全文获取类型
收费全文 | 2246篇 |
免费 | 154篇 |
国内免费 | 235篇 |
出版年
2024年 | 7篇 |
2023年 | 49篇 |
2022年 | 118篇 |
2021年 | 190篇 |
2020年 | 126篇 |
2019年 | 138篇 |
2018年 | 131篇 |
2017年 | 109篇 |
2016年 | 142篇 |
2015年 | 201篇 |
2014年 | 167篇 |
2013年 | 229篇 |
2012年 | 240篇 |
2011年 | 198篇 |
2010年 | 114篇 |
2009年 | 78篇 |
2008年 | 83篇 |
2007年 | 56篇 |
2006年 | 48篇 |
2005年 | 28篇 |
2004年 | 27篇 |
2003年 | 10篇 |
2002年 | 20篇 |
2001年 | 17篇 |
2000年 | 12篇 |
1999年 | 16篇 |
1998年 | 8篇 |
1997年 | 14篇 |
1996年 | 7篇 |
1995年 | 7篇 |
1994年 | 6篇 |
1993年 | 4篇 |
1992年 | 11篇 |
1991年 | 8篇 |
1990年 | 5篇 |
1989年 | 4篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1986年 | 2篇 |
1985年 | 2篇 |
1983年 | 1篇 |
排序方式: 共有2635条查询结果,搜索用时 46 毫秒
171.
Zheng Ma Jinxiu Liu Xiaozhen Lin Xuping Shentu Yalin Bian Xiaoping Yu 《Folia microbiologica》2014,59(2):93-97
Toyocamycin exhibits effective biological activities for use against plant pathogenic fungi thanks to its structural similarity to nucleoside. It has been recognized as a promising agricultural antibiotic utilized in controlling the occurrence of plant diseases. In our previous study, a strain that was isolated was identified and designated as Streptomyces diastatochromogenes whose major secondary metabolite was toyocamycin, but the production was largely limited. Protoplast transformation is a useful technique in the improvement of streptomycete. In this study, we optimized some key factors necessary for protoplast formation, regeneration, and transformation of S. diastatochromogenes. When mycelium was cultivated in CP medium with 1 % glycine, harvested at 48 h old, and then treated with 3 mg lysozyme/mL in P buffer for 1 h, the greatest regeneration frequency (42.5 %) of protoplasts was obtained. By using 1?×?109/mL protoplasts with polyethylene glycol 1000 at a concentration of 30 % (w/v), the best performance of protoplast transformation efficiency was 4.8?×?103/μg DNA transformants. 相似文献
172.
173.
The histone acetyltransferase MOF overexpression blunts cardiac hypertrophy by targeting ROS in mice
Weiwei Qiao Weili Zhang Yusheng GaiLan Zhao Juexin Fan 《Biochemical and biophysical research communications》2014
Imbalance between histone acetylation/deacetylation critically participates in the expression of hypertrophic fetal genes and development of cardiac hypertrophy. While histone deacetylases play dual roles in hypertrophy, current evidence reveals that histone acetyltransferase such as p300 and PCAF act as pro-hypertrophic factors. However, it remains elusive whether some histone acetyltransferases can prevent the development of hypertrophy. Males absent on the first (MOF) is a histone acetyltransferase belonging to the MYST (MOZ, Ybf2/Sas3, Sas2 and TIP60) family. Here in this study, we reported that MOF expression was down-regulated in failing human hearts and hypertrophic murine hearts at protein and mRNA levels. To evaluate the roles of MOF in cardiac hypertrophy, we generated cardiac-specific MOF transgenic mice. MOF transgenic mice did not show any differences from their wide-type littermates at baseline. However, cardiac-specific MOF overexpression protected mice from transverse aortic constriction (TAC)-induced cardiac hypertrophy, with reduced radios of heart weight (HW)/body weight (BW), lung weight/BW and HW/tibia length, decreased left ventricular wall thickness and increased fractional shortening. We also observed lower expression of hypertrophic fetal genes in TAC-challenged MOF transgenic mice compared with that of wide-type mice. Mechanically, MOF overexpression increased the expression of Catalase and MnSOD, which blocked TAC-induced ROS and ROS downstream c-Raf-MEK-ERK pathway that promotes hypertrophy. Taken together, our findings identify a novel anti-hypertrophic role of MOF, and MOF is the first reported anti-hypertrophic histone acetyltransferase. 相似文献
174.
Design and selection of trap color for capture of the tea leafhopper,Empoasca vitis,by orthogonal optimization 总被引:2,自引:0,他引:2
Lei Bian Xiao‐Ling Sun Zong‐Xiu Luo Zheng‐Qun Zhang Zong‐Mao Chen 《Entomologia Experimentalis et Applicata》2014,151(3):247-258
The tea leafhopper, Empoasca vitis (Göthe) (Hemiptera: Cicadellidae), is a major pest of the tea plant, Camellia sinensis (L.) O. Kuntze (Theaceae). In this study, the RGB color model was used to describe the colors of sticky traps. The most effective color for attraction of E. vitis was investigated by orthogonal optimization. The selected color was verified in tea gardens and the most effective height for positioning of color sticky traps for capturing tea leafhoppers was investigated. After the determination of the effect of the three color parameters and their interactions by orthogonal optimization, the color gold (RGB: 255, 215, 0) was selected as the most effective color to trap tea leafhoppers. In tea gardens, more leafhoppers were captured using gold sticky traps (RGB: 226, 204, 4) than using commercially available yellow sticky traps. The most effective height of gold sticky traps for trapping leafhoppers was 40–60 cm above the tea canopy. Few lady beetles were captured at this height. We conclude that the orthogonal optimization method is a convenient and efficient method to screen digitally generated colors for attracting and trapping of pests. 相似文献
175.
Xiaoliang Liang Yan Bian Xiao-Feng Tang Gengfu Xiao Bing Tang 《Applied microbiology and biotechnology》2010,87(3):999-1006
WF146 protease, a thermophilic subtilase from thermophile Bacillus sp. WF146, suffers excessive autolysis in the presence of reducing agents. In this report, two autolytic sites of WF146 protease
were modified by site-directed mutagenesis. The introduction of prolines into the autolytic sites increased the autolysis
resistance of the enzyme under reducing conditions. The double mutant N63P/A66P displayed a 2.8-fold longer half-life at 80°C
and higher hydrolytic activities than wild-type enzyme toward soluble (casein) and insoluble (keratin azure) substrates at
high temperatures. In the presence of reducing agents, N63P/A66P was able to degrade feather at 80°C (∼3 h), with hydrolysis
efficiency comparable to that of proteinase K at 50°C (∼24 h). Meanwhile, the mutant N63P/A66P had the ability to hydrolyze
PrPSc-like prion protein at high temperatures. In virtue of these properties, N63P/A66P is of great interest to be used in recycling
of keratinous wastes, such as feather, and disinfection of medical apparatus. In addition, our study may provide useful information
needed to explore keratinolytic potential of thermophilic subtilases, even if they are produced by non-keratinolytic microorganisms. 相似文献
176.
Marina L Kozak Alejandro Chavez Weiwei Dang Shelley L Berger Annie Ashok Xiaoge Guo F Brad Johnson 《The EMBO journal》2010,29(1):158-170
Changes in telomere chromatin have been linked to cellular senescence, but the underlying mechanisms and impact on lifespan are unclear. We found that inactivation of the Sas2 histone acetyltransferase delays senescence in Saccharomyces cerevisiae telomerase (tlc1) mutants through a homologous recombination‐dependent mechanism. Sas2 acetylates histone H4 lysine 16 (H4K16), and telomere shortening in tlc1 mutants was accompanied by a selective and Sas2‐dependent increase in subtelomeric H4K16 acetylation. Further, mutation of H4 lysine 16 to arginine, which mimics constitutively deacetylated H4K16, delayed senescence and was epistatic to sas2 deletion, indicating that deacetylated H4K16 mediates the delay caused by sas2 deletion. Sas2 normally prevents the Sir2/3/4 heterochromatin complex from leaving the telomere and spreading to internal euchromatic loci. Senescence was delayed by sir3 deletion, but not sir2 deletion, indicating that senescence delay is mediated by release of Sir3 specifically from the telomere repeats. In contrast, sir4 deletion sped senescence and blocked the delay conferred by sas2 or sir3 deletion. We thus show that manipulation of telomere chromatin modulates senescence caused by telomere shortening. 相似文献
177.
Genome-wide analysis of primary auxin-responsive Aux/IAA gene family in maize (Zea mays. L.) 总被引:1,自引:0,他引:1
Yijun Wang Dexiang Deng Yunlong Bian Yanping Lv Qin Xie 《Molecular biology reports》2010,37(8):3991-4001
The phytohormone auxin is important in various aspects of organism growth and development. Aux/IAA genes encoding short-lived nuclear proteins are responsive primarily to auxin induction. Despite their physiological importance, systematic analysis of Aux/IAA genes in maize have not yet been reported. In this paper, we presented the isolation and characterization of maize Aux/IAA genes in whole-genome scale. A total of 31 maize Aux/IAA genes (ZmIAA1 to ZmIAA31) were identified. ZmIAA genes are distributed in all the maize chromosomes except chromosome 2. Aux/IAA genes expand in the maize genome partly due to tandem and segmental duplication events. Multiple alignment and motif display results revealed major maize Aux/IAA proteins share all the four conserved domains. Phylogenetic analysis indicated Aux/IAA family can be divided into seven subfamilies. Putative cis-acting regulatory DNA elements involved in auxin response, light signaling transduction and abiotic stress adaption were observed in the promoters of ZmIAA genes. Expression data mining suggested maize Aux/IAA genes have temporal and spatial expression pattern. Collectively, these results will provide molecular insights into the auxin metabolism, transport and signaling research. 相似文献
178.
Huaping Lei Yonggang Wang Fengyin Liang Weiwei Su Yifan Feng Xiaoling Guo Ning Wang 《Biochemical Systematics and Ecology》2010
Essential oils were isolated from the leaves of Platycladus orientalis growing in 16 areas of China. The essential oils were analyzed by gas chromatography and gas chromatography-mass spectrometry. In total, 98 volatile compounds were identified. Chemical variability in essential oil composition was evaluated using cluster analysis and principal component analysis. The two analyses led to the identification of four chemotypes: α-pinene, α-pinene/3-carene, cedrol, and cedrol/terpinyl acetate. Geographically, the populations growing in close proximity had similar essential oil composition. The chemical variability could possibly be attributed to genetic and environmental factors. 相似文献
179.
180.
Girijavallabhan VM Chen L Dai C Feltz RJ Firmansjah L Li D Kim SH Kozlowski JA Lavey BJ Kosinski A Piwinski JJ Popovici-Muller J Rizvi R Rosner KE Shankar BB Shih NY Siddiqui MA Tong L Wong MK Yang DY Yang L Yu W Zhou G Guo Z Orth P Madison V Bian H Lundell D Niu X Shah H Sun J Umland S 《Bioorganic & medicinal chemistry letters》2010,20(24):7283-7287
Our research on hydantoin based TNF-α converting enzyme (TACE) inhibitors has led to an acetylene containing series that demonstrates sub-nanomolar potency (K(i)) as well as excellent activity in human whole blood. These studies led to the discovery of highly potent TACE inhibitors with good DMPK profiles. 相似文献