全文获取类型
收费全文 | 2660篇 |
免费 | 75篇 |
国内免费 | 14篇 |
专业分类
化学 | 1778篇 |
晶体学 | 31篇 |
力学 | 78篇 |
数学 | 409篇 |
物理学 | 453篇 |
出版年
2023年 | 13篇 |
2022年 | 70篇 |
2021年 | 71篇 |
2020年 | 55篇 |
2019年 | 68篇 |
2018年 | 47篇 |
2017年 | 42篇 |
2016年 | 93篇 |
2015年 | 84篇 |
2014年 | 88篇 |
2013年 | 132篇 |
2012年 | 173篇 |
2011年 | 196篇 |
2010年 | 130篇 |
2009年 | 111篇 |
2008年 | 180篇 |
2007年 | 167篇 |
2006年 | 135篇 |
2005年 | 143篇 |
2004年 | 122篇 |
2003年 | 106篇 |
2002年 | 92篇 |
2001年 | 34篇 |
2000年 | 40篇 |
1999年 | 31篇 |
1998年 | 19篇 |
1997年 | 22篇 |
1996年 | 22篇 |
1995年 | 18篇 |
1994年 | 15篇 |
1993年 | 15篇 |
1992年 | 14篇 |
1991年 | 13篇 |
1990年 | 9篇 |
1989年 | 6篇 |
1988年 | 15篇 |
1987年 | 9篇 |
1986年 | 4篇 |
1985年 | 14篇 |
1984年 | 9篇 |
1983年 | 16篇 |
1982年 | 14篇 |
1981年 | 15篇 |
1980年 | 12篇 |
1979年 | 7篇 |
1978年 | 7篇 |
1976年 | 4篇 |
1974年 | 3篇 |
1973年 | 4篇 |
1960年 | 5篇 |
排序方式: 共有2749条查询结果,搜索用时 0 毫秒
1.
2.
3.
K.M.J. Rocha R.G. Leitão E.G. Oliveira-Barros M.A. Oliveira C.G.L. Canellas M.J. Anjos L.E. Nasciutti R.T. Lopes 《X射线光谱测定》2019,48(5):476-481
Prostate cancer is a highly prevalent disease and ranks second among malignant neoplasms that affect men around the world, behind lung cancer alone. Trace elements are very important and are involved in many cellular processes. The X-ray microfluorescence technique is an advanced tool of high spatial resolution, sensitivity, multielemental analysis, and nondestructiveness for trace element study. This study aimed to investigate the elemental distribution in spheroids obtained through the following human prostate cell lines using synchrotron X-ray microfluorescence: tumor cell line androgen independent (DU145), tumor cell line androgen dependent (LNCaP), and normal cell line (RWPE-1). The measurements were performed with a standard geometry of 45° of incidence, excited by a white beam using a pixel of 25 μm and an acquisition time of 300 ms/pixel at the X-ray fluorescence beamline at the Synchrotron Light National Laboratory (Campinas, Brazil). The synchrotron X-ray microfluorescence results showed differences between groups in all elements analyzed and suggested that further studies should be performed to understand the relationship of these trace elements with the progression and development of the disease. 相似文献
4.
We investigate heteroclinic orbits between equilibria and rotating waves for scalar semilinear parabolic reaction-advection-diffusion equations with periodic boundary conditions. Using zero number properties of the solutions and the phase shift equivariance of the equation, we establish a necessary and sufficient condition for the existence of a heteroclinic connection between any pair of hyperbolic equilibria or rotating waves. 相似文献
5.
Mauro Picone 《Rendiconti del Circolo Matematico di Palermo》1997,46(1):437-455
[Estratto da una lettera al Prof. G. Bagnera] 相似文献
6.
7.
We consider the generalization of the classical P||Cmax problem (assign n jobs to m identical parallel processors by minimizing the makespan) arising when the number of jobs that can be assigned to each processor cannot exceed a given integer k. The problem is strongly NP-hard for any fixed k > 2. We briefly survey lower and upper bounds from the literature. We introduce greedy heuristics, local search and a scatter search approach. The effectiveness of these approaches is evaluated through extensive computational comparison with a depth-first branch-and-bound algorithm that includes new lower bounds and dominance criteria. 相似文献
8.
Some authors claim that reporting the best result obtained by a stochastic algorithm in a number of runs is more meaningful
than reporting some central statistic. In this short note, we analyze and refute the main argument brought in favor of this
statement. 相似文献
9.
Humberto César Chaves Fernandes Arthur Rodrigo Barros da Rocha 《International Journal of Infrared and Millimeter Waves》2003,24(7):1171-1176
The use of photonic materials has been used in the theory of optical waves. The PBG (Photonic Band Gap) theory and material, was developed recently for optical frequencies and can be easily applied to millimeter waves, microwaves and planar antenna frequencies. The presence of photonic materials as substrate in antennas has some good characteristics such as, supression of light spontaneous emission and suppression of surface waves, allowing the application in planar antenna array. In this work an elaborate analysis using the full wave Transverse Transmission Line - TTL method, that provides efficient and concise results is applied to the planar antennas array with PBG substrate. 相似文献
10.
In this paper we study a Ginzburg–Landau model which describes the behaviour of a superconducting material including thermal effects. We extend the traditional formulation of the problem, by introducing the temperature as an additional state variable. Accordingly, together with the Gor’kov–Eliashberg system, we introduce an evolution equation for the absolute temperature. We examine in detail the case which allows only variations of the concentration of superconducting electrons and of the temperature, neglecting the electromagnetic field. For this problem existence and uniqueness of the solution are shown. Finally we analyze the asymptotic behaviour of the solutions, proving that the system possesses a global attractor. 相似文献