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   89319篇
  免费   1192篇
  国内免费   415篇
电工技术   812篇
综合类   2320篇
化学工业   12324篇
金属工艺   4835篇
机械仪表   3102篇
建筑科学   2407篇
矿业工程   591篇
能源动力   1168篇
轻工业   4381篇
水利工程   1312篇
石油天然气   381篇
无线电   9466篇
一般工业技术   16942篇
冶金工业   4645篇
原子能技术   267篇
自动化技术   25973篇
  2022年   77篇
  2021年   93篇
  2020年   61篇
  2019年   88篇
  2018年   14528篇
  2017年   13465篇
  2016年   10040篇
  2015年   683篇
  2014年   349篇
  2013年   541篇
  2012年   3324篇
  2011年   9701篇
  2010年   8482篇
  2009年   5755篇
  2008年   7022篇
  2007年   8029篇
  2006年   350篇
  2005年   1415篇
  2004年   1306篇
  2003年   1342篇
  2002年   712篇
  2001年   201篇
  2000年   290篇
  1999年   169篇
  1998年   159篇
  1997年   146篇
  1996年   178篇
  1995年   107篇
  1994年   123篇
  1993年   138篇
  1992年   118篇
  1991年   69篇
  1990年   106篇
  1989年   104篇
  1988年   90篇
  1987年   91篇
  1986年   86篇
  1985年   94篇
  1984年   72篇
  1983年   70篇
  1982年   52篇
  1981年   54篇
  1980年   43篇
  1979年   43篇
  1977年   51篇
  1968年   50篇
  1966年   53篇
  1965年   50篇
  1955年   67篇
  1954年   69篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
61.
A series of Al-Cu-Ni alloys of various compositions were made and annealed at 800 °C. The equilibrium phases were studied by metallography, X-ray diffraction (XRD) analysis, and electron probe microanalysis. The isothermal section of the ternary Al-Cu-Ni system at 800 °C was then determined based on these experimental results and the available phase relationship knowledge of the three constituent binary systems. No ternary compound was found. All three phases, AlNi3, AlNi, and Al3Ni2, have very high ternary solubility, especially the AlNi phase, which almost reaches the binary Al-Cu side. However, no continuous solid solution was formed between the AlNi phase and any of the binary Al-Cu phases. Interfacial reactions of Al/Ni, Al/Cu, Al-Cu/Ni, and Al-Ni/Cu at 800 °C were investigated by using reaction couple techniques. The results showed that Al3Ni and Al3Ni2 phases were formed in the Al/Ni couples; β-AlCu4, γ 1-Al4Cu9, and ɛ 2-Al2Cu3 phases were formed in the Al/Cu couples. As for the results in the Al-2 at. pct Ni/Cu, Al-5 at. pct Ni/Cu, and Al-2 at. pct Cu/Ni, Al-4.5 at. pct Cu/Ni, and Al-6 at. pct Cu/Ni were similar to those in the binary Al/Cu and Al/Ni couples, respectively. A different reaction path was found in the Al-7.5 at. pct Cu/Ni couples, and an AlNi solid solution layer was formed instead of the Al3Ni and Al3Ni2 phases.  相似文献   
62.
63.
The hot blow forming of magnesium sheet offers significant opportunity for forming complex, lightweight parts for automotive applications. This paper characterizes the elevated-temperature formability of AZ31 magnesium sheet materials and the effect of processing conditions on the performance of these materials. In addition, magnesium sheet application development at General Motors Corporation is reviewed.  相似文献   
64.
Strength of ground ceramics may be affected by residual stress as well as surface flaws induced by grinding. Strength prediction for ground ceramics is convenient for mechanical design of ceramic components. In this article, a numerical procedure based on fracture mechanics was proposed to estimate strength distribution of ground ceramics by considering grinding-induced residual stress. Bending strength and residual stress of ground ceramics were measured for three grinding-conditions. By comparison of simulated results with experimental ones, it was revealed that strength characteristics in experiments were well simulated by using the proposed procedure.  相似文献   
65.
Many advanced document systems provide a formatting mechanism called ‘style sheets’ Style sheets provide a great deal of flexibility in describing a document's format, and allow easy maintenance of different house styles for a collection of documents. In this paper, we describe the basics of general style sheet systems, argue that successful document interchange must include the exchange of style sheet information, and evaluate ODA's style mechanism against this requirement.  相似文献   
66.
Due to their small size, mammalian oocytes and embryos pose unique problems during preparation for transmission electron microscopy. This paper outlines a method which combines protein embedding with centrifugation to locate the specimens on the face of a Beem capsule mould. This method facilitates both the processing of oocytes with minimal loss and rapid location of the specimens within the block for simultaneous sectioning, staining and examination.  相似文献   
67.
Reviews available research on the meaning and measurement of denial and strategies for treating maladaptive denial, with special reference to its occurrence in traumatic head injuries. Questionnaire or interview measures, rather than behavioral indices, are used to assess denial. Denial may be manifested with respect to past, present, or future status; and it may have both positive and negative consequences for coping, motivation, and rehabilitation. Where denial limits a patient's functioning or recovery, several treatment strategies are possible. Intervention should involve a balance between supportive and confrontational elements, with a focus on behaviors rather than verbalizations. Computer feedback, videotaping, focused group therapy, and supervised activities are possible interventions for confronting maladaptive forms of denial. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
68.
Updated the report of W. M. Cox and V. Catt (see record 1978-21651-001) by determining the 40 top contributing institutions to the Journal of Applied Psychology, 1976–1982, and assessed the generalizability of productivity rankings based solely on contributions to this journal. A number of industrial and organizational psychologists were asked to indicate all the journals in which psychologists in the field were likely to publish. Five journals suggested by these nominators were used for comparison in the review. A list of the 40 most productive graduate programs based on these 5 journals is included. Results show the inadequacy of Cox and Catt's decision to base productivity ratings solely on contributions to 1 journal. Using 5 journals, 4 programs were catapulted into the top 10 rankings, while 7 programs dropped from top rankings in the Cox study (1970–1975) to below the 65th rank in the present study. Using only the Journal of Applied Psychology contributions, 2 of these programs ranked in the top 10, 1976–1982. (5 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
69.
This study investigated jurors' reactions to judges' nonverbal communication in mock trials. Participants in 80 mock juries viewed taped segments of direct and cross examination that varied the judges' level of nonverbal involvement. Comments about the judge were solicited in predeliberation questionnaires and unsolicited comments obtained from dialogue that occurred during mock jury deliberations. The investigation found that jurors are aware of nonverbal cues from judges, particularly negative behaviors. Although the high- and low-involved judges solicited roughly the same number of comments, more negative comments were made about the judge displaying low than high nonverbal involvement. The results also revealed that jurors made more negative comments than positive ones. Overall, jurors are most aware of a judge's lack of involvement and apparent bias. Discussion focuses on ways to minimize the influence of judge nonverbal communication on jurors.  相似文献   
70.
During large scale wildfires, suppression activities are carried out under the direction of an Incident Management Team (IMT). The aim of the research was to increase understanding of decision processes potentially related to IMT effectiveness. An IMT comprises four major functions: Command, Operations, Planning, and Logistics. Four methodologies were used to study IMT processes: computer simulation experiments; analyses of wildfire reports; interviews with IMT members; and cognitive ethnographic studies of IMTs. Three processes were important determinants of IMT effectiveness: information management and cognitive overload; matching component function goals to overall goals; and team metacognition to detect and counter task‐disruptive developments. These processes appear to be complex multi‐person analogues of individual Incident Command processes identified previously. The findings have implications for issues such as: creating IMTs; training IMTs; managing IMTs; and providing decision support to IMTs.  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