全文获取类型
收费全文 | 103264篇 |
免费 | 1161篇 |
国内免费 | 812篇 |
出版年
2022年 | 90篇 |
2021年 | 156篇 |
2020年 | 115篇 |
2019年 | 157篇 |
2018年 | 11999篇 |
2017年 | 10809篇 |
2016年 | 7685篇 |
2015年 | 1009篇 |
2014年 | 711篇 |
2013年 | 913篇 |
2012年 | 4898篇 |
2011年 | 13423篇 |
2010年 | 12405篇 |
2009年 | 8621篇 |
2008年 | 10312篇 |
2007年 | 11919篇 |
2006年 | 792篇 |
2005年 | 1049篇 |
2004年 | 1508篇 |
2003年 | 1561篇 |
2002年 | 1396篇 |
2001年 | 381篇 |
2000年 | 249篇 |
1999年 | 160篇 |
1998年 | 162篇 |
1997年 | 165篇 |
1996年 | 137篇 |
1995年 | 109篇 |
1994年 | 106篇 |
1993年 | 130篇 |
1992年 | 124篇 |
1991年 | 117篇 |
1990年 | 77篇 |
1989年 | 71篇 |
1988年 | 67篇 |
1987年 | 62篇 |
1985年 | 53篇 |
1984年 | 74篇 |
1983年 | 76篇 |
1982年 | 97篇 |
1981年 | 84篇 |
1980年 | 64篇 |
1979年 | 55篇 |
1978年 | 52篇 |
1977年 | 51篇 |
1976年 | 51篇 |
1975年 | 40篇 |
1973年 | 40篇 |
1972年 | 259篇 |
1971年 | 289篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
221.
222.
223.
Eric Delson 《Journal of Mammalian Evolution》2007,14(3):198-199
224.
The influence of moulded hay (Alternaria alternata, Epicoccum nigrum, Mucor racemosus, Ulocladium chartarum) and the efficiency of Vitamin B1 substitution to cope these effects on rumen protozoa was investigated using the longterm rumen simulation technique (RUSITEC) for about 25 days. Moulded hay affected medium-sized protozoa to a different extent (Alternaria alternata: ?16 %, Epicoccum nigrum: ?27 %, Mucor racemosus: ?9 %, Ulocladium chartarum: +2 %). The vitamin B1 substitution had positive effects during the feeding of Mucor racemosus and Ulocladium chartarum. 相似文献
225.
Jerzy Chelkowski Piotr Zajkowski Marcin Zawadzki Juliusz Perkowski 《Mycotoxin Research》1987,3(1):25-32
An isolated rat liver was perfused with deoxynivalenol (DON) at a dose of 3 mg in a recirculating perfusion system. To identify glucuronide conjugates equal amounts of bile samples, perfusate and liver homogenates were incubated with and without (control) a β-glucuronidase preparation and analyzed by thin layer chromatography and capillary gas liquid chromatography — chemical ionization mass spectrometry. A total of 40.4% of the administered dose of DON was found to be conjugated with glucuronic acid (perfusate 20.4%, bile 19.2%, liver 0.8%), while only 1.3% of the parent DON (perfusate 1.1%, bile 0.2%) was detected. The cleavage of DON-glucuronide was demonstrated by incubating DON-glucuronide containing bile samples with intestine contents under anaerobic conditions. 相似文献
226.
Ahmed Lebrihi Pierre Germain Gérard Lefebvre 《Applied microbiology and biotechnology》1987,26(2):130-135
Summary Production of cephamycin and clavulanic acid by Streptomyces clavuligerus is controlled by the phosphate concentration. Phosphate represses the biosynthesis of cephamycin synthetase, expandase and clavulanic acid synthetase. In the presence of 2 mM phosphate, the specific activities of expandase, cephamycin synthetase and clavulanic acid synthetase were higher than in the presence of 75 mM phosphate. The specific activity of cephamycin synthetase is maximal with an initial phosphate concentration of 10 mM, whereas the specific activity of expandase is maximal with 1 mM phosphate. A correlation between cephamycin synthetase specific activity and expandase specific activity was established at phosphate concentrations higher than 10 mM. This shows that the expandase is an important enzyme in the mechanism by which the phosphate concentration affects the biosynthesis of cephamycin. 相似文献
227.
Axonal Transport Characteristics of Gangliosides in Sensory Axons of Rat Sciatic Nerve 总被引:2,自引:2,他引:0
G. Jean Harry Jeffry F. Goodrum Arrel D. Toews† Pierre Morell† 《Journal of neurochemistry》1987,48(5):1529-1536
The distribution of axonally transported gangliosides and glycoproteins along the sciatic nerve was examined from 3 h to 4 weeks following injection of[3H]glucosamine into the fifth lumbar dorsal root ganglion of adult rats. Incorporation of labeled precursor into these glycoconjugates reached a maximal level in the ganglion within 6 h. Outflow patterns of radioactivity for glycoproteins showed a well-defined crest with a transport rate of approximately 330 mm/day. In contrast, the crest of transported gangliosides was continuously attenuated, implying a significant deposition along the axon, and an alternative method of calculating velocity was required. Analysis of accumulation of labeled material at double ligatures demonstrated both anterograde and retrograde transport of glycoproteins and gangliosides and allowed for the calculation of an anterograde transport rate of about 270 mm/day for each. Additional evidence of ganglioside transport is provided in that the TLC pattern of transported radioactive gangliosides accumulating at a ligature is significantly different from the pattern seen in the dorsal root ganglion or following intraneural administration of the labeled precursor. These data indicate that gangliosides are transported at the same rapid rate as glycoproteins but are subject to a more extensive exchange with stationary material than are glycoproteins. 相似文献
228.
Dinucleoside tetraphosphate variations in cultured tumor cells during their cell cycle and growth 总被引:3,自引:0,他引:3
Gilbert Moris Denise Meyer Georges Orfanoudakis Nicole Befort Jean-Pierre Ebel Pierre Remy 《Biochimie》1987,69(11-12):1217-1225
Asynchronous and synchronized cultures of A549 and HTC cells were used to detect possible, cell cycle or cell density specific variations in the intracellular pools of dinucleoside tetraphosphates (Ap4X). No important variations of the nucleotide pools were observed during cell growth. When HTC cells were released from mitotic arrest, a decrease by a factor of N3 Ap4X and ATP levels was observed when the cells entered the G1 phase. This decrease is essentially due to cell doubling. When A549 cells were released from an arrest at the G1/S boundary, the nucleotide pool size increased slightly during the G2 phase just before mitosis. This result is in agreement with both earlier data from our laboratory and the observed decrease in Ap4X pool after release from mitotic-arrested HTC cells. These results suggest that the Ap4X and ATP pools are only subjected to very small variations during the cell cycle, essentially in the G2 phase and after mitosis. 相似文献
229.
Human elongation factor 1α: a polymorphic and conserved multigene family with multiple chromosomal localizations 总被引:1,自引:0,他引:1
230.