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   154篇
  免费   3篇
  国内免费   1篇
丛书文集   1篇
理论与方法论   5篇
现状及发展   37篇
研究方法   27篇
综合类   85篇
自然研究   3篇
  2023年   1篇
  2020年   1篇
  2018年   3篇
  2017年   1篇
  2014年   5篇
  2013年   7篇
  2012年   8篇
  2011年   16篇
  2010年   3篇
  2009年   3篇
  2008年   15篇
  2007年   15篇
  2006年   21篇
  2005年   13篇
  2004年   8篇
  2003年   7篇
  2002年   9篇
  2001年   1篇
  1996年   1篇
  1995年   2篇
  1992年   1篇
  1991年   1篇
  1987年   1篇
  1986年   1篇
  1982年   2篇
  1979年   2篇
  1968年   2篇
  1965年   1篇
  1961年   1篇
  1946年   5篇
  1945年   1篇
排序方式: 共有158条查询结果,搜索用时 203 毫秒
121.
In this study, we proposed and evaluated the use of Independent Component Analysis (ICA) combining the EEG dipole model to automatically remove eye movement artifacts from the EEG without needing EOG as a reference. We separated the EEG data into independent components using the ICA method, and determined the source localization of these independent components with a single dipole model. The EEG signal was reconstructed by automatically excluding those components localized within a preset eye model. EEGs from 12 patients were analyzed. The experimental results indicate that ICA with the dipole model is very efficient at automatically subtracting the eye movement artifacts, while retaining the EEG slow waves and making their interpretation easier.  相似文献   
122.
This paper proposes a mixed‐frequency error correction model for possibly cointegrated non‐stationary time series sampled at different frequencies. We highlight the impact, in terms of model specification, of the choice of the particular high‐frequency explanatory variable to be included in the cointegrating relationship, which we call a dynamic mixed‐frequency cointegrating relationship. The forecasting performance of aggregated models and several mixed‐frequency regressions are compared in a set of Monte Carlo experiments. In particular, we look at both the unrestricted mixed‐frequency model and at a more parsimonious MIDAS regression. Whereas the existing literature has only investigated the potential improvements of the MIDAS framework for stationary time series, our study emphasizes the need to include the relevant cointegrating vectors in the non‐stationary case. Furthermore, it is illustrated that the choice of dynamic mixed‐frequency cointegrating relationship does not matter as long as the short‐run dynamics are adapted accordingly. Finally, the unrestricted model is shown to suffer from parameter proliferation for samples of relatively small size, whereas MIDAS forecasts are robust to over‐parameterization. We illustrate our results for the US inflation rate. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   
123.
Multiple self-healing squamous epithelioma (MSSE), also known as Ferguson-Smith disease (FSD), is an autosomal-dominant skin cancer condition characterized by multiple squamous-carcinoma-like locally invasive skin tumors that grow rapidly for a few weeks before spontaneously regressing, leaving scars. High-throughput genomic sequencing of a conservative estimate (24.2 Mb) of the disease locus on chromosome 9 using exon array capture identified independent mutations in TGFBR1 in three unrelated families. Subsequent dideoxy sequencing of TGFBR1 identified 11 distinct monoallelic mutations in 18 affected families, firmly establishing TGFBR1 as the causative gene. The nature of the sequence variants, which include mutations in the extracellular ligand-binding domain and a series of truncating mutations in the kinase domain, indicates a clear genotype-phenotype correlation between loss-of-function TGFBR1 mutations and MSSE. This distinguishes MSSE from the Marfan syndrome-related disorders in which missense mutations in TGFBR1 lead to developmental defects with vascular involvement but no reported predisposition to cancer.  相似文献   
124.
Bardet-Biedl syndrome (BBS) is a genetically heterogeneous ciliopathy. Although nine BBS genes have been cloned, they explain only 40-50% of the total mutational load. Here we report a major new BBS locus, BBS10, that encodes a previously unknown, rapidly evolving vertebrate-specific chaperonin-like protein. We found BBS10 to be mutated in about 20% of an unselected cohort of families of various ethnic origins, including some families with mutations in other BBS genes, consistent with oligogenic inheritance. In zebrafish, mild suppression of bbs10 exacerbated the phenotypes of other bbs morphants.  相似文献   
125.
126.
This paper extends the ‘remarkable property’ of Breusch (Journal of Econometrics 1987; 36 : 383–389) and Baltagi and Li (Journal of Econometrics 1992; 53 : 45–51) to the three‐way random components framework. Indeed, like its one‐way and two‐way counterparts, the three‐way random effects model maximum likelihood estimation can be obtained as an iterated generalized least squares procedure through an appropriate algorithm of monotonic sequences of some variance components ratios, θi (i = 2, 3, 4). More specifically, a search over θiwhile iterating on the regression coefficients estimates β and the other θjwill guard against the possibility of multiple local maxima of the likelihood function. In addition, the derivations of related prediction functions are obtained based on complete as well as incomplete panels. Finally, an application to international trade issues modeling is presented. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   
127.
Long-billed curlew populations were studied in the upper Green River Basin of Wyoming. Sites were selected where curlew populations appear constant in numbers and declining in numbers. Results show that while few habitat differences were found between the two areas, disturbances such as grazing and dragging during nesting reduced productivity. Nest failures were also correlated with field fertilization and early season grazing. Within each area curlews nested successfully on field sites that were elevated and had adequate grass cover but not tall grass.  相似文献   
128.
Summary Experiments were carried out to test the effects of relative humidity on prepupae and pupae of the Silkworm,Bombyx mori L., at 250 C. It was found that:(1) duration of prepupal + pupal stages is the same at all relative humidities between 7 and 100%;(2) mortality seems unaffected in all these humidity conditions;(3) moths obtained in percentages between 55 and 100% R. H. have the same average wet weight; moths obtained under dryer conditions have a lower average weight (expressed in percentage of initial weights of prepupae);(4) pupae extracted from their cocoons develop as quickly and as well as pupae in their cocoons.  相似文献   
129.
Eumeces capito Boucourt, 1879, is a senior synonym of Eumeces xanthi Günther, 1889. No exception to application of the Law of Priority is recommended in this case. The type locality of E. capito as originally published (“La côte oriental des Etats - Unis”) is erroneous. Undoubtedly the correct locality is China, but it is not restricted at present.      相似文献   
130.
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