全文获取类型
收费全文 | 6237篇 |
免费 | 493篇 |
国内免费 | 111篇 |
专业分类
电工技术 | 253篇 |
综合类 | 204篇 |
化学工业 | 1121篇 |
金属工艺 | 226篇 |
机械仪表 | 210篇 |
建筑科学 | 366篇 |
矿业工程 | 49篇 |
能源动力 | 331篇 |
轻工业 | 572篇 |
水利工程 | 104篇 |
石油天然气 | 190篇 |
武器工业 | 4篇 |
无线电 | 719篇 |
一般工业技术 | 915篇 |
冶金工业 | 384篇 |
原子能技术 | 31篇 |
自动化技术 | 1162篇 |
出版年
2024年 | 12篇 |
2023年 | 109篇 |
2022年 | 178篇 |
2021年 | 262篇 |
2020年 | 205篇 |
2019年 | 197篇 |
2018年 | 250篇 |
2017年 | 225篇 |
2016年 | 271篇 |
2015年 | 239篇 |
2014年 | 265篇 |
2013年 | 492篇 |
2012年 | 382篇 |
2011年 | 460篇 |
2010年 | 375篇 |
2009年 | 365篇 |
2008年 | 312篇 |
2007年 | 258篇 |
2006年 | 253篇 |
2005年 | 207篇 |
2004年 | 138篇 |
2003年 | 158篇 |
2002年 | 217篇 |
2001年 | 154篇 |
2000年 | 115篇 |
1999年 | 66篇 |
1998年 | 97篇 |
1997年 | 70篇 |
1996年 | 61篇 |
1995年 | 64篇 |
1994年 | 61篇 |
1993年 | 43篇 |
1992年 | 23篇 |
1991年 | 15篇 |
1990年 | 19篇 |
1989年 | 10篇 |
1988年 | 15篇 |
1987年 | 16篇 |
1986年 | 14篇 |
1985年 | 11篇 |
1984年 | 24篇 |
1983年 | 13篇 |
1982年 | 17篇 |
1981年 | 11篇 |
1980年 | 6篇 |
1979年 | 11篇 |
1978年 | 10篇 |
1977年 | 11篇 |
1976年 | 13篇 |
1975年 | 11篇 |
排序方式: 共有6841条查询结果,搜索用时 15 毫秒
1.
Christoph Gottschalk Aiko Huckauf Arne Dübecke Florian Kaltner Matthias Zimmermann Ines Rahaus 《Food additives & contaminants. Part A, Chemistry, analysis, control, exposure & risk assessment》2018,35(7):1366-1383
The contamination of honey with hepatotoxic pyrrolizidine alkaloids (PAs) is a well-known hazard for food safety. While management strategies and controls of the honey industry aim to reduce the PA levels, uncertainties remain with regard to the safety of regionally produced and marketed honey. In addition, a previous study showed large differences of results obtained after various periods of storage and apparent differences between the analytical results of different laboratories. Therefore, this study aimed at examining these uncertainties by monitoring the impact of storage on the PA and PA N-oxide (PANO) content of two freshly harvested honeys and on possible demixing effects caused by pollen settling. Additionally, three analytical approaches – target analysis with matrix-matched calibration or standard addition and a sum parameter method – were applied for a comparative analysis of 20 honeys harvested in summer 2016. All samples originated from Schleswig-Holstein in Northern Germany where the PA plant Jacobaea vulgaris is currently observed on a massive scale. The results of the time series analyses showed that PANO levels markedly decreased within a few weeks and practically reached the LOD 16 weeks after harvest. Tertiary PAs, by contrast, remained stable and did not increase as a consequence of PANO decrease. The experiments on a putative demixing, which may result in a heterogeneous distribution of PAs/PANOs, revealed that there was no such effect during storage of up to 12 weeks. A comparison of the PA/PANO levels obtained by different analytical approaches showed that in some cases the sum parameter method yielded much higher levels than the target approaches, whereas in other cases, the target analysis with standard addition found higher levels than the other two methods. In summary, the results of this study highlight uncertainties regarding the validity and comparability of analytical results and consequently regarding health risk assessment. 相似文献
2.
3.
4.
Yingcai Bi Menglu Lan Jiaxin Li Shupeng Lai Ben M. Chen 《Asian journal of control》2019,21(4):1732-1744
Micro Aerial Vehicles (MAVs) have great potentials to be applied for indoor search and rescue missions. In this paper, we propose a modular lightweight design of an autonomous MAV with integrated hardware and software. The MAV is equipped with the 2D laser scanner, camera, mission computer and flight controller, running all the computation onboard in real time. The onboard perception system includes a laser‐based SLAM module and a custom‐designed visual detection module. A dual Kalman filter design provides robust state estimation by multiple sensor fusion. Specifically, the fusion module provides robust altitude measurement in the circumstance of surface changing. In addition, indoor‐outdoor transition is explicitly handled by the fusion module. In order to efficiently navigate through obstacles and adapt to multiple tasks, a task tree‐based mission planning method is seamlessly integrated with path planning and control modules. The MAV is capable of searching and rescuing victims from unknown indoor environments effectively. It was validated by our award‐winning performance at the 2017 International Micro Air Vehicle Competition (IMAV 2017), held in Toulouse, France. The performance video is available on https://youtu.be/8H19ppS_VXM . 相似文献
5.
Chinh Ngo Radhika Mehta Kanchan Aggarwal Audrey G. Fikes Dr. Ines C. Santos Dr. Sylvester M. Greer Prof. Dr. Emily L. Que 《Chembiochem : a European journal of chemical biology》2019,20(8):1003-1007
One-third of all proteins are estimated to require metals for structural stability and/or catalytic activity. Desthiobiotin probes containing metal binding groups can be used to capture metalloproteins with exposed active-site metals under mild conditions so as to prevent changes in metallation state. The proof-of-concept was demonstrated with carbonic anhydrase (CA), an open active site, Zn2+-containing protein. CA was targeted by using sulfonamide derivatives. Linkers of various lengths and structures were screened to determine the optimal structure for capture of the native protein. The optimized probes could selectively pull down CA from red blood cell lysate and other protein mixtures. Pull-down of differently metallated CAs was also investigated. 相似文献
6.
The Journal of Supercomputing - Data center network virtualization is being considered as a promising technology to provide a performance guarantee for cloud computing applications. One important... 相似文献
7.
Abdeljaoued Emna Brulé Mathieu Tayibi Saida Manolakos Dimitris Oukarroum Abdallah Monlau Florian Barakat Abdellatif 《Clean Technologies and Environmental Policy》2020,22(10):1967-1997
Clean Technologies and Environmental Policy - Biochar has caught great attention over the last decade, yielding a large number of publications in a broad range of disciplines. This scientometric... 相似文献
8.
LNG冷量优化集成利用技术 总被引:7,自引:1,他引:6
我国将相继在沿海地区建成多个LNG接收站,每年将进口数以千万吨计的LNG,同时携带数着巨额冷量,而这些冷量可用于发电、空气分离、制造干冰、低温冷库等众多领域。基于国外LNG冷量利用现状,指出我国即将展开和实施此项技术还存在着:过程火用损较大,缺乏系统、全面的LNG冷量利用技术的研发指导机制,以及宏观调控力度薄弱等问题,进而提出了发展LNG冷量的集成利用方案,可为此类技术的研发利用提供新思路。以福建即将进口的LNG为例,模拟了空气分离与干冰制备的集成工艺流程,结果表明:福建每年进口的260×104t LNG可以冷却290×104t空气,相当于60000 m3/h的氧气制备规模,还可以生产100×104t的干冰,其过程火用损较小;其剩余的高温位冷量可应用于低温冻结库或冰灯等项目,这对主体装置的实施效果和过程火用损的影响较小。该技术的优点在于可灵活控制冷却空气的液化率,基本不用冷却循环水,流程简单,设备投资少,能耗低等。 相似文献
9.
N Haddad R Ben Khelifa H Matter H Kharmachi MF Aubert A Wandeler J Blancou 《Canadian Metallurgical Quarterly》1994,12(4):307-309
The possibility of immunizing dogs orally against rabies, using SADBern, an attenuated strain, was tested on dogs in the field in Tunisia. This strain induced high neutralizing antibody titres and conferred to all vaccinated dogs total resistance against a challenge with a Maghrebian strain. However, an excretion of virus of vaccinal origin was observed in one dog, hampering the use of SADBern in dogs. Nevertheless, this work demonstrates for the first time that dogs in developing countries, especially those which are inaccessible to parenteral vaccination, could be efficiently immunized against rabies by the oral route. 相似文献
10.