全文获取类型
收费全文 | 2627篇 |
免费 | 74篇 |
国内免费 | 7篇 |
专业分类
化学 | 1964篇 |
晶体学 | 6篇 |
力学 | 49篇 |
数学 | 158篇 |
物理学 | 531篇 |
出版年
2021年 | 28篇 |
2020年 | 44篇 |
2019年 | 21篇 |
2018年 | 20篇 |
2017年 | 19篇 |
2016年 | 42篇 |
2015年 | 55篇 |
2014年 | 62篇 |
2013年 | 97篇 |
2012年 | 100篇 |
2011年 | 113篇 |
2010年 | 65篇 |
2009年 | 79篇 |
2008年 | 95篇 |
2007年 | 100篇 |
2006年 | 108篇 |
2005年 | 99篇 |
2004年 | 92篇 |
2003年 | 72篇 |
2002年 | 76篇 |
2001年 | 85篇 |
2000年 | 81篇 |
1999年 | 47篇 |
1998年 | 41篇 |
1997年 | 33篇 |
1996年 | 49篇 |
1995年 | 30篇 |
1994年 | 50篇 |
1993年 | 27篇 |
1992年 | 42篇 |
1991年 | 33篇 |
1990年 | 33篇 |
1989年 | 30篇 |
1988年 | 26篇 |
1987年 | 35篇 |
1986年 | 27篇 |
1985年 | 34篇 |
1984年 | 27篇 |
1983年 | 30篇 |
1982年 | 36篇 |
1981年 | 23篇 |
1980年 | 20篇 |
1979年 | 23篇 |
1978年 | 23篇 |
1973年 | 21篇 |
1972年 | 20篇 |
1969年 | 20篇 |
1968年 | 22篇 |
1967年 | 28篇 |
1966年 | 21篇 |
排序方式: 共有2708条查询结果,搜索用时 15 毫秒
61.
Werner Hoffmann 《Annals of Global Analysis and Geometry》1994,12(1):19-63
Automorphic forms of arbitrary real weight can be considered as functions on the universal covering group of SL(2, ). In this situation, we prove an invariant form of the Selberg trace formula for Hecke operators. For this purpose, the Fourier transforms of weightet orbital integrals, obtained by J. Arthur, R. Herb and P. Sally, jr., are explicitly calculated. Our formula does not follow from Arthur's invariant trace formula, since the group has infinite centre, and vector-valued automorphic forms with respect to non-congruence lattices are considered. 相似文献
62.
Belz J Cousins RD Diwan MV Eckhause M Ecklund KM Hancock AD Highland VL Hoff C Hoffmann GW Irwin GM Kane JR Kettell SH Klein JR Kuang Y Lang K Martin R May M McDonough J Molzon WR Riley PJ Ritchie JL Schwartz AJ Trandafir A Ware B Welsh RE White SN Witkowski MT Wojcicki SG Worm S 《Physical review letters》1996,76(18):3277-3280
63.
64.
Detlev W. Hoffmann 《Transactions of the American Mathematical Society》1996,348(8):3267-3281
Let and be anisotropic quadratic forms over a field of characteristic not . Their function fields and are said to be equivalent (over ) if and are isotropic. We consider the case where and is divisible by an -fold Pfister form. We determine those forms for which becomes isotropic over if , and provide partial results for . These results imply that if and are equivalent and , then is similar to over . This together with already known results yields that if is of height and degree or , and if , then and are equivalent iff and are isomorphic over .
65.
It is geometrically feasible to insert metal-metal-bonded M(4) tetrahedra and M(6) octahedra into the tetrahedral and octahedral holes, respectively, of the fcc C(60) lattice. The electronic structure of the hypothetical tetrahedral variants C(60)(M(4))(2), M = Rh, Co, is analyzed with approximate molecular orbital methods and band structure calculations. These compounds feature M-M and M-C(60) bonding and a variable degree of electron transfer to or from C(60). The C(60)(M(4))(2) phases should be metallic, but we have no way of predicting if they will be superconducting. A number of discrete molecular tetrahedral cluster compounds which serve as models for the solid state materials are analyzed. There is a clear indication that tetranuclear and even mononuclear Rh, Ir, and Co arene complexes should be relatively unstable. 相似文献
66.
Hoffmann V Uhlemann HJ Prässler F Wetzig K Birus D 《Analytical and bioanalytical chemistry》1996,355(7-8):826-830
A new radio frequency (rf) hardware is developed for glow discharge spectroscopic methods. The resulting features and its capabilities for analytical applications are discussed. The electrical equipment developed allows to work as quickly, stably, reliably and easily as known from the direct current (dc) mode. Moreover, the rf power measurement has been improved. The hardware has been developed, optimised and tested for glow discharge optical emission spectroscopy (GDOES), but nevertheless it is possible to use it for all procedures applying glow discharge sources. 相似文献
67.
We report approximate molecular orbital calculations on the [Ta(5)(NH)(4)Cl(17)](6-) cluster synthesized by Simon and Meyer. The cluster is based on a "flattened" square pyramid of tantalum atoms, basal bridging imides, and terminal chlorides. This cluster was of interest to us due to the unusual presence of imide ligands, the distorted nature of the metal core, and the possible resemblance to B(5)H(9). Our calculations indicate that metal-metal bonding is limited to Ta(apical)-Ta(basal) bonding, with no significant bonding between the basal metal atoms. The imide ligands, which bridge the base of the pyramid, were found to have a significant amount of capping character. The metal-metal bonding orbitals have some unusual features due to the pyramid's distortion. Additionally, the flattened nature of the pyramid leads to an interesting energy ordering of the metal-metal bonding orbitals. 相似文献
68.
The crystallochemistry of and the bonding in the orthorhombic four-connected nets of BaIn(2) (CeCu(2) structure) and of CaPtSn (TiNiSi structure, a derivative of the CeCu(2) structure) are analyzed with approximate molecular orbital calculations. Following the Zintl concept, in BaIn(2) the In(-) ions are isoelectronic with group IV tin and should adopt a four-connected structure. In contrast to alpha-tin, which has a cubic diamond structure, the indium ions in BaIn(2) build up an orthorhombic three-dimensional four-connected net containing distorted tetrahedra and ladder polymers of four-membered rings. In the CeCu(2) structure (space group Imma) two bond angles in these distorted tetrahedra are fixed at 90 degrees. The four-connected net in the CeCu(2) structure is topologically related to the layers in black phosphorus (space group Cmca). In CaPtSn (TiNiSi structure) the orthorhombic four-connected net is formed by (PtSn)(2)(-) ions in an ordered arrangement. Calculations on BaIn(2) and CaPtSn show that the four-connected nets are increasingly stabilized as the valence electron count is increased from 16 to 30 valence electrons per 4 formula units. For more than 30e, the nets are destabilized due to filling of M-E antibonding states. Structural data obtained by precise single crystal investigations for the TiNiSi series CaPdIn (20e), CaPdSn (24e), CaPdSb (28e), and CaAgSb (32e), confirm the results of the extended Hückel calculations. We find an interesting and understandable angular asymmetry of the tetrahedral sites in these ternary compounds. 相似文献
69.
Particulates of platinum group elements (Pt, Rh, Pd, Ir) emitted in automotive catalyst exhaust were measured down to the pg/m(3) level. Samples were taken from a standard type three-way catalyst equipped gasoline engine, running on a computer controlled dynamometer. Particulates in catalyzed car exhaust were sampled fractionated according to size by using the cascade impactor with separate targets mounted underneath each nozzle. The targets, small flat discs made of pure graphite, were subsequently analyzed by ETV-ICP-MS without any preparatory steps. 相似文献
70.
Arisaka K Auerbach LB Axelrod S Belz J Biery KA Buchholz P Chapman MD Cousins RD Diwan MV Eckhause M Ginkel JF Guss C Hancock AD Heinson AP Highland VL Hoffmann GW Horvath J Irwin GM Joyce D Kaarsberg T Kane JR Kenney CJ Kettell SH Kinnison WW Knibbe P Konigsberg J Kuang Y Lang K Lee DM Margulies J Mathiazhagan C McFarlane WK McKee RJ Melese P Milner EC Molzon WR Ouimette DA Riley PJ Ritchie JL Rubin P Sanders GH Schwartz AJ Sivertz M Slater WE Urheim J Vulcan WF Wagner DL Welsh RE Whyley RJ 《Physical review letters》1993,71(24):3910-3913