全文获取类型
收费全文 | 87960篇 |
免费 | 19788篇 |
国内免费 | 6188篇 |
专业分类
113936篇 |
出版年
2024年 | 161篇 |
2023年 | 683篇 |
2022年 | 1740篇 |
2021年 | 3149篇 |
2020年 | 3920篇 |
2019年 | 5775篇 |
2018年 | 5792篇 |
2017年 | 5563篇 |
2016年 | 6216篇 |
2015年 | 7425篇 |
2014年 | 7880篇 |
2013年 | 8645篇 |
2012年 | 7554篇 |
2011年 | 6756篇 |
2010年 | 6299篇 |
2009年 | 4650篇 |
2008年 | 4371篇 |
2007年 | 3576篇 |
2006年 | 3266篇 |
2005年 | 2875篇 |
2004年 | 2610篇 |
2003年 | 2413篇 |
2002年 | 2110篇 |
2001年 | 1468篇 |
2000年 | 1288篇 |
1999年 | 1185篇 |
1998年 | 710篇 |
1997年 | 564篇 |
1996年 | 570篇 |
1995年 | 526篇 |
1994年 | 483篇 |
1993年 | 330篇 |
1992年 | 457篇 |
1991年 | 350篇 |
1990年 | 352篇 |
1989年 | 322篇 |
1988年 | 228篇 |
1987年 | 205篇 |
1986年 | 187篇 |
1985年 | 174篇 |
1984年 | 135篇 |
1983年 | 112篇 |
1982年 | 99篇 |
1981年 | 66篇 |
1979年 | 80篇 |
1978年 | 59篇 |
1977年 | 59篇 |
1975年 | 61篇 |
1974年 | 50篇 |
1973年 | 53篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
21.
P. Cruz C. H. Mejia‐Ruiz R. Perez‐Enriquez A. M. Ibarra 《Molecular ecology resources》2002,2(3):239-241
Five polymorphic microsatellite loci were characterized for Penaeus (Litopenaeus) vannamei. Loci were isolated using a partial Sau3A1 genomic library by the sequencing of randomly selected clones and by a biotinylated (CT)10 and (GT)10 probes screening procedure. The last strategy resulted in the most useful data. About 40% of the clones showed a previously reported satellite/microsatellite (PVS1), reducing the chance of finding new microsatellite regions. Whereas two of the microsatellite loci with more than 10 alleles will be useful for mating analysis in a breeding program, the others might prove useful for population genetic studies. 相似文献
22.
23.
24.
25.
26.
27.
Guanethidine treatment or adrenal medullectomy significantly inhibited the elevation in blood pressure induced by Clostridium perfringens beta toxin, and the combination of the two drastically reduced the pressure rise, to less than 19% of that in control rats. When rats were pretreated with tetrodotoxin or hexamethonium, the toxin-evoked rise was significantly inhibited. Elevation in blood pressure induced by the toxin in spinal rats tended to be less than that in control rats. When investigated by a microscopical technique, arteriolar constriction in the mesenteric vasculature was observed after the blood pressure elevation induced by the toxin reached a maximum. Blood flow in the skin decreased with an increase in blood pressure following intravenous injection of the toxin. It is concluded that beta toxin acts on the autonomic nervous system and produces arterial constriction. 相似文献
28.
Structural changes associated with corolla wilting may serve as a mechanism for effecting self-pollination. Low pollinator visitation, high seed production and a corolla that persists after anthesis indicates that Pedicularis dunniana is autogamous. Delayed autonomous self-pollination is facilitated by corolla wilting. Wilting of the upper lip (galea) brought the pollen laden anthers into contact with the stigma resulting in the deposition of self pollen on the stigma. The seed set of flowers either emasculated, or with restrained galeae thus preventing anthers brushing against the stigma, was significantly lower than that of open-pollinated flowers. This demonstrates that autogamy occurs in this species through corolla wilting. Germination experiments indicated that outcross seedlings were more vigorous than selfed seedlings as a result of inbreeding depression. It is likely that autogamy provides reproductive assurance for P. dunniana under conditions of pollinator scarcity. 相似文献
29.
Background
Eosinophilia plays the major role in the pathogenesis of asthma and correlates with the up‐regulation of eotaxin, which, together with interleukin (IL)‐5, is important for differentiation, chemo‐attraction, degranulation, and survival of eosinophils in local tissue. In a previous study, we found that administration of lentivirus‐delivered short hairpin RNA (shRNA) to suppress the expression of IL‐5 inhibited airway inflammation. The present study aimed to investigate the role of eotaxin shRNA and the synergistic effect of eotaxin and IL‐5 shRNAs on airway inflammation in an ovalbumin (OVA)‐induced murine model of asthma.Methods
Lentivirus‐delivered shRNAs were used to suppress the expression of eotaxin and/or IL‐5 in local tissue in an OVA‐induced murine asthma model.Results
Intra‐tracheal administration of lentivirus containing eotaxin shRNA expressing cassette (eoSEC3.3) efficiently moderated the characteristics of asthma, including airway hyper‐responsiveness, cellular infiltration of lung tissues, and eotaxin and IL‐5 levels in bronchio‐alveolar lavage fluid. Administration of lentiviruses expressing IL‐5 or eotaxin shRNAs (IL5SEC4 + eoSEC3.3) also moderated the symptoms of asthma in a mouse model.Conclusions
Local delivery of lentiviruses expressing IL‐5 and eotaxin shRNAs provides a potential tool in moderating airway inflammation and also has the potential for developing clinical therapy based on the application of shRNAs of chemokines and cytokines involved in T helper 2 cell inflammation and eosinophilia. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献30.
Rabbit alveolar macrophages exhibit a chemiluminescent response which is associated with phagocytosis of zymosan and polystyrene-butadiene particles. The chemiluminescence reaches a peak in 15 to 25 minutes and then gradually diminishes over the next 1 to 3 hours. During the time of maximal light emission there appears to be no actual uptake of particles, but the response is dependent upon the particle concentration. The metabolic inhibitor, DNP (2,4-dinitrophenol), causes a rapid inhibition of the chemiluminescent response. The addition of ATP to the medium prior to exposure of the cells to particles causes the chemiluminescent response to be greatly diminished, i.e., 0.3mM ATP virtually abolishes the response. These experiments suggest that some metabolic response of the cell to phagocytosis is responsible for the chemiluminescence. 相似文献