全文获取类型
收费全文 | 4189篇 |
免费 | 190篇 |
国内免费 | 27篇 |
专业分类
化学 | 3065篇 |
晶体学 | 22篇 |
力学 | 122篇 |
数学 | 675篇 |
物理学 | 522篇 |
出版年
2023年 | 21篇 |
2022年 | 40篇 |
2021年 | 75篇 |
2020年 | 53篇 |
2019年 | 66篇 |
2018年 | 57篇 |
2017年 | 57篇 |
2016年 | 118篇 |
2015年 | 109篇 |
2014年 | 150篇 |
2013年 | 237篇 |
2012年 | 277篇 |
2011年 | 318篇 |
2010年 | 182篇 |
2009年 | 171篇 |
2008年 | 249篇 |
2007年 | 243篇 |
2006年 | 247篇 |
2005年 | 202篇 |
2004年 | 203篇 |
2003年 | 161篇 |
2002年 | 136篇 |
2001年 | 74篇 |
2000年 | 52篇 |
1999年 | 35篇 |
1998年 | 42篇 |
1997年 | 36篇 |
1996年 | 52篇 |
1995年 | 30篇 |
1994年 | 30篇 |
1993年 | 34篇 |
1992年 | 20篇 |
1991年 | 31篇 |
1990年 | 21篇 |
1989年 | 22篇 |
1988年 | 25篇 |
1986年 | 17篇 |
1985年 | 44篇 |
1984年 | 30篇 |
1983年 | 17篇 |
1982年 | 31篇 |
1981年 | 30篇 |
1980年 | 18篇 |
1979年 | 38篇 |
1978年 | 22篇 |
1977年 | 32篇 |
1976年 | 24篇 |
1975年 | 25篇 |
1974年 | 24篇 |
1973年 | 19篇 |
排序方式: 共有4406条查询结果,搜索用时 15 毫秒
81.
Francis Choucroun 《Geometriae Dedicata》1994,53(1):69-74
Résumé On décrit une bijection canonique qui associe à un bon espace ultramétrique, localement compact, non compact, un arbre pointé par un bout: cet espace s'identifie à l'ensemble des autres bouts.
We describe a canonical bijection, which associates a tree with a chosen end to a nice ultrametric, locally compact, non-compact space: this space is identified with the set of other ends.相似文献
82.
Rafael Abela Christopher Baines Xavier Donath Dierk Herlach David Maden Ivan D. Reid Dieter Renker György Solt Ulrich Zimmermann 《Hyperfine Interactions》1994,87(1):1105-1110
TheSR Facility Instruments presently available at PSI and the envisaged medium- and long-term developments are presented. The plans focus on further upgrades of the existing instruments and the development of new techniques using the very high fluxes becoming available at PSI, in particular the setup of a beamline with a fast kicker for muons on request (MORE) and the development of very low energy muon beams. 相似文献
83.
84.
Michel Josse Xavier Gerbaux Armand Hadni 《International Journal of Infrared and Millimeter Waves》1993,14(7):1381-1387
Conclusion We have presented the possibility to make optical coatings on quartz in the FIR and we have got a transmission coefficient as high as 97% at room temperature. It will rise probably close to 100% at liquid helium temperature where the quartz two-phonon difference processes are frozen. The use of polyethylene or TPX is also possible to make plates and lenses. The reflectivity losses are smaller because the refractive index is much smaller, but they cannot be further reduced by any coating because there is no transparent material with n1.2 in the FIR. These lenses are very useful in the FIR (except around 60 cm–1 if they are made of polyethylene). TPX is quite transparent over the whole FIR range, and also in the visible with nearly the same refractive index as in the FIR. Alignments can be made with visible light, and still work in the FIR. 相似文献
85.
A robust, easy to optimize, and efficient homonuclear correlation NMR experiment for half-integer quadrupolar nuclei in solids is described and has been experimentally tested on anhydrous Na2HPO4-(23Na, S= 3/2 nucleus) and as-synthesized AlPO4-14 (27Al, S= 5/2 nucleus), an aluminophosphate molecular sieve. 相似文献
86.
Nam K Prat-Resina X Garcia-Viloca M Devi-Kesavan LS Gao J 《Journal of the American Chemical Society》2004,126(5):1369-1376
Reactive flux molecular dynamics simulations have been carried out using a combined QM/MM potential to study the dynamics of the nucleophilic substitution reaction of dichloroethane by a carboxylate group in haloalkane dehalogenase and in water. We found that protein dynamics accelerates the reaction rate by a factor of 2 over the uncatalyzed reaction. Compared to the thermodynamic effect in barrier reduction, protein dynamic contribution is relatively small. However, analyses of the friction kernel reveal that the origins of the reaction dynamics in water and in the enzyme are different. In aqueous solution, there is significant electrostatic solvation effect, which is reflected by the slow reorganization relaxation of the solvent. On the other hand, there is no strong electrostatic coupling in the enzyme and the major effect on reaction coordinate motion is intramolecular energy relaxation. 相似文献
87.
Churruca F SanMartin R Carril M Urtiaga MK Solans X Tellitu I Domínguez E 《The Journal of organic chemistry》2005,70(8):3178-3187
Novel dibenzo[a,c]phenanthridines are prepared regioselectively by the application of a straightforward synthetic pathway, starting from new 3,4-diaryl- and 3,4-dihydro-3,4-diarylisoquinolines prepared via Ritter-type heterocyclization and the more classical two-step reductive amination/Bischler-Napieralski cyclization of triarylethanones, respectively. A comparative study of nonphenolic oxidative coupling methodologies provides a highly efficient procedure, based on the hypervalent iodine reagent phenyliodine(III) bis(trifluoroacetate) (PIFA), to accomplish the final coupling step. 相似文献
88.
An activated D-residue of a protected dipeptide when coupled racemizes twice as much as an activated L-residue, which is contrary to the case for couplings of acylamino acids. 相似文献
89.
D'Souza F Chitta R Gadde S Zandler ME Sandanayaka AS Araki Y Ito O 《Chemical communications (Cambridge, England)》2005,(10):1279-1281
A highly stable porphyrin-fullerene conjugate with defined distance and orientation, was formed using a newly developed 'two-point' binding strategy involving axial-coordination and cation-crown ether complexation; photochemical studies performed in benzonitrile revealed efficient charge separation and slow charge-recombination in the supramolecular complex. 相似文献
90.