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   15239篇
  免费   496篇
  国内免费   19篇
电工技术   265篇
综合类   3篇
化学工业   3162篇
金属工艺   369篇
机械仪表   295篇
建筑科学   527篇
矿业工程   96篇
能源动力   380篇
轻工业   1105篇
水利工程   109篇
石油天然气   70篇
武器工业   1篇
无线电   1950篇
一般工业技术   1975篇
冶金工业   3761篇
原子能技术   192篇
自动化技术   1494篇
  2022年   193篇
  2021年   302篇
  2020年   194篇
  2019年   233篇
  2018年   268篇
  2017年   273篇
  2016年   246篇
  2015年   226篇
  2014年   309篇
  2013年   919篇
  2012年   401篇
  2011年   486篇
  2010年   387篇
  2009年   472篇
  2008年   397篇
  2007年   340篇
  2006年   356篇
  2005年   319篇
  2004年   265篇
  2003年   289篇
  2002年   301篇
  2001年   286篇
  2000年   270篇
  1999年   339篇
  1998年   1020篇
  1997年   712篇
  1996年   518篇
  1995年   380篇
  1994年   389篇
  1993年   363篇
  1992年   273篇
  1991年   243篇
  1990年   251篇
  1989年   276篇
  1988年   206篇
  1987年   188篇
  1986年   168篇
  1985年   132篇
  1984年   124篇
  1983年   102篇
  1982年   108篇
  1981年   127篇
  1980年   117篇
  1979年   100篇
  1978年   101篇
  1977年   169篇
  1976年   206篇
  1975年   100篇
  1972年   91篇
  1970年   78篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
The combination of N-(phosphonacetyl)-L-aspartate, 6-methylmercaptopurine, and 6-aminonicotinamide has been shown to be an effective antineoplastic regimen and also to enhance the effects of other chemotherapeutic agents. The mechanism of action of this combination of drugs is not known definitively, but one possible mechanism is biochemical modulation of energy metabolism and inhibition of production of tumor ATP. Tumor-bearing mice were treated with N-(phosphonacetyl)-L-aspartate, followed 17 h later by 6-methylmercaptopurine and 6-aminonicotinamide. 31P nuclear magnetic resonance spectroscopic studies demonstrated a significant depletion of high energy phosphates at 10 h post-6-methylmercaptopurine and 6-aminonicotinamide. The addition of radiation at this time was shown to induce a significantly longer tumor growth delay and a greater number of regressions (including durable complete regressions) than either chemotherapy or radiation alone. The combination of chemotherapy and radiation was found to be supra-additive compared to the antineoplastic effects of either modality administered separately, without a measurable increase in host toxicity.  相似文献   
62.
63.
By Cooperative Editing we mean the coordinated manipulation of information by a group of authors. During the editing process the (co-)authors need to communicate their ideas, drafts and constraints (remotely or face-to-face) until a final version of the information is achieved. For the different phases of this process - discussion of ideas, editing, cross-checking - different media or media integration are adequate. Furthermore, analysing the transition from individual work to group work, within different human activities, two pitfalls are often detected if computer support is considered: a) technological communication difficulties, especially if the group is remotely located on heterogeneous hardware, associated with a fall in productivity and frequent social inadequacies of the group's computer support; b) the lack of integrated media processing tools available for group editing. In order to solve these problems, we suggest that Multimedia can be applied in two ways: to effectively support the necessary group communication links; and to enhance the expressiveness of the information edited. To test this statement we have been conceptualising and implementing a prototype system. Most of the techniques involved can be used in other tools that need multimedia capabilities or that support other specific types of group activities. The innovative aspects of the work are the use of multimedia techniques to support demanding applications, possibly on cross-platforms, and the integration of several concepts to support cooperation.  相似文献   
64.
The effects of nitrogen-beam voltage on the structure, stress, energy band gap and hardness of AIN thin films deposited on Si (111), Si (100) and sapphire (0001) by ion beam assisted deposition (IBAD) are reported. As the nitrogen-beam voltage was increased from 50 to 200 V, the stress and disorder in the AIN films increased as determined by X-ray diffraction, FTIR and Raman spectroscopy. The preferred orientation of the film's c-axis changed from completely normal to the film at 100 V, to a mixture of normal and in the plane of the film at 200 V. For AIN films deposited under the same conditions, the films were more highly oriented on sapphire (0001) than in Si (111). The hardness of the films increased from 18.2 to 23.7 GPa with the nitrogen-beam voltage, and possible reasons for this change in hardness are considered.  相似文献   
65.
Chemometrics has enjoyed tremendous success in the areas related to calibration of spectrometers and spectroscopy-based measurements. These chemometric-based spectrometers have been widely applied for process monitoring and quality assurance. However, chemometrics has the potential to revolutionize the very intellectual roots of problem solving. Are there barriers to a more rapid proliferation of chemometric-based thinking, particularly in industry? What are the potential effects of chemometrics technology and the New Network Economy (NNE) working in concert? Who will be the winners in the race for faster, better, cheaper systems and products? These questions are reviewed in terms of the principles of the NNE and in the promise of chemometrics for industry. What then is the state of multivariate thinking in industry? Several powerful principles are derived from an evaluation of the NNE and chemometrics which could allow chemometrics to proliferate much more rapidly as a key general problem-solving tool.  相似文献   
66.
CoMEdiA is a groupware tool which enables co-authors to cooperatively produce hypermedia documents.CoMEdiA allows co-authors to communicate their ideas,drafts,guidelines,constraints and annotations to other co-authors.In uses a mix of communication patterns,media and document organization to enable co-authors to keep on exchanging information(remotely or face-to-face),improving passages and modifying notes until a final document is achieved.We did not concentrate on th depth but on the breath of the features.Our efforts were on integrating and corrdinating concepts from collaboration,multimedia and hyper organization rather than on making a specialized system in any of them.We began with the text medium and are now including bitmaps and raster images.Later sound and video will also be integrated.In this paper we describe and sustain the available capacites.  相似文献   
67.
The use of conventional ultrasound systems to image the upper airway has been limited because ultrasound energy is attenuated by the air column. In an attempt to study upper airway geometry, we developed a computer controlled bi-directional ultrasound system which combines two conventional ultrasound devices with computer image processing to yield images of upper airway structures. Human studies and cadaver studies were performed to evaluate the system. Images acquired by the bi-directional ultrasound system were comparable to images from 3D volume rendered CT scans. This system may provide valuable data in the study of upper airway physiology and pathology.  相似文献   
68.
69.
In this article the direct boundary element formulations of stretching and bending plate problems are combined together to solve thin walled structures and other similar frames. The final system is obtained by assuming each individual plane structural element as a subregion. After the necessary transforms of these equations they can be combined together taking into account the displacement compatibility and equilibrium conditions.  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