全文获取类型
收费全文 | 15012篇 |
免费 | 2413篇 |
国内免费 | 2023篇 |
专业分类
化学 | 11116篇 |
晶体学 | 180篇 |
力学 | 860篇 |
综合类 | 151篇 |
数学 | 1965篇 |
物理学 | 5176篇 |
出版年
2024年 | 35篇 |
2023年 | 315篇 |
2022年 | 429篇 |
2021年 | 488篇 |
2020年 | 604篇 |
2019年 | 595篇 |
2018年 | 468篇 |
2017年 | 375篇 |
2016年 | 676篇 |
2015年 | 672篇 |
2014年 | 841篇 |
2013年 | 1099篇 |
2012年 | 1310篇 |
2011年 | 1329篇 |
2010年 | 965篇 |
2009年 | 822篇 |
2008年 | 932篇 |
2007年 | 907篇 |
2006年 | 843篇 |
2005年 | 765篇 |
2004年 | 562篇 |
2003年 | 503篇 |
2002年 | 530篇 |
2001年 | 462篇 |
2000年 | 342篇 |
1999年 | 326篇 |
1998年 | 309篇 |
1997年 | 268篇 |
1996年 | 274篇 |
1995年 | 223篇 |
1994年 | 207篇 |
1993年 | 176篇 |
1992年 | 150篇 |
1991年 | 132篇 |
1990年 | 94篇 |
1989年 | 97篇 |
1988年 | 64篇 |
1987年 | 43篇 |
1986年 | 34篇 |
1985年 | 48篇 |
1984年 | 45篇 |
1983年 | 22篇 |
1982年 | 21篇 |
1981年 | 13篇 |
1980年 | 13篇 |
1978年 | 3篇 |
1977年 | 3篇 |
1976年 | 2篇 |
1971年 | 2篇 |
1957年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 125 毫秒
61.
62.
The properties of pulsed laser vapor doping on p-Si(1 0 0) with a KrF (248 nm) excimer pulsed laser (248 nm) and BCl3 gas are reported in this paper. The doped samples are characterized by the resistance measured using a four-probe method, since the sheet resistance changes with the carrier concentration of the sample. The doping effects with the variation of laser energy density, pulse number, and the pressure of BCl3 were investigated in terms of the sheet resistance. In this way, the optimized parameters were obtained and used for the positive heavy doping on p-Si(1 0 0) and p-Si(1 1 1). Then, using a square mesh under the above conditions, an image doping was completed. Finally, the metal–semiconductor Ohmic contacts were realized by plating Ag and Cu films on the doped surface. 相似文献
63.
64.
本文对轴对称场二极管区电子运动所遵循的近似轨迹方程进行数值求解,以此做为设计相对论二极管电子枪的依据,与实验结果相比较,符合较好。 相似文献
65.
66.
Qing Shi Dong Yang Yanlei Su Jian Li Zhongyi Jiang Yanjun Jiang Weikang Yuan 《Journal of nanoparticle research》2007,9(6):1205-1210
Lipase from Candida rugosa was covalently anchored onto acid-treated multi-walled carbon nanotubes (MWNTs) through a self-catalytic mechanism. A variety
of characterization techniques including FTIR, Raman spectroscopy, and XPS were employed to demonstrate the formation of the
ester linkage between lipase and MWNTs. The MWNTs-lipase biocomposites showed significantly increased solubility in some common-used
organic solvents, such as THF, DMF and chloroform. This study may offer a novel and facile route for covalent modification
of carbon nanotubes, and expand the potential utilization of both lipases and MWNTs in the fields of biocatalyst and biosensor. 相似文献
67.
The main aim of this paper is to provide convergence analysis of Quasi-Wilson nonconforming finite element to Maxwell's equations under arbitrary quadrilateral meshes.The error estimates are derived,which are the same as those for conforming elements under conventional regular meshes. 相似文献
68.
Weimin Xue 《中国科学A辑(英文版)》1997,40(7):673-679
A ringR is left co-semihereditary (strongly left co-semihereditary) if every finitely cogenerated factor of a finitely cogenerated
(arbitrary) injective leftR-module is injective. A left co-semihereditary ring, which is not strongly left co-semihereditary, is given to answer a question
of Miller and Tumidge in the negative. If
R
U
S
defines a Morita duality,R is proved to be left co-semihereditary (left semihereditmy) if and only ifS is right semihereditary (right co-semihereditary). Assuming thatS⩾R is an almost excellent extension,S is shown to be (strongly) right co-semihereditary if and only ifR is (strongly) right co-semihereditary.
Project supported by the National Natural Science Foundation of China. 相似文献
69.
Hua Jin Zhuangqi Hu Qingmin Liu Yunlong Ge Changxu Shi 《Applied Physics A: Materials Science & Processing》1992,54(5):399-403
A crystallization study has been carried out for rapidly solidified Bi2Pb0.5Sr2Ca4Cu5Ox glass. Glass transition temperature T
g, crystallized superconducting phases and microstructural changes were measured and analysed by differential thermal analysis (DTA), X-ray diffraction (XRD), and scanning electron microscopy (SEM). The crystallization mechanism of the three superconducting phases — (2201) 20 K phase, (2212) 80 K phase, and (2223) 110 K phase — has been discussed, and a time-temperature-transformation diagram for the glass has been constructed. 相似文献
70.
本文采用了一种简单的功率监测法,观察了KrF准分子激光对掺锗光纤折射率影响的非线性过程。观察到子纤芯折射率扰动过程中非稳定现象、饱和现象和折射率扰动的非线性。 相似文献