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   176199篇
  免费   17430篇
  国内免费   12152篇
化学   94258篇
晶体学   1850篇
力学   12062篇
综合类   666篇
数学   43451篇
物理学   53494篇
  2024年   351篇
  2023年   2067篇
  2022年   3667篇
  2021年   3820篇
  2020年   4175篇
  2019年   3959篇
  2018年   13232篇
  2017年   12764篇
  2016年   10562篇
  2015年   5702篇
  2014年   6323篇
  2013年   8063篇
  2012年   12832篇
  2011年   19325篇
  2010年   11920篇
  2009年   11961篇
  2008年   12900篇
  2007年   14253篇
  2006年   5771篇
  2005年   5887篇
  2004年   5095篇
  2003年   4818篇
  2002年   3624篇
  2001年   2457篇
  2000年   2227篇
  1999年   2199篇
  1998年   1922篇
  1997年   1700篇
  1996年   1748篇
  1995年   1479篇
  1994年   1313篇
  1993年   1095篇
  1992年   953篇
  1991年   838篇
  1990年   701篇
  1989年   560篇
  1988年   436篇
  1987年   395篇
  1986年   392篇
  1985年   308篇
  1984年   230篇
  1983年   189篇
  1982年   166篇
  1981年   116篇
  1980年   105篇
  1979年   70篇
  1978年   56篇
  1973年   42篇
  1914年   45篇
  1909年   41篇
排序方式: 共有10000条查询结果,搜索用时 8 毫秒
991.
Hardy spaces of analytic functions are studied both on strongly pseudoconvex domains in ℂn and on domains of finite type in ℂ2. Duality theorems, atomic decompositions, and factorization of functions are treated. Mapping properties of certain Hankel operators are studied.  相似文献   
992.
Theformationofanewtypeofself_assembledmultilayerfilms,moleculardeposition(MD)films[1,2],isafastdevelopingareaofthinfilmresearch.Thisnewmethodoffilmpreparationisbasedonionicattractionbetweenoppositechargedchromophores.IncomparisonwiththeclassicLangmuir_Blo…  相似文献   
993.
994.
995.
This paper is concerned with a combined production-transportation scheduling problem. The problem comprises a simple, two-machine, automated manufacturing cell, which either stands alone or is a subunit of a complete flexible manufacturing system. The cell consists of two machines in series with a dedicated part-handling device such as a crane or robotic arm for transferring parts from the first machine to the second. The loading of a new piece on the first machine and the ejection of a finished piece from the second machine are performed by dedicated automated mechanisms. The introduction of parts into the system is done n at a time, whereby the parts are reshuffled into a sequence that minimizes completion time. All processing and transfer times are considered deterministic—a reasonable assumption for a cell comprising a robotic transfer device and two CNC machining units. What complicates the problem is the assumption of a non-negligible time for the transfer device to return (empty) from the second machine to the first. The operation is a generalization of a two-machine flowshop problem, and is formulated as a specially structured, asymmetric travelling salesman problem. An approximate polynomial time 0(n log n) algorithm is proffered. The procedure incorporates a lower bound using the Gilmore–Gomory algorithm for the no-wait, two-machine flowshop problem.  相似文献   
996.
Let l be the critical exponent associated with the probability thatl independentN-step ordinary random walks, starting at nearby points, are mutually avoiding. Using Monte Carlo methods combined with a maximum-likelihood data analysis, we find that in two dimensions 2=0.6240±0.0005±0.0011 and 3=1.4575±0.0030±0.0052, where the first error bar represents systematic error due to corrections to scaling (subjective 95% confidence limits) and the second error bar represents statistical error (classical 95% confidence limits). These results are in good agreement with the conformal-invariance predictions 2=5/8 and 3=35/24.  相似文献   
997.
998.
999.
The picosecond degenerate four-wave mixing reflectivity of semi-insulating gallium arsenide at 1.06 m is calculated in this paper. The dependence of the reflectivity on the pump and signal fluences is measured. Reflectivities of more than one are possible. The Fourier components of the excited-carrier densities are calculated as a function of the pump fluence. The wavefront-correction property of this reflectivity is demonstrated with a lens group in the signal beam.  相似文献   
1000.
We first demonstrate that mixed strategies are relevant in decision analysis for a maximin decision-maker quite apart from any game-theory considerations. This rectifies the apparent misconception that results from MS/OR textbooks which discuss mixed strategies only in the game-theory setting. Next we show an example of an implementable mixed strategy, by which we mean a mixed decision strategy which does not require randomization for its implementation. This application is to portfolio construction.  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