全文获取类型
收费全文 | 1152篇 |
免费 | 146篇 |
国内免费 | 12篇 |
出版年
2023年 | 15篇 |
2022年 | 7篇 |
2021年 | 14篇 |
2020年 | 36篇 |
2019年 | 40篇 |
2018年 | 37篇 |
2017年 | 37篇 |
2016年 | 50篇 |
2015年 | 75篇 |
2014年 | 72篇 |
2013年 | 69篇 |
2012年 | 35篇 |
2011年 | 52篇 |
2010年 | 38篇 |
2009年 | 53篇 |
2008年 | 64篇 |
2007年 | 72篇 |
2006年 | 65篇 |
2005年 | 47篇 |
2004年 | 47篇 |
2003年 | 43篇 |
2002年 | 61篇 |
2001年 | 35篇 |
2000年 | 34篇 |
1999年 | 46篇 |
1998年 | 28篇 |
1997年 | 24篇 |
1996年 | 14篇 |
1995年 | 12篇 |
1994年 | 12篇 |
1993年 | 14篇 |
1992年 | 10篇 |
1991年 | 6篇 |
1990年 | 7篇 |
1989年 | 4篇 |
1988年 | 2篇 |
1987年 | 1篇 |
1986年 | 3篇 |
1985年 | 3篇 |
1984年 | 5篇 |
1983年 | 4篇 |
1982年 | 6篇 |
1981年 | 2篇 |
1980年 | 1篇 |
1978年 | 1篇 |
1977年 | 3篇 |
1975年 | 3篇 |
1974年 | 1篇 |
排序方式: 共有1310条查询结果,搜索用时 15 毫秒
1.
3.
4.
Gal Bitan Irena Zeltser Gerardo Byk David Halle Yaffa Mashriki Evgenia V. Gluhov Inna Sukhotinsky Menachem Hanani Zvi Selinger Chaim Gilon 《Journal of peptide science》1996,2(4):261-269
Novel backbone-to-side chain and backbone-to-backbone cyclic analogues of substance P (SP) were prepared by solid-phase synthesis and screened for biological activity. An analogue containing a thioether- lactam ring between positions 9 and 11 showed an EC50 value of 20nM toward the neurokinin 1 (NK-1) and was inactive toward the NK-2 and NK-3 receptors. On the other hand, in a multiple backbone cyclic peptide library of similar analogues, in which the sulphur was excluded from the ring, very low activity was detected. The activity was re-evaluated and was found to be even lower (EC50=0.11 mM ) than the previously published data. These results indicate that the thioether moiety has a crucial role in receptor activation. The results also show tolerance of the NK-1 receptor, but not NK-2 or NK-3, to cyclization of the C-terminal portion of the SP6–11 hexapeptide. 相似文献
5.
It is commonly assumed that in order for animal signals to be advantageous, the information being signalled could not have been obtained otherwise, and is therefore ‘cryptic’ or ‘private’. Here, we suggest a scenario in which individuals can gain an advantage by signalling ‘public’ information that is neither cryptic nor private. In that scenario, signalling increases the efficiency with which that ‘public’ information is transmitted. We formalize our idea with a game in which offspring can signal their condition to their parents. Specifically, we consider a resource‐strapped parent who can only invest in one of its two offspring, and we allow offspring the chance to influence parental investment through a signal. A parent in the game seeks to invest in the higher‐quality offspring, which it could identify either through a publicly available cue, such as body size, or by relying on a signal provided by the offspring. We find that if the signal can convey information about offspring quality more efficiently than cues, then signalling of condition between offspring and parents can be favoured by selection, even though parents could potentially have acquired the same information from the cue. Our results suggest that the biological function of signals may be broader than currently considered, and provide a scenario where low cost signalling can be favoured. More generally, efficiency benefits could explain signalling across a range of biological and economic scenarios. 相似文献
6.
7.
8.
9.
Zhao Sun Jean‐François Hamel Christopher C. Parrish Annie Mercier 《Ecology and evolution》2015,5(5):1117-1129
Classical optimality models of offspring size and number assume a monotonically increasing relationship between offspring size and performance. In aquatic organisms with complex life cycles, the size–performance function is particularly hard to grasp because measures of performance are varied and their relationships with size may not be consistent throughout early ontogeny. Here, we examine size effects in premetamorphic (larval) and postmetamorphic (juvenile) stages of brooding marine animals and show that they vary contextually in strength and direction during ontogeny and among species. Larger offspring of the sea anemone Urticina felina generally outperformed small siblings at the larval stage (i.e., greater settlement and survival rates under suboptimal conditions). However, results differed when analyses were conducted at the intrabrood versus across‐brood levels, suggesting that the relationship between larval size and performance is mediated by parentage. At the juvenile stage (15 months), small offspring were less susceptible than large ones to predation by subadult nudibranchs and both sizes performed similarly when facing adult nudibranchs. In a sympatric species with a different life history (Aulactinia stella), all juveniles suffered similar predation rates by subadult nudibranchs, but smaller juveniles performed better (lower mortalities) when facing adult nudibranchs. Size differences in premetamorphic performance of U. felina were linked to total lipid contents of larvae, whereas size‐specific predation of juvenile stages followed the general predictions of the optimal foraging strategy. These findings emphasize the challenge in gathering empirical support for a positive monotonic size–performance function in taxa that exhibit complex life cycles, which are dominant in the sea. 相似文献
10.