全文获取类型
收费全文 | 4120篇 |
免费 | 226篇 |
国内免费 | 3篇 |
专业分类
4349篇 |
出版年
2022年 | 27篇 |
2021年 | 47篇 |
2020年 | 31篇 |
2019年 | 45篇 |
2018年 | 71篇 |
2017年 | 46篇 |
2016年 | 85篇 |
2015年 | 160篇 |
2014年 | 150篇 |
2013年 | 214篇 |
2012年 | 231篇 |
2011年 | 252篇 |
2010年 | 164篇 |
2009年 | 153篇 |
2008年 | 232篇 |
2007年 | 235篇 |
2006年 | 230篇 |
2005年 | 240篇 |
2004年 | 248篇 |
2003年 | 193篇 |
2002年 | 216篇 |
2001年 | 74篇 |
2000年 | 53篇 |
1999年 | 79篇 |
1998年 | 68篇 |
1997年 | 41篇 |
1996年 | 37篇 |
1995年 | 35篇 |
1994年 | 33篇 |
1993年 | 16篇 |
1992年 | 54篇 |
1991年 | 46篇 |
1990年 | 45篇 |
1989年 | 47篇 |
1988年 | 47篇 |
1987年 | 42篇 |
1986年 | 41篇 |
1985年 | 35篇 |
1984年 | 30篇 |
1983年 | 31篇 |
1982年 | 26篇 |
1981年 | 16篇 |
1980年 | 16篇 |
1979年 | 16篇 |
1978年 | 16篇 |
1977年 | 21篇 |
1976年 | 21篇 |
1975年 | 19篇 |
1974年 | 11篇 |
1972年 | 9篇 |
排序方式: 共有4349条查询结果,搜索用时 0 毫秒
21.
22.
Y Hirata M Uchihashi T Fujita S Matsukura T Motoyama M Kaku K Koshimizu 《Endocrinologia japonica》1983,30(5):601-607
Using seventeen human tumor cell lines derived from a variety of tissues, specific binding sites for epidermal growth factor (EGF), a mouse submandibular gland-derived growth factor, has been characterized. A significant amount of membrane-bound EGF receptors, although considerably varied, was demonstrated in all the tumor cell lines studied. Epidermoid carcinoma appeared to have more EGF receptors than adenocarcinoma. One small cell carcinoma of the lung, one choriocarcinoma of the stomach and three bone tumors also possessed EGF receptors comparable to those of epidermoid carcinoma, while one adenoacanthoma of the stomach had less EGF receptors comparable to adenocarcinoma. Among a variety of phorbol esters tested, tetradecanoyl phorbol acetate, a potent tumor promotor, was shown to be the most effective compound in inhibiting 125I-labeled EGF binding to its receptors. Our results indicate that human tumor cells contain varying amounts of membrane-bound receptors for EGF and that phorbol esters interact with these EGF receptor sites. However, the relationship between EGF receptor sites on tumor cells and cellular proliferation and/or differentiation awaits further study. 相似文献
23.
Microiontophoretic study was performed to elucidate dopaminergic mechanism in the nucleus accumbens (Acc) of rats anesthetized with chloral hydrate. Iontophoretically applied dopamine produced an inhibition of glutamate-induced firing in 28 (62%) out of 45 Acc neurons tested. The dopamine-induced inhibition of 14 Acc neurons was clearly antagonized by simultaneous application of haloperidol, and a partial antagonism by sulpiride was observed in 3 out of 10 Acc neurons. These results indicate that dopamine produces an inhibition of the Acc neuron and that, compared to haloperidol, sulpiride is a less potent blocker of the postsynaptic dopamine receptor involved in the dopamine-induced inhibition. 相似文献
24.
Apple trees ( Malus pumila Mill . var. domestica Fuji/ Malus prunifolia rootstock) showed a high susceptibility to bitter pit when supplyed with ammonium salt instead of nitrate (control) in the nutrient solution. When apple fruit was affected by bitter pit, a lower calcium as well as a higher nitrogen and ammonium-nitrogen contents was observed in the fruit flesh near the calyx end. The activity of the mitochondrial Ca2+ -uptake of the fruit flesh near the calyx end was higher when the tree was grown with ammonium salt than when grown with nitrate. Both the activities of succinate: cytochrome c oxidoreductase and the mitochondrial Ca2+ -uptake per g of tissue were higher in affected fruit than in healthy fruit. Each of chlorpromazine, N-(6-aminohexyl)-5-chloro-l-napthalenesulfonamide (W-7) and N-(6-aminohexyl)-l-naphthalenesulfonamide (W-5), calmodulin antagonists, was infiltrated into the fruit for 20 min under reduced pressure (about 1 × 104 Pa). Few days later, numerous bitter pit-like spots were observed in both fruit treated with W-7 and chlorpromazine, while only a few spots were observed after the infiltration with W-5, a less potent calmodulin antagonist. A possible mechanism for the occurrence of bitter pit is discussed. 相似文献
25.
26.
27.
28.
Masashi Yamaguchi Theodore Yanos Tomoko Yamaguchi Abel Lajtha 《Developmental neurobiology》1969,1(4):419-433
When rat sciatic nerves were incubated with C14l-lysine, l- or d-glutamate, or d-l γ-aminoisobutyrate, the labeled compounds penetrated the nerve, and the level of lysine and leucine after 1 hr was higher in the nerve than in the medium. The level increased with time, and at 24 hr glutamate levels also were higher in the nerve than in the medium. Lowering the temperature strongly inhibited uptake, while other conditions such as absence of glucose, absence of sodium, or the presence of cyanide inhibited uptake by nerve less than uptake by brain slices. The uptake against a concentration gradient, and inhibitions of this uptake by metabolic inhibitors and by structural analogs, were interpreted as showing the presence of transport processes for amino acids in peripheral nerves with characteristics similar to such transport processes in the central nervous system. 相似文献
29.
Participation of P-450 in 7 alpha-hydroxylation of cholesterol 总被引:1,自引:0,他引:1
30.
Isolated microspores of Chinese cabbage (Brassica campestris ssp. pekinensis) were incubated in modified NN medium containing 10% sucrose in darkness at 33°C for one day followed by culture at 25°C. After 14 days of culture, microspores developed into embryos ranging from globular to cotyledonary stage. Plants were regenerated after transfer of embryos to medium containing 3% sucrose and no plant growth regulators.Abbreviations NN
Nitsch and Nitsch
- MS
Murashige and Skoog
- NAA
naphthaleneacetic acid
- BA
6-benzylaminopurine 相似文献