全文获取类型
收费全文 | 1878篇 |
免费 | 118篇 |
出版年
2023年 | 13篇 |
2022年 | 16篇 |
2021年 | 45篇 |
2020年 | 27篇 |
2019年 | 40篇 |
2018年 | 60篇 |
2017年 | 46篇 |
2016年 | 61篇 |
2015年 | 89篇 |
2014年 | 110篇 |
2013年 | 126篇 |
2012年 | 141篇 |
2011年 | 123篇 |
2010年 | 86篇 |
2009年 | 82篇 |
2008年 | 91篇 |
2007年 | 108篇 |
2006年 | 65篇 |
2005年 | 75篇 |
2004年 | 56篇 |
2003年 | 54篇 |
2002年 | 51篇 |
2001年 | 22篇 |
2000年 | 29篇 |
1999年 | 19篇 |
1998年 | 8篇 |
1997年 | 10篇 |
1995年 | 10篇 |
1994年 | 10篇 |
1992年 | 12篇 |
1991年 | 25篇 |
1990年 | 17篇 |
1989年 | 23篇 |
1988年 | 11篇 |
1987年 | 9篇 |
1986年 | 10篇 |
1985年 | 17篇 |
1984年 | 22篇 |
1983年 | 10篇 |
1982年 | 18篇 |
1981年 | 11篇 |
1980年 | 11篇 |
1979年 | 22篇 |
1978年 | 12篇 |
1977年 | 14篇 |
1975年 | 13篇 |
1974年 | 8篇 |
1973年 | 10篇 |
1972年 | 9篇 |
1971年 | 7篇 |
排序方式: 共有1996条查询结果,搜索用时 15 毫秒
1.
R C Shukla 《Acta anatomica》1979,103(1):119-124
The digest of the pure epidermis preparation from Macaca mulatta demonstrated three types of dendritic cells i.e. (1) dopa-positive melanocytes, (2) dopa-negative Langerhans' cells and (3) weakly dopa-positive intermediate cells of Billingham and Medawar. The last type of cell was found to have characteristics being intermediate between those of the melanocytes and of the Langerhans' cell. A similar digest prepared from the epidermis of the rhesus monkey demonstrated isomorphous dendritic cells which were all dopa-negative. Here also the intermediate cells of Billingham and Medawar with characteristics intermediate between those of the melanocytes and of the Langerhans' cells were identified. 相似文献
2.
Phytochemical analysis of dried twigs of Marsdenia roylei (family Asclepiadaceae) has resulted in the isolation of a trisaccharide, maryal, and a diglycoside, rolinose. Their structures were determined as O-beta-D-oleandropyranosyl-(1-->4)-O-beta-D-digitoxopyranosyl++ +-(1-->4)-D- cymaral and ethyl O-beta-D-oleandropyranosyl-(1-->4)-O-3-O-methyl-6-deoxy-beta-D- allopyranoside, respectively, by chemical degradation and spectroscopic methods. 相似文献
3.
4.
A number of environmental chemical pollutants have been reported to cause tumors or help in the propagation of tumors in experimental animals. The in-vitro effects of a few chemical contaminants were studied on the histone phosphorylation and 3H Phorbol dibutyrate (PdBu) binding of partially purified Ca2+/phospholipid dependent protein kinase c (PKC) from the brains of Fischer F344 and B6C3F1 mice. The enzyme was prepared by a modified method which gave approximately 75-fold purification. A differential effect of various compounds was observed on the phosphorylation activity and PdBu binding of PKC from rats and mice. The reported tumor promoting ability and effect on protein kinase C activity appeared to be related in the case of the rat enzyme, although causality cannot be inferred. 相似文献
5.
6.
7.
Using Liapunov's direct method, effects of dispersal on the linear and nonlinear stability of the equilibrium state for a prey-predator system with functional response are investigated. It is noted that the functional response has a destabilizing effect. It is shown that an otherwise linearly or nonlinearly stable equilibrium state of the system remains so with dispersal as well, even with functional response. It is further established that if the equilibrium state is linearly stable a subregion of the positive quadrant can be found in the phase plane where it is nonlinearly stable with or without dispersal. 相似文献
8.
9.
10.
The well-known Late Cretaceous Lameta Ghat locality (Jabalpur, India) provides a window of opportunity to study a large stable, near shore sandy beach, which was widely used by sauropod dinosaurs as a hatchery. In this paper, we revisit the eggs and eggshell fragments previously assigned to lizards from this locality and reassign them to crocodylomorphs. Several features point to a crocodilian affinity, including a subspherical to ellipsoidal shape, smooth, uneven external surface, discrete trapezoid shaped shell units with wide top and narrow base, basal knobs and wedge shaped crystallites showing typical inverted triangular extinction under crossed nicols. The crocodylomorph eggshell material presented in this paper adds to the skeletal data of these most probably Cretaceous-Eocene dryosaurid crocodiles. 相似文献