首页 | 官方网站   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   29216篇
  免费   6376篇
  国内免费   5148篇
工业技术   40740篇
  2024年   208篇
  2023年   754篇
  2022年   1138篇
  2021年   1263篇
  2020年   1498篇
  2019年   1377篇
  2018年   1286篇
  2017年   1478篇
  2016年   1602篇
  2015年   1778篇
  2014年   2212篇
  2013年   2363篇
  2012年   2615篇
  2011年   2817篇
  2010年   2165篇
  2009年   2157篇
  2008年   2248篇
  2007年   2304篇
  2006年   1874篇
  2005年   1479篇
  2004年   1171篇
  2003年   927篇
  2002年   721篇
  2001年   594篇
  2000年   494篇
  1999年   392篇
  1998年   319篇
  1997年   281篇
  1996年   238篇
  1995年   178篇
  1994年   145篇
  1993年   138篇
  1992年   114篇
  1991年   77篇
  1990年   72篇
  1989年   60篇
  1988年   37篇
  1987年   18篇
  1986年   11篇
  1985年   14篇
  1984年   32篇
  1983年   19篇
  1982年   9篇
  1981年   11篇
  1980年   9篇
  1979年   8篇
  1978年   6篇
  1977年   7篇
  1960年   3篇
  1959年   4篇
排序方式: 共有10000条查询结果,搜索用时 234 毫秒
71.
This paper finds the appropriate pi-coefficients for a parameter estimation adaptive system and uses them to analyze the stability of two estimation algorithms. The estimation error dynamics of the system are modeled by a linear time-invariant subsystem and a nonlinear time-varying update law in a feedback loop. Then the so-called max-p problems are formulated and solved to obtain the pi-coefficients for the linear subsystem and nonlinear update low. For the investigated system, the quantitative results show that the least-squares update algorithm has larger stability range than that of the gradient algorithm, and the σ-modification scheme gives larger stability ranges for both algorithms.  相似文献   
72.
73.
1IntroductionAutomaticparallelexecutionofdeclarativelanguageprograms(e.g.functionprogramsandlogicprograms)isattractive,asitmakestheuseofparallelcomputersveryeasy,andtheprogrammerneednotbeconcernedwiththespecificsoftheunderlyingparallelarchitecture.However,ifseveralprocessorsareexecutingconcurrently,exploitingadaptiveparallelismishardduetonon-determinismoftaskgranularityanddatadependenciesamongtasks.TheearlysolutionproposedbyConeryandKibler[2]usesanorderingalgorithmtodeterminedependenciesatrun…  相似文献   
74.
The conventional way of solving the group technology (GT) problem is to start from an assignment of parts to machines and try to find a partitioning of machine cells and part families. The similarity between parts is measured based on commonality of the machines assigned to them. However, parts are assigned to machines based on their operation requirements and the operation capabilities of machines. Similarity between parts should be based on their required operations. In this paper, the authors attempt to solve or facilitate solving the GT problem at the assignment level. An algorithm for assigning parts to machines is provided which utilizes the types of operations required by parts and applies GT principles in producing the assignment. This leads to better partitioning of machine cells and part-families. Furthermore, operation sequences required by parts in determining the similarity between parts have been considered. An algorithm to form part-families based on the operation sequence similarity coefficient has been developed. The resulting families are then used by the assignment algorithm to produce machine assignments to part-families. The use of the algorithm is demonstrated by examples.  相似文献   
75.
This paper describes an approach, conceptual framework, and software architecture for dynamic reconfiguration of the order picking system. The research and development project was sponsored by the Material Handling Research Center (MHRC), a National Science Foundation sponsored Cooperative Industry/University Research Center. The storage configuration is assumed to be an in-the-aisle order picking system in which stockkeeping units (SKUs) can occupy variable capacity storage locations and stock-splitting is allowed among zones (clusters). The product mix may include multiple product families with different life cycles, correlated demand within families and commonality of demand across families.  相似文献   
76.
水文相似度及其应用   总被引:6,自引:0,他引:6  
本文分别从流域下垫面、河网发育情况、产汇流影响因素的角度,探索性的提出了几个水文相似性评定指标,并采用层次分析法计算每种水文相似性指标在计算水文相似程度中的权重。以江西雨量站网密度实验区中的朗口和银山流域为研究对象,实例计算了两个流域的水文相似程度,结果证明水文相似度有助于定量化研究水文相似性问题。  相似文献   
77.
正交频分多址(OFDM:orthogonal frequency division multiplexing)技术由于其在多径环境下克服码间干扰的固有特点,在移动通信中已得到广泛地应用。利用阵列天线上行链路信号到达角估计实时信息,计算OFDM系统下行链路阵列天线权重,将阵列天线应用于下行链路中,最后给出系统误码率性能的计算机仿真结果。  相似文献   
78.
非理想信道下Colpitts混沌电路的自适应同步研究   总被引:1,自引:0,他引:1  
本文研究了Colpitts混沌电路在非理想信道条件下的自适应同步问题。引入自适应控制器对输入到响应部分(response system)的衰变混沌信号进行预处理,来补偿衰落信道对于同步性能的影响。给出了系统的数学模型,对恒定信道衰变和时变信道衰变两种非理想信道条件下的混沌ColpiRs电路的自适应同步进行了数值仿真研究。仿真结果表明,对于恒定或慢变化的时变信道衰变,自适应控制器可以有效的提高Colpitts电路响应部分和驱动部分(Drive system)的同步性能。  相似文献   
79.
区域内旱情监测站点的布设研究   总被引:4,自引:0,他引:4  
孙凯  王一鸣  杨绍辉  高福栋 《水利学报》2005,36(2):0208-0213
本文对北京通州辖区范围内组织的大规模的土壤墒情调查数据进行总结。基于地理统计、空间分析以及统计学知识,分析了北京通州旱情分布形势。运用数值分类学的知识对测量数据进行了聚类分析,同时用DB(DaviesBouldin)指标准则研究了区域内合理布设旱情监测站的数量及位置,为建立旱情监测站点提供了理论依据。  相似文献   
80.
We address the problems of noise and huge data sizes in microarray images. First, we propose a mixture model for describing the statistical and structural properties of microarray images. Then, based on the microarray image model, we present methods for denoising and for compressing microarray images. The denoising method is based on a variant of the translation-invariant wavelet transform. The compression method introduces the notion of approximate contexts (rather than traditional exact contexts) in modeling the symbol probabilities in a microarray image. This inexact context modeling approach is important in dealing with the noisy nature of microarray images. Using the proposed denoising and compression methods, we describe a near-lossless compression scheme suitable for microarray images. Results on both denoising and compression are included, which show the performance of the proposed methods. Further experiments using the results of the proposed near-lossless compression scheme in gene clustering using cell-cycle microarray data for S. cerevisiae showed a general improvement in the clustering performance, when compared with using the original data. This provides an indirect validation of the effectiveness of the proposed denoising method.  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-23

京公网安备 11010802026262号