全文获取类型
收费全文 | 1517481篇 |
免费 | 30373篇 |
国内免费 | 10721篇 |
专业分类
电工技术 | 33851篇 |
技术理论 | 14篇 |
综合类 | 11032篇 |
化学工业 | 232277篇 |
金属工艺 | 58548篇 |
机械仪表 | 48846篇 |
建筑科学 | 45583篇 |
矿业工程 | 11180篇 |
能源动力 | 40026篇 |
轻工业 | 123754篇 |
水利工程 | 16842篇 |
石油天然气 | 30528篇 |
武器工业 | 1362篇 |
无线电 | 168853篇 |
一般工业技术 | 279167篇 |
冶金工业 | 279577篇 |
原子能技术 | 28739篇 |
自动化技术 | 148396篇 |
出版年
2022年 | 12496篇 |
2021年 | 18068篇 |
2020年 | 13585篇 |
2019年 | 14934篇 |
2018年 | 22554篇 |
2017年 | 22865篇 |
2016年 | 23784篇 |
2015年 | 19272篇 |
2014年 | 28981篇 |
2013年 | 73135篇 |
2012年 | 44730篇 |
2011年 | 59026篇 |
2010年 | 47655篇 |
2009年 | 51858篇 |
2008年 | 53191篇 |
2007年 | 52515篇 |
2006年 | 46933篇 |
2005年 | 41997篇 |
2004年 | 38651篇 |
2003年 | 38095篇 |
2002年 | 36870篇 |
2001年 | 35543篇 |
2000年 | 33054篇 |
1999年 | 34466篇 |
1998年 | 80981篇 |
1997年 | 58145篇 |
1996年 | 45390篇 |
1995年 | 34567篇 |
1994年 | 30676篇 |
1993年 | 30143篇 |
1992年 | 22006篇 |
1991年 | 20613篇 |
1990年 | 20394篇 |
1989年 | 19855篇 |
1988年 | 18744篇 |
1987年 | 16773篇 |
1986年 | 16358篇 |
1985年 | 18846篇 |
1984年 | 17395篇 |
1983年 | 15784篇 |
1982年 | 14669篇 |
1981年 | 14922篇 |
1980年 | 14048篇 |
1979年 | 14004篇 |
1978年 | 13542篇 |
1977年 | 15940篇 |
1976年 | 21207篇 |
1975年 | 11926篇 |
1974年 | 11356篇 |
1973年 | 11405篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
41.
42.
On the effect of spatial variances in historical rainfall time series to CSO performance evaluation.
Historical, high-resolution rain series are the backbone of modern combined sewer overflow (CSO) structure design. These rain series are the input to the computational estimation of the performance of the measures with respect to CSO pollution abatement. However, those historical precipitation measurements are available at only a few locations. Frequently rain series have to be used from gauging stations at a significant distance. In order to judge and to compensate for this influence an estimate between rain characteristics and combined sewer outflow (CSO) performance indicators would be useful. In this paper such correlations have been sought for a collection of 37 rain series covering large areas of Europe. It was found that the mean annual rain volume can explain most of the variances for the performance indicators Number of overflows and CSO volume. For explaining the spatial differences in the efficiency of the CSO structure another rain characteristic, i.e. the maximum event with a return period of one year, is to be used. 相似文献
43.
H. L. Du S. R. Rose Z. D. Xiang P. K. Datta X. Y. Li 《Materialwissenschaft und Werkstofftechnik》2003,34(4):421-426
The oxidation/sulphidation behaviour of a Ti‐46.7Al‐1.9W‐0.5Si alloy with a TiAl3 diffusion coating was studied in an environment of H2/H2S/H2O at 850oC. The kinetic results demonstrate that the TiAl3 coating significantly increased the high temperature corrosion resistance of Ti‐46.7Al‐1.9W‐0.5Si. The SEM, EDX, XRD and TEM analysis reveals that the formation of an Al2O3 scale on the surface of the TiAl3‐coated sample was responsible for the enhancement of the corroison resistance. The Ti‐46.7Al‐1.9W‐0.5Si alloy was also modified by Nb ion implantation. The Nb ion implanted and as received sampels were subjected to cyclic oxidation in an open air at 800oC. The Nb ion implantation not only increased the oxidation resistance but also substantially improved the adhesion of scale to the substrate. 相似文献
44.
Nobel A.B. 《IEEE transactions on information theory / Professional Technical Group on Information Theory》2003,49(1):83-98
This paper considers several aspects of the sequential prediction problem for unbounded, nonstationary processes under pth power loss /spl lscr//sub p/(u,v)=|u-v|/sup p/, 1
相似文献
45.
Nucleation and growth mechanisms and kinetics of crystals of an amino acid salt were investigated in a methanol‐water system by measuring and evaluating the induction time as a function of the supersaturation ratio and temperature in batch salting out crystallization experiments. Discrimination between the possible crystallization mechanisms, and estimation of the kinetic parameters were carried out using nonlinear parameter identification. The results concerning the growth mechanism obtained were checked additionally by measuring the induction time as a function of number density of seed crystals. 相似文献
46.
47.
G. I. Glazov A. M. Garaiev R. V. Timerkhanov 《Chemistry and Technology of Fuels and Oils》2003,39(1-2):26-53
A series of small–capacity units has recently been constructed in regions of oil field development and crude oil and gas condensate production to satisfy the requirements for such petroleum products as naphtha, diesel fuel, kerosene, and boiler fuel and to reduce costs for delivery of these products. There are almost no data in the technical literature, particularly in periodicals, on the construction and operation of small–capacity units. We attempt to generalize the experience of Orgeneftekhimzavody Trust in this area. We hope that this experience will be useful to specialists in the development and management of small–capacity plants. 相似文献
48.
49.
Malcolm J. Beynon 《国际智能系统杂志》2006,21(2):173-191
The granularity of an information system has an incumbent effect on the efficacy of the analysis from many machine learning algorithms. An information system contains a universe of objects characterized and categorized by condition and decision attributes. To manage the concomitant granularity, a level of continuous value discretization (CVD) is often undertaken. In the case of the rough set theory (RST) methodology for object classification, the granularity contributes to the grouping of objects into condition classes with the same condition attribute values. This article exposits the effect of a level of CVD on the subsequent condition classes constructed, with the introduction of the condition class space—the domain within which the condition classes exist. This domain elucidates the association of the condition classes to the related decision outcomes—reflecting the inexactness incumbent when a level of CVD is undertaken. A series of measures is defined that quantify this association. Throughout this study and without loss of generality, the findings are made through the RST methodology. This further offers a novel exposition of the relationship between all the condition attributes and the RST‐related reducts (subsets of condition attributes). © 2006 Wiley Periodicals, Inc. Int J Int Syst 21: 173–191, 2006. 相似文献
50.
S Kim 《Water science and technology》2006,53(4-5):393-401
The unsteady flow analysis of pipeline systems provides useful guidelines for implementing data acquisition components such as data filtering ranges, sensor locations and sampling frequencies. A theoretical integration among hydraulics, free vibration analysis and signal processing is proposed for a comprehensive approach aiming at enhanced design and operation of data acquisition system. Transient analysis is performed to extract flow variation by a valve modulation in a pipeline system. Frequency transformation analysis is developed to convert pressure variations between time domain and frequency domain. Free vibration analysis provides spatial distribution of impedance characteristics and pressure variation for determining optimum sensor location. A real-time filter can be designed to secure valid signals of any particular unsteady event. Hypothetical and experimental applications show that the proposed method has potentials of the leakage detection of a pipeline system as well as an efficient design of data acquisition system. 相似文献