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   219412篇
  免费   1847篇
  国内免费   653篇
化学   120519篇
晶体学   3306篇
力学   8510篇
综合类   6篇
数学   23767篇
物理学   65804篇
  2020年   2015篇
  2019年   2301篇
  2018年   3228篇
  2017年   3137篇
  2016年   4334篇
  2015年   2426篇
  2014年   3897篇
  2013年   9435篇
  2012年   7056篇
  2011年   8631篇
  2010年   6177篇
  2009年   6012篇
  2008年   8334篇
  2007年   8405篇
  2006年   7803篇
  2005年   7123篇
  2004年   6325篇
  2003年   5823篇
  2002年   5648篇
  2001年   6038篇
  2000年   4801篇
  1999年   3532篇
  1998年   3063篇
  1997年   3084篇
  1996年   2920篇
  1995年   2380篇
  1994年   2477篇
  1993年   2527篇
  1992年   2670篇
  1991年   2721篇
  1990年   2626篇
  1989年   2584篇
  1988年   2537篇
  1987年   2493篇
  1986年   2413篇
  1985年   3107篇
  1984年   3263篇
  1983年   2598篇
  1982年   2874篇
  1981年   2765篇
  1980年   2554篇
  1979年   2784篇
  1978年   2873篇
  1977年   2922篇
  1976年   2889篇
  1975年   2743篇
  1974年   2726篇
  1973年   2868篇
  1972年   1904篇
  1967年   1846篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
141.
Nonperturbative nolocal structure of QCD vacuum is well described by instanton model. Specific helicity and flavor structure of zero modes of quarks, in instanton field allows simultaneously to explain some important features of low-and high-energy hadron phenomemology. The basic characteristics of hadron spectrum, partonic sum rules, heavyquark potential etc within the instanton liquid model are briefly discussed.  相似文献   
142.
We investigate the replica symmetry breaking (RSB) in a neighborhood of the instability point of the replica-symmetric solution in the axial quadrupolar glass model. We show that the solution with the first-stage RSB is stable against the subsequent RSB. Although there is no reflection symmetry, the first-stage RSB solution continuously bifurcates from the replica-symmetric one. This implies that our model does not belong to either of the two classes into which spin glasses are usually divided.  相似文献   
143.
The microhardness and content of carbon in electroplated gold coatings were studied as influenced by the operation time of citrate and citrate-phosphate gold-plating electrolytes. Such physicomechanical properties as porosity, microhardness, internal stress, plasticity, and microstructure of electroless-plated and electroplated nickel coatings were studied and analyzed.  相似文献   
144.
Muon electron pairs were detected in an Al multiplate spark chamber, exposed to a neutrino beam from the CERN PS. The leptons were not accompanied by other particles, except occasionally by protons. The background came mainly from muon associated π0 production, with one decay gamma lost. It was determined empirically, together with the small contribution from υ e reactions. For electron energies above 2 GeV the background is 5.7±1.5 events, whereas 18 (μe)-candidates have been observed. Hence the effect is established, with a rate of about 10?4 as compared to the muonic reactions above 3 GeV. Charm creation as the origin of this (μe)-production process is excluded; heavy neutral lepton production does not fit the kinematics observed. Instead the events are compatible with the two-body decay of an object with variable invariant mass of order 1 GeV, possibly resulting from axion interactions.  相似文献   
145.
146.
147.
148.
A convenient method is proposed for the synthesis of all the individual methyl ethers of methyl 2-acetamido-2-deoxy-α-D-glucopyranoside based on the partial methylation of 2-acetamido-2-deoxy-α-D-glucopyranoside with dimethyl sulfate in an alkaline medium followed by preparative liquid column chromatography on silica gel of the resulting mixture of methyl ethers.  相似文献   
149.
Tricyclic skeletons have been generated from acyclic enyne precursors by using an intramolecular Pauson-Khand reaction in combination with aldol, Michael and alkylation reactions.  相似文献   
150.
A test for a function to be a solution of an elliptic PDE is given in terms of extensions, as solutions, from the boundaries inside the domains belonging to an isotopic family. It generalizes a result of Ehrenpreis for spheres moved along a straight line.

  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