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   19210篇
  免费   871篇
  国内免费   27篇
电工技术   232篇
综合类   18篇
化学工业   4044篇
金属工艺   350篇
机械仪表   424篇
建筑科学   1059篇
矿业工程   52篇
能源动力   540篇
轻工业   1792篇
水利工程   129篇
石油天然气   56篇
武器工业   1篇
无线电   1687篇
一般工业技术   3328篇
冶金工业   3101篇
原子能技术   198篇
自动化技术   3097篇
  2023年   150篇
  2022年   237篇
  2021年   481篇
  2020年   366篇
  2019年   389篇
  2018年   457篇
  2017年   425篇
  2016年   536篇
  2015年   456篇
  2014年   580篇
  2013年   1160篇
  2012年   943篇
  2011年   1194篇
  2010年   842篇
  2009年   896篇
  2008年   948篇
  2007年   814篇
  2006年   747篇
  2005年   644篇
  2004年   538篇
  2003年   480篇
  2002年   463篇
  2001年   309篇
  2000年   339篇
  1999年   364篇
  1998年   759篇
  1997年   489篇
  1996年   408篇
  1995年   298篇
  1994年   286篇
  1993年   283篇
  1992年   189篇
  1991年   167篇
  1990年   146篇
  1989年   146篇
  1988年   131篇
  1987年   124篇
  1986年   122篇
  1985年   148篇
  1984年   141篇
  1983年   120篇
  1982年   100篇
  1981年   103篇
  1980年   85篇
  1979年   100篇
  1978年   90篇
  1977年   117篇
  1976年   140篇
  1975年   84篇
  1974年   75篇
排序方式: 共有10000条查询结果,搜索用时 953 毫秒
141.
As treatments have improved health and quality of life for people with HIV/AIDS, many have contemplated workforce reentry. Workforce reentry rarely occurs among people with illness-related disability. The authors mailed a survey that included workforce-entry-related concerns to 1,991 HIV/AIDS clients. Factor analysis extracted 6 areas of concern (benefits loss, work-related health, job skills, discrimination, personal health care, workplace accommodation). Levels of concern generally increased with HIV acuity level and time since last worked. Work-related health concerns predicted consideration of workforce entry, and work-related health concerns and benefits-loss concerns predicted estimated time to return to work. Findings provide quantitative validation of intuitive categories of workforce-entry concerns among people with HIV/AIDS and suggest that concerns may shift with progress toward workforce entry. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
142.
Modellierung in der Lehre an Hochschulen: Thesen und Erfahrungen   总被引:1,自引:1,他引:0  
Zusammenfassung  Nicht erst seit Modellierung zum Modewort geworden ist, ist Modellierung ein wichtiges Thema in der Informatikausbildung. Dieser Beitrag beleuchtet in zw?lf Thesen das Warum, Was, Wie viel, Wo, Wann und Wie von Modellierung in der Lehre im Rahmen informatikbezogener Studieng?nge. Die Thesen basieren auf der Erfahrung des Verfassers mit einer seit über zehn Jahren gehaltenen Modellierungsvorlesung an der Universit?t Zürich sowie dem Gedankenaustausch mit anderen Hochschullehrerinnen und -lehrern im Rahmen der GI-Workshopreihe ,,Modellierung“. Zus?tzlich liefert eine Befragung von Absolventinnen und Absolventen an der Universit?t Zürich empirische Evidenz für eine Reihe der Thesen.  相似文献   
143.
144.
To be able to perform more realistic simulations of timber constructions with modern numerical simulation methods like the finite element method (FEM), a suitable constitutive material model is required. Such a material model was developed by Mackenzie-Helnwein et al. (2005) for clear spruce wood. This paper presents an application-oriented adaption and usage of the mentioned material model, its implementation in a FE software as well as performing ultimate load analyses using FEM and the validation of the material model by means of the comparison of results of FE Simulations and experiments on the structure level (Fleischmann 2005). Further, some aspects with respect to the standardisation are discussed in one of the two examples.  相似文献   
145.
Polycrystalline A1N thin films were deposited by RF reactive magnetron sputtering on Pt(111)/Ti electrode films. The substrates were tilted by an angle ranging from 40 degrees to 70 degrees with respect to the target normal. A low deposition temperature and a high sputter gas pressure were found ideal for tilted growth. The resulting grain tilt angle amounts to about half the substrate tilt angle. For coupling evaluation, 5 GHz solidly mounted resonator structures have been realized. The tilted grain A1N films exhibited a permittivity in the 9.5-10.5 range and loss tangent of 0.3%. Two shear modes as well as the longitudinal mode could be clearly identified. The coupling coefficient k2(eff) of the fundamental thickness shear mode (TS0) was found to be about 0.5%, which is compatible with a c-axis tilt of about 6 degrees.  相似文献   
146.
147.
148.
Summary We introduce a very simple model for thermally activated atomic migration on a lattice, and several techniques to handle it. For thermodynamical systems, the model can be used for simulating decomposition paths taking into account relevant metallurgical features. Close to equilibrium, the simplest mean-field approximation of the model can be linearized with respect to the departure from equilibrium; one then gets a microscopic interpretation of classical phenomenological coefficients, such as mobility, interfacial transfer coefficient, rate constants for the coupled relaxation of concentration and order fields. Further away from the equilibrium, the nonlinearities can be taken into account in a consistent way. For driven alloys, i.e. alloys submitted to external forcing, forced atomic migration is added to the model and new features emerge: the model is supported by several experimental results some of which confirmed its predictions a posteriori.  相似文献   
149.
In farm animals as in human, reproduction is affected by changes in the level of energetic balance. The main factors that link metabolism and reproduction, like insulin, IGFs, glucose, FFA, leptin and NPY, act on hypothalamo-pituitary axis as well as on gonads by directly altering gametogenesis.  相似文献   
150.
BACKGROUND: This study evaluated the perceptions of patients with breast cancer of their medical interactions with providers. The determinants and psychological consequences of communication problems also were examined. METHODS: Ninety-seven patients with Stage I or II breast cancer completed a set of validated questionnaires before initiating postoperative therapy. Data on psychological distress were collected at baseline and 3-month follow-up, and multivariate models were fit to explain the relationship between pretreatment communication problems and subsequent psychological distress. Data on clinical variables were abstracted from medical records. RESULTS: A substantial proportion of patients (84%) reported difficulties communicating with the medical team. Communication problems were more common among patients who were less optimistic about their disease and had less assertive coping styles. Patient-reported communication problems were associated with increased anxiety, depression anger, and confusion at the 3-month follow-up. The association between communication problems and mood disturbance remained significant, although small, after adjusting for baseline mood disturbance, demographic, clinical, and coping style variables. CONCLUSION: Interventions that enhance communication between patients with breast cancer and their providers may improve patients' psychological adjustment to treatment. Conversely, interventions that lower distress and modify coping style may enhance communication.  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