全文获取类型
收费全文 | 32557篇 |
免费 | 1090篇 |
国内免费 | 242篇 |
专业分类
化学 | 22599篇 |
晶体学 | 223篇 |
力学 | 768篇 |
数学 | 5420篇 |
物理学 | 4879篇 |
出版年
2022年 | 218篇 |
2021年 | 420篇 |
2020年 | 514篇 |
2019年 | 483篇 |
2018年 | 376篇 |
2017年 | 369篇 |
2016年 | 832篇 |
2015年 | 737篇 |
2014年 | 807篇 |
2013年 | 1725篇 |
2012年 | 1866篇 |
2011年 | 2352篇 |
2010年 | 1141篇 |
2009年 | 1004篇 |
2008年 | 2009篇 |
2007年 | 2020篇 |
2006年 | 1996篇 |
2005年 | 1862篇 |
2004年 | 1587篇 |
2003年 | 1382篇 |
2002年 | 1282篇 |
2001年 | 402篇 |
2000年 | 388篇 |
1999年 | 358篇 |
1998年 | 335篇 |
1997年 | 357篇 |
1996年 | 486篇 |
1995年 | 343篇 |
1994年 | 299篇 |
1993年 | 270篇 |
1992年 | 266篇 |
1991年 | 237篇 |
1990年 | 202篇 |
1989年 | 203篇 |
1988年 | 232篇 |
1987年 | 198篇 |
1986年 | 180篇 |
1985年 | 347篇 |
1984年 | 339篇 |
1983年 | 242篇 |
1982年 | 313篇 |
1981年 | 323篇 |
1980年 | 298篇 |
1979年 | 282篇 |
1978年 | 257篇 |
1977年 | 227篇 |
1976年 | 206篇 |
1975年 | 208篇 |
1974年 | 210篇 |
1973年 | 209篇 |
排序方式: 共有10000条查询结果,搜索用时 312 毫秒
201.
Summary In this paper we analize the reversibility of the diffusion property for the solution of certain infinite-dimensional systems of stochastic differential equations. Necessary and sufficient conditions ensuring this reversibility are given. The proofs use the techniques of the stochastic calculus of variations.This work was partly done when the first author was visiting the Centre de Recerca Matemàtica at Barcelona 相似文献
202.
Summary We prove the fundamental lemma for spherical functions with respect to the natural (induction) lifting fromPGL(2) toPGL(3) which appears as the unstable counterpart of the stable symmetric-square lifting fromSL(2) toPGL(3) (see [IV] for an introduction to this project, and [VI] for the final results). Thus spherical functions onPGL(2) andPGL(3) which correspond to each other by satisfying an elementary representation theoretic relation are shown to have matching orbital integrals. The proof of this local statement is based on an application of the global trace formula.Partially supported by NSF grants 相似文献
203.
David J. Aldous 《Probability Theory and Related Fields》1988,77(1):137-145
Summary For a continuous-time finite state Markov process with stationary distribution , it is well-known thatP
i
(X
t
=j)-
j
isO(e
-t
) ast, for a certain . For a stochastically monotone process for which the reversed process is also stochastically monotone, one can obtain bounds valid for allt. Precisely,
exp(-t). The proof exploits duality for stochastically monotone processes.Research supported by National Science Foundation Grant MCS 84-03239 相似文献
204.
David G. Kirkpatrick 《Discrete and Computational Geometry》1988,3(1):267-280
A planar subdivision is the partition of the plane induced by an embedded planar graph. A representation of such a subdivision isordered if, for each vertexv of the associated graphG, the (say) clockwise sequence of edges in the embedding ofG incident withv appears explicitly.The worst-case complexity of establishing order in a planar subdivision, i.e., converting an unordered representation into an ordered one, is shown to be (n + log (G)), wheren is the size (number of vertices) of the underlying graphG and (G) is (essentially) the number of topologically distinct embeddings ofG in the plane.This work was supported by the National Science and Engineering Research Council of Canada under Grant A3583. A preliminary version of this paper appeared in theProceedings of the Third Annual ACM Symposium on Computational Geometry. 相似文献
205.
We continue the rigorous study of the large order behavior of the perturbation series for the 4 model in 4 dimensions started in [1]. In this paper we prove a result announced in [1]. We show that the exact radius of convergence of the Borel transform of the renormalized perturbation series for
4
4
is greater than or equal to the expected value given by the position of the first renormalon [2]. This result holds for any vector (2)2 model withN components, and makes use of the Lipatov bound of [1]. This result is based on a partial resummation of counterterms similar to the one of [3], but in a phase-space analysis of the renormalized series. 相似文献
206.
Gabriel M. Rebeiz Curtis C. Ling David B. Rutledge 《International Journal of Infrared and Millimeter Waves》1989,10(8):931-936
An accurate monolithic power meter has been developed for millimeter-wave applications. The detector is a large-area Bismuth bolometer, integrated on a fused-Quartz substrate. It simply measures the temperature change caused by the absorption of millimeter-wave radiation. The power meter is simple to fabricate, inexpensive, and can be easily calibrated using a low-frequency network. The measured responsivity for a 50 bolometer, with an area of 1×1cm, at a bias of 1V. and a video modulation of 100Hz, is 1mV/W. The noise spectrum exhibits a 1/f rolloff till 1KHz, and is limited by the Johnson noise for higher frequencies. The NEP of the detector is 3WHz–1/2 at a video modulation of 1KHz. It is possible to decrease the current NEP by fabricating bolometers with higher responsivities. Possible application areas are absolute power calibration and localized power density measurements at millimeter and submillimeter wavelengths. 相似文献
207.
Monotone Chemical Reaction Networks 总被引:2,自引:1,他引:2
Patrick De Leenheer David Angeli Eduardo D. Sontag 《Journal of mathematical chemistry》2007,41(3):295-314
We analyze certain chemical reaction networks and show that every solution converges to some steady state. The reaction kinetics
are assumed to be monotone but otherwise arbitrary. When diffusion effects are taken into account, the conclusions remain
unchanged. The main tools used in our analysis come from the theory of monotone dynamical systems. We review some of the features
of this theory and provide a self-contained proof of a particular attractivity result which is used in proving our main result. 相似文献
208.
Heptakis(2,6-di-O-methyl)-β-cyclodextrin interacts with 5,15-diphenylporphine to produce a 2:1 complex in dimethyl sulfoxide. This complex possesses a hydrophobic groove that circumscribes the metal binding site of the porphyrin moiety. 相似文献
209.
Charles Brown R. Harry Cragg Tim J. Miller David O''N. Smith 《Journal of organometallic chemistry》1981,220(3):C25-C26
The application of variable temperature 13C NMR to the study of a series of chlorodialkylaminophenylboranes has enabled G values for the rotational barrier, about the boron---nitrogen bond, to be determined. 相似文献
210.
A diastereoselective [4+2] annulation of vinyl carbodiimides with chiral N-alkyl imines has been developed to access the stereochemically rich tricyclic core of the batzelladine alkaloids. Its application to the asymmetric synthesis of batzelladine D permitted the use of long-range, directed hydrogenation and stereoselective intramolecular iodoamination as additional key steps to establish the remaining stereocenters within the natural product with excellent stereocontrol. 相似文献