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   409008篇
  免费   3426篇
  国内免费   954篇
化学   206627篇
晶体学   6537篇
力学   19382篇
综合类   7篇
数学   54217篇
物理学   126618篇
  2018年   11114篇
  2017年   11921篇
  2016年   8347篇
  2015年   3841篇
  2014年   4633篇
  2013年   13202篇
  2012年   13389篇
  2011年   23251篇
  2010年   14755篇
  2009年   14720篇
  2008年   20607篇
  2007年   23831篇
  2006年   10509篇
  2005年   15965篇
  2004年   11931篇
  2003年   11001篇
  2002年   8890篇
  2001年   10188篇
  2000年   7780篇
  1999年   5918篇
  1998年   4489篇
  1997年   4587篇
  1996年   4576篇
  1995年   4179篇
  1994年   4073篇
  1993年   3784篇
  1992年   4586篇
  1991年   4579篇
  1990年   4411篇
  1989年   4395篇
  1988年   4309篇
  1987年   4323篇
  1986年   4032篇
  1985年   5269篇
  1984年   5334篇
  1983年   4404篇
  1982年   4572篇
  1981年   4398篇
  1980年   4312篇
  1979年   4670篇
  1978年   5048篇
  1977年   4726篇
  1976年   4656篇
  1975年   4418篇
  1974年   4334篇
  1973年   4421篇
  1972年   2916篇
  1968年   2800篇
  1967年   2822篇
  1966年   2505篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
81.
82.
Molecular Diversity - Hypertension is a medical condition that affects millions of people worldwide. Despite the high efficacy of the current antihypertensive drugs, they are associated with...  相似文献   
83.
Luyen  D. T. 《Mathematical Notes》2022,112(1-2):239-250
Mathematical Notes - We study the multiplicity of weak solutions to the boundary-value problem $$\begin{alignedat}{2} - M\biggl(\iint_{\mathbb R^{2N}}|u(x)-u(y)|^2 K(x-y)\,d x\,d y\biggr)\mathscr...  相似文献   
84.

A procedure was suggested for preparing brominated polyols of reduced viscosity for the synthesis of foamed polyurethanes of reduced flammability. The flame-retarding action of the synthesized polyol tetrabromophthalate in polyurethane was studied in comparison with that of other widely used flame retardants. Evaluation of the effect exerted on the flammability of the polurethane compound by the polyol tetrabromophthalate synthesized, melamine, and aluminum hydroxide shows that all the samples containing flame retardants are self-extinguishing. The shortest combustion time was observed for the sample containing 6% polyol tetrabromophthalate synthesized. The sample containing as a flame retardant additive solely the synthesized polyole tetrabromophthalate also exhibits the highest performance as a heat-insulating material from the viewpoint of thermal conductivity.

  相似文献   
85.
Sargsyan  A.  Vartanyan  T. A.  Sarkisyan  D. 《Optics and Spectroscopy》2021,129(11):1173-1178
Optics and Spectroscopy - A cell with a submicron thickness was used to measure the broadening and shift of the D1 and D2 lines of Rb atoms by neon. The resolution of hypefine components...  相似文献   
86.
Exosomes are nanovesicles secreted by most cellular types that carry important biochemical compounds throughout the body with different purposes, playing a preponderant role in cellular communication. Because of their structure, physicochemical properties and stability, recent studies are focusing in their use as nanocarriers for different therapeutic compounds for the treatment of different diseases ranging from cancer to Parkinson's disease. However, current bioseparation protocols and methodologies are selected based on the final exosome application or intended use and present both advantages and disadvantages when compared among them. In this context, this review aims to present the most important technologies available for exosome isolation while discussing their advantages and disadvantages and the possibilities of being combined with other strategies. This is critical since the development of novel exosome‐based therapeutic strategies will be constrained to the effectiveness and yield of the selected downstream purification methodologies for which a thorough understanding of the available technological resources is needed.  相似文献   
87.
Vorob’ev  N. T.  Lantsetova  E. D. 《Mathematical Notes》2021,110(5-6):655-665
Mathematical Notes - It is proved that the lattice of all Fitting classes of finite groups is not distributive, and conditions under which Fitting classes satisfy the distributive and modular laws...  相似文献   
88.
Physics of Atomic Nuclei - The paper presents a comparison of three neutrons identifying methods in scintillators based on ZnS with 6Li and 10B: charge integration method, pulse gradient analysis,...  相似文献   
89.
Xu  H. J.  Zhang  Q. G.  Debenest  G. 《Transport in Porous Media》2021,140(3):625-627
Transport in Porous Media - The theme of coupling problems for adsorption, absorption and thermochemical transport in porous media is very important for engineering applications. Based on the...  相似文献   
90.
Aliev  A. B.  Shafieva  G. H. 《Differential Equations》2022,58(8):1028-1042
Differential Equations - We study a mixed problem for systems of one-dimensional semilinear hyperbolic equations with variable nonlinearity growth rate and nonlinear boundary conditions. Theorems...  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