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   144篇
  免费   7篇
  2021年   5篇
  2018年   3篇
  2016年   4篇
  2015年   7篇
  2013年   8篇
  2012年   6篇
  2011年   2篇
  2010年   5篇
  2008年   1篇
  2007年   6篇
  2006年   3篇
  2005年   7篇
  2004年   5篇
  2003年   4篇
  2002年   1篇
  2001年   4篇
  2000年   4篇
  1999年   3篇
  1998年   2篇
  1997年   1篇
  1996年   1篇
  1995年   1篇
  1994年   1篇
  1993年   4篇
  1992年   3篇
  1991年   2篇
  1989年   4篇
  1988年   1篇
  1987年   3篇
  1986年   2篇
  1985年   2篇
  1984年   4篇
  1983年   5篇
  1982年   8篇
  1981年   2篇
  1979年   1篇
  1977年   1篇
  1976年   1篇
  1975年   1篇
  1973年   1篇
  1972年   3篇
  1971年   2篇
  1970年   3篇
  1969年   3篇
  1965年   1篇
  1964年   2篇
  1963年   3篇
  1961年   1篇
  1954年   1篇
  1916年   1篇
排序方式: 共有151条查询结果,搜索用时 46 毫秒
31.
Crimean-Congo hemorrhagic fever (CCHF) virus is one among the major zoonosis viral diseases that use the Hyalomma ticks as their transmission vector to cause viral infection to the human and mammalian community. The fatality of infectious is high across the world especially in Africa, Asia, Middle East, and Europe. This study regarding codon usage bias of S, M, and L segments of the CCHF virus pertaining to the host Homo sapiens, reveals in-depth information about the evolutionary characteristics of CCHFV. Relative Synonymous Codon Usage (RSCU), Effective number of codons (ENC) were calculated, to determine the codon usage pattern in each segment. Correlation analysis between Codon adaptation index (CAI), GRAVY (Hydrophobicity), AROMO (Aromaticity), and nucleotide composition revealed bias in the codon usage pattern. There was no strong codon bias found among any segments of the CCHF virus, indicating both the factors i.e., natural selection and mutational pressure shapes the codon usage bias.  相似文献   
32.
We investigated the prevalence and phenotypic variation of Candida species in oral lichen planus (OLP) and the therapeutic implications of our findings. Eighty patients with clinically and histopathologically confirmed cases of OLP (64 non-erosive, 16 erosive) and a control group of 80 healthy individuals with no predisposing factors for oral candidiasis were examined for evidence of Candida infection. Oral swabs and smears were obtained for cytology and culture. Identification, speciation and antifungal susceptibility tests of Candida isolates were performed using an automated microbial identification system. Fifty percent of erosive OLP cases, 28% of non-erosive cases and none of the controls showed evidence of Candida. Candida albicans was found predominantly in non-erosive OLP, while other Candida species were predominate in erosive OLP. Non-Candida albicans isolates (C. glabrata, C. krusei) were resistant to the commonly used antifungals, clotrimazole and fluconazole. Candida infection is common in cases of OLP. We recommend antifungal sensitivity testing prior to antifungal therapy for the erosive form of OLP.  相似文献   
33.
Summary The infection of root hairs and nodulation ofT. subterraneum L. cv. Cranmore byRhizobium trifolii strain TA1 was extremely sensitive to root temperature. Within the range 11°–19°C infection was progressively delayed as root temperature decreased but at 7°C no root hairs were infected by 40 days. At 7°C lateral root formation was stimulated in the root zone where nodules formed at 19°C.  相似文献   
34.
Models of the human bronchial tree   总被引:18,自引:0,他引:18  
  相似文献   
35.
Summary The seasonal patterns of nodulation, acetylene reduction, nitrogen uptake and nitrogen fixation were studies for 11 pigeonpea cultivars belonging to different maturity groups grown on an Alfisol at ICRISAT Center, Patancheru, India. In all cultivars the nodule number and mass increased to a maximum around 60–80 days after sowing and then declined. The nodule number and mass of medium- and late-maturing cultivars was greater than that of early-maturing cultivars. The nitrogenase activity per plant increased to 60 days after sowing and declined thereafter, with little activity at 100 days when the crop was flowering. At later stages of plant growth nodules formed down to 90 cm below the soil surface but those at greater depth appeared less active than those near the surface. All the 11 cultivars continued to accumulate dry matter until 140 days, with most biomass production by the late-maturing cultivars (up to 11 t ha−1) and least by the early-maturing determinate cultivars (4 t ha−1). Total nitrogen uptake ranged from 69 to 134 kg ha−1. Nitrogen fixation by pigeonpea was estimated as the difference in total nitrogen uptake between pigeonpea and sorghum and could amount to 69 kg N ha−1 per season, or half the total nitrogen uptake. Fixation by pigeonpea increased with crop duration, but there were differences within each maturity group. The limitations of the methods used for estimating N2 fixation by pigeonpea are discussed. Submitted as J.A. No. 552 by the International Crops Research Institute for the Semi-Arid Tropics (ICRISAT).  相似文献   
36.
Nitrogen fixation associated with non-legumes in agriculture   总被引:1,自引:0,他引:1  
P. J. Dart 《Plant and Soil》1986,90(1-3):303-334
Summary This review examines the nitrogen cycle in upland agricultural situations where nonlegume N2-fixation is likely to be important for crop growth. Evidence for associative fixation is adduced from accumulation of N in the top 15 cm soil under grasses, from N balances for crop production obtained from both pot and field experiments, in tropical and temperate environments, measurements of nitrogen (C2H2 reduction) activity, uptake of15N2 by plants and15N isotope dilution. Factors influencing the activity such as the provision of carbon substrate by the plant and the efficiency of its utilisation by the bacteria, plant cultivar, soil moisture and N levels, and inoculation with N2-fixing bacteria are discussed. Crop responses to inoculation withAzospirillum are detailed. The breakdown of crop residues, particularly straw, can support large levels of N2-fixation. Cyanobacteria as crusts on the soil surface also fix nitrogen actively in many environments. Fixation by the nodulated, non-legume treesCasuarina andParasponia has beneficial effects in some cropping systems in Asia. I conclude that nonlegume N2-fixation makes a significant contribution to the production of some major cereal crops in both temperate and tropical environments.  相似文献   
37.
Seventy-three patients were studied after ingesting a liquid glucose meal, tagged with 113Indium. Nineteen of these patients were awaiting surgery for their duodenal ulcer, while 54 were studied postoperatively, 25 of whom experienced troublesome postprandial (dumping) symptoms in their daily lives. The radioactive marker emptied significantly faster in the symptomatic patients than in the symptomfree, pre and post-operative groups (initial emptying rate 3.45 ± 0.23, compared with 1.16 ± 0.19 and 1.27 ± 0.15% fall in counts/min respectively; p < 0.01). Initial (20 min) rises in the plasma concentrations of neurotensin-like immunoreactivity measured during the test correlated significantly with the rate of gastric emptying in all patients, being greatest in patients with dumping symptoms. Physiological concentrations of neurotensin have been shown to delay gastric emptying. The excessive rise in plasma neurotensin-like immunoreactivity in patients with dumping symptoms, presumably occuring as a result of the rapid passage of nutrients to the neurotensin-rich ileum, may possibly have a compensatory role in slowing further emptying from the stomach.  相似文献   
38.
Summary Roots of sugar cane had considerable nitrogenase activity and produced up to 5 n moles ethylene/h/g root by the reduction of acetylene. The rhizosphere soil and soil mid-way between the cane rows also reduced acetylene.Beijerinckia indica was abundant on roots and in the soil. Nitrogenase activity was also associated with roots ofPanicum maximum,Pennisetum purpureum andCymbopogon citratus.  相似文献   
39.
Tolerance of Australian tropical and subtropical Acacias to acid soil   总被引:1,自引:0,他引:1  
Two glasshouse experiments were conducted to refine screening procedures and to rank 36 native Acacia species for acid-soil tolerance. The first experiment showed that nitrogen fixation was more sensitive to soil acidity than plant growth per se. This suggests that, in screening experiments where acid soil tolerant rhizobia are not available, inorganic nitrogen should be supplied in determining the species' intrinsic ability to tolerate soil acidity and to avoid confounding sensitivity to acid soil with ineffectiveness of Rhizobium/Bradyrhizobium. The second experiment enabled us to rank 36 species into 4 classes of differing tolerance to acid soil. This experiment also indicated that the ranking order of species differed with the soil type, suggesting the need to use more than one soil type in screening experiments in order to obtain a better and more reliable ranking of species for tolerance to acid soil.  相似文献   
40.
Summary A vesicular intracytoplasmic membrane system is demonstrated in bacteroids from the leghaemoglobin filled zone of effective Trifolium subterraneum nodules after KMnO4 and OsO4 fixation. The system appears to be present in all mature bacteroids from this zone, and is derived from tubular invaginations of the plasma membrane of the bacteriod. A granular substance similar to the bacteroid cytoplasm is found in the vesicles which are bounded by a tripartite membrane approximately 80 Å wide, while the interspace between the vesicles is filled with a material of similar appearance to that in the interspace between bacteroid plasma membrane and cell wall.  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