全文获取类型
收费全文 | 5457篇 |
免费 | 183篇 |
国内免费 | 216篇 |
专业分类
化学 | 85篇 |
晶体学 | 2篇 |
力学 | 266篇 |
综合类 | 30篇 |
数学 | 1208篇 |
物理学 | 281篇 |
综合类 | 3984篇 |
出版年
2024年 | 19篇 |
2023年 | 71篇 |
2022年 | 73篇 |
2021年 | 104篇 |
2020年 | 114篇 |
2019年 | 103篇 |
2018年 | 66篇 |
2017年 | 125篇 |
2016年 | 122篇 |
2015年 | 174篇 |
2014年 | 298篇 |
2013年 | 295篇 |
2012年 | 313篇 |
2011年 | 352篇 |
2010年 | 288篇 |
2009年 | 340篇 |
2008年 | 298篇 |
2007年 | 355篇 |
2006年 | 307篇 |
2005年 | 314篇 |
2004年 | 230篇 |
2003年 | 217篇 |
2002年 | 187篇 |
2001年 | 183篇 |
2000年 | 156篇 |
1999年 | 103篇 |
1998年 | 98篇 |
1997年 | 86篇 |
1996年 | 73篇 |
1995年 | 50篇 |
1994年 | 59篇 |
1993年 | 41篇 |
1992年 | 40篇 |
1991年 | 37篇 |
1990年 | 28篇 |
1989年 | 22篇 |
1988年 | 18篇 |
1987年 | 12篇 |
1986年 | 7篇 |
1984年 | 12篇 |
1983年 | 9篇 |
1982年 | 11篇 |
1981年 | 6篇 |
1980年 | 4篇 |
1979年 | 9篇 |
1978年 | 4篇 |
1977年 | 9篇 |
1976年 | 4篇 |
1975年 | 3篇 |
1973年 | 4篇 |
排序方式: 共有5856条查询结果,搜索用时 468 毫秒
11.
庆元县滑坡等地质灾害是由本地的地理环境和人为因素造成的,根据发生滑坡等地质灾害的背景条件和特点,采取适宜的防治对策和措施,可以避免和减少滑坡等地质灾害的发生,从而减少经济损失以及避免人员伤亡. 相似文献
12.
Abstract. We propose a general approach to deal with nonlinear, nonconvex variational problems based on a reformulation of the problem
resulting in an optimization problem with linear cost functional and convex constraints. As a first step we explicitly explore
these ideas to some one-dimensional variational problems and obtain specific conclusions of an analytical and numerical nature. 相似文献
13.
Hans TRIEBEL 《应用数学学报(英文版)》2004,(4)
The paper deals with multifractal quantities for some types of Radon measures,especiallyself-similar probability measures,and their relations to Besov spaces. 相似文献
14.
Neil S. TrudingerXu-Jia Wang 《Journal of Functional Analysis》2002,193(1):1-23
In this paper, we continue previous investigations into the theory of Hessian measures. We extend our weak continuity result to the case of mixed k-Hessian measures associated with k-tuples of k-convex functions, on domains in Euclidean n-space, k=1,2,…,n. Applications are given to capacity, quasicontinuity, and the Dirichlet problem, with inhomogeneous terms, continuous with respect to capacity or combinations of Dirac measures. 相似文献
15.
An investigation of BELENE Nuclear Power Plant (NPP) free field signal is presented in the current study. An SH wave propagation trough multilayer geological media in the region is considered. An original structural model of the geological column has been developed. The investigated layers are isotropic, with constant depth and skyline parallel. The SH rays are with an arbitrary angle as far as the layers are concerned. The seismic SH waves have been generated by a special detonation device. The main results of the study are graphically illustrated. A comparison between the original BELENE NPP experimental and the numerical surface (free field) signals (obtained by the formulated direct problem) for the investigated geological column has been carried out and its results are hereby shown. 相似文献
16.
A. Budhiraja 《Annales de l'Institut Henri Poincaré (B) Probabilités et Statistiques》2003,39(6):2318-941
In this work we study connections between various asymptotic properties of the nonlinear filter. It is assumed that the signal has a unique invariant probability measure. The key property of interest is expressed in terms of a relationship between the observation σ field and the tail σ field of the signal, in the stationary filtering problem. This property can be viewed as the permissibility of the interchange of the order of the operations of maximum and countable intersection for certain σ-fields. Under suitable conditions, it is shown that the above property is equivalent to various desirable properties of the filter such as
- (a) uniqueness of invariant measure for the signal,
- (b) uniqueness of invariant measure for the pair (signal, filter),
- (c) a finite memory property of the filter,
- (d) a property of finite time dependence between the signal and observation σ fields and
- (e) asymptotic stability of the filter.
17.
What features characterize complex system dynamics? Power laws and scale invariance of fluctuations are often taken as the hallmarks of complexity, drawing on analogies with equilibrium critical phenomena. Here we argue that slow, directed dynamics, during which the system's properties change significantly, is fundamental. The underlying dynamics is related to a slow, decelerating but spasmodic release of an intrinsic strain or tension. Time series of a number of appropriate observables can be analyzed to confirm this effect. The strain arises from local frustration. As the strain is released through “quakes,” some system variable undergoes record statistics with accompanying log‐Poisson statistics for the quake event times. We demonstrate these phenomena via two very different systems: a model of magnetic relaxation in type II superconductors and the Tangled Nature model of evolutionary ecology and show how quantitative indications of aging can be found. © 2004 Wiley Periodicals, Inc. Complexity 10: 49–56, 2004 相似文献
18.
Il Bong Jung Alan Lambert Jan Stochel 《Proceedings of the American Mathematical Society》2004,132(8):2291-2302
The concept of backward extension for subnormal weighted shifts is generalized to arbitrary subnormal operators. Several differences and similarities in these contexts are explored, with emphasis on the structure of the underlying measures.
19.
Andrea Grosso Marco Locatelli Fabio Schoen 《Computational Optimization and Applications》2007,38(3):351-370
In this paper we perform a computational analysis of a population based approach for global optimization, Population Basin
Hopping (PBH), which was proven to be very efficient on very challenging global optimization problems by the authors (see
). The experimental analysis aims at understanding more deeply how the approach works and why it is successful on challenging
problems. 相似文献
20.
The pollution source and pollution state of surface water is respectively assessed with equal-standard-pollution-load index and Nemero index, and the habitans' health is assessed as well by comparison with pre-development of geothermal field. Results show that: 1 ) Three pollutive factors obviously fail to attain the required standards and their order sorted by impact degree is As>F- >S2-. 2) The Nemero index of Donggua cross section of Duilongqu River is 0. 725and the water quality is at mildly-polluted level. 3) In Lhasa River, the Nemero indexes of cross sections affected by geothermal fields are much higher than that of the unaffected one, which shows the present and potential impacts of geothermal development. 4) Much more inhabitants nearby got trichomadesis sickness after geothermal development, which shows that the surface water pollution in this area has threatened the inhabitants' health. In addition, other environmental issues caused by Yangbajing geothermal development are analyzed and some countermeasures are proposed. 相似文献