全文获取类型
收费全文 | 4676篇 |
免费 | 260篇 |
国内免费 | 5篇 |
专业分类
电工技术 | 34篇 |
综合类 | 7篇 |
化学工业 | 1175篇 |
金属工艺 | 62篇 |
机械仪表 | 76篇 |
建筑科学 | 263篇 |
矿业工程 | 6篇 |
能源动力 | 73篇 |
轻工业 | 705篇 |
水利工程 | 43篇 |
石油天然气 | 24篇 |
无线电 | 231篇 |
一般工业技术 | 673篇 |
冶金工业 | 1020篇 |
原子能技术 | 17篇 |
自动化技术 | 532篇 |
出版年
2023年 | 30篇 |
2022年 | 97篇 |
2021年 | 150篇 |
2020年 | 64篇 |
2019年 | 101篇 |
2018年 | 117篇 |
2017年 | 99篇 |
2016年 | 138篇 |
2015年 | 97篇 |
2014年 | 177篇 |
2013年 | 282篇 |
2012年 | 215篇 |
2011年 | 307篇 |
2010年 | 219篇 |
2009年 | 202篇 |
2008年 | 229篇 |
2007年 | 196篇 |
2006年 | 207篇 |
2005年 | 138篇 |
2004年 | 154篇 |
2003年 | 132篇 |
2002年 | 108篇 |
2001年 | 70篇 |
2000年 | 76篇 |
1999年 | 71篇 |
1998年 | 110篇 |
1997年 | 91篇 |
1996年 | 99篇 |
1995年 | 64篇 |
1994年 | 57篇 |
1993年 | 65篇 |
1992年 | 61篇 |
1991年 | 47篇 |
1990年 | 58篇 |
1989年 | 45篇 |
1988年 | 59篇 |
1987年 | 37篇 |
1986年 | 37篇 |
1985年 | 36篇 |
1984年 | 39篇 |
1983年 | 28篇 |
1982年 | 40篇 |
1981年 | 21篇 |
1980年 | 30篇 |
1979年 | 31篇 |
1978年 | 22篇 |
1977年 | 20篇 |
1976年 | 16篇 |
1975年 | 21篇 |
1973年 | 11篇 |
排序方式: 共有4941条查询结果,搜索用时 15 毫秒
101.
Adverse effects of vitamin D deficiency on the Pi3k/Akt pathway and pancreatic islet morphology in diet‐induced obese mice 下载免费PDF全文
102.
103.
This study reviews the development of railway safety in Finland from 1959 to 2008. The results show that the level of safety has greatly improved over the past five decades. The total number of railway fatalities did not show any obvious decreasing or increasing trend during the first decade, but since the early 1970s the annual number of fatalities has decreased from about 100 to 20. The estimated overall annual reduction per year from 1970 to 2008 was 5.4% (with a 95% confidence interval from −8.2% to −2.6%). The reduction in subcategories per million train-kilometres from 1959 to 2008 was 4.4% per year for passengers, 8.3% for employees, 5.0% for road users at level crossings and 3.6% for others (mainly trespassers). The safety improvement for passengers and staff was probably influenced by the introduction of central locking of doors in passenger cars and improved procedures to protect railway employees working on the tracks. The number of road users killed at level crossings has fallen due to the installation of barriers and the construction of overpasses and underpasses at crossings with dense traffic, removal of level crossings, and an improvement of conditions such as visibility at crossings. The number of trespasser fatalities has seen the least decline. Key plans for the future include further reduction of the number of level crossings on the state railway network from the current roughly 3500–2200 by 2025, and involving communities in safety work related to railway trespassers. 相似文献
104.
Enhancing Photovoltaic Performance Using an All‐Conjugated Random Copolymer to Tailor Bulk and Interfacial Morphology of the P3HT:ICBA Active Layer 下载免费PDF全文
Anton Li Jojo Amonoo Bingyuan Huang Peter K. Goldberg Anne J. McNeil Peter F. Green 《Advanced functional materials》2014,24(35):5594-5602
Bulk heterojunction (BHJ) solar cells are fabricated using active material blends of poly(3‐hexylthiophene) (P3HT) donor, indene‐C60 bisadduct (ICBA) acceptor, and an all‐conjugated random copolymer (RCP) additive. By optimizing RCP loading, power conversion efficiencies (PCEs) up to 20% higher than those of a binary P3HT:ICBA mixture are achieved. The improved device characteristics are rationalized in terms of the differences between the photoactive thin film morphologies. Energy‐filtered transmission electron microscopy reveals that incorporation of the RCP improves the degree of structural order of the BHJ fibrillar network and increases the extent of microphase separation between P3HT and ICBA. Additionally, a combination of atomic force microscopy and X‐ray photoelectron spectroscopy analysis indicates segregation of the RCP at the free interface, leading to a shift in the surface potentials measured by Kelvin probe force microscopy. These changes, both in the bulk morphology and in the interfacial composition/energetics, are correlated to improved carrier collection efficiency due to a reduction of non‐geminate recombination, which is measured by charge extraction of photogenerated carriers by linearly increasing voltage. 相似文献
105.
106.
ABSTRACTThis article explores how private owners can protect bodies of water through private property rights. It compares the use of conventional property rights in the Netherlands and New Zealand with a novel approach whereby a New Zealand river owns itself. 相似文献
107.
108.
Clement Appiah Christine Arndt Katharina Siemsen Anne Heitmann Anne Staubitz Christine Selhuber‐Unkel 《Advanced materials (Deerfield Beach, Fla.)》2019,31(36)
Living beings have an unsurpassed range of ways to manipulate objects and interact with them. They can make autonomous decisions and can heal themselves. So far, a conventional robot cannot mimic this complexity even remotely. Classical robots are often used to help with lifting and gripping and thus to alleviate the effects of menial tasks. Sensors can render robots responsive, and artificial intelligence aims at enabling autonomous responses. Inanimate soft robots are a step in this direction, but it will only be in combination with living systems that full complexity will be achievable. The field of biohybrid soft robotics provides entirely new concepts to address current challenges, for example the ability to self‐heal, enable a soft touch, or to show situational versatility. Therefore, “living materials” are at the heart of this review. Similarly to biological taxonomy, there is a recent effort for taxonomy of biohybrid soft robotics. Here, an expansion is proposed to take into account not only function and origin of biohybrid soft robotic components, but also the materials. This materials taxonomy key demonstrates visually that materials science will drive the development of the field of soft biohybrid robotics. 相似文献
109.
110.
Information technology (IT) implementation continues to be a challenging process for many organizations. The challenge is heightened when systems are changed due to mergers and acquisitions (M&A). The recent focus on IT-service management highlights the importance of having positive relationships between IT-service providers and end-users. In an M&A situation, there is often little history, and thus limited basis for trust in the IT organization, yet systems often need to be changed in these situations. The current study examines the IT-service provider’s relationship with the end-user to ascertain the factors that influence that relationship and ultimately influence end-user attitudes toward the new system. We study a mandated implementation following an acquisition in the banking industry. The results highlight the important and fragile nature of trust in the IT-service provider. In addition, the results demonstrate that there are significant differences in what matters at what time during the implementation process. 相似文献