全文获取类型
收费全文 | 15400篇 |
免费 | 2980篇 |
国内免费 | 2208篇 |
专业分类
化学 | 9308篇 |
晶体学 | 258篇 |
力学 | 1924篇 |
综合类 | 154篇 |
数学 | 1728篇 |
物理学 | 7216篇 |
出版年
2024年 | 34篇 |
2023年 | 197篇 |
2022年 | 487篇 |
2021年 | 425篇 |
2020年 | 601篇 |
2019年 | 509篇 |
2018年 | 512篇 |
2017年 | 592篇 |
2016年 | 771篇 |
2015年 | 689篇 |
2014年 | 964篇 |
2013年 | 1527篇 |
2012年 | 1064篇 |
2011年 | 1050篇 |
2010年 | 884篇 |
2009年 | 959篇 |
2008年 | 973篇 |
2007年 | 1068篇 |
2006年 | 914篇 |
2005年 | 802篇 |
2004年 | 761篇 |
2003年 | 698篇 |
2002年 | 521篇 |
2001年 | 500篇 |
2000年 | 490篇 |
1999年 | 383篇 |
1998年 | 383篇 |
1997年 | 283篇 |
1996年 | 269篇 |
1995年 | 223篇 |
1994年 | 214篇 |
1993年 | 156篇 |
1992年 | 137篇 |
1991年 | 92篇 |
1990年 | 72篇 |
1989年 | 68篇 |
1988年 | 60篇 |
1987年 | 42篇 |
1986年 | 42篇 |
1985年 | 35篇 |
1984年 | 33篇 |
1983年 | 8篇 |
1982年 | 24篇 |
1981年 | 9篇 |
1980年 | 14篇 |
1979年 | 14篇 |
1978年 | 9篇 |
1977年 | 4篇 |
1973年 | 5篇 |
1957年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
102.
103.
关于非球面制造技术的看法 总被引:1,自引:1,他引:0
列举了现代诸高科技领域对非球面光学系统的需求实例,如短波光学,空间光学,红外光学,微电子技术等。然后比较讨论了刀口阴影法与数字干涉检验的优缺点。在非球面修磨方法方面,首先肯定了计算机辅助加工是发展的方向,指出其主要优点在于“失误”造成的反复率大大降低。最后对非球面技术提出了总的看法,并对检测方法和修磨方法提出了几个研究课题。 相似文献
104.
Likelihood estimation of soft-core interaction potentials for Gibbsian point patterns 总被引:3,自引:3,他引:0
Yosihiko Ogata Masaharu Tanemura 《Annals of the Institute of Statistical Mathematics》1989,41(3):583-600
The likelihood method is developed for the analysis of socalled regular point patterns. Approximating the normalizing factor of Gibbs canonical distribution, we simultaneously estimate two parameters, one for the scale and the other which measures the softness (or hardness), of repulsive interactions between points. The approximations are useful up to a considerably high density. Some real data are analyzed to illustrate the utility of the parameters for characterizing the regular point pattern. 相似文献
105.
Ph. Choquard B. Piller R. Rentsch P. Vieillefosse 《Journal of statistical physics》1989,55(5-6):1185-1262
We report analytical and numerical studies of surface correlations in finite, homogeneously polarizable, classical Coulomb systems placed in an insulating or conducting environment. Their purpose is to understand the phenomenological, shape-dependent laws of electrostatics, from the point of view of statistical mechanics; we focus on the knowledge of the dielectric susceptibility of the system, a quantity proportional to the equilibrium fluctuation of the system's instantaneous polarization per unit volume. This goal has been achieved for a system in a conducting state. The picture is that the shape-dependent part of the susceptibilities results from the action of unbounded observables (the second moments of the instantaneous polarization of the system) on long-range surface correlations and that the relations of electrostatics are verified by means of shape-dependent thermodynamic limits. This picture is supported (i) by exact solutions and asymptotic analysis of the Debye-Hückel approximation of multicomponent plasmas in disks and spheres with insulating and conducting environment and also in ellipses in a vacuum, and (ii) by computer simulations of a one-component plasma in a disk with different environments, notably a conducting environment with permeable and impermeable wall. These observations have revealed for the first time the reason why the susceptibility of a conducting disk in a conductor with impermeable walls diverges linearly with the radius of the disk: this is due to the occurrence of long-range radial correlations in the conductor. These findings are quantitatively interpreted in terms of a novel canonical Debye-Huckel approximation as contrasted to the ordinary grand canonical version. Lastly a fresh look at the problem of the surface correlations of a conductor in a vacuum, which places the observer close to the surface of the conductor but in the vacuum, is presented and applied to the disk, the ellipse, the cylinder, the sphere, and the wedge. 相似文献
106.
107.
超高真空中银表面垂直谐波电流的实验测量 总被引:1,自引:1,他引:0
在超高真空的条件下,测量了清洁、自由银表面产生的光学二次谐波随基波电矢量与入射面之间夹角(?)的变化,从而通过理论公式,求得由Rudnick和Stern引入的,用于衡量垂直面电流密度的唯象参数a的值,在入射基频光波长为1.064μm时,被测定为-4.0±0.8. 相似文献
108.
本文利用表面光电压谱(Surface Photovohage spectroscopy,简称SPS)研究了ZnTPP对TiO_2粉末的光谱敏化,发现用ZnTPP修饰后的TiO_2(金红石和锐钛矿)粉末在可见区420、550和590nm附近有三个光伏响应带,它们分别对应于ZnTPP的Soret、Q(1,0)和Q(0,0)带。经过严格的实验和分析,证明这三个带是由ZnTPP对TiO_2的敏化光电压引起的,而不是ZnTPP自身的光伏响应。在敏化效果上,亚稳的锐钛矿优于金红石。同时,我们对这种光敏表面的光诱导电荷转移机制和SPS作为一种研究光谱敏化方法的可行性进行了讨论。 相似文献
109.
In order to elucidate the mechanism of reaction M+ + SCO, both triplet and singlet potential energy surfaces (PESs) for the reaction of Sc+ + SCO have been theoretically investigated using the DFT (B3LYP/6-311+G*) level of theory. The geometries for reactants, intermediates, transition states and products were completely optimized. All the transition states were verified by the vibrational analysis and the intrinsic reaction coordinate calculations. The involving potential energy curve-crossing dramatically affects reaction mechanism, reaction rate has been discussed, and the crossing points (CPs) have been localized by the approach suggested by Yoshizawa et al. The present results show that the reaction mechanism are insertion–elimination mechanism both along the C–S and C–O bond activation branches, but the C–S bond activation is much more favorable in energy than the C–O bond activation. All theoretical results not only support the existing conclusions inferred from early experiment, but also complement the pathway and mechanism for this reaction. 相似文献
110.