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   10750篇
  免费   653篇
  国内免费   426篇
化学   6346篇
晶体学   71篇
力学   415篇
综合类   45篇
数学   2066篇
物理学   2886篇
  2023年   91篇
  2022年   140篇
  2021年   167篇
  2020年   215篇
  2019年   181篇
  2018年   299篇
  2017年   288篇
  2016年   418篇
  2015年   316篇
  2014年   441篇
  2013年   830篇
  2012年   580篇
  2011年   765篇
  2010年   462篇
  2009年   425篇
  2008年   591篇
  2007年   570篇
  2006年   507篇
  2005年   362篇
  2004年   312篇
  2003年   235篇
  2002年   247篇
  2001年   186篇
  2000年   161篇
  1999年   150篇
  1998年   132篇
  1997年   115篇
  1996年   116篇
  1995年   109篇
  1994年   98篇
  1993年   103篇
  1992年   118篇
  1991年   94篇
  1990年   103篇
  1989年   98篇
  1988年   91篇
  1987年   94篇
  1986年   81篇
  1985年   95篇
  1984年   87篇
  1983年   94篇
  1982年   89篇
  1981年   62篇
  1980年   84篇
  1979年   72篇
  1978年   96篇
  1977年   74篇
  1976年   84篇
  1975年   69篇
  1974年   73篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
A green and sustainable strategy synthesizes clinical medicine warfarin anticoagulant by using lipase‐supported metal–organic framework (MOF) bioreactors (see scheme). These findings may be beneficial for future studies in the industrial production of chemical, pharmaceutical, and agrochemical precursors.  相似文献   
3.
4.
5.
6.
In agreement with the Kohn theorem the relative motion (rel) of three electrons in a two-dimensional parabolic trap separates from the centre-of-mass (CM) motion. By introducing new coordinates the Hamiltonian for relative motion in the approximation of non-interacting electrons can be taken to the normal form. The eigenstates of the normalized Hamiltonian are products of the Fock-Darwin states for normal modes. The energy levels for relative motion are obtained by diagonalizing the exact Hamiltonian in the eigenbasis for the non-interacting case. In this basis the interaction matrix elements can be obtained in the analytical form. Since the rank of the Hamiltonian matrix is significantly reduced, the calculations are faster and more accurate than those for the full (CM + rel) motion. This advantage is especially important for the calculations of excited states and the analysis of energy spectra.  相似文献   
7.
An experimental method for determining the real-time depth of laser-drilled holes is presented. The proposed method involves detecting the laser-induced optoacoustic waves generated during the interaction of the laser beam with the material. Our optodynamic study involved measuring the propagation times of these waves as they traveled through the material and analyzing their temporal behavior during the drilling process. The experimental observations revealed an exponential relationship between the propagation time of the longitudinal stress wave and the number of consecutive laser pulses. Received: 25 October 2001 / Accepted: 27 October 2001 / Published online: 20 December 2001  相似文献   
8.
9.
In mononuclear HgI2[(C5H4N)3N], mercury is tetrahedrally coordinated by two nitrogen atoms of a tris(2‐pyridyl)amine ligand and two iodides. The coordination moieties are connected by weak intermolecular Hg(II)···I interactions to give a one‐dimensional structure. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   
10.
Test particle motion and acceleration has been explored in strong radio frequency (RF) fields, for which quasilinear ponderomotive force approximation is not valid. By nonlinear acceleration in spatially varying wave amplitude of RF travelling wave, electrons may be accelerated to time averaged velocities significantly larger than the RF wave phase velocity, and than the boundary plasma thermal velocity, in RF fields of several Volts per centimeter at wave frequency of 7 MHz. It is also demonstrated that even weak spatial gradients, much weaker than those expected in experiments, of the RF wave field amplitude, have significant consequences for the particle motion. Estimates are presented of the total energy transferred from the near antenna RF field to the plasma due to the nonlinear electron acceleration effects.  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