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   1132篇
  免费   36篇
  国内免费   2篇
电工技术   11篇
综合类   1篇
化学工业   166篇
金属工艺   9篇
机械仪表   19篇
建筑科学   86篇
矿业工程   8篇
能源动力   30篇
轻工业   100篇
水利工程   6篇
石油天然气   6篇
无线电   122篇
一般工业技术   180篇
冶金工业   104篇
原子能技术   8篇
自动化技术   314篇
  2023年   6篇
  2022年   12篇
  2021年   39篇
  2020年   16篇
  2019年   25篇
  2018年   34篇
  2017年   37篇
  2016年   42篇
  2015年   22篇
  2014年   31篇
  2013年   89篇
  2012年   77篇
  2011年   90篇
  2010年   62篇
  2009年   66篇
  2008年   81篇
  2007年   69篇
  2006年   60篇
  2005年   42篇
  2004年   36篇
  2003年   25篇
  2002年   33篇
  2001年   16篇
  2000年   11篇
  1999年   13篇
  1998年   21篇
  1997年   18篇
  1996年   15篇
  1995年   8篇
  1994年   6篇
  1993年   3篇
  1992年   3篇
  1991年   3篇
  1989年   3篇
  1988年   5篇
  1987年   2篇
  1985年   5篇
  1984年   6篇
  1983年   3篇
  1982年   3篇
  1981年   7篇
  1980年   2篇
  1979年   2篇
  1975年   4篇
  1974年   3篇
  1973年   2篇
  1963年   2篇
  1954年   1篇
  1951年   1篇
  1945年   1篇
排序方式: 共有1170条查询结果,搜索用时 15 毫秒
991.
A 3-day monolithic polyacrylate adhesive dispersion type delivery system containing methadone was fabricated and in vitro permeation through hairless mouse and human cadaver skins was conducted. The effect of skin permeation enhancers was also investigated. Skin permeation rate across human cadaver skin was found to be lower than that of hairless mouse. Skin permeation profiles across both types of skins showed a membrane permeation controlled cumulative amount permeated (Q) versus time (t) relationship. Skin permeation rate was found to be dependent on both adhesive film thickness and loading dose of the drug in the matrix. Effective skin permeation rate across the hairless mouse skin was obtained from a patch with 1.5 mm thickness and 15% w/w loading dose. n-Decylmethyl sulfoxide and Azone were found to produce an effective skin permeation rate of methadone through human cadaver skin at a 5% w/w concentration. These initial studies demonstrated the feasibility of methadone administration through intact skin from a transdermal patch.  相似文献   
992.
Although the theoretical framework of expert systems has been well established, the process of developing a non-trivial expert system is still considered a difficult task. The main reason for this is that the nature of expert systems is knowledge-intensive. Also, it is usually difficult for domain experts to explain or communicate their expertise to the system professionals. Many methodologies have been proposed to overcome this domain knowledge representation problem. Most of them require the assistance of an expert system shell (tool). However, with a purpose of helping the system development in mind, most of them were not satisfactory. This research takes the experience of implementing a course scheduling expert system, and suggests two analysis methods to describe the characteristics of course scheduling knowledge. It is shown that these methods provide assistance on clarifying the complicated scheduling problem. Another favorable advantage of this method is its capability helping the transferring of domain knowledge to rules in the knowledge base.  相似文献   
993.
In this paper, we demonstrate how craft practice in contemporary jewellery opens up conceptions of ‘digital jewellery’ to possibilities beyond merely embedding pre-existing behaviours of digital systems in objects, which follow shallow interpretations of jewellery. We argue that a design approach that understands jewellery only in terms of location on the body is likely to lead to a world of ‘gadgets’, rather than anything that deserves the moniker ‘jewellery’. In contrast, by adopting a craft approach, we demonstrate that the space of digital jewellery can include objects where the digital functionality is integrated as one facet of an object that can be personally meaningful for the holder or wearer.  相似文献   
994.
The cognitive advantage of imagined spatial transformations of the human body over that of more unfamiliar objects (e.g., Shepard-Metzler [S-M] cubes) is an issue for validating motor theories of visual perception. In 6 experiments, the authors show that providing S-M cubes with body characteristics (e.g., by adding a head to S-M cubes to evoke a posture) facilitates the mapping of the cognitive coordinate system of one's body onto the abstract shape. In turn, this spatial embodiment improves object shape matching. Thanks to the increased cohesiveness of human posture in people's body schema, imagined transformations of the body operate in a less piecemeal fashion as compared with objects (S-M cubes or swing-arm desk lamps) under a similar spatial configuration, provided that the pose can be embodied. If the pose cannot be emulated (covert imitation) by the sensorimotor system, the facilitation due to motoric embodiment will also be disrupted. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
995.
According to the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) report in 1982, radiation from radon contributes about 50% of all natural radiation sources to the public. The situation is worse in Hong Kong where large area is granitic containing larger amount of uranium when compared to the global mean. Radon level can therefore be on the high side during tunneling especially where poor ventilation is envisaged. This article includes realistic field study of radon in tunnel under construction. A maximum concentration of over 30,000?Bq/m3 was recorded (1 Becquerels per cubic meter is equivalent to 0.027?pico?Curies/L). Radon concentration in tunnel environment is found to be related to groundwater ingress, ventilation provision and geology. A review of the current statutory control in Hong Kong is done as well as its comparison with other countries’ practices. In fact, the situation can be improved through education, adopting control legislation and more specifically, having a suggested radon management plan in every tunnel drilling project.  相似文献   
996.
AMyChow 《今日电子》2003,(8):51-52
开关模式电源(SMPS)功率电感器的选择过程绝非是信手拈来那么简单,必须要对对实际电感器有充分的了解。SMPS的选用要求包括:大功率、小尺寸、高开关频率和高效率。此外,考虑到健康、环保方面的因素,很多用户还提出了降低电磁辐射(EMI)的要求。理想的电感器选择除了取决于对实际电感器(并不完善的)特性的了解之外,还需要对完善的电感器特性有一定的通晓。储能方面的考虑14种基本的SMPS设计大多依靠电感器来进行储能和EMI抑制(滤波)。控制电路负责对储存的能量进行调节,并通过将电感器与电源相连的方法来增加能量的存储。存储在一个电…  相似文献   
997.
对粉末涂料与涂装的发展历史作了简要的介绍。  相似文献   
998.
Verbal information has long been assumed to be an indirect pathway to fear. Children (aged 6-8 or 12-13 years) were exposed to threat, positive, or no information about 3 novel animals to see the long-term impact on their fear cognitions and the immediate impact on avoidance behavior. Their directly (self-report) and indirectly (implicit association task) measured attitudes toward the animals changed congruent with the information provided, and the changes persisted up to 6 months later. Verbal threat information also induced behavioral avoidance of the animal. Younger children formed stronger animal- threat and animal-safe associations because of threat and positive verbal information than older children, but there were negligible age effects on self-reported fear beliefs and avoidance behaviors. These results support theories of fear acquisition that suppose that verbal information affects components of the fear emotion. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
999.
A novel paradigm was developed to study the behavior of groups of networked people searching a problem space. The authors examined how different network structures affect the propagation of information in laboratory-created groups. Participants made numerical guesses and received scores that were also made available to their neighbors in the network. The networks were compared on speed of discovery and convergence on the optimal solution. One experiment showed that individuals within a group tend to converge on similar solutions even when there is an equally valid alternative solution. Two additional studies demonstrated that the optimal network structure depends on the problem space being explored, with networks that incorporate spatially based cliques having an advantage for problems that benefit from broad exploration, and networks with greater long-range connectivity having an advantage for problems requiring less exploration. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
1000.
A method is developed which makes it possible to scan and reconstruct an object with cone beam x-rays in a spiral scan path with area detectors much shorter than the length of the object. The method is mathematically exact. If only a region of interest of the object is to be imaged, a top circle scan at the top level of the region of interest and a bottom circle scan at the bottom level of the region of interest are added. The height of the detector is required to cover only the distance between adjacent turns in the spiral projected at the detector. To reconstruct the object, the Radon transform for each plane intersecting the object is computed from the totality of the cone beam data. This is achieved by suitably combining the cone beam data taken at different source positions on the scan path; the angular range of the cone beam data required at each source position can be determined easily with a mask which is the spiral scan path projected on the detector from the current source position. The spiral scan algorithm has been successfully validated with simulated cone beam data.  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