全文获取类型
收费全文 | 2076篇 |
免费 | 195篇 |
国内免费 | 1篇 |
出版年
2023年 | 7篇 |
2022年 | 18篇 |
2021年 | 30篇 |
2020年 | 24篇 |
2019年 | 25篇 |
2018年 | 21篇 |
2017年 | 29篇 |
2016年 | 58篇 |
2015年 | 83篇 |
2014年 | 83篇 |
2013年 | 135篇 |
2012年 | 146篇 |
2011年 | 148篇 |
2010年 | 95篇 |
2009年 | 80篇 |
2008年 | 100篇 |
2007年 | 105篇 |
2006年 | 100篇 |
2005年 | 126篇 |
2004年 | 88篇 |
2003年 | 85篇 |
2002年 | 129篇 |
2001年 | 47篇 |
2000年 | 29篇 |
1999年 | 29篇 |
1998年 | 53篇 |
1997年 | 34篇 |
1996年 | 34篇 |
1995年 | 30篇 |
1994年 | 27篇 |
1993年 | 34篇 |
1992年 | 18篇 |
1991年 | 14篇 |
1990年 | 17篇 |
1989年 | 19篇 |
1988年 | 13篇 |
1987年 | 9篇 |
1986年 | 11篇 |
1985年 | 7篇 |
1984年 | 13篇 |
1983年 | 15篇 |
1982年 | 16篇 |
1981年 | 10篇 |
1980年 | 9篇 |
1978年 | 7篇 |
1977年 | 6篇 |
1976年 | 6篇 |
1975年 | 6篇 |
1972年 | 8篇 |
1960年 | 4篇 |
排序方式: 共有2272条查询结果,搜索用时 15 毫秒
51.
Raymonda Varon Willem J. Kleijer Emrah J. Thompson Alessandra d'Azzo 《Human genetics》1982,62(1):66-69
Summary Reduced activity of -glucosidase was shown in the cultured skin fibroblasts of four patients with I-cell disease when the enzyme was tested without the use of detergents. In the presence of taurocholate and triton X100 -glucosidase activity was normal. This suggested a deficiency of a -glucosidase-activating factor in I-cell fibroblasts rather than of the enzyme itself. The deficiency of -glucosidase activity was corrected to some extent by mixing cell lysates, and more effectively by cocultivation and fusion of I-cell disease and Gaucher fibroblasts. These results present evidence for the presence of a -glucosidase-activating factor in normal and Gaucher fibroblasts. In fibroblasts of patients with I-cell disease this activator is probably deficient, as is the case for most lysosomal enzymes. 相似文献
52.
53.
Hans M.G. Princen Gerard C.M. Selten Anne-Marie E. Selten-Versteegen Gera P.B.M. Mol-Backx Willem Nieuwenhuizen Sing Hiem Yap 《Biochimica et Biophysica Acta (BBA) - Gene Structure and Expression》1982,699(2):121-130
To study the effect of regenerative response of the liver following partial hepatectomy on the synthesis of major plasma proteins (secretory proteins), we have determined the sequence contents and the distribution of albumin and fibrinogen polypeptide mRNAs in rat liver at intervals after partial hepatectomy and sham operation. Using a quantitative technique for the isolation of polyribosomes, we demonstrated that the distribution of RNA between free and membrane-bound polyribosomal fraction was unchanged in these experiments. There was no shift in the polyribosomal population to favor free polyribosomes after partial hepatectomy. However, there was a dramatic increase (5–6-fold) of the fibrinogen polypeptide mRNA concentration during the first 24 h after resection. In contrast, the albumin mRNA concentration decreased (2–3-fold). There were no α-fetoprotein mRNA sequences detectable in any liver RNA fraction in these experimental animals. In sham-operated rats with intact livers, similar changes of fibrinogen polypeptide and albumin mRNA concentrations as described in regenerating liver after partial hepatectomy, were observed. These results suggest that albumin and fibrinogen synthesis after partial hepatectomy is reciprocally regulated at the mRNA level and represents a nonspecific acute phase response to surgical trauma. 相似文献
54.
55.
Frans B. M. de Waal Jan A. R. A. M. van Hooff Willem J. Netto 《Primates; journal of primatology》1976,17(3):257-290
The primate literature provides many indications not only that the nature of dyadic interactions is to a large extent determined
by the relations of the interacting animals with others and between these others, but also of the existence of polyadic interactions
in which more than two individuals are simultaneously involved.
The objectives of the present study are to obtain a quantitative categorization of the agonistic interaction types of captive
Java-monkeys and an analysis of their dynamics.
After having described the agonistic behaviour patterns of Java-monkeys we shall discuss the categorization of agonistic interaction
types (depending on the number of involvees: “dyads”, “triads” and “polyads”), the way in which these types can be further
differentiated on the basis of the nature and the direction of the behaviours shown (e.g., different types of alliances), and the existence of so-called “sub-directed” behaviours (i.e., non-agonistic behaviours which are shown towards a dominant third animal more or less simultaneously with aggressive behaviour
directed towards an opponent).
The analysis indicates that agonistic behaviour is different both in its form and its regulation in interactions of different
complexity.
This research was supported in part by a government grant (i.e.: Beleidsruimte project: 16-21-06, “Brain and Behaviour”) to
the first author.
The investigation was supported by a grant from the Beleidsruimtemiddelen Hersenen en Gedrag to the first author. 相似文献
56.
A complex containing lipopolysaccharides, phospholipids and proteins is released into the culture medium by Escherichia coli during normal growth. It can be separated from the medium by gelfiltration on Sephadex G-200 or by centrifugation. Electron microscopy revealed that this material is released as vesicles and membrane fragments. To determine the origin of these fragments, they were compared to outer and cytoplasmic membranes with respect to keto-deoxyoctulosonic acid, phospholipid, and protein content, phospholipid composition, fatty acid composition, protein distribution on sodium dodecyl sulfate-polyacrylamide gels, buoyant density, and content of several membrane marker enzymes. The results of this comparison indicate that the membrane fragments found in the culture supernatant of normally growing Escherichia coli consist of practically unmodified outer membrane. Possible mechanisms as to the cause of the release of outer membrane fragments, and its relationship to cell-division, are discussed. 相似文献
57.
58.
59.
Stomatal conductance, one of the major plant physiological controls within NH3 biosphere–atmosphere exchange models, is commonly estimated from semi‐empirical multiplicative schemes or simple light‐ and temperature‐response functions. However, due to their inherent parameterization on meteorological proxy variables, instead of a direct measure of stomatal opening, they are unfit for the use in climate change scenarios and of limited value for interpreting field‐scale measurements. Alternatives based on H2O flux measurements suffer from uncertainties in the partitioning of evapotranspiration at humid sites, as well as a potential decoupling of transpiration from stomatal opening in the presence of hygroscopic particles on leaf surfaces. We argue that these problems may be avoided by directly deriving stomatal conductance from CO2 fluxes instead. We reanalysed a data set of NH3 flux measurements based on CO2‐derived stomatal conductance, confirming the hypothesis that the increasing relevance of stomatal exchange with the onset of vegetation activity caused a rapid decrease of observed NH3 deposition velocities. Finally, we argue that developing more mechanistic representations of NH3 biosphere–atmosphere exchange can be of great benefit in many applications. These range from model‐based flux partitioning, over deposition monitoring using low‐cost samplers and inferential modelling, to a direct response of NH3 exchange to climate change. 相似文献
60.
Ingrid M. Lubbers Matty P. Berg Gerlinde B. De Deyn Wim H. van der Putten Jan Willem van Groenigen 《Global Change Biology》2020,26(3):1886-1898
Soil faunal activity can be a major control of greenhouse gas (GHG) emissions from soil. Effects of single faunal species, genera or families have been investigated, but it is unknown how soil fauna diversity may influence emissions of both carbon dioxide (CO2, end product of decomposition of organic matter) and nitrous oxide (N2O, an intermediate product of N transformation processes, in particular denitrification). Here, we studied how CO2 and N2O emissions are affected by species and species mixtures of up to eight species of detritivorous/fungivorous soil fauna from four different taxonomic groups (earthworms, potworms, mites, springtails) using a microcosm set‐up. We found that higher species richness and increased functional dissimilarity of species mixtures led to increased faunal‐induced CO2 emission (up to 10%), but decreased N2O emission (up to 62%). Large ecosystem engineers such as earthworms were key drivers of both CO2 and N2O emissions. Interestingly, increased biodiversity of other soil fauna in the presence of earthworms decreased faunal‐induced N2O emission despite enhanced C cycling. We conclude that higher soil fauna functional diversity enhanced the intensity of belowground processes, leading to more complete litter decomposition and increased CO2 emission, but concurrently also resulting in more complete denitrification and reduced N2O emission. Our results suggest that increased soil fauna species diversity has the potential to mitigate emissions of N2O from soil ecosystems. Given the loss of soil biodiversity in managed soils, our findings call for adoption of management practices that enhance soil biodiversity and stimulate a functionally diverse faunal community to reduce N2O emissions from managed soils. 相似文献