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   1337728篇
  免费   30453篇
  国内免费   8437篇
化学   667296篇
晶体学   14966篇
力学   75131篇
综合类   162篇
数学   243237篇
物理学   375826篇
  2021年   13326篇
  2020年   16035篇
  2019年   16151篇
  2018年   14065篇
  2016年   28495篇
  2015年   21098篇
  2014年   30625篇
  2013年   74754篇
  2012年   39131篇
  2011年   37150篇
  2010年   38654篇
  2009年   40888篇
  2008年   36308篇
  2007年   32325篇
  2006年   36543篇
  2005年   30494篇
  2004年   30833篇
  2003年   28854篇
  2002年   29589篇
  2001年   28440篇
  2000年   24829篇
  1999年   22496篇
  1998年   20828篇
  1997年   19293篇
  1996年   19223篇
  1995年   18585篇
  1994年   18102篇
  1993年   17621篇
  1992年   17488篇
  1991年   17765篇
  1990年   16937篇
  1989年   16989篇
  1988年   16595篇
  1987年   16598篇
  1986年   15543篇
  1985年   22073篇
  1984年   23392篇
  1983年   19493篇
  1982年   21228篇
  1981年   20439篇
  1980年   19755篇
  1979年   20005篇
  1978年   21367篇
  1977年   21015篇
  1976年   20776篇
  1975年   19418篇
  1974年   19075篇
  1973年   19616篇
  1972年   14152篇
  1967年   12524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