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   1435篇
  免费   55篇
化学   1102篇
晶体学   41篇
力学   36篇
数学   97篇
物理学   214篇
  2024年   4篇
  2023年   7篇
  2022年   16篇
  2021年   30篇
  2020年   36篇
  2019年   30篇
  2018年   35篇
  2017年   36篇
  2016年   41篇
  2015年   44篇
  2014年   63篇
  2013年   97篇
  2012年   104篇
  2011年   105篇
  2010年   55篇
  2009年   71篇
  2008年   85篇
  2007年   66篇
  2006年   110篇
  2005年   69篇
  2004年   62篇
  2003年   44篇
  2002年   32篇
  2001年   11篇
  2000年   18篇
  1999年   9篇
  1998年   8篇
  1997年   14篇
  1996年   14篇
  1995年   13篇
  1994年   16篇
  1993年   17篇
  1992年   15篇
  1991年   15篇
  1990年   13篇
  1989年   10篇
  1988年   8篇
  1987年   4篇
  1986年   6篇
  1985年   8篇
  1984年   10篇
  1983年   4篇
  1982年   6篇
  1981年   6篇
  1980年   3篇
  1979年   3篇
  1977年   2篇
  1976年   3篇
  1972年   3篇
  1968年   3篇
排序方式: 共有1490条查询结果,搜索用时 359 毫秒
1.
Russian Journal of General Chemistry - In the current study, some new quinoxaline linked 1,3,4-oxadiazole sulfonamide hybrids have been designed, synthesized and characterized by IR, 1H and 13C...  相似文献   
2.
3.
4.
M. D. Srinivas 《Pramana》2003,60(6):1137-1152
We derive an optimal bound on the sum of entropic uncertainties of two or more observables when they are sequentially measured on the same ensemble of systems. This optimal bound is shown to be greater than or equal to the bounds derived in the literature on the sum of entropie uncertainties of two observables which are measured on distinct but identically prepared ensembles of systems. In the case of a two-dimensional Hilbert space, the optimum bound for successive measurements of two-spin components, is seen to be strictly greater than the optimal bound for the case when they are measured on distinct ensembles, except when the spin components are mutually parallel or perpendicular  相似文献   
5.
The title compound was extracted from a natural product and its structure was characterized by an X-ray diffraction method. It crystallizes in the tetragonal space group P41 with cell parameters a = 15.832(10)A, c = 11.622(10)A, Z = 4; the final residual factor is R1 = 0.0769. The structure has both intra and intermolecular hydrogen bonds.  相似文献   
6.
Additive-subtractive phase modulated speckle interferometry (ASPMSI) is a technique that minimizes the susceptibility of speckle methods to environmental noise while providing fringes of good visibility. The method requires the acquisition of two consecutive video frames of additive-speckle images of the same two deformed states of an object at a rapid enough rate such that ambient noise is not a problem. The additive-speckle images as expected are of very poor visibility due to the presence of the self-interference term. An interframe phase-modulation is introduced and the two additive-speckle images are digitally subtracted to improve the fringe visibility by removing the self-interference term. The ASPM-SI method works with in-plane and out-of-plane deformation sensitive ESPI as well as with displacement-gradient sensitive speckle-shearing interferometry. It is shown that the ASPM-SI scheme has higher visibility than conventional additive-SI and performs consistently better than subtractive-SI schemes in the presence of partial interframe speckle decorrelating optical noise. Furthermore, it is shown that the fringe visibility of the out-of-plane displacement sensitive interferometer which uses a protected reference beam separate from the object beam can be made to be essentially unity even at complete interframe decorrelation.  相似文献   
7.
The crystal structures of pyrano­quinolines 9‐fluoro‐5‐phenyl‐3,4,4a,5,6,10b‐hexa­hydro‐2H‐pyrano[3,2‐c]quinoline, C18H18FNO, and 9‐methyl‐5‐phenyl‐3,4,4a,5,6,10b‐hexa­hydro‐2H‐pyrano­[3,2‐c]quinoline, C19H21NO, are isomorphous. In both structures, the pyran ring is exo to the six‐membered N‐heterocyclic ring formed in the cyclo­addition step. The torsion angles across the phenyl linkage for the two structures are −91.2 (1) and −88.3 (2)°. The striking feature in both crystal packings is that they do not contain the expected conventional hydrogen bonds, in spite of the presence of good hydrogen‐bonding functionalities. Possible C—H⋯π inter­actions are, however, observed.  相似文献   
8.
This is summary of the activities of the working group on collider physics in the IXth Workshop on High Energy Physics Phenomenology (WHEPP-9) held at the Institute of Physics, Bhubaneswar, India in January 2006. Some of the work subsequently done on these problems by the subgroups formed during the workshop is included in this report.  相似文献   
9.
10.
Hadroprduction ofJ/ψ in π? nucleus collisions is studied in the context of the colour singlet model using nuclear structure functions from three different models of the EMC effect. We conclude that it is possible to understand the data on the large transverse momentum (p T ) and small Feynmanx (x F ) of theJ/ψ in terms of the nuclear dependence of structure functions alone. We further show that these data can be used to distinguish between different models of the EMC effect, and that a study of distributions in various kinematic variables in photoproduction ofJ/ψ should be able to very effectively supplement the information obtained from hadroproduction experiments.  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