Mathematics

LinuxWindows Maxima
 Maxima is a system for the manipulation of symbolic and numerical expressions, including differentiation, integration, Taylor series, Laplace transforms, ordinary differential equations, systems of linear equations, polynomials, and sets, lists, vectors, matrices, and tensors. Maxima yields high precision numeric results by using exact fractions, arbitrary precision integers, and arbitrarily precision floating point numbers. Maxima can plot functions and data in two and three dimensions.
LinuxWindows SAGE (Software for Algebra and Geometry Expermentation)
 SAGE is free open source math software that supports research and teaching in algebra, geometry, number theory, cryptography, numerical computation, and related areas. Includes Maxima, Singular, PARI, Matplotlib and other opensource math packages. You can use internet interface (sage-notebok) to access all the features (needs Firefox).

Physics – Chemistry

Linux4Chemistry
 
LinuxWindows CDK (Chemistry Developmnet Kit)
 The Chemistry Development Kit (CDK) is a Java library for structural chemo- and bioinformatics. c

Geography

Windows NASA World Wind
 World Wind, an open source 3D interactive world viewer, was created by NASA's Learning Technologies project, and released in mid-2004. It is now developed by NASA staff and open source community developers.
World Wind allows any user to zoom from outer space into any place on Earth. World Wind uses satellite imagery and elevation data to allow users to experience Earth terrain in visually rich 3D, just as if they were really there. Virtually visit anyplace in the world. Look across the Andes, into the Grand Canyon, over the Alps or along the African Sahara.

Scientific calculations and data analysis

LinuxWindows SciLab
 Scilab is a scientific software package for numerical computations providing a powerful open computing environment for engineering and scientific applications. A number of toolboxes are available with the system: 2-D and 3-D graphics, animation Linear algebra, sparse matrices Polynomials and rational functions Interpolation, approximation Simulation: ODE solver and DAE solver Scicos: a hybrid dynamic systems modeler and simulator Classic and robust control, LMI optimization Differentiable and non-differentiable optimization Signal processing Metanet: graphs and networks Parallel Scilab Statistics Interface with Computer Algebra: Maple package for Scilab code generation Interface with Fortran, Tcl/Tk, C, C++, Java, LabVIEW And a large number of contributions for various domains.
LinuxWindows R
 R is a language and environment for statistical computing and graphics. Language is similar to proprietary S-plus statistical package. R provides a wide variety of statistical (linear and nonlinear modelling, classical statistical tests, time-series analysis, classification, clustering, ...) and graphical techniques, and is highly extensible. The S language is often the vehicle of choice for research in statistical methodology, and R provides an Open Source route to participation in that activity.
Linuxrkward
 RKWard is meant to become an easy to use, transparent frontend to the R-language, a very powerful, yet hard-to-get-into scripting-language with a strong focus on statistic functions. It will not only provide a convenient user-interface, however, but also take care of seamless integration with an office-suite. Practical statistics is not just about calculating, after all, but also about documenting and ultimately publishing the results.
Windows SciViews
 SciViews-R is a suite of companion applications that provides a Graphical User Interface (GUI) on top of the command-line driven environment of R. To get a rapid feeling of the look-and-feel of SciViews-R, take a look at these screenshots and this presentation.
Windows Tanagra
 TANAGRA is a free DATA MINING software for academic and research purposes. It proposes several data mining methods from exploratory data analysis, statistical learning, machine learning and databases area.
LinuxWindows gretl
 
LinuxWindows ParaView
 ParaView designed with the need to visualize large data sets in mind.
The goals of the ParaView project include the following: Develop an open-source, multi-platform visualization application. Support distributed computation models to process large data sets. Create an open, flexible, and intuitive user interface. Develop an extensible architecture based on open standards.
LinuxWindows Išversta į lietuvių kalbąOpenOffice Calc
 
LinuxWindows praat
 doing phonetics by computer

Biochemija

LinuxWindows PyMol
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CellProfiler
 cell image analysis software is designed for biologists without training in computer vision or programming to quantitatively measure phenotypes from thousands of images automatically

Kompiuterinė lingvistika

LinuxWindows NLTK Lite (Natural Language Toolkit)
 NLTK is ideally suited to students who are learnina suite of program modules, data sets and tutorials supporting research and teaching in computational linguistics and natural language processing. NLTK is ideally suited to students who are learning NLP (natural language processing) or conducting research in NLP or closely related areas, including empirical linguistics, cognitive science, artificial intelligence, information retrieval, and machine learning. NLTK has been used successfully as a teaching tool, as an individual study tool, and as a platform for prototyping and building research systems.
LinuxWindows WordNet
 WordNet® is a large lexical database of English. Nouns, verbs, adjectives and adverbs are grouped into sets of cognitive synonyms (synsets), each expressing a distinct concept. Synsets are interlinked by means of conceptual-semantic and lexical relations. The resulting network of meaningfully related words and concepts can be navigated with the browser.

Text editing

LinuxWindows Lyx
 LyX is a document processor that encourages an approach to writing based on the structure of your documents, not their appearance.