全文获取类型
收费全文 | 165364篇 |
免费 | 6674篇 |
国内免费 | 2289篇 |
专业分类
174327篇 |
出版年
2023年 | 417篇 |
2022年 | 1125篇 |
2021年 | 1786篇 |
2020年 | 1160篇 |
2019年 | 1465篇 |
2018年 | 13245篇 |
2017年 | 11686篇 |
2016年 | 9521篇 |
2015年 | 4376篇 |
2014年 | 4572篇 |
2013年 | 5174篇 |
2012年 | 10146篇 |
2011年 | 18155篇 |
2010年 | 15188篇 |
2009年 | 11187篇 |
2008年 | 13879篇 |
2007年 | 15105篇 |
2006年 | 4004篇 |
2005年 | 3841篇 |
2004年 | 4171篇 |
2003年 | 3811篇 |
2002年 | 3182篇 |
2001年 | 2262篇 |
2000年 | 1974篇 |
1999年 | 1489篇 |
1998年 | 732篇 |
1997年 | 642篇 |
1996年 | 565篇 |
1995年 | 512篇 |
1994年 | 424篇 |
1993年 | 394篇 |
1992年 | 750篇 |
1991年 | 624篇 |
1990年 | 566篇 |
1989年 | 553篇 |
1988年 | 466篇 |
1987年 | 450篇 |
1986年 | 346篇 |
1985年 | 357篇 |
1984年 | 311篇 |
1983年 | 256篇 |
1982年 | 202篇 |
1981年 | 171篇 |
1979年 | 224篇 |
1978年 | 200篇 |
1977年 | 181篇 |
1976年 | 173篇 |
1974年 | 198篇 |
1972年 | 401篇 |
1971年 | 397篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
91.
Hyperthermic treatment at 43 degrees C suppressed the growth of Ehrlich ascites tumor (EAT) cells in vitro. Incubation of EAT cells at 43 degrees C for as little as 1.5 h totally abolished the transplantability of the tumor. At the same time, the rate of cellular glucose uptake, the density of glucose transporter on the cells as well as the extent of thymidine, uridine and leucine incorporation were significantly reduced. 相似文献
92.
93.
94.
95.
Effect of membrane additives on vesicle fusion 总被引:1,自引:0,他引:1
A large variety of alkyl derivatives were found to either slow or block the low-temperature induced fusion of dipalmitoylphosphatidylcholine small unilamellar vesicles (DPPC SUV) when incorporated into the SUV bilayer at five mol%. Only corn oil was fusogenic. 相似文献
96.
Shallow-water vegetated estuarine habitats, notably seagrass, mangrove and saltmarsh, are known to be important habitats for
many species of small or juvenile fish in temperate Australia. However, the movement of fish between these habitats is poorly
understood, and yet critical to the management of the estuarine fisheries resource. We installed a series of buoyant pop nets
in adjacent stands of seagrass, mangrove and saltmarsh in order to determine how relative abundance of fishes varied through
lunar cycles. Nets were released in all habitats at the peak of the monthly spring tide for 12 months, and in the seagrass
habitat at the peak of the neap tide also. The assemblage of fish in each habitat differed during the spring tides. The seagrass
assemblage differed between spring and neap tide, with the neap tide assemblage showing greater abundances of fish, particularly
those species which visited the adjacent habitats when inundated during spring tides. The result supports the hypothesis that
fish move from the seagrass to the adjacent mangrove and saltmarsh during spring tides, taking advantage of high abundances
of zooplankton, and use seagrass as a refuge during lower tides. The restoration and preservation of mangrove and saltmarsh
utility as fish habitat may in some situations be linked to the proximity of available seagrass. 相似文献
97.
98.
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99.
100.
We have developed a procedure for the reconstitution of Escherichia coli diacylglycerol kinase (DGK) into phospholipid bilayers containing diacylglycerol substrate. When DGK is reconstituted into a series of phosphatidylcholines containing monounsaturated fatty acyl chains, activity against dihexanoylglycerol (DHG) as a substrate was found to be markedly dependent on the fatty acyl chain length with the highest activity in dioleoylphosphatidylcholine [di(C18:1)PC] and a lower activity in bilayers with shorter or longer fatty acyl chains. Low activities in the short chain phospholipid dimyristoleoylphosphatidylcholine [di(C14:1)PC] followed from an increase in the K(m) value for DHG and ATP, with no effect on v(max). In contrast, in the long chain lipid dierucoylphosphatidylcholine [di(C24:1)PC], the low activity followed from a decrease in v(max) with no effect on K(m). In mixtures of two phosphatidylcholines with different chain lengths, the activity corresponded to that expected for the average chain length of the mixture. Cholesterol increased the activity in di(C14:1)PC but slightly decreased it in di(C18:1)PC or di(C24:1)PC, effects that could follow from changes in bilayer thickness caused by cholesterol. 相似文献