全文获取类型
收费全文 | 2657篇 |
免费 | 251篇 |
国内免费 | 1篇 |
出版年
2022年 | 14篇 |
2021年 | 34篇 |
2020年 | 22篇 |
2019年 | 44篇 |
2018年 | 48篇 |
2017年 | 47篇 |
2016年 | 73篇 |
2015年 | 133篇 |
2014年 | 142篇 |
2013年 | 162篇 |
2012年 | 194篇 |
2011年 | 183篇 |
2010年 | 126篇 |
2009年 | 83篇 |
2008年 | 140篇 |
2007年 | 152篇 |
2006年 | 129篇 |
2005年 | 111篇 |
2004年 | 113篇 |
2003年 | 105篇 |
2002年 | 109篇 |
2001年 | 59篇 |
2000年 | 65篇 |
1999年 | 50篇 |
1998年 | 37篇 |
1997年 | 32篇 |
1996年 | 25篇 |
1995年 | 29篇 |
1994年 | 16篇 |
1993年 | 15篇 |
1992年 | 32篇 |
1991年 | 47篇 |
1990年 | 43篇 |
1989年 | 30篇 |
1988年 | 31篇 |
1987年 | 24篇 |
1986年 | 20篇 |
1985年 | 28篇 |
1984年 | 22篇 |
1983年 | 18篇 |
1982年 | 18篇 |
1981年 | 16篇 |
1979年 | 12篇 |
1978年 | 10篇 |
1977年 | 11篇 |
1976年 | 5篇 |
1973年 | 5篇 |
1972年 | 7篇 |
1971年 | 5篇 |
1970年 | 7篇 |
排序方式: 共有2909条查询结果,搜索用时 15 毫秒
61.
Virus-receptor interaction in the adenovirus system I. Identification of virion attachment proteins of the HeLa cell plasma membrane. 总被引:18,自引:15,他引:3 下载免费PDF全文
Plasma membranes from HeLa cells were isolated in a two-phase polymer system. To compare the efficiency of attachment protein extraction, a normalized assay for the assessment of adenovirus type 2 (Ad2) receptor-active components interfering with the attachment of Ad2 to HeLa cells was developed. An optimized detergent extraction procedure, 0.5% Triton X-100, was used, and solubilized membrane proteins were radioisotope labeled in vitro. Proteins with affinity for Ad2 virions were quantified and identified in a sucrose gradient sedimentation assay and by affinity chromatography with cross-linked Ad2 virions immobilized to AH-Sepharose 4B. From virions recovered in the sucrose gradient system, one major membrane component of high affinity was identified with a polypeptide molecular weight of around 40,000. Glycosylated proteins isolated by wheat germ lectin chromatography with high affinity for immobilized virus particles were isolated, and two major components with apparent molecular weights of 40,000 and 42,000 were identified. We suggest that a glycosylated protein with high affinity for Ad2 virions and a polypeptide molecular weight of 40,000 to 42,000 is one component of the Ad2 attachment site on HeLa cells. 相似文献
62.
Hans Persson 《Plant Ecology》1980,41(2):101-109
63.
14C-labeled extracellular organic carbon (EOC) released by the phytoplankton in a Danish Estuary was shown immediately to form particles (>0.2m) when the products were added to a natural water sample. About 14%–20% of the added activity could be recovered as particles. Any bacterial assimilation of the extracellular products was thus masked. The abiotic origin of the particulate EOC was verified, and it was shown that the particle formation was due to some factors present in the estuarine water with a nominal diameter >0.2m. Precaution must be taken to avoid misinterpretations in studies concerning carbon flow from algae to bacteria. 相似文献
64.
65.
Peripheral blood plasma Cortisol concentration and its diurnal variation was measured in 4 horses. Mean concentration of Cortisol during 24 hrs. was 42 ng/ml (s ± 20 ng/ml). Peak values occurred at 6 a.m. and the lowest values were observed at about 6 p.m. (mean 65 ng/ml and 20 ng/ml, respectively). Long-acting ACTH at a dose of 150 i.u. was given by intramuscular injection to the 4 horses. Peak Cortisol concentrations markedly exceeding the prestimulation level were obtained between 2 and 4 hrs. after injection. During the immediate 24 hrs. after these peaks, the mean Cortisol level was markedly lower and the cyclic variation out of phase with the basal diurnal pattern. After a gradual adjustment during the second postinjection day, no differences could be seen between the 2 patterns on day 3 after injection. 相似文献
66.
A human skull with mandible from the Ngada District on the island of Flores, Indonesia, is described in order to contribute to the knowledge of variation in cranial architecture, which is important in interpretations of evolutionary cerebralisation. The skull was excavated in 1924 and sent to the National Museum in Copenhagen. The “Copenhagen Flores” (CF) male skull is radiocarbon-dated and of modern age. The cranium is small, but larger than e.g. Liang Bua skull (LB1) in every measurement. The (CT-scan based) cranial capacity of 1258 ml is normal for modern humans, but somewhat lower than values from the middle or upper Palaeolithics. The metric cranial data analysed in FORDISC, characterize the skull as a male Vietnamese rather than a Chinese or White individual. Tooth morphology shows the sundadont pattern and tooth size corresponds to that of teeth from Bali, Java and Malayan Orang Asli. Remarkable are the marked asymmetries in the dentition with rotation of an upper premolar and congenital absence of a third molar. In these respects the CF skull is similar to dentitions belonging to the pygmoid villagers of Rampasasa, a village not far from the Liang Bua cave, and to LB1. 相似文献
67.
Lars-Eric Persson 《Journal of experimental marine biology and ecology》1983,68(3):277-293
Quantitative (0.1-m2) samples of benthic macrofauna were taken at three depths (5, 10, 17 m) off the eastern coast of Scania, southern Baltic, in the period April 1974 to August 1978. Altogether 20 sampling cruises were made. Spatial and temporal species composition, abundance and biomass were compared. The number of species increased significantly with increasing depth. Zonation of the species was due to their zoogeographical origin and capacity to withstand exposure. Abundance was highest at 5 m depth whereas biomass increased with depth due to the dominance of large bivalves. Variation in abundance within years was large at all three depths and connected with reproductive recruitment for all species except Bathyporeia pilosa Lindström which migrated towards the shore in summer. 相似文献
68.
The human aldose reductase gene maps to chromosome region 7q35 总被引:1,自引:0,他引:1
Alexander Graham Paul Heath John E. N. Morten Alexander F. Markham 《Human genetics》1991,86(5):509-514
Summary The human aldose reductase (AR) gene has been mapped to chromosome 7 using the polymerase chain reaction to specifically amplify the human AR sequence in hamster/human hybrid DNA and also in mouse/ human monochromosome hybrids. The assignment to chromosome 7 was confirmed by in situ hybridisation to human metaphase chromosomes using a novel, rapid hybridisation, method giving a regional localisation at 7q35. 相似文献
69.
70.
Persson Joel Ford Scott Keophoxay Anousith Mertz Ole Nielsen Jonas Østergaard Vongvisouk Thoumthone Zörner Michael 《Human ecology: an interdisciplinary journal》2021,49(5):597-616
Human Ecology - Despite the popularity of integrated conservation and development approaches to protected area management, adjacent communities increasingly face livelihood dilemmas. Yet... 相似文献