首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   86035篇
  免费   633篇
  国内免费   131篇
化学   42028篇
晶体学   1264篇
力学   3300篇
综合类   1篇
数学   7944篇
物理学   24958篇
无线电   7304篇
  2022年   685篇
  2021年   964篇
  2020年   1100篇
  2019年   1235篇
  2018年   1726篇
  2017年   1815篇
  2016年   2330篇
  2015年   1097篇
  2014年   1869篇
  2013年   3524篇
  2012年   3101篇
  2011年   3507篇
  2010年   2852篇
  2009年   2942篇
  2008年   3353篇
  2007年   3317篇
  2006年   3135篇
  2005年   2812篇
  2004年   2588篇
  2003年   2435篇
  2002年   2424篇
  2001年   2509篇
  2000年   1905篇
  1999年   1507篇
  1998年   1376篇
  1997年   1263篇
  1996年   1079篇
  1995年   998篇
  1994年   989篇
  1993年   953篇
  1992年   1007篇
  1991年   1088篇
  1990年   1036篇
  1989年   1024篇
  1988年   923篇
  1987年   840篇
  1986年   810篇
  1985年   954篇
  1984年   1024篇
  1983年   872篇
  1982年   892篇
  1981年   787篇
  1980年   738篇
  1979年   806篇
  1978年   928篇
  1977年   959篇
  1976年   839篇
  1975年   801篇
  1974年   826篇
  1973年   800篇
排序方式: 共有10000条查询结果,搜索用时 7 毫秒
71.
We obtain estimates for errors of interpolation on a nonuniform grid for a parabolic nonperiodic spline of defect 1.  相似文献   
72.
Book reviews     
Ohne Zusammenfassung
Book reviews
  相似文献   
73.
74.
The third-law method is used to assess the authenticity of available equilibrium constants for the thermal dissociation of N2O5 ? NO2 + NO3. © 1994 John Wiley & Sons, Inc.  相似文献   
75.
In this article we propose efficient scan path and BIST schemes for RAMs. Tools for automatic generation of these schemes have been implemented. They reduce the design effort and thus allow the designer to select the more appropriate scheme with respect to various constraints.  相似文献   
76.
Signature analyzers are very efficient output response compactors for BIST design. The only limitation of signature analysis is the fault coverage reduction (aliasing) due to the information loss inherent to any data compaction. In this article, in order to increase the effectiveness of ROM BIST, we take advantage from the simplicity of the error patterns generated by ROMs and we show that aliasing free signature analysis can be achieved in ROM BIST.This work was performed when the author was on leave from Minsk Radio Engineering Institute, Computer Department, Belorus.  相似文献   
77.
We analyze a very general class of algorithms for constructingm-bit invertible S-boxes called bit-by-bit methods. The method builds an S-box one entry at a time, and has been proposed by Adams and Tavares [2] and Forre [11] to construct S-boxes that satisfy certain cryptographic properties such as nonlinearity and the strict avalanche criterion. We prove, both theoretically and empirically, that the bit-by-bit method is infeasible form>6. The author is currently employed by the Distributed System Technology Center (DSTC), Brisbane, Australia. Correspondence should be sent to ISRC, QUT Gardens Point, 2 George Street, GPO Box 2434, Brisbane, Queensland 4001, Australia.  相似文献   
78.
On the basis of a complex null-polarimetric method, the natural birefringence and the rotation of the optical indicatrix in crystals of deuterated triglycinesulfate are measured in the temperature range of 300–340 K. The temperature-dependent behavior of the optical parameters is shown to be close to that observed previously in triglycinesulfate crystals. Changes in them upon the ferroelectric phase transition can be accounted for by the spontaneous quadratic electro-optic effect, with the values of the electro-optic coefficients being larger by a factor of 1.4 than in triglycinesulfate crystals.  相似文献   
79.
80.
The measured equation of invariance (MEI) has been previously introduced to efficiently and accurately handle the boundary truncation for finite methods. The present authors give a theoretical analysis that provides several important insights into the capabilities of the MEI. From the numerical study, they can explain why the MEI works better than one would expect. Both the theoretical and the numerical analyses demonstrate that the accuracy of the solution is dependent on the electrical size of the geometry as well as the distance between the mesh boundary and the geometry. From the analysis, the authors propose a new set of metrons that is less sensitive to the excitation than the previously proposed sinusoidal metrons  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号