全文获取类型
收费全文 | 2524篇 |
免费 | 63篇 |
国内免费 | 6篇 |
专业分类
化学 | 1865篇 |
晶体学 | 16篇 |
力学 | 49篇 |
数学 | 149篇 |
物理学 | 514篇 |
出版年
2021年 | 19篇 |
2020年 | 40篇 |
2016年 | 35篇 |
2015年 | 46篇 |
2014年 | 56篇 |
2013年 | 84篇 |
2012年 | 92篇 |
2011年 | 95篇 |
2010年 | 60篇 |
2009年 | 72篇 |
2008年 | 90篇 |
2007年 | 89篇 |
2006年 | 102篇 |
2005年 | 91篇 |
2004年 | 82篇 |
2003年 | 65篇 |
2002年 | 76篇 |
2001年 | 84篇 |
2000年 | 81篇 |
1999年 | 45篇 |
1998年 | 41篇 |
1997年 | 33篇 |
1996年 | 50篇 |
1995年 | 32篇 |
1994年 | 50篇 |
1993年 | 28篇 |
1992年 | 46篇 |
1991年 | 35篇 |
1990年 | 33篇 |
1989年 | 30篇 |
1988年 | 27篇 |
1987年 | 35篇 |
1986年 | 29篇 |
1985年 | 35篇 |
1984年 | 29篇 |
1983年 | 31篇 |
1982年 | 36篇 |
1981年 | 24篇 |
1980年 | 20篇 |
1979年 | 24篇 |
1978年 | 25篇 |
1976年 | 21篇 |
1975年 | 18篇 |
1973年 | 21篇 |
1972年 | 21篇 |
1969年 | 20篇 |
1968年 | 22篇 |
1967年 | 28篇 |
1966年 | 21篇 |
1965年 | 18篇 |
排序方式: 共有2593条查询结果,搜索用时 15 毫秒
111.
G. T. Jones R. W. L. Jones B. W. Kennedy D. R. O. Morrison M. M. Mobayyen S. Wainstein M. Aderholz D. Hantke E. Hoffmann U. F. Katz J. Kern N. Schmitz W. Wittek H. P. Borner G. Myatt D. Radojicic S. Burke 《Zeitschrift fur Physik C Particles and Fields》1991,51(2):205-208
Using data obtained with the bubble chamber BEBC at CERN, the inclusivef 2 (1270) meson production invp and \(\bar vp\) charged current reactions is studied. It is found thatf 2 production occurs mainly in events with a hadronic invariant massW?7 GeV. In these events, the averagef 2 multiplicity is about half the average ρO multiplicity, and thex F andp T 2 distributions of thef 2 agree in shape with those of the ρO. The predictions of a semi-empirical model (Wells model) are in accord with the measured multiplicities atW>7 GeV, whereas at lowerW the model predicts too largef 2 multiplicities. 相似文献
112.
113.
The new low-dimensional ternary chalcogenide, Nb(1+x)V(1-x)S(5) (x = 0.18), has been prepared and characterized. This compound crystallizes in the monoclinic space group, C2(2h)-P2(1)/m with two formula units in a cell with dimensions a = 9.881(4) A, b = 3.329(1) A, c = 8.775(3) A, and beta = 114.82(3) degrees. The layer is composed of two unique chains of face-sharing Nb-centered bicapped trigonal prisms and edge-sharing M-centered octahedra (M = Nb or V). The electronic structures of the monomeric basic building units, NbS(8) and VS(6), and hypothetical and real one-, two-, and three-dimensional structures making up the compound are examined to understand the nature of inter- and intrachain interactions and orbital overlapping among metals and sulfur atoms. The electronic structure of Nb(1+x)V(1-x)S(5) is essentially given by superimposing those of the individual chains. V d orbitals are found to be crucial for the one-dimensional metallic conductivity along the chain axis. 相似文献
114.
[reaction: see text] In the presence of nucleophiles, Lewis acid mediated cleavage of alpha-amino ethers derived from quincorine and quincoridine affords a variety of C2-substituted and C6-vinylated 1-azabicyclo[3.2.2]nonanes. These are enantiopure and are formed in S(N)1-like reactions with complete stereocontrol. There is no leakage into 2-Nu en route to product 1-Nu or vice versa. Me(3)SiCN provides new Strecker-type alpha-amino nitriles. In the presence of TTMPP-BF(3).OEt(2), the ketene acetal Me(2)C=C(OMe)OSiMe(3) delivers enantiopure bicyclic beta-amino acid esters. 相似文献
115.
The two new compounds [Fe(tren)]FeSbS4 ( 1 ) (tren = tris(2‐aminoethyl)amine) and [Fe(dien)2]Fe2Sb4S10 ( 2 ) (dien = diethylendiamine) were prepared under solvothermal conditions and represent the first thioantimonates(III) with iron cations integrated into the anionic network. In both compounds Fe3+ is part of a [2FeIII‐2S] cluster which is often found in ferredoxines. In addition, Fe2+ ions are present which are surrounded by the organic ligands. In ( 1 ) the Fe2+ ion is also part of the thioantimonate(III) network whereas in ( 2 ) the Fe2+ ion is isolated. In both compounds the primary SbS3 units are interconnected into one‐dimensional chains. The mixed‐valent character of [Fe(tren)]FeSbS4 was unambiguously determined with Mössbauer spectroscopy. Both compounds exhibit paramagnetic behaviour and for ( 1 ) a deviation from linearity is observed due to a strong zero‐field splitting. Both compounds decompose in one single step. 相似文献
116.
117.
Markus Follmann Nils Griebenow Michael G. Hahn Ingo Hartung Franz‐Josef Mais Joachim Mittendorf Martina Schfer Hartmut Schirok Johannes‐Peter Stasch Friederike Stoll Alexander Straub Peter Jeschke Ralf Nauen Michael Edmund Beck Hans‐Wilhelm Engels Hans‐Georg Pirkl Reinhard Albers Rolf W. Albach Jens Krause Andreas Hoffmann Holger Casselmann Jeff Dormish 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2013,125(36):9503-9503
118.
Nicolas P. Cheval Barbara Hoffmann Anna Dikova Fatih Sirindil Philippe Bertus Aurélien Blanc Jean-Marc Weibel Patrick Pale 《Tetrahedron》2018,74(50):7111-7119
Vinyl nosylates, readily obtained from β-dicarbonyl derivatives, could be efficiently engaged in Sonogashira cross-coupling reactions, either cocatalyzed by copper or silver salts. The para-nitrobenzenesulfonate (nosylate) group allows this coupling to be performed under very mild conditions (room temperature). These new leaving group and mild conditions could be applied to the synthesis of acetylenic coumarinyl derivatives and to the total synthesis of an acetylenic monoterpene natural product, named cleviolide. 相似文献
119.
120.
T. Hoffmann P. Jacob M. Linscheid D. Klockow 《International journal of environmental analytical chemistry》2013,93(1-4):29-37
Abstract An analytical procedure for the sampling and quantitative determination of biogenic hydrocarbons in the atmosphere is presented. The method is based on the adsorptive preconcentration of the hydrocarbons using Tenax TA/Carbopack B filled sampling tubes followed by thermodesorption of the trapped compounds and gas chromatographic analysis. To avoid losses of the biogenic alkenes as a consequence of their reaction with ozone on the adsorbents during the sampling step, an ozone scrubber is used in front of the adsorption tubes. Diurnal variations of the monoterpene- and ozone-concentrations are determined at different heights in and above a forest stand (coniferous and deciduous trees) in the Vosges (Col du Donon, 760 m a.s.l.) in order to elucidate the importance of terpene-oxidation reactions on the formation of peroxidic products in forest air. 相似文献