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   12745篇
  免费   385篇
  国内免费   15篇
化学   7069篇
晶体学   247篇
力学   304篇
综合类   21篇
数学   2384篇
物理学   3120篇
  2022年   66篇
  2021年   84篇
  2020年   165篇
  2019年   239篇
  2018年   285篇
  2017年   298篇
  2016年   540篇
  2015年   407篇
  2014年   506篇
  2013年   1119篇
  2012年   660篇
  2011年   743篇
  2010年   565篇
  2009年   484篇
  2008年   689篇
  2007年   609篇
  2006年   521篇
  2005年   435篇
  2004年   389篇
  2003年   362篇
  2002年   307篇
  2001年   274篇
  2000年   226篇
  1999年   149篇
  1998年   154篇
  1997年   107篇
  1996年   117篇
  1995年   140篇
  1994年   84篇
  1993年   62篇
  1992年   91篇
  1991年   91篇
  1990年   90篇
  1989年   97篇
  1988年   109篇
  1987年   88篇
  1986年   93篇
  1985年   176篇
  1984年   183篇
  1983年   118篇
  1982年   110篇
  1981年   119篇
  1980年   128篇
  1979年   95篇
  1978年   91篇
  1977年   84篇
  1976年   94篇
  1975年   77篇
  1974年   68篇
  1973年   59篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
Thermal behaviour and biochemical activity of potassium-silicate-phosphate glasses modified by addition of Ca, Mg, acting as ecological fertilisers of controlled release rate of the nutrients for plants were studied. It has been found that the biochemical activity of silicate-phosphate glasses depends on the nature and the number of components forming the glassy framework and is related to the thermal stability of glass demonstrated by the formation of new compounds during the process of crystallisation. It is proved that these seemingly different properties are determined by the same parameters which are the strengths bonds of glass network-formers and modifiers as well as their chemical affinity. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   
22.
The eigenvalues and eigenfunctions of an elementary 3-fermion 2-body operator 3P2gI1A31≤ij≤3P2g(i, j)A3 acting on a 3-particle antisymmetric finite-dimensional Hilbert space have been found. Here Pg2 denotes the projection operator onto a 2-particle antisymmetric function g2, while A3 denotes the 3-particle antisymmetrizing operator.  相似文献   
23.
A convenient and higher yielding synthetic route to N‐alkyl‐bis(thiophene)phenothiazine derivatives is reported and their aggregation, electrochemical properties and polymerization are characterized. The key step in the synthesis of this group of compounds has been the Stille type coupling reaction between the N‐alkyldibromophenothiazine and tin derivatives of thiophene as the best way for preparation of conjugated N‐alkylphenothiazine derivatives. For this group of compounds we also present an electrochemical polymerization effect and widely adopted approach to prepare structurally ordered thin, electroconducting films by Langmuir–Blodgett technique.  相似文献   
24.
We introduce here some Itô calculus for non-continuous Dirichlet processes. Such calculus extends what was known for continuous Dirichlet processes or for semimartingales. In particular we prove that non-continuous Dirichlet processes are stable under C 1 transformation.  相似文献   
25.
JPC – Journal of Planar Chromatography – Modern TLC - This paper reports the efficiency of the C30 phase for HPLC and TLC separation of a mixture of tocopherol homologs and...  相似文献   
26.
A least‐squares meshfree method based on the first‐order velocity–pressure–vorticity formulation for two‐dimensional incompressible Navier–Stokes problem is presented. The convective term is linearized by successive substitution or Newton's method. The discretization of all governing equations is implemented by the least‐squares method. Equal‐order moving least‐squares approximation is employed with Gauss quadrature in the background cells. The boundary conditions are enforced by the penalty method. The matrix‐free element‐by‐element Jacobi preconditioned conjugate method is applied to solve the discretized linear systems. Cavity flow for steady Navier–Stokes problem and the flow over a square obstacle for time‐dependent Navier–Stokes problem are investigated for the presented least‐squares meshfree method. The effects of inaccurate integration on the accuracy of the solution are investigated. Copyright © 2004 John Wiley & Sons, Ltd.  相似文献   
27.
A phenomenological model for describing the production of Centauro events in relativistic heavy-ion collisions is discussed. The model provides quantitative predictions for kinematical variables, for the baryon number, and for the masses of a Centauro fireball and of its decay products. A Centauro fireball decays predominantly into nucleons, strange hyperons, and possibly strangelets. Centauro events in Pb + Pb collisions at the LHC energy are simulated for the CASTOR detector. The signatures of these events are discussed in detail.  相似文献   
28.
JPC – Journal of Planar Chromatography – Modern TLC - Flavonoid glycosides are much more polar than their aglycones and the two groups of compounds are difficult to separate by planar...  相似文献   
29.
大气气溶胶粒子光吸收系数的测量   总被引:6,自引:2,他引:4       下载免费PDF全文
 采用核孔过滤膜累积气溶胶粒子的方法设计了气溶胶粒子光吸收系数的测量系统。该系统由双光路组成,可以减小光路损耗和电路噪声带来的各种测量误差。同时,具有体积小、光路易于调节、可进行实时测量、定标容易等特点。用200和400nm孔径的过滤膜,分别测量了实验室内大气气溶胶粒子对不同波长激光的吸收系数。随着累积时间的增加,系统的测量精度也不断的提高,在累积时间为900s时,系统测量误差为9.849×10-6/m。  相似文献   
30.
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