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   164篇
  免费   7篇
  国内免费   1篇
林业   4篇
农学   5篇
  63篇
综合类   18篇
农作物   16篇
水产渔业   10篇
畜牧兽医   42篇
园艺   1篇
植物保护   13篇
  2021年   3篇
  2020年   1篇
  2019年   2篇
  2018年   4篇
  2017年   2篇
  2016年   8篇
  2015年   2篇
  2014年   3篇
  2013年   8篇
  2012年   14篇
  2011年   19篇
  2010年   13篇
  2009年   16篇
  2008年   7篇
  2007年   9篇
  2006年   8篇
  2005年   6篇
  2004年   10篇
  2003年   2篇
  2002年   2篇
  2001年   4篇
  2000年   3篇
  1999年   3篇
  1997年   3篇
  1996年   1篇
  1993年   1篇
  1991年   1篇
  1990年   3篇
  1989年   1篇
  1987年   1篇
  1981年   1篇
  1979年   1篇
  1975年   2篇
  1974年   1篇
  1969年   2篇
  1965年   2篇
  1963年   2篇
  1945年   1篇
排序方式: 共有172条查询结果,搜索用时 15 毫秒
161.
Improving fruit farm profitability through integrated pest management (IPM) programs is always an important issue to modern agriculture systems. In order to enhance IPM programs against Bactrocera dorsalis, an automatic infield monitoring system is required to efficiently capture long-term and up-to-the-minute environmental fluctuations in a fruit farm. In this study, a remote agro-ecological monitoring system built upon wireless sensor networks has been developed to provide precision agriculture (PA) services with large-scale, long-distance, long-term, scalable, and real-time infield data collection capabilities. Historical data with spatial information is available through a web-based decision support program built upon a database. Pest population forecast results are also provided so that farmers and government officials would be able to accurately respond to infield variations. Compared with the previous version of the system, various useful functions have been added into the system, and its accuracy has been improved when measuring different parameters in the field. The system could provide a valuable framework for farmers and pest control officials to analyze the relations between population dynamics of the fruit fly and meteorological events. Based on the analysis, a better insect pest risk assessment and accurate decision-making strategy can be made as an aid to PA against B. dorsalis.  相似文献   
162.
A humoral response of Japanese eel, Anguilla japonica Temminck & Schlegel, to the microsporean Pleistophora anguillarum Hoshina was demonstrated using immunoblotting and an enzyme-linked immunosorbent assay (ELISA). Japanese eel immunoglobulin was purified by affinity chromatography. The immunoglobulin was composed of 25-kDa light chains and 72-kDa heavy chains. The ELISA values of P. anguillarum antibodies in naturally infected fish sera were significantly higher than those of clinically healthy fish. Spore proteins from the microsporean were separated by electrophoresis and subjected to analysis by Western blot. Sera from naturally infected fish showed different reaction patterns to the spore proteins. While the sera randomly selected from naturally infected eels all showed a significant positive reaction to P. anguillarum antigens, the mucus from only three out of the nine infected eels reacted positively in the ELISA test. Subsequent analyses indicated that there was no significant difference in the amount of mucus immunoglobulin among the tested eels. Therefore, the generally lower ELISA values of mucosal anti-P. anguillarum antibodies from the infected eels tested were evidently not caused by a lack of immunoglobulin per se, but seem to be the result of a lack of anti-P. anguillarum antibodies in the mucus and/or a lower affinity in the anti-P. anguillarum antibodies that were present.  相似文献   
163.
164.
165.
Five sesquiterpene-related metabolites (1–5), including two new eremophilane-type compounds, philippinlins C and D (1 and 2) and a 4,5-seconeolemnane philippinlin E (3), were isolated from the organic extract of a Taiwanese soft coral Lemnalia philippinensis. The structures of the new metabolites were determined on the basis of extensive spectroscopic analysis and by comparison of NMR data with those of related metabolites. Compound 3 was suggested to be derived from the neolemnane skeleton.  相似文献   
166.
Cytokine signaling is thought to require assembly of multicomponent signaling complexes at cytoplasmic segments of membrane-embedded receptors, in which receptor-proximal protein kinases are activated. Indeed, CD40, a tumor necrosis factor receptor (TNFR) family member, forms a complex containing adaptor molecules TRAF2 and TRAF3, ubiquitin-conjugating enzyme Ubc13, cellular inhibitor of apoptosis proteins 1 and 2 (c-IAP1/2), IkappaB kinase regulatory subunit IKKgamma (also called NEMO), and mitogen-activated protein kinase (MAPK) kinase kinase MEKK1 upon ligation. TRAF2, Ubc13, and IKKgamma were required for complex assembly and activation of MEKK1 and MAPK cascades. However, these kinases were not activated unless the multicomponent signaling complex translocated from CD40 to the cytosol upon c-IAP1/2-induced degradation of TRAF3. This two-stage signaling mechanism may apply to other innate immune receptors, accounting for spatial and temporal separation of MAPK and IKK signaling.  相似文献   
167.
Histidine kinases, used for environmental sensing by bacterial two-component systems, are involved in regulation of bacterial gene expression, chemotaxis, phototaxis, and virulence. Flavin-containing domains function as light-sensory modules in plant and algal phototropins and in fungal blue-light receptors. We have discovered that the prokaryotes Brucella melitensis, Brucella abortus, Erythrobacter litoralis, and Pseudomonas syringae contain light-activated histidine kinases that bind a flavin chromophore and undergo photochemistry indicative of cysteinyl-flavin adduct formation. Infection of macrophages by B. abortus was stimulated by light in the wild type but was limited in photochemically inactive and null mutants, indicating that the flavin-containing histidine kinase functions as a photoreceptor regulating B. abortus virulence.  相似文献   
168.
Prediction of a crystallization pathway for Z-DNA hexanucleotides   总被引:3,自引:0,他引:3  
Crystallization of macromolecules for structural studies has long been a hit-or-miss process. The crystallization of hexanucleotides as Z-DNA was studied, and it was shown that the cation concentration for crystal formation could be predicted from solvation free energy (SFE) calculations. Solution studies on the conformation and solubilities of the hexanucleotides showed that a critical concentration of the DNA in the Z-conformation must be present in solution to effect crystallization. The SFE calculations therefore predict the propensity of the hexanucleotides to adopt the left-handed conformation and the driving force required to reach this critical concentration relative to the intrinsic solubility of Z-DNA for crystallization.  相似文献   
169.
170.
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