全文获取类型
收费全文 | 1506篇 |
免费 | 100篇 |
国内免费 | 1篇 |
出版年
2024年 | 2篇 |
2023年 | 12篇 |
2022年 | 20篇 |
2021年 | 54篇 |
2020年 | 27篇 |
2019年 | 30篇 |
2018年 | 43篇 |
2017年 | 34篇 |
2016年 | 55篇 |
2015年 | 97篇 |
2014年 | 98篇 |
2013年 | 134篇 |
2012年 | 126篇 |
2011年 | 123篇 |
2010年 | 74篇 |
2009年 | 52篇 |
2008年 | 88篇 |
2007年 | 109篇 |
2006年 | 102篇 |
2005年 | 68篇 |
2004年 | 62篇 |
2003年 | 60篇 |
2002年 | 49篇 |
2001年 | 12篇 |
2000年 | 7篇 |
1999年 | 6篇 |
1998年 | 6篇 |
1997年 | 9篇 |
1996年 | 10篇 |
1995年 | 8篇 |
1994年 | 7篇 |
1993年 | 1篇 |
1992年 | 4篇 |
1991年 | 1篇 |
1990年 | 2篇 |
1989年 | 2篇 |
1987年 | 1篇 |
1985年 | 2篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1981年 | 1篇 |
1980年 | 3篇 |
1978年 | 2篇 |
1976年 | 1篇 |
排序方式: 共有1607条查询结果,搜索用时 15 毫秒
11.
Svetlana E. Koshlukova Albena B. Momchilova-Pankova Tania T. Markovska Kamen S. Koumanov 《The Journal of membrane biology》1992,127(2):113-119
Summary Investigations were performed on the influence of the phospholipid composition and physicochemical properties of the rat liver microsomal membranes on acyl-CoA synthetase and acyl-CoA : 1-acyl-sn-glycero-3-phosphocholine O-acyltransferase activities. The phospholipid composition of the membranes was modified by incubation with different phospholipids in the presence of lipid transfer proteins or by partial delipidation with exogenous phospholipase C and subsequent enrichment with phospholipids. The results indicated that the incorporation of phosphatidylglycerol, phosphatidylserine and phosphatidylethanolamine induced a marked activation of acyl-CoA synthetase for both substrates used—palmitic and oleic acids. Sphingomyelin occurred as specific inhibitor for this activity especially for palmitic acid. Palmitoyl-CoA: and oleoyl-CoA : lacyl-sn-glycero-3-phosphocholine acyltransferase activities were found to depend on the physical state of the membrane lipids. The alterations in the membrane physical state were estimated using two different fluorescent probes—1,6-diphenyl-1,3,5-hexatriene and pyrene. In all cases of membrane fluidization this activity was elevated. On the contrary, in more rigid membranes obtained by incorporation of sphingomyelin and dipalmitoylphosphatidylcholine, acyltransferase activity was reduced for both palmitoyl-CoA and oleoyl-CoA. We suggest a certain similarity in the way of regulation of membrane-bound acyltransferase and phospholipase A2 which both participate in the deacylation-reacylation cycle. 相似文献
12.
G. Simoni M. Fraccaro A. Arslanian M. Bacchetta C. Baccichetti F. A. Bignone A. Cagiano A. O. Carbonara F. Carozzi C. Cuoco F. Dagna Bricarelli B. Dallapiccola L. Dalprà L. Doria Lamba Carbone G. Ferranti G. Filippi M. Frateschi G. Gimelli R. M. Gualtieri E. Lenzini G. Micara N. Migone V. Montacuti G. Neri R. Papa V. Pecile M. Rocchi E. Savin A. Serra R. Tenconi G. L. Terzoli M. G. Tibiletti 《Human genetics》1982,60(1):63-68
Summary The development of prenatal diagnosis in Italy was made difficult by the restrictions of the old abortion law and only in recent years has a consistent number of cases been investigated. We report the experience on prenatal chromosome diagnosis of ten Italian centers participating in a collaborative study on 4952 diagnoses performed from 1972 to 1980. The main indication groups were: advanced maternal age (2882 cases), previous child with chromosome anomaly from parents with normal karyotype (847 cases), and chromosome anomaly in one parent (97 cases). The other indications for amniocentesis, including cases without a cytogenetic risk, have been assembled into a miscellaneous group (1126 cases). We found 125 abnormal fetal karyotypes (2.5%) of which 89 were unbalanced (1.8%). The frequencies and types of chromosome anomalies are reported in detail for each indication group and are compared with the corresponding ones from the European Munich Conference. The great majority of these Italian data were not included in the Munich report. 相似文献
13.
Xylose anaerobic conversion by open-mixed cultures 总被引:1,自引:0,他引:1
Margarida F. Temudo Tania Mato Robbert Kleerebezem Mark C. M. van Loosdrecht 《Applied microbiology and biotechnology》2009,82(2):231-239
Xylose is, after glucose, the dominant sugar in agricultural wastes. In anaerobic environments, carbohydrates are converted
into volatile fatty acids and alcohols. These can be used as building blocks in biotechnological or chemical processes, e.g.,
to produce bioplastics. In this study, xylose fermentation by mixed microbial cultures was investigated and compared with
glucose under the same conditions. The product spectrum obtained with both substrates was comparable. It was observed that,
in the case of xylose, a higher fraction of the carbon was converted into catabolic products (butyrate, acetate, and ethanol)
and the biomass yield was approximately 20% lower than on glucose, 0.16 versus 0.21 Cmol X/Cmol S. This lower yield is likely
related to the need of an extra ATP during xylose uptake. When submitted to a pulse of glucose, the population cultivated
on xylose could instantaneously convert the glucose. No substrate preference was observed when glucose and xylose were fed
simultaneously to the continuously operated bioreactor. 相似文献
14.
15.
16.
Kathleen M. Kay Tania Jogesh Diana Tataru Sami Akiba 《Proceedings. Biological sciences / The Royal Society》2020,287(1941)
Heteranthery, the presence of two or more anther types in the same flower, is taxonomically widespread among bee-pollinated angiosperms, yet has puzzled botanists since Darwin. We test two competing hypotheses for its evolution: the long-standing ‘division of labour'' hypothesis, which posits that some anthers are specialized as food rewards for bees whereas others are specialized for surreptitious pollination, and our new hypothesis that heteranthery is a way to gradually release pollen that maximizes pollen delivery. We examine the evolution of heteranthery and associated traits across the genus Clarkia (Onagraceae) and study plant–pollinator interactions in two heterantherous Clarkia species. Across species, heteranthery is associated with bee pollination, delayed dehiscence and colour crypsis of one anther whorl, and movement of that anther whorl upon dehiscence. Our mechanistic studies in heterantherous species show that bees notice, forage on and export pollen from each anther whorl when it is dehiscing, and that heteranthery promotes pollen export. We find no support for division of labour, but multifarious evidence that heteranthery is a mechanism for gradual pollen presentation that probably evolved through indirect male–male competition for siring success. 相似文献
17.
Coral Reefs - Structural complexity provided by the living coral reef framework is the basis of the rich and dynamic biodiversity in coral reefs. In many cases today, the reduction in habitat... 相似文献
18.
19.
20.
The Protein Journal - Expression of recombinant proteins requires at times the aid of molecular chaperones for efficient post-translational folding into functional structure. However, predicting... 相似文献