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   9898篇
  免费   187篇
  国内免费   9篇
电工技术   105篇
综合类   6篇
化学工业   1449篇
金属工艺   113篇
机械仪表   322篇
建筑科学   268篇
矿业工程   28篇
能源动力   146篇
轻工业   1033篇
水利工程   118篇
石油天然气   16篇
无线电   924篇
一般工业技术   1222篇
冶金工业   3353篇
原子能技术   108篇
自动化技术   883篇
  2022年   100篇
  2021年   161篇
  2020年   94篇
  2019年   105篇
  2018年   95篇
  2017年   123篇
  2016年   101篇
  2015年   97篇
  2014年   142篇
  2013年   385篇
  2012年   238篇
  2011年   335篇
  2010年   284篇
  2009年   298篇
  2008年   342篇
  2007年   308篇
  2006年   300篇
  2005年   252篇
  2004年   217篇
  2003年   231篇
  2002年   226篇
  2001年   185篇
  2000年   176篇
  1999年   209篇
  1998年   778篇
  1997年   492篇
  1996年   428篇
  1995年   303篇
  1994年   253篇
  1993年   258篇
  1992年   114篇
  1991年   131篇
  1990年   138篇
  1989年   137篇
  1988年   142篇
  1987年   138篇
  1986年   109篇
  1985年   133篇
  1984年   95篇
  1983年   103篇
  1982年   71篇
  1981年   90篇
  1980年   70篇
  1979年   80篇
  1978年   70篇
  1977年   110篇
  1976年   201篇
  1975年   74篇
  1974年   71篇
  1973年   64篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
Comments that L. B. Silverstein's (see record 1992-05293-001) article on child care and maternal employment contributes unfounded and damaging misbeliefs regarding fathers. The dad-as-cad myth suggests intentional malevolence or at least blatant failure by fathers to care for others, and suggests that their failure to share equally in child care and household management is the primary cause of marital conflict. W. B. Johnson and D. Hayes propose a research agenda for fathering that originates in a coherent model of male development in the context of ever-changing environmental demands. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
42.
43.
44.
Neuropathological examinations were carried out at necropsy on 274 cases of intrauterine death or neonatal death at or before three days after birth. Fifty six (20.4%) subjects had evidence of prenatal ischaemic brain damage. On review of the maternal case notes to ascertain antenatal clinical associations there was an increased incidence of intrauterine growth retardation, either based on birth weight for gestational age (odds ratio (OR) 2.0; 95% confidence interval (CI) 1.1 to 3.7) or diagnosed antenatally (OR 2.7; 95% CI 1.3 to 5.6). Oligohydramnios was also more common (OR 2.9; 95% CI 1.2 to 7.0). The association of intrauterine growth retardation and white matter damage remained after excluding fetuses with a major congenital anomaly (OR 2.4; 95% CI 1.1 to 5.1). The findings suggest that chronic intrauterine hypoxia may be associated with damage to cerebral white matter among fetuses and infants who die. The relation between ischaemic white matter damage and cerebral palsy among survivors remains speculative.  相似文献   
45.
Infants seem sensitive to hidden objects in habituation tasks at 3.5 months but fail to retrieve hidden objects until 8 months. The authors first consider principle-based accounts of these successes and failures, in which early successes imply knowledge of principles and failures are attributed to ancillary deficits. One account is that infants younger than 8 months have the object permanence principle but lack means-ends abilities. To test this, 7-month-olds were trained on means-ends behaviors and were tested on retrieval of visible and occluded toys. Means-ends demands were the same, yet infants made more toy-guided retrievals in the visible case. The authors offer an adaptive process account in which knowledge is graded and embedded in specific behavioral processes. Simulation models that learn gradually to represent occluded objects show how this approach can account for success and failure in object permanence tasks without assuming principles and ancillary deficits.  相似文献   
46.
Human peripheral blood monocytes were examined for migration across an endothelial cell monolayer in an in vitro vessel wall construct. Few monocytes invaded in the absence of a chemotactic gradient, despite significant adhesion to the endothelial monolayer. However, the addition of zymosan-activated human plasma to the lower compartment, to create a chemotactic gradient across the vessel wall, resulted in significantly enhanced monocyte migration. Pretreatment of the monocytes with monoclonal antibodies to thrombospondin (TSP) dramatically inhibited monocyte diapedesis into the vessel wall. The same treatment inhibited monocyte adhesion to endothelial cells in two-dimensional monolayer cultures as well as in vessel wall constructs (no chemotactic gradient). Of interest, however, the monoclonal antibodies had no inhibitory effect on monocyte migration into collagen gels devoid of endothelial cells in response to the same chemotactic gradient, suggesting the importance of TSP in monocyte-endothelial cell interactions. Monoclonal antibodies to fibronectin and normal mouse immunoglobulin G did not inhibit migration in this model of a vessel wall. Furthermore, monoclonal antibodies to TSP showed no inhibition of human peripheral blood neutrophil migration. Previous studies have shown that monocytes synthesize TSP and express this moiety on their surface. The present data suggest that monocytes may utilize TSP to interact with endothelial cells lining the vessel wall during diapedesis.  相似文献   
47.
This study investigates self-presentation strategies among online dating participants, exploring how participants manage their online presentation of self in order to accomplish the goal of finding a romantic partner. Thirty-four individuals active on a large online dating site participated in telephone interviews about their online dating experiences and perceptions. Qualitative data analysis suggests that participants attended to small cues online, mediated the tension between impression management pressures and the desire to present an authentic sense of self through tactics such as creating a profile that reflected their "ideal self," and attempted to establish the veracity of their identity claims. This study provides empirical support for Social Information Processing theory in a naturalistic context while offering insight into the complicated way in which "honesty" is enacted online.  相似文献   
48.
49.
50.
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