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   2034篇
  免费   11篇
  国内免费   2篇
化学   1051篇
晶体学   24篇
力学   52篇
数学   182篇
物理学   738篇
  2021年   40篇
  2020年   26篇
  2019年   39篇
  2018年   43篇
  2017年   51篇
  2016年   70篇
  2015年   28篇
  2014年   48篇
  2013年   82篇
  2012年   68篇
  2011年   91篇
  2010年   80篇
  2009年   74篇
  2008年   86篇
  2007年   78篇
  2006年   64篇
  2005年   61篇
  2004年   55篇
  2003年   48篇
  2002年   56篇
  2001年   43篇
  2000年   40篇
  1999年   38篇
  1998年   20篇
  1997年   27篇
  1996年   22篇
  1995年   19篇
  1994年   26篇
  1993年   20篇
  1992年   31篇
  1991年   21篇
  1990年   26篇
  1989年   22篇
  1988年   23篇
  1987年   29篇
  1986年   21篇
  1983年   20篇
  1982年   22篇
  1980年   21篇
  1979年   18篇
  1978年   36篇
  1977年   22篇
  1976年   18篇
  1975年   24篇
  1974年   26篇
  1973年   21篇
  1972年   18篇
  1971年   18篇
  1968年   20篇
  1967年   18篇
排序方式: 共有2047条查询结果,搜索用时 8 毫秒
941.
942.
The reaction of the divalent ruthenium complexes [CpFRuCl]n and [CpFRu(MeCN)3]PF6 with substituted pentafulvenes 1,2-(Me2NCH)(CO2Et)C5H3 and 1,3-(Me2NCH)(CO2Et)- C5H3 followed by hydrolysis affords new homoannular disubstituted ruthenocenes {1,2- (CO2Et)(CHO)C5H3}RuCpF and {1,3-(CO2Et)(CHO)C5H3}RuCpF (CpF = C5Me4CF3), re- spectively.  相似文献   
943.
Polymolybdates of the composition Cs2Mo4O13 (1) and Cs4Mo8O26 · 4H2O (2) are synthesized under hydrothermal conditions from a mixture containing (NH4)6Mo7O24 · 4H2O and CsCl at pH 2.5 and 3.6, respectively.  相似文献   
944.
近年研究表明二茂铁的环钯化衍生物被广泛地应用于各类偶联反应中,比如Heck反应、Suzuki反应、aza-Claisen重排反应等.主要综述了含氮导向基的二茂铁衍生物的环钯化反应,包括通过不对称诱导或拆分手段合成具有平面手性环钯化合物,基于环金属化反应1,1'-取代二茂铁钯化物的合成,以及其在催化反应的应用.  相似文献   
945.
The classical factorization method reduces the study of a system of ordinary differential equations Ut=[U+, U] to solving algebraic equations. Here U(t) belongs to a Lie algebra which is the direct sum of its subalgebras and , where “+” signifies the projection on . We generalize this method to the case . The corresponding quadratic systems are reducible to a linear system with variable coefficients. It is shown that the generalized version of the factorization method can also be applied to Liouville equation-type systems of partial differential equations. Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 110, No. 3, pp. 339–350, March, 1997.  相似文献   
946.
A convenient method is proposed for obtaining difficultly available derivatives of 2-amino-5-chloromethyl-2-thiazoline by the cyclization of N-allythioureas under the action of-chloronitrosoalkanes. It is assumed that the reaction proceeds as a halogenophilic process leading to the intermediate formamidinesulfenyl chloride which is rapidly and selectively cyclized with the formation of 2-amino-2-thiazoline derivatives.Institute of Physiologically Active Substances, Russian Academy of Sciences, Chernogolovka 142432, Russia. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 381–384, March, 1998.  相似文献   
947.
948.
A model of magnetic field generation by the turbulent motions of a highly conducting fluid is constructed. It is assumed that the field is generated in individual cells of space in a statistically independent manner. A coupling between the cells is realized by magnetic diffusion. The rates of growth of the field and its moments are calculated. The field distribution generated by this mechanism possesses an intermittent nature in both time and space.  相似文献   
949.
Using the freon filled bubble chamber SKAT at the Serpukhov accelerator we study event charge distributions in neutrino and antineutrino charged current reactions in the (anti)neutrino energy region from 3–30 GeV. We derive from the data the total cross section ratios of reactions on neutrons to reactions on protonsR ν=2.24±0.18 and \(R_{\bar v} = 0.43\) in agreement with the predictions of the quark parton model. These values agree also with other experimental results at different energies. For neutrino reactions we study additionally the differential distributions in Bjorken variablesx andy.  相似文献   
950.
The polarized (VV) and depolarized (VH) light scattering spectra of polyisobutylene, poly(methyl methacrylate), and glycerol were measured in the gigahertz frequency range at temperatures below and above the glass transition. Both VV and VH spectra exhibit a significant constant loss contribution that appears as a frequency‐independent imaginary part of the susceptibility spectrum. Existence of the frequency‐independent susceptibility in VV spectra below the Brillouin lines suggests that the constant loss also appears in mechanical relaxation in the gigahertz frequency range. Intensity of the constant loss increases strongly with temperature. Analysis of the spectra and literature data suggests that the constant loss can be general for many glass‐forming systems, but it is hidden in many cases by other relaxation contributions. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 40: 201–209, 2002  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