全文获取类型
收费全文 | 4620篇 |
免费 | 560篇 |
国内免费 | 433篇 |
专业分类
化学 | 446篇 |
晶体学 | 8篇 |
力学 | 480篇 |
综合类 | 131篇 |
数学 | 3747篇 |
物理学 | 801篇 |
出版年
2024年 | 10篇 |
2023年 | 56篇 |
2022年 | 69篇 |
2021年 | 105篇 |
2020年 | 145篇 |
2019年 | 156篇 |
2018年 | 159篇 |
2017年 | 207篇 |
2016年 | 210篇 |
2015年 | 125篇 |
2014年 | 217篇 |
2013年 | 511篇 |
2012年 | 226篇 |
2011年 | 225篇 |
2010年 | 198篇 |
2009年 | 242篇 |
2008年 | 287篇 |
2007年 | 281篇 |
2006年 | 250篇 |
2005年 | 253篇 |
2004年 | 205篇 |
2003年 | 192篇 |
2002年 | 218篇 |
2001年 | 162篇 |
2000年 | 141篇 |
1999年 | 122篇 |
1998年 | 103篇 |
1997年 | 105篇 |
1996年 | 71篇 |
1995年 | 68篇 |
1994年 | 52篇 |
1993年 | 39篇 |
1992年 | 26篇 |
1991年 | 21篇 |
1990年 | 19篇 |
1989年 | 21篇 |
1988年 | 11篇 |
1987年 | 14篇 |
1986年 | 3篇 |
1985年 | 19篇 |
1984年 | 8篇 |
1983年 | 7篇 |
1982年 | 4篇 |
1981年 | 7篇 |
1980年 | 9篇 |
1979年 | 7篇 |
1978年 | 9篇 |
1977年 | 9篇 |
1976年 | 3篇 |
1936年 | 2篇 |
排序方式: 共有5613条查询结果,搜索用时 0 毫秒
81.
82.
The inverse problem of determining 2D spatial part of integral member kernel in integro‐differential wave equation is considered. It is supposed that the unknown function is a trigonometric polynomial with respect to the spatial variable y with coefficients continuous with respect to the variable x. Herein, the direct problem is represented by the initial‐boundary value problem for the half‐space x>0 with the zero initial Cauchy data and Neumann boundary condition as Dirac delta function concentrated on the boundary of the domain . Local existence and uniqueness theorem for the solution to the inverse problem is obtained. 相似文献
83.
84.
85.
Nikolay K. Vitanov Zlatinka I. Dimitrova Kaloyan N. Vitanov 《Entropy (Basel, Switzerland)》2021,23(1)
The goal of this article is to discuss the Simple Equations Method (SEsM) for obtaining exact solutions of nonlinear partial differential equations and to show that several well-known methods for obtaining exact solutions of such equations are connected to SEsM. In more detail, we show that the Hirota method is connected to a particular case of SEsM for a specific form of the function from Step 2 of SEsM and for simple equations of the kinds of differential equations for exponential functions. We illustrate this particular case of SEsM by obtaining the three- soliton solution of the Korteweg-de Vries equation, two-soliton solution of the nonlinear Schrödinger equation, and the soliton solution of the Ishimori equation for the spin dynamics of ferromagnetic materials. Then we show that a particular case of SEsM can be used in order to reproduce the methodology of the inverse scattering transform method for the case of the Burgers equation and Korteweg-de Vries equation. This particular case is connected to use of a specific case of Step 2 of SEsM. This step is connected to: (i) representation of the solution of the solved nonlinear partial differential equation as expansion as power series containing powers of a “small” parameter ; (ii) solving the differential equations arising from this representation by means of Fourier series, and (iii) transition from the obtained solution for small values of to solution for arbitrary finite values of . Finally, we show that the much-used homogeneous balance method, extended homogeneous balance method, auxiliary equation method, Jacobi elliptic function expansion method, F-expansion method, modified simple equation method, trial function method and first integral method are connected to particular cases of SEsM. 相似文献
86.
87.
Nadica Mihajlović 《代数通讯》2020,48(4):1803-1818
AbstractIn this paper, we have focused our study on the acute perturbation of the group inverse for the elements of Banach algebra with respect to the spectral radius. We also give perturbation analysis for the core inverse in C*- algebra. The perturbation bounds for the core inverse under some conditions are presented. Additionally, this paper extends the results obtained in [11, 14]. 相似文献
88.
For detailed study of complex chemical reactions mechanisms experiment is conducted for selected private reactions. This causes a problem of kinetic parameters getting—the same set of rate constants must describe both public and private reaction stages, and also a general mechanism. In this paper, solution of this problem for a reaction of olefins hydroalumination is proposed. To optimize the computational process a methodology of parallelization is elaborated. On the base of parallel computations, a kinetic model for the reaction assigned is constructed, and on its base, the physical and chemical conclusions about reaction mechanism are done. 相似文献
89.
CAO Rui-Fen WU Yi-Can PEI Xi JING Jia LI Guo-Li CHENG Meng-Yun LI Gui HU Li-Qin 《中国物理C(英文版)》2011,35(3):313-317
The multi-objective optimization of inverse planning based on the Pareto solution set, according to the multi-objective character of inverse planning in accurate radiotherapy, was studied in this paper. Firstly,the clinical requirements of a treatment plan were transformed into a multi-objective optimization problem with multiple constraints. Then, the fast and elitist multi-objective Non-dominated Sorting Genetic Algorithm (NSGA-Ⅱ)was introduced to optimize the problem. A clinical example was tested using this method. The results show that an obtained set of non-dominated solutions were uniformly distributed and the corresponding dose distribution of each solution not only approached the expected dose distribution, but also met the dosevolume constraints. It was indicated that the clinical requirements were better satisfied using the method and the planner could select the optimal treatment plan from the non-dominated solution set. 相似文献
90.
In this paper, we establish uniform-in-bandwidth limit laws of the logarithm for nonparametric Inverse Probability of Censoring
Weighted (I.P.C.W.) estimators of the multivariate regression function under random censorship. A similar result is deduced
for estimators of the conditional distribution function. The uniform-in-bandwidth consistency for estimators of the conditional
density and the conditional hazard rate functions are also derived from our main result. Moreover, the logarithm laws we establish
are shown to yield almost sure simultaneous asymptotic confidence bands for the functions we consider. Examples of confidence
bands obtained from simulated data are displayed.
相似文献