首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   4813篇
  免费   0篇
  2012年   188篇
  2011年   349篇
  2010年   144篇
  2009年   1篇
  2008年   303篇
  2007年   419篇
  2006年   447篇
  2005年   431篇
  2004年   451篇
  2003年   485篇
  2002年   474篇
  2001年   298篇
  2000年   513篇
  1999年   261篇
  1998年   34篇
  1997年   12篇
  1989年   1篇
  1988年   1篇
  1983年   1篇
排序方式: 共有4813条查询结果,搜索用时 296 毫秒
951.
952.
953.
954.
The major approaches to different lung cancer marker development are outlined in the review, including genetic, epigenetic, protein, transcryptomic, proteomic, metabolic, and miRNA markers. As far as epigenetic changes are among the earliest events in malignant transformation, methylated markers are thoroughly discussed. Special attention is given to minimally invasive tumor markers, which could be detected in easily accessible biological fluids, because they can be useful for screening and early diagnostics of cancer (before its clinical manifestation) as well as for verification of standard methods of diagnostics. Extracellular nucleic acids, circulating in blood (cirNA), are highlighted as the potential source of material for the early lung cancer diagnostics, prediction of antitumor treatment efficiency, post-treatment monitoring and disease prognosis.  相似文献   
955.
"Barbate roots" in tobacco and colza transgenic on lectin gene were obtained with the use of a wild strain of Agrobacterium rhizogenes 15834 transformed with pCAMBIA1305.1 plasmid containing the full-size lectin gene (psl) from the Pisum sativum. Influence of expression oflectin gene on colonization oftransgenic roots with symbiont of pea (Rhizobium leguminosarum) was investigated. The number of adhered bacteria onto the roots transformed with lectin gene was 14-fold and 37-fold higher in comparison with the control; this confirms the interaction of R. leguminosarum with pea lectin at the surface of the transformed roots of tobacco and colza. The developed experimental approach, based on the simulation of recognition processes and early symbiotic interactions with lectins of pea plants, may, in perspective, be used for obtaining stable associations of economically valuable, nonsymbiotrophic plant species with rhizobia.  相似文献   
956.
This review provides an analysis of recent data on the mechanisms of degradation of lignocellulosic materials and xenobiotics by basidiomycetes. Special attention is given to the analysis of the current state of research of ligninolytic enzymes and their involvement in the degradation ofxenobiotics. Data on the practical use of basidiomycetes for bioconversion of industrial wastes are systematized. The most promising areas of bioconversion technologies are considered, such as contaminated water purification (including wastewater), cleanup of soils contaminated with heavy metals and xenobiotics, and degradation of difficult-to-degrade substrates (lignin and lignocellulose wastes, low-energy coal, and synthetic polymers).  相似文献   
957.
Four cultures of fungi of the genus Penicillium belonging to Furcatum Pitt subgenus, such as P. citrinum Thom, 1910; P. corylophilum Dierckx, 1901; P. fellutanum Biourge, 1923; and P. waksmanii Zaleski, 1927, produced the ergot alkaloids, namely, agroclavine-I, and epoxyagroclavine-I; their N-N-dimers, such as dimer of epoxyagroclavine-I and the mixed dimer of epoxyagroclavine-I and agroclavine-I; and also quinoline metabolites, namely, quinocitrinin A and quinocitrinin B. Physiological and biochemical characteristics of the producers were studied. Optimal conditions for the biosynthesis of metabolome components were determined. Zinc additive to the medium stimulated the biosynthesis of the ergot alkaloids in all cases; citrinin production was increased only in P. citrinum, and that was suppressed in P. corylophinum, P. fellutanum, and P. waksmanii. This testifies that genes of the biosynthesis pathways are located in the different clusters of the producers.  相似文献   
958.
Destruction of a number of aromatic substrates by anaerobic microbial communities was studied. Active methanogenic microbial communities decomposing aminoaromatic acids and azo dyes into CH4 and CO2 were isolated. Products of primary conversion were found to be 2-hydroxybenzyl and benzyl alcohols gradually transforming into benzoate. It was shown that isolated microbial communities are capable of converting the initial substrates--benzyl alcohol, benzoate, salicylic acid, and golden yellow azo dye--into biogas without a lag-phase but with different velocities. Aromatic and linear intermediates of biodestruction of aromatic amines by obtained enrichment cultures were determined for the first time. Selective effect of aromatic substrates on a microbial community that was expressed in decrease in diversity and gradual change of dominant morphotypes was revealed.  相似文献   
959.
Research into ion-exchange properties of cell walls isolated from thallus of red seaweed Phyllophora crispa was carried out. Ion-exchange capacity and the swelling coefficient of the red alga cell walls were estimated at various pH values (from 2 to 12) and at constant ionic strength of a solution (10 mM). It was established that behavior of cell walls as ion-exchangers is caused by the presence in their matrix of two types of cation-exchange groups and amino groups. The amount of the functional group of each type was estimated, and the corresponding values of pK(a) were calculated. It can be assumed that ionogenic groups with pK(a) -5 are carboxyl groups of uronic acids, and ionogenic groups with pK(a) -7.5 are carboxyl groups of the proteins. Intervals of pH in which cation-exchange groups are ionized and can take part in exchange reactions with cations in the environment are defined. It was found that protein was a major component of cell wall polymeric matrix because its content was 36%.  相似文献   
960.
A microarray analytic system that uses a silicon chip with immobilized in microreactor test-system for multiplex analysis of DNA by real-time polymerase chain reaction (RT-PCR) was developed and optimized. We suggested the method of immobilization of PCR-components of a test-system, chose the stabilizer, and conducted the optimization of the composition of reaction mixture to achieve permanent stability of a microarray. We conducted optimization of preparation of samples using magnetic sorbent and indicated that, with 2.6 x 10(4) copies/ml, 60 min are necessary to obtain positive identification including time for preparation of model probes. The abilities of the created system were demonstrated on the example of microarray analysis of samples with different content of DNA, low absolute limits of identification (20 DNA copies in microreactor), and high reproducibility of the analysis.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号