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   30987篇
  免费   1848篇
  国内免费   32篇
电工技术   205篇
综合类   13篇
化学工业   6990篇
金属工艺   560篇
机械仪表   690篇
建筑科学   961篇
矿业工程   59篇
能源动力   623篇
轻工业   5853篇
水利工程   336篇
石油天然气   142篇
武器工业   2篇
无线电   1210篇
一般工业技术   5089篇
冶金工业   5881篇
原子能技术   114篇
自动化技术   4139篇
  2024年   70篇
  2023年   315篇
  2022年   415篇
  2021年   895篇
  2020年   739篇
  2019年   762篇
  2018年   1361篇
  2017年   1305篇
  2016年   1408篇
  2015年   1053篇
  2014年   1341篇
  2013年   2567篇
  2012年   1943篇
  2011年   1835篇
  2010年   1450篇
  2009年   1284篇
  2008年   1314篇
  2007年   1202篇
  2006年   800篇
  2005年   660篇
  2004年   632篇
  2003年   585篇
  2002年   505篇
  2001年   376篇
  2000年   334篇
  1999年   370篇
  1998年   2029篇
  1997年   1316篇
  1996年   827篇
  1995年   456篇
  1994年   354篇
  1993年   377篇
  1992年   119篇
  1991年   99篇
  1990年   83篇
  1989年   84篇
  1988年   103篇
  1987年   94篇
  1986年   89篇
  1985年   108篇
  1984年   81篇
  1983年   64篇
  1982年   70篇
  1981年   88篇
  1980年   89篇
  1979年   53篇
  1977年   144篇
  1976年   273篇
  1975年   53篇
  1973年   55篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
A photoacoustic (PA) methodology, in the transmission configuration, for simultaneous measurements of thermal effusivity and molar absorption coefficient (absorptivity) for pigments in liquid solution is introduced. The analytical treatment involves a self-normalization procedure for the PA signal, as a function of the modulation frequency, for a strong absorbing material in the thermally thin regime, when the light travels across the sample under study. Two fitted parameters are obtained from the analysis of the self-normalized PA amplitude and phase, one of them proportional to the sample's optical absorption coefficient and from which, taking it for a series of samples at different concentrations, the pigment's absorptivity in liquid solution can be measured, the other one yields the sample's thermal effusivity. Methylene blue's absorptivity in distilled water was measured with this methodology at 658 nm, finding good agreement with the corresponding one reported in the literature.  相似文献   
72.
This paper describes a novel model for fetal heart rate (FHR) monitoring from single-lead mother?s abdomen ECG (AECG) measurements. This novel method is divided in two stages: the first step consists on a one-step wavelet-based preprocessing for simultaneous baseline and high-frequency noise suppression, while the second stage efficiently detects fetal QRS complexes allowing FHR monitoring. The presented structure has been simplified as much as possible, in order to reduce computational cost and thus enable possible custom hardware implementations. Moreover, the proposed scheme and its fixed-point modeling have been tested using real abdominal ECG signals, which allow the validation of the presented approach and provide high accuracy.  相似文献   
73.
ABSTRACT

This exhibition review focuses on the quest for weaving boundaries between body-form-space-and material relationship using immersive technologies. Emerging as an architectural counterpoint, Universal Everything: Fluid Bodies exhibition held in Borusan Contemporary focuses on how we perceive the motion and form in relation to it, as well as fusing senses of kinaesthetic and synaesthetic through a data driven and motion-based visual representation. Through these algorithms, the exhibition displays how neuroarchitecture reminds us of the senses of perception. The architectural counterpoint, intention as an interaction and encounter of the body with ‘the machine’ as the ‘voyeur body’ and how this observational dialogue becomes a research methodology in understanding the nature of movement in space through digital tools.  相似文献   
74.
In this paper we study the coordination of different activities in a supply chain issued from a real case. Multiple suppliers send raw materials (RMs) to a distribution center (DC) that delivers them to a unique plant where the storage of the RMs and the finished goods is not possible. Then, the finished goods are directly shipped to multiple customers having just‐in‐time (JIT) demands. Under these hypotheses, we show that the problem can be reduced to multiple suppliers and one DC. Afterwards, we analyze two cases; in the first, we consider an uncapacitated storage at DC, and in the second, we analyze the capacitated storage case. For the first case, we show that the problem is NP‐hard in the ordinary sense using the Knapsack decision problem. We then propose two exact methods: a mixed integer linear program (MILP) and a pseudopolynomial dynamic program. A classical dynamic program and an improved one using the idea of Shaw and Wagelmans are given. With numerical tests we show that the dynamic program gives the optimal solution in reasonable time for quite large instances compared with the MILP. For the second case, the capacity limitation in DC is assumed, which makes the problem solving more challenging. We propose an MILP and a dynamic programming‐based heuristic that provides solutions close to the optimal solution in very short times.  相似文献   
75.
FALGOL (Formal ALGOrithmic Language) is a fundamental theoretical model of high-level operational languages with unrestricted program object hierarchy. This model formalizes binding, assignment, substitution, and recursion; moreover, the principle of dynamic binding is implemented in the model in contrast to other formal systems of this sort, which makes FALGOL appropriate to specify the most difficultly formalized concepts in modern object programming languages.  相似文献   
76.
Phosphofructokinase purified from mantle tissue of the sea mussel Mytilus galloprovincialis, was phosphorylated "in vitro" by the catalytic subunit of cyclic AMP-dependent protein kinase. The incorporation of phosphate gave rise to an activation of the enzyme by increasing its affinity for fructose-6-phosphate, by decreasing its sensitivity to the inhibition by ATP and by enhancing the effect of allosteric activators (5'-AMP and fructose-2,6-bisphosphate). In addition, the effects of phosphorylation on the catalytic activity are pH-dependent.  相似文献   
77.
A novel complex formed by ruthenium (III) and the sequestering ligand 1,2-propylenediaminetetraacetic acid (PDTA) has been synthetized and characterized. The structure of the monomeric compound, studied by X-ray diffraction , shows an almost symmetric octahedral geometry around the metal ion, with two chlorine atoms in a cis conformation. The antitumour activity against a variety of murine and human cancers is reported.  相似文献   
78.
The Journal of Supercomputing - CMOS technology is facing physical limitations in scaling the manufacturing process. Therefore, to deepen the development of better designs in a smaller area, it is...  相似文献   
79.
80.
García J  Mas D  Dorsch RG 《Applied optics》1996,35(35):7013-7018
A method for the calculation of the fractional Fourier transform (FRT) by means of the fast Fourier transform (FFT) algorithm is presented. The process involves mainly two FFT's in cascade; thus the process has the same complexity as this algorithm. The method is valid for fractional orders varying from -1 to 1. Scaling factors for the FRT and Fresnel diffraction when calculated through the FFT are discussed.  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