全文获取类型
收费全文 | 9172篇 |
免费 | 207篇 |
国内免费 | 20篇 |
专业分类
化学 | 5730篇 |
晶体学 | 143篇 |
力学 | 198篇 |
数学 | 1325篇 |
物理学 | 2003篇 |
出版年
2020年 | 84篇 |
2019年 | 80篇 |
2016年 | 156篇 |
2015年 | 130篇 |
2014年 | 152篇 |
2013年 | 287篇 |
2012年 | 292篇 |
2011年 | 374篇 |
2010年 | 219篇 |
2009年 | 210篇 |
2008年 | 314篇 |
2007年 | 296篇 |
2006年 | 318篇 |
2005年 | 281篇 |
2004年 | 291篇 |
2003年 | 256篇 |
2002年 | 236篇 |
2001年 | 168篇 |
2000年 | 212篇 |
1999年 | 137篇 |
1998年 | 129篇 |
1997年 | 122篇 |
1996年 | 157篇 |
1995年 | 174篇 |
1994年 | 151篇 |
1993年 | 132篇 |
1992年 | 138篇 |
1991年 | 127篇 |
1990年 | 122篇 |
1989年 | 140篇 |
1988年 | 146篇 |
1987年 | 126篇 |
1986年 | 123篇 |
1985年 | 151篇 |
1984年 | 109篇 |
1983年 | 143篇 |
1982年 | 145篇 |
1981年 | 153篇 |
1980年 | 129篇 |
1979年 | 153篇 |
1978年 | 135篇 |
1977年 | 119篇 |
1976年 | 111篇 |
1975年 | 91篇 |
1974年 | 105篇 |
1973年 | 109篇 |
1972年 | 65篇 |
1971年 | 80篇 |
1970年 | 66篇 |
1968年 | 65篇 |
排序方式: 共有9399条查询结果,搜索用时 15 毫秒
1.
Annals of Global Analysis and Geometry - In this paper, we characterize round spheres in the Euclidean space under some suitable conditions on the r-mean curvature. 相似文献
2.
3.
4.
Synthesis of optically active sesquiterpenes with a eudesmane C-skeleton from the chiral starting material thujone involves transformation of a tricyclic intermediate (1R,2R,4S)-1,7-dimethyl-4-(1-methylethyl)tricyclo[4.4.0.02,4]dec-6-en-8-one ( 2 ) into the bicyclic compound β -cyperone ( 5 ). Hydroxylation of 2 at C(5) or C(11) permits subsequent opening of the cyclopropane ring and rearrangement to β -cyperone. In this publication, studies involving hydroxylation of 2 by fungal cultures are presented. The resultant products are useful intermediates in efficient synthesis of eudesmane sesquiterpenes. Of five fungi tested, Rhizopus oryzae ATCC 11145 proved most versatile. It hydroxylates at the exocyclic C(11) position in high yield (70%) and, to a lesser extent, at C(5) (5%). Enzymatic activity appears at the end of growth phase and at least 2.2 g of 2 per liter can be metabolized without significant loss of product yield. A second fungus, Cunninghamella echinulata ATCC 9244, proved most useful for hydroxylation of derivatives of 2 for the preparation of derivatives of β -cyperone, although product yields were low (2–20%), some derivatives were nonreactive, and hydroxylation at C(9) occurred. The relationship between precursor structure and enzyme affinity is discussed. 相似文献
5.
In complex biological systems, entities that are conceptually distinct but empirically related—such as sunlight and plant growth or antigene and immune response—are being explicitly linked through the identification of highly specific uninterrupted interaction sequences that take place between their macromolecular system components. These uninterrupted sequences of causation include common elements that are shared by the empirically related but conceptually distinct entities. Through the identification of specific shared elements, “conceptual continuity” is established between these entities. Examples are introduced to suggest that in sociopolitical systems, an analogous conceptual continuity can be established between distinct sociopolitical entities. The identification of specific shared elements, essential for the well being of each of the entities, can play a significant role in resolving conflicts between those separated by seemingly insurmountable obstacles such as race or religion or ideology. © 2006 Wiley Periodicals, Inc. Complexity 11:20–24, 2006 相似文献
6.
Werner Leißner 《Results in Mathematics》1991,20(1-2):530-537
7.
We relate the Schramm–Loewner Evolution processes (SLE) to highest-weight representations of the Virasoro Algebra. The restriction properties of SLE that have been recently derived in [19] play a crucial role. In this setup, various considerations from conformal field theory can be interpreted and reformulated via SLE. This enables one to make a concrete link between the two-dimensional discrete critical systems from statistical physics and conformal field theory. To cite this article: R. Friedrich, W. Werner, C. R. Acad. Sci. Paris, Ser. I 335 (2002) 947–952. 相似文献
8.
9.
10.