全文获取类型
收费全文 | 127951篇 |
免费 | 5881篇 |
国内免费 | 5058篇 |
专业分类
化学 | 67034篇 |
晶体学 | 1583篇 |
力学 | 7099篇 |
综合类 | 370篇 |
数学 | 20816篇 |
物理学 | 41988篇 |
出版年
2023年 | 774篇 |
2022年 | 1753篇 |
2021年 | 2107篇 |
2020年 | 2370篇 |
2019年 | 2572篇 |
2018年 | 4089篇 |
2017年 | 4259篇 |
2016年 | 4218篇 |
2015年 | 2997篇 |
2014年 | 3978篇 |
2013年 | 5594篇 |
2012年 | 8196篇 |
2011年 | 7692篇 |
2010年 | 6045篇 |
2009年 | 5799篇 |
2008年 | 5038篇 |
2007年 | 4805篇 |
2006年 | 4442篇 |
2005年 | 7788篇 |
2004年 | 6924篇 |
2003年 | 4999篇 |
2002年 | 3325篇 |
2001年 | 2857篇 |
2000年 | 2114篇 |
1999年 | 1815篇 |
1998年 | 1686篇 |
1997年 | 1421篇 |
1996年 | 1369篇 |
1995年 | 1138篇 |
1994年 | 1215篇 |
1993年 | 1122篇 |
1992年 | 1240篇 |
1991年 | 1285篇 |
1990年 | 1260篇 |
1989年 | 1143篇 |
1988年 | 1016篇 |
1987年 | 972篇 |
1986年 | 925篇 |
1985年 | 962篇 |
1984年 | 944篇 |
1983年 | 847篇 |
1982年 | 818篇 |
1979年 | 830篇 |
1978年 | 836篇 |
1977年 | 824篇 |
1976年 | 997篇 |
1975年 | 849篇 |
1974年 | 884篇 |
1973年 | 895篇 |
1972年 | 791篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
171.
Belov V. V. Dobrokhotov S. Yu. Maksimov V. A. 《Theoretical and Mathematical Physics》2003,135(3):765-791
Different versions of the Darboux–Weinstein theorem guarantee the existence of action–angle-type variables and the harmonic-oscillator variables in a neighborhood of isotropic tori in the phase space. The procedure for constructing these variables is reduced to solving a rather complicated system of partial differential equations. We show that this system can be integrated in quadratures, which permits reducing the problem of constructing these variables to solving a system of quadratic equations. We discuss several applications of this purely geometric fact in problems of classical and quantum mechanics. 相似文献
172.
Yu. M. Dyukarev 《Mathematical Notes》2004,75(1-2):66-82
In this paper, we obtain criteria for the indeterminacy of the Stieltjes matrix moment problem. We obtain explicit formulas for Stieltjes parameters and study the multiplicative structure of the resolvent matrix. In the indeterminate case, we study the analytic properties of the resolvent matrix of the moment problem. We describe the set of all matrix functions associated with the indeterminate Stieltjes moment problem in terms of linear fractional transformations over Stieltjes pairs. 相似文献
173.
We consider the one-dimensional steady-state semiconductor deviceequations modelling a pnpn device. There are two relevant scalingsof the equations corresponding to small and large applied voltages.In both scalings, the semiconductor equations can be consideredas singularly perturbed. It turns out that the small-voltagescaling breaks down for current values between two saturationcurrents. In that interval, the large-voltage scaling has tobe employed. For both scalings, we derive the first-order termsof an asymptotic expansion and show that the reduced problemhas a solution. An example verifies that the current-voltagecurves obtained have the expected qualitative structure. 相似文献
174.
Yu. P. Kalmykov 《Radiophysics and Quantum Electronics》1989,32(9):826-835
Radio Engineering and Electronics Institute, Academy of Sciences of the USSR. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 32, No. 9, pp. 1113–1124, September, 1989. 相似文献
175.
S. P. Tretyakova Yu. S. Zamyatnin V. N. Kovantsev Yu. S. Korotkin V. L. Mikheev G. A. Timofeev 《Zeitschrift für Physik A Hadrons and Nuclei》1989,333(4):349-353
The emission of Ne and Mg nuclei was detected in the spontaneous decay of234U with probabilities of, respectively, (3.9 ±1.0) × 10?13 and (2.3 ±0.7) × 10?13 relative toα-decay. The upper limits of this kind of decay for235U and236U have been established. Systematics of half-lives for cluster emission are found to be similar to the Geiger-Nuttall dependence forα-decay. Some evidence for the presence of hindrance to cluster emission from the odd-mass nuclei233U and235U is obtained. 相似文献
176.
Conclusions When formamide was reacted with phosphorous acid and phosphorus trichloride, the formation of iminobis(methylenediphosphonic) acid was detected.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 4, pp. 865–868, April, 1987.The authors wish to express their graditude to Yu. P. Tsentalovich for helping with the NMR spectral analysis. 相似文献
177.
An analytical solution of a linearized problem of the emission of periodic internal waves by part of a plane which oscillates with a small amplitude in an arbitrary direction in a viscous exponentially stratified fluid is constructed. Solutions of the dispersion equation are given for all positions of the emitting surface (arbitrary, vertical, horizontal, and critical when one of the beam propagation directions is collinear with the emitting surface). The possibility of transition to the case of a uniform fluid, which is important for applications, is analyzed. 相似文献
178.
Tor Schoenmeyr David Yu Zhang 《Journal of Algorithms in Cognition, Informatics and Logic》2005,57(2):130-139
The string matching with mismatches problem requires finding the Hamming distance between a pattern P of length m and every length m substring of text T with length n. Fischer and Paterson's FFT-based algorithm solves the problem without error in O(σnlogm), where σ is the size of the alphabet Σ [SIAM–AMS Proc. 7 (1973) 113–125]. However, this in the worst case reduces to O(nmlogm). Atallah, Chyzak and Dumas used the idea of randomly mapping the letters of the alphabet to complex roots of unity to estimate the score vector in time O(nlogm) [Algorithmica 29 (2001) 468–486]. We show that the algorithm's score variance can be substantially lowered by using a bijective mapping, and specifically to zero in the case of binary and ternary alphabets. This result is extended via alphabet remappings to deterministically solve the string matching with mismatches problem with a constant factor of 2 improvement over Fischer–Paterson's method. 相似文献
179.
Basic principles of the generalized lattice model of multicomponent condensed systems are formulated. Short-range parts of interatomic interactions are taken into account by means of the geometric constraints method. Long-range parts of the interactions are taken into account in mean field approximation. The expression for Helmholtz free energy is obtained. A system of integral equations for the equilibrium distributions of components is derived. The asymptotic properties of its solutions are investigated. Moment expansion of interatomic interactions and localization of integral terms in free energy is obtained. A Ginzburg–Landau-like functional of free energy is derived. 相似文献
180.
Compact, time‐harmonic, acoustic sources produce waves that decay too slowly to be square‐integrable on a line away from the sources. We introduce an inner product, arising directly from Green's second theorem, to form a Hilbert space of these waves and present examples of its computation.1 © 2005 Wiley Periodicals, Inc. 相似文献