全文获取类型
收费全文 | 760篇 |
免费 | 49篇 |
出版年
2023年 | 7篇 |
2022年 | 8篇 |
2021年 | 18篇 |
2020年 | 10篇 |
2019年 | 20篇 |
2018年 | 29篇 |
2017年 | 26篇 |
2016年 | 42篇 |
2015年 | 33篇 |
2014年 | 47篇 |
2013年 | 78篇 |
2012年 | 49篇 |
2011年 | 44篇 |
2010年 | 34篇 |
2009年 | 25篇 |
2008年 | 24篇 |
2007年 | 20篇 |
2006年 | 25篇 |
2005年 | 10篇 |
2004年 | 14篇 |
2003年 | 14篇 |
2002年 | 9篇 |
2001年 | 4篇 |
2000年 | 12篇 |
1999年 | 11篇 |
1998年 | 7篇 |
1997年 | 6篇 |
1996年 | 10篇 |
1995年 | 9篇 |
1994年 | 5篇 |
1993年 | 10篇 |
1992年 | 17篇 |
1991年 | 8篇 |
1990年 | 7篇 |
1989年 | 10篇 |
1988年 | 11篇 |
1987年 | 5篇 |
1985年 | 7篇 |
1984年 | 4篇 |
1982年 | 3篇 |
1980年 | 6篇 |
1977年 | 6篇 |
1976年 | 7篇 |
1975年 | 3篇 |
1973年 | 3篇 |
1971年 | 3篇 |
1970年 | 4篇 |
1968年 | 3篇 |
1967年 | 3篇 |
1917年 | 5篇 |
排序方式: 共有809条查询结果,搜索用时 15 毫秒
801.
Prakash Bhuta Jiří Žemclička 《Biochimica et Biophysica Acta (BBA)/General Subjects》1985,841(2):145-150
The (1c) and (2c), obtained by chemical synthesis, are substrates for ribosomal peptidyltransferase from Escherichia coli. Nucleoside 1c, which mimics an anti conformation of antibiotic formycin, has 80% of the acceptor activity of puromycin at 5 · 10?4 M determined by the release of N-Ac-Phe residue from the 70 S complex. The reaction product, (1d), was characterized by paper electrophoresis before and after alkaline hydrolysis. By contrast, nucleoside 2c, which resembles a syn conformation of formycin, exhibited only 20% of the acceptor activity of puromycin at 5 · 10∮4 M and essentially none in the concentration region between 1 · 10?6 and 1 · 10?4 M. The results which are in accord with previous models have shown that a substrate with its base in an anti conformation is preferable for the acceptor site of peptidyltransferase than the corresponding syn counterpart, Nevertheless, it is possible that an intermediate conformation, for example, high anti (amphi-minus), is an optimal arrangement for acceptor site substrates. 相似文献
802.
803.
804.
805.
806.
807.
Dialectical Anthropology - There is an ongoing debate in anthropology on the kinds of subject positions activists ascribe to the marginalized actors they encounter and the political consequences... 相似文献
808.
We have developed an animal model of hyperammonemia consisting of feeding rats a diet containing 20% (w/w) ammonium acetate. Ingestion of this diet markedly affects carcass composition, with a 46% reduction in lipid content. The ammonium diet alters levels of several key compounds involved in lipid metabolism. Long-chain acylcarnitine is increased in liver by approx. 60% while free carnitine and acetylcarnitine are unaffected. The hepatic content of acetyl-CoA increases by approx. 50%. The level of ketone bodies in blood increases by 32% but remains unchanged in liver. Our data indicate that hyperammonemia alters lipid metabolism and results in a significant decrease in body lipid content. 相似文献
809.
The paper deals with the effect of the application of certain ions (Zn2+, B4O7 2- Mn2+, Cu2+, MoO4 2-,) on the development of the activity displayed by amylase, urease, and glutamate-oxalacetate (GOT) in hydroponically cultivated barley during the first seven days of ontogenesis. The enzymes were studied separately in the overground and root parts of the plants. The following main conclusions can be drawn from the findings made: The amylase activity of the control plants in connection with their development diminished slightly in the overground part, while it was relatively constant in the roots. Due to the effect of certain elements tested, this activity increased pronouncedly (significant differences were confirmed in variants containing MoO4 2-, Zn2+, and Co2+). The urease level in the overground part of the control plants remained low throughout the entire experimental period and was only little influenced by the individual microelements under study (with the exception of B4O7 2-). On the other hand, the urease activity in the root system increased markedly, the B4O7 2- ions exhibiting a significantly stimulating effect. The activity of glutamate-oxalacetate transaminase (GOT) in the overground part of the control plants increased only slightly in the course of the initial development, while in the root system it grew relatively more pronouncedly. In the overground part of the plants all the microelements administered displayed a significantly depressive effect on the development of this enzyme activity; in the roots, the inhibitory action was maintained only in the last experimental period in variants with Zn2+ ions. 相似文献