全文获取类型
收费全文 | 33739篇 |
免费 | 5586篇 |
国内免费 | 2539篇 |
专业分类
化学 | 5929篇 |
晶体学 | 223篇 |
力学 | 6925篇 |
综合类 | 561篇 |
数学 | 11026篇 |
物理学 | 17200篇 |
出版年
2024年 | 49篇 |
2023年 | 312篇 |
2022年 | 632篇 |
2021年 | 853篇 |
2020年 | 1052篇 |
2019年 | 883篇 |
2018年 | 851篇 |
2017年 | 1197篇 |
2016年 | 1415篇 |
2015年 | 1051篇 |
2014年 | 1869篇 |
2013年 | 2601篇 |
2012年 | 1907篇 |
2011年 | 2335篇 |
2010年 | 1983篇 |
2009年 | 2332篇 |
2008年 | 2216篇 |
2007年 | 2208篇 |
2006年 | 1931篇 |
2005年 | 1709篇 |
2004年 | 1618篇 |
2003年 | 1342篇 |
2002年 | 1269篇 |
2001年 | 1074篇 |
2000年 | 977篇 |
1999年 | 835篇 |
1998年 | 765篇 |
1997年 | 602篇 |
1996年 | 524篇 |
1995年 | 482篇 |
1994年 | 425篇 |
1993年 | 363篇 |
1992年 | 329篇 |
1991年 | 255篇 |
1990年 | 217篇 |
1989年 | 166篇 |
1988年 | 145篇 |
1987年 | 156篇 |
1986年 | 135篇 |
1985年 | 148篇 |
1984年 | 146篇 |
1983年 | 81篇 |
1982年 | 113篇 |
1981年 | 71篇 |
1980年 | 39篇 |
1979年 | 43篇 |
1978年 | 32篇 |
1977年 | 29篇 |
1976年 | 19篇 |
1973年 | 24篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
141.
Mari Grobbelaar‐Van Dalsen 《Mathematical Methods in the Applied Sciences》2004,27(11):1301-1315
This paper is concerned with well‐posedness results for a mathematical model for the transversal vibrations of a two‐dimensional hybrid elastic structure consisting of a rectangular Reissner–Mindlin plate with a Timoshenko beam attached to its free edge. The model incorporates linear dynamic feedback controls along the interface between the plate and the beam. Classical semigroup methods are employed to show the unique solvability of the coupled initial‐boundary‐value problem. We also show that the energy associated with the system exhibits the property of strong stability. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
142.
In this article we prove the existence of the solution to the mixed problem for Euler–Bernoulli beam equation with memory term. The existence is proved by means of the Faedo–Galerkin method and the exponential decay is obtained by making use of the multiplier technique combined with integral inequalities due to Komornik. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
143.
A hybrid heuristic method for combinatorial optimization problems is proposed that combines different classical techniques such as tree search procedures, bounding schemes and local search. The proposed method enhances the classic beam search approach by applying to each partial solution corresponding to a node selected by the beam, a further test that checks whether the current partial solution is dominated by another partial solution at the same level of the search tree. If this is the case, the latter solution becomes the new current partial solution. This step allows to partially recover from previous wrong decisions of the beam search procedure and can be seen as a local search step on the partial solution. We present here the application to two well known combinatorial optimization problems: the two-machine total completion time flow shop scheduling problem and the uncapacitated p-median location problem. In both cases the method strongly improves the performances with respect to the basic beam search approach and is competitive with the state of the art heuristics. 相似文献
144.
145.
146.
Luis L. Bonilla 《Journal of statistical physics》1987,46(3-4):659-678
A nonlinear Fokker-Planck equation is derived to describe the cooperative behavior of general stochastic systems interacting via mean-field couplings, in the limit of an infinite number of such systems. Disordered systems are also considered. In the weak-noise limit; a general result yields the possibility of having bifurcations from stationary solutions of the nonlinear Fokker-Planck equation into stable time-dependent solutions. The latter are interpreted as non-equilibrium probability distributions (states), and the bifurcations to them as nonequilibrium phase transitions. In the thermodynamic limit, results for three models are given for illustrative purposes. A model of self-synchronization of nonlinear oscillators presents a Hopf bifurcation to a time-periodic probability density, which can be analyzed for any value of the noise. The effects of disorder are illustrated by a simplified version of the Sompolinsky-Zippelius model of spin-glasses. Finally, results for the Fukuyama-Lee-Fisher model of charge-density waves are given. A singular perturbation analysis shows that the depinning transition is a bifurcation problem modified by the disorder noise due to impurities. Far from the bifurcation point, the CDW is either pinned or free, obeying (to leading order) the Grüner-Zawadowki-Chaikin equation. Near the bifurcation, the disorder noise drastically modifies the pattern, giving a quenched average of the CDW current which is constant. Critical exponents are found to depend on the noise, and they are larger than Fisher's values for the two probability distributions considered. 相似文献
147.
Based on the discrete-structural theory of thin plates and shells, a calculation model for thin-walled elements consisting
of a number of rigid anisotropic layers is put forward. It is assumed that the transverse shear and compression stresses are
equal on the interfaces. Elastic slippage is allowed over the interfaces between adjacent layers. The solution to the problem
is obtained in a geometrically nonlinear statement with account of the influence of transverse shear and compression strains.
The stress-strain state of circular two-layer transversely isotropic plates, both without defects and with a local area of
adhesion failure at their center, is investigated numerically and experimentally. It is found that the kinematic and static
contact conditions on the interfaces of layered thin-walled structural members greatly affect the magnitude of stresses and
strains. With the use of three variants of calculation models, in the cases of perfect and weakened contact conditions between
layers, the calculation results for circular plates are compared. It is revealed that the variant suggested in this paper
adequately reflects the behavior of layered thin-walled structural elements under large deformations.
__________
Translated from Mekhanika Kompozitnykh Materialov, Vol. 41, No. 6, pp. 761–772, November–December, 2005. 相似文献
148.
I. Peshko G. Galich M. Lopiychuk A. Khizhnyak V. Nakvasuk 《Optics & Laser Technology》1997,29(4):211-215
A laser system containing four CW Nd:YAG double-rod lasers, transforming optics and a fibre with input-output optics has been designed and investigated. It is shown that reduction of the beam parameter product of the non-Gaussian beams in the image space of the lens has made it possible to collect the emission of four lasers to the same fibre. Independent laser operation has provided the output power control in the range of 10–900 W with a stable light spot size on the input end of the fibre. 相似文献
149.
Biswarup Mukhopadhyaya 《Pramana》1998,51(1-2):181-190
The observable consequences of gauge-mediated supersymmetry breaking (GMSB) are reviewed here. Implications of scenarios both
with a neutralino and a slepton as the next lightest supersymmetric particle (NLSP) are surveyed in relation to hadronic ande
+
e
- colliders. We also discuss the phenomenological consequences of the NLSP decaying slowly, giving rise to delayed events in
the detectors.The importance of distinguishing signals of GMSB models from those of the commonly discussed supergravity-type
theories is emphasized. 相似文献
150.
Mass distributions of fragments in the low-energy fission of nuclei from 187Ir to 213At have been analysed. This analysis has shown that shell effects in symmetric-mode fragment mass yields from the fission of pre-actinide nuclei could be described if one assumes the existence of two strongly deformed neutron shells in the arising fragments with neutron numbers N1 ≈ 52 and N2 ≈ 68. A new method has been proposed for quantitatively describing the mass distributions of the symmetric fission mode for pre-actinides with A ≈ 180–220. 相似文献