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   10254篇
  免费   429篇
  国内免费   87篇
化学   7042篇
晶体学   91篇
力学   267篇
综合类   1篇
数学   1741篇
物理学   1628篇
  2023年   77篇
  2022年   61篇
  2021年   192篇
  2020年   209篇
  2019年   250篇
  2018年   158篇
  2017年   159篇
  2016年   384篇
  2015年   288篇
  2014年   320篇
  2013年   603篇
  2012年   607篇
  2011年   653篇
  2010年   453篇
  2009年   405篇
  2008年   586篇
  2007年   630篇
  2006年   494篇
  2005年   547篇
  2004年   440篇
  2003年   350篇
  2002年   336篇
  2001年   162篇
  2000年   146篇
  1999年   98篇
  1998年   103篇
  1997年   109篇
  1996年   114篇
  1995年   93篇
  1994年   84篇
  1993年   100篇
  1992年   74篇
  1991年   76篇
  1990年   69篇
  1989年   64篇
  1988年   48篇
  1987年   54篇
  1986年   64篇
  1985年   102篇
  1984年   99篇
  1983年   77篇
  1982年   66篇
  1981年   70篇
  1980年   62篇
  1979年   64篇
  1978年   67篇
  1977年   41篇
  1976年   40篇
  1975年   50篇
  1974年   53篇
排序方式: 共有10000条查询结果,搜索用时 123 毫秒
981.
This article presents extensions of the Cramér-Wold theorem to measures that may have infinite mass near the origin. Corresponding results for sequences of measures are presented together with examples showing that the assumptions imposed are sharp. The extensions build on a number of results and methods concerned with injectivity properties of the Radon transform. Using a few tools from distribution theory and Fourier analysis we show that the presented injectivity results for the Radon transform lead to Cramér-Wold type results for measures. One purpose of this article is to contribute to making known to probabilists interesting results for the Radon transform that have been developed essentially during the 1980s and 1990s.  相似文献   
982.
983.
Performance of homonuclear coupling sign edited (HCSE) experiment applied to detection of signed carbon–carbon couplings is discussed using a set of already measured samples of nine monosubstituted benzenes. It is shown that coupling sign detection is insensitive to the settings of carbon–carbon polarization transfer delays. The HCSE spectra of ten from the total of 43 measured carbon–carbon couplings were considerably influenced by relaxations and proton–proton strong couplings. These effects are quantitatively discussed. The results of HCSE and SLAP experiments are compared. It is shown that the two methods may complement each other in detection of signed carbon–carbon couplings. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   
984.
985.
Two gold(I) complexes of the (NHC)AuX type bearing a triazole‐based N‐heterocyclic carbene (NHC) ligand (1‐tert‐butyl‐4‐(4‐methylphenyl)‐3‐phenyl‐1H‐1,2,4‐triazol‐4‐ium‐5‐ylidene) and various halide ligands (X = Br, I) were synthesized and characterized in solution using NMR spectroscopy as well as in the solid state using X‐ray diffraction techniques. The cytotoxic properties of both compounds and the precursor, (NHC)AuCl, were screened against a panel of human tumour cell lines including liver cancer (HepG2), cervical cancer (HeLa S3) and leukaemia (CCRF‐CEM, HL‐60) and compared to cisplatin and auranofin. It was found that the activities of the chloro and bromo derivatives were generally superior to that of cisplatin and slightly less effective compared to auranofin, except for HepG2 cells where auranofin was not as effective. In addition, the ability to induce membrane phosphatidyl serine externalization as a hallmark of apoptosis in CCRF‐CEM leukaemic cells was investigated. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   
986.
Optimal trading strategies are found for an insider who is trading in two convergent stocks and is bound by margin constraints.  相似文献   
987.
A common generalization of effect algebras and ortholattices that allows to represent ortholattices in a similar way in which orthomodular lattices are represented in the setting of effect algebras is introduced.  相似文献   
988.
989.
990.
Single crystals of the title compound, C9H10N3O3+·Cl·H2O, were obtained by recrystallization from hydrochloric acid. The cations stack along the crystallographic a direction. The 2,3‐dioxo‐1,4‐dihydroquinoxaline group shows a significant deviation from planarity [r.m.s. deviation from the best plane = 0.063 (2) Å]. Hydrogen bonding links the cations, chloride anions and water molecules to form an extended three‐dimensional architecture.  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