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   80篇
  免费   0篇
系统科学   6篇
理论与方法论   1篇
现状及发展   17篇
研究方法   9篇
综合类   45篇
自然研究   2篇
  2020年   1篇
  2015年   1篇
  2014年   1篇
  2013年   2篇
  2012年   2篇
  2011年   2篇
  2010年   1篇
  2009年   1篇
  2008年   2篇
  2007年   8篇
  2006年   3篇
  2005年   1篇
  2004年   8篇
  2003年   5篇
  2002年   1篇
  2001年   5篇
  2000年   4篇
  1999年   3篇
  1997年   1篇
  1995年   1篇
  1993年   1篇
  1992年   1篇
  1990年   2篇
  1988年   1篇
  1987年   2篇
  1982年   1篇
  1980年   1篇
  1978年   3篇
  1977年   1篇
  1976年   1篇
  1974年   3篇
  1972年   3篇
  1969年   1篇
  1968年   3篇
  1966年   1篇
  1965年   2篇
排序方式: 共有80条查询结果,搜索用时 15 毫秒
61.
Zusammenfassung Nachweis, dass die Aminosäure-Zusammensetzung der Hämolymphe vonSimuliumvenustum-Larven total 39.3±1.3 mg Amino N pro 100 ml enthält, wobei als hauptsächliche Ninhydrinpositive Bestandteile der Hämolymphe Alanin, Asparagin, Asparaginsäure, Dioxyphenylalanin, Äthanolanin, Glutaminsäure, Glutamin, Glycin, Histidin, Phenylalanin und Serin gefunden wurden, während nur kleine Mengen von Tyrosin, Halb-Cystin und Cystathion festgestellt wurden.  相似文献   
62.
Multilayers of phospholipid bimolecular leaflets   总被引:8,自引:0,他引:8  
Y K Levine  A I Bailey  M H Wilkins 《Nature》1968,220(5167):577-578
  相似文献   
63.
This is the second of two articles describing the revision of The ONS classification of local and health authorities of Great Britain to take account of area changes in the 1990's. It presents local authorities in Great Britain as at April 1999 in terms of Families, Groups and Clusters, based on 37 socio-economic and demographic variables from the 1991 Census. Health authorities are presented in terms of Families and Groups only, based on the same variables. The previous article (in Population Trends 98) presented, for each local and health authority, up to four other authorities to which it is 'most similar'.  相似文献   
64.
The domestication of cattle, sheep and goats had already taken place in the Near East by the eighth millennium bc. Although there would have been considerable economic and nutritional gains from using these animals for their milk and other products from living animals-that is, traction and wool-the first clear evidence for these appears much later, from the late fifth and fourth millennia bc. Hence, the timing and region in which milking was first practised remain unknown. Organic residues preserved in archaeological pottery have provided direct evidence for the use of milk in the fourth millennium in Britain, and in the sixth millennium in eastern Europe, based on the delta(13)C values of the major fatty acids of milk fat. Here we apply this approach to more than 2,200 pottery vessels from sites in the Near East and southeastern Europe dating from the fifth to the seventh millennia bc. We show that milk was in use by the seventh millennium; this is the earliest direct evidence to date. Milking was particularly important in northwestern Anatolia, pointing to regional differences linked with conditions more favourable to cattle compared to other regions, where sheep and goats were relatively common and milk use less important. The latter is supported by correlations between the fat type and animal bone evidence.  相似文献   
65.
One exotic poeciliid ( Xiphophorus helleri ) and two cichlids ( Cichlasoma nigrofasciatum and Tilapia mossambica ) are recorded as recently established in thermal springs and their outflows in southern Idaho. Misgurnus anguillicaudatus was collected and is considered as established in the Boise River system. Poecilia mexicana and juvenile hybrid tilapias are recorded from the Bruneau River at Bruneau Hot Springs, Idaho. A reproducing population of X. helleri was found in a spring within the boundaries of Grand Teton National Park, Wyoming. Poecilia reticulata , previously reported from one spring each in Idaho and Wyoming, is recorded from a second spring outflow in Idaho.  相似文献   
66.
DNA double-strand breaks are not sufficient to initiate recruitment of TRF2   总被引:1,自引:0,他引:1  
  相似文献   
67.
We conducted a genome-wide association study of 299,983 tagging SNPs for chronic lymphocytic leukemia (CLL) and performed validation in two additional series totaling 1,529 cases and 3,115 controls. We identified six previously unreported CLL risk loci at 2q13 (rs17483466; P = 2.36 x 10(-10)), 2q37.1 (rs13397985, SP140; P = 5.40 x 10(-10)), 6p25.3 (rs872071, IRF4; P = 1.91 x 10(-20)), 11q24.1 (rs735665; P = 3.78 x 10(-12)), 15q23 (rs7176508; P = 4.54 x 10(-12)) and 19q13.32 (rs11083846, PRKD2; P = 3.96 x 10(-9)). These data provide the first evidence for the existence of common, low-penetrance susceptibility to a hematological malignancy and new insights into disease causation in CLL.  相似文献   
68.
Genome-wide association studies are now identifying disease-associated chromosome regions. However, even after convincing replication, the localization of the causal variant(s) requires comprehensive resequencing, extensive genotyping and statistical analyses in large sample sets leading to targeted functional studies. Here, we have localized the type 1 diabetes (T1D) association in the interleukin 2 receptor alpha (IL2RA) gene region to two independent groups of SNPs, spanning overlapping regions of 14 and 40 kb, encompassing IL2RA intron 1 and the 5' regions of IL2RA and RBM17 (odds ratio = 2.04, 95% confidence interval = 1.70-2.45; P = 1.92 x 10(-28); control frequency = 0.635). Furthermore, we have associated IL2RA T1D susceptibility genotypes with lower circulating levels of the biomarker, soluble IL-2RA (P = 6.28 x 10(-28)), suggesting that an inherited lower immune responsiveness predisposes to T1D.  相似文献   
69.
This study investigates whether human judgement can be of value to users of industrial learning curves, either alone or in conjunction with statistical models. In a laboratory setting, it compares the forecast accuracy of a statistical model and judgemental forecasts, contingent on three factors: the amount of data available prior to forecasting, the forecasting horizon, and the availability of a decision aid (projections from a fitted learning curve). The results indicate that human judgement was better than the curve forecasts overall. Despite their lack of field experience with learning curve use, 52 of the 79 subjects outperformed the curve on the set of 120 forecasts, based on mean absolute percentage error. Human performance was statistically superior to the model when few data points were available and when forecasting further into the future. These results indicate substantial potential for human judgement to improve predictive accuracy in the industrial learning‐curve context. Copyright © 1999 John Wiley & Sons, Ltd.  相似文献   
70.
Summary In patients exhibiting in marrow cells deletion of the long arm of chromosome 20, the specific activities of adenosine deaminase in cells of the peripheral blood are normal. This suggests that the gene for adenosine deaminase is not localized to the distal segment of the long arm of this chromosome.This work was supported by Grants from the National Health and Medical Research Council of Australia and the Anti-Cancer Council of Victoria.  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