全文获取类型
收费全文 | 993篇 |
免费 | 59篇 |
出版年
2022年 | 4篇 |
2021年 | 6篇 |
2020年 | 6篇 |
2019年 | 6篇 |
2018年 | 9篇 |
2017年 | 10篇 |
2016年 | 12篇 |
2015年 | 24篇 |
2014年 | 36篇 |
2013年 | 46篇 |
2012年 | 53篇 |
2011年 | 43篇 |
2010年 | 39篇 |
2009年 | 22篇 |
2008年 | 51篇 |
2007年 | 47篇 |
2006年 | 48篇 |
2005年 | 39篇 |
2004年 | 49篇 |
2003年 | 48篇 |
2002年 | 52篇 |
2001年 | 51篇 |
2000年 | 43篇 |
1999年 | 29篇 |
1998年 | 20篇 |
1997年 | 20篇 |
1996年 | 6篇 |
1995年 | 12篇 |
1994年 | 8篇 |
1993年 | 9篇 |
1992年 | 13篇 |
1991年 | 17篇 |
1990年 | 5篇 |
1989年 | 11篇 |
1988年 | 10篇 |
1987年 | 16篇 |
1986年 | 12篇 |
1985年 | 14篇 |
1984年 | 7篇 |
1983年 | 12篇 |
1982年 | 10篇 |
1981年 | 8篇 |
1980年 | 8篇 |
1979年 | 9篇 |
1978年 | 8篇 |
1977年 | 9篇 |
1976年 | 9篇 |
1973年 | 6篇 |
1970年 | 4篇 |
1969年 | 4篇 |
排序方式: 共有1052条查询结果,搜索用时 15 毫秒
221.
222.
Rapid loss of 7-methylguanine from liver nucleic acids in mice during the initial stage of liver carcinogenesis induced by dimethylnitrosamine 总被引:3,自引:0,他引:3
Dimethylnitrosamine was administered to mice in their drinking water. The amount of 7-methylguanine in liver nucleic acids was found to increase initially and then to decrease. This decrease in 7-methylguanine was found to be due to decrease in the rate of its formation and increase in its excision from nucleic acids. 相似文献
223.
224.
225.
Takayama Koji Crawford Daniel J. López-Sepúlveda Patricio Greimler Josef Stuessy Tod F. 《Journal of plant research》2019,132(2):295-295
Journal of Plant Research - The article Factors driving adaptive radiation in plants of oceanic islands: a case study from the Juan Fernández Archipelago, written by Koji Takayama, Daniel J.... 相似文献
226.
227.
Fujii Y Hirayama T Ohtake H Ono N Inoue T Sakurai T Takayama T Matsumoto K Tsukahara N Hidano S Harima N Nakazawa K Igarashi Y Goitsuka R 《Journal of immunology (Baltimore, Md. : 1950)》2012,188(1):206-215
Sphingosine 1-phosphate (S1P) regulates lymphocyte trafficking through the type 1 sphingosine 1-phosphate receptor (S1P(1)) and participates in many pathological conditions, including autoimmune diseases. We developed a novel S1P(1)-selective antagonist, TASP0277308, which is structurally unrelated to S1P. This antagonist competitively inhibited S1P-induced cellular responses, such as chemotaxis and receptor internalization. Furthermore, differing from previously reported S1P(1) antagonists, TASP0277308 demonstrated in vivo activities to induce lymphopenia, a block in T cell egress from the thymus, displacement of marginal zone B cells, and upregulation of CD69 expression on both T and B cells, all of which recapitulate phenotypes of S1P(1)-deficient lymphocytes. In a mouse collagen-induced arthritis model, TASP0277308 significantly suppressed the development of arthritis, even after the onset of disease. These findings provide the first chemical evidence to our knowledge that S1P(1) antagonism is responsible for immunosuppression in the treatment of autoimmune diseases and also resolve the discrepancies between genetic and chemical studies on the functions of S1P(1) in lymphocytes. 相似文献
228.
The pathways whereby Sox2 scans DNA to locate its specific binding site are investigated by NMR in specific and nonspecific Sox2·DNA complexes and in a specific ternary complex with Oct1 on the Hoxb1 regulatory element. Direct transfer of Sox2 between nonspecific sites on different DNA molecules occurs without dissociation into free solution at a rate of ~10(6) M(-1) s(-1), whereas one-dimensional sliding proceeds with a diffusion constant of ≥0.1 μm(2)·s(-1). Translocation of Sox2 from one specific DNA site to another occurs via jumping, involving complete dissociation into free solution (k(d) ~5-6 s(-1)) followed by reassociation (k(a) ~5 × 10(8) M(-1) s(-1)). In the presence of Oct1 bound to an adjacent specific site, k(d) is reduced by more than 10-fold. Paramagnetic relaxation measurements, however, demonstrate that sparsely populated (<1%), transient states involving nonspecifically bound Sox2 in rapid exchange with specifically bound Sox2 are sampled in both binary Sox2·DNA- and ternary Oct1·Sox2·Hoxb1-DNA-specific complexes. Moreover, Sox2 modulates the mechanism of translocation of Oct1. Both Sox2 and the Oct1 POU(HD) domain are transiently released from the specific ternary complex by sliding to an adjacent nonspecific site, followed by direct transfer to another DNA molecule, whereas the Oct1 POU(S) domain is fixed to its specific site through direct interactions with Sox2. Intermolecular translocation of POU(HD) results in the formation of a bridged intermediate spanning two DNA molecules, enhancing the probability of complete intermolecular translocation of Oct1. By way of contrast, in the specific Oct1·DNA binary complex, POU(S) undergoes direct intermolecular translocation, whereas POU(HD) scans the DNA by sliding. 相似文献
229.
Shouhei Ueda Tadahiro Okubo Takao Itioka Usun Shimizu-kaya Masaya Yago Yoko Inui Takao Itino 《Ecological Research》2012,27(2):437-443
In the Southeast Asian tropics, Arhopala lycaenid butterflies feed on Macaranga ant-plants inhabited by Crematogaster (subgenus Decacrema) ants tending Coccus-scale insects. A recent phylogenetic study showed that (1) the plants and ants have been codiversifying for the past 20–16
million years (Myr), and that (2) the tripartite symbiosis was formed 9–7 Myr ago, when the scale insects became involved
in the plant–ant mutualism. To determine when the lycaenids first parasitized the Macaranga tripartite symbiosis, we constructed a molecular phylogeny of the lycaenids that feed on Macaranga by using mitochondrial and nuclear DNA sequence data and estimated their divergence times based on the cytochrome oxidase I molecular clock. The minimum age of the lycaenids was estimated by the time-calibrated phylogeny to be 2.05 Myr, about one-tenth
the age of the plant–ant association, suggesting that the lycaenids are latecomers that associated themselves with the pre-existing
symbiosis of plant, ant, and scale insects. 相似文献
230.
The glucocorticoid receptor represses cyclin D1 by targeting the Tcf-beta-catenin complex 总被引:4,自引:0,他引:4
Takayama S Rogatsky I Schwarcz LE Darimont BD 《The Journal of biological chemistry》2006,281(26):17856-17863