全文获取类型
收费全文 | 4854篇 |
免费 | 376篇 |
国内免费 | 1篇 |
出版年
2023年 | 20篇 |
2022年 | 41篇 |
2021年 | 103篇 |
2020年 | 46篇 |
2019年 | 66篇 |
2018年 | 95篇 |
2017年 | 81篇 |
2016年 | 140篇 |
2015年 | 240篇 |
2014年 | 216篇 |
2013年 | 328篇 |
2012年 | 390篇 |
2011年 | 346篇 |
2010年 | 243篇 |
2009年 | 197篇 |
2008年 | 272篇 |
2007年 | 290篇 |
2006年 | 269篇 |
2005年 | 259篇 |
2004年 | 211篇 |
2003年 | 241篇 |
2002年 | 203篇 |
2001年 | 91篇 |
2000年 | 78篇 |
1999年 | 72篇 |
1998年 | 54篇 |
1997年 | 32篇 |
1996年 | 17篇 |
1995年 | 33篇 |
1994年 | 26篇 |
1993年 | 22篇 |
1992年 | 41篇 |
1991年 | 36篇 |
1990年 | 33篇 |
1989年 | 28篇 |
1988年 | 25篇 |
1987年 | 31篇 |
1985年 | 26篇 |
1984年 | 28篇 |
1983年 | 24篇 |
1982年 | 17篇 |
1981年 | 18篇 |
1980年 | 13篇 |
1979年 | 15篇 |
1978年 | 21篇 |
1977年 | 15篇 |
1976年 | 12篇 |
1975年 | 11篇 |
1973年 | 18篇 |
1972年 | 12篇 |
排序方式: 共有5231条查询结果,搜索用时 718 毫秒
181.
182.
183.
184.
Pereira Felipe Walter Vitule Jean Ricardo Simões 《Reviews in Fish Biology and Fisheries》2019,29(3):639-652
Reviews in Fish Biology and Fisheries - Biological invasions via anthropogenic vectors, intentional or not, are one of the main causes of ecological change in aquatic ecosystems. Micropterus... 相似文献
185.
186.
Martyn Eliott Simon Lawson Andrew Hayes Valerie Debuse Alan York Tom Lewis 《Austral ecology》2019,44(4):609-620
Fire has a varied influence on plant and animal species through direct (e.g. fire‐induced mortality) and indirect (e.g. modification of habitat) effects. Our understanding of the influence of fire regime on invertebrates and their response to fire‐induced modifications to habitat is poor. We aimed to determine the response of a beetle family (Coleoptera: Cerambycidae) to varying fire treatments and hypothesised that the abundance of cerambycid beetles is influenced by fire frequency due to modifications in habitat associated with the fire treatments. Arthropods were sampled across 3 months in annually and triennially burnt areas (treatments starting in 1952 and 1973 respectively), an area unburnt since 1946, and a former unburnt treatment, burnt by wildfire in 2006. Eleven different cerambycid taxa were collected using flight intercept panel traps, dominated by three species (Ipomoria tillides, Adrium sp. and Bethelium signiferum) which made up 99% of individuals collected. Over the sampling period the long unburnt treatment had significantly lower species richness than the triennial and wildfire treatments. Cerambycid abundance was significantly higher in the triennially burnt treatment than in all other fire treatments. Ipomoria tillides was more abundant in both frequently burnt treatments, Adrium sp. was more common in triennially burnt areas, whereas B. signiferum, was more common in the wildfire affected treatment. Some, but not all, cerambycid beetles were more common in areas with a more open understorey (i.e. resulting from frequent burning), and lower tree basal area, as this likely influences their ability to fly easily between food sources. Cerambycid abundance was positively related to the volume of coarse woody debris and healthy tree crowns. Cerambycid beetles were clearly influenced by historic fire regime, suggesting that changes in fire regime can potentially have a profound influence on arthropod assemblages, and subsequent influences on ecosystem processes, which are currently poorly understood. 相似文献
187.
Amanda Rui En Woo Siu Kwan Sze Hwa Hwa Chung Valerie C-L Lin 《Biochimica et Biophysica Acta (BBA) - Gene Regulatory Mechanisms》2019,1862(4):522-533
The activation functions AF1 and AF2 of nuclear receptors mediate the recruitment of coregulators in gene regulation. AF1 is mapped to the highly variable and intrinsically unstructured N terminal domain and AF2 lies in the conserved ligand binding domain. The unstructured nature of AF1 offers structural plasticity and hence functional versatility in gene regulation. However, little is known about the key functional residues of AF1 that mediates its interaction with coregulators. This study focuses on the progesterone receptor (PR) and reports the identification of K464, K481 and R492 (KKR) as the key functional residues of PR AF1. The KKR are monomethylated and function cooperatively. The combined mutations of KKR to QQQ render PR isoform B (PRB) hyperactive, whereas KKR to FFF mutations abolishes as much as 80% of PR activity. Furthermore, the hyperactive QQQ mutation rescues the loss of PR activity due to E911A mutation in AF2. The study also finds that the magnitudes of the mutational effect differ in different cell types as a result of differential effects on the functional interaction with coregulators. Furthermore, KKR provides the interface for AF1 to physically interact with p300 and SRC-1, and with AF2 at E911. Intriguingly, the inactive FFF mutant interacts strikingly stronger with both SRC-1 and AF2 than wt PRB. We propose a tripartite model to describe the dynamic interactions between AF1, AF2 and SRC-1 with KKR of AF1 and E911 of AF2 as the interface. An overly stable interaction would hamper the dynamics of disassembly of the receptor complex. 相似文献
188.
Suresh Anand Sadananthan Mya Thway Tint Navin Michael Izzuddin M. Aris See Ling Loy Kuan Jin Lee Lynette Pei‐Chi Shek Fabian Kok Peng Yap Kok Hian Tan Keith M. Godfrey Melvin Khee‐Shing Leow Yung Seng Lee Michael S. Kramer Peter D. Gluckman Yap Seng Chong Neerja Karnani Christiani Jeyakumar Henry Marielle Valerie Fortier S. Sendhil Velan 《Obesity (Silver Spring, Md.)》2019,27(3):470-478
189.
The synthesis of chain-modified analogues of the naturally-occurring glycosidase inhibitor, salacinol, and its selenium analogue, blintol is described. The modification consists of a frame shift of the sulfate moiety by one carbon atom in the zwitterionic structures as well as an extension of the acyclic chain to five carbons. The target molecules were synthesized by alkylation of 1,4-anhydro-2,3,5-tri-O-p-methoxybenzyl-4-thio (or seleno)-D-arabinitol at the ring heteroatom by 2,3,5-tri-O-p-methoxybenzyl D- or L-xylitol-1,4-cyclic sulfate, followed by deprotection with trifluoroacetic acid. Two of the four compounds inhibit recombinant human maltase glucoamylase, one of the key intestinal enzymes involved in the breakdown of glucose oligosaccharides in the small intestine, with Ki values of 20+/-4 and 53+/-5 microM. 相似文献
190.