全文获取类型
收费全文 | 3309篇 |
免费 | 320篇 |
出版年
2021年 | 53篇 |
2020年 | 22篇 |
2018年 | 36篇 |
2017年 | 31篇 |
2016年 | 60篇 |
2015年 | 86篇 |
2014年 | 104篇 |
2013年 | 137篇 |
2012年 | 160篇 |
2011年 | 174篇 |
2010年 | 100篇 |
2009年 | 94篇 |
2008年 | 131篇 |
2007年 | 137篇 |
2006年 | 149篇 |
2005年 | 122篇 |
2004年 | 116篇 |
2003年 | 107篇 |
2002年 | 94篇 |
2001年 | 78篇 |
2000年 | 79篇 |
1999年 | 61篇 |
1998年 | 53篇 |
1997年 | 36篇 |
1996年 | 28篇 |
1995年 | 26篇 |
1994年 | 28篇 |
1993年 | 34篇 |
1992年 | 56篇 |
1991年 | 45篇 |
1990年 | 56篇 |
1989年 | 55篇 |
1988年 | 41篇 |
1987年 | 60篇 |
1986年 | 75篇 |
1985年 | 63篇 |
1984年 | 64篇 |
1983年 | 74篇 |
1982年 | 63篇 |
1981年 | 67篇 |
1980年 | 68篇 |
1979年 | 53篇 |
1978年 | 44篇 |
1977年 | 32篇 |
1976年 | 30篇 |
1975年 | 25篇 |
1974年 | 34篇 |
1973年 | 33篇 |
1970年 | 24篇 |
1969年 | 19篇 |
排序方式: 共有3629条查询结果,搜索用时 15 毫秒
2.
3.
Selective increase in cytokeratin synthesis in cultured rat hepatocytes in response to hormonal stimulation 总被引:3,自引:0,他引:3
I Leroux-Nicollet M Noel H Baribault R Goyette N Marceau 《Biochemical and biophysical research communications》1983,114(2):556-563
Addition of a combination of insulin, dexamethasone and EGF at seeding time to cultured rat hepatocytes in serum-free medium caused a selective increase in the biosynthesis of particular cytokeratin components. This increase was prominent during the first day in culture. No significant increases were detected in the absence of hormones or in the presence of either hormones added alone or in pairs, except in the case of insulin plus dexamethasone, which yielded an effect close to that obtained with the three factors. Interestingly, the latter condition also maintained a high level of albumin production over a 6-day period in culture. 相似文献
4.
N. Rocks C. Estrella G. Paulissen F. Quesada‐Calvo C. Gilles M. M. Guéders C. Crahay J.‐M. Foidart P. Gosset A. Noel D. D. Cataldo 《Cell proliferation》2008,41(6):988-1001
Abstract. Objectives: The ADAMs (a disintegrin and metalloproteinase) enzymes compose a family of membrane‐bound proteins characterized by their multi‐domain structure and ADAM‐12 expression is elevated in human non‐small cell lung cancers. The aim of this study was to investigate the roles played by ADAM‐12 in critical steps of bronchial cell transformation during carcinogenesis. Materials and methods: To assess the role of ADAM‐12 in tumorigenicity, BEAS‐2B cells were transfected with a plasmid encoding human full‐length ADAM‐12 cDNA, and then the effects of ADAM‐12 overexpression on cell behaviour were explored. Treatment of clones with heparin‐binding epidermal growth factor (EGF)‐like growth factor (HB‐EGF) neutralizing antibodies as well as an EGFR inhibitor allowed the dissection of mechanisms regulating cell proliferation and apoptosis. Results: Overexpression of ADAM‐12 in BEAS‐2B cells promoted cell proliferation. ADAM‐12 overexpressing clones produced higher quantities of HB‐EGF in their culture medium which may rely on membrane‐bound HB‐EGF shedding by ADAM‐12. Targeting HB‐EGF activity with a neutralizing antibody abrogated enhanced cell proliferation in the ADAM‐12 overexpressing clones. In sharp contrast, targeting of amphiregulin, EGF or transforming growth factor‐α failed to influence cell proliferation; moreover, ADAM‐12 transfectants were resistant to etoposide‐induced apoptosis and the use of a neutralizing antibody against HB‐EGF activity restored rates of apoptosis to be similar to controls.Conclusions: ADAM‐12 contributes to enhancing HB‐EGF shedding from plasma membranes leading to increased cell proliferation and reduced apoptosis in this bronchial epithelial cell line. 相似文献
5.
6.
Noel R. Rawson 《BMJ (Clinical research ed.)》1929,2(3596):1084-1085
7.
Noradrenaline caused a prompt but transient increase in the rate of45Ca2+ efflux from isolated rat islets of Langerhans perifused in Ca2+ depleted medium. The response was modest in size and was unaffected by isosmotic replacement of NaCl with choline chloride or by inclusion of 0.5 mM dibutyryl cAMP in the perifusion medium, suggesting that it was not mediated by Na+: Ca2+ exchange nor by lowered cAMP. Despite its effect on45Ca2+ efflux, noradrenaline treatment did not alter the kinetics of45Ca2+ efflux in response to the muscarinic agonist, carbamylcholine, nor did it change the magnitude of the response to this agent. Simultaneous introduction of 20 mM glucose with noradrenaline prevented a rise in45Ca2+ efflux and indeed resulted in inhibition of45Ca2+ efflux. The data suggest that noradrenaline does not directly activate the mechanisms which regulate Ca2+ extrusion from islets cells, and they do not support a primary role for the Ca2+ efflux response in mediating adrenergic inhibition of insulin secretion. 相似文献
8.
9.
10.
D. C. Coleman R. V. Anderson C. V. Cole E. T. Elliott L. Woods M. K. Campion 《Microbial ecology》1977,4(4):373-380
Flows of biomass and respiratory carbon were studied in a series of propylene-oxide sterilized soil microcosms. One-half of the microcosms received three pulsed additions of 200 ppm glucose-carbon to mimic rhizosphere carbon inputs. Biotic variables were: bacteria (Pseudomonas) alone, or amoebae (Acanthamoeba) and nematodes (Mesodiplogaster) singly, or both combined in the presence of bacteria.Over the 24-day experiment, respiration was significantly higher in the microcosms containing the bacterial grazers. Biomass accumulation by amoebae was significantly higher than that by nematodes. The nematodes respired up to 30-fold more CO2 per unit biomass than did amoebae. Similar amounts of carbon flowed into both respiratory and biomass carbon in microcosms with fauna, compared with the bacteria-alone microcosms. However, partitioning of available carbon by the microfauna varied considerably, with little biomass production and relatively more CO2-C produced in the nematode-containing microcosms. The amoebae, in contrast, allocated more carbon to tissue production (about 40% assimilation efficiency) and correspondingly less to CO2. 相似文献