全文获取类型
收费全文 | 3973篇 |
免费 | 162篇 |
国内免费 | 52篇 |
专业分类
化学 | 2419篇 |
晶体学 | 24篇 |
力学 | 128篇 |
综合类 | 3篇 |
数学 | 876篇 |
物理学 | 737篇 |
出版年
2023年 | 27篇 |
2022年 | 95篇 |
2021年 | 140篇 |
2020年 | 112篇 |
2019年 | 137篇 |
2018年 | 144篇 |
2017年 | 115篇 |
2016年 | 178篇 |
2015年 | 129篇 |
2014年 | 161篇 |
2013年 | 300篇 |
2012年 | 288篇 |
2011年 | 286篇 |
2010年 | 186篇 |
2009年 | 140篇 |
2008年 | 217篇 |
2007年 | 188篇 |
2006年 | 154篇 |
2005年 | 156篇 |
2004年 | 115篇 |
2003年 | 82篇 |
2002年 | 88篇 |
2001年 | 41篇 |
2000年 | 52篇 |
1999年 | 47篇 |
1998年 | 40篇 |
1997年 | 36篇 |
1996年 | 40篇 |
1995年 | 33篇 |
1994年 | 34篇 |
1993年 | 22篇 |
1992年 | 25篇 |
1991年 | 11篇 |
1990年 | 23篇 |
1989年 | 24篇 |
1988年 | 14篇 |
1987年 | 17篇 |
1986年 | 19篇 |
1985年 | 33篇 |
1984年 | 18篇 |
1982年 | 20篇 |
1981年 | 17篇 |
1980年 | 24篇 |
1979年 | 21篇 |
1978年 | 16篇 |
1977年 | 22篇 |
1976年 | 18篇 |
1975年 | 20篇 |
1974年 | 12篇 |
1973年 | 10篇 |
排序方式: 共有4187条查询结果,搜索用时 15 毫秒
1.
Bao Nguyen Xuan Duy Khanh Phan Quoc Tung Nguyen Minh 《Set-Valued and Variational Analysis》2022,30(2):465-486
Set-Valued and Variational Analysis - We aim to establish Karush-Kuhn-Tucker multiplier rules involving higher-order complementarity slackness under Hölder metric subregularity. These rules... 相似文献
2.
Nonlinear Dynamics - Introduction of stiffness nonlinearities to broaden the frequency bandwidth of vibratory energy harvesters has the adverse influence of complicating the response behavior of... 相似文献
3.
4.
As borders between different entities, lines are an important element of natural images. Indeed, the neurons of the mammalian
visual cortex are tuned to respond best to lines of a given orientation. This preferred orientation varies continuously across
most of the cortex, but also has vortex-like singularities known as pinwheels. In attempting to describe such patterns of
orientation preference, we are led to consider underlying rotation symmetries: Oriented segments in natural images tend to
be collinear; neurons are more likely to be connected if their preferred orientations are aligned to their topographic separation.
These are indications of a reduced symmetry requiring joint rotations of both orientation preference and the underlying topography.
This is verified by direct statistical tests in both natural images and in cortical maps. Using the statistics of natural
scenes we construct filters that are best suited to extracting information from such images, and find qualitative similarities
to mammalian vision.
PACS84.35+i 89.70.+c 87.57.Nk 相似文献
5.
Software failures have become the major factor that brings the system down or causes a degradation in the quality of service. For many applications, estimating the software failure rate from a user's perspective helps the development team evaluate the reliability of the software and determine the release time properly. Traditionally, software reliability growth models are applied to system test data with the hope of estimating the software failure rate in the field. Given the aggressive nature by which the software is exercised during system test, as well as unavoidable differences between the test environment and the field environment, the resulting estimate of the failure rate will not typically reflect the user‐perceived failure rate in the field. The goal of this work is to quantify the mismatch between the system test environment and the field environment. A calibration factor is proposed to map the failure rate estimated from the system test data to the failure rate that will be observed in the field. Non‐homogeneous Poisson process models are utilized to estimate the software failure rate in both the system test phase and the field. For projects that have only system test data, use of the calibration factor provides an estimate of the field failure rate that would otherwise be unavailable. For projects that have both system test data and previous field data, the calibration factor can be explicitly evaluated and used to estimate the field failure rate of future releases as their system test data becomes available. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
6.
J. Giroire T. Ha‐Duong V. Moumas 《Mathematical Methods in the Applied Sciences》2005,28(13):1527-1552
This article deals with a boundary value problem for Laplace equation with a non‐linear and non‐local boundary condition. This problem comes from petroleum engineering and is used to obtain an estimation of well productivity. The non‐linear and non‐local boundary condition is written on the well boundary. On the outer reservoir boundaries, we have both Dirichlet and Neumann conditions. In this paper, we prove the existence and uniqueness of a solution to this problem. The existence is proved by Schauder theorem and the uniqueness is obtained under more restricted conditions, when the involved operator is a contraction. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
7.
Pham Huu Anh Ngoc 《Journal of Differential Equations》2007,243(1):101-122
We study stability radii of linear Volterra-Stieltjes equations under multi-perturbations and affine perturbations. A lower and upper bound for the complex stability radius with respect to multi-perturbations are given. Furthermore, in some special cases concerning the structure matrices, the complex stability radius can precisely be computed via the associated transfer functions. Then, the class of positive linear Volterra-Stieltjes equations is studied in detail. It is shown that for this class, complex, real and positive stability radius under multi-perturbations or multi-affine perturbations coincide and can be computed by simple formulae expressed in terms of the system matrices. As direct consequences of the obtained results, we get some results on robust stability of positive linear integro-differential equations and of positive linear functional differential equations. To the best of our knowledge, most of the results of this paper are new. 相似文献
8.
K.E. Lee T.L. Phan N.D. Ha M.H. Phan S.C. Yu C.O. Kim 《Journal of magnetism and magnetic materials》2006
Influences of oxygen-partial pressure and annealing on the electrical and magnetic properties of CoFeAlO thin films were systematically investigated by means of resistivity, permeability, magnetization and ferromagnetic resonance (FMR) measurements. It was found that, with increasing oxygen-partial pressure or under annealing, the electrical resistivity of the film increased and the magnetic softness decreased, which is attributed to the microstructural change of the film. Interestingly, an as-deposited Co45.30Fe20.65Al19.34O14.71 film was found to exhibit an inverted hysteresis loop with negative coercivity, and this peculiar phenomenon disappeared upon effects of oxygen-partial pressure and annealing. It was also found that the as-deposited films owned a narrow FMR line width that increased with increasing oxygen-partial pressure or under annealing. 相似文献
9.
High-frequency characteristics of CoFeVAlONb thin films were studied. A thin film of Co43.47Fe35.30V1.54Al5.55O9.93Nb4.21 is observed to exhibit excellent magnetic properties; magnetic coercivity of 1.24 Oe, uniaxial in-plane anisotropy field of 66.99 Oe, and saturation magnetization of 19.8 kG. The effective permeability of the film is as high as 1089 and is stable up to 1.8 GHz, and with ferromagnetic resonance over 3 GHz. This film also has very high electrical resistivity of about 628 μΩ cm. These superior properties make it ideal for high-frequency magnetic applications. 相似文献