全文获取类型
收费全文 | 2321篇 |
免费 | 149篇 |
国内免费 | 2篇 |
出版年
2023年 | 9篇 |
2022年 | 32篇 |
2021年 | 41篇 |
2020年 | 44篇 |
2019年 | 41篇 |
2018年 | 55篇 |
2017年 | 45篇 |
2016年 | 70篇 |
2015年 | 103篇 |
2014年 | 116篇 |
2013年 | 158篇 |
2012年 | 156篇 |
2011年 | 185篇 |
2010年 | 101篇 |
2009年 | 94篇 |
2008年 | 145篇 |
2007年 | 142篇 |
2006年 | 132篇 |
2005年 | 113篇 |
2004年 | 87篇 |
2003年 | 98篇 |
2002年 | 68篇 |
2001年 | 29篇 |
2000年 | 27篇 |
1999年 | 34篇 |
1998年 | 26篇 |
1997年 | 17篇 |
1996年 | 17篇 |
1995年 | 13篇 |
1994年 | 23篇 |
1993年 | 11篇 |
1992年 | 11篇 |
1991年 | 16篇 |
1990年 | 15篇 |
1989年 | 12篇 |
1987年 | 12篇 |
1986年 | 11篇 |
1985年 | 10篇 |
1984年 | 9篇 |
1983年 | 12篇 |
1982年 | 9篇 |
1981年 | 6篇 |
1980年 | 12篇 |
1979年 | 7篇 |
1978年 | 9篇 |
1977年 | 11篇 |
1976年 | 11篇 |
1975年 | 13篇 |
1974年 | 8篇 |
1973年 | 9篇 |
排序方式: 共有2472条查询结果,搜索用时 31 毫秒
41.
Steroidogenesis in isolated adrenocortical cells. Correlation with receptor-bound adenosine 3′:5′-cyclic monophosphate
下载免费PDF全文
![点击此处可从《The Biochemical journal》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Ernesto J. Podesta Alfred Milani Hans Steffen Robert Neher 《The Biochemical journal》1979,180(2):355-363
Because several groups have recently questioned a mediating role for cyclic AMP in adrenocortical steroidogenesis, we analysed the problem in more detail by measuring three different cyclic AMP pools in cells isolated from decapsulated rat adrenals. Extra-cellular, total intracellular and bound intracellular cyclic AMP were determined by radioimmunoassay in comparison with corticosterone production induced by low corticotropin concentrations. The increase in extracellular and total intracellular cyclic AMP with low corticotropin concentrations was dependent on the presence of a phosphodiesterase inhibitor and short incubation times. Bound intracellular cyclic AMP was less dependent on these two parameters. In unstimulated cells cyclic AMP bound to its receptor represents only a small fraction of the total intracellular cyclic AMP. After stimulation by a concentration of corticotropin around the threshold for corticosterone production, an increase in bound cyclic AMP was observed which correlated very well with steroidogenesis both temporally and with respect to corticotropin concentration. This finding was complemented by measuring a concomitant decrease in free receptor sites. Full occupancy of the receptors was not necessary for maximal steroidogenesis. Binding kinetics of cyclic [(3)H]AMP in concentrations equivalent to the intracellular cyclic AMP concentration suggest the presence of at least three different intracellular cyclic AMP pools. These observations are in agreement with a possible role for cyclic AMP as a mediator of acute steroidogenesis induced by low corticotropin concentrations. 相似文献
42.
The thermal unfolding of yeast phenylalanine-specific tRNA (tRNAPhe) has been calorimetrically investigated at several salt concentrations in the absence of magnesium. Application of the deconvolution theory of macromolecular conformational transitions allows calculation of the thermodynamic parameters of unfolding. It is demonstrated that the unfolding of tRNAPhe occurs in a sequential fashion and that four separate transitions or five macromolecular thermodynamic states exist in the temperature range 8–72°C under the experimental conditions of these studies (0.067–0.52M Na+). The enthalpy and entropy changes between states and the relative population of each state as a function of temperature and salt concentration have been obtained. Sodium stabilizes the low-temperature conformations of tRNAPhe. The increase in the melting temperatures of each transition is shown to be linearly dependent on the logarithm of sodium concentration. These results allow calculation of the “phase” diagram for the transitions as a function of salt concentration. 相似文献
43.
The chain stiffness of linear native DNA is represented by a generalized bead and spring model recently proposed. It incorporates molecular rigidity by means of springs between beads, which are second neighbors along the contour of the chain. These springs are equivalent to elastic forces having longitudinal and transversal contributions. The model is compared with existing experimental data of sedimentation and low-angle light scattering to obtain the statistical parameters of DNA. The value of the statistical length obtained with this model is 1300 Å. The same value is obtained with the wormlike chain. Throughout this analysis, excluded volume is left out as a simplifying assumption. 相似文献
44.
45.
Abstract A 2.5-kb Sca I fragment of the type 3 pneumococcal strain 406 DNA containing a 1425-nucleotide open reading frame ( gadA ) and encoding a 475-amino acid protein ( M rmr 54427) was characterised. The gene gadA was expressed in Salmonella typhimurium . Pulsed-field gel electrophoresis and Southern blotting analysis of DNAs prepared from several pneumococcal serotypes showed that only those clinical isolates belonging to serotype 3 harbour the gadA gene. Sequence comparison of GadA with proteins included in the data banks revealed the highest similarity with human glutamate decarboxylase (GAD65 ) (59% similarity, 28% identity). Auto-antibodies to GAD65 have been associated with the onset of insulin-dependent diabetes mellitus. Interestingly, several epitopes of GAD65 that have been identified as immunodominant are particularly well conserved in the pneumococcal GadA. 相似文献
46.
47.
Autolysins are direct involved in the bactericidal effect caused by penicillin in wild type and in tolerant pneumococci 总被引:3,自引:0,他引:3
The two pneumococcal autolytic enzymes (an N-acetylmuramoyl-L-alanine amidase and an endo-beta-1,4-N-acetylglucosaminidase) are directly involved in the penicillin-induced killing of Streptococcus pneumoniae. The activity of these lytic enzymes was efficiently controlled in tolerant mutants under physiological conditions. 相似文献
48.
Ernesto Orme?o-Orrillo Marco A. Rogel Ligia Maria Oliveira Chueire James M. Tiedje Esperanza Martínez-Romero Mariangela Hungria 《Journal of bacteriology》2012,194(24):6927
The genome sequences of Burkholderia sp. strains CCGE1002 from Mexico and H160 from Brazil, isolated from legume nodules, are reported. Their gene contents in relation to plant-microbe interactions and xenobiotic degradation are discussed. 相似文献
49.
Luis E. Escobar Sandra Pritzkow Steven N. Winter Daniel A. Grear Megan S. Kirchgessner Ernesto Dominguez‐Villegas Gustavo Machado A. Townsend Peterson Claudio Soto 《Biological reviews of the Cambridge Philosophical Society》2020,95(2):393-408
Prions are misfolded infectious proteins responsible for a group of fatal neurodegenerative diseases termed transmissible spongiform encephalopathy or prion diseases. Chronic Wasting Disease (CWD) is the prion disease with the highest spillover potential, affecting at least seven Cervidae (deer) species. The zoonotic potential of CWD is inconclusive and cannot be ruled out. A risk of infection for other domestic and wildlife species is also plausible. Here, we review the current status of the knowledge with respect to CWD ecology in wildlife. Our current understanding of the geographic distribution of CWD lacks spatial and temporal detail, does not consider the biogeography of infectious diseases, and is largely biased by sampling based on hunters' cooperation and funding available for each region. Limitations of the methods used for data collection suggest that the extent and prevalence of CWD in wildlife is underestimated. If the zoonotic potential of CWD is confirmed in the short term, as suggested by recent results obtained in experimental animal models, there will be limited accurate epidemiological data to inform public health. Research gaps in CWD prion ecology include the need to identify specific biological characteristics of potential CWD reservoir species that better explain susceptibility to spillover, landscape and climate configurations that are suitable for CWD transmission, and the magnitude of sampling bias in our current understanding of CWD distribution and risk. Addressing these research gaps will help anticipate novel areas and species where CWD spillover is expected, which will inform control strategies. From an ecological perspective, control strategies could include assessing restoration of natural predators of CWD reservoirs, ultrasensitive CWD detection in biotic and abiotic reservoirs, and deer density and landscape modification to reduce CWD spread and prevalence. 相似文献