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   253668篇
  免费   16341篇
  国内免费   9160篇
电工技术   12371篇
技术理论   3篇
综合类   14242篇
化学工业   37395篇
金属工艺   14726篇
机械仪表   13838篇
建筑科学   15604篇
矿业工程   5269篇
能源动力   5848篇
轻工业   15863篇
水利工程   4827篇
石油天然气   8439篇
武器工业   1532篇
无线电   30650篇
一般工业技术   36120篇
冶金工业   10710篇
原子能技术   2224篇
自动化技术   49508篇
  2024年   741篇
  2023年   2510篇
  2022年   5054篇
  2021年   6908篇
  2020年   5019篇
  2019年   4129篇
  2018年   18473篇
  2017年   18250篇
  2016年   14428篇
  2015年   7588篇
  2014年   9007篇
  2013年   11026篇
  2012年   14984篇
  2011年   22223篇
  2010年   19760篇
  2009年   16813篇
  2008年   17721篇
  2007年   18344篇
  2006年   10154篇
  2005年   9595篇
  2004年   6763篇
  2003年   5861篇
  2002年   5105篇
  2001年   4061篇
  2000年   3729篇
  1999年   3551篇
  1998年   2928篇
  1997年   2542篇
  1996年   2264篇
  1995年   1853篇
  1994年   1475篇
  1993年   1172篇
  1992年   925篇
  1991年   728篇
  1990年   581篇
  1989年   470篇
  1988年   391篇
  1987年   265篇
  1986年   224篇
  1985年   172篇
  1984年   132篇
  1983年   88篇
  1982年   91篇
  1981年   73篇
  1980年   71篇
  1976年   61篇
  1968年   50篇
  1965年   45篇
  1955年   63篇
  1954年   68篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
11.
12.
This study empirically examined the organisational learning effects of the nonfinancial performance information provided by management accounting information systems (MAISs) under advanced manufacturing technology (AMT). In this study, a target costing system and the frequent and quick reporting of information were considered the facilitators of learning. First, we examined the relationships between AMT level and the amount of nonfinancial performance information produced by MAISs. The empirical results showed that there are significant positive relationships between the level of AMT and nonfinancial performance information. With a systems approach, we also proved the impact of the relationships among AMT levels, nonfinancial performance information and learning facilitators on the organisational performance of a firm. The results of our research suggest that under a high level of AMT, for the provision of information to result in an increase of performance through organisational learning, a target costing system must be introduced and a large amount of information should be provided frequently and quickly. The results of this study also showed that although AMT level may be low, fairly well-arranged facilitators and a moderately large amount of information may be necessary for the improvement of performance. In conclusion, effective organisational learning depends on the provision of relevant information as well as efficient learning support mechanisms.  相似文献   
13.
14.
基于DICOM标准全方向M型心动图的软件系统设计   总被引:3,自引:0,他引:3  
本文介绍了基于DICOM标准全方向M型心动图软件系统的设计方案,详细分析了系统结构及各个模块功能.通过该系统可以直接准确地定量检测分析心脏各结构的舒、缩、形变过程及其数据,同时可以生成多个任意方向且互相同步的M型心动图.各个模块设计完全遵循DICOM标准,同时结合数据库管理,方便查询索引.该系统分析的影像数据可以来自PACS服务器,也可以来自本地系统,分析结果数据可以回传PACS服务器,也可以保存本地.该系统实现了国家发明专利"全方向M型心动图方法及其系统98 125713.5"系统数据和国际医学图像传递标准的接口.  相似文献   
15.
The hot blow forming of magnesium sheet offers significant opportunity for forming complex, lightweight parts for automotive applications. This paper characterizes the elevated-temperature formability of AZ31 magnesium sheet materials and the effect of processing conditions on the performance of these materials. In addition, magnesium sheet application development at General Motors Corporation is reviewed.  相似文献   
16.
Strength of ground ceramics may be affected by residual stress as well as surface flaws induced by grinding. Strength prediction for ground ceramics is convenient for mechanical design of ceramic components. In this article, a numerical procedure based on fracture mechanics was proposed to estimate strength distribution of ground ceramics by considering grinding-induced residual stress. Bending strength and residual stress of ground ceramics were measured for three grinding-conditions. By comparison of simulated results with experimental ones, it was revealed that strength characteristics in experiments were well simulated by using the proposed procedure.  相似文献   
17.
Carboxyl‐terminated butadiene‐acrylonitrile rubber (CTBN) has often been used to improve the toughness of cyanate ester (CE) resin while sacrificing modulus and thermostability. In this paper, the addition of the appropriate amount of epoxy resin (EP) to the CE/CTBN system is shown to not only increase the modulus and thermostability of the blend, but also improve the toughness. The values of impact strength showed a maximum for the CE/CTBN/EP 100/5/5 blend. The temperature of 10 % weight loss (T10) improves from 376 °C for CE/CTBN 100/5 to 407 °C for the CE/CTBN/EP 100/5/2.5 blend. It is proposed that addition of the appropriate amount of EP can decrease the mobility and increase the stability of CTBN via the reaction between the terminal carboxyl group of CTBN and the hydroxyl group of EP. But a very high EP concentration will decrease the crosslinking density of CE, consequently reducing the mechanical properties and thermostability of the blends. Copyright © 2004 Society of Chemical Industry  相似文献   
18.
A novel cholesterol‐imprinted polymer (CMIP‐H) was prepared by a hybrid method of covalent imprinting and non‐covalent imprinting. This approach involves the copolymerization of a template‐containing monomer, cholesteryl 2‐hydroxyethyl methacrylate carbonate, and a cross‐linker, followed by hydrolysis to afford a flexible guest‐binding site accompanied with the easy and efficient removal of a ‘sacrificial spacer’. The effect of solvent on the binding capacity of CMIP‐H towards cholesterol was studied, indicating that a good binding capacity towards cholesterol could be achieved in a less‐polar solvent. The binding experiments of CMIP‐H towards a series of structural analogues of cholesterol, including cholesterol acetate, progesterone and stigmasterol, were carried out in hexane. The results showed that CMIP‐H almost did not bind cholesterol acetate at all because the hydrogen‐bonding site is blocked. It exhibited a similar binding towards both cholesterol and stigmasterol, but much higher binding towards progesterone. Copyright © 2005 Society of Chemical Industry  相似文献   
19.
在互联网服务中,即时通讯已成为了最流行的服务模式之一,人们对即时通讯的依赖程度也与日俱增。但是, 频频出现的病毒和黑客攻击使广大用户深受其害,即时通讯的安全问题也日益严峻。为了从根本上解决问题,本文对即时通讯软件的架构和协议进行了深入分析,目的是找出漏洞根源,给开发者和使用者提供防止漏洞的依据。  相似文献   
20.
Nanocrystalline LaFeO3 is prepared by the dehydration of coprecipitated lanthanum and iron(III) hydroxides. It is shown that the behavior of the samples during heating and the size distribution of LaFeO3 nanocrystals can be considerably different depending on the scheme used for coprecipitation of lanthanum and iron hydroxides; independently of the method employed for coprecipitation of the initial compounds, sintering of the samples at 950°C leads to the formation of lanthanum orthoferrite crystals up to 100 nm in size.  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