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   106篇
  免费   2篇
系统科学   5篇
理论与方法论   3篇
现状及发展   43篇
研究方法   10篇
综合类   41篇
自然研究   6篇
  2021年   1篇
  2020年   3篇
  2018年   2篇
  2017年   1篇
  2016年   5篇
  2015年   4篇
  2014年   4篇
  2013年   4篇
  2012年   8篇
  2011年   9篇
  2010年   3篇
  2009年   1篇
  2008年   4篇
  2007年   10篇
  2006年   4篇
  2005年   2篇
  2004年   4篇
  2003年   5篇
  2002年   2篇
  2000年   2篇
  1999年   1篇
  1992年   2篇
  1991年   1篇
  1987年   1篇
  1985年   1篇
  1984年   2篇
  1982年   3篇
  1981年   4篇
  1980年   1篇
  1977年   1篇
  1976年   1篇
  1975年   3篇
  1974年   2篇
  1970年   3篇
  1969年   1篇
  1968年   1篇
  1966年   2篇
排序方式: 共有108条查询结果,搜索用时 0 毫秒
31.
The objective of this paper is to develop a GME formulation for the class of spatial structural equations models (S-SEM). In this respect, two innovatory aspects are introduced: (i) the formalization of the GME estimation approach for structural equations models that account for spatial heterogeneity and spatial dependence; (ii) the extension of the methodology to a panel data framework. We also present an application of the method to real data finalized to investigate disparities of unemployment rates in OECD countries over the period 1998-2006.  相似文献   
32.
Trechona diamantina sp. nov. is described from quartzite caves in Diamantina, central Minas Gerais State, Brazil. This represents the largest cavernicolous mygalomorph population ever recorded. The new species is the first Trechona recorded from a xeric habitat, namely the Rocky Fields on the Diamantina Plateau. T. diamantina sp. nov. is closely related to T. uniformis, both species possessing elongated male and female copulatory organs and both constructing distinct funnel-webs and sheet-webs in quartzite formations. T. diamantina sp. nov. is distinct in possessing less elongated embolus and receptacula seminis. A key for all valid species of the genus is given.

http://zoobank.org/urn:lsid:zoobank.org:pub:EB9E66B3-4701-470C-A80D-873E25F52042  相似文献   

33.
34.
Progressive supranuclear palsy (PSP) is a movement disorder with prominent tau neuropathology. Brain diseases with abnormal tau deposits are called tauopathies, the most common of which is Alzheimer's disease. Environmental causes of tauopathies include repetitive head trauma associated with some sports. To identify common genetic variation contributing to risk for tauopathies, we carried out a genome-wide association study of 1,114 individuals with PSP (cases) and 3,247 controls (stage 1) followed by a second stage in which we genotyped 1,051 cases and 3,560 controls for the stage 1 SNPs that yielded P ≤ 10(-3). We found significant previously unidentified signals (P < 5 × 10(-8)) associated with PSP risk at STX6, EIF2AK3 and MOBP. We confirmed two independent variants in MAPT affecting risk for PSP, one of which influences MAPT brain expression. The genes implicated encode proteins for vesicle-membrane fusion at the Golgi-endosomal interface, for the endoplasmic reticulum unfolded protein response and for a myelin structural component.  相似文献   
35.
Vertebral and metaphyseal dysplasia, spasticity with cerebral calcifications, and strong predisposition to autoimmune diseases are the hallmarks of the genetic disorder spondyloenchondrodysplasia. We mapped a locus in five consanguineous families to chromosome 19p13 and identified mutations in ACP5, which encodes tartrate-resistant phosphatase (TRAP), in 14 affected individuals and showed that these mutations abolish enzyme function in the serum and cells of affected individuals. Phosphorylated osteopontin, a protein involved in bone reabsorption and in immune regulation, accumulates in serum, urine and cells cultured from TRAP-deficient individuals. Case-derived dendritic cells exhibit an altered cytokine profile and are more potent than matched control cells in stimulating allogeneic T cell proliferation in mixed lymphocyte reactions. These findings shed new light on the role of osteopontin and its regulation by TRAP in the pathogenesis of common autoimmune disorders.  相似文献   
36.
37.
Di Rosa I  Simoncelli F  Fagotti A  Pascolini R 《Nature》2007,447(7144):E4-5; discussion E5-6
Pounds et al. argue that global warming contributes to amphibian declines by encouraging outbreaks of the chytrid fungus Batrachochytrium dendrobatidis. Although our findings agree with the climate-linked epidemic hypothesis, this pathogen is probably not the only proximate factor in such cases: in the Trasimeno Lake area of Umbria in central Italy, for example, the water frog Rana lessonae first declined in the late 1990s, yet chytridiomycosis was not observed until 2003 (refs 5, 6). Here we show that the chytrid was common there throughout 1999-2002, in a previously unknown form that did not cause disease. We therefore think that the focus by Pounds et al. on a single pathogen is hard to justify because the host-parasite ecology is at present so poorly understood.  相似文献   
38.
39.
This article presents a proposal of a systemic model composed for the micro and small companies (MSE) of the region of Ribeirão Preto and the agents which influenced their environment. The proposed model was based on Stafford Beer’s (Diagnosing the system for organizations. Chichester, Wiley, 1985) systemic methodologies VSM (Viable System Model) and on Werner Ulrich’s (1983) CSH (Critical Systems Heuristics). The VSM is a model for the diagnosis of the structure of an organization and of its flows of information through the application of the cybernetics concepts (Narvarte, In El Modelo del Sistema Viable—MSV: experiencias de su aplicación en Chile. Proyecto Cerebro Colectivo del IAS, Santiago, 2001). On the other hand, CSH focus on the context of the social group applied to the systemic vision as a counterpoint to the organizational management view considered by the VSM. MSE of Ribeirão Preto and Sertãozinho had been analyzed as organizations inserted in systems that relate and integrate with other systems concerning the public administration, entities of representation and promotion agencies. The research questions: which are the bonds of interaction among the subsystems in this process and who are the agents involved? The systemic approach not only diagnosed a social group, formed by MSE of Ribeirão Preto and Sertãozinho, public authorities and support entities, but could also delineate answers that aimed the clarification of obscure questions generating financial assistance to the formularization of efficient actions for the development of this system.  相似文献   
40.
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