全文获取类型
收费全文 | 742篇 |
免费 | 84篇 |
出版年
2022年 | 11篇 |
2021年 | 16篇 |
2020年 | 7篇 |
2019年 | 8篇 |
2018年 | 18篇 |
2017年 | 21篇 |
2016年 | 25篇 |
2015年 | 22篇 |
2014年 | 25篇 |
2013年 | 47篇 |
2012年 | 54篇 |
2011年 | 42篇 |
2010年 | 27篇 |
2009年 | 24篇 |
2008年 | 30篇 |
2007年 | 29篇 |
2006年 | 17篇 |
2005年 | 25篇 |
2004年 | 22篇 |
2003年 | 25篇 |
2002年 | 26篇 |
2001年 | 20篇 |
2000年 | 21篇 |
1999年 | 17篇 |
1998年 | 9篇 |
1996年 | 5篇 |
1993年 | 12篇 |
1992年 | 22篇 |
1991年 | 10篇 |
1990年 | 9篇 |
1989年 | 12篇 |
1988年 | 15篇 |
1987年 | 13篇 |
1986年 | 9篇 |
1985年 | 8篇 |
1984年 | 8篇 |
1983年 | 7篇 |
1981年 | 11篇 |
1980年 | 6篇 |
1979年 | 5篇 |
1978年 | 5篇 |
1977年 | 6篇 |
1976年 | 4篇 |
1975年 | 5篇 |
1974年 | 6篇 |
1973年 | 4篇 |
1972年 | 6篇 |
1970年 | 10篇 |
1969年 | 7篇 |
1967年 | 6篇 |
排序方式: 共有826条查询结果,搜索用时 15 毫秒
51.
52.
Rocio Acuna-Hidalgo Denny Schanze Ariana Kariminejad Ann Nordgren Mohamad Hasan Kariminejad Peter Conner Giedre Grigelioniene Daniel Nilsson Magnus Nordenskjöld Anna Wedell Christoph Freyer Anna Wredenberg Dagmar Wieczorek Gabriele Gillessen-Kaesbach Hülya Kayserili Nursel Elcioglu Siavash Ghaderi-Sohi Payman Goodarzi Hamidreza Setayesh Maartje van de Vorst Marloes Steehouwer Rolph Pfundt Birgit Krabichler Cynthia Curry Malcolm G. MacKenzie Kym M. Boycott Christian Gilissen Andreas R. Janecke Alexander Hoischen Martin Zenker 《American journal of human genetics》2014
53.
54.
55.
Background
Microbial hosts offer a number of unique advantages when used as production systems for both native and heterologous small-molecules. These advantages include high selectivity and benign environmental impact; however, a principal drawback is low yield and/or productivity, which limits economic viability. Therefore a major challenge in developing a microbial production system is to maximize formation of a specific product while sustaining cell growth. Tools to rationally reconfigure microbial metabolism for these potentially conflicting objectives remain limited. Exhaustively exploring combinations of genetic modifications is both experimentally and computationally inefficient, and can become intractable when multiple gene deletions or insertions need to be considered. Alternatively, the search for desirable gene modifications may be solved heuristically as an evolutionary optimization problem. In this study, we combine a genetic algorithm and elementary mode analysis to develop an optimization framework for evolving metabolic networks with energetically favorable pathways for production of both biomass and a compound of interest. 相似文献56.
Bräutigam A Bomke S Pfeifer T Karst U Krauss GJ Wesenberg D 《Metallomics : integrated biometal science》2010,2(8):565-570
A method for the identification and quantification of canonic and isoforms of phytochelatins (PCs) from Chlamydomonas reinhardtii was developed. After disulfide reduction with tris(2-carboxyethyl)phosphine (TCEP) PCs were derivatized with ferrocenecarboxylic acid (2-maleimidoyl)ethylamide (FMEA) in order to avoid oxidation of the free thiol functions during analysis. Liquid chromatography (LC) coupled to electrospray mass spectrometry (ESI-MS) and inductively coupled plasma-mass spectrometry (ICP-MS) was used for rapid and quantitative analysis of the precolumn derivatized PCs. PC(2-4), CysGSH, CysPC(2-4), CysPC(2)desGly, CysPC(2)Glu and CysPC(2)Ala were determined in the algal samples depending on the exposure of the cells to cadmium ions. 相似文献
57.
An S-adenosylmethionine synthetase gene (metK) from Streptomyces spectabilis was cloned into an expression plasmid under the control of an inducible T7 promoter and introduced into a strain of Escherichia coli (BAP1(pBP130/pBP144)) capable of producing the polyketide product 6-deoxyerythronolide B (6-dEB). The metK coexpression in BAP1(pBP130/pBP144) improved the specific production of 6-dEB from 10.86 to 20.08 mg l−1
. In an effort to probe the reason for this improvement, a series of gene deletion and expression experiments were conducted
based on a metK metabolic pathway that branches between propionyl-CoA (a 6-dEB precursor) and autoinducer compounds. The deletion and expression
studies suggested that the autoinducer pathway had a larger impact on improved 6-dEB biosynthesis. Supporting these results
were experiments demonstrating the positive effect conditioned media (the suspected location of the autoinducer compounds)
had on 6-dEB production. Taken together, the results of this study show an increase in heterologous 6-dEB production concomitant
with heterologous metK gene expression and suggest that the mechanism for this improvement is linked to native autoinducer compounds. 相似文献
58.
Aranda R Doménech E Rus AD Real JT Sastre J Viña J Pallardó FV 《Free radical research》2007,41(11):1195-1200
This study assessed the role of xanthine oxidase in vascular ageing. A positive correlation between xanthine oxidase activity and age was found in human plasma. Similar results were found in rat plasma. Xanthine oxidase expression and activity in homogenates from the aortic wall were significantly higher in samples from old rats than in their young counterparts (p < 0.01). In rat skeletal muscle homogenates both xanthine oxidase expression and activity showed a similar age-related profile. Superoxide production by xanthine oxidase in aortic rings was higher in aged rats. Uric acid, the final product of xanthine oxidase has been proposed as a risk factor for coronary heart disease and an independent marker of worse prognosis in patients with moderate-to-severe chronic heart failure. These results give a possible explanation for this correlation and underscore the role of xanthine oxidase in ageing. 相似文献
59.
Peña-Rico Miguel A. Bravo-D Humberto R. Roldan-Sabino Crisanto Castro-Cerritos Karla V. Huerta-Heredia Ariana Navarro-Mtz A. Karin 《Antonie van Leeuwenhoek》2022,115(1):89-102
Antonie van Leeuwenhoek - Bacillus thuringiensis is the major bioinsecticide worldwide produced due to the Cry protein activity. Several studies have been done to improve the... 相似文献
60.