全文获取类型
收费全文 | 52072篇 |
免费 | 4453篇 |
国内免费 | 5503篇 |
出版年
2023年 | 1194篇 |
2022年 | 1321篇 |
2021年 | 2078篇 |
2020年 | 1959篇 |
2019年 | 2623篇 |
2018年 | 2188篇 |
2017年 | 1845篇 |
2016年 | 1851篇 |
2015年 | 1951篇 |
2014年 | 2935篇 |
2013年 | 4000篇 |
2012年 | 2254篇 |
2011年 | 2585篇 |
2010年 | 1961篇 |
2009年 | 2483篇 |
2008年 | 2482篇 |
2007年 | 2565篇 |
2006年 | 2277篇 |
2005年 | 2101篇 |
2004年 | 1861篇 |
2003年 | 1624篇 |
2002年 | 1480篇 |
2001年 | 1141篇 |
2000年 | 998篇 |
1999年 | 885篇 |
1998年 | 863篇 |
1997年 | 739篇 |
1996年 | 619篇 |
1995年 | 625篇 |
1994年 | 650篇 |
1993年 | 559篇 |
1992年 | 526篇 |
1991年 | 497篇 |
1990年 | 405篇 |
1989年 | 361篇 |
1988年 | 376篇 |
1987年 | 292篇 |
1986年 | 331篇 |
1985年 | 506篇 |
1984年 | 607篇 |
1983年 | 350篇 |
1982年 | 481篇 |
1981年 | 472篇 |
1980年 | 407篇 |
1979年 | 309篇 |
1978年 | 228篇 |
1977年 | 238篇 |
1976年 | 217篇 |
1975年 | 168篇 |
1973年 | 180篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Andrea Dichlberger Stefanie Schlager Katariina Maaninka Wolfgang J. Schneider Petri T. Kovanen 《Journal of lipid research》2014,55(12):2471-2478
Human mast cells (MCs) contain TG-rich cytoplasmic lipid droplets (LDs) with high arachidonic acid (AA) content. Here, we investigated the functional role of adipose TG lipase (ATGL) in TG hydrolysis and the ensuing release of AA as substrate for eicosanoid generation by activated human primary MCs in culture. Silencing of ATGL in MCs by siRNAs induced the accumulation of neutral lipids in LDs. IgE-dependent activation of MCs triggered the secretion of the two major eicosanoids, prostaglandin D2 (PGD2) and leukotriene C4 (LTC4). The immediate release of PGD2 from the activated MCs was solely dependent on cyclooxygenase (COX) 1, while during the delayed phase of lipid mediator production, the inducible COX-2 also contributed to its release. Importantly, when ATGL-silenced MCs were activated, the secretion of both PGD2 and LTC4 was significantly reduced. Interestingly, the inhibitory effect on the release of LTC4 was even more pronounced in ATGL-silenced MCs than in cytosolic phospholipase A2-silenced MCs. These data show that ATGL hydrolyzes AA-containing TGs present in human MC LDs and define ATGL as a novel regulator of the substrate availability of AA for eicosanoid generation upon MC activation. 相似文献
2.
3.
4.
5.
Learning-Induced Expression of Meningeal Ependymin mRNA and Demonstration of Ependymin in Neurons and Glial Cells 总被引:1,自引:0,他引:1
Stefan Rother Rupert Schmidt Wolfgang Brysch †Karl-Hermann Schlingensiepen 《Journal of neurochemistry》1995,65(4):1456-1464
Abstract: The turnover of a CNS-specific cell adhesion glycoprotein, ependymin, has earlier been found to increase during periods of neuronal plasticity. Here, ependymin mRNA expression was analyzed by semiquantitative in situ hybridization in goldfish. Learning of an active avoidance response resulted in a significant increase in ependymin mRNA expression 20 min to 4 h after acquisition of the task. In contrast, yoked control animals that were exposed to the same numbers of conditioned and unconditioned stimuli in a random, unpaired manner exhibited a strong down-regulation of ependymin mRNA. Hybridization signals were also increased by injection of anti-ependymin antiserum into brain ventricles. Ependymin mRNA was exclusively localized to reticular-shaped fibroblasts of the inner endomeningeal cell layer. Immunoelectron microscopic investigation, however, revealed ependymin also in distinct neuronal and glial cell populations in which no ependymin mRNA had been detected. Uptake of meningeal protein factors into glial and neuronal cells may therefore be of functional importance for plastic adaptations of the CNS. 相似文献
6.
Phytoplankton biomass values in Tavropos Reservoir, ranging from 92 to 1071 mg m–3, are within a range characteristic of oligotrophic waters. The seasonal sequence of biomass shows three annual peaks, differing from the monoacmic pattern seen in oligotrophic lakes. This sequence was profoundly affected by changes in water withdrawal and inflow rates. Diatoms, cryptophytes, chrysophytes and dinoflagellates, in that order, were the major constituents of the reservoir phytoplankton. The succession, from diatoms and chrysophytes in late winter-spring, to centric diatoms in late spring-summer and again to diatom-chrysophytes in late autumn was similar to that in oligotrophic lakes. 相似文献
7.
《Microbes and infection / Institut Pasteur》2015,17(2):109-117
Ebola virus infection can cause Ebola virus disease (EVD). Patients usually show severe symptoms, and the fatality rate can reach up to 90%. No licensed medicine is available. In this review, development of therapeutics for treatment of Ebola virus infection and EVD will be discussed. 相似文献
8.
9.
《Saudi Journal of Biological Sciences》2016,23(4):462-466
The present study is to determine the prevalence and implication of coeliac disease (CD) among adult Saudis and compared to those with diagnosed irritable bowel syndrome. This prospective study was conducted among 980 adults. Out of that, 482 subjects (staff and students of Riyadh Health Science College) were designated as control cohorts for undetected coeliac disease. Furthermore, another contingent of 498 subjects diagnosed with irritable bowel syndrome (IBS) at Prince Salman Hospital and Al-Iman General Hospital also constituted a segment of the overall initial 1020 subjects. Both cases and control were tested for serological markers of coeliac disease (tissues transglutaminase (tTGAs) and endomysial autoantibody (EMAs) and were confirmed by histopathology test. All the positive for cases of coeliac disease were screened for iron deficiency anaemia, Vitamin D deficiency, and osteoporosis and weight assessment. The percentage of coeliac disease in control subjects and patients diagnosed with irritable bowel syndrome (IBS) were found to be 1.9% and 9.6% respectively, about 38% of the total coeliac disease patients are among females of middle age (20–39-years) and 16% of the males in the same age range. Whereas, 20% and 25% of all coeliac disease cases with ages of 40–59 were remarked as females and males respectively. The identical nature and overlap of symptoms of the two conditions could possibly result in misdiagnosis of coeliac diseases or over-diagnosis of irritable bowel syndrome. The findings of the study might also give considerable implications of the disease in the nutritional level which is noticeable. 相似文献
10.
Normal and limited vision gait was investigated in individuals with Parkinson disease (PD), healthy older and healthy young individuals. Participants walked a GAITRite mat with normal vision or vision of lower limbs occluded. Results indicate individuals with PD walked more slowly, with shorter and wider steps, and spent more time in double support with limited vision as compared to full vision. Healthy young and old individuals took shorter steps but were otherwise unchanged between conditions. 相似文献