全文获取类型
收费全文 | 58426篇 |
免费 | 8021篇 |
国内免费 | 5284篇 |
专业分类
电工技术 | 5916篇 |
技术理论 | 3篇 |
综合类 | 6153篇 |
化学工业 | 4555篇 |
金属工艺 | 1327篇 |
机械仪表 | 2909篇 |
建筑科学 | 5457篇 |
矿业工程 | 1810篇 |
能源动力 | 1386篇 |
轻工业 | 2640篇 |
水利工程 | 1418篇 |
石油天然气 | 2376篇 |
武器工业 | 738篇 |
无线电 | 7372篇 |
一般工业技术 | 4810篇 |
冶金工业 | 2063篇 |
原子能技术 | 650篇 |
自动化技术 | 20148篇 |
出版年
2024年 | 348篇 |
2023年 | 1004篇 |
2022年 | 1867篇 |
2021年 | 2182篇 |
2020年 | 2406篇 |
2019年 | 2090篇 |
2018年 | 1878篇 |
2017年 | 2335篇 |
2016年 | 2500篇 |
2015年 | 2686篇 |
2014年 | 3761篇 |
2013年 | 3946篇 |
2012年 | 4281篇 |
2011年 | 4531篇 |
2010年 | 3409篇 |
2009年 | 3551篇 |
2008年 | 3438篇 |
2007年 | 4003篇 |
2006年 | 3531篇 |
2005年 | 2957篇 |
2004年 | 2398篇 |
2003年 | 2183篇 |
2002年 | 1931篇 |
2001年 | 1576篇 |
2000年 | 1356篇 |
1999年 | 1037篇 |
1998年 | 805篇 |
1997年 | 680篇 |
1996年 | 553篇 |
1995年 | 459篇 |
1994年 | 379篇 |
1993年 | 293篇 |
1992年 | 198篇 |
1991年 | 185篇 |
1990年 | 137篇 |
1989年 | 114篇 |
1988年 | 87篇 |
1987年 | 80篇 |
1986年 | 68篇 |
1985年 | 71篇 |
1984年 | 58篇 |
1983年 | 52篇 |
1982年 | 42篇 |
1981年 | 41篇 |
1980年 | 39篇 |
1979年 | 29篇 |
1978年 | 21篇 |
1977年 | 17篇 |
1964年 | 13篇 |
1955年 | 12篇 |
排序方式: 共有10000条查询结果,搜索用时 10 毫秒
11.
During the 1997 winter season, shipborne polarimetric backscatter measurements of Great Lakes (freshwater) ice types using the Jet Propulsion Laboratory C-band scatterometer, together with surface-based ice physical characterization measurements and environmental parameters, were acquired concurrently with Earth Resource Satellite 2 (ERS-2) and RADARSAT Synthetic Aperture Radar (SAR) data. This polarimetric data set, composed of over 20 variations of different ice types measured at incident angles from 0° to 60° for all polarizations, was processed to radar cross-section to establish a library of signatures (look-up table) for different ice types. The library is used in the computer classification of calibrated satellite SAR data. Computer analysis of ERS-2 and RADARSAT ScanSAR images of Great Lakes ice cover using a supervised classification technique indicates that different ice types in the ice cover can be identified and mapped, and that wind speed and direction can have an influence on the classification of water as ice based on single frequency, single polarization data. Once satellite SAR data are classified into ice types, the ice map provides important and necessary input for environmental protection and management, ice control and ice breaking operations, and ice forecasting and modeling efforts. 相似文献
12.
NUMERICAL ANALYSIS AND EXPERI- MENT OF UNSTEADY THERMAL FIELD OF ROTOR PLATE FOR EDDY CURRENT RETARDER 总被引:3,自引:0,他引:3
LIU Chengye HE Ren 《机械工程学报(英文版)》2008,21(4):71-75
The physical model based on heat transfer theory and virtual boundary method for analyzing unsteady thermal field of rotor plate for eddy current retarder used in automobile is established and boundary conditions are also defined. The finite element governing equation is derived by Galerkin method. The time differential item is discrete based on Galerkin format that is stable at any condition. And a new style of varying time step method is used in iteration process. The thermal field on the rotor plate at the radial and axle directions is analyzed and varying temperature at appointed points on two side-surfaces is measured. The testing and analytical data are uniform approximately. Finite element method can be used for estimating thermal field of the rotor plate at initial design stage of eddy current retarder. 相似文献
13.
企业实施精益生产的探讨 总被引:1,自引:0,他引:1
通过描述造成企业经济效益差的原因之一——浪费,提出了如何实施精益生产,消除企业浪费,以提高企业经济效益. 相似文献
14.
It is necessary to determine the accurate reflectance of painted surfaces for the review of paint finishes by computer graphics (CG) before actual painting of the exterior color of automobiles, and for quality control during production and inspection processes. We have optimized a method for measuring reflectance by using a statistical technique. We have found that the reflectance of a painted surface is best measured at an incident angle of 60° and at five aspecular angles of 10°, 18°, 28°, 40°, and 90°. Our method makes it possible to accurately reproduce reflection characteristics of paint finishes containing special flake pigments, such as pearl mica. Also it was proved that our method can apply not only to solid and metallic coatings but to all painted surfaces. © 2005 Wiley Periodicals, Inc. Col Res Appl, 30, 275–282, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/col.20125 相似文献
15.
16.
李毅 《核电子学与探测技术》1995,15(3):184-188
多丝正比室中电子的最大漂移时间是逃逸门电路中的一个重要参数。这个参数的选择将影响逃逸门工作方式的多丝正比室的整体性能。通过实验测量得到了多丝正比室中电子的最大漂移时间的实际值和最大漂移时间随多丝正比室工作状态的变化,测量结果在实际中得到应用。 相似文献
17.
Adrian Thomas Christopher D. Gilson Tanveer Ahmed 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1995,64(1):73-79
Equipment was developed to measure the time for complete gelling of sodium alginate fibres in calcium chloride solution, taken as the time to achieve maximum tensile strength. The effects of fibre diameter, alginate concentration, alginate composition and calcium chloride concentration on gelling time were investigated. A diffusional model, developed to predict the gelling time, agreed with experimental results except for the effect of calcium ion concentration which was modelled empirically. 相似文献
18.
Wood has long traditions as a building material, and is often used in construction elements, and as interior and exterior surfaces in the Nordic countries. In most applications, there are reaction to fire requirements to products used as surfaces, e.g. in escape routes and larger public spaces. Most wood products will therefore have to be treated with fire retardant (FR) agents to fulfil the strict requirements to properties connected to heat release and flame spread. Unfortunately, FR agents usually also increase the smoke production, as they cause a more incomplete combustion of the wood. The wood product manufacturers seek to find the optimal amount of FR additives where both heat release and smoke production in the classifying test are within the requirements given in the building regulations. This paper describes models for prediction of the European reaction to fire classes of wood products. The models are based on multivariate statistical analysis, and use test results from the cone calorimeter test as input. The presented models are, with very good precision, able to predict which Euroclass and additional smoke class a wood based product would obtain if it were to be tested in the single burning item test. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
19.
20.
本文介绍单光子时间分辨在线谱仪系统中的多道分析器与IBM PC/XT微型计算机接口的工作原理及控制程序。 相似文献