全文获取类型
收费全文 | 28242篇 |
免费 | 636篇 |
国内免费 | 172篇 |
专业分类
化学 | 18790篇 |
晶体学 | 229篇 |
力学 | 692篇 |
综合类 | 1篇 |
数学 | 4877篇 |
物理学 | 4461篇 |
出版年
2021年 | 195篇 |
2020年 | 240篇 |
2019年 | 303篇 |
2018年 | 251篇 |
2017年 | 226篇 |
2016年 | 482篇 |
2015年 | 374篇 |
2014年 | 494篇 |
2013年 | 1420篇 |
2012年 | 1270篇 |
2011年 | 1593篇 |
2010年 | 832篇 |
2009年 | 670篇 |
2008年 | 1444篇 |
2007年 | 1505篇 |
2006年 | 1500篇 |
2005年 | 1495篇 |
2004年 | 1327篇 |
2003年 | 1108篇 |
2002年 | 1067篇 |
2001年 | 400篇 |
2000年 | 322篇 |
1999年 | 258篇 |
1998年 | 303篇 |
1997年 | 333篇 |
1996年 | 435篇 |
1995年 | 329篇 |
1994年 | 303篇 |
1993年 | 311篇 |
1992年 | 301篇 |
1991年 | 260篇 |
1990年 | 241篇 |
1989年 | 258篇 |
1988年 | 284篇 |
1987年 | 266篇 |
1986年 | 267篇 |
1985年 | 414篇 |
1984年 | 468篇 |
1983年 | 337篇 |
1982年 | 463篇 |
1981年 | 430篇 |
1980年 | 382篇 |
1979年 | 368篇 |
1978年 | 378篇 |
1977年 | 372篇 |
1976年 | 319篇 |
1975年 | 312篇 |
1974年 | 294篇 |
1973年 | 264篇 |
1972年 | 159篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
41.
42.
43.
O.M. Hussain A.S. Swapnasmitha J. John R. Pinto 《Applied Physics A: Materials Science & Processing》2005,81(6):1291-1297
The structure and surface morphology of WO3 thin films deposited by a laser-ablation technique have been found to be strongly dependent on the deposition conditions and the nature of the substrate. By precisely controlling the substrate temperature and the oxygen partial pressure, amorphous, polycrystalline, nano-crystalline and iso-epitaxial WO3 thin films were successfully grown. The structure and surface morphological features of the films from X-ray diffraction and atomic force microscopy data are described in relation to the deposition conditions. PACS 81.15.Fg; 68.55.-a; 68.37.Ps 相似文献
44.
45.
John Strantzen 《Journal of Geometry》1989,36(1-2):160-172
46.
47.
48.
49.
In an earlier paper on a malignant cell invasion model (Marchantet al., SIAM J. Appl. Math, 60, 2000) we introduced a novelform of discontinuous travelling wave solution. These solutionscould be studied easily by combining behaviour within a phaseplane with the RankineHugoniot shock conditions, whichdescribe properties (such as the ratio of the jump discontinuitiesto the speed of propagation) that solutions may possess. Theseresults were new for several reasons. The shock conditions relateto hyperbolic equations (which the model is) but were appliedin a travelling wave ordinary differential equation phase planeusing techniques that usually apply to parabolic reactiondiffusionsystems. In addition the solutions possess singular behaviournear several points in the phase plane but in spite of thisthere exists a robust and stable family of physically interestingsolutions. In this paper we discuss two previously studied models, oneof detonation theory and one of angiogenesis. We show that eachof these models also possesses a family of discontinuous travellingwave solutions which was not previously discovered. Of particularinterest is the solution which has a blunt interface at thefront of the invading profile. In all three models it is thissolution that is seen to stably evolve from physically relevantinitial data, and for physically relevant parameter values. This work confirms the robustness of these novel travellingwave solutions and their applicability to a wider range of mathematicalmodelling situations. 相似文献
50.
Apurba Bhattacharya Nitin C. Patel Michael Peddicord Luca Parlanti John A. Grosso 《Tetrahedron letters》2006,47(30):5341-5343
An efficient, one-pot, phase transfer N-amination technology was developed. The protocol utilizes chloramine, an inexpensive and safe electrophilic aminating agent potentially viable for commercial manufacturing. 相似文献