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   32160篇
  免费   6026篇
  国内免费   3359篇
化学   22952篇
晶体学   363篇
力学   1882篇
综合类   138篇
数学   3087篇
物理学   13123篇
  2024年   144篇
  2023年   720篇
  2022年   1243篇
  2021年   1347篇
  2020年   1447篇
  2019年   1425篇
  2018年   1217篇
  2017年   1087篇
  2016年   1660篇
  2015年   1583篇
  2014年   2022篇
  2013年   2471篇
  2012年   2992篇
  2011年   3004篇
  2010年   1954篇
  2009年   1855篇
  2008年   2092篇
  2007年   1818篇
  2006年   1704篇
  2005年   1365篇
  2004年   1026篇
  2003年   796篇
  2002年   790篇
  2001年   609篇
  2000年   493篇
  1999年   617篇
  1998年   527篇
  1997年   518篇
  1996年   506篇
  1995年   444篇
  1994年   353篇
  1993年   288篇
  1992年   290篇
  1991年   243篇
  1990年   213篇
  1989年   153篇
  1988年   95篇
  1987年   86篇
  1986年   104篇
  1985年   76篇
  1984年   38篇
  1983年   49篇
  1982年   29篇
  1981年   23篇
  1980年   11篇
  1979年   5篇
  1976年   3篇
  1957年   4篇
  1946年   1篇
  1923年   1篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
991.
Phototriggered intramolecular isomerization in a series of ruthenium sulfoxide complexes, [Ru(L)(tpy)(DMSO)]n+ (where tpy=2,2’:6’,2’’‐terpyridine; DMSO=dimethyl sulfoxide; L=2,2’‐bipyridine (bpy), n=2; N,N,N’,N’‐tetramethylethylenediamine (tmen) n=2; picolinate (pic), n=1; acetylacetonate (acac), n=1; oxalate (ox), n=0; malonate (mal), n=0), was investigated theoretically. It is observed that the metal‐centered ligand field (3MC) state plays an important role in the excited state S→O isomerization of the coordinated DMSO ligand. If the population of 3MCS state is thermally accessible and no 3MCO can be populated from this state, photoisomerization will be turned off because the 3MCS excited state is expected to lead to fast radiationless decay back to the original 1GSS ground state or photodecomposition along the Ru2+?S stretching coordinate. On the contrary, if the population of 3MCS (or 3MCO) state is inaccessible, photoinduced S→O isomerization can proceed adiabatically on the potential energy surface of the metal‐to‐ligand charge transfer excited states (3MLCTS3MLCTO). It is hoped that these results can provide valuable information for the excited state isomerization in photochromic d6 transition‐metal complexes, which is both experimentally and intellectually challenging as a field of study.  相似文献   
992.
993.
994.
995.
Adhesive force between two solid surfaces can lead to stiction failure of the micro-electro-mechanical systems (MEMS) device. The competition between the adhesive force and the beam restoring force determines whether the stiction occurs or not. Previous models assume that the stuck beam deforms either as the arc-shape or the S-shape, which causes significant differences in the measurements of adhesion and disputations among researchers. The contact mechanics model presented in this paper shows that the assumptions of the arc-shape and S-shape on the beam deformation over-simplify the problem; both the arc-shaped deformation and S-shaped deformation significantly deviate from the real ones. The previous theories are shown to be incompatible with the recent experimental results. The model presented in this paper attempts to explain those new experimental results and resolve some disputations on the previous models. The instabilities of jump-in during loading process and jump-off during unloading process are also incorporated in this model.  相似文献   
996.
A general and efficient synthetic method of 1-phenoxy-3-arylseleno-2-propanol by reducing diary1 diselenides with sodium borohydride in basic environment and their reaction with epoxypropoxyphenols are described.  相似文献   
997.
Chen  Rixiong  Yu  Shuhui  Sun  Rong  Yang  Wenhu  Zhao  Yubao 《Journal of Solid State Electrochemistry》2012,16(11):3635-3641
Journal of Solid State Electrochemistry - Graphene with highly flaky state has been successfully prepared through chemical reduction process with the assistance of potassium chloride (KCl) to...  相似文献   
998.
After the Higgs discovery, precise measurements of the Higgs properties and the electroweak observables become vital for the experimental particle physics. A powerful Higgs/Z factory, the Circular Electron Positron Collider (CEPC) is proposed. The Particle Flow oriented detector design is proposed to the CEPC and a Particle Flow algorithm, Arbor is optimized accordingly. We summarize the physics object reconstruction performance of the Particle Flow oriented detector design with Arbor algorithm and conclude that this combination fulfills the physics requirement of CEPC.  相似文献   
999.
Russian Journal of Physical Chemistry A - A new mesoporous carbon containing nitrogen and copper was prepared by carbonizing a polymer obtained by blending p-phenylenediamine, copper(II) sulfate,...  相似文献   
1000.
Most existing social learning models assume that there is only one underlying true state. In this work, we consider a social learning model with multiple true states, in which agents in different groups receive different signal sequences generated by their corresponding underlying true states. Each agent updates his belief by combining his rational self-adjustment based on the external signals he received and the influence of his neighbors according to their communication. We observe chaotic oscillation in the belief evolution, which implies that neither true state could be learnt correctly by calculating the largest Lyapunov exponents and Hurst exponents.  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