全文获取类型
收费全文 | 26223篇 |
免费 | 615篇 |
国内免费 | 160篇 |
专业分类
化学 | 17636篇 |
晶体学 | 215篇 |
力学 | 658篇 |
综合类 | 1篇 |
数学 | 4428篇 |
物理学 | 4060篇 |
出版年
2021年 | 178篇 |
2020年 | 219篇 |
2019年 | 291篇 |
2018年 | 236篇 |
2017年 | 211篇 |
2016年 | 458篇 |
2015年 | 355篇 |
2014年 | 466篇 |
2013年 | 1333篇 |
2012年 | 1201篇 |
2011年 | 1521篇 |
2010年 | 784篇 |
2009年 | 628篇 |
2008年 | 1372篇 |
2007年 | 1424篇 |
2006年 | 1417篇 |
2005年 | 1414篇 |
2004年 | 1240篇 |
2003年 | 1048篇 |
2002年 | 1022篇 |
2001年 | 371篇 |
2000年 | 300篇 |
1999年 | 245篇 |
1998年 | 285篇 |
1997年 | 312篇 |
1996年 | 394篇 |
1995年 | 298篇 |
1994年 | 282篇 |
1993年 | 288篇 |
1992年 | 275篇 |
1991年 | 239篇 |
1990年 | 225篇 |
1989年 | 242篇 |
1988年 | 268篇 |
1987年 | 250篇 |
1986年 | 245篇 |
1985年 | 387篇 |
1984年 | 436篇 |
1983年 | 322篇 |
1982年 | 427篇 |
1981年 | 403篇 |
1980年 | 342篇 |
1979年 | 331篇 |
1978年 | 347篇 |
1977年 | 332篇 |
1976年 | 275篇 |
1975年 | 271篇 |
1974年 | 261篇 |
1973年 | 240篇 |
1972年 | 143篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
Many biological and medical studies have as a response of interest the time to occurrence of some event, such as the occurrence of a particular symptom or disease, remission, relapse, death due to some specific disease, or simply death. In this paper we study the problem of assessing the effect of potential risk factors on the outcome event of interest through a parametric or semi-parametric frailty model where the lifetimes have a reason to be considered dependent. This dependence may arise because of multiple endpoints within the same individual or because, when studying a single endpoint, there are natural groupings between study subjects. The objective of this paper is to extend both parametric and semi-parametric approaches to regression analysis in which the lifetimes of individuals in a group are effected by the same random frailty which follows a positive stable distribution. Some comparisons of the properties of this frailty distribution with other frailty distributions are made and an example which assesses the effect of a treatment in a litter-matched tumorigenesis study is presented. 相似文献
32.
John L. Wood Johannes Schwarzenberg Edward F. Zganjar Dubravka Rupnik 《Hyperfine Interactions》1992,75(1-4):51-58
State-of-the-art spectroscopy of nuclei far from stability has achieved an extraordinary level of sophistication and detail
in the last ten years. In principle, if a state can be populated, it can be characterized by its energy, spin, parity, and
major decay paths. Sometimes its lifetime can be measured. In practice, one is confronted with enormous complexity. To convert
raw spectroscopic data into nuclear structure data involves a complex process of disentangling gamma rays and conversion electrons
into decay schemes. Specifically, coincidence techniques, especially coincidence intensities, play a crucial role in this
process. Recent examples and methods from work done at UNISOR are presented. 相似文献
33.
34.
35.
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
36.
37.
John Strantzen 《Journal of Geometry》1989,36(1-2):160-172
38.
39.
40.