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   5780篇
  免费   198篇
  国内免费   9篇
电工技术   36篇
综合类   4篇
化学工业   969篇
金属工艺   57篇
机械仪表   76篇
建筑科学   259篇
矿业工程   31篇
能源动力   63篇
轻工业   786篇
水利工程   48篇
石油天然气   40篇
无线电   228篇
一般工业技术   684篇
冶金工业   1983篇
原子能技术   12篇
自动化技术   711篇
  2023年   32篇
  2022年   77篇
  2021年   94篇
  2020年   59篇
  2019年   79篇
  2018年   92篇
  2017年   97篇
  2016年   98篇
  2015年   81篇
  2014年   125篇
  2013年   340篇
  2012年   198篇
  2011年   321篇
  2010年   228篇
  2009年   235篇
  2008年   262篇
  2007年   278篇
  2006年   237篇
  2005年   201篇
  2004年   176篇
  2003年   176篇
  2002年   174篇
  2001年   102篇
  2000年   112篇
  1999年   109篇
  1998年   111篇
  1997年   117篇
  1996年   131篇
  1995年   94篇
  1994年   112篇
  1993年   126篇
  1992年   107篇
  1991年   45篇
  1990年   100篇
  1989年   102篇
  1988年   72篇
  1987年   88篇
  1986年   84篇
  1985年   86篇
  1984年   64篇
  1983年   65篇
  1982年   46篇
  1981年   52篇
  1980年   42篇
  1979年   43篇
  1978年   27篇
  1977年   44篇
  1976年   25篇
  1975年   34篇
  1974年   24篇
排序方式: 共有5987条查询结果,搜索用时 15 毫秒
71.
This study investigated the effectiveness of different types of on-line feedback following user errors for informing users of the information and functions available in a system with a natural language interface. Twenty-four individuals performed a task based on an industry cost savings program, in which they were given general goals to pursue with regard to the task. Three feedback levels which differed according to the type and amount of feedback provided, along with two levels of system complexity, were examined. In addition, subjects performed the task again after one week to determine the effects of feedback on retention. Results indicated that the subjects in the second level of feedback generally performed better with respect to accessing system functions and information than those in the first level. Although there was some performance improvement from the second to third level, it was not significant. However, the third level of feedback did significantly improve the efficiency with which subjects used information to complete the task during the return condition. Overall, feedback did not affect the errors made, though at certain more limited stages of the tasks this effect was observed.  相似文献   
72.
73.
Reviews evidence concerning the congruence of the inductive and deductive models in logic and presents support for this congruence in the context of new test items designed to exemplify general-to-particular induction. Data from the Professional and Administrative Career Examination corroborate the logical foundations of deduction and induction as convergent models. Factor analysis of the items demonstrated factorial convergence, which lends additional support to the postulate of convergence. Implications for the understanding of cognitive processes and for psychometric practice are discussed in relation to such issues as the use of verbal and nonverbal test media, redundancy of measurement, and problem-solving strategies. (50 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
74.
Using newly developed test equipment, the fatigue behavior of nylon 66 monofilaments was studied under two loading conditions, pure bending or simple torsion. For each mode, results are expressed in terms of the measured decay in stiffness with numbers of cycles over a range of maximum applied strain levels. Fatigue lifetimes are presented in S–N format where the log number of cycles of fatigue for a 40% decay in stiffness (N) is plotted as a function of applied strain (S). The failure mechanism for these fibers in each fatigue mode reflects the morphology of semicrystalline-oriented synthetic fibers. In torsion, many longitudinal cracks form around the perimeter of a fiber as the result of cleavage of the relatively weak interfibrillar bonds in nylon 66. In bending, cracks form within kink band boundaries and grow at an oblique angle to the fiber axis. © 1992 John Wiley & Sons, Inc.  相似文献   
75.
Contends that tests in repeated-measures designs based on MANOVA are free of sphericity assumptions, and with modern computing software, MANOVA is straightforward to use, even for complex designs and nontraditional hypotheses. A general strategy for implementing MANOVA within statistical computing packages is presented. Regular (preplanned) tests and simultaneous (post hoc) tests are illustrated for a variety of designs and hypotheses. Optimal contrasts for unbalanced repeated measures designs are appended. (33 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
76.
Few well-documented cases of central nervous system involvement in patients with hepatitis C virus infection have been reported. We describe three patients (two men and one woman) with cerebral involvement (ischemia and/or hemorrhage). Hepatitis C virus infection was confirmed in all patients by polymerase chain reaction detection of hepatitis C virus RNA. These three cases document the occurrence of central nervous system involvement in patients with hepatitis C virus infection and mixed cryoglobulinemia. Cerebral involvement may be the initial manifestation of hepatitis C virus infection.  相似文献   
77.
The electronic mail (EM) network in a large, multi-campus community college district was used by some employees to gain support for positions contrary to those of the leadership. The case study offered an opportunity to look at technology within an organizational setting. It raised questions about the loose coupling of the educational organization's technical and authority systems, about the strength of coupling among employee groups during the incident, about the boundaries of the EM political activists, and about the power manifested within educational organization's technical and authority systems. A variety of research methods (stages of event progression, fantasy types associated with consciousness-building, and evidence of user technical and rhetorical skills) were used to answer questions about the organization's loosely coupled systems during the EM political incident. Notes were taken of conversations and more formal interviews. From this the technical and authority systems of the institution were described and compared. Results indicated that (1) the loose coupling of the technical and the authority systems made the EM political incident possible; (2) employees were more tightly coupled on organizational goals and more loosely coupled on organizational means; (3) political activists did not make full use of the EM's political medium potential; and (4) when the college district's administration refused to limit anyone's use of the EM network, they reinforced the integrity of both the authority and the technical systems.

Implications included: (1) the potential of some of the research methods for EM study, especially fantasy theme analysis; (2) a political interpretation of EM language, especially flaming; (3) the importance of technical and rhetorical skills for mature EM users; and (4) the role of the authority and technical systems in the debate about appropriate EM network use within an organization.  相似文献   
78.
Client/server, open systems, joint application development, and legacy systems—what happens when the silver bullet meets the glass house? And what does all of this have to do with end-user computing, anyway? Read this column and find out.  相似文献   
79.
The coevolution of genomics and proteomics has led to advancements in the field of diagnosis and molecular mechanisms of disease. Proteomics is now stepping into the field of obstetrics, where early diagnosis of pregnancy complication such as preeclampsia (PE) is imperative. PE is a multifactorial disease characterized by hypertension with proteinuria, which is a leading cause of maternal and neonatal morbidity and mortality occurring in 5-7% of pregnancies worldwide. This review discusses the probable molecular mechanisms that lead to PE and summarizes the proteomics research carried out in understanding the pathogenicity of PE, and for identifying the candidate biomarker for diagnosis of the disease.  相似文献   
80.
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