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   269667篇
  免费   3273篇
  国内免费   1086篇
电工技术   6108篇
综合类   714篇
化学工业   44605篇
金属工艺   11220篇
机械仪表   7515篇
建筑科学   7957篇
矿业工程   659篇
能源动力   6806篇
轻工业   26911篇
水利工程   2142篇
石油天然气   1548篇
武器工业   3篇
无线电   31894篇
一般工业技术   48617篇
冶金工业   51154篇
原子能技术   4166篇
自动化技术   22007篇
  2021年   2589篇
  2020年   2232篇
  2019年   2293篇
  2018年   3016篇
  2017年   2735篇
  2016年   3249篇
  2015年   2867篇
  2014年   4154篇
  2013年   12490篇
  2012年   6243篇
  2011年   8572篇
  2010年   7293篇
  2009年   8043篇
  2008年   8236篇
  2007年   8290篇
  2006年   7603篇
  2005年   6963篇
  2004年   6619篇
  2003年   6670篇
  2002年   6515篇
  2001年   6612篇
  2000年   6000篇
  1999年   6616篇
  1998年   17011篇
  1997年   11922篇
  1996年   9261篇
  1995年   6952篇
  1994年   6177篇
  1993年   6045篇
  1992年   4257篇
  1991年   4160篇
  1990年   3781篇
  1989年   3718篇
  1988年   3605篇
  1987年   3109篇
  1986年   3044篇
  1985年   3605篇
  1984年   3256篇
  1983年   2941篇
  1982年   2711篇
  1981年   2788篇
  1980年   2614篇
  1979年   2454篇
  1978年   2374篇
  1977年   2979篇
  1976年   4353篇
  1975年   2090篇
  1974年   1985篇
  1973年   2128篇
  1972年   1635篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
62.
63.
The biological decolorization of two industrial, spent textile reactive dyebaths was investigated using a suspended-growth, halophilic mixed culture fed with glucose. Dyebath I contained mainly Reactive Blue 19 (RB19), an anthraquinone dye, whereas dyebath II contained mainly Reactive Blue 21 (RB21), a phthalocyanine dye. Batch assays under anaerobic conditions with the two neutralized dyebaths resulted in 87 and 37% extent of decolorization for dyebaths I and II, respectively. The rate of glucose utilization and the extent of acetate production were impacted in the presence of each dyebath as compared to the control culture. However, dyebath decolorization occurred despite moderate culture inhibition. Reuse of a biologically renovated RB19-containing dyebath in the dyeing process resulted in reproducible but not identical cotton fabric shades as compared to a standard dyeing (i.e., control) using fresh water. This difference is attributed to a variable degree of RB19 aggregation during the dyeing process and is not related to the efficiency of the biodecolorization process. Further improvement of the redyeing efficiency will lead to the development of an in-plant, closed-loop decolorization system resulting in significant water conservation and minimization of textile pollutants such as salt and dyes.  相似文献   
64.
Sure System 2000, a fault-tolerant computer that couples multiprocessors to offer low-priced, high-performance systems that deal effectively with faults and failures, is presented. The architecture is based on the local redundancy technique, ensuring that no hardware or software fault can cause a system crash. Software errors can be fixed, and hardware can be replaced, upgraded, or added dynamically. Existing fault-tolerant computers are briefly reviewed, and the logic hardware system configuration of the Sure System 2000 is described. The multiprocessor and I/O architecture are examined. The SXO Sure System 2000 expandable operating system is described  相似文献   
65.
The new Editor in Chief of IEEE Micro introduces himself and the first issue of 2007. He thanks outgoing Editor in Chief Pradip Bose for his outstanding work on Micro during his tenure. He assesses the current state of the microarchitecture field, speculates on the future, and asks readers for their suggestions on topics the magazine should cover in coming issues.  相似文献   
66.
Assessments of sewer performance are usually based on a single computation of CSO (combined sewer overflow) volumes using a time series of rainfall as system loads. A shortcoming of this method is that uncertainties in knowledge of sewer system dimensions are not taken into account. Moreover, sewer models are rarely calibrated. This paper presents the impacts of database errors and model calibration on return periods of calculated CSO volumes. The impact of uncertainties is illustrated with two examples. Variability of calculated CSO volumes is estimated using Monte Carlo simulations. The results show that calculated CSO volumes vary considerably due to database errors, especially uncertain dimensions of the catchment area. Furthermore, event-based calibration of a sewer model does not result in more reliable predictions because the calibrated parameters have low portability. However, it enables removal of database errors harmonising model predictions and 'reality'.  相似文献   
67.
An algorithm, 'phylogenetic scanning', is described for mapping gene conversion events where comparative DNA sequence data are available from different species. In this algorithm, sets of hypothetical phylogenetic trees are constructed that describe possible sequence relationships due to gene conversions in different species lineages; these trees are then evaluated by the principle of parsimony at intervals in the sequence alignment. When used to map gene conversion events that occurred between the pair of gamma-globin genes of higher primates, the algorithm gives results nearly identical to those obtained using a tedious manual approach. Suggestions are also provided for adaptation of this procedure to the analysis of other recombination events.  相似文献   
68.
Modern helicopter design depends on the successful combination of materials to fulfil a very wide range of critical functions. In the past few years demands from the aerospace industry have caused considerable enhancement in the favourable properties of both polymer based materials and metals. These are discussed in connection with the progressive technical evolution of helicopters and other advanced technological products from the Westland Group.  相似文献   
69.
Presents a model suitable for computing images of absorption cross sections of thick tissue structures illuminated at near infrared (NIR) wavelengths from tomographic projection data. Image reconstruction is accomplished by solving a system of linear equations derived from transport theory. Reconstruction results using different algebraic solvers are shown for anatomical maps of the breast, derived from magnetic resonance imaging data, containing two simulated pathologies, in which case qualitatively good reconstructions were obtained. Evaluation of magnetic resonance (MR) data to optimize NIR optical tomographic imaging methods and to assess the feasibility of a combined MR-optical measurement scheme is discussed  相似文献   
70.
In this paper the results are presented of a test program on the energy absorption of composite cylinders loaded in compression. The influence of the laminate lay-up and of the trigger configuration were determined. Two different failure modes for the different laminates and triggers were observed: a splaying mode and a fragmentation mode. The splaying mode is more efficient in absorbing energy. The failure mode did not change during the crushing process.  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