全文获取类型
收费全文 | 14604篇 |
免费 | 1073篇 |
国内免费 | 1630篇 |
专业分类
化学 | 6326篇 |
晶体学 | 22篇 |
力学 | 716篇 |
综合类 | 160篇 |
数学 | 7942篇 |
物理学 | 2141篇 |
出版年
2024年 | 36篇 |
2023年 | 173篇 |
2022年 | 307篇 |
2021年 | 310篇 |
2020年 | 489篇 |
2019年 | 398篇 |
2018年 | 371篇 |
2017年 | 456篇 |
2016年 | 495篇 |
2015年 | 409篇 |
2014年 | 649篇 |
2013年 | 1123篇 |
2012年 | 606篇 |
2011年 | 745篇 |
2010年 | 681篇 |
2009年 | 869篇 |
2008年 | 912篇 |
2007年 | 925篇 |
2006年 | 860篇 |
2005年 | 820篇 |
2004年 | 700篇 |
2003年 | 662篇 |
2002年 | 505篇 |
2001年 | 450篇 |
2000年 | 428篇 |
1999年 | 392篇 |
1998年 | 378篇 |
1997年 | 345篇 |
1996年 | 265篇 |
1995年 | 210篇 |
1994年 | 176篇 |
1993年 | 152篇 |
1992年 | 136篇 |
1991年 | 137篇 |
1990年 | 94篇 |
1989年 | 75篇 |
1988年 | 78篇 |
1987年 | 47篇 |
1986年 | 48篇 |
1985年 | 58篇 |
1984年 | 49篇 |
1983年 | 26篇 |
1982年 | 46篇 |
1981年 | 45篇 |
1980年 | 37篇 |
1979年 | 44篇 |
1978年 | 32篇 |
1977年 | 17篇 |
1976年 | 17篇 |
1973年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
91.
The authors establish the Hilbertian invariance principle for the empirical process of a stationary Markov process, by extending the forward-backward martingale decomposition of Lyons-Meyer-Zheng to the Hilbert space valued additive functionals associated with general non-reversible Markov processes. 相似文献
92.
Eero Immonen 《Journal of Mathematical Analysis and Applications》2004,300(1):79-101
In this article, we study the effect of the chosen representation of a point value (and point evaluation) on the class of periodic signals realizable using a certain type of infinite-dimensional linear system. By suitably representing the point evaluation at the origin in a Hilbert space, we are able to give a complete characterization of its extensions. These extensions involve a new concept called δ-sequence, the use of which as an observation operator of an infinite-dimensional linear system is studied in this article. In particular, we consider their use in the realization of periodic signals. We also investigate how the use of δ-sequences affects the convergence properties of such realizations; we consider the rate and character of convergence and the removal of the Gibbs phenomenon. As still a further demonstration of the significance of the chosen concept of a point value, we discuss the use of distributional point values in the realization of periodic distributions. The possible applications of this work lie in regulator problems of infinite-dimensional control theory, as is indicated by the well-known internal model principle. 相似文献
93.
Johan van Benthem 《Logica Universalis》2007,1(1):125-138
We prove new Lindstr?m theorems for the basic modal propositional language, and for some related fragments of first-order
logic. We find difficulties with such results for modal languages without a finite-depth property, high-lighting the difference
between abstract model theory for fragments and for extensions of first-order logic. In addition we discuss new connections
with interpolation properties, and the modal invariance theorem.
Mathematics Subject Classification (2000): Primary 03B45; Secondary 03C95 相似文献
94.
本文讨论了在区域提纯过程中,研究液态金属流的表面张力时提出的一个带有非负参数Q的两点边值问题.利用上、下解方法和Schauder不动点定理,证明了当0Q851时,该问题至少有一个解,对已有结果0Q<1进行了重要的改进. 相似文献
95.
96.
Pedro J. Torres 《Journal of Differential Equations》2007,232(1):277-284
In a periodically forced semilinear differential equation with a singular nonlinearity, a weak force condition enables the achievement of new existence criteria through a basic application of Schauder's fixed point theorem. The originality of the arguments relies in that, contrary to the customary situation in the available references, a weak singularity facilitates the arguments of the proofs. 相似文献
97.
C. Scheidenberger K. Beckert P. Beller F. Bosch C. Brandau D. Boutin L. Chen B. Franzke H. Geissel R. Knöbel C. Kozhuharov J. Kurcewicz S. A. Litvinov Yu. A. Litvinov M. Mazzocco G. Münzenberg F. Nolden W. R. Plaß M. Steck B. Sun H. Weick M. Winkler 《Hyperfine Interactions》2006,173(1-3):61-66
One important goal of the ILIMA project at FAIR is the study of masses and decay properties of relativistic isomeric beams
stored and cooled in the planned storage-ring complex. A new scheme is described, where a storage-cooler ring is used for
high-resolution mass separation. Experimental results on the separation of the isobaric pair 140Pr-140Ce are presented.
P. Beller, deceased. 相似文献
98.
The complete proofs of Krein’s theorem on the spectral shift function and the trace formula are given for a pair of self-adjoint
operators such that either (i) their difference is trace-class or (ii) the difference of their resolvents is trace-class.
The proofs, essentially due to Krein, is based on Herglotz’s theorem on the boundary value of the analytic functions whose
imaginary part is non-negative on the upper half plane, and an almost optimal class of functions are obtained for which the
trace formula is valid. Also an alternative method based on Weyl-von Neumann’s theorem for self-adjoint operators, avoiding
the complex function theory and inspired by Voiculescu’s work, is given for the first case. Furthermore, some applications
of the spectral shift function have been discussed. 相似文献
99.
Pure gas sorption and transport properties of polyesters based on bisphenol-A and both pure isophthalic and pure terephthalic acid chloride were obtained for He, N2, O2, CH4, and CO2 at 35°C. The polymers were synthesized in our laboratory and amorphous films were prepared with a specialized solvent casting procedure. The polymer containing m-phenylene groups shows higher permselectivity for most of the gas pairs. The ideal selectivity of O2/N2 was increased by 33% when p-phenylene units were replaced by m-phenylene ones. On the other hand, the polyester containing only p-phenylene groups, shows higher permeability to all the gases studied. The polymer based on pure terephthalic acid chloride has a 75% higher oxygen permeability and a 1.1-fold higher carbon dioxide permeability than the isophthalic acid derivative. The polyester containing meta-phenylene units has lower Tg, higher permselectivity, lower permeability, lower fractional free volume (FFV), and lower d-spacing. The values of FFV, and lower d-spacing. The values of FFV and d-spacing were only slightly different between the two isomers. Moreover, for the sub-Tgγ transition the maximum in tan δ occured at essentially the same temperature (?55°C). The polymer with a higher concentration of p-phenylene units shows somewhat larger area under the γ-peak, indicating slightly more sub-Tg motion. The Distribution of FFV is considered to be the determining factor for the differences in transport properties observed. © 1993 John Wiley & Sons, Inc. 相似文献
100.
Sergio Albeverio Yeneng Sun Jiang-Lun Wu 《Transactions of the American Mathematical Society》2007,359(2):517-527
It is shown that for a large collection of independent martingales, the martingale property is preserved on the empirical processes. Under the assumptions of independence and identical finite-dimensional distributions, it is proved that a large collection of stochastic processes are martingales essentially if and only if the empirical processes are also martingales. These two results have implications on the testability of the martingale property in scientific modeling. Extensions to submartingales and supermartingales are given.