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   1063篇
  免费   109篇
  国内免费   1篇
  2023年   10篇
  2022年   24篇
  2021年   51篇
  2020年   23篇
  2019年   18篇
  2018年   41篇
  2017年   30篇
  2016年   63篇
  2015年   41篇
  2014年   66篇
  2013年   79篇
  2012年   74篇
  2011年   77篇
  2010年   43篇
  2009年   43篇
  2008年   51篇
  2007年   44篇
  2006年   56篇
  2005年   35篇
  2004年   41篇
  2003年   37篇
  2002年   20篇
  2001年   11篇
  2000年   13篇
  1999年   12篇
  1998年   7篇
  1996年   8篇
  1994年   6篇
  1992年   8篇
  1991年   8篇
  1990年   5篇
  1988年   4篇
  1987年   5篇
  1986年   7篇
  1985年   8篇
  1983年   8篇
  1982年   3篇
  1980年   5篇
  1979年   7篇
  1978年   5篇
  1977年   5篇
  1976年   7篇
  1975年   5篇
  1973年   3篇
  1972年   4篇
  1971年   6篇
  1970年   6篇
  1969年   12篇
  1968年   6篇
  1967年   3篇
排序方式: 共有1173条查询结果,搜索用时 0 毫秒
171.
172.
In Vitro Cellular & Developmental Biology - Plant - The OsRGLP1 gene was overexpressed under the control of CaMV 35S promoter in tomato (Solanum lycopersicum L.) plants using...  相似文献   
173.
We have previously determined that larval feeding experience with a feeding/oviposition deterrent modified the feeding responses of larvae and oviposition responses of subsequent moths. These behavioural changes were attributed to learning, but the possibility of chemical legacy could not be ruled out. In the present study, we have topically applied a feeding/oviposition deterrent plant extract from Hoodia gordonii (Masson) Sweet ex Decne (Asclepiadaceae) to larvae, pupae, and adults of Trichoplusia ni (Hübner) (Lepidoptera: Noctuidae) to determine whether the feeding response of larvae and oviposition response of subsequent female moths is similarly modified by chemicals applied to the external surface of the insect. Our results indicate that traces of the extract that may be present internally or externally on the larvae do not reduce the feeding deterrent response of larvae. Furthermore, traces of the extract in or on larvae, pupae, or adult moths did not alter oviposition choice of female moths, leading us to discount the role of experience through topical application in this study. The fact that feeding/oviposition choice was only influenced by prior feeding experience of the larvae and not by topical administration suggests that habituation via sensory stimulation through mouthpart chemosensilla is likely a central phenomenon. Continuous exposure of adult moths to the extract over a period of 7 days did not affect the oviposition response of the female moths, ruling out the role of adult experience on host-plant selection in T. ni . To the best of our knowledge, this is the first study to examine the role of experience via topical application of chemicals onto all life stages of the insect except the egg. Chemical legacy may not be playing a role in influencing the oviposition choices of female T. ni moths.  相似文献   
174.
The effects of N and P depletion on the production and structural characterization of the cellular carbohydrate polymers of the estuarine diatom Halamphora luciae in batch culture were examined using matrix-assisted laser desorption-ionization time-of flight mass spectrometry (MALDI-TOF MS) complemented with monosaccharide composition determination and structural analyses by methylation of aqueous extracted product. The MALDI MS analysis of the cells showed a similar profile in control and N- and P-depleted media, with a displacement to higher molecular weight for cells grown in depleted media. In the monosaccharide analyses, both nutrient depletion and culture ageing led to an increase in glucose content, indicating that MALDI-TOF MS in whole cells was detecting the changes in chrysolaminarin. The maxima for the ions from f/2-P and to a lesser extent in f/2-N were displaced to higher m/z values indicating a higher degree of polymerization (DP). Methylation analysis confirmed the presence of chrysolaminarin, a (1→3)-β-d-glucan with branching in C2 and C6, where the glucan backbone had a substitution every four glucose residues. The (1→3)-β-d-glucan was also detected in the cingule by fluorescence with aniline blue.  相似文献   
175.
176.
The genetic differentiation of teak meta-population in India was investigated in relation to geographical and climatic variations employing dominant ISSR markers followed by Bayesian statistical analysis to understand adaptability of the species. The analysis based on 290 teak genotypes representing 29 locations of its natural distribution and 43 ISSR loci exhibited an insignificant structure and low 2.76% LD (≥?0.1 R2 values, p?<?0.001) in teak meta-population. The genetic and geographical variables despite acting independently with each other resulted in three sub-population clusters in the meta-population. The geographical barrier played a significant role in direction/restriction of gene flow. The integration of spatial/climatic variables altered the clustering pattern of the teak meta-population with signature of the adaptation to the temperature and longitudinal gradients that was also verified by the similar adaptation pattern of meta-population towards predicted global climate modeling for year 2050. The findings can help tackle the sustainable management and conservation of the species and its survival quotient in threat of changing climatic conditions.  相似文献   
177.
1. [3alpha-(3)H]Cholesta-7,9-dien-3beta-ol is converted in high yield into cholesterol by a 10000g(av.) supernatant fraction of rat liver homogenate. 2. Incubation of cholesta-7,9-dien-3beta-ol with [4-(3)H]NADPH and rat liver microsomal fractions under anaerobic conditions resulted in (3)H being incorporated into the 14alpha-position of cholest-7-en-3beta-ol. 3. Under anaerobic conditions in the absence of NADPH cholesta-7,9-dien-3beta-ol was isomerized into cholesta-8,14-dien-3beta-ol by rat liver microsomal fractions.  相似文献   
178.
Bacillus strains have been widely used for the production of fibrinolytic enzymes having role in the treatment of cardiovascular disorders. Purification and overproduction of such enzymes has increased their usage in medical fields including metalloproteinases with the ability to degrade extracellular matrix (ECM). Camelysin, a neutral metalloproteinase has been isolated from different species of bacteria like Bacillus cereus, Bacillus anthracis, and Bacillus thuringiensis with fibrinolytic, collagenolytic and actin degradation activity. This project successfully demonstrated the presence of 734-bp coding DNA sequence (CDS) encoding a 20.72331 kDa camelysin gene in local strain of Bacillus thuringiensis containing a signal peptide with cleavage site between residues 19 and 20. The sequence was submitted to GenBank (KT023597) and the sequence showed high homology with the camelysin protein of closely related Bacillus species. The alignment of related proteins through ClustalW displayed difference of four amino acids (“Q” replaced by “P” at position 169 and at position 182–184, “NQE” replaced by “HLK”) in the isolated protein. Comparison including structural and functional analysis of camelysin sequences isolated from different Bacillus species was carried out using different bioinformatics tools and software. The information would help in better understanding the properties of camelysin protein and its role in pathogenicity and clinical treatments.  相似文献   
179.
180.
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