全文获取类型
收费全文 | 5002篇 |
免费 | 344篇 |
国内免费 | 1篇 |
出版年
2023年 | 22篇 |
2022年 | 50篇 |
2021年 | 153篇 |
2020年 | 90篇 |
2019年 | 95篇 |
2018年 | 149篇 |
2017年 | 116篇 |
2016年 | 154篇 |
2015年 | 224篇 |
2014年 | 289篇 |
2013年 | 357篇 |
2012年 | 411篇 |
2011年 | 432篇 |
2010年 | 253篇 |
2009年 | 234篇 |
2008年 | 284篇 |
2007年 | 328篇 |
2006年 | 300篇 |
2005年 | 252篇 |
2004年 | 233篇 |
2003年 | 224篇 |
2002年 | 192篇 |
2001年 | 40篇 |
2000年 | 32篇 |
1999年 | 32篇 |
1998年 | 39篇 |
1997年 | 27篇 |
1996年 | 16篇 |
1995年 | 35篇 |
1994年 | 25篇 |
1993年 | 31篇 |
1992年 | 20篇 |
1991年 | 14篇 |
1990年 | 20篇 |
1989年 | 15篇 |
1988年 | 12篇 |
1987年 | 9篇 |
1986年 | 12篇 |
1985年 | 13篇 |
1984年 | 15篇 |
1983年 | 9篇 |
1982年 | 13篇 |
1981年 | 11篇 |
1979年 | 9篇 |
1978年 | 5篇 |
1977年 | 9篇 |
1976年 | 7篇 |
1975年 | 6篇 |
1972年 | 4篇 |
1970年 | 7篇 |
排序方式: 共有5347条查询结果,搜索用时 15 毫秒
991.
Salvia madrigalii is described and illustrated as a new species to science. It is known for the municipality of Morelia, in the north central region of Michoacán, Mexico. It is one of the few Mexican species with 2 flowers per verticillaster and white corollas. We included line drawings, photographs of the plant and a distribution map. In addition, its relationships with the related species are discussed. 相似文献
992.
993.
994.
995.
996.
Julio C. Cristaldi María C. Gómez Pablo J. González Felix M. Ferroni Sergio D. Dalosto Alberto C. Rizzi María G. Rivas Carlos D. Brondino 《Biochimica et Biophysica Acta (BBA)/General Subjects》2018,1862(3):752-760
The Cys-His bridge as electron transfer conduit in the enzymatic catalysis of nitrite to nitric oxide by nitrite reductase from Sinorhizobium meliloti 2011 (SmNir) was evaluated by site-directed mutagenesis, steady state kinetic studies, UV–vis and EPR spectroscopic measurements as well as computational calculations. The kinetic, structural and spectroscopic properties of the His171Asp (H171D) and Cys172Asp (C172D) SmNir variants were compared with the wild type enzyme. Molecular properties of H171D and C172D indicate that these point mutations have not visible effects on the quaternary structure of SmNir. Both variants are catalytically incompetent using the physiological electron donor pseudoazurin, though C172D presents catalytic activity with the artificial electron donor methyl viologen (kcat = 3.9(4) s? 1) lower than that of wt SmNir (kcat = 240(50) s? 1). QM/MM calculations indicate that the lack of activity of H171D may be ascribed to the Nδ1H…OC hydrogen bond that partially shortcuts the T1–T2 bridging Cys-His covalent pathway. The role of the Nδ1H…OC hydrogen bond in the pH-dependent catalytic activity of wt SmNir is also analyzed by monitoring the T1 and T2 oxidation states at the end of the catalytic reaction of wt SmNir at pH 6 and 10 by UV–vis and EPR spectroscopies. These data provide insight into how changes in Cys-His bridge interrupts the electron transfer between T1 and T2 and how the pH-dependent catalytic activity of the enzyme are related to pH-dependent structural modifications of the T1–T2 bridging chemical pathway. 相似文献
997.
998.
999.
Carlos Alberto dos Santos Souza Jarbas Marçal Queiroz Mauro Sergio Cruz Souza Lima Jonas Pederassi 《Acta ethologica》2018,21(2):81-89
Sphex ingens is one of 30 species in the family Sphecidae that occur in the state of Rio de Janeiro. However, details of the behavior and sexual selection of natural populations of this wasp species have only recently been unveiled. In addition, the knowledge of its ecology is still poor. This is the first study on the feeding behavior interactions between S. ingens and prey captured to feed its larvae. Paralyzed prey were collected manually at the sites of wasp nests on Aventureiro Beach, Ilha Grande, Brazil during the provisioning activity of marked female S. ingens. All prey were preserved, their sex and sexual maturity were determined, and they were identified to the lowest possible taxonomic level. The body mass and size of the prey and female wasps were measured. Sphex ingens females captured only Pleminia vicina and Meroncidius sp. The body masses of wasps and katydids were positively correlated. The body mass of captured katydids was significantly dependent on the wasp’s wing length. Most of the prey were adult females, but the differences did not confirm possible preferences, as those values can be related to differences in the distribution and fluctuation in the population density of prey species and to the individual foraging strategies of female wasps. However, the predisposition to predatory specialization exhibited by S. ingens populations in Ilha Grande and elsewhere suggests that this interaction can be an important source of mortality for populations of pseudophylline katydid species. 相似文献
1000.
Adrian P. Mansini Estanislao Peixoto Kristen M. Thelen Cesar Gaspari Sujeong Jin Sergio A. Gradilone 《生物化学与生物物理学报:疾病的分子基础》2018,1864(4):1245-1253
Cholangiocytes, like most cells, express primary cilia extending from their membranes. These organelles function as antennae which detect stimuli from bile and transmit the information into cells regulating several signaling pathways involved in secretion, proliferation and apoptosis. The ability of primary cilia to detect different signals is provided by ciliary associated proteins which are expressed in its membrane. Defects in the structure and/or function of these organelles lead to cholangiociliopathies that result in cholangiocyte hyperproliferation, altered fluid secretion and absorption. Since primary cilia dysfunction has been observed in several epithelial tumors, including cholangiocarcinoma (CCA), primary cilia have been proposed as tumor suppressor organelles. In addition, the loss of cilia is associated with dysregulation of several molecular pathways resulting in CCA development and progression. Thus, restoration of the primary cilia may be a potential therapeutic approach for several ciliopathies and CCA. 相似文献