全文获取类型
收费全文 | 684篇 |
免费 | 67篇 |
专业分类
751篇 |
出版年
2019年 | 5篇 |
2018年 | 7篇 |
2016年 | 8篇 |
2015年 | 17篇 |
2014年 | 18篇 |
2013年 | 23篇 |
2012年 | 20篇 |
2011年 | 24篇 |
2010年 | 20篇 |
2009年 | 19篇 |
2008年 | 23篇 |
2007年 | 25篇 |
2006年 | 28篇 |
2005年 | 17篇 |
2004年 | 17篇 |
2003年 | 30篇 |
2002年 | 10篇 |
2001年 | 17篇 |
2000年 | 20篇 |
1999年 | 21篇 |
1998年 | 6篇 |
1997年 | 8篇 |
1996年 | 12篇 |
1995年 | 13篇 |
1994年 | 6篇 |
1993年 | 7篇 |
1992年 | 28篇 |
1991年 | 21篇 |
1990年 | 18篇 |
1989年 | 22篇 |
1988年 | 10篇 |
1987年 | 10篇 |
1986年 | 12篇 |
1985年 | 17篇 |
1984年 | 11篇 |
1982年 | 8篇 |
1981年 | 18篇 |
1980年 | 16篇 |
1979年 | 12篇 |
1978年 | 13篇 |
1977年 | 11篇 |
1976年 | 9篇 |
1975年 | 7篇 |
1974年 | 5篇 |
1973年 | 11篇 |
1972年 | 9篇 |
1971年 | 12篇 |
1970年 | 6篇 |
1969年 | 7篇 |
1968年 | 5篇 |
排序方式: 共有751条查询结果,搜索用时 15 毫秒
31.
Evidence is presented indicating that intact plants of Hordeum vulgare degrade [α- 14C]hordenine to 14CO 2. 相似文献
32.
33.
34.
R. Breton M. Fiszman F. Gros 《Biochemical and biophysical research communications》1980,95(1):281-288
Proteins synthesized by cardiocytes isolated from 11d embryonic hearts and cultured have been compared with proteins present in the 11d embryonic heart. It is shown that cultured cardiocytes synthesize two new proteins, C1 and C2 with a molecular weight of 27 500 and pI of 6.35 and 6.05 respectively. The synthesis of these proteins is associated with the appearance of new RNA species. This induction is not related to the conditions of culture since it occurs with either aggregated cardioacytes grown in suspension or cardiocytes grown in monolayer. Finally no other embryonic cell types seem to synthesize these proteins. 相似文献
35.
36.
Justine Thubaut Laure Corbari Olivier Gros Sébastien Duperron Arnaud Couloux Sarah Samadi 《PloS one》2013,8(7)
The giant bathymodioline mussels from vents have been studied as models to understand the adaptation of organisms to deep-sea chemosynthetic environments. These mussels are closely related to minute mussels associated to organic remains decaying on the deep-sea floor. Whereas biological data accumulate for the giant mussels, the small mussels remain poorly studied. Despite this lack of data for species living on organic remains it has been hypothesized that during evolution, contrary to their relatives from vents or seeps, they did not acquire highly specialized biological features. We aim at testing this hypothesis by providing new biological data for species associated with organic falls. Within Bathymodiolinae a close phylogenetic relationship was revealed between the Bathymodiolus sensu stricto lineage (i.e. “thermophilus” lineage) which includes exclusively vent and seep species, and a diversified lineage of small mussels, attributed to the genus Idas, that includes mostly species from organic falls. We selected Idas iwaotakii (Habe, 1958) from this latter lineage to analyse population structure and to document biological features. Mitochondrial and nuclear markers reveal a north-south genetic structure at an oceanic scale in the Western Pacific but no structure was revealed at a regional scale or as correlated with the kind of substrate or depth. The morphology of larval shells suggests substantial dispersal abilities. Nutritional features were assessed by examining bacterial diversity coupled by a microscopic analysis of the digestive tract. Molecular data demonstrated the presence of sulphur-oxidizing bacteria resembling those identified in other Bathymodiolinae. In contrast with most Bathymodiolus s.s. species the digestive tract of I. iwaotakii is not reduced. Combining data from literature with the present data shows that most of the important biological features are shared between Bathymodiolus s.s. species and its sister-lineage. However Bathymodiolus s.s. species are ecologically more restricted and also display a lower species richness than Idas species. 相似文献
37.
L Cordeau-Lossouarn J L Vayssière J C Larcher F Gros B Croizat 《Biology of the cell / under the auspices of the European Cell Biology Organization》1991,71(1-2):57-65
The evolution of the mitochondrion has been followed within differentiating neuronal cells, both in primary cultures of neurons from fetal rat cortex and during rat brain cortex maturation. Changes in total mitochondrial proteins (mt-proteins) were evaluated, and qualitative changes in the mt-proteins pattern were analyzed using the Western blot technique. The evolution of mt-protein contents in cultured neurons resembles what is observed during rat brain maturation. The mitochondrion exhibits pronounced changes in the course of neurogenesis, in particular, bursts of mitochondrial masses accompanying the successive steps of neurogenesis are observed. There are indications that protein equipment of mitochondria during neuronal development undergoes variations. Although more work is required to establish the significance of these correlations, the present data might suggest an important role of the mitochondrion in neurogenesis. 相似文献
38.
The expression of cytolytic activity and production of interferon gamma (IFN-gamma) by CD8(+) T cells is thought to play a fundamental role in protection against infection by viruses and intracellular parasites. Fran?ois Erard and Graham Le Gros have recently shown that CD8(+) T cells activated in the presence of interleukin 4 (IL-4) can switch development to a CD8(-)CD4(-)Th2-like phenotype that is not cytolytic and that does not produce IFN-gamma. Here they speculate on whether this IL-4-induced switch is used by the host to make a more-effective response against parasite invasion, or i f it is a host mechanism used by the parasite to evade protective CD8(+) T-cell responses. 相似文献
39.
Orelle C Dalmas O Gros P Di Pietro A Jault JM 《The Journal of biological chemistry》2003,278(47):47002-47008
ATP-binding cassette (ABC) proteins constitute one of the widest families in all organisms, whose P-glycoprotein involved in resistance of cancer cells to chemotherapy is an archetype member. Although three-dimensional structures of several nucleotide-binding domains of ABC proteins are now available, the catalytic mechanism triggering the functioning of these proteins still remains elusive. In particular, it has been postulated that ATP hydrolysis proceeds via an acid-base mechanism catalyzed by the Glu residue adjacent to the Walker-B motif (Geourjon, C., Orelle, C., Steinfels, E., Blanchet, C., Deléage, G., Di Pietro, A., and Jault, J. M. (2001) Trends Biochem. Sci. 26, 539-544), but the involvement of such residue as the catalytic base in ABC transporters was recently questioned (Sauna, Z. E., Muller, M., Peng, X. H., and Ambudkar, S. V. (2002) Biochemistry, 41, 13989-14000). The equivalent glutamate residue (Glu504) of a half-ABC transporter involved in multidrug resistance in Bacillus subtilis, BmrA (formerly known as YvcC), was therefore mutated to Asp, Ala, Gln, Ser, and Cys residues. All these mutants were fully devoid of ATPase activity, yet they showed a high level of vanadate-independent trapping of 8-N3-alpha-32P-labeled nucleotide(s), following preincubation with 8-N3-[alpha-32P]ATP. However, and in contrast to the wild-type enzyme, the use of 8-N3-[gamma-32P]ATP unequivocally showed that all the mutants trapped exclusively the triphosphate form of the analogue, suggesting that they were not able to perform even a single hydrolytic turnover. These results demonstrate that Glu504 is the catalytic base for ATP hydrolysis in BmrA, and it is proposed that equivalent glutamate residues in other ABC transporters play the same role. 相似文献
40.
In the nucleotide-binding domains (NBDs) of ABC transporters, such as mouse Mdr3 P-glycoprotein (P-gp), an invariant carboxylate residue (E552 in NBD1; E1197 in NBD2) immediately follows the Walker B motif (hyd(4)DE/D). Removal of the negative charge in mutants E552Q and E1197Q abolishes drug-stimulated ATPase activity measured by P(i) release. Surprisingly, drug-stimulated trapping of 8-azido-[alpha-(32)P]ATP is still observed in the mutants in both the presence and absence of the transition-state analogue vanadate (V(i)), and ADP can be recovered from the trapped enzymes. The E552Q and E1197Q mutants show characteristics similar to those of the wild-type (WT) enzyme with respect to 8-azido-[alpha-(32)P]ATP binding and 8-azido-[alpha-(32)P]nucleotide trapping, with the latter being both Mg(2+) and temperature dependent. Importantly, drug-stimulated nucleotide trapping in E552Q is stimulated by V(i) and resembles the WT enzyme, while it is almost completely V(i) insensitive in E1197Q. Similar nucleotide trapping properties are observed when aluminum fluoride or beryllium fluoride is used as an alternate transition-state analogue. Partial proteolytic cleavage of photolabeled enzymes indicates that, in the absence of V(i), nucleotide trapping occurs exclusively at the mutant NBD, whereas in the presence of V(i), nucleotide trapping occurs at both NBDs. Together, these results suggest that there is single-site turnover occurring in the E552Q and E1197Q mutants and that ADP release from the mutant site, or another catalytic step, is impaired in these mutants. Furthermore, our results support a model in which the two NBDs of P-gp are not functionally equivalent. 相似文献