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   9118篇
  免费   126篇
  国内免费   14篇
电工技术   116篇
综合类   4篇
化学工业   981篇
金属工艺   97篇
机械仪表   144篇
建筑科学   263篇
矿业工程   16篇
能源动力   122篇
轻工业   488篇
水利工程   56篇
石油天然气   7篇
武器工业   1篇
无线电   696篇
一般工业技术   957篇
冶金工业   4564篇
原子能技术   70篇
自动化技术   676篇
  2022年   37篇
  2021年   43篇
  2019年   40篇
  2018年   77篇
  2017年   55篇
  2016年   67篇
  2015年   72篇
  2014年   97篇
  2013年   258篇
  2012年   159篇
  2011年   195篇
  2010年   143篇
  2009年   158篇
  2008年   199篇
  2007年   201篇
  2006年   199篇
  2005年   194篇
  2004年   175篇
  2003年   156篇
  2002年   146篇
  2001年   145篇
  2000年   151篇
  1999年   223篇
  1998年   1280篇
  1997年   702篇
  1996年   543篇
  1995年   317篇
  1994年   296篇
  1993年   312篇
  1992年   148篇
  1991年   134篇
  1990年   120篇
  1989年   141篇
  1988年   131篇
  1987年   131篇
  1986年   125篇
  1985年   137篇
  1984年   105篇
  1983年   81篇
  1982年   100篇
  1981年   98篇
  1980年   90篇
  1979年   71篇
  1978年   74篇
  1977年   156篇
  1976年   270篇
  1975年   43篇
  1974年   44篇
  1973年   52篇
  1972年   43篇
排序方式: 共有9258条查询结果,搜索用时 0 毫秒
61.
Studied visual masking and visual integration across saccadic eye movements in 4 experiments. In a 5th experiment, 4 randomly chosen dots from a 3?×?5 dot matrix were presented in 1 fixation, and 4 different dots from the matrix were presented in a 2nd fixation. Ss reported the location of the missing dot. When the 1st display was presented just before the saccade (as in Exps I–III), Ss accurately specified the missing dot location when the dots were presented to the same region of the retina but not when they were presented in the same place in space. When the 1st display was presented well before the saccade (as in Exp IV), Ss performed poorly regardless of retinal or spatial overlap. Results indicate the existence of a short-lived retinotopic visual persistence but provide no support for a spatiotopic visual persistence capable of fusing the contents of successive fixations. It is concluded that transsaccadic integration depends instead on an abstract memory that accumulates position and identity information about the contents of successive fixations. Results are discussed in relation to the work by M. L. Davidson et al (see record 1974-10245-001). (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
62.
We employed an anatomically realistic three-dimensional finite-element model to explore several biomechanical variables involved in coring or bone-grafting of a segmentally necrotic femoral head. The mechanical efficacy of several variants of these procedures was indexed in terms of their alteration of the stress:strength ratio in at-risk necrotic cancellous bone. For coring alone, the associated structural compromise was generally modest, provided that the tract did not extend near the subchondral plate. Cortical bone-grafting was potentially of great structural benefit for femoral heads in which the graft penetrated deeply into the superocentral or lateral aspect of the lesion, ideally with abutment against the subchondral plate. By contrast, central or lateral grafts that stopped well short of the subchondral plate were contraindicated biomechanically because they caused marked elevations in stress on the necrotic cancellous bone. Calculated levels of stress were relatively insensitive to variations in the diameter of the graft.  相似文献   
63.
64.
Mothers (N?=?76) of 3- to 5-year-old children completed questionnaires assessing beliefs in the importance and modifiability (vs. innateness) of children's peer relationship skills, perceptions of their children's social competence with peers, and strategies they would use in response to children's peer interaction problems. A subsample of mothers (n?=?34) was observed supervising the play of their own children and a peer. Maternal perceptions of children's competence were negatively associated with the extent of mothers' involvement in children's play, whereas the quality of supervision was predicted by knowledge of socialization strategies and the interaction of beliefs and knowledge. Beliefs appeared to moderate the effects of maternal knowledge on mothers' behavior in that knowledge was associated with the quality of supervision only when mothers believed social skills were important and modifiable. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
65.
66.
With the recent advent of accurate orbital volume assessment by computed tomography, a retrospective analysis was made of 31 patients with 'pure' blowout fracture of the orbital floor, managed either surgically or conservatively, to determine whether orbital volume measurement could provide an additional parameter of use in the management of such fractures. There was a significant difference in orbital volume discrepancy between patients managed surgically or conservatively suggesting that this investigation may be of use in decision making on surgical intervention in patients with orbital blowout fractures.  相似文献   
67.
Bovine spongiform encephalopathy (BSE), or ‘mad cow disease’, is one of several transmissable spongiform encephalopathies (TSEs) known to affect certain mammals and is spread through the ingestion of infected animal tissue. It is believed that the inadvertent contamination of meat and bone meal (MBM) with infected animal tissue and the subsequent use of this material as a feed supplement contributed to the spread of the disease in cattle. As a result, the use of processed animal proteins (PAPs) in animal feeds is regulated in many parts of the world. Although feed testing is the only definitive means to certify compliance, regulatory compliance often relies solely on paper certification. Recently, rapid methods have become available that can be used by regulators to determine compliance during routine inspections. We describe a rapid, immunochromatographic strip test that can detect 0.1% MBM in animal feed. The test takes 15 min to perform and large numbers of samples can be screened for PAPs simultaneously.  相似文献   
68.
The modality effect in immediate recall refers to superior recall of the last few items within lists presented in spoken as opposed to printed form. The locus of this well-known effect has been unclear. N. Cowan, J. S. Saults, E. M. Elliott, and M. Moreno (2002) introduced a new method to distinguish between the effects of input serial position, output serial position, and the number of items yet to be recalled and found that large modality effects occurred only in conditions in which delay and interference at output (from items already recalled) was high. The authors replicated that finding, even when the response period included output interference acoustically similar to the spoken stimuli to be recalled. However, the authors found that output delay and interference act only by lowering the level of performance to a more sensitive range. The modality effect thus originates during encoding of the list to be recalled, not during output. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
69.
We describe the results of functional studies on DNA clones encoding functional bradykinin receptors derived from human, rat, and mouse sources and including both genomic and complementary DNA clones. In both the Xenopus oocyte and the COS cell expression systems, the receptors from human and rat showed the pharmacological properties of B2 receptors, but receptors from mouse displayed both B1- and B2-like pharmacological properties. We further investigated the molecular relationship between the B1 and B2 receptor subtypes expressed by a human fibroblast cell line, and we demonstrate that these two receptor subtypes are encoded by distinct mRNA species.  相似文献   
70.
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