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   713558篇
  免费   7765篇
  国内免费   1762篇
化学   367252篇
晶体学   8064篇
力学   34376篇
综合类   27篇
数学   97399篇
物理学   215967篇
  2021年   5902篇
  2020年   7011篇
  2019年   7779篇
  2018年   10521篇
  2017年   10591篇
  2016年   15206篇
  2015年   8838篇
  2014年   13782篇
  2013年   32504篇
  2012年   25172篇
  2011年   29477篇
  2010年   21629篇
  2009年   21157篇
  2008年   27707篇
  2007年   27508篇
  2006年   25268篇
  2005年   22657篇
  2004年   20947篇
  2003年   18801篇
  2002年   18501篇
  2001年   18672篇
  2000年   14462篇
  1999年   11025篇
  1998年   9473篇
  1997年   9453篇
  1996年   8922篇
  1995年   8412篇
  1994年   8619篇
  1993年   8155篇
  1992年   8759篇
  1991年   9148篇
  1990年   8847篇
  1989年   8550篇
  1988年   8458篇
  1987年   8349篇
  1986年   7920篇
  1985年   10358篇
  1984年   10872篇
  1983年   9138篇
  1982年   9492篇
  1981年   8999篇
  1980年   8666篇
  1979年   9078篇
  1978年   9570篇
  1977年   9451篇
  1976年   9482篇
  1975年   8941篇
  1974年   8825篇
  1973年   9164篇
  1972年   6631篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
101.
Filippov  A. N. 《Colloid Journal》2022,84(3):332-343
Colloid Journal - The capillary-osmosis and reverse-osmosis coefficients of an ion-exchange membrane have been calculated as the kinetic coefficients of the Onsager matrix within the thermodynamics...  相似文献   
102.
103.
Doklady Physical Chemistry - The rheological behavior of a 1 wt % suspension of highly porous chitosan particles in polydimethylsiloxane in a high electric field has been studied as a function of...  相似文献   
104.
Journal of Structural Chemistry - N-cyanomethylanabasine is prepared with an yield of 70% by the interaction of the alkaloid anabasine with glyconitrile. It is shown that the highest yield of the...  相似文献   
105.
Journal of Inclusion Phenomena and Macrocyclic Chemistry - Novel neodymium phthalocyaninates based on template condensation of 4-[(4-benzyloxy)phenoxy]- or...  相似文献   
106.
During the past two decades, single-atom-centered medium-sized germanium clusters [M@Gen] (M=transition metals, n>12) have been extensively explored, both from theoretical perspectives and experimental gas-phase syntheses. However, the actual structural arrangements of the Ge13 and Ge14 endohedral cages are still ambiguous and have long remained an unresolved problem for experimental implementation. In this work, we successfully synthesize 13-/14-vertex Ge clusters [Nb@Ge13]3− ( 1 ) and [Nb@Ge14]3− ( 2 ), which are structurally characterized and exhibit unprecedented topologies, neither classical deltahedra nor 3-connected polyhedral structures. Theoretical analysis indicates that the major stabilization of the Ge backbones arises due to the substantial interaction of Ge 4p-AOs with the endohedral Nb 4d-AOs through three/four-center two-electron bonds with an enhanced electron density accumulated over the shortest Nb−Ge13 contact in 1 . Low occupancies of the direct two-center two-electron (2c–2e) Nb−Ge and Ge−Ge σ bonds point to a considerable degree of electron delocalization over the Ge cages revealing their electron deficiency.  相似文献   
107.
This review summarizes recent progress in understanding the oxygen reduction and evolution reactions at the lanthanum strontium manganite electrode of a high-temperature solid oxide cell. Information provided here is put into the perspective of the defect chemistry of lanthanum strontium manganite and its impact on the electrode reaction mechanisms itself. After summarizing recent views on the oxygen reduction reaction mechanism, the focus turns to the oxygen evolution reaction, which is significantly less treated in the literature. A combination of the information in the literature on both reactions was the basis for modified reaction mechanism of the oxygen evolution reaction to be proposed under consideration of recent experimental observations and theoretical findings.  相似文献   
108.
Crystallography Reports - The review is devoted to the current state of affairs and prospects for development in the field of neutron reflectometry on the existing and future neutron sources in the...  相似文献   
109.
Spin-crossover complexes with multistep transitions attract much attention due to their potential applications as multi-switches and for data storage. A four-step spin crossover is observed in the new iron(II)-based cyanometallic guest-free framework compound Fe(2-ethoxypyrazine)2{Ag(CN)2}2 during the transition from the low-spin to the high-spin state. A reverse process occurs in three steps. Crystallographic studies reveal an associated stepwise evolution of the crystal structures. Multiple transitions in the reported complex originate from distinct FeII sites which exist due to the packing of the ligand with a bulky substituent.  相似文献   
110.
Covalent functionalization of 2D materials provides a tailored approach towards tuning of their chemical, optical, and electronic properties making the search for new ways to graft small molecules important. Herein, the reaction with (3,5-bis(trifluoromethyl)phenyl)iodonium salt is revealed as an effective strategy for functionalization of MoTe2 thin films. Upon decomposition of the salt, the generated radicals graft covalently as aryl-(CF3)2 groups at the surface of both metallic (1T’) and semiconducting (2H) polymorphs of MoTe2. Remarkably, the reactivity of the salt is governed by the electronic structure of the given polymorph. While the functionalization of the metallic MoTe2 occurs spontaneously, the semiconducting MoTe2 requires activation by light. The reaction proceeds with the elimination of oxide from the original films yielding the functionalized products that remain protected in ambient conditions, presenting a viable solution to the ageing of MoTe2 in air.  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