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   245142篇
  免费   3056篇
  国内免费   1255篇
电工技术   4847篇
综合类   273篇
化学工业   35948篇
金属工艺   10888篇
机械仪表   7090篇
建筑科学   6367篇
矿业工程   505篇
能源动力   6313篇
轻工业   24296篇
水利工程   1843篇
石油天然气   1346篇
武器工业   3篇
无线电   31155篇
一般工业技术   45220篇
冶金工业   50195篇
原子能技术   3864篇
自动化技术   19300篇
  2021年   1610篇
  2019年   1466篇
  2018年   2351篇
  2017年   2258篇
  2016年   2509篇
  2015年   1979篇
  2014年   3257篇
  2013年   10892篇
  2012年   5532篇
  2011年   7885篇
  2010年   6339篇
  2009年   7054篇
  2008年   7627篇
  2007年   7730篇
  2006年   7094篇
  2005年   6587篇
  2004年   6292篇
  2003年   6308篇
  2002年   6276篇
  2001年   6393篇
  2000年   5824篇
  1999年   6443篇
  1998年   16586篇
  1997年   11618篇
  1996年   8972篇
  1995年   6712篇
  1994年   5932篇
  1993年   5753篇
  1992年   4073篇
  1991年   4015篇
  1990年   3600篇
  1989年   3521篇
  1988年   3451篇
  1987年   2915篇
  1986年   2858篇
  1985年   3426篇
  1984年   3060篇
  1983年   2762篇
  1982年   2554篇
  1981年   2582篇
  1980年   2445篇
  1979年   2282篇
  1978年   2249篇
  1977年   2816篇
  1976年   4178篇
  1975年   1903篇
  1974年   1801篇
  1973年   1788篇
  1972年   1463篇
  1971年   1320篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
101.
102.
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   
103.
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   
104.
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   
105.
High cycle fatigue of bolted connections Extensive tests regarding the influences on the fatigue of bolt‐nut‐connections of preloading with torsion, of preloading with yielding, of loading with superimposed bending and of the tested lot are processed. These influences are not yet known according to VDI 2230. New testing devices were designed for these tests, which allow a far less expensive operation and may easily be used for bolts of diameters up to M100 and testing frequencies up to 1000 Hz. The validity of fatigue resistance according to VDI 2230 is specified with respect to the test results. The determined influence of the tested lots is unexpectedly high. The manufacturing process of bolts should be improved to minimize this influence.  相似文献   
106.
107.
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   
108.
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   
109.
110.
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