全文获取类型
收费全文 | 664243篇 |
免费 | 5661篇 |
国内免费 | 1674篇 |
专业分类
化学 | 344351篇 |
晶体学 | 10052篇 |
力学 | 31748篇 |
综合类 | 26篇 |
数学 | 83194篇 |
物理学 | 202207篇 |
出版年
2021年 | 5852篇 |
2020年 | 6485篇 |
2019年 | 7306篇 |
2018年 | 9550篇 |
2017年 | 9746篇 |
2016年 | 13634篇 |
2015年 | 7593篇 |
2014年 | 12652篇 |
2013年 | 29764篇 |
2012年 | 22563篇 |
2011年 | 26962篇 |
2010年 | 20003篇 |
2009年 | 19874篇 |
2008年 | 25247篇 |
2007年 | 24978篇 |
2006年 | 22874篇 |
2005年 | 20525篇 |
2004年 | 18977篇 |
2003年 | 17214篇 |
2002年 | 16946篇 |
2001年 | 18598篇 |
2000年 | 14389篇 |
1999年 | 11135篇 |
1998年 | 9447篇 |
1997年 | 9300篇 |
1996年 | 8712篇 |
1995年 | 7967篇 |
1994年 | 7877篇 |
1993年 | 7509篇 |
1992年 | 8410篇 |
1991年 | 8734篇 |
1990年 | 8437篇 |
1989年 | 8342篇 |
1988年 | 8210篇 |
1987年 | 8057篇 |
1986年 | 7688篇 |
1985年 | 9800篇 |
1984年 | 10137篇 |
1983年 | 8367篇 |
1982年 | 8709篇 |
1981年 | 8298篇 |
1980年 | 7840篇 |
1979年 | 8566篇 |
1978年 | 8817篇 |
1977年 | 8784篇 |
1976年 | 8592篇 |
1975年 | 8144篇 |
1974年 | 7955篇 |
1973年 | 8118篇 |
1972年 | 5849篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
We study oscillation in a gyrotron with allowance for reflections from an output horn. Regions with different system behaviors,
such as stationary oscillation, self-modulation, and complex-dynamics regimes are found in the parameter plane. The scenarios
of appearance of chaotic oscillations are considered. It is shown that they can emerge via either a sequence of period-doubling
bifurcations or destruction of quasiperiodic motion. For chaotic attractors, Lyapunov exponents are calculated and their dimensions
are estimated on the basis of the Kaplan-Yorke formula. The dimension values turn out to be anomalously large, which is stipulated
by the presence of a large number of high-Q eigenmodes in the gyrotron cavity due to operation near the cutoff frequency of
an electrodynamic system.
__________
Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 49, No. 10, pp. 887–899, October 2006. 相似文献
62.
David K Bisset 《国际流体数值方法杂志》2002,39(10):961-977
Turbulent flow simulation methods based on finite differences are attractive for their simplicity, flexibility and efficiency, but not always for accuracy or stability. This paper demonstrates that a good compromise is possible with the advected grid explicit (AGE) method. Starting from the same initial field as a previous spectral DNS, AGE method simulations of a planar turbulent wake were carried out as DNS, and then at three levels of reduced resolution. The latter cases were in a sense large‐eddy simulations (LES), although no specific sub‐grid‐scale model was used. Results for the two DNS methods, including variances and power spectra, were very similar, but the AGE simulation required much less computational effort. Small‐scale information was lost in the reduced resolution runs, but large‐scale mean and instantaneous properties were reproduced quite well, with further large reductions in computational effort. Quality of results becomes more sensitive to the value chosen for one of the AGE method parameters as resolution is reduced, from which it is inferred that the numerical stability procedure controlled by the parameter is acting in part as a sub‐grid‐scale model. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
63.
A. R. Volkov B. V. Shul'gin T. I. Polupanova V. N. Lebedev A. A. Nagornyi V. L. Petrov Yu. F. Kargin 《Journal of Applied Spectroscopy》1991,54(6):585-590
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 54, No. 6, pp. 970–975, June, 1991. 相似文献
64.
65.
The finite-size corrections, central chargesc, and scaling dimensionsx of tricritical hard squares and critical hard hexagons are calculated analytically. This is achieved by solving the special functional equation or inversion identity satisfied by the commuting row transfer matrices of these lattice models at criticality. The results are expressed in terms of Rogers dilogarithms. For tricritical hard squares we obtainc=7/10,x=3/40, 1/5, 7/8, 6/5 and for hard hexagons we obtainc=4/5,x=2/15, 4/5, 17/15, 4/3, 9/5, in accord with the predictions of conformal and modular invariance. 相似文献
66.
Exact closed-form solutions are exhibited for the Hopf equation for stationary incompressible 3D Navier-Stokes flow, for the cases of homogeneous forced flow (including a solution with depleted nonlinearity) and inhomogeneous flow with arbitrary boundary conditions. This provides an exact method for computing two- and higher-point moments, given the mean flow. 相似文献
67.
A. A. Slavnov 《Theoretical and Mathematical Physics》1989,79(3):579-587
V. A. Steklov Mathematics Institute, USSR Academy of Sciences. Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 79, No. 3, pp. 347–358, June, 1989. 相似文献
68.
69.
We establish soliton-like asymptotics for finite energy solutions to the Schrödinger equation coupled to a nonrelativistic classical particle. Any solution with initial state close to the solitary manifold converges to a sum of a travelling wave and an outgoing free wave. The convergence holds in global energy norm. The proof uses spectral theory and the symplectic projection onto the solitary manifold in the Hilbert phase space. 相似文献
70.
We demonstrate a method that permits to obtain generalized solutions for some quasilinear equations and systems of hyperbolic
type. The corresponding variational principle is constructed using the theory of equilibrium of a potential in an external
field.
Dedicated to the memory of B. M. Levitan
Supported by RFBR grants Nos. 05-01-00522 and NSh-1551.2003.1, by Program No. 1 of the Branch of Mathematics, Russian Academy
of Sciences, and by INTAS project No. 03-51-6637. 相似文献