全文获取类型
收费全文 | 27394篇 |
免费 | 1964篇 |
国内免费 | 1236篇 |
专业分类
电工技术 | 732篇 |
综合类 | 1637篇 |
化学工业 | 2416篇 |
金属工艺 | 4098篇 |
机械仪表 | 1345篇 |
建筑科学 | 2930篇 |
矿业工程 | 437篇 |
能源动力 | 654篇 |
轻工业 | 3357篇 |
水利工程 | 170篇 |
石油天然气 | 457篇 |
武器工业 | 126篇 |
无线电 | 1449篇 |
一般工业技术 | 5380篇 |
冶金工业 | 4055篇 |
原子能技术 | 148篇 |
自动化技术 | 1203篇 |
出版年
2024年 | 173篇 |
2023年 | 456篇 |
2022年 | 732篇 |
2021年 | 921篇 |
2020年 | 871篇 |
2019年 | 693篇 |
2018年 | 673篇 |
2017年 | 960篇 |
2016年 | 892篇 |
2015年 | 820篇 |
2014年 | 1762篇 |
2013年 | 1555篇 |
2012年 | 2069篇 |
2011年 | 2207篇 |
2010年 | 1580篇 |
2009年 | 1765篇 |
2008年 | 1212篇 |
2007年 | 1706篇 |
2006年 | 1634篇 |
2005年 | 1268篇 |
2004年 | 1108篇 |
2003年 | 876篇 |
2002年 | 876篇 |
2001年 | 724篇 |
2000年 | 579篇 |
1999年 | 468篇 |
1998年 | 364篇 |
1997年 | 336篇 |
1996年 | 261篇 |
1995年 | 208篇 |
1994年 | 155篇 |
1993年 | 156篇 |
1992年 | 139篇 |
1991年 | 91篇 |
1990年 | 78篇 |
1989年 | 101篇 |
1988年 | 36篇 |
1987年 | 20篇 |
1986年 | 10篇 |
1985年 | 6篇 |
1984年 | 13篇 |
1983年 | 3篇 |
1982年 | 7篇 |
1980年 | 10篇 |
1979年 | 4篇 |
1978年 | 3篇 |
1975年 | 3篇 |
1962年 | 1篇 |
1961年 | 1篇 |
1959年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 593 毫秒
21.
22.
23.
24.
Plastic encapsulated microcircuits (PEMs) are increasingly being used in applications requiring operation at temperatures lower than the manufacturer’s recommended minimum temperature, which is 0°C for commercial grade components and −40°C for industrial and automotive grade components. To characterize the susceptibility of PEMs to delamination at these extreme low temperatures, packages with different geometries, encapsulated in both biphenyl and novolac molding compounds, were subjected to up to 500 thermal cycles with minimum temperatures in the range −40 to −65°C in both the moisture saturated and baked conditions. Scanning acoustic microscopy revealed there was a negligible increase in delamination at the die-to-encapsulant interface after thermal cycling for the 84 lead PQFPs encapsulated in novolac and for both 84 lead PQFPs and 14 lead PDIPs encapsulated in biphenyl molding compound. Only the 14 lead novolac PDIPs exhibited increased delamination. Moisture exposure had a significant effect on the creation of additional delamination. 相似文献
25.
随着集成电路技术的发展及计算机性能的不断提高,计算机组装结构设计在计算机,总体设计中的地位越来越重要,它直接影响到计算机性能的提高。本文针对一个基于工作站和EUCLID-IS软件的电子计算机组结构CAD系统,从软、硬件平台,系统功能及实现等方面进行了讨论,旨在为电子计算机组装结构设计提供一种强有力的、方便的设计工具,有利于增强国产计算机的市场竞争能力。 相似文献
26.
随着集成电路技术的发展及计算机性能的不断提高,计算机组装结构设计在计算机,总体设计中的地位越来越重要,它直接影响到计算机性能的提高。本文针对一个基于工作站和EUCLID-IS软件的电子计算机组结构CAD系统,从软、硬件平台,系统功能及实现等方面进行了讨论,旨在为电子计算机组装结构设计提供一种强有力的、方便的设计工具,有利于增强国产计算机的市场竞争能力。 相似文献
27.
Steel box sections are usually fabricated from flat plates which are welded at the corners. The welding process can introduce residual stresses and geometric imperfections into the sections which can influence their strength. For some thin-walled sections, large periodic geometric imperfections have been observed in manufactured sections. Subsequent investigations have indicated that the imperfections are in fact buckling deformations i.e. the box section has buckled due to welding residual stresses prior to any application of external load. The welding procedure and the behaviour of the box sections under load has been modelled using a finite element analysis that accounts for both geometric and material non-linearities. Tests have been carried out on box sections with a range of width to thickness ratios for the plate elements. Modelling has been shown to give good correlation with the test results. The conditions for buckling to take place as a result of the welding process have been established. A design method has been proposed. 相似文献
28.
29.
ABSTRACT: The traditional small-scale production of boucané, a cured smoked pork-belly product from Réunion, involves several unit operations that are performed in a single step. The aim of this study was to highligh the impact of 4 unit operations (salting, drying, cooking, and smoking) on stability, color, and flavor development in processed pork. These characateristics are the 3 main criteria of boucané's quality. Mass transfer, color, and volatile compounds were measured, analyzed, and compared in 4 products. Results indicated that a major quantity of volatile compounds detected in the processed meat were derived from the smoking process. Color variations were mainly explained by muscle pigment modification due to the cooking process, and by the input of volatile compounds of smoke. 相似文献
30.