全文获取类型
收费全文 | 90483篇 |
免费 | 1102篇 |
国内免费 | 423篇 |
专业分类
电工技术 | 1070篇 |
综合类 | 2319篇 |
化学工业 | 12856篇 |
金属工艺 | 4940篇 |
机械仪表 | 3190篇 |
建筑科学 | 2319篇 |
矿业工程 | 563篇 |
能源动力 | 1295篇 |
轻工业 | 4240篇 |
水利工程 | 1303篇 |
石油天然气 | 349篇 |
无线电 | 9821篇 |
一般工业技术 | 17456篇 |
冶金工业 | 4001篇 |
原子能技术 | 474篇 |
自动化技术 | 25812篇 |
出版年
2023年 | 41篇 |
2022年 | 81篇 |
2021年 | 144篇 |
2020年 | 69篇 |
2019年 | 83篇 |
2018年 | 14544篇 |
2017年 | 13442篇 |
2016年 | 10094篇 |
2015年 | 682篇 |
2014年 | 384篇 |
2013年 | 558篇 |
2012年 | 3372篇 |
2011年 | 9725篇 |
2010年 | 8504篇 |
2009年 | 5827篇 |
2008年 | 7049篇 |
2007年 | 7999篇 |
2006年 | 370篇 |
2005年 | 1427篇 |
2004年 | 1327篇 |
2003年 | 1383篇 |
2002年 | 740篇 |
2001年 | 240篇 |
2000年 | 296篇 |
1999年 | 228篇 |
1998年 | 582篇 |
1997年 | 397篇 |
1996年 | 315篇 |
1995年 | 161篇 |
1994年 | 168篇 |
1993年 | 176篇 |
1992年 | 83篇 |
1991年 | 91篇 |
1990年 | 68篇 |
1989年 | 67篇 |
1988年 | 66篇 |
1987年 | 43篇 |
1986年 | 67篇 |
1985年 | 72篇 |
1984年 | 48篇 |
1983年 | 52篇 |
1982年 | 41篇 |
1981年 | 45篇 |
1980年 | 43篇 |
1976年 | 50篇 |
1968年 | 46篇 |
1966年 | 45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 15 毫秒
1.
In this study, feasibility of membrane separation for the removal of indigenous noroviruses (NVs) is evaluated. The indigenous NV gene was never detected from ultrafiltration (UF) permeates of sewage sludge and treated wastewater. Indigenous NV gene was also not detected from permeates of sewage sludge and treated wastewater by microfiltration (MF) with a pore size of 0.1 microm (MF0.1). Even though the pore size of MF (0.1 microm) was much larger than the diameter of virus particle (approximately 30-40nm), more than 4-log10 reduction value (LRV) at maximum was achieved by membrane separation with MF0.1. NV genes were often detected from permeates of sewage sludge and treated wastewater by MF with a pore size of 0.45 microm (MF0.45), although the maximum log10 reduction values were more than 3.59 for sewage sludge and more than 2.90 for treated wastewater. It is important to verify factors determining the removal efficiency of viruses with MF membranes. 相似文献
2.
Watanabe H. Komori J. Higashitani K. Sekine M. Koyama H. 《Semiconductor Manufacturing, IEEE Transactions on》1997,10(2):228-232
A novel monitoring method for plasma-charging damage is proposed. This method performs a quick and accurate evaluation using antenna PMOSFET. It was found that not only hot-carrier (HC) lifetime but transistor parameters such as initial gate current and substrate current were changed according to the degree of plasma-charging damage. However, the present work suggests that monitoring the shift of drain current after a few seconds of HC stress is a more accurate method to indicate plasma-charging damage. The monitoring method using the present test structure is demonstrated to be useful for realizing highly reliable devices 相似文献
3.
The purpose of this paper is to evaluate two methods of assessing the productivity and quality impact of Computer Aided Software Engineering (CASE) and Fourth Generation Language (4GL) technologies: (1) by the retrospective method; and (2) the cross-sectional method. Both methods involve the use of questionnaire surveys. Developers' perceptions depend on the context in which they are expressed and this includes expectations about the effectiveness of a given software product. Consequently, it is generally not reliable to base inferences about the relative merits of CASE and 4GLs on a cross-sectional comparison of two separate samples of users. The retrospective method that requires each respondent to directly compare different products is shown to be more reliable. However, there may be scope to employ cross-sectional comparisons of the findings from different samples where both sets of respondents use the same reference point for their judgements, and where numerical rather than verbal rating scales are used to measure perceptions. 相似文献
4.
5.
6.
J-M Choe 《欧洲信息系统杂志》2002,11(2):142-158
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
7.
8.
9.
10.