全文获取类型
收费全文 | 3010篇 |
免费 | 284篇 |
出版年
2023年 | 24篇 |
2022年 | 55篇 |
2021年 | 91篇 |
2020年 | 67篇 |
2019年 | 64篇 |
2018年 | 86篇 |
2017年 | 64篇 |
2016年 | 116篇 |
2015年 | 197篇 |
2014年 | 205篇 |
2013年 | 269篇 |
2012年 | 318篇 |
2011年 | 247篇 |
2010年 | 184篇 |
2009年 | 162篇 |
2008年 | 156篇 |
2007年 | 168篇 |
2006年 | 140篇 |
2005年 | 107篇 |
2004年 | 89篇 |
2003年 | 89篇 |
2002年 | 51篇 |
2001年 | 19篇 |
2000年 | 21篇 |
1999年 | 18篇 |
1998年 | 7篇 |
1997年 | 11篇 |
1996年 | 11篇 |
1995年 | 7篇 |
1993年 | 8篇 |
1992年 | 25篇 |
1991年 | 11篇 |
1990年 | 13篇 |
1989年 | 10篇 |
1988年 | 12篇 |
1987年 | 13篇 |
1986年 | 14篇 |
1985年 | 14篇 |
1984年 | 9篇 |
1983年 | 11篇 |
1982年 | 8篇 |
1981年 | 9篇 |
1980年 | 8篇 |
1979年 | 8篇 |
1978年 | 9篇 |
1977年 | 5篇 |
1976年 | 5篇 |
1975年 | 9篇 |
1972年 | 6篇 |
1971年 | 5篇 |
排序方式: 共有3294条查询结果,搜索用时 31 毫秒
991.
Julien Farard Gaëtan Lanceart Cedric Logé Marie-Renée Nourrisson Francisco Cruzalegui Bruno Pfeiffer 《Journal of enzyme inhibition and medicinal chemistry》2013,28(5):629-640
Src family kinases (SFKs) are nonreceptor tyrosine kinases that are reported to be critical for cancer progression. Inhibiting the catalytic activity of these proteins has become one of the major therapeutic concepts in contemporary drug discovery. We report here the design and the synthesis of novel 6-substituted-5-benzyloxy-4-oxo-4H-pyran-2-carboxamides as potential inhibitors of Src kinase. The synthesis of these derivatives and the preliminary results of biological activity will be discussed. 相似文献
992.
993.
Avigliano Esteban Pisonero Jorge Bouchez Julien Pouilly Marc Domanico Alejandro Sánchez Sebastian Clavijo Cristhian Scarabotti Pablo Facetti Juan F. Caffetti Jacqueline D. del Rosso Franco R. Llamazares Vegh Sabina Volpedo Alejandra V. 《Environmental Biology of Fishes》2021,104(3):277-292
Environmental Biology of Fishes - The potential use of Sr/Ca and Ba/Ca ratios in fish otolith, as a complement to 87Sr/86Sr to study movements of Prochilodus lineatus, was evaluated in the La Plata... 相似文献
994.
Hiraku Takada Mohammad Roghanian Julien Caballero-Montes Katleen Van
Nerom Steffi Jimmy Pavel Kudrin Fabio Trebini Rikinori Murayama Genki Akanuma Abel Garcia-Pino Vasili Hauryliuk 《Nucleic acids research》2021,49(1):444
In the Gram-positive Firmicute bacterium Bacillus subtilis, amino acid starvation induces synthesis of the alarmone (p)ppGpp by the RelA/SpoT Homolog factor Rel. This bifunctional enzyme is capable of both synthesizing and hydrolysing (p)ppGpp. To detect amino acid deficiency, Rel monitors the aminoacylation status of the ribosomal A-site tRNA by directly inspecting the tRNA’s CCA end. Here we dissect the molecular mechanism of B. subtilis Rel. Off the ribosome, Rel predominantly assumes a ‘closed’ conformation with dominant (p)ppGpp hydrolysis activity. This state does not specifically select deacylated tRNA since the interaction is only moderately affected by tRNA aminoacylation. Once bound to the vacant ribosomal A-site, Rel assumes an ‘open’ conformation, which primes its TGS and Helical domains for specific recognition and stabilization of cognate deacylated tRNA on the ribosome. The tRNA locks Rel on the ribosome in a hyperactivated state that processively synthesises (p)ppGpp while the hydrolysis is suppressed. In stark contrast to non-specific tRNA interactions off the ribosome, tRNA-dependent Rel locking on the ribosome and activation of (p)ppGpp synthesis are highly specific and completely abrogated by tRNA aminoacylation. Binding pppGpp to a dedicated allosteric site located in the N-terminal catalytic domain region of the enzyme further enhances its synthetase activity. 相似文献
995.
996.
Stefania Viola Julien Sellés Benjamin Bailleul Pierre Joliot Francis-André Wollman 《BBA》2021,1862(9):148449
Many cyanobacteria species can use both plastocyanin and cytochrome c6 as lumenal electron carriers to shuttle electrons from the cytochrome b6f to either photosystem I or the respiratory cytochrome c oxidase. In Synechocystis sp. PCC6803 placed in darkness, about 60% of the active PSI centres are bound to a reduced electron donor which is responsible for the fast re-reduction of P700 in vivo after a single charge separation. Here, we show that both cytochrome c6 and plastocyanin can bind to PSI in the dark and participate to the fast phase of P700 reduction, but the fraction of pre-bound PSI is smaller in the case of cytochrome c6 than with plastocyanin. Because of the inter-connection of respiration and photosynthesis in cyanobacteria, the inhibition of the cytochrome c oxidase results in the over-reduction of the photosynthetic electron transfer chain in the dark that translates into a lag in the kinetics of P700 oxidation at the onset of light. We show that this is true both with plastocyanin and cytochrome c6, indicating that the partitioning of electron transport between respiration and photosynthesis is regulated in the same way independently of which of the two lumenal electron carriers is present, although the mechanisms of such regulation are yet to be understood. 相似文献
997.
998.
Alexandra H. M. Jebb Daniel T. Blumstein Pierre Bize Julien G. A. Martin 《Ecology and evolution》2021,11(7):3435
Body mass is often viewed as a proxy of past access to resources and of future survival and reproductive success. Links between body mass and survival or reproduction are, however, likely to differ between age classes and sexes. Remarkably, this is rarely taken into account in selection analyses. Selection on body mass is likely to be the primary target accounting for juvenile survival until reproduction but may weaken after recruitment. Males and females also often differ in how they use resources for reproduction and survival. Using a long‐term study on body mass and annual survival in yellow‐bellied marmots (Marmota flaviventer), we show that body mass was under stabilizing viability selection in the first years of life, before recruitment, which changed to positive directional selection as age increased and animals matured. We found no evidence that viability selection across age classes on body mass differed between sexes. By investigating the link between running speed and body mass, we show that the capacity to escape predators was not consistent across age classes and followed a quadratic relationship at young ages only. Overall, our results indicate that mature age classes exhibit traditional patterns of positive viability selection on body mass, as expected in a hibernating mammal, but that mass in the first years of life is subjected to stabilizing selection which may come from additional predation pressures that negate the benefits of the largest body masses. Our study highlights the importance to disentangle selection pressures on traits across critical age (or life) classes. 相似文献
999.
1000.
Lefevre S Huong do TT Wang T Phuong NT Bayley M 《Comparative biochemistry and physiology. Part A, Molecular & integrative physiology》2011,158(2):207-214
Air-breathing fish are common in the tropics, and their importance in Asian aquaculture is increasing, but the respiratory physiology of some of the key species such as the striped catfish, Pangasianodon hypophthalmus Sauvage 1878 is unstudied. P. hypophthalmus is an interesting species as it appears to possess both well-developed gills and a modified swim bladder that functions as an air-breathing organ indicating a high capacity for both aquatic and aerial respiration. Using newly developed bimodal intermittent-closed respirometry, the partitioning of oxygen consumption in normoxia and hypoxia was investigated in P. hypophthalmus. In addition the capacity for aquatic breathing was studied through measurements of oxygen consumption when access to air was denied, both in normoxia and hypoxia, and the critical oxygen tension, Pcrit, was also determined during these experiments. Finally, gill ventilation and air-breathing frequency were measured in a separate experiment with pressure measurements from the buccal cavity. The data showed that P. hypophthalmus is able to maintain standard metabolic rate (SMR) through aquatic breathing alone in normoxia, but that air-breathing is important during hypoxia. Gill ventilation was reduced during air-breathing, which occurred at oxygen levels below 8 kPa, coinciding with the measured Pcrit of 7.7 kPa. The findings in this study indicate that the introduction of aeration into the aquaculture of P. hypophthalmus could potentially reduce the need to air-breathe. The possibility of reducing air-breathing frequency may be energetically beneficial for the fish, leaving more of the aerobic scope for growth and other activities, due to the proposed energetic costs of surfacing behavior. 相似文献