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   92874篇
  免费   7288篇
  国内免费   3586篇
电工技术   5097篇
技术理论   5篇
综合类   5910篇
化学工业   16233篇
金属工艺   5582篇
机械仪表   5674篇
建筑科学   8083篇
矿业工程   2666篇
能源动力   2474篇
轻工业   5581篇
水利工程   1632篇
石油天然气   5309篇
武器工业   727篇
无线电   9921篇
一般工业技术   11189篇
冶金工业   4971篇
原子能技术   1115篇
自动化技术   11579篇
  2024年   296篇
  2023年   1473篇
  2022年   2360篇
  2021年   3473篇
  2020年   2656篇
  2019年   2244篇
  2018年   2614篇
  2017年   2964篇
  2016年   2525篇
  2015年   3408篇
  2014年   4264篇
  2013年   5245篇
  2012年   5762篇
  2011年   6196篇
  2010年   5272篇
  2009年   5196篇
  2008年   5030篇
  2007年   4780篇
  2006年   5065篇
  2005年   4479篇
  2004年   2990篇
  2003年   2590篇
  2002年   2386篇
  2001年   2126篇
  2000年   2412篇
  1999年   2810篇
  1998年   2404篇
  1997年   1916篇
  1996年   1918篇
  1995年   1541篇
  1994年   1265篇
  1993年   910篇
  1992年   721篇
  1991年   573篇
  1990年   412篇
  1989年   351篇
  1988年   291篇
  1987年   196篇
  1986年   135篇
  1985年   93篇
  1984年   77篇
  1983年   46篇
  1982年   55篇
  1981年   36篇
  1980年   30篇
  1979年   15篇
  1978年   15篇
  1977年   8篇
  1976年   34篇
  1956年   8篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
991.
一种基于ARM的集中器的硬件实现   总被引:4,自引:1,他引:3  
介绍了一种以ARM9为核心,以Windows CE5.0为操作系统的集中器。它符合国家电网的Q/GDW 374.2-2009技术标准,可以在国家电网中使用。给出了集中器的系统框图,介绍了集中器的主要实现电路,论述了其主要工作原理。  相似文献   
992.
With the fast development of cloud computing and wide application of cloud storage, the energy efficiency of cloud storage system is drawing significant attention from researchers or specialists. For the typical Dynamo cloud storage system, we design a new policy instead of the consistent hashing policy which is a combination of consistent hashing and sequential policy. The basic idea of this policy is that it divides the nodes into groups and allows each other to be mirror modes so it can find the full coverage subset of data items easily. Also we use autoregressive-moving-average model to estimate the task numbers of servers so that when under low utilization period, certain numbers of servers can be turned off to save energy. Based on the model, we demonstrate that it can save up to 23.7 % energy and maintain load balancing of servers. Furthermore, we compare our policy with Heuristic which is a classical energy conservation policy for cloud storage system that is based on consistent hash table. And we find several advantages of our policy which include finding the minimum subset of full coverage as well as other aspects.  相似文献   
993.
Email spam filtering is typically treated as a binary classification problem that can be solved by machine learning algorithms. We argue that a three-way decision approach provides a more meaningful way to users for precautionary handling their incoming emails. Three email folders instead of two are produced in a three-way spam filtering system, a suspected folder is added to allow users make further examinations of suspicious emails, thereby reducing the chances of misclassification. Different from existing ternary email spam filtering systems, we focus on two issues that are less studied, that is, the computation of required thresholds to define the three email categories, and the interpretation of the cost-sensitive characteristics of spam filtering. Instead of supplying the thresholds based on intuitive understandings of the levels of tolerance for errors, we systematically calculate the thresholds based on decision-theoretic rough set model. A loss function is interpreted as the costs of making classification decisions. A decision is made for which the overall cost is minimum. Experimental results show that the new approach reduces the error rate of misclassifying a legitimate email to spam and demonstrates a better performance for the cost-sensitivity aspect.  相似文献   
994.
A new model to predict the adsorption equilibrium of mixtures containing supercritical components was presented. The difference in the adsorption mechanism between the supercritical components and the condensable components was accounted for in the new model. Lateral interaction in the adsorbed phase was also considered in the local isotherm. The new model was verified by the experimental data of the mixture CH4/CO2/C2H6 on activated carbon JX101 collected for 283-313 K and pressures up to . It was also verified with the experimental data published previously in literature. Considerable improvement in the prediction precision was achieved in using the new model to predict the adsorption of mixtures on activated carbon.  相似文献   
995.
UHMWPE纤维/LDPE复合材料防弹性能及机理研究   总被引:9,自引:0,他引:9  
本文探讨了用超高分子量聚乙烯(UHMWPE)纤维增强低密度聚乙烯(LDPE)复合材料的防弹性能,研究了不同基体含量对复合材料防弹性能的影响。实验证明,UHMWPE纤维/LDPE复合材料具有较好的防弹性能,其最佳的基体含量在26%左右。同时,本文还通过分析防弹片材的断裂区域及复合材料的防弹机理确定了弹丸的变形情况和靶片“背凸”在防弹作用中的贡献。  相似文献   
996.
根据电除尘器绝缘子的功能及工况条件,介绍了材质和结构形式的选择。对于电除尘器绝缘子材质的选择,首先要考虑承受运行电压的能力,其次是耐温性能和机械强度。对于结构形式的选择,应考虑有足够的厚度以耐电力冲击、足够大的爬电距离以防漏电或对地闪络、足够大的空间以防出现电晕或空间闪络。另外,介绍了高铝瓷绝缘子的成功应用及其优点。  相似文献   
997.
High‐temperature vulcanized silicone rubber was prepared by using allyl‐capped carbosilane dendrimers, in which the core molecules were Si(CH2CH?CH2)4 and Ph2Si(CH2CH?CH2)2 as crosslinker and nanoscale reinforcing filler, respectively. Allyl‐capped carbosilane dendrimers improved the mechanical properties of silicone rubber. The optimum tensile strength and tear strength were 9.6 MPa and 31.0 kN/m, respectively, when using SiGn(allyl)m as the crosslinker and 10.1 MPa and 32.0 kN/m, respectively, when using Ph2SiGn(allyl)m as the crosslinker. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 1772–1775, 2006  相似文献   
998.
讨论了传统流变仪测量粘度上存在的问题,提出了改进的方案测量粘度,以减少误差。试验方案主要体现在用数码方法采集数据。  相似文献   
999.
The aim of this work is to develop a new compatibility for the uncertain multiplicative linguistic preference relations and utilize it to determine the optimal weights of experts in the group decision making (GDM). First, the compatibility degree and compatibility index for the two multiplicative linguistic preference relations are proposed. Then, based on the linguistic continuous ordered weighted geometric averaging (LCOWGA) operator, some concepts of the compatibility degree and compatibility index for the two uncertain multiplicative linguistic preference relations are presented. We prove the property that the synthetic uncertain linguistic preference relation is of acceptable compatibility under the condition that the uncertain multiplicative linguistic preference relations given by experts are all of acceptable compatibility with the ideal uncertain multiplicative linguistic preference relation, which provides a theoretic basis for the application of the uncertain multiplicative linguistic preference relations in GDM. Next, an optimal model is constructed to determine the weights of experts based on the criterion of minimizing the compatibility index in GDM. Moreover, an approach to GDM with uncertain multiplicative linguistic preference relations is developed, and finally, an application of the approach to supplier selection problem with uncertain multiplicative linguistic preference relations is pointed out.  相似文献   
1000.
As a recently proposed machine learning method, active learning of Gaussian processes can effectively use a small number of labeled examples to train a classifier, which in turn is used to select the most informative examples from unlabeled data for manual labeling. However, in the process of example selection, active learning usually need consider all the unlabeled data without exploiting the structural space connectivity among them. This will decrease the classification accuracy to some extent since the selected points may not be the most informative. To overcome this shortcoming, in this paper, we present a method which applies the manifold-preserving graph reduction (MPGR) algorithm to the traditional active learning method of Gaussian processes. MPGR is a simple and efficient example sparsification algorithm which can construct a subset to represent the global structure and simultaneously eliminate the influence of noisy points and outliers. Thereby, when actively selecting examples to label, we just choose from the subset constructed by MPGR instead of the whole unlabeled data. We report experimental results on multiple data sets which demonstrate that our method obtains better classification performance compared with the original active learning method of Gaussian processes.  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