全文获取类型
收费全文 | 10551篇 |
免费 | 1014篇 |
国内免费 | 26篇 |
出版年
2023年 | 41篇 |
2022年 | 55篇 |
2021年 | 174篇 |
2020年 | 129篇 |
2019年 | 171篇 |
2018年 | 225篇 |
2017年 | 206篇 |
2016年 | 309篇 |
2015年 | 536篇 |
2014年 | 561篇 |
2013年 | 691篇 |
2012年 | 848篇 |
2011年 | 735篇 |
2010年 | 483篇 |
2009年 | 468篇 |
2008年 | 646篇 |
2007年 | 584篇 |
2006年 | 521篇 |
2005年 | 463篇 |
2004年 | 447篇 |
2003年 | 402篇 |
2002年 | 383篇 |
2001年 | 231篇 |
2000年 | 203篇 |
1999年 | 174篇 |
1998年 | 93篇 |
1997年 | 81篇 |
1996年 | 65篇 |
1995年 | 90篇 |
1994年 | 51篇 |
1993年 | 57篇 |
1992年 | 102篇 |
1991年 | 99篇 |
1990年 | 101篇 |
1989年 | 99篇 |
1988年 | 91篇 |
1987年 | 86篇 |
1986年 | 79篇 |
1985年 | 82篇 |
1984年 | 68篇 |
1983年 | 54篇 |
1982年 | 41篇 |
1980年 | 41篇 |
1979年 | 57篇 |
1978年 | 59篇 |
1977年 | 39篇 |
1976年 | 44篇 |
1975年 | 53篇 |
1974年 | 45篇 |
1973年 | 44篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
Chi Ho Chan Caleb E. Levar Lori Zacharoff Jonathan P. Badalamenti Daniel R. Bond 《Applied and environmental microbiology》2015,81(20):7178-7186
Metal reduction by members of the Geobacteraceae is encoded by multiple gene clusters, and the study of extracellular electron transfer often requires biofilm development on surfaces. Genetic tools that utilize polar antibiotic cassette insertions limit mutant construction and complementation. In addition, unstable plasmids create metabolic burdens that slow growth, and the presence of antibiotics such as kanamycin can interfere with the rate and extent of Geobacter biofilm growth. We report here genetic system improvements for the model anaerobic metal-reducing bacterium Geobacter sulfurreducens. A motile strain of G. sulfurreducens was constructed by precise removal of a transposon interrupting the fgrM flagellar regulator gene using SacB/sucrose counterselection, and Fe(III) citrate reduction was eliminated by deletion of the gene encoding the inner membrane cytochrome imcH. We also show that RK2-based plasmids were maintained in G. sulfurreducens for over 15 generations in the absence of antibiotic selection in contrast to unstable pBBR1 plasmids. Therefore, we engineered a series of new RK2 vectors containing native constitutive Geobacter promoters, and modified one of these promoters for VanR-dependent induction by the small aromatic carboxylic acid vanillate. Inducible plasmids fully complemented ΔimcH mutants for Fe(III) reduction, Mn(IV) oxide reduction, and growth on poised electrodes. A real-time, high-throughput Fe(III) citrate reduction assay is described that can screen numerous G. sulfurreducens strain constructs simultaneously and shows the sensitivity of imcH expression by the vanillate system. These tools will enable more sophisticated genetic studies in G. sulfurreducens without polar insertion effects or need for multiple antibiotics. 相似文献
993.
Sisi Patricia Lolita Ameria Hye Sook Jung Hee Sook Kim Sang Soo Han Hak Sung Kim Jin Ho Lee 《Biotechnology letters》2015,37(8):1637-1644
Objective
To examine the role of a gene encoding flavin-containing monooxygenase (cFMO) from Corynebacterium glutamicum ATCC13032 when cloned and expressed in Escherichia coli for the production of indigo pigments.Results
The blue pigments produced by recombinant E. coli were identified as indigo and indirubin. The cFMO was purified as a fused form with maltose-binding protein (MBP). The enzyme was optimal at 25 °C and pH 8. From absorption spectrum analysis, the cFMO was classified as a flavoprotein. FMO activity was strongly inhibited by 1 mM Cu2+ and recovered by adding 1–10 mM EDTA. The enzyme catalyzed the oxidation of TMA, thiourea, and cysteamine, but not glutathione or cysteine. MBP-cFMO had an indole oxygenase activity through oxygenation of indole to indoxyl. The recombinant E. coli produced 685 mg indigo l?1 and 103 mg indirubin l?1 from 2.5 g l-tryptophan l?1.Conclusion
The results suggest the cFMO can be used for the microbial production of both indigo and indirubin.994.
NFIL3 Suppresses Hypoxia‐induced Apoptotic Cell Death by Targeting the Insulin‐like Growth Factor 2 Receptor 下载免费PDF全文
995.
Kim Bo Kyung Joo HuiTae Song Ho Jung Yang Eun Jin Lee Sang Hoon Hahm Doshik Rhee Tae Siek Lee Sang H. 《Polar Biology》2015,38(3):319-331
Polar Biology - To better estimate annual primary production in the Amundsen Sea, which is one of the highest productivity regions in the Southern Ocean, the seasonal variations in carbon and... 相似文献
996.
997.
998.
Development of HPLC Chiral Stationary Phases Based on (+)‐(18‐Crown‐6)‐2,3,11,12‐tetracarboxylic Acid and Their Applications 下载免费PDF全文
Myung Ho Hyun 《Chirality》2015,27(9):576-588
Crown ether‐based chiral stationary phases (CSPs) have been known to be useful for the resolution of racemic primary amino compounds. In particular, CSPs based on (+)‐(18‐crown‐6)‐2,3,11,12‐tetracarboxylic acid have been reported to be useful for the resolution of secondary amino compounds as well as primary amino compounds. In this article, the process of developing various CSPs based on (+)‐(18‐crown‐6)‐2,3,11,12‐tetracarboxylic acid to improve the chiral recognition efficiency and/or the stability of the CSPs and their applications to the resolution of various primary and nonprimary amino compounds are reviewed. Chirality 27:576–588, 2015. © 2015 Wiley Periodicals, Inc. 相似文献
999.
Pai-An Hwang Yu-Lan Hung Yi-Kuan Tsai Shih-Yung Chien Zwe-Ling Kong 《Cytotechnology》2015,67(4):653-660
Diabetes is one of the most prevalent chronic diseases globally. In this study, major polyphenols (17.35 ± 0.93–36.66 ± 2.01 mg/g) and minor fucoxanthin (non detected 15.12 ± 0.09 mg/g) were isolated from water, ethanol, and acetone extracts (WES, EES, and AES, respectively) of Sargassum hemiphyllum. Inhibition of α-amylase, α-glucosidase, sucrose, and maltase activities and stimulation of insulin secretion was greater with AES than with WES or EES and correlated with polyphenol and fucoxanthin concentrations in extracts. Moreover, 250 μg/ml EES and AES significantly increased insulin secretion in the presence of 25 mg/ml glibenclamide to higher levels than those obtained with 50 mg/ml glibenclamide. None of the extracts exhibited cytotoxicity, exacerbated the side effects of glibenclamide, or inhibited glibenclamide-induced insulin secretion. These results suggested that the S. hemiphyllum extracts WES, EES, and AES could be used as pharmaceuticals and functional foods to reduce dosages of synthetic diabetes drugs. 相似文献
1000.