全文获取类型
收费全文 | 2814篇 |
免费 | 200篇 |
国内免费 | 164篇 |
专业分类
电工技术 | 176篇 |
综合类 | 196篇 |
化学工业 | 227篇 |
金属工艺 | 82篇 |
机械仪表 | 125篇 |
建筑科学 | 39篇 |
矿业工程 | 23篇 |
能源动力 | 31篇 |
轻工业 | 393篇 |
水利工程 | 15篇 |
石油天然气 | 105篇 |
武器工业 | 21篇 |
无线电 | 611篇 |
一般工业技术 | 656篇 |
冶金工业 | 38篇 |
原子能技术 | 69篇 |
自动化技术 | 371篇 |
出版年
2024年 | 7篇 |
2023年 | 32篇 |
2022年 | 61篇 |
2021年 | 59篇 |
2020年 | 65篇 |
2019年 | 65篇 |
2018年 | 55篇 |
2017年 | 70篇 |
2016年 | 74篇 |
2015年 | 57篇 |
2014年 | 146篇 |
2013年 | 136篇 |
2012年 | 189篇 |
2011年 | 190篇 |
2010年 | 149篇 |
2009年 | 165篇 |
2008年 | 138篇 |
2007年 | 218篇 |
2006年 | 229篇 |
2005年 | 184篇 |
2004年 | 191篇 |
2003年 | 103篇 |
2002年 | 120篇 |
2001年 | 91篇 |
2000年 | 70篇 |
1999年 | 71篇 |
1998年 | 51篇 |
1997年 | 32篇 |
1996年 | 33篇 |
1995年 | 19篇 |
1994年 | 18篇 |
1993年 | 16篇 |
1992年 | 13篇 |
1991年 | 20篇 |
1990年 | 11篇 |
1989年 | 6篇 |
1988年 | 7篇 |
1987年 | 5篇 |
1986年 | 2篇 |
1985年 | 2篇 |
1984年 | 2篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1977年 | 1篇 |
1974年 | 1篇 |
1961年 | 1篇 |
1959年 | 1篇 |
排序方式: 共有3178条查询结果,搜索用时 78 毫秒
61.
不等式机器证明问题是智能系统领域的难点和热点问题.借助不等式证明软件BOTTEMA,对若干常用的基本不等式成功地实现了机器证明,包括算术、几何与调和平均不等式、排序不等式、Chebyshev不等式、Bernoulli不等式、三角形不等式及Jensen不等式等.所论不等式含有的变元个数是一个不确定的变量,属于Tarski模型外的不等式类型.机器证明得出的结论有时可能是已知结果的推广,其方法本身对同类不等式有示范性,更多的例子表明了该算法和软件的有效性. 相似文献
62.
将一类积分不等式转化为Tarski模型外的齐次对称多项式不等式,该类齐次对称多项式的次数是给定的,变元个数可以是任意多个,并且多项式的系数是与变元个数相关的变系数.这些特点与杨路等人最近提出的几个公开问题密切相关,是比较有代表性的一类齐次对称多项式.然后利用Timofte关于对称多项式不等式判定的降维方法,结合不等式证明软件BOTTEMA及差分代换方法,给出对应的一类Tarski模型外的齐次对称多项式不等式的机器判定算法,从而实现原积分不等式的机器判定.当给定的积分不等式及齐次对称多项式不等式不成立时,可给出具体不成立的数值反例.应用例子表明问题的广泛性及算法的有效性. 相似文献
63.
严慧 《数码设计:surface》2010,(6):61-62
包装是生活中不可或缺的一部分,色彩是包装设计中重要元素,人们通过长期的生活体验,有意无意之中形成了根据色彩来判断和感受商品包装的方式,包装色彩不仅增强消费者的审美愉悦,吸引消费者的注意力,更能激发消费者的购买欲望,它的运用是否合理直接影响到该包装设计是否成功。 相似文献
64.
65.
To what extent can software ‘travel’ to organizations and countries for which it was not designed for, and how important are local contexts for a successful design and implementation of generic software? Information systems researchers have differing views on this, some emphasizing the strengths of the generic and others the importance of contextual aspects. Contributing to this debate, Pollock and Williams have coined the term generification in order to describe how large vendors succeed in globalizing software packages through management by community, content and social authority. In this paper, we explore an approach that we call open generification, which extends Pollock and Williams' work in the sense that we acknowledge the need for and the feasibility of generic software, but propose an alternative model for the governance of it. Open generification is not about managing the community of users attached to a software package by homogenization or segmentation but aims at addressing the diverse needs of the community the software is expected to serve. Our empirical basis is a longitudinal study of the development of an open‐source health information system software (District Health Information software version 2), which is being used in more than 47 countries. Its success is attributed to a continuous interplay between generic and specific software and continuous cycles of embedding (implementing the global in the local context) and disembedding (taking local innovations into the global). We identify and discuss the contingent mechanisms of this interplay. 相似文献
66.
Sam J. Cipolla 《Computer Physics Communications》2011,(11):2439-2440
In this new version of ISICS, called ISICS2011, a few omissions and incorrect entries in the built-in file of electron binding energies have been corrected; operational situations leading to un-physical behavior have been identified and flagged.
New version program summary
Program title: ISICS2011Catalogue identifier: ADDS_v5_0Program summary URL:http://cpc.cs.qub.ac.uk/summaries/ADDS_v5_0.htmlProgram obtainable from: CPC Program Library, Queen?s University, Belfast, N. IrelandLicensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.htmlNo. of lines in distributed program, including test data, etc.: 6011No. of bytes in distributed program, including test data, etc.: 130 587Distribution format: tar.gzProgramming language: CComputer: 80486 or higher-level PCsOperating system: WINDOWS XP and all earlier operating systemsClassification: 16.7Catalogue identifier of previous version: ADDS_v4_0Journal reference of previous version: Comput. Phys. Commun. 180 (2009) 1716.Does the new version supersede the previous version?: YesNature of problem: Ionization and X-ray production cross section calculations for ion–atom collisions.Solution method: Numerical integration of form factor using a logarithmic transform and Gaussian quadrature, plus exact integration limits.Reasons for new version: General need for higher precision in output format for projectile energies; some built-in binding energies needed correcting; some anomalous results occur due to faulty read-in data or calculated parameters becoming un-physical; erroneous calculations could result for the L and M shells when restricted K-shell options are inadvertently chosen; to achieve general compatibility with ISICSoo, a companion C++ version that is portable to Linux and MacOS platforms, has been submitted for publication in the CPC Program Library approximately at the same time as this present new standalone version of ISICS [1].Summary of revisions: The format field for projectile energies in the output has been expanded from two to four decimal places in order to distinguish between closely spaced energy values. There were a few entries in the executable binding energy file that needed correcting; K shell of Eu, M shells of Zn, M1 shell of Kr. The corrected values were also entered in the ENERGY.DAT file. In addition, an alternate data file of binding energies is included, called ENERGY_GW.DAT, which is more up-to-date [2]. Likewise, an alternate atomic parameters data file is now included, called FLOURE_JC.DAT, which is more up-to-date [3] fluorescence yields for the K and L shells and Coster–Kronig parameters for the L shell. Both data files can be read in using the -f usage option. To do this, the original energy file should be renamed and saved (e.g., ENERGY_BB.DAT) and the new file (ENERGY_GW.DAT ) should be duplicated as ENERGY.DAT to be read in using the -f option. Similarly for reading in an alternate FLOURE.DAT file. As with previous versions, the user can also simply input different values of any input quantity by invoking the “specify your own parameters” option from the main menu. You can also use this option to simply check the values of the built-in values of the parameters. If it still happens that a zero binding energy for a particular sub-shell is read in, the program will not completely abort, but will calculate results for the other sub-shells while setting the affected sub-shell output to zero. In calculating the Coulomb deflection factor, if the quantity inside the radical sign of the parameter zs becomes zero or negative, to prevent the program from aborting, the PWBA cross sections are still calculated while the ECPSSR cross sections are set to zero. This situation can happen for very low energy collisions, such as were noticed for helium ions on copper at energies of E?11.2 keV. It was observed during the engineering of ISICSoo [1] that erroneous calculations could result for the L- and M-shell cases when restricted K-shell R or HSR scaling options were inappropriately chosen. The program has now been fixed so that these inappropriate options are ignored for the L and M shells. In the previous versions, the usage for inputting a batch data file was incorrectly stated in the Users Manual as -Bxxx; the correct designation is -Fxxx, or alternatively, -Ixxx, as indicated on the usage screen in running the program.A revised Users Manual is also available.Restrictions: The consumed CPU time increases with the atomic shell (K, L, M), but execution is still very fast.Running time: This depends on which shell and the number of different energies to be used in the calculation. The running time is not significantly changed from the previous version.References:[1]
M. Batic, M.G. Pia, S. Cipolla, Comput. Phys. Commun. (2011), submitted for publication. [2]
http://www.jlab.org/~gwyn/ebindene.html. [3]
J. Campbell, At. Data Nucl. Data Tables 85 (2003) 291.
67.
随着软件复用技术的发展,Internet上出现了大量可以被利用的软件资源,如Web Services, JAR包等。但是,这些软件资源常常缺乏必要的描述信息和使用说明。为此,提出了一种基于Internet的JAR包使用信息收集方法,以帮助用户检索并整理Internet上已经存在的JAR包描述信息和用户使用评论,辅助软件复用的成功进行。基于该方法,设计并实现了北京大学软件资源库JAR包使用信息收集子系统。该系统目前已经为6000余个JAR包资源收集、整理了相关的描述和评论信息。 相似文献
68.
基于MATLAB的小波包信号消噪处理 总被引:2,自引:0,他引:2
信噪分离是小波包应用于信号分析的一个重要方面。本文在基于MATLAB的基础上,采用小波包对含高斯白噪声信号进行分解,通过不同的量化阈值对小波包系数进行处理、重构得出小波包消噪后的信号。计算机仿真结果表明,用不同量化阈值的小波包可对含高斯白声信号进行消噪重构。 相似文献
69.
70.
探讨了在知识经济全面发展的背景下,插画艺术和包装设计结合的日益普遍的原因,并结合时代、社会、市场的发展要求提出新时期包装设计所面临的挑战。最后从市场、情感、民族和社会审美等角度出发,论述了应用当今插画艺术的包装设计所要遵循的原则。在满足商业需求的同时,探寻一条本土化的包装设计之路。 相似文献