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   12069篇
  免费   1805篇
  国内免费   1266篇
化学   6997篇
晶体学   106篇
力学   481篇
综合类   110篇
数学   1188篇
物理学   3015篇
无线电   3243篇
  2024年   52篇
  2023年   283篇
  2022年   347篇
  2021年   411篇
  2020年   454篇
  2019年   436篇
  2018年   348篇
  2017年   368篇
  2016年   558篇
  2015年   545篇
  2014年   731篇
  2013年   856篇
  2012年   1015篇
  2011年   1017篇
  2010年   754篇
  2009年   676篇
  2008年   794篇
  2007年   676篇
  2006年   597篇
  2005年   523篇
  2004年   479篇
  2003年   445篇
  2002年   457篇
  2001年   389篇
  2000年   238篇
  1999年   273篇
  1998年   173篇
  1997年   146篇
  1996年   164篇
  1995年   137篇
  1994年   126篇
  1993年   97篇
  1992年   92篇
  1991年   88篇
  1990年   51篇
  1989年   54篇
  1988年   38篇
  1987年   34篇
  1986年   35篇
  1985年   34篇
  1984年   11篇
  1983年   6篇
  1982年   9篇
  1981年   9篇
  1980年   7篇
  1963年   7篇
  1959年   12篇
  1958年   11篇
  1957年   15篇
  1956年   10篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
This paper is contributed to the combinatorial properties of the periodic kneading words of antisymmetric cubic maps defined on a interval. The least words of given lengths, the adjacency relations on the words of given lengths and the parity-alternative property in some sets of such words are established.  相似文献   
993.
模糊控制技术中一种特殊的高维插值法   总被引:1,自引:0,他引:1  
本文介绍一种在模糊控制技术中高维插值方法的应用。这种方法可以由有限数据或经验规则,通过高维插获完整的全值表,从而克服了过去去多因素,多目标,非线性的复杂被控系统由于经验规则远远不足,无法得到完整的控制规则表听困难。为进一步设计模糊模糊控制器提供了可行的基础。  相似文献   
994.
Room temperature ionic liquids with low melting point (<100℃) salts represent a new class of non-molecular, ionic solvents. Especially those based on the 1-N-alkyl-3- methylimidazolium cations, have shown great promise as an attractive alternative to conventional solvents for catalytic reactions1. On the other hand, FeCl3·6H2O was considered to be an environmentally benign Lewis acid and has been used successfully in several kinds of organic reactions2. Recently we have focused our interes…  相似文献   
995.
We report on the improvement of critical dimension (CD) linearity on a photomask by applying the concept of process proximity correction to a laser lithographic process used for the fabrication of photomasks. Rule‐based laser process proximity correction (LPC) was performed using an automated optical proximity correction tool and we obtained dramatic improvement of CD linearity on a photomask. A study on model‐based LPC was executed using a two‐Gaussian kernel function and we extracted model parameters for the laser lithographic process by fitting the model‐predicted CD linearity data with measured ones. Model‐predicted bias values of isolated space (I/S), arrayed contact (A/C) and isolated contact (I/C) were in good agreement with those obtained by the nonlinear curve‐fitting method used for the rule‐based LPC.  相似文献   
996.
Deposition of HfO2 films on n-type 4H-SiC substrates by sol-gel spin-on coating technique has been performed and the physical and electrical characteristics of this film as a function of annealing temperature (550, 750, and 850 °C for 30 min) have been reported. The physical properties of the film have been characterized using a Filmetrics and X-ray diffractometer, while conduction atomic force microscope and semiconductor parameter analyzer were used for electrical characterization. Phase transformation has been revealed in the oxide as the annealing temperature changed. Refractive index, relative density, dielectric constant of the film, and oxide-semiconductor interface trap density have been extracted and related to the leakage current through the oxide. It has been recorded that, oxide annealed at 700 °C has demonstrated the lowest leakage current and the best oxide reliability. The reasons of these observations have been explained.  相似文献   
997.
998.
A simplicial complex K\mathsf{K} is called d -representable if it is the nerve of a collection of convex sets in ℝ d ; K\mathsf{K} is d -collapsible if it can be reduced to an empty complex by repeatedly removing a face of dimension at most d−1 that is contained in a unique maximal face; and K\mathsf{K} is d -Leray if every induced subcomplex of K\mathsf{K} has vanishing homology of dimension d and larger. It is known that d-representable implies d-collapsible implies d-Leray, and no two of these notions coincide for d≥2. The famous Helly theorem and other important results in discrete geometry can be regarded as results about d-representable complexes, and in many of these results, “d-representable” in the assumption can be replaced by “d-collapsible” or even “d-Leray.”  相似文献   
999.
1000.
Monadic MV-algebras are an algebraic model of the predicate calculus of the Łukasiewicz infinite valued logic in which only a single individual variable occurs. GMV-algebras are a non-commutative generalization of MV-algebras and are an algebraic counterpart of the non-commutative Łukasiewicz infinite valued logic. We introduce monadic GMV-algebras and describe their connections to certain couples of GMV-algebras and to left adjoint mappings of canonical embeddings of GMV-algebras. Furthermore, functional MGMV-algebras are studied and polyadic GMV-algebras are introduced and discussed. The first author was supported by the Council of Czech Government, MSM 6198959214.  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