全文获取类型
收费全文 | 804661篇 |
免费 | 94820篇 |
国内免费 | 958篇 |
出版年
2018年 | 7091篇 |
2017年 | 6761篇 |
2016年 | 9974篇 |
2015年 | 14645篇 |
2014年 | 16743篇 |
2013年 | 23223篇 |
2012年 | 27053篇 |
2011年 | 27517篇 |
2010年 | 18362篇 |
2009年 | 16823篇 |
2008年 | 24188篇 |
2007年 | 25048篇 |
2006年 | 23164篇 |
2005年 | 22443篇 |
2004年 | 22275篇 |
2003年 | 20965篇 |
2002年 | 20316篇 |
2001年 | 34893篇 |
2000年 | 35018篇 |
1999年 | 28054篇 |
1998年 | 10555篇 |
1997年 | 10777篇 |
1996年 | 10343篇 |
1995年 | 9638篇 |
1994年 | 9468篇 |
1993年 | 9353篇 |
1992年 | 23055篇 |
1991年 | 22379篇 |
1990年 | 22002篇 |
1989年 | 21448篇 |
1988年 | 19524篇 |
1987年 | 18749篇 |
1986年 | 17525篇 |
1985年 | 17203篇 |
1984年 | 14526篇 |
1983年 | 12578篇 |
1982年 | 9731篇 |
1981年 | 8794篇 |
1980年 | 8193篇 |
1979年 | 13679篇 |
1978年 | 10852篇 |
1977年 | 9838篇 |
1976年 | 9168篇 |
1975年 | 10181篇 |
1974年 | 11126篇 |
1973年 | 10895篇 |
1972年 | 9794篇 |
1971年 | 9046篇 |
1970年 | 7605篇 |
1969年 | 7458篇 |
排序方式: 共有10000条查询结果,搜索用时 13 毫秒
991.
M Hall D K Parker P L Grover J Y Lu N E Hopkins W L Alworth 《Chemico-biological interactions》1990,76(2):181-192
The effects of three aryl acetylenes, 1-ethynylpyrene (EP), 2-ethynylnaphthalene (EN) and 3-ethynylperylene (EPE), upon the metabolism of benzo[a]pyrene (BaP) by microsomes isolated from rat liver were investigated. These aryl acetylenes all inhibited the total metabolism of BaP. Formation of BaP 7,8-dihydrodiol and BaP tetrol products by microsomal preparations from rats that had been pretreated with 3-methylcholanthrene (3MC) were preferentially inhibited. The effects of EP upon the metabolism of BaP 7,8-dihydrodiol by microsomes from rat liver were also studied. This aryl acetylene strongly inhibited the formation of BaP tetrols from BaP 7,8-dihydrodiol by liver microsomes both from untreated rats and from rats pretreated with 3MC, but enhanced the conversion of the BaP dihydrodiol into other metabolites. 相似文献
992.
993.
994.
995.
996.
G C Randall 《Journal of developmental physiology》1988,10(1):77-83
The role of cortisol as a factor controlling the deposition of glycogen in the pig fetus was examined by infusing either a low dose (1 mg/day) or a high dose (3 mg/day) of cortisol into chronically-catheterized hypophysectomized fetal pigs for five days beginning on day 100-104 of gestation. After infusion, liver glycogen was significantly higher (P less than 0.05) and lung glycogen significantly lower (P less than 0.05) than in uninfused hypophysectomized litter mates although concentrations were significantly different from intact litter mates (P less than 0.05). Although skeletal and cardiac muscle content increased after infusion this difference was not significant. Changes in tissue glycogen content were similar for both the low and high rates of infusion. These observations indicate that exogenous cortisol alone is able to stimulate liver glycogen deposition and reverse the effect of hypophysectomy. Although other factors may be necessary for maximal response this suggests that cortisol is an important stimulant for liver glycogen deposition in the fetal pig. The effect of cortisol on muscle glycogen was equivocal suggesting that other hormones may play a more important role in this tissue. 相似文献
997.
Paracoenia fumosalis Cresson previously known only from the USA and Canada is recorded in the Palaearctic Region for the first time. The adults were collected near a thermal hydrosulfuric spring in the Geiser Valley in Kamchatka. A key to species of the genus Paracoenia occurring in Russia is given. 相似文献
998.
Mitochondrial DNA variation was examined in one of the southem most populations of domestic reindeer, inhabiting Tyva Republic (Tuva). In Tuvinian population sequence polymorphism of the mitochondrial DNA D-loop region was demonstrated. In a sample of 29 individuals 7 mitotypes were distinguished, pointing to the preservation of rather high level of genetic diversity in this population. 相似文献
999.
1000.
Mandy L. Roberts-Crowley Tora Mitra-Ganguli Liwang Liu Ann R. Rittenhouse 《Cell calcium》2009,45(6):589-601
Great skepticism has surrounded the question of whether modulation of voltage-gated Ca2+ channels (VGCCs) by the polyunsaturated free fatty acid arachidonic acid (AA) has any physiological basis. Here we synthesize findings from studies of both native and recombinant channels where micromolar concentrations of AA consistently inhibit both native and recombinant activity by stabilizing VGCCs in one or more closed states. Structural requirements for these inhibitory actions include a chain length of at least 18 carbons and multiple double bonds located near the fatty acid's carboxy terminus. Acting at a second site, AA increases the rate of VGCC activation kinetics, and in CaV2.2 channels, increases current amplitude. We present evidence that phosphatidylinositol 4,5-bisphosphate (PIP2), a palmitoylated accessory subunit (β2a) of VGCCs and AA appear to have overlapping sites of action giving rise to complex channel behavior. Their actions converge in a physiologically relevant manner during muscarinic modulation of VGCCs. We speculate that M1 muscarinic receptors may stimulate multiple lipases to break down the PIP2 associated with VGCCs and leave PIP2's freed fatty acid tails bound to the channels to confer modulation. This unexpectedly simple scheme gives rise to unanticipated predictions and redirects thinking about lipid regulation of VGCCs. 相似文献