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   1990篇
  免费   93篇
  国内免费   4篇
化学   1543篇
晶体学   21篇
力学   32篇
数学   87篇
物理学   404篇
  2023年   13篇
  2022年   11篇
  2021年   17篇
  2020年   24篇
  2019年   40篇
  2018年   28篇
  2017年   17篇
  2016年   51篇
  2015年   37篇
  2014年   49篇
  2013年   92篇
  2012年   116篇
  2011年   149篇
  2010年   69篇
  2009年   56篇
  2008年   137篇
  2007年   103篇
  2006年   130篇
  2005年   113篇
  2004年   97篇
  2003年   90篇
  2002年   81篇
  2001年   42篇
  2000年   38篇
  1999年   31篇
  1998年   19篇
  1997年   21篇
  1996年   17篇
  1995年   18篇
  1994年   17篇
  1993年   12篇
  1992年   21篇
  1991年   16篇
  1990年   27篇
  1989年   17篇
  1988年   22篇
  1987年   16篇
  1986年   23篇
  1985年   17篇
  1984年   27篇
  1983年   20篇
  1982年   19篇
  1981年   14篇
  1980年   12篇
  1979年   15篇
  1978年   11篇
  1977年   7篇
  1976年   12篇
  1975年   11篇
  1974年   11篇
排序方式: 共有2087条查询结果,搜索用时 312 毫秒
1.
Journal of Radioanalytical and Nuclear Chemistry - Extraction chromatography flow-sheet employing octyl(phenyl)-N,N-diisobutylcarbonoylmethylphosphine oxide and bis(2-ethylhexyl) hydrogen phosphate...  相似文献   
2.
Three new cytotoxic polyacetylenes, PQ-1 (1), PQ-2 (2) and PQ-3 (3), have been isolated from Panax quinquefolium. The structures of these acetylenes were determined by analyses of their 1H-1H and 1H-13C COSY spectra. All these compounds exhibited strong cytotoxic activities against leukemia cells (L 1210) in tissue culture.  相似文献   
3.
We report the recent development on the SUSY calculations with the help of GRACE system. GRACE/SUSY/1LOOP is the computer code which can generate Feynman diagrams in the MSSM automatically and compute one-loop amplitudes in the numerical way. We present new results of various two-body decay widths and chargino pair production at ILC (international linear collider) at one-loop level.   相似文献   
4.
Tsuyoshi Kitamura 《Tetrahedron》2004,60(43):9649-9657
Synthesis of (+)-anthramycin was examined. A pyrrolobenzodiazepine skeleton could be synthesized by reductive cyclization of pyrrolidine derivative, which was obtained by enyne metathesis. The conjugated enamide ester part of (+)-anthramycin derivative was constructed by cross-metathesis.  相似文献   
5.
Within the large literature on inter-organizational networks, there has been some discussion of linking-pin organizations and the role they play in integrating these networks. Based on this verbal specification of linking-pin organizations, we construct operational criteria and empirical methods for identifying these structurally important organizations in potentially large and complex inter-organizational networks. These methods are based on ideas drawn from blockmodeling, structural holes, centrality and centralization of networks, and identifying cut-points in networks. These methods are applied to a constructed example and then to real empirical inter-organizational networks. Implications and contrasts with other methods are discussed, together with some open problems.  相似文献   
6.
7.
Threshold radiant exposures for grossly apparent immediate whitening and ultrastructural alterations of melanosomes in black guinea pig skin were determined for a series of red visible laser pulses ranging from 4 x 10(-4) to 6.5 x 10(-14) s. Threshold exposures for melanosomal injury were found to be independent of pulsewidth when the pulsewidths were below the estimated thermal relaxation time of melanosomes. Threshold radiant exposures for melanosomal injury were found to increase when the pulsewidths were approximately equal to or above the thermal relaxation time of melanosomes. At longer pulse durations, fracturing of melanosomes was not observed despite the longer exposures necessary for injury. Instead, perimelanosomal vacuoles were noted. These findings are consistent with the theory of selective photothermolysis and provide evidence for the thermal initiation of melanosomal disruption.  相似文献   
8.
This paper derives a conservation law for mean waiting times in a single-server multi-class service queueing system (M X/G/1 type queue) with setup times which may be dependent on multiple customer classes and its arrival batch size by using the work decomposition property in the queueing system with vacations.  相似文献   
9.
We investigate low-temperature behaviors of a system with chirality-pair interaction on a one-dimensional lattice. In the course of the investigation, we evaluate asymptotic forms of the characteristic values of the integral equation satisfied by the Mathieu functions. It turns out that the low-temperature behavior of correlation length of the chirality-pair correlation function is different from the one for the Ising model of spin ±1 but akin to the one for the Ising model of infinite spin.  相似文献   
10.
13C NMR studies showed that the population of the norcaradiene form of the title systems containing p-CH3O, H, and p-CF3 on the 7-aryl group increases in this order. The result is consistent with the prediction from the π-acceptor strength of the aryl group estimated by INDO calculations.  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