全文获取类型
收费全文 | 2174篇 |
免费 | 260篇 |
国内免费 | 253篇 |
专业分类
化学 | 250篇 |
晶体学 | 9篇 |
力学 | 222篇 |
综合类 | 6篇 |
数学 | 1461篇 |
物理学 | 739篇 |
出版年
2024年 | 17篇 |
2023年 | 38篇 |
2022年 | 65篇 |
2021年 | 53篇 |
2020年 | 46篇 |
2019年 | 74篇 |
2018年 | 74篇 |
2017年 | 71篇 |
2016年 | 98篇 |
2015年 | 70篇 |
2014年 | 126篇 |
2013年 | 221篇 |
2012年 | 145篇 |
2011年 | 164篇 |
2010年 | 112篇 |
2009年 | 207篇 |
2008年 | 163篇 |
2007年 | 140篇 |
2006年 | 95篇 |
2005年 | 79篇 |
2004年 | 59篇 |
2003年 | 75篇 |
2002年 | 66篇 |
2001年 | 53篇 |
2000年 | 58篇 |
1999年 | 39篇 |
1998年 | 36篇 |
1997年 | 41篇 |
1996年 | 25篇 |
1995年 | 20篇 |
1994年 | 26篇 |
1993年 | 18篇 |
1992年 | 11篇 |
1991年 | 7篇 |
1990年 | 10篇 |
1989年 | 8篇 |
1988年 | 9篇 |
1987年 | 4篇 |
1986年 | 5篇 |
1985年 | 7篇 |
1984年 | 10篇 |
1983年 | 5篇 |
1982年 | 9篇 |
1981年 | 7篇 |
1980年 | 4篇 |
1979年 | 4篇 |
1978年 | 4篇 |
1977年 | 3篇 |
1976年 | 2篇 |
1973年 | 2篇 |
排序方式: 共有2687条查询结果,搜索用时 31 毫秒
51.
A fundamentally new recognition method of bio-objects (e.g., cancer cells as the most important case of them) that escape the immune system supervision control is suggested. It is proposed to use a unified complex consisting of several molecular groups (e.g., antibodies or their fragments) bound with each other. Binding targets are localized on the surface of this bio-object. The choice of the targets is determined by antigen profiling being expressed on the surface of these bio-objects. The recognition efficiency appears to be notably higher than in a situation when molecular groups do not form a unified complex and act separately. 相似文献
52.
Hybrid systems with memory are dynamical systems exhibiting both delayed and hybrid dynamics. Such systems can be described by hybrid functional inclusions. Classical invariance principles play an instrumental role in proving stability and convergence of dynamical systems. Invariance principles for general hybrid systems with delays, however, remain an open topic. In this paper, we prove invariance principles for hybrid systems with memory, using both Lyapunov–Razumikhin function and Lyapunov–Krasovskii functional methods. These invariance principles are then applied to derive two stability results as corollaries. 相似文献
53.
An investigation into the bulk properties, elastic properties and Debye temperature under pressure, and deformation mode under tension of Al8Cu4Y and Al8Cr4Y compounds was investigated by using first principles calculations based on density functional theory. The calculated lattice constants for the ternary compounds (Al8Cu4Y and Al8Cr4Y) are in good agreement with the experimental data. It can be seen from interatomic distances that the bonding between Al1 atom and Cr, Y, and Al2 atoms in Al8Cr4Y are stronger than Al8Cu4Y. The results of cohesive energy show that Al8Cr4Y should be easier to be formed and much stronger chemical bonds than Al8Cu4Y. The bulk modulus B, shear modulus G, Young's modulus E and Poisson's ratio ν can be obtained by using the Voigt–Reuss–Hill averaging scheme. From the results of elastic properties, Al8Cr4Y has the stronger mechanical behavior than Al8Cu4Y. Our calculations also show that pressure has a greater effect on mechanical behavior for both compounds. The ideal tensile strength are obtained by stress-strain relationships under [001](001) uniaxial tensile deformation, which are 15.4 and 23.4 GPa for Al8Cu4Y and Al8Cr4Y, respectively. The total and partial density of states and electron charge density under uniaxial tensile deformations for Al8Cu4Y and Al8Cr4Y compounds are also calculated and discussed in this work. 相似文献
54.
本文基于第一性原理方法研究了Y,Zr,Nb在Sn位掺杂SnO_2的键长变化、稳定性、能带结构以及态密度.结果表明:Y,Zr,Nb在Sn位掺杂SnO_2使附近的键长发生改变,改变量最大是Y掺杂SnO_2体系;掺杂体系的杂质替换能都为负值,表明体系为稳定结构;掺杂使SnO_2能级增多,能较好的调节带隙值;而Y掺杂SnO_2体系价带顶端有一条能级越过了费米线表明该体系呈现出半导体的特征;同时,Y,Zr,Nb掺杂SnO_2使导带底端的能级出现分离;在低能区的态密度仍主要由Sn、O的s轨道贡献;在高能区态密度的掺杂体系出现sp杂化的现象; Zr掺杂SnO_2的态密度能量向低能区移动. 相似文献
55.
In this paper we investigate maximum principles for functionals defined on solutions to special partial diff'erential equations of elliptic type, extending results by Payne and Philippin. We apply such maximum principles to investigate one overdetermined problem. 相似文献
56.
In this paper, we study the Kirchhoff type problem with critical growth. By using the variational method, the existence and multiplicity of solutions are obtained. 相似文献
57.
Asher Yahalom 《Physics letters. A》2013,377(31-33):1898-1904
It is shown that an Aharonov–Bohm (AB) effect exists in magnetohydrodynamics (MHD). This effect is best described in terms of the MHD variational variables (Kats, 2004; Yahalom and Lynden-Bell, 2008; Yahalom, 2010) [1], [10], [12]. If a MHD flow has a non-trivial topology some of the functions appearing in the MHD Lagrangian are non-single-valued. These functions have properties similar to the phases in the AB celebrated effect (Aharonov and Bohm, 1959; van Oudenaarden et al., 1998) [2], [3]. While the manifestation of the quantum AB effect is in interference fringe patterns (Tonomura et al., 1982) [4], the manifestation of the MHD Aharonov–Bohm effects are through new dynamical conservation laws. 相似文献
58.
In this paper, we mainly explore the phenomenon of concentration of homoclinic solutions for a class of nonperiodic fourth-order equations with sublinear indefinite nonlinearities. The proof is based on variational methods. 相似文献
59.
In this paper, we study the following Klein–Gordon–Maxwell system Using variational methods, we obtain the existence of ground state solutions under some appropriate assumptions on and . 相似文献
60.
ABSTRACTIn this paper, we investigate the problem of finding a common solution to a fixed point problem involving demi-contractive operator and a variational inequality with monotone and Lipschitz continuous mapping in real Hilbert spaces. Inspired by the projection and contraction method and the hybrid descent approximation method, a new and efficient iterative method for solving the problem is introduced. Strong convergence theorem of the proposed method is established under standard and mild conditions. Our scheme generalizes and extends some of the existing results in the literature, and moreover, its computational effort is less per each iteration compared with related works. 相似文献