全文获取类型
收费全文 | 7955篇 |
免费 | 908篇 |
国内免费 | 4篇 |
出版年
2021年 | 112篇 |
2020年 | 70篇 |
2018年 | 87篇 |
2017年 | 72篇 |
2016年 | 137篇 |
2015年 | 261篇 |
2014年 | 233篇 |
2013年 | 312篇 |
2012年 | 383篇 |
2011年 | 382篇 |
2010年 | 211篇 |
2009年 | 186篇 |
2008年 | 304篇 |
2007年 | 296篇 |
2006年 | 257篇 |
2005年 | 246篇 |
2004年 | 250篇 |
2003年 | 220篇 |
2002年 | 243篇 |
2001年 | 197篇 |
2000年 | 205篇 |
1999年 | 172篇 |
1998年 | 100篇 |
1997年 | 93篇 |
1996年 | 69篇 |
1995年 | 80篇 |
1994年 | 84篇 |
1993年 | 96篇 |
1992年 | 134篇 |
1991年 | 179篇 |
1990年 | 162篇 |
1989年 | 183篇 |
1988年 | 148篇 |
1987年 | 160篇 |
1986年 | 136篇 |
1985年 | 136篇 |
1984年 | 127篇 |
1983年 | 105篇 |
1982年 | 131篇 |
1981年 | 140篇 |
1980年 | 123篇 |
1979年 | 133篇 |
1978年 | 102篇 |
1977年 | 86篇 |
1976年 | 89篇 |
1975年 | 75篇 |
1974年 | 74篇 |
1973年 | 79篇 |
1972年 | 92篇 |
1966年 | 68篇 |
排序方式: 共有8867条查询结果,搜索用时 15 毫秒
1.
E King 《BMJ (Clinical research ed.)》1983,286(6383):2059-2060
2.
A group of captive chimpanzees, consisting of one adult male and three mother/infant pairs, was systematically observed over a 15-month period. Over 200 hr of data were collected, using both sequential and time sampling techniques, and compared to the available data on wild chimps. Unlike many captive groups, most behavior patterns were remarkably similar, both qualitatively and quantitatively, to that of wild chimpanzees including: play, grooming, infant sexual development, tool use, food sharing, prosocial partner preferences, and aggressive displays. 相似文献
3.
Ferdinand Bohlmann Elena Tsankova Jasmin Jakupovic Robert M. King Harold Robinson 《Phytochemistry》1983,22(2):557-560
The investigation of Encelia canescens afforded, in addition to several known compounds, four new dimeric p-hydroxyacetophenone derivatives, two epimeric chromene dimers and two epimeric mixed dimers of euparin and encecalin. Furthermore, derivatives of tremetone and of encecalin were present. The structures were elucidated hy high field 1H NMR spectroscopy. 相似文献
4.
Obesity-inducing lesions of the central nervous system alter leptin uptake by the blood-brain barrier. 总被引:1,自引:0,他引:1
Leptin regulates body adiposity by decreasing feeding and increasing thermogenesis. Obese humans and some obese rodents are resistant to peripherally administered leptin, suggesting a defect in the transport of leptin across the blood-brain barrier (BBB). Defective transport of exogenous leptin occurs in some models of obesity, but in other models transport is normal. This shows that factors other than obesity are associated with impairment of leptin transport across the BBB. In order to further investigate these factors, we determined leptin transport in rats made obese by lesioning of the ventromedial hypothalamus (VMH), paraventricular nucleus (PVN), or posterodorsal amygdala (PDA). These regions all contain leptin receptors and lesions there induce obesity and hyperleptinemia and alter the levels of many feeding hormones which might participate in leptin transporter regulation. We measured the uptake of radioactively labeled leptin by the BBB by multiple-time regression analysis which divides uptake into a reversible phase (Vi, e.g., receptor/transporter binding to the brain endothelial cell) and an irreversible phase (Ki, complete transport across the BBB). Leptin uptake was not affected in rats with VMH lesions. No significant change occurred in the entry rate (Ki) for any group, although Ki declined by over 35% in rats with PVN lesions. Decreased uptake was observed in rats with PVN lesions and with PDA lesions. This was primarily due to a reduced Vi (about 21% for the PDA). This decreased uptake is most likely explained by decreased binding of leptin to the brain endothelial cell, which could be because of decreased binding by either receptors or transporters. This suggests that some of the feeding hormones controlled by the PVN and PDA may participate in regulating leptin uptake by the BBB. 相似文献
5.
Interest in cross-disciplinary research knowledge interchange runs high. Review processes at funding agencies, such as the U.S. National Science Foundation, consider plans to disseminate research across disciplinary bounds. Publication in the leading multidisciplinary journals, Nature and Science, may signify the epitome of successful interdisciplinary integration of research knowledge and cross-disciplinary dissemination of findings. But how interdisciplinary are they? The journals are multidisciplinary, but do the individual articles themselves draw upon multiple fields of knowledge and does their influence span disciplines? This research compares articles in three fields (Cell Biology, Physical Chemistry, and Cognitive Science) published in a leading disciplinary journal in each field to those published in Nature and Science. We find comparable degrees of interdisciplinary integration and only modest differences in cross-disciplinary diffusion. That said, though the rate of out-of-field diffusion might be comparable, the sheer reach of Nature and Science, indicated by their potent Journal Impact Factors, means that the diffusion of knowledge therein can far exceed that of leading disciplinary journals in some fields (such as Physical Chemistry and Cognitive Science in our samples). 相似文献
6.
The spontaneous allele quakingviable (qk
v
) exerts effects on myelination and spermiogenesis. The defects generated by qk
v
were not separated in a multilocus mapping cross that provided a mapping resolution of 0.1 centiMorgans (cM). Furthermore, no distortions suggestive of a large chromosomal anomaly associated with qk
v
were apparent. One plausible interpretation is that the quaking locus contains more than one functional domain, either organized into overlapping genes or expressed by alternative splicing mechanisms. The cloning needed to analyze this locus will be enhanced by the very high resolution of the meiotic mapping cross reported here. The recombinational distances on this qk
v
map were compressed compared with those previously reported in a high-resolution map for qk
1–1, an embryonic lethal allele of quaking induced by ethylnitrosourea. Additional crosses confirmed prior reports that the sex and the genetic background of the heterozygous parent can affect recombinational distances. These joint effects on recombination are strong enough to account for the discrepancy between the two maps. This variability of two-factor map values leads to the preferred multilocus map-building protocol discussed in the accompanying paper. 相似文献
7.
8.
9.
Nataly Mancette Rijensky Netta R. Blondheim Shraga Eilon Barnea Nir Peled Eli Rosenbaum Aron Popovtzer Solomon M. Stemmer Alejandro Livoff Mark Shlapobersky Neta Moskovits Dafna Perry Eitan Rubin Itzhak Haviv Arie Admon 《Molecular & cellular proteomics : MCP》2020,19(8):1360-1374
- Download : Download high-res image (147KB)
- Download : Download full-size image
- •Sufficient tumor tissues are often unavailable large HLA peptidome discovery.
- •Using patient derived xenograft (PDX) tumors can overcome this limitation.
- •The large PDX HLA peptidomes expand significantly those of the original biopsies.
- •The HLA peptidomes of the PDX tumors included many tumor antigens.
10.