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   4425篇
  免费   102篇
  国内免费   3篇
电工技术   21篇
综合类   11篇
化学工业   441篇
金属工艺   50篇
机械仪表   49篇
建筑科学   91篇
矿业工程   8篇
能源动力   57篇
轻工业   124篇
水利工程   4篇
石油天然气   7篇
无线电   142篇
一般工业技术   407篇
冶金工业   2738篇
原子能技术   15篇
自动化技术   365篇
  2023年   22篇
  2022年   33篇
  2021年   67篇
  2020年   50篇
  2019年   56篇
  2018年   50篇
  2017年   40篇
  2016年   63篇
  2015年   53篇
  2014年   54篇
  2013年   128篇
  2012年   97篇
  2011年   137篇
  2010年   97篇
  2009年   90篇
  2008年   104篇
  2007年   111篇
  2006年   77篇
  2005年   67篇
  2004年   50篇
  2003年   57篇
  2002年   51篇
  2001年   38篇
  2000年   26篇
  1999年   111篇
  1998年   769篇
  1997年   440篇
  1996年   295篇
  1995年   184篇
  1994年   161篇
  1993年   173篇
  1992年   49篇
  1991年   49篇
  1990年   57篇
  1989年   82篇
  1988年   54篇
  1987年   58篇
  1986年   37篇
  1985年   27篇
  1984年   11篇
  1983年   16篇
  1982年   23篇
  1981年   17篇
  1980年   28篇
  1979年   13篇
  1978年   18篇
  1977年   62篇
  1976年   133篇
  1975年   6篇
  1971年   6篇
排序方式: 共有4530条查询结果,搜索用时 12 毫秒
71.
Although enterprise systems (ES) are ubiquitous, many firms report less than stellar payoffs from these costly investments, with underutilization often attributed to failures in the implementation process. Unfortunately, research has not provided sufficient insights into these failures, in part because it has focused on actual usage, as opposed to proficient usage, as the benchmark for successful implementation. Moreover, research has not generally examined how the adoption process unfolds over time, thus overlooking potential underlying mechanisms that may help explain how adopters achieve proficiency. To begin addressing these shortcomings, we study how adopters’ pre-adoption expectations, enacted over time, can influence their post-adoption proficiency, by shaping how and why they spend time using the system during the adoption period. We analyzed time-lagged survey data from 153 financial analysts, required to adopt new ES-based software, at a multinational bank. We found that adopters who hold pre-adoption expectations reflecting greater internal and external motives to adopt the system as well as systematically integrate it into their work routines are more apt to use the system in ways that enhance their cumulative knowledge of it, and subsequently develop higher levels of proficiency post-adoption. Moreover, greater organizational support enhanced the impact of adopters’ expectations on proficiency, except when their actual use is low in which case organizational support had an adverse effect.  相似文献   
72.
An intelligent adaptable system, aware of a user’s experienced cognitive load, may help improve performance in complex, time-critical situations by dynamically deploying more appropriate output strategies to reduce cognitive load. However, measuring a user’s cognitive load robustly, in real-time is not a trivial task. Many research studies have attempted to assess users’ cognitive load using different measurements, but these are often unsuitable for deployment in real-life applications due to high intrusiveness. Relatively novel linguistic behavioral features as potential indices of user’s cognitive load is proposed. These features may be collected implicitly and nonintrusively supporting real-time assessment of users’ cognitive load and accordingly allowing adaptive usability evaluation and interaction. Results from a laboratory experiment show significantly different linguistic patterns under different task complexities and cognitive load levels. Implications of the research for adaptive interaction are also discussed, that is, how the cognitive load measurement-based approach could be used for user interface evaluation and interaction design improvement.  相似文献   
73.
Rivoaland  L.  Maurice  V.  Josso  P.  Bacos  M.-P.  Marcus  P. 《Oxidation of Metals》2003,60(1-2):137-157
The aim of this study was to improve the understanding of the deleterious effect of sulfur impurities on the adherence of the thermally-grown oxide on the boundary layer in thermal-barrier-coating systems. In Part I, the sulfur segregation on the free surface of NiAl(001) and at different interfaces between metal and transient alumina scales has been characterized by AES, XPS and LEED. The sulfur diffusion coefficient in the alloy has been determined (D = 0.15 exp(–218,000/RT) cm2/s). It is by three orders of magnitude larger than the nickel and aluminum self-diffusion coefficients. It has also been observed that the sulfur de-segregates upon Al enrichment of the metallic surface. The saturation of the metallic surface with an amorphous alumina layer formed at room temperature blocks the segregation of S. However, in the initial stages of oxidation where the transient -alumina grows by cationic transport and inject vacancies at the interface, S segregates at the interface between the alumina thin films and the metallic substrate.  相似文献   
74.
Alongside the emergence of the use of fieldwork studies for design there has been a discussion on how best these studies can inform system development. Concerns have been expressed as to whether their most appropriate contribution is a list of requirements or design recommendations. This article explores a recurrent issue that has emerged from fieldwork studies in Computer-Supported Cooperative Work, awareness, and with respect to a particular system development project discusses some of the implications for the development and deployment of one particular kind of technology—image recognition systems—in particular, organizational settings. In the setting in question—surveillance centers or operations rooms—staff utilize a range of practices to maintain awareness. Rather than extending field studies so that they can better assist design, it may be considered how workplace studies can contribute to a respecification of key concepts, like awareness, that are critical to an understanding of how technologies are used and deployed in everyday environments.  相似文献   
75.
Entanglement in high-dimensional many-body systems plays an increasingly vital role in the foundations and applications of quantum physics. In the present paper, we introduce a theoretical concept which allows to categorize multipartite states by the number of degrees of freedom being entangled. In this regard, we derive computable and experimentally friendly criteria for arbitrary multipartite qudit systems that enable to examine in how many degrees of freedom a mixed state is genuine multipartite entangled.  相似文献   
76.
77.
The morbidity and mortality in short bowel syndrome are directly related to the length of the remaining small bowel and to the duration of total parenteral nutrition. We describe the successful salvage of an infant with extensive small bowel infarction for whom a new technique was used to preserve all viable mucosal surfaces. The infant, with gastroschisis, was found to have a tight volvulus of the extruded bowel and extensive small bowel ischemia at the time of delivery. Forty-eight hours after reduction of the volvulus and abdominal decompression, a second-look laparotomy was performed. Although only the terminal 13 cm of ileum was completely viable, 25% of the circumference of a further 23 cm of proximal jejunum/ileum was considered salvageable. After debridement of the dead tissue, the remaining gutter of jejunum was divided at its midpoint, and the two halves were anastomosed longitudinally to provide a "neojejunum" of 12 cm in length, which was anastomosed between the duodenum and terminal ileum. Full enteral feeding was tolerated from day 47. Although the neojejunum was excised on day 149, after becoming dilated and atonic, by that time the remaining small bowel had elongated to 30 cm. Because of the early institution of full enteral feeding, there were no long-term complications related to total parenteral nutrition.  相似文献   
78.
OBJECTIVE: This study explored psychosocial and "environmental" correlates of childhood anxiety disorders. The study examined relationships among parental psychiatric symptomatology, perceived family environment, temperament, and self-competence in children with a DSM-III-R anxiety disorder. METHOD: A community sample of third through sixth graders was screened initially for symptoms of test anxiety. Those with high and low scores were administered the Anxiety Disorders Interview Schedule for Children. Three groups (childhood anxiety disorder, test-anxious only, and normal controls) were identified and compared on the psychosocial variables. RESULTS: Children with an anxiety disorder had greater impairment on the indices of perceived self-competence and temperamental flexibility than controls, with the test-anxious children showing intermediate, yet significant, levels of disturbance. There was a trend for children with an anxiety disorder to describe their families as less promoting of independence than the other groups. Finally, measures of parental psychiatric symptomatology revealed more obsessive-compulsive symptoms for the fathers of both the anxiety disorder and test-anxious children compared with controls. CONCLUSIONS: Results are consistent with previous findings suggesting the familial transmission of anxiety disorders and recent speculations regarding a relationship between behavioral inhibition, environmental control, and anxiety. Further research may isolate psychosocial and family environmental factors as instrumental treatment targets in the management of childhood anxiety disorders.  相似文献   
79.
An Ar atmospheric treatment is rationally used to etch and activate hematite nanoflakes (NFs) as photoanodes toward enhanced photoelectrochemical water oxidation. The formation of a highly ordered hematite nanorods (NRs) array containing a high density of oxygen vacancy is successfully prepared through in situ reduction of NFs in Ar atmosphere. Furthermore, a hematite (104) plane and an iron suboxide layer at the absorber/back‐contact interface are formed. The material defects produced by a thermal oxidation method can be critical for the morphology transformation from 2D NFs to 1D NRs. The resulting hematite NR photoanodes show high efficiency toward solar water splitting with improved light harvesting capabilities, leading to an enhanced photoresponse due to the artificially formed oxygen vacancies.  相似文献   
80.
The classic hypoglossal transfer to the facial nerve is invariably followed by complications caused by tongue atrophy. In 1984, Terzis introduced the "baby-sitter" procedure which involved a formal cross-facial procedure, in addition to partial neurectomy of the hypoglossal nerve, and an end-to-side coaptation with the ipsilateral facial nerve. This reported study provides, for the first time, quantification of the number of hypoglossal motor fibers needed to successfully restore eye sphincter function, using an end-to-side coaptation with preservation of the tongue. Thirty adult Sprague-Dawley rats were divided into six groups: control, denervated, perineurial window, 20 percent partial neurectomy (PN), 40 percent PN, and 80 percent PN. The procedure involves interposing a nerve graft (saphenous) between the partially severed XII nerve and the upper zygomatic branch of the facial nerve. Evaluation of the behavioral data (blink reflex) revealed good-to-superb return of the blinking mechanism in the 40 percent group, without significant tongue atrophy. Electrophysiologic data in the 40 percent neurectomy group demonstrated superiority to the other groups. Quantitative axonal morphometry of the coaptation sites and graft, as well as motor end-plates of the orbicularis oculi muscle and tongue showed the 40 percent partial neurectomy group to be the optimal group.  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