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   8151篇
  免费   334篇
  国内免费   624篇
化学   4947篇
晶体学   249篇
力学   87篇
综合类   60篇
数学   2349篇
物理学   1417篇
  2023年   66篇
  2022年   96篇
  2021年   114篇
  2020年   148篇
  2019年   178篇
  2018年   98篇
  2017年   119篇
  2016年   133篇
  2015年   142篇
  2014年   176篇
  2013年   669篇
  2012年   492篇
  2011年   645篇
  2010年   590篇
  2009年   715篇
  2008年   645篇
  2007年   579篇
  2006年   471篇
  2005年   367篇
  2004年   349篇
  2003年   286篇
  2002年   373篇
  2001年   165篇
  2000年   156篇
  1999年   141篇
  1998年   124篇
  1997年   117篇
  1996年   121篇
  1995年   100篇
  1994年   91篇
  1993年   56篇
  1992年   64篇
  1991年   40篇
  1990年   23篇
  1989年   14篇
  1988年   15篇
  1985年   39篇
  1984年   20篇
  1983年   24篇
  1982年   24篇
  1981年   47篇
  1980年   31篇
  1979年   17篇
  1978年   25篇
  1977年   33篇
  1976年   28篇
  1975年   25篇
  1974年   28篇
  1973年   23篇
  1971年   17篇
排序方式: 共有9109条查询结果,搜索用时 31 毫秒
961.
We discovered a simple quadratic equation, which relates scattering phases of particles on Fermi surface. We consider one-dimensional Bose gas and XXZ Heisenberg quantum spin chain. Received: 4 December 1997 / Accepted: 17 March 1998  相似文献   
962.
Irradiation caused DNA single-strand breaks in S180 cells in the presence oflaser-hematoporphyrin derivative(HPD).The number of single strand breaks was 3.69 ×10~(10)break dolton~(-1).The analysis of base composition of DNA showed that the effect of laser-HPDirradiation on guanine was the highest,being 5-12 times as high as those of the three others(adenine,cytosine and thymine).It was different from the nature of DNA damage caused by γ-ray irradiation.  相似文献   
963.
964.
We define for every so-called admissible relation r in the Steenrod algebra A and for every oriented spherical fibration ξ over a CW-space an exotic characteristic class (mod 2) ε(r)(ξ), which is primitive and vanishes for sphere bundles. The set of exotic classes associated with the universal spherical fibration and the admissible Adem relations are compared with the algebra generators of H1(BSG;Z2) due to Milgram. Moreover, their behaviour under the action of A is computed. Finally, we give a secondary Wu formula for exotic classes of special Poincaré duality spaces.  相似文献   
965.
Certain Stiefel-Whitney classes of manifolds with smooth, effective toral actions are shown to be computable in terms of Poincare duals of fixed point sets of isotropy subgroups. As an application the toral degrees of symmetry of certain Dold manifolds are determined.  相似文献   
966.
A previous analysis of the charge (Z) correlations in the ΔZZ plane for 129Xe+natSn central collisions at 32 MeV/n has shown an enhancement in the production of equally sized fragments (low ΔZ) which was interpreted as an evidence for spinodal decomposition. However, the signal is weak and rises the question of the estimation of the uncorrelated yield. After a critical analysis of its robustness, we propose in this paper a new technique to build the uncorrelated yield in the charge correlation function. The application of this method to 129Xe+natSn central collision data at 32, 39, 45 and 50 MeV/n does not show any particular enhancement of the correlation function in any ΔZ bin.  相似文献   
967.
A method for the microdetermination of periodate in the presence of iodate is presented. It is based on reduction of periodate to iodate by leucothionine generated in situ by photochemical reaction between EDTA and blue thionine. Biamperometric curves are used for evaluation, representing reduction time for the periodate versus the current generated in the oxidation of the Tred in excess after the end-point. A polarographic study of the process is presented. An applied potential of 100 mV is suitable for the biamperometric measurements with Pt—Pt electrodes. The method is applicable for 0.4–45 ppm periodate. Iodate does not interfere up to IO-3 : IO-4 ratios of 100:1.  相似文献   
968.
Explicit examples of finite subgroups of the group of homotopy classes of self-homotopy equivalences of some flat Riemannian manifolds which cannot be lifted to effective actions are given. It is also shown that no finite subgroups of the kernel of π0(Homeo(M))→Out π1(M) can be lifted back to Homeo(M), for a large class of flat manifolds M. Some results of an earlier paper by the authors are refined and related to recent work of R. Schoen and S.T. Yau.  相似文献   
969.
Precipitate-type electrodes (benzidine sulfate or phosphate and hexammino-cobalt(III) nitrate in silicone rubber), and liquid ion-exchanger electrodes based on quaternary ammonium and phosphonium and triphenyltin salts were tested for the assay of phosphate ions. Good sensitivity was achieved with the phosphonium and triphenyltin salts, but both lacked sufficient selectivity for routine-assays.  相似文献   
970.
Amperometric oxygen electrodes are useful transducers for enzymatic analyses. One must, however, account for contributions from oxygen incorporation or depletion caused by sample introduction, stirring and diffusion, or non-enzymatic reactions, as well as for instrumental response time. Examples of various characteristics of these contributions are shown and discussed from a theoretical basis.  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