全文获取类型
收费全文 | 108339篇 |
免费 | 12853篇 |
国内免费 | 8749篇 |
专业分类
电工技术 | 7446篇 |
技术理论 | 13篇 |
综合类 | 10450篇 |
化学工业 | 6149篇 |
金属工艺 | 3776篇 |
机械仪表 | 7440篇 |
建筑科学 | 5668篇 |
矿业工程 | 4146篇 |
能源动力 | 1585篇 |
轻工业 | 6326篇 |
水利工程 | 2287篇 |
石油天然气 | 4154篇 |
武器工业 | 1654篇 |
无线电 | 16252篇 |
一般工业技术 | 7137篇 |
冶金工业 | 3483篇 |
原子能技术 | 1140篇 |
自动化技术 | 40835篇 |
出版年
2024年 | 445篇 |
2023年 | 1508篇 |
2022年 | 2843篇 |
2021年 | 3658篇 |
2020年 | 3701篇 |
2019年 | 2867篇 |
2018年 | 2608篇 |
2017年 | 3371篇 |
2016年 | 3818篇 |
2015年 | 4467篇 |
2014年 | 7005篇 |
2013年 | 6398篇 |
2012年 | 7939篇 |
2011年 | 8532篇 |
2010年 | 6498篇 |
2009年 | 6460篇 |
2008年 | 6819篇 |
2007年 | 7961篇 |
2006年 | 6876篇 |
2005年 | 6112篇 |
2004年 | 5176篇 |
2003年 | 4518篇 |
2002年 | 3619篇 |
2001年 | 2919篇 |
2000年 | 2506篇 |
1999年 | 1879篇 |
1998年 | 1534篇 |
1997年 | 1331篇 |
1996年 | 1126篇 |
1995年 | 977篇 |
1994年 | 837篇 |
1993年 | 644篇 |
1992年 | 490篇 |
1991年 | 423篇 |
1990年 | 374篇 |
1989年 | 306篇 |
1988年 | 220篇 |
1987年 | 140篇 |
1986年 | 118篇 |
1985年 | 161篇 |
1984年 | 122篇 |
1983年 | 140篇 |
1982年 | 112篇 |
1981年 | 76篇 |
1980年 | 56篇 |
1979年 | 59篇 |
1978年 | 30篇 |
1977年 | 41篇 |
1976年 | 23篇 |
1959年 | 13篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
31.
This paper analyzes the problems existing in the teaching of data structure course, and puts forward the reform from the as-
pects of strengthening basic programming, visualized explanation of abstract theory, combination of C++, Java programming, ratio-
nal use of online platform, and stratification of exercises, aiming at improving students' practical ability, learning interest and self-
confidence. 相似文献
32.
In the first critical assessment of knowledge economy dynamic paths in Africa and the Middle East, but for a few exceptions, we find overwhelming support for diminishing cross-country disparities in knowledge-based economy dimensions. The paper employs all the four components of the World Bank's Knowledge Economy Index (KEI): economic incentives, innovation, education, and information infrastructure. The main finding suggests that sub-Saharan African (SSA) and the Middle East and North African (MENA) countries with low levels of KE dynamics and catching-up their counterparts of higher KE levels. We provide the speeds of integration and time necessary to achieve full (100%) integration. Policy implications are also discussed. 相似文献
33.
34.
35.
36.
Qiaozhi Zhang Yanbo Wang Linglin Fu 《Comprehensive Reviews in Food Science and Food Safety》2020,19(5):2559-2587
Dietary advanced glycation end products (dAGEs) are complex and heterogeneous compounds derived from nonenzymatic glycation reactions during industrial processing and home cooking. There is mounting evidence showing that dAGEs are closely associated with various chronic diseases, where the absorbed dAGEs fuel the biological AGEs pool to exhibit noxious effects on human health. Currently, due to the uncertain bioavailability and rapid renal clearance of dAGEs, the relationship between dAGEs and biological AGEs remains debatable. In this review, we provide the most updated information on dAGEs including their generation in processed foods, analytical and characterization techniques, metabolic fates, interaction with AGE receptors, implications on human health and reducing strategies. Available evidence demonstrating a relevance between dAGEs and food allergy is also included. AGEs are ubiquitous in foods and their contents largely depend on the reactivity of carbonyl and amino groups, along with surrounding condition mainly pH and heating procedures. Once being digested and absorbed into the circulation, two separate pathways can be involved in the deleterious effects of dAGEs: an AGE receptor‐dependent way to stimulate cell signals, and an AGE receptor‐independent way to dysregulate proteins via forming complexes. Inhibition of AGEs formation during food processing and reduction in the diet are two potent approaches to restrict health‐hazardous dAGEs. To elucidate the biological role of dAGEs toward human health, the following significant perspectives are raised: molecular size and complexity of dAGEs; interactions between unabsorbed dAGEs and gut microbiota; and roles played by concomitant compounds in the heat‐processed foods. 相似文献
37.
38.
《Advanced Powder Technology》2020,31(2):746-754
Although many colloidal assembling systems have been reported, most systems suffer from severe aggregation under high solid concentrations, which can often be observed in typical hetero-aggregation system. In this study, we created a hetero-assembly system using concentrated (~50 vol%) suspensions by mixing large SiO2 particles modified with polyacrylic acid partially complexed with oleylamine (PAA-OAm) and small SiO2 particles modified with polyethyleneimine partially complexed with oleic acid (PEI-OA) in a non-aqueous solvent. We demonstrated that hetero-assembly is driven by the interactions between the uncomplexed carboxyl/amine groups of the PAA/PEI present on the particles, while severe aggregation is simultaneously prevented by the steric repulsions of the aliphatic oleyl chains. Comparison of the cross sections of the in-situ solidified hetero-assembled suspensions with those of ideally assembled structures which were reproduced by a simulation considering the statistical distribution of particles strongly supported successful particle assembling via the proposed approach. The results revealed that the OA content in the PEI-OA complex was the dominant factor that controlled the dispersion and assembling state of the binary particles. The significance of this study is that our findings will provide a class of colloidal dispersion state which binary particles were assembled in a high solid content suspension without forming strong aggregates. 相似文献
40.
Paul Geoerg Florian Berchtold Steven Gwynne Karen Boyce Stefan Holl Anja Hofmann 《火与材料》2019,43(7):759-781
To quantify the evacuation process, evacuation practitioners use engineering egress data describing the occupant movement characteristics. These data are typically based to young and fit populations. However, the movement abilities of occupants who might be involved in evacuations are becoming more variable—with the building populations of today typically including increasing numbers of individuals: with impairments or who are otherwise elderly or generally less mobile. Thus, there will be an increasing proportion of building occupants with reduced ability to egress. For safe evacuation, there is therefore a need to provide valid engineering egress data considering pedestrians with disabilities. Gwynne and Boyce recently compiled a series of data sets related to the evacuation process to support practitioner activities in the chapter Engineering Data in the SFPE Handbook of Fire Protection Engineering. This paper supplements these data sets by providing information on and presenting data obtained from additional research related to the premovement and horizontal movement of participants with physical‐, cognitive‐, or age‐related disabilities. The aim is to provide an overview of currently available data sets related to, and key factors affecting the egress performance of, mixed ability populations which could be used to guide fire safety engineering decisions in the context of building design. 相似文献