全文获取类型
收费全文 | 9385篇 |
免费 | 825篇 |
国内免费 | 13篇 |
专业分类
10223篇 |
出版年
2023年 | 41篇 |
2022年 | 116篇 |
2021年 | 200篇 |
2020年 | 103篇 |
2019年 | 141篇 |
2018年 | 189篇 |
2017年 | 190篇 |
2016年 | 273篇 |
2015年 | 465篇 |
2014年 | 506篇 |
2013年 | 650篇 |
2012年 | 801篇 |
2011年 | 773篇 |
2010年 | 509篇 |
2009年 | 432篇 |
2008年 | 655篇 |
2007年 | 599篇 |
2006年 | 559篇 |
2005年 | 534篇 |
2004年 | 486篇 |
2003年 | 439篇 |
2002年 | 431篇 |
2001年 | 95篇 |
2000年 | 55篇 |
1999年 | 81篇 |
1998年 | 120篇 |
1997年 | 73篇 |
1996年 | 59篇 |
1995年 | 35篇 |
1994年 | 52篇 |
1993年 | 46篇 |
1992年 | 31篇 |
1991年 | 31篇 |
1990年 | 38篇 |
1989年 | 25篇 |
1988年 | 27篇 |
1987年 | 30篇 |
1986年 | 27篇 |
1985年 | 18篇 |
1984年 | 28篇 |
1983年 | 15篇 |
1982年 | 31篇 |
1981年 | 27篇 |
1980年 | 25篇 |
1979年 | 27篇 |
1978年 | 19篇 |
1977年 | 17篇 |
1974年 | 21篇 |
1972年 | 16篇 |
1971年 | 12篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
2.
The natural aversion of rats to ethanol was overcome by subjecting rats to immobilization stress for a two-week period during which increasing concentrations of ethanol were offered in the drinking water. The rats subjected to this regimen consumed 47% of total calories as ethanol, indefinitely, following removal of the stress. Ethanol was consumed at a rate of 17.1 g/kg body weight along with sufficient stock diet to assure adequate nutrition in the absence of ethanol. 相似文献
3.
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
4.
Vincent Anquetil Caroline Le Sommer Agn��s M��reau Sandra Hamon Hubert Lerivray Serge Hardy 《The Journal of biological chemistry》2009,284(47):32370-32383
Alternative splicing of 3′-terminal exons plays a critical role in gene expression by producing mRNA with distinct 3′-untranslated regions that regulate their fate and their expression. The Xenopus α-tropomyosin pre-mRNA possesses a composite internal/3′-terminal exon (exon 9A9′) that is differentially processed depending on the embryonic tissue. Exon 9A9′ is repressed in non-muscle tissue by the polypyrimidine tract binding protein, whereas it is selected as a 3′-terminal or internal exon in myotomal cells and adult striated muscles, respectively. We report here the identification of an intronic regulatory element, designated the upstream terminal exon enhancer (UTE), that is required for the specific usage of exon 9A9′ as a 3′-terminal exon in the myotome. We demonstrate that polypyrimidine tract binding protein prevents the activity of UTE in non-muscle cells, whereas a subclass of serine/arginine rich (SR) proteins promotes the selection of exon 9A9′ in a UTE-dependent way. Morpholino-targeted blocking of UTE in the embryo strongly reduced the inclusion of exon 9A9′ as a 3′-terminal exon in the endogenous mRNA, demonstrating the function of UTE under physiological circumstances. This strategy allowed us to reveal a splicing pathway that generates a mRNA with no in frame stop codon and whose steady-state level is translation-dependent. This result suggests that a non-stop decay mechanism participates in the strict control of the 3′-end processing of the α-tropomyosin pre-mRNA. 相似文献
5.
Sandra Danner Christiane Kirchhoff Richard Ivell 《Reproductive biology and endocrinology : RB&E》2009,7(1):67-14
Background
Post-meiotically expressed genes in the testis are essential for the proper progression of spermatogenesis, and yet, aside from the construction of individual transgenic mice using specific promoters to drive reporter plasmids, there are only very limited possibilities for relevant and quantitative analysis of gene promoters. This is due to the special nature of post-meiotic haploid cells, which to date are not represented in any appropriate cell-lines. This article reports the development of novel methodology using isolated and cultured rat seminiferous tubules in a multiwell format, into which promoter-reporter constructs can be introduced by a combination of microinjection and electroporation. 相似文献6.
7.
8.
Ante M. Krstulovi Laura Bertani-Dziedzic Sandra Bautista-Cerqueira Stanley E. Gitlow 《Journal of chromatography. B, Analytical technologies in the biomedical and life sciences》1982,227(2):379-389
We describe a direct analysis for the simultaneous quantitative determination of 4-hydroxy-3-methoxyphenylacetic (homovanillic) acid and other monoamine metabolites in human lumbar cerebrospinal fluid, utilizing reversed-phase high-performance liquid chromatography with amperometric detection. In addition, a rapid isocratic separation was developed for homovanillic acid in the presence of other endogenous compounds.Twenty-five unselected diagnostic specimens of human lumbar cerebrospinal fluid were extracted with ethyl acetate and subsequently analyzed using the described method. Chromatographic peaks were identified on the basis of retention behavior and ratio of responses at several oxidation potentials.Although our quantitative results correlate well with the literature values, the data were not interpreted clinically since samples were obtained from routine, diagnostic testing of patients admitted to the medical or neurologic services at the Mount Sinai Hospital. 相似文献
9.
10.