全文获取类型
收费全文 | 5062篇 |
免费 | 879篇 |
国内免费 | 835篇 |
专业分类
化学 | 2322篇 |
晶体学 | 42篇 |
力学 | 978篇 |
综合类 | 81篇 |
数学 | 447篇 |
物理学 | 2906篇 |
出版年
2024年 | 7篇 |
2023年 | 55篇 |
2022年 | 137篇 |
2021年 | 149篇 |
2020年 | 146篇 |
2019年 | 140篇 |
2018年 | 177篇 |
2017年 | 193篇 |
2016年 | 254篇 |
2015年 | 215篇 |
2014年 | 299篇 |
2013年 | 464篇 |
2012年 | 305篇 |
2011年 | 329篇 |
2010年 | 271篇 |
2009年 | 298篇 |
2008年 | 313篇 |
2007年 | 333篇 |
2006年 | 307篇 |
2005年 | 285篇 |
2004年 | 266篇 |
2003年 | 223篇 |
2002年 | 226篇 |
2001年 | 175篇 |
2000年 | 168篇 |
1999年 | 173篇 |
1998年 | 144篇 |
1997年 | 121篇 |
1996年 | 88篇 |
1995年 | 94篇 |
1994年 | 89篇 |
1993年 | 53篇 |
1992年 | 46篇 |
1991年 | 43篇 |
1990年 | 24篇 |
1989年 | 33篇 |
1988年 | 20篇 |
1987年 | 17篇 |
1986年 | 9篇 |
1985年 | 15篇 |
1984年 | 9篇 |
1983年 | 4篇 |
1982年 | 16篇 |
1981年 | 8篇 |
1980年 | 4篇 |
1979年 | 10篇 |
1978年 | 10篇 |
1977年 | 2篇 |
1976年 | 3篇 |
1973年 | 2篇 |
排序方式: 共有6776条查询结果,搜索用时 265 毫秒
71.
Chengzhe Zhao Guangfeng Wu Chao Zhou Haidong Yang Huixuan Zhang 《Journal of Polymer Science.Polymer Physics》2006,44(4):696-702
A series of acrylic impact modifiers (AIMs) with different particle sizes ranging from 55.2 to 927.0 nm were synthesized by seeded emulsion polymerization, and the effect of the particle size on the brittle–ductile transition of impact‐modified poly(vinyl chloride) (PVC) was investigated. For each AIM, a series of PVC/AIM blends with compositions of 6, 8, 10, 12, and 15 phr AIM in 100 phr PVC were prepared, and the Izod impact strengths of these blends were tested at 23 °C. For AIMs with particle sizes of 55.2, 59.8, 125.2, 243.2, and 341.1 nm, the blends fractured in the brittle mode when the concentration of AIM was lower than 10 phr, whereas the blends showed ductile fracture when the AIM concentration reached 10 phr. It was concluded that the brittle–ductile transition of the PVC/AIM blends was independent of the particle size in the range of 55.2–341.1 nm. When the particle size was greater than 341.1 nm, however, the brittle–ductile transition shifted to a higher AIM concentration with an increase in the particle size. Furthermore, the critical interparticle distance was found not to be the criterion of the brittle–ductile transition for the PVC/AIM blends. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 696–702, 2006 相似文献
72.
A new analytical method of designing two-aspherical-mirror anastigmats was developed and applied to searching solution groups
of soft X-ray microscopes of a large misalignment tolerance. The two-mirror anastigmat configurations were expressed by a
practical variable related to pupil obstruction limiting the system throughput. Axial coma and other aberrations caused by
a slight decenter of the system were then formulated to represent sensitivity to misalignment. These formulations enabled
a global survey of solution groups as demonstrated by a designing example of soft X-ray microscopes with a magnification m = −1/50, which resulted in four solutions more insensitive to misalignment than a standard Schwarzschild optics in the soft
X-ray region. Some solutions were also found to have much larger fields of view suitable for high resolution imaging as confirmed
by computer ray tracing. 相似文献
73.
74.
The problem considered is that of determining the shape of aplane acoustically sound-soft obstacle from the knowledge ofthe far-field pattern for one time-harmonic incident field.An iterative procedure is proposed based on two boundary integralsrepresenting the incident field and the far-field pattern, respectively.Numerical examples are included which show that the proceduregives accurate numerical approximations in relatively few iterations. 相似文献
75.
合肥同步辐射软X射线显微术研究 总被引:1,自引:0,他引:1
合肥国家同步辐射实验室首期建设的光束线之一用于软X射线显微成像研究。实验站现已装置初型的扫描透射X射线显微镜,并正在进行亲一代的扫描显微建设,同时还使同步辐射光进行接触软X射线呈微成像研究,并对选取的一些生物样品进行了成像试验。本文介绍了合肥同步辐射光源上软X射线显微术实验线站的建设及完成的一些实验结果。 相似文献
76.
叙述一种新的光电复合测量技术,它集CCD摄像显示,微机信息采集与处理,光不投影放大,显微镜目视判读为一体,可对微粒大小及其空间分布实行多通道测量,观察和分析。 相似文献
77.
Consider a sequenceF
1,F
2,... of i.i.d. random transformations from a countable setV toV. Such a sequence describes a discrete-time stochastic flow onV, in which the position at timen of a particle that started at sitex isM
n(x), whereM
n
=F
n
F
n–1
F
1. We give conditions on the law ofF
1 for the sequence (M
n) to be tight, and describe the possible limiting law. an example called the block charge model is introduced. The results can be formulated as a statement about the convergence in distribution of products of infinite-dimensional random stochastic matrices. In practical terms, they describe the possible equilibria for random motions of systems of particles on a countable set, without births or deaths, where each site may be occupied by any number of particles, and all particles at a particular site move together. 相似文献
78.
P. Calderoni A. Pellegrinotti E. Presutti M. E. Vares 《Journal of statistical physics》1989,55(3-4):523-577
We consider a system of spins which have values ±1 and evolve according to a jump Markov process whose generator is the sum of two generators, one describing a spin-flipGlauber process, the other aKawasaki (stirring) evolution. It was proven elsewhere that if the Kawasaki dynamics is speeded up by a factor –2, then, in the limit 0 (continuum limit), propagation of chaos holds and the local magnetization solves a reaction-diffusion equation. We choose the parameters of the Glauber interaction so that the potential of the reaction term in the reaction-diffusion equation is a double-well potential with quartic maximum at the origin. We assume further that for each the system is in a finite interval ofZ with –1 sites and periodic boundary conditions. We specify the initial measure as the product measure with 0 spin average, thus obtaining, in the continuum limit, a constant magnetic profile equal to 0, which is a stationary unstable solution to the reaction-diffusion equation. We prove that at times of the order –1/2 propagation of chaos does not hold any more and, in the limit as 0, the state becomes a nontrivial superposition of Bernoulli measures with parameters corresponding to the minima of the reaction potential. The coefficients of such a superposition depend on time (on the scale –1/2) and at large times (on this scale) the coefficient of the term corresponding to the initial magnetization vanishes (transient bimodality). This differs from what was observed by De Masi, Presutti, and Vares, who considered a reaction potential with quadratic maximum and no bimodal effect was seen, as predicted by Broggi, Lugiato, and Colombo. 相似文献
79.
80.