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   19644篇
  免费   245篇
  国内免费   17篇
电工技术   221篇
综合类   8篇
化学工业   3477篇
金属工艺   321篇
机械仪表   377篇
建筑科学   932篇
矿业工程   38篇
能源动力   503篇
轻工业   1654篇
水利工程   211篇
石油天然气   64篇
无线电   1754篇
一般工业技术   3371篇
冶金工业   4289篇
原子能技术   120篇
自动化技术   2566篇
  2024年   114篇
  2023年   112篇
  2022年   181篇
  2021年   300篇
  2020年   305篇
  2019年   335篇
  2018年   309篇
  2017年   312篇
  2016年   383篇
  2015年   306篇
  2014年   449篇
  2013年   1059篇
  2012年   735篇
  2011年   1066篇
  2010年   687篇
  2009年   679篇
  2008年   847篇
  2007年   753篇
  2006年   638篇
  2005年   605篇
  2004年   584篇
  2003年   546篇
  2002年   494篇
  2001年   357篇
  2000年   327篇
  1999年   367篇
  1998年   954篇
  1997年   661篇
  1996年   495篇
  1995年   391篇
  1994年   336篇
  1993年   363篇
  1992年   239篇
  1991年   194篇
  1990年   218篇
  1989年   188篇
  1988年   164篇
  1987年   188篇
  1986年   168篇
  1985年   190篇
  1984年   160篇
  1983年   178篇
  1982年   173篇
  1981年   153篇
  1980年   133篇
  1979年   134篇
  1978年   119篇
  1977年   151篇
  1976年   258篇
  1975年   120篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
Currently there are design barriers inhibiting the implementation of high-precision digital signal processing (DSP) objects with field programmable logic (FPL) devices. This paper explores overcoming these barriers by fusing together the popular distributed arithmetic (DA) method with the residue number system (RNS) for use in FPL-centric designs. The new design paradigm is studied in the context of a high-performance filter bank and a discrete wavelet transform (DWT). The proposed design paradigm is facilitated by a new RNS accumulator structure based on a carry save adder (CSA). The reported methodology also introduces a polyphase filter structure that results in a reduced look-up table (LUT) budget. The 2C-DA and RNS-DA are compared, in the context of a FPL implementation strategy, using a discrete wavelet transform (DWT) filter bank as a common design theme. The results show that the RNS-DA, compared to a traditional 2C-DA design, enjoys a performance advantage that increases with precision (wordlength).  相似文献   
2.
Fuzzy logic was first suggested as the mechanism by which humans drive cars. This paper addresses the use of fuzzy logic and algorithms towards the intelligent autonomous motion control of land vehicles. To cope with vehicle complexities, internal parametric changes, and with unpredictable environmental effects, the controllers that are presented, whilst heuristic in nature, are self-organizing or self-learning in that they generate automatically by observation an experiential rule base that models the vehicle, and via an appropriate performance index an optimal control rule base that is robust to large parametric changes. The methodology presented is applicable to any complex process which is too difficult to model or control using conventional methods, or which has relied on the experience of a human operator. An overview of fuzzy logic and static fuzzy logic control (akin to expert systems) is provided, together with illustrative examples.  相似文献   
3.
Power distribution systems have been significantly affected by many outage-causing events. Good fault cause identification can help expedite the restoration procedure and improve the system reliability. However, the data imbalance issue in many real-world data sets often degrades the fault cause identification performance. In this paper, the E-algorithm, which is extended from the fuzzy classification algorithm by Ishibuchi to alleviate the effect of imbalanced data constitution, is applied to Duke Energy outage data for distribution fault cause identification. Three major outage causes (tree, animal, and lightning) are used as prototypes. The performance of E-algorithm on real-world imbalanced data is compared with artificial neural network. The results show that the E-algorithm can greatly improve the performance when the data are imbalanced  相似文献   
4.
The authors highlight several possible ways in which the construction industry could lower present emissions of the greenhouse gas, carbon dioxide. It is an excellent discussion document and is recommended reading.  相似文献   
5.
Methyl groups from chain scission and H-crosslinks have been identified by solid-state nuclear magnetic resonance in amorphous ethylene-propylene copolymers containing 23 and 36 mole % propylene after γ-irradiation to 10 MGy at 30°C. G (scission) and G (crosslink) values determined from the n.m.r. spectra and by extraction are in agreement, which suggests that the crosslinks are not clustered. This may differ from the situation in polyethylene where there is a substantial crystalline content. G(S). G(X) and the ratio G(S)/G(X) increase with increasing propylene content of the copolymers.  相似文献   
6.
7.
Recent research suggests that implementing information systems presents considerable difficulties and that many implementations are total or partial failures. This paper argues that what both practitioners and students require are richer and more acceptable models of information systems implementation. Accordingly, case study data concerning the introduction of manufacturing resource planning (MRP II) are used to illustrate five patterns of behaviour (rites) which capture important social actions; and four components of changing psychological orientation. It is argued that appreciation of the rites and psychological developments identified here will support effective change programmes. Guidelines based on our model are provided for practitioners.  相似文献   
8.
To examine the separate effects of viscosity and sweetness on astringency, aqueous solutions of grape seed tannin (GST) were thickened with carboxymethyl cellulose (CMC) from 2 to 45 cP (experiment 1) or sweetened with 0 to 1.8 g/L aspartame (experiment 2). Trained subjects continuously rated astringency and bitterness in duplicate. Subjects were categorized by the salivary flow induced by citric acid and ability to taste n-propyl thiouracil (PROP). In experiment 1, maximum intensity and total duration of astringency were significantly decreased as viscosity rose, although time to maximum intensity of astringency was not affected. Maximum intensity and total duration of bitterness were not significantly affected by increasing viscosity; however, the onset of bitterness was significantly delayed. In experiment 2, increasing sweetness had no affect on any astringency parameter, although maximum intensity of bitterness was significantly decreased. Neither PROP nor salivary flow-status had any effect on perception of bitterness or astringency in either experiment.  相似文献   
9.
Results of tests undertaken to identify which measures of seated posture control are most effective in two areas, distinguishing differences in the x and y direction control strategies for a given task and distinguishing differences in overall control strategies for pairs of different tasks, are presented. The test platform, calibration tests, test protocol, and data analysis method are described. The results of statistical analyses performed on the data are summarized  相似文献   
10.
The design and evaluation of an optically triggered, fully integrated sample and hold circuit (OS/H) is described. Measured results are presented that demonstrate operation of this circuit at 250 Ms/s and with effective resolution approaching 8 bits. The integrated circuit, which measures 2.1 mm×1.4 mm, is realized in -1.0-V threshold, 20-GHz ft GaAs MESFET technology, consumes approximately 200 mW of power, and requires one optical address. The OS/H will find applications in high precision, hybrid, and integrated signal processing systems where high speed, high levels of parallelism, and low timing jitter are important. Measured results of a series photoconducting (Auston switch) OS/H realized in the same technology are presented for comparison purposes  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