全文获取类型
收费全文 | 2228篇 |
免费 | 144篇 |
专业分类
2372篇 |
出版年
2023年 | 7篇 |
2022年 | 21篇 |
2021年 | 43篇 |
2020年 | 27篇 |
2019年 | 34篇 |
2018年 | 57篇 |
2017年 | 27篇 |
2016年 | 72篇 |
2015年 | 100篇 |
2014年 | 101篇 |
2013年 | 170篇 |
2012年 | 187篇 |
2011年 | 174篇 |
2010年 | 102篇 |
2009年 | 93篇 |
2008年 | 141篇 |
2007年 | 132篇 |
2006年 | 128篇 |
2005年 | 109篇 |
2004年 | 114篇 |
2003年 | 103篇 |
2002年 | 90篇 |
2001年 | 25篇 |
2000年 | 14篇 |
1999年 | 13篇 |
1998年 | 29篇 |
1997年 | 13篇 |
1996年 | 20篇 |
1995年 | 14篇 |
1994年 | 18篇 |
1993年 | 23篇 |
1992年 | 17篇 |
1991年 | 16篇 |
1990年 | 21篇 |
1989年 | 5篇 |
1988年 | 11篇 |
1987年 | 6篇 |
1986年 | 6篇 |
1985年 | 15篇 |
1984年 | 6篇 |
1983年 | 7篇 |
1982年 | 7篇 |
1981年 | 11篇 |
1980年 | 6篇 |
1979年 | 10篇 |
1978年 | 7篇 |
1975年 | 3篇 |
1974年 | 4篇 |
1971年 | 2篇 |
1968年 | 2篇 |
排序方式: 共有2372条查询结果,搜索用时 0 毫秒
21.
Purification, Characterization, and Functional Role of a Novel Extracellular Protease from Pleurotus ostreatus 总被引:3,自引:0,他引:3 下载免费PDF全文
Gianna Palmieri Carmen Bianco Giovanna Cennamo Paola Giardina Gennaro Marino Maria Monti Giovanni Sannia 《Applied microbiology》2001,67(6):2754-2759
A new extracellular protease (PoSl; Pleurotus ostreatus subtilisin-like protease) from P. ostreatus culture broth has been purified and characterized. PoSl is a monomeric glycoprotein with a molecular mass of 75 kDa, a pI of 4.5, and an optimum pH in the alkaline range. The inhibitory profile indicates that PoSl is a serine protease. The N-terminal and three tryptic peptide sequences of PoSl have been determined. The homology of one internal peptide with conserved sequence around the Asp residue of the catalytic triad in the subtilase family suggests that PoSl is a subtilisin-like protease. This hypothesis is further supported by the finding that PoSl hydrolysis sites of the insulin B chain match those of subtilisin. PoSl activity is positively affected by calcium. A 10-fold decrease in the Km value in the presence of calcium ions can reflect an induced structural change in the substrate recognition site region. Furthermore, Ca2+ binding slows PoSl autolysis, triggering the protein to form a more compact structure. These effects have already been observed for subtilisin and other serine proteases. Moreover, PoSl protease seems to play a key role in the regulation of P. ostreatus laccase activity by degrading and/or activating different isoenzymes. 相似文献
22.
23.
Clonal descent and microevolution of Neisseria meningitidis during 30 years of epidemic spread 总被引:3,自引:0,他引:3
Giovanna Morelli Burkhard Malorny Kerstin Müller rea Seiler Jian-Fu Wang Jesus del Valle & Mark Achtman 《Molecular microbiology》1997,25(6):1047-1064
Serogroup A meningococci of subgroups III, IV-1 and IV-2 are probably descended from a common ancestor that existed in the nineteenth century. The 10.5 kb sequences spanning five distinct chromosomal loci, encoding cell-surface antigens, a secreted protease or housekeeping genes and intergenic regions, were almost identical in strains of those subgroups isolated in 1966, 1966 and 1917 respectively. During the subsequent two to three decades, all of these loci varied as a result of mutation, translocation or import of DNA from unrelated neisseriae. Thus, microevolution occurs frequently in naturally transformable bacteria. Many variants were isolated only once or within a single geographical location and disappeared thereafter. Other variants achieved genetic fixation within months or a few years. The speed with which sequence variation is either eliminated or fixed may reflect sequential bottlenecks associated with epidemic spread and contrasts with the results of phylogenetic analyses from bacteria that do not cause epidemics. 相似文献
24.
Abstract: The subcellular distribution of acyl-CoA: sn -glycerol-3-phosphate O-acyltransferase between brain mitochondria and microsomes was investigated. The activities associated with purified rat brain mitochondrial and microsomal preparations could be distinguished by differences in their acyl-CoA specificity, products of acylation, and sensitivity to N -ethylmaleimide, trypsin, acetone, and polymyxin B. It was concluded that both brain mitochondria and microsomes possess the acyltransferase. 相似文献
25.
Vincenzo Amico Rosario Currenti Giovanna Oriente Mario Piattelli Corrado Tringali 《Phytochemistry》1981,20(6):1451-1453
The major lipid component of the brown seaweed Zonaria tournefortii was identified as the acylphlorogluconol (all Z)-2′-icosa-5,8,11,14,17-pentae 相似文献
26.
Alessio Collalti Mark G. Tjoelker Günter Hoch Annikki Mkel Gabriele Guidolotti Mary Heskel Giai Petit Michael G. Ryan Giovanna Battipaglia Giorgio Matteucci Iain Colin Prentice 《Global Change Biology》2020,26(3):1739-1753
Two simplifying hypotheses have been proposed for whole‐plant respiration. One links respiration to photosynthesis; the other to biomass. Using a first‐principles carbon balance model with a prescribed live woody biomass turnover, applied at a forest research site where multidecadal measurements are available for comparison, we show that if turnover is fast the accumulation of respiring biomass is low and respiration depends primarily on photosynthesis; while if turnover is slow the accumulation of respiring biomass is high and respiration depends primarily on biomass. But the first scenario is inconsistent with evidence for substantial carry‐over of fixed carbon between years, while the second implies far too great an increase in respiration during stand development—leading to depleted carbohydrate reserves and an unrealistically high mortality risk. These two mutually incompatible hypotheses are thus both incorrect. Respiration is not linearly related either to photosynthesis or to biomass, but it is more strongly controlled by recent photosynthates (and reserve availability) than by total biomass. 相似文献
27.
Davide Marzi Patrizia Brunetti Giovanni Mele Nadia Napoli Lorenzo Cal Erica Spaziani Minami Matsui Simone De Panfilis Paolo Costantino Giovanna Serino Maura Cardarelli 《The Plant journal : for cell and molecular biology》2020,103(1):379-394
In Arabidopsis, stamen elongation, which ensures male fertility, is controlled by the auxin response factor ARF8, which regulates the expression of the auxin repressor IAA19. Here, we uncover a role for light in controlling stamen elongation. By an extensive genetic and molecular analysis we show that the repressor of light signaling COP1, through its targets HY5 and HYH, controls stamen elongation, and that HY5 – oppositely to ARF8 – directly represses the expression of IAA19 in stamens. In addition, we show that in closed flower buds, when light is shielded by sepals and petals, the blue light receptors CRY1/CRY2 repress stamen elongation. Coherently, at flower disclosure and in subsequent stages, stamen elongation is repressed by the red and far‐red light receptors PHYA/PHYB. In conclusion, different light qualities – sequentially perceived by specific photoreceptors – and the downstream COP1–HY5/HYH module finely tune auxin‐induced stamen elongation and thus male fertility. 相似文献
28.
Jian-Jun Jia Roni M Lahr Michael T Solgaard Bruno J Moraes Roberta Pointet An-Dao Yang Giovanna Celucci Tyson E Graber Huy-Dung Hoang Marius
R Niklaus Izabella A Pena Anne K Hollensen Ewan M Smith Malik Chaker-Margot Leonie Anton Christopher Dajadian Mark Livingstone Jaclyn Hearnden Xu-Dong Wang Yonghao Yu Timm Maier Christian K Damgaard Andrea J Berman Tommy Alain Bruno D Fonseca 《Nucleic acids research》2021,49(6):3461
29.
30.
Abstract Anemophylus dispersal of pollen grains in the Po Valley.—Results of phenological and aerobiological measurements with Castanea sativa pollen are presented. The data concerning the dispersal of this pollen in the Po Valley, show some features of the transport over hundred kilometer distances and give useful suggestions for application research. 相似文献