全文获取类型
收费全文 | 278613篇 |
免费 | 3290篇 |
国内免费 | 899篇 |
专业分类
化学 | 130179篇 |
晶体学 | 3878篇 |
力学 | 14375篇 |
综合类 | 3篇 |
数学 | 56125篇 |
物理学 | 78242篇 |
出版年
2020年 | 1857篇 |
2019年 | 1847篇 |
2018年 | 12458篇 |
2017年 | 12312篇 |
2016年 | 9898篇 |
2015年 | 3439篇 |
2014年 | 4218篇 |
2013年 | 9773篇 |
2012年 | 10706篇 |
2011年 | 18522篇 |
2010年 | 11269篇 |
2009年 | 11491篇 |
2008年 | 14404篇 |
2007年 | 16381篇 |
2006年 | 7659篇 |
2005年 | 7957篇 |
2004年 | 7533篇 |
2003年 | 7289篇 |
2002年 | 6225篇 |
2001年 | 6046篇 |
2000年 | 4685篇 |
1999年 | 3512篇 |
1998年 | 3013篇 |
1997年 | 2888篇 |
1996年 | 2909篇 |
1995年 | 2645篇 |
1994年 | 2604篇 |
1993年 | 2589篇 |
1992年 | 2768篇 |
1991年 | 2622篇 |
1990年 | 2574篇 |
1989年 | 2474篇 |
1988年 | 2479篇 |
1987年 | 2460篇 |
1986年 | 2349篇 |
1985年 | 3086篇 |
1984年 | 3137篇 |
1983年 | 2783篇 |
1982年 | 2884篇 |
1981年 | 2718篇 |
1980年 | 2682篇 |
1979年 | 2802篇 |
1978年 | 2849篇 |
1977年 | 2752篇 |
1976年 | 2743篇 |
1975年 | 2646篇 |
1974年 | 2609篇 |
1973年 | 2810篇 |
1972年 | 1763篇 |
1971年 | 1476篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
191.
192.
M Lepère R Gobeille V.Malathy Devi M.A.H Smith B Aoaeh A.W Mantz 《Journal of Molecular Spectroscopy》2004,224(1):7-12
We have analyzed the methyl fluoride RQ(J,0)Q branch lines located near 1475 cm−1 using a simultaneous multi-spectrum fitting technique. In this analysis we have used previously recorded diode-laser data in which we collected many data points covering only one or two Q branch lines in a particular run. The analysis consists of simultaneously fitting 57 spectra collected with numerous pressure and path length conditions for all absorption lines. The data are concatenated to create one continuous spectrum of the Q branch. We have determined the intensity and self-broadened widths at 296 K for 23 RQ(J,0) lines. 相似文献
193.
We investigate the dynamics of the Λ system driven by two resonant laser fields in presence of dissipation for coupling strengths where the rotating‐wave approximation starts to break down. This regime is characterised by Rabi frequencies being approximately equal or smaller than the field frequencies. A systematic procedure to obtain an expansion for the solution of the Bloch evolution equations of the system is presented. The lowest contribution results to be the well‐known rotating‐wave approximation. The method is based on a semi‐classical treatment of the problem, and its predictions are interpreted fully quantum mechanically. The theory is illustrated by a detailed study of the disappearance of coherent population trapping as the intensities of the fields increase. 相似文献
194.
195.
We give necessary and sufficient conditions for an operator on a separable Hilbert space to satisfy the hypercyclicity criterion.
This paper is a part of the second author’s Doctoral thesis, written at Shiraz University under the direction of the first
author. 相似文献
196.
P. R. Latthe P. S. Shinge Bharati V. Badami P. B. Patil S. N. Holihosur 《Journal of Chemical Sciences》2006,118(3):249-256
3-[4-(Azidocarbonyl)]phenylsydnone (2) obtained from 3-(4-hydrazinocarbonyl) phenylsydnone (1) on Curtius rearrangement with alcohols, water and amines afforded the corresponding carbamates (3a-h), 4,4′-(sydnone-3-yl) diphenyl urea (4) and 4-(heterocyclyl)phenyl ureas (5a-l). Compounds (5a-l) on one-pot ring conversion yielded the 1,3,4-oxadiazolin-2-one derivatives (6a-l), which on reaction with N2H4 gave the 4-amino-1,2,4-triazolin-3-ones (7a-l). All these compounds exhibited moderate antimicrobial activity against the few microbes tested. The carbamates have been
found to be more toxic against fourth instar larvae ofAedes aegypti, in particular, then-butyl derivative (3e). 相似文献
197.
J.-C. Thomas L. Achouri J. Äystö R. Béraud B. Blank G. Canchel S. Czajkowski P. Dendooven A. Ensallem J. Giovinazzo N. Guillet J. Honkanen A. Jokinen A. Laird M. Lewitowicz C. Longour F. de Oliveira Santos K. Peräjärvi M. Stanoiu 《The European Physical Journal A - Hadrons and Nuclei》2004,21(3):419-435
198.
Dimitar I. Pushkarov 《Central European Journal of Physics》2004,2(3):420-455
Basic ideas and results which characterize quantum diffusion of defects in quantum crystals like solid helium as a new phenomenon
are presented. Quantum effects in such media lead to a delocalization of point defects (vacancies, impurities etc.) and they
turn into quasiparticles of a new type—defectons, which are characterized not by their position in the crystal lattice but
by their quasimomentum and dispersion law. Defecton-defecton and defecton-phonon scattering are considered and an interpolation
formula for the diffusion coefficient valid in all interesting temperature and concentration regions is presented. A comparison
with the experimental data is made. Some alternative points of view are discussed in detail and the inconsistency of the Kisvarsanyi-Sullivan
theory is shown. 相似文献
199.
Sauer, Shelah, Vapnik and Chervonenkis proved that if a set system on n vertices contains many sets, then the set system has full trace on a large set. Although the restriction on the size of the
groundset cannot be lifted, Frankl and Pach found a trace structure that is guaranteed to occur in uniform set systems even
if we do not bound the size of the groundset. In this note we shall give three sequences of structures such that every set
system consisting of sufficiently many sets contains at least one of these structures with many sets. 相似文献
200.