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   755篇
  免费   50篇
  国内免费   5篇
电工技术   14篇
综合类   4篇
化学工业   194篇
金属工艺   9篇
机械仪表   12篇
建筑科学   40篇
矿业工程   2篇
能源动力   21篇
轻工业   53篇
水利工程   9篇
石油天然气   8篇
无线电   69篇
一般工业技术   184篇
冶金工业   93篇
原子能技术   7篇
自动化技术   91篇
  2024年   3篇
  2023年   12篇
  2022年   22篇
  2021年   36篇
  2020年   28篇
  2019年   24篇
  2018年   23篇
  2017年   20篇
  2016年   20篇
  2015年   26篇
  2014年   23篇
  2013年   48篇
  2012年   45篇
  2011年   60篇
  2010年   58篇
  2009年   27篇
  2008年   42篇
  2007年   38篇
  2006年   37篇
  2005年   27篇
  2004年   20篇
  2003年   18篇
  2002年   5篇
  2001年   4篇
  2000年   8篇
  1999年   7篇
  1998年   9篇
  1997年   10篇
  1996年   7篇
  1995年   6篇
  1994年   7篇
  1993年   3篇
  1992年   4篇
  1991年   6篇
  1990年   10篇
  1989年   3篇
  1988年   2篇
  1987年   5篇
  1986年   10篇
  1985年   4篇
  1984年   5篇
  1983年   9篇
  1981年   5篇
  1980年   3篇
  1979年   3篇
  1978年   3篇
  1977年   3篇
  1976年   4篇
  1975年   2篇
  1946年   1篇
排序方式: 共有810条查询结果,搜索用时 31 毫秒
801.
802.
山西壶关上好牢村宋金时期砖雕壁画墓作为完整保存了仿木构建筑形象与建筑装饰形象的案例,对宋金时期建筑装饰的研究具有重要参考价值。本文基于精细测绘成果,对山西壶关上好牢村宋金时期砖雕壁画墓 M1 主室的建筑装饰形象与建筑色彩进行了系统整理与记录,对其建筑装饰形象进行了多方案色彩复原的对比,并探讨了该墓装饰与《营造法式》彩画系统的关联性,总结了其建筑装饰特征与装饰手法。  相似文献   
803.
The long-term future of information storage requires the use of sustainable nanomaterials in architectures operating at high frequencies. Interfaces can play a key role in this pursuit via emergent functionalities that break out from conventional operation methods. Here, spin-filtering effects and photocurrents are combined at metal-molecular-oxide junctions in a hybrid magneto-capacitive memory. Light exposure of metal-fullerene-metal oxide devices results in spin-polarized charge trapping and the formation of a magnetic interface. Because the magnetism is generated by a photocurrent, the writing time is determined by exciton formation and splitting, electron hopping, and spin-dependent trapping. Transient absorption spectroscopy measurements show changes in the electronic states as a function of the magnetic history of the device within picoseconds of the optical pumping. The stored information is read using time-resolved scanning magneto optic Kerr effect measurements during microwave irradiation. The emergence of a magnetic interface in the picosecond timescale opens new paths of research to design hybrid magneto-optic structures operating at high frequencies for sensing, computing, and information storage.  相似文献   
804.
805.
Warming temperatures can have negative consequences for aquatic organisms, especially cold-adapted fishes such as Pacific salmon. The magnitude of warming is related to the thermal sensitivity of streams in salmon-bearing watersheds (i.e., change in stream temperature for every 1°C increase in air temperature), which can vary based on several factors including streamflow. Management actions to increase streamflow may therefore benefit salmon by decreasing thermal sensitivity. However, the effects of streamflow on thermal sensitivity are often complex, as the temperature of flow inputs can directly increase or decrease temperatures. This study aimed to disentangle the influence of streamflow on thermal sensitivity and stream temperature over 4 years in the Nicola River, a regulated semiarid watershed in south-central British Columbia, Canada. A statistical modeling approach was used to estimate streamflow effects on stream temperatures and thermal sensitivity (i.e., relationship of regional air temperature to stream temperature) at 12 sites from 2018 to 2021. Streamflow had a variable influence on stream temperatures across the watershed via both direct effects and by modulating thermal sensitivity. At a given site, streamflow was generally negatively associated with summer daily mean stream temperature, but the magnitude of its influence varied among locations and years. The influence of streamflow on thermal sensitivity was also highly variable both spatially and temporally. The analysis suggests that there may be complex relationships between streamflow, stream temperature, and thermal sensitivity, which complicates the efficacy of flow as a lever to mitigate high temperatures in regulated systems.  相似文献   
806.
Metallurgical and Materials Transactions A - Recent research has studied the use of low transformation temperature (LTT) martensite steel as feedstock for wire arc additive manufacturing (WAAM) and...  相似文献   
807.
Stimuli-responsive hydrogels have attracted much attention owing to the versatility of their programmed response in offering intelligent solutions for biomimicry applications, such as soft robotics, tissue engineering, and drug delivery. To achieve the complexity of biomimetic structures, two photon polymerization (2PP) has provided a means of fabricating intricate 3D structures from stimuli-responsive hydrogels. Rapid swelling hydrogel microstructures are advantageous for osmotically driven stimuli-response, where actuation speed, that is reliant on the diffusion of analytes or bioanalytes, can be optimized. Herein, the flexibility of 2PP is exploited to showcase a novel sugar-responsive, phenylboronic acid-based photoresist. This offers a remarkable solution for achieving fast response hydrogel systems that have been often hindered by the volume-dependent diffusion times of analytes to receptor sites. A phenylboronic acid-based photoresist compatible with 2PP is presented to fabricate stimuli-responsive microstructures with accelerated response times. Moreover, microstructures with programmable actuation (i.e., bending and opening) are fabricated using the same photoresist within a one-step fabrication process. By combining the flexibility of 2PP with an easily adaptable photoresist, an accessible fabrication method is showcased for sophisticated and chemo-responsive 3D hydrogel actuators.  相似文献   
808.
Through a novel laser ablative patterning (LAP) process, the present work reported the increase in wetting contact angle of two ceramic materials, boron carbide (B4C) and molybdenum aluminum boride (MoAlB). The LAP technique employed picosecond laser pulses to form a crosshatch pattern with micropillars on ceramic surfaces. The wetting behavior of both ceramic surfaces was successfully transitioned from hydrophilic (θ < 90°) to hydrophobic (θ > 90°), which was related to Wenzel and Cassie–Baxter mechanisms. Parameters such as laser fluence and number of laser scans were varied to study their effects on ceramic surface characteristics. Lunar dust adhesion experiments were performed on these hydrophobic ceramic surfaces, which showed that the adhesion of lunar soil simulant dust particles was significantly reduced in the patterned B4C and MoAlB surfaces.  相似文献   
809.
A heat transport system based on heat pipes is developed and analyzed. The aim is to increase the efficiency of electrical engines by transferring dissipation-related heat. The system performance is investigated experimentally by varying the temperature range and the supplied heat flow as well as the rotational speed. The thermal resistance of the system is reduced by 98 % compared to pure heat conduction. The rotation of the system has no significant influence on the thermal resistance, which is constant until the power limit is reached. The power limit is dependent on temperature and approximately coincides with the capillary force limit.  相似文献   
810.
Teleworking, also known as remote working, has become the new norm for many workers since the coronavirus disease 2019 (COVID-19) pandemic. Studies show that during this time, the incidence of musculoskeletal pain is increasing among these workers. Despite this, few studies have addressed the possible correlates of musculoskeletal paśin in teleworkers, with several potential predictors receiving little or no attention in published studies. With this in mind, an online survey was conducted among organizations in the IT and communications sectors in Malta. Information was collected from 459 teleworkers on the frequency of telework, frequency of work during nonworking hours, exercise frequency, burnout, and ergonomic arrangements. Demographic data were also collected. Results revealed that 55.8% reported one or more musculoskeletal pain. Back pain was the most common, followed by neck and shoulder pain. The presence of pain, the number of painful body areas, and the presence of back, neck, and shoulder pain were each individually associated with work during nonworking hours, lower levels of exercise, and higher levels of burnout. It is argued that musculoskeletal pain appears to be common among teleworkers and may negatively impact the quality of life and organizational performance. Companies and occupational health practitioners should strive to identify the prevalence of these problems among their teleworkers, develop appropriate preventive measures, and support workers to obtain multidisciplinary care when needed.  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