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   1385510篇
  免费   34120篇
  国内免费   12113篇
化学   695572篇
晶体学   14602篇
力学   77095篇
综合类   425篇
数学   247231篇
物理学   396818篇
  2021年   13454篇
  2020年   17059篇
  2019年   17301篇
  2018年   15797篇
  2017年   14355篇
  2016年   30059篇
  2015年   22264篇
  2014年   32067篇
  2013年   76802篇
  2012年   43131篇
  2011年   42623篇
  2010年   40862篇
  2009年   42833篇
  2008年   40146篇
  2007年   36647篇
  2006年   39858篇
  2005年   33192篇
  2004年   32968篇
  2003年   30054篇
  2002年   27571篇
  2001年   30079篇
  2000年   24618篇
  1999年   21398篇
  1998年   19566篇
  1997年   19978篇
  1996年   19751篇
  1995年   19036篇
  1994年   18582篇
  1993年   18036篇
  1992年   18394篇
  1991年   18524篇
  1990年   17787篇
  1989年   17709篇
  1988年   17281篇
  1987年   17255篇
  1986年   16178篇
  1985年   22666篇
  1984年   23758篇
  1983年   19790篇
  1982年   21391篇
  1981年   20603篇
  1980年   19925篇
  1979年   20416篇
  1978年   21574篇
  1977年   21289篇
  1976年   21054篇
  1975年   19743篇
  1974年   19417篇
  1973年   19917篇
  1972年   14365篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Different strategies for the preparation of efficient and robust immobilized biocatalysts are here reviewed. Different physico-chemical approaches are discussed.i.- The stabilization of enzyme by any kind of immobilization on pre-existing porous supports.ii.- The stabilization of enzymes by multipoint covalent attachment on support surfaces.iii.- Additional stabilization of immobilized-stabilized enzyme by physical or chemical modification with polymers.These three strategies can be easily developed when enzymes are immobilized in pre-existing porous supports. In addition to that, these immobilized-stabilized derivatives are optimal to develop enzyme reaction engineering and reactor engineering. Stabilizations ranging between 1000 and 100,000 folds regarding diluted soluble enzymes are here reported.  相似文献   
2.
Crystallography Reports - Fluoride crystals K2(Ta0.9I0.1)F7 (sp. gr. Р21/c) complementary to the K2TaF7 and K2NbF7 fluoride family have been obtained by hydrothermal synthesis. Their...  相似文献   
3.
Gaponov  S. A. 《Fluid Dynamics》2022,57(5):587-596
Fluid Dynamics - The problem of stability of a subsonic boundary layer is solved under the conditions of heat supply inside the boundary layer with injection of a homogeneous gas through a porous...  相似文献   
4.
Awad  A. M.  Askar  S. S.  Elsadany  A. A. 《Nonlinear dynamics》2022,107(4):3983-3999
Nonlinear Dynamics - In this paper, an economic competition between two firms that want to maximize the weighted-average social welfare and own profits is proposed. This kind of competition is...  相似文献   
5.
Crystallography Reports - The review presents the important unique results of the cycle of research led by M.V. Kovalchuk on the fundamental patterns of protein interactions and the protein...  相似文献   
6.
Journal of Applied Mechanics and Technical Physics - A method for determining the empirical dependence of the rheological properties of rocks on stresses has been developed and tested in...  相似文献   
7.
Journal of Experimental and Theoretical Physics - New data concerning neutrino oscillations as obtained in the T2K and NOvA accelerator neutrino experiments are considered. Both collaborations...  相似文献   
8.
Pomogaev  V. A.  Lee  H. J.  Goh  E.  Tchaikovskaya  O. N.  Kononov  A. I.  Avramov  P. V. 《Russian Physics Journal》2022,64(11):2076-2081
Russian Physics Journal - Theoretical calculations of excited states in the complexes of gold and silver three-atom nanoclusters with carbon quantum nanodots are performed using the M062X...  相似文献   
9.
This work demonstrates the analytical applicability of single ion-selective membranes (ISMs) and potentiometric sensor array to distinguish and detect cathinone derivatives. Potentiometric data from ISMs based on cation exchanger and varying content of calix[4]arene derivative were processed by principal component analysis (PCA). Such a combination of methods allowed discriminating various individual synthetic cathinones and their recognition from the mixture comprising primary amines (substituted amphetamines+aminoindane). Analytical parameters of ISM containing 1wt % of calix[4]arene derivative were sufficient to detect 1.0×10−4 mol.l−1 1-(4-fluorophenyl)-2-(ethylamino)butan-1-one and 2-(methylamino)-1-phenylbutan-1-one (buphedrone) in both model and saliva samples.  相似文献   
10.
Structural Chemistry - In the present work, the energy contribution of the sulfur atom in a heterocycle and in a disulfide bond in solid and gas phases was calculated. To achieve this goal,...  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