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   1764篇
  免费   59篇
  国内免费   7篇
化学   1219篇
晶体学   13篇
力学   29篇
数学   116篇
物理学   453篇
  2023年   14篇
  2022年   14篇
  2021年   12篇
  2020年   20篇
  2019年   21篇
  2018年   16篇
  2017年   9篇
  2016年   38篇
  2015年   30篇
  2014年   36篇
  2013年   74篇
  2012年   80篇
  2011年   96篇
  2010年   56篇
  2009年   57篇
  2008年   106篇
  2007年   103篇
  2006年   99篇
  2005年   99篇
  2004年   77篇
  2003年   60篇
  2002年   44篇
  2001年   38篇
  2000年   45篇
  1999年   27篇
  1998年   18篇
  1997年   17篇
  1996年   36篇
  1995年   13篇
  1994年   26篇
  1993年   23篇
  1992年   28篇
  1991年   23篇
  1990年   23篇
  1989年   33篇
  1988年   29篇
  1987年   24篇
  1986年   28篇
  1985年   26篇
  1984年   28篇
  1983年   14篇
  1982年   14篇
  1981年   25篇
  1980年   13篇
  1978年   19篇
  1977年   10篇
  1976年   15篇
  1975年   16篇
  1973年   15篇
  1969年   8篇
排序方式: 共有1830条查询结果,搜索用时 453 毫秒
241.
242.
We have recently observed two patients with superior vena caval syndrome who showed a unique abnormality, so called "Hot Spot", on the 99mTc-phytate liver scintigraphy. This phenomenon seems to be related to the collateral venous circulation. It is supposed that its manifestation depends on the degree of venous dilatation of the chest and abdominal wall.  相似文献   
243.
The differential cross section and the vector and tensor analyzing powers Ay, Axx, Ayy and Axz were measured for the d-4He elastic scattering at 56 MeV. The measurement of Axz was performed using a deuteron beam polarized in the horizontal plane. An optical-model analysis of the experimental data was carried out. The magnitude of the tensor analyzing powers could not be reproduced without the tensor potential. By including the TR type tensor potential, the optical-model calculations give a reasonable reproduction of the experimental data at θc.m. < 120°. The obtained TR tensor potential was much stronger than that predicted by the folding model. The strength of the real TR potential was roughly in accordance with that obtained from the optical-model analysis of d-4He elastic scattering at 20.2 MeV.  相似文献   
244.
245.
A method is described for the determination of benzethonium and benzalkonium compounds (1–5 × 10?6 M) based on the formation of ion-associates with bromocresol green (BCG) and quinine in 1,2-dichloroethane. Benzethonium and benzalkonium are extracted quantitatively after the formation of a new type of ion-associate with BCG and quinine in an aqueous solution at pH 8.2. The ion-associate shows an absorption maximum at 630 nm. Many other quaternary ammonium species and amines do not interfere. The method is applied to a range of pharmaceutical products.  相似文献   
246.
247.
We study 10D super Yang–Mills theory with the gauge groups E 6, E 7 and E 8. We consider the torus/orbifold compactification with magnetic fluxes and Wilson lines. They lead to 4D interesting models with three families of quarks and leptons, whose profiles in extra dimensions are quasi-localized because of magnetic fluxes.  相似文献   
248.
We report a microscopic investigation of multipolar order parameters in the ordered state of NpO2 conducted via 17O NMR on a single crystal. From the angular dependence of hyperfine fields at 17O nuclei, we have obtained clear evidence for the appearance of field-induced antiferro-octupolar as well as field-induced antiferro-dipolar moments below T0 = 26 K. We have also observed oscillatory spin-echo decay, which is well understood in terms of small electric field gradients created by antiferro-quadrupolar ordering. This reveals that the quadrupolar order parameter is directly observable by means of NMR. The present NMR studies provide definitive support for a proposed longitudinal triple-q type octupolar-quadrupolar ordering model for NpO2.  相似文献   
249.
A tris(2,2'-bipyridine)ruthenium(II) derivative having two N-(3-ammoniopropyl)carbamoyl pendant units has been prepared and reacted with cis-PtCl2(DMSO)2 (DMSO = dimethyl sulfoxide) to give a heteronuclear Ru(II)Pt(II) dimer having a cis-Pt(II)Cl2(aliphatic amine)2 unit, [Ru(bpy)2(mu-bridge)PtCl2](PF6)2 (bpy = 2,2'-bipyridine, bridge = 4,4'-bis(N-(3-aminopropyl)carbamoyl)-2,2'-bipyridine). The ESI-TOF mass spectrum of the Ru(II)Pt(II) dimer shows a set of signals corresponding to {[Ru(bpy)2(mu-bridge)PtCl2](PF6)}(+) (m/z 1181.1). The MLCT (metal-to-ligand charge transfer) luminescence intensity is enhanced upon the platination of two amine units, presumably due to the formation of a relatively rigid metallocycle. More interestingly, the luminescence intensity is further enhanced by the complexation of the Ru(II)Pt(II) dimer with either 5'-GMP (guanosine 5'-monophosphate disodium salt) or calf thymus DNA. Visible-light-induced scission of supercoiled pBR322 DNA is found to be efficiently enhanced in the presence of the title Ru(II)Pt(II) dimer.  相似文献   
250.
Adsorption and growth of a C(60) monolayer on a TiO(2)(110)-1 x 2-cross-link structure were investigated by scanning tunneling microscopy (STM). Single C(60) molecules were preferentially anchored at the cross-link site due to interaction with undercoordinated Ti cations, and C(60) rows grew along the troughs between the 1 x 2-added rows. The C(60) monolayer structure is characterized by closely packed (r(C(60)-C(60)) = 1.0 nm) C(60) rows that are paired with every second added row (separation of paired rows is 1.1 nm). By applying a high negative bias voltage (-3.5 V) to an STM tip on the C(60) monolayer, C(60) oligomers were formed accompanied with the contraction of C(60)-C(60) distance along the C(60) row and bright contrast in the STM image.  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