全文获取类型
收费全文 | 29870篇 |
免费 | 1025篇 |
国内免费 | 83篇 |
专业分类
化学 | 19632篇 |
晶体学 | 200篇 |
力学 | 634篇 |
数学 | 5338篇 |
物理学 | 5174篇 |
出版年
2023年 | 186篇 |
2022年 | 262篇 |
2021年 | 428篇 |
2020年 | 471篇 |
2019年 | 491篇 |
2018年 | 580篇 |
2017年 | 506篇 |
2016年 | 1075篇 |
2015年 | 862篇 |
2014年 | 905篇 |
2013年 | 1847篇 |
2012年 | 1886篇 |
2011年 | 1982篇 |
2010年 | 1199篇 |
2009年 | 1137篇 |
2008年 | 1733篇 |
2007年 | 1745篇 |
2006年 | 1621篇 |
2005年 | 1439篇 |
2004年 | 1308篇 |
2003年 | 1020篇 |
2002年 | 927篇 |
2001年 | 614篇 |
2000年 | 538篇 |
1999年 | 424篇 |
1998年 | 318篇 |
1997年 | 316篇 |
1996年 | 399篇 |
1995年 | 276篇 |
1994年 | 311篇 |
1993年 | 252篇 |
1992年 | 247篇 |
1991年 | 221篇 |
1990年 | 232篇 |
1989年 | 201篇 |
1988年 | 178篇 |
1987年 | 176篇 |
1986年 | 161篇 |
1985年 | 235篇 |
1984年 | 257篇 |
1983年 | 166篇 |
1982年 | 174篇 |
1981年 | 173篇 |
1980年 | 176篇 |
1979年 | 124篇 |
1978年 | 126篇 |
1977年 | 130篇 |
1976年 | 98篇 |
1975年 | 101篇 |
1973年 | 85篇 |
排序方式: 共有10000条查询结果,搜索用时 203 毫秒
91.
Starting from the assumption that general relativity might be an emergent phenomenon showing up at low energies from an underlying microscopic structure, we reanalyze the stability of a static closed universe filled with radiation. In this scenario, it is sensible to consider the effective general-relativistic configuration as in a thermal contact with an “environment” (the role of the environment can be played, for example, by a higher-dimensional bulk or by the trans-Planckian degrees of freedom). We calculate the free energy at a fixed temperature of this radiation-filled static configuration. Then, by looking at the free energy, we show that the static Einstein configuration is stable under the stated condition. 相似文献
92.
Antonio Tineo 《Journal of Mathematical Analysis and Applications》2003,279(2):365-371
In this paper we use a continuation argument to prove the existence of global attractors for a class of periodic Kolmogorov systems. 相似文献
93.
Juan A. Barceló Jonathan Bennett Alberto Ruiz 《Journal of Fourier Analysis and Applications》2003,9(6):541-562
We study the continuity properties of a projection derived from a recent characterization of Herglotz Wave Functions in the plane. Herglotz Wave Functions are the entire solutions of the Helmholtz equation which have L2-Far-Field-Pattern. The behavior of this projection is reminiscent of the Disc Multiplier Operator on both Lp and mixed Lp-normed spaces. In particular a Kakeya type set plays a central role in our analysis. As a consequence we answer a question posed by Alvarez, Folch-Gabayet and Pérez-Esteva. 相似文献
94.
95.
Antonio Vitolo 《Journal of Differential Equations》2003,194(1):166-184
This paper is concerned with the maximum principle for second-order linear elliptic equations in a wide generality. By means of a geometric condition previously stressed by Berestycki-Nirenberg-Varadhan, Cabré was very able to improve the classical ABP estimate obtaining the maximum principle also in unbounded domains, such as infinite strips and open connected cones with closure different from the whole space. Now we introduce a new geometric condition that extends the result to a more general class of domains including the complements of hypersurfaces, as for instance the cut plane. The methods developed here allow us to deal with complete second-order equations, where the admissible first-order term, forced to be zero in a preceding result with Cafagna, depends on the geometry of the domain. 相似文献
96.
D. Barrios Rolanía G. Lpez Lagomasino E. B. Saff 《Journal of Approximation Theory》2003,124(2):263-281
Using a convergence theorem for Fourier–Padé approximants constructed from orthogonal polynomials on the unit circle, we prove an analogue of Hadamard's theorem for determining the radius of m-meromorphy of a function analytic on the unit disk and apply this to the location of poles of the reciprocal of Szeg
functions. 相似文献
97.
José A. Anquela Teresa Cortés Miguel Gómez-Lozano Mercedes Siles-Molina 《Acta Mathematica Hungarica》2004,103(3):177-196
We investigate the basic properties of the different socles that can be considered in not necessarily semiprime associative
systems. Among other things, we show that the socle defined as the sum of minimal (or minimal and trivial) inner ideals is
always an ideal. When trivial inner ideals are included, this inner socle contains the socles defined in terms of minimal
left or right ideals.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
98.
Deák L. Bottyán L. Major M. Nagy D. L. Spiering H. Szilágyi E. Tanczikó F. 《Hyperfine Interactions》2002,144(1-4):45-52
Hyperfine Interactions - Synchrotron Mössbauer Reflectometry (SMR), the grazing incidence nuclear resonant scattering of synchrotron radiation, can be applied to perform depth-selective phase... 相似文献
99.
We derive the incompressible and compressible k–ε model for locally homogeneous turbulence. The model is rigorously derived on formal mathematical grounds using the MPP modelling technique. This lets us calculate by either analytical or numerical means the closure constants of the model. To cite this article: T. Chacón Rebollo, D. Franco Coronil, C. R. Acad. Sci. Paris, Ser. I 337 (2003). 相似文献
100.
We consider toy cosmological models in which a classical, homogeneous, spinor field provides a dominant or sub-dominant contribution to the energy-momentum tensor of a flat Friedmann-Robertson-Walker universe. We find that, if such a field were to exist, appropriate choices of the spinor self-interaction would generate a rich variety of behaviors, quite different from their widely studied scalar field counterparts. We first discuss solutions that incorporate a stage of cosmic inflation and estimate the primordial spectrum of density perturbations seeded during such a stage. Inflation driven by a spinor field turns out to be unappealing as it leads to a blue spectrum of perturbations and requires considerable fine-tuning of parameters. We next find that, for simple, quartic spinor self-interactions, non-singular cyclic cosmologies exist with reasonable parameter choices. These solutions might eventually be incorporated into a successful past- and future-eternal cosmological model free of singularities. In an Appendix, we discuss the classical treatment of spinors and argue that certain quantum systems might be approximated in terms of such fields. 相似文献