全文获取类型
收费全文 | 3127篇 |
免费 | 241篇 |
出版年
2023年 | 5篇 |
2022年 | 16篇 |
2021年 | 59篇 |
2020年 | 35篇 |
2019年 | 58篇 |
2018年 | 70篇 |
2017年 | 59篇 |
2016年 | 86篇 |
2015年 | 137篇 |
2014年 | 174篇 |
2013年 | 232篇 |
2012年 | 260篇 |
2011年 | 260篇 |
2010年 | 171篇 |
2009年 | 131篇 |
2008年 | 192篇 |
2007年 | 202篇 |
2006年 | 189篇 |
2005年 | 162篇 |
2004年 | 162篇 |
2003年 | 137篇 |
2002年 | 137篇 |
2001年 | 34篇 |
2000年 | 22篇 |
1999年 | 19篇 |
1998年 | 35篇 |
1997年 | 26篇 |
1996年 | 28篇 |
1995年 | 24篇 |
1994年 | 24篇 |
1993年 | 30篇 |
1992年 | 21篇 |
1991年 | 21篇 |
1990年 | 14篇 |
1989年 | 14篇 |
1988年 | 10篇 |
1987年 | 17篇 |
1986年 | 11篇 |
1985年 | 10篇 |
1984年 | 9篇 |
1983年 | 7篇 |
1982年 | 8篇 |
1981年 | 10篇 |
1978年 | 6篇 |
1977年 | 3篇 |
1976年 | 4篇 |
1975年 | 3篇 |
1974年 | 5篇 |
1973年 | 3篇 |
1969年 | 3篇 |
排序方式: 共有3368条查询结果,搜索用时 15 毫秒
1.
2.
3.
Luca Racca Andrea Villa Lukardis C. M. Wencker Marco Camaiti Hugues-Alexandre Blain Massimo Delfino 《Journal of morphology》2020,281(7):808-833
The skull osteology of Hierophis viridiflavus is here described and figured in detail on the basis of 18 specimens. The sample includes specimens from the ranges of both H. viridiflavus viridiflavus and H. viridiflavus carbonarius as well as specimens not identified at sub-specific level. The main characters that define H. viridiflavus in comparison to the parapatric congeneric species Hierophis gemonensis are wide maxillary diastema, basioccipital crest well distinct in three lobes and basioccipital process well marked. The foramina of the otoccipital and prootic, and the basioccipital process of the basioccipital are among the most ontogenetically variable characters, as indicated by two juvenile specimens included in the sample. A specimen-level phylogenetic analysis including H. gemonensis and other outgroups (overall 6 species, 26 specimens, 64 skull characters) recovered all H. viridiflavus specimens in one clade, indicating the presence of a clear phylogenetic signal in the applied characters. However, the resolution within the H. viridiflavus clade is poor the monophyly of H. viridiflavus carbonarius was retrieved, but not that of Hierophis v. viridiflavus. Probably due to the relatively high variability, the skull morphology does not support the recently proposed specific status of the two subspecies. 相似文献
4.
Hilary S. Callahan Massimo Pigliucci Carl D. Schlichting 《BioEssays : news and reviews in molecular, cellular and developmental biology》1997,19(6):519-525
The plastic response of phenotypic traits to environmental change is a common research focus in several disciplines - from ecology and evolutionary biology to physiology and molecular genetics. The use of model systems such as the flowering plant Arabidopsis thaliana has facilitated a dialogue between developmental biologists asking how plasticity is controlled (proximate causes) and organismal biologists asking why plasticity exists (ultimate causes). Researchers studying ultimate causes and consequences are increasingly compelled to reject simplistic, ‘black box’ models, while those studying proximate causes and mechanisms are increasingly obliged to subject their interpretations to ecological ‘reality checks.’ We review the successful multidisciplinary efforts to understand the phytochrome-mediated shade-avoidance and light-seeking responses of flowering plants as a pertinent example of convergence between evolutionary and molecular biology. In this example, the two-way exchange between reductionist and holist camps has been essential to rapid and sustained progress. This should serve as a model for future collaborative efforts towards understanding the responses of organisms to their constantly changing environments. 相似文献
5.
Alberto Buson Alessandro Negro Luigi Grassato Massimo Tagliaro Marina Basaglia Claudio Grandi Angelo Fontana Marco P. Nuti 《FEMS microbiology letters》1996,145(1):55-62
Abstract A clone positive for d-carbamoylase activity (2.7 kb Hin dIII- Bam H1 DNA fragment) was obtained by screening a genomic library of Agrobacterium radiobacter in Escherichia coli . This DNA fragment contains an open reading frame of 912 bp which is predicted to encode a peptide of 304 amino acids with a calculated molecular mass of 34247 Da. The d-carbamoylase gene. named cauA , was placed under the control of T7 RNA-dependent promoter and expressed in E. coli BL21 (DE3). After induction with isopropyl-thio-β-d-galactopyranoside, the synthesis of d-carbamoylase in E. coli reached about 40% of the total protein. The expressed protein was shown to possess a molecular mass, on SDS-PAGE, of 36 kDa and showed an enhanced allowed us to establish that a Pro14 →Leu14 exchange leads to an inactive enzyme species, while a Cys279 →Ser279 exchange did not impair the functional properties of the enxyme. 相似文献
6.
7.
Proteolytic maturation of insulin is a post-Golgi event which occurs in acidifying clathrin-coated secretory vesicles 总被引:48,自引:0,他引:48
The direct identification of the intracellular site where proinsulin is proteolytically processed into insulin has been achieved by immunocytochemistry using an insulin-specific monoclonal antibody. Insulin immunoreactivity is absent from the Golgi stack of pancreatic B-cells and first becomes detectable in clathrin-coated secretory vesicles released from the trans Golgi pole. Clathrin-coated secretory vesicles transform into mature noncoated secretory granules which contain the highest concentration of insulin immunoreactive sites. Maturation of clathrin-coated secretory vesicles is accompanied by a progressive acidification of the vesicular milieu, as evidenced by a cytochemical probe that accumulates in acidic compartments whereupon it can be revealed by immunocytochemistry. Thus packaging of the prohormone in secretory vesicles, and acidification of this compartment, are critical steps in the proper proteolytic maturation of insulin. 相似文献
8.
Amiloride selectively inhibits the urokinase-type plasminogen activator 总被引:24,自引:0,他引:24
The diuretic drug amiloride, an inhibitor of Na+ uptake, competitively inhibits the catalytic activity of the urokinase-type plasminogen activator (u-PA), with a Ki of 7 X 10(-6) M. Generation of plasmin, cleavage of peptide substrates, and interaction of u-PA with a specific macromolecular proteinase inhibitor are all prevented in the presence of the drug. In contrast, amiloride does not affect the activity of either tissue-type plasminogen activator, plasmin, plasma kallikrein or thrombin. The inhibition of u-PA by amiloride may be related to the previously reported inhibition of u-PA-type enzymes by Na+. Amiloride or related compounds could prove useful in selectively controlling u-PA-catalyzed extracellular proteolysis. 相似文献
9.
10.