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   1335269篇
  免费   30387篇
  国内免费   8393篇
化学   669153篇
晶体学   14718篇
力学   74891篇
综合类   161篇
数学   242043篇
物理学   373083篇
  2021年   13428篇
  2020年   16002篇
  2019年   16081篇
  2018年   12788篇
  2016年   28017篇
  2015年   20913篇
  2014年   30526篇
  2013年   74610篇
  2012年   39096篇
  2011年   36618篇
  2010年   37749篇
  2009年   40033篇
  2008年   35703篇
  2007年   31556篇
  2006年   37370篇
  2005年   30107篇
  2004年   30865篇
  2003年   28907篇
  2002年   29890篇
  2001年   28905篇
  2000年   25171篇
  1999年   22656篇
  1998年   21093篇
  1997年   20607篇
  1996年   19238篇
  1995年   18568篇
  1994年   18102篇
  1993年   17621篇
  1992年   17545篇
  1991年   17826篇
  1990年   17010篇
  1989年   17031篇
  1988年   16654篇
  1987年   16653篇
  1986年   15578篇
  1985年   22117篇
  1984年   23407篇
  1983年   19518篇
  1982年   21252篇
  1981年   20441篇
  1980年   19785篇
  1979年   20064篇
  1978年   21398篇
  1977年   21033篇
  1976年   20810篇
  1975年   19492篇
  1974年   19135篇
  1973年   19678篇
  1972年   14202篇
  1967年   12552篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
Russian Physics Journal - The specific features of the sorption activity of silver nanoparticles (AgNPs) on biodegradable polymers of natural (collagen) and artificial (polyamide 6.6) origin have...  相似文献   
102.
103.
A formal computation proving a new operator identity from known ones is, in principle, restricted by domains and codomains of linear operators involved, since not any two operators can be added or composed. Algebraically, identities can be modelled by noncommutative polynomials and such a formal computation proves that the polynomial corresponding to the new identity lies in the ideal generated by the polynomials corresponding to the known identities. In order to prove an operator identity, however, just proving membership of the polynomial in the ideal is not enough, since the ring of noncommutative polynomials ignores domains and codomains. We show that it suffices to additionally verify compatibility of this polynomial and of the generators of the ideal with the labelled quiver that encodes which polynomials can be realized as linear operators. Then, for every consistent representation of such a quiver in a linear category, there exists a computation in the category that proves the corresponding instance of the identity. Moreover, by assigning the same label to several edges of the quiver, the algebraic framework developed allows to model different versions of an operator by the same indeterminate in the noncommutative polynomials.  相似文献   
104.
Crystallography Reports - Neutron diffraction studies on the small-angle neutron spectrometer YuMO (Joint Institute for Nuclear Research, Dubna), based on the IBR-2 pulsed reactor, have been...  相似文献   
105.
Crystallography Reports - The crystal and molecular structures of Cl–C6H4–O–C16H33 (I) have been studied, and its differential scanning calorimetry (DSC) study is performed....  相似文献   
106.
Gawad  Dina A.  Elnaggar  Mai M.  Belal  Tarek S. 《Chromatographia》2022,85(7):617-628
Chromatographia - The present work deals with the optimization, validation and application of a versatile HPLC–DAD method for concurrent estimation of nine antimicrobials and proton pump...  相似文献   
107.
Crystallography Reports - Crystals of mutants of uridine phosphorylase from Shewanella oneidensis MR-1 at the active-site threonine residue were obtained, and the three-dimensional structures of...  相似文献   
108.
Crystallography Reports - The review describes the application of small-angle scattering (SAS) of neutrons and complementary methods to study the structures of biomacromolecules. Here we cover SAS...  相似文献   
109.
We investigate the possibility of phantom crossing in the dark energy sector and the solution for the Hubble tension between early and late universe observations. We use robust combinations of different cosmological observations, namely the Cosmic Microwave Background (CMB), local measurement of Hubble constant (H0), Baryon Acoustic Oscillation (BAO) and SnIa for this purpose. For a combination of CMB+BAO data that is related to early universe physics, phantom crossing in the dark energy sector was confirmed at a 95% confidence level and we obtained the constraint H0=71.03.8+2.9 km/s/Mpc at a 68% confidence level, which is in perfect agreement with the local measurement by Riess et al. We show that constraints from different combinations of data are consistent with each other and all of them are consistent with phantom crossing in the dark energy sector. For the combination of all data considered, we obtained the constraint H0=70.25±0.78 km/s/Mpc at a 68% confidence level and the phantom crossing happening at the scale factor am=0.8510.031+0.048 at a 68% confidence level.  相似文献   
110.
David Hull     
Journal of Optimization Theory and Applications -  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