全文获取类型
收费全文 | 9801篇 |
免费 | 261篇 |
国内免费 | 20篇 |
专业分类
化学 | 5812篇 |
晶体学 | 162篇 |
力学 | 267篇 |
数学 | 733篇 |
物理学 | 3108篇 |
出版年
2023年 | 92篇 |
2022年 | 206篇 |
2021年 | 161篇 |
2020年 | 177篇 |
2019年 | 240篇 |
2018年 | 207篇 |
2017年 | 232篇 |
2016年 | 317篇 |
2015年 | 212篇 |
2014年 | 400篇 |
2013年 | 781篇 |
2012年 | 548篇 |
2011年 | 655篇 |
2010年 | 417篇 |
2009年 | 405篇 |
2008年 | 460篇 |
2007年 | 440篇 |
2006年 | 335篇 |
2005年 | 281篇 |
2004年 | 229篇 |
2003年 | 163篇 |
2002年 | 183篇 |
2001年 | 117篇 |
2000年 | 125篇 |
1999年 | 86篇 |
1998年 | 56篇 |
1997年 | 56篇 |
1996年 | 92篇 |
1995年 | 104篇 |
1994年 | 98篇 |
1993年 | 92篇 |
1992年 | 120篇 |
1991年 | 86篇 |
1990年 | 79篇 |
1989年 | 92篇 |
1988年 | 87篇 |
1987年 | 90篇 |
1986年 | 74篇 |
1985年 | 104篇 |
1984年 | 119篇 |
1983年 | 82篇 |
1982年 | 98篇 |
1981年 | 97篇 |
1980年 | 102篇 |
1979年 | 90篇 |
1978年 | 102篇 |
1977年 | 84篇 |
1976年 | 56篇 |
1975年 | 61篇 |
1974年 | 74篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
Doshi DA Shah PB Singh S Branson ED Malanoski AP Watkins EB Majewski J van Swol F Brinker CJ 《Langmuir : the ACS journal of surfaces and colloids》2005,21(17):7805-7811
Neutron reflectivity (NR) is used to probe the solid, liquid, vapor interface of a porous superhydrophobic (SH) surface submerged in water. A low-temperature, low-pressure technique was used to prepare a rough, highly porous organosilica aerogel-like film. UV/ozone treatments were used to control the surface coverage of hydrophobic organic ligands on the silica framework, allowing the contact angle with water to be continuously varied over the range of 160 degrees (superhydrophobic) to <10 degrees (hydrophilic). NR shows that the superhydrophobic nature of the surface prevents infiltration of water into the porous film. Atomic force microscopy and density functional theory simulations are used in combination to interpret the NR results and help establish the location, width, and nature of the SH film-water interface. 相似文献
62.
Svein G. Dahl Peter A. Kollman Shashidhar N. Rao U. Chandra Singh 《Journal of computer-aided molecular design》1992,6(3):207-222
Summary The side-chain conformations of psychoactive phenothiazine drugs in crystals are different from those of biologically inactive ring sulfoxide metabolites. This study examines the potential energies, molecular conformations and electrostatic potentials in chlorpromazine, levomepromazine (methotrimeprazine), their sulfoxide metabolites and methoxypromazine. The purpose of the study was to examine the significance of the different crystal conformations of active and inactive phenothiazine derivatives, and to determine why phenothiazine drugs lose most of their biological activity by sulfoxidation. Quantum mechanics and molecular mechanics calculations demonstrated that conformations with the side chain folded over the ring structure had lowest potential energy in vacuo, both in the drugs and in the sulfoxide metabolites. In the sulfoxides, side chain conformations corresponding to the crystal structure of chlorpromazine sulfoxide were characterized by stronger negative electrostatic potentials around the ring system than in the parent drugs. This may weaken the electrostatic interaction of sulfoxide metabolites with negatively charged domains in dopamine receptors, and cause the sulfoxides to be virtually inactive in dopamine receptor binding and related pharmacological tests. 相似文献
63.
Vijay Singh 《Tetrahedron letters》2006,47(39):7043-7045
Tributyltin hydride-mediated straightforward synthesis of a new isoxazolo-benzazulene system from the derivatives afforded by the Baylis-Hillman reaction of 3-(2-bromophenyl)-4-isoxazolecarbaldehydes is described. 相似文献
64.
65.
The one-pot cyclocondensation of 2,6-diaminopyrimidin-4-one, an aromatic or aliphatic aldehyde and a beta-ketoester in acetic acid, or dimethyl sulfoxide in the presence of zinc(II) bromide, under thermal conditions provided dihydropyrido[2,3-d]pyrimidin-4(3H)-ones in good yield and with total regiocontrol. 相似文献
66.
67.
68.
B. Brocklehurst R.S. Dixon E.M. Gardy V.J. Lopata M.J. Quinn A. Singh F.P. Sargent 《Chemical physics letters》1974,28(3):361-363
Excited state formation by ion recombination in solutions of fluorene in squalene has been studied by pulse radiolysis at the center of a large electromagnet. The products of the slower part of the ion recombination are affected by an applied magnetic field. The fluorescence yield increases by a factor of about 1.5 whereas the triplet yield decreases. 相似文献
69.
A. S. Paschoa M. Cholewa K. W. Jones N. P. Singh M. E. Wrenn 《Journal of Radioanalytical and Nuclear Chemistry》1987,115(2):231-240
A combination of two techniques, PIXE (particle induced x-ray emission) and RBS (Rutherford backscattering), is proposed as an analytical tool to measure uranium and thorium in environmental and biological samples and in the study of the micro-distribution of uranium is low Z matrices such as biological tissue.Work supported by U.S. Department of Energy Contracts DE-AC02-76CH-00116 (MC, KWJ) and DE-AC02-76EV-00119 (NPS, MEW). One of us (ASP) is grateful to FINEP (Financiadora de Estudos e Projetos) and CNPq (Conselho Nacional de Desenvolvimento Cientifico e Technológico). 相似文献
70.
R. N. Singh S. Sujatha G. K. Mishra 《Journal of Radioanalytical and Nuclear Chemistry》1990,146(6):427-436
The distribution ratios for the extraction of Zr(IV) by TBP and its binary mixtures with DMSO or Py in n-dodecane in the presence of HNO3, and HClO4 have been determined. Based on stoichiometric and slope analysis methods a possible mechanism for the extraction has been proposed. 相似文献