全文获取类型
收费全文 | 34858篇 |
免费 | 5920篇 |
国内免费 | 5156篇 |
专业分类
化学 | 25911篇 |
晶体学 | 649篇 |
力学 | 1891篇 |
综合类 | 431篇 |
数学 | 3968篇 |
物理学 | 13084篇 |
出版年
2024年 | 97篇 |
2023年 | 613篇 |
2022年 | 1031篇 |
2021年 | 1143篇 |
2020年 | 1303篇 |
2019年 | 1413篇 |
2018年 | 1120篇 |
2017年 | 1058篇 |
2016年 | 1584篇 |
2015年 | 1650篇 |
2014年 | 1958篇 |
2013年 | 2559篇 |
2012年 | 3203篇 |
2011年 | 3103篇 |
2010年 | 2421篇 |
2009年 | 2243篇 |
2008年 | 2532篇 |
2007年 | 2243篇 |
2006年 | 2195篇 |
2005年 | 1980篇 |
2004年 | 1546篇 |
2003年 | 1259篇 |
2002年 | 1340篇 |
2001年 | 1085篇 |
2000年 | 839篇 |
1999年 | 715篇 |
1998年 | 527篇 |
1997年 | 434篇 |
1996年 | 432篇 |
1995年 | 366篇 |
1994年 | 363篇 |
1993年 | 292篇 |
1992年 | 212篇 |
1991年 | 223篇 |
1990年 | 149篇 |
1989年 | 137篇 |
1988年 | 110篇 |
1987年 | 63篇 |
1986年 | 62篇 |
1985年 | 78篇 |
1984年 | 63篇 |
1983年 | 38篇 |
1982年 | 33篇 |
1981年 | 29篇 |
1980年 | 23篇 |
1979年 | 14篇 |
1978年 | 10篇 |
1977年 | 10篇 |
1957年 | 8篇 |
1936年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
41.
KANG Zihua WANG Mingwei QIAN Jiamei RAO Jun LI Xiujuan ZHENG Tieliu WANG Xuehua 《核工业西南物理研究院年报(英文版)》2004,(1):73-76
Lower hybrid wave (LHW), electro cyclotron (EC) and neutral beam injection (NBI) etc. are the important methods of auxiliary heating. They would be devoted to the HL-2A tokamak step by step. In order to satisfy the debug of each system and the need of the experiment, the system should be equipped with high voltage pulse power (HVPP) according to the requirement. 相似文献
42.
Shu Fen Wang Wen Guo Zou Su Wen Liu Dong Xu Duo Rong Yuan Guang Jun Zhou 《Journal of Physics and Chemistry of Solids》2004,65(7):1243-1245
The photoluminescence properties of the Bi3+ in sol-gel derived ZnTiO3 nanocrystals have been investigated. An ultra-violet emission at 360 nm and a visible emission band at 506 nm have been observed, originating from two kinds of emission centers. The former is ascribed to the 3P1-1S0 transition of Bi3+ and the latter to the recombination of the electrons with the photo-generated holes trapped in the zinc vacancies. In all cases the latter contribution is predominant. 相似文献
43.
ChunXiaLI YingXiaLI LingBoYU HuaZHANG SiftDongCHU HuaShiGUAN 《中国化学快报》2003,14(8):776-778
A convenient synthetic route was developed for the synthesis of the novel glycolipids: 1,2-di-O-acyl-3-O-(2‘-acylamide-2‘-denxy-ct-D-glucopyranosyl)-sn-glycerols. 10 new compounds of glycolipids with different acyl groups were obtained. 相似文献
44.
5‐Methylene‐2‐oxazolidinone (1) and 5‐methylene‐1,3‐thiazolidine‐2‐thione (4) react with various isocyanates to give the corresponding urethanes 3 and 5 in high yields in the presence of palladium(0) or palladium(II) catalyst under mild reaction conditions. A mechanism is proposed. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
45.
YunFei Liu ShengCai Shi ShengLin Yu 《International Journal of Infrared and Millimeter Waves》2003,24(12):2069-2077
When electromagnetic waves propagate through a wire grid, there will be some evanescent space harmonics generated around the wire grid. In this paper, we mainly investigate their effects on the transmission characteristics of a Gaussian beam by cylindrical wire grids. The results are compared with those without taking account of evanescent space-harmonics. 相似文献
46.
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
47.
48.
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
49.
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
50.
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