全文获取类型
收费全文 | 1905篇 |
免费 | 142篇 |
国内免费 | 1篇 |
出版年
2023年 | 13篇 |
2022年 | 16篇 |
2021年 | 46篇 |
2020年 | 41篇 |
2019年 | 41篇 |
2018年 | 35篇 |
2017年 | 34篇 |
2016年 | 49篇 |
2015年 | 61篇 |
2014年 | 78篇 |
2013年 | 126篇 |
2012年 | 137篇 |
2011年 | 98篇 |
2010年 | 85篇 |
2009年 | 82篇 |
2008年 | 102篇 |
2007年 | 96篇 |
2006年 | 79篇 |
2005年 | 77篇 |
2004年 | 58篇 |
2003年 | 44篇 |
2002年 | 58篇 |
2001年 | 42篇 |
2000年 | 35篇 |
1999年 | 26篇 |
1998年 | 20篇 |
1997年 | 16篇 |
1996年 | 18篇 |
1995年 | 11篇 |
1993年 | 15篇 |
1992年 | 21篇 |
1991年 | 24篇 |
1990年 | 20篇 |
1989年 | 33篇 |
1988年 | 22篇 |
1987年 | 20篇 |
1986年 | 16篇 |
1985年 | 30篇 |
1984年 | 23篇 |
1982年 | 12篇 |
1981年 | 15篇 |
1979年 | 14篇 |
1977年 | 13篇 |
1976年 | 14篇 |
1975年 | 9篇 |
1974年 | 14篇 |
1973年 | 9篇 |
1972年 | 10篇 |
1971年 | 9篇 |
1966年 | 11篇 |
排序方式: 共有2048条查询结果,搜索用时 31 毫秒
1.
2.
The univalent reduction of oxygen by reduced flavins and quinones 总被引:15,自引:0,他引:15
3.
Natural killer T (NKT) cells are a component of innate and adaptive immune systems implicated in immune, autoimmune responses and in the control of obesity and cancer. NKT cells develop from common CD4+ CD8+ double positive (DP) thymocyte precursors after the rearrangement and expression of T cell receptor (TCR) Vα14-Jα18 gene. Temporal regulation and late appearance of Vα14-Jα18 rearrangement in immature DP thymocytes has been demonstrated. However, the precise control of lifetime of DP thymocytes in vivo that enables distal rearrangements remains incompletely defined. Here we demonstrate that T cell factor (TCF)-1, encoded by the Tcf7 gene, is critical for the extended lifetime of DP thymocytes. TCF-1-deficient DP thymocytes fail to undergo TCR Vα14-Jα18 rearrangement and produce significantly fewer NKT cells. Ectopic expression of Bcl-xL permits Vα14-Jα18 rearrangement and rescues NKT cell development. We report that TCF-1 regulates expression of RORγt, which regulates DP thymocyte survival by controlling expression of Bcl-xL. We posit that TCF-1 along with its cofactors controls the lifetime of DP thymocytes in vivo. 相似文献
4.
5.
6.
7.
A theoretical investigation of capillary-tissue fluid exchange has been studied including the characteristics and influence of the boundaries and media through which the fluid flows. Filtration from a cylindrical capillary into the concentrically surrounding tissue space and flow from a capillary into the tissue across a thin membrane are analyzed in detail. In has been observed that the filtration efficiency of the functional unit decreases as the viscosity of the peripheral layer increases. Contrary to the results of Apelblat [17], the slip velocity at the porous boundary plays a dominant role in filtration efficiency. It has also been noticed that the filtration efficiency decreases as the slip velocity at the porous boundary increases. 相似文献
8.
9.
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
10.
A novel ompC mutation of Escherichia coli K-12 that reduces OmpC and OmpF levels in the outer membrane 总被引:1,自引:0,他引:1
Rajeev Misra 《Molecular microbiology》1993,10(5):1029-1035