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   943篇
  免费   24篇
  国内免费   3篇
电工技术   16篇
化学工业   190篇
金属工艺   29篇
机械仪表   27篇
建筑科学   15篇
矿业工程   3篇
能源动力   41篇
轻工业   73篇
水利工程   7篇
石油天然气   3篇
无线电   73篇
一般工业技术   256篇
冶金工业   123篇
原子能技术   3篇
自动化技术   111篇
  2024年   4篇
  2023年   9篇
  2022年   22篇
  2021年   39篇
  2020年   36篇
  2019年   40篇
  2018年   36篇
  2017年   31篇
  2016年   24篇
  2015年   27篇
  2014年   35篇
  2013年   64篇
  2012年   30篇
  2011年   39篇
  2010年   44篇
  2009年   40篇
  2008年   30篇
  2007年   27篇
  2006年   17篇
  2005年   19篇
  2004年   11篇
  2003年   18篇
  2002年   20篇
  2001年   14篇
  2000年   11篇
  1999年   10篇
  1998年   34篇
  1997年   22篇
  1996年   16篇
  1995年   8篇
  1994年   9篇
  1993年   16篇
  1992年   7篇
  1990年   10篇
  1989年   10篇
  1988年   9篇
  1987年   10篇
  1986年   6篇
  1985年   20篇
  1984年   10篇
  1983年   9篇
  1982年   9篇
  1981年   10篇
  1980年   15篇
  1979年   9篇
  1977年   3篇
  1976年   11篇
  1975年   3篇
  1974年   3篇
  1966年   2篇
排序方式: 共有970条查询结果,搜索用时 6 毫秒
51.
52.
This study was conducted in the Tafresh area of Iran to assess the dietary patterns, time allocation, and nutritional status of rural women in relation to their participation in mixed farming activities. We selected 75 women from 40 villages by applying a stratified random-sampling technique. Cereals and grains were the major source of energy intake. According to the recommended dietary allowance (RDA) tables of India, the United States, the United Kingdom, and the Food and Agriculture Organization (FAO), the respondents seemed to have no micronutrient and energy deficiencies during the spring season. They spent most of their time and energy on household, animal husbandry, and crop farming activities. According to measurements of body mass index (BMI), the respondents were well nourished. However, despite the high level of BMI, analysis suggested a negative energy balance. Nevertheless, analysis indicated that rural women with negative energy balance spent more time and energy in mixed farming and had a higher level of participation in related activities. Hence, it is evident from the results that the physical contribution of rural women in mixed farming activities has a detrimental effect on their nutritional status, at least during some parts of the year (e.g., spring or summer). Therefore, there is a need to adjust nutritional interventions to improve the sustainability of their food intake and to develop appropriate technologies in mixed farming to alleviate their work burdens.  相似文献   
53.
-FeSi2 is an important semiconducting silicide which is being studied extensively. In this paper, we report our results of the effect of laser and laser-thermal annealing on the properties of -FeSi2. 5N purity Fe was deposited on Si substrate and was subsequently irradiated by CW and pulsed laser separately followed by thermal annealing to reduce the laser induced damage. The samples were then characterized by sheet resistance, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), optical reflectance and absorption studies. Lastly, -FeSi2/n-Si heterojunctions were fabricated and the effect of laser treatment on the junction ideality factor was investigated. All these characterizations indicated the formation of good quality -FeSi2, particularly after pulsed laser followed by thermal treatment.  相似文献   
54.
The idea of information improvement was introduced by Thiel [3]. This idea was further extended by the first author to information improvement due to 2 and N revisions and specifically states that different experimenters (a finite number) are required to proceed with given distributions P and U and are permitted to choose a suitable revision. We attempted to provide a measure of information corresponding to Theil's measure which reflected the effect of all revisions. In this paper, the authors have studied a joint characterization of information improvement of N revisions and its generalization by considering a suitable functional equation.  相似文献   
55.
Nath N  Chilkoti A 《Analytical chemistry》2004,76(18):5370-5378
The unique optical properties of noble metal nanoparticles have been used to design a label-free biosensor in a chip format. In this paper, we demonstrate that the size of gold nanoparticles significantly affects the sensitivity of the biosensor. Gold nanoparticles with diameters in the range of 12-48 nm were synthesized in solution and sensor chips were fabricated by chemisorption of these nanoparticles on amine-functionalized glass. Sensors fabricated from 39-nm-diameter gold nanoparticles exhibited maximum sensitivity to the change of the bulk refractive index and the largest "analytical volume", defined as the region around the nanoparticle within which a change in refractive index causes a change in the optical properties of the immobilized nanoparticles. The detection limit for streptavidin-biotin binding of a sensor fabricated from 39-nm-diameter nanoparticles was 20-fold better than a previously reported sensor fabricated from 13-nm-diameter gold nanoparticles. We also discuss several other factors that could improve the performance of the next generation of these immobilized metal nanoparticle sensors.  相似文献   
56.
A neutron dosemeter which offers instant read-out has been developed for nuclear criticality accidents. The system is based on gels containing emulsions of superheated dichlorodifluoromethane droplets, which vaporise into bubbles upon neutron irradiation. The expansion of these bubbles displaces an equivalent volume of gel into a graduated pipette, providing an immediate measure of the dose. Instant read-out is achieved using an array of transmissive optical sensors which consist of coupled LED emitters and phototransistor receivers. When the gel displaced in the pipette crosses the sensing region of the photomicrosensors, it generates a signal collected on a computer through a dedicated acquisition board. The performance of the device was tested during the 2002 International Accident Dosimetry Intercomparison in Valduc, France. The dosemeter was able to follow the initial dose gradient of a simulated accident, providing accurate values of neutron kerma; however, the emulsion was rapidly depleted of all its drops. A model of the depletion effects was developed and it indicates that an adequate dynamic range of the dose response can be achieved by using emulsions of smaller droplets.  相似文献   
57.
The purpose of this work is to examine the basic foundations, similarities and fundamental differences between the finite element methods (FEM) and the lumped parameter methods (LPM) of analysis for oceanic cables under hydrodynamic load conditions. The continuum method (CM) is presented as a ‘ground truth’ prior to presenting each aspect of the approximate method derivations.  相似文献   
58.
A method suitable for the stability analysis of periodic solutions of large nonlinear systems is presented. The stability behaviour is inferred from a Galerkin approximation of the associated Poincaré map. The practical value of the method is shown by applying it to the nonlinear finite element model of a large scale wind energy convertor.  相似文献   
59.
The prototype of an electronic personal neutron dosemeter based on superheated drop detectors is presented. This battery operated device comprises a neutron sensor, bubble-counting electronics and a temperature controller ensuring an optimal dose equivalent response. The neutron sensor is a 12 ml detector vial containing an emulsion of about 50,000 halocarbon-12 droplets of 100 microns diameter. The temperature controller is a low-power, solid-state device stabilising the emulsion at 31.5 degrees C by means of an etched foil heater. The microprocessor controlled counting electronics relies on a double piezo-electric transducer configuration to record bubble formation acoustically via a comparative pulse-shape analysis of ambient noise and detector signals. The performance of the dosemeter was analysed in terms of the requirements presently developed for neutron personal dosemeters. The detection threshold is about 1 microSv, while the personal dose equivalent response to neutrons in the thermal to 62 MeV range falls within a factor 1.6 of 13 bubbles per microSv.  相似文献   
60.
Pervasive Personal Computing in an Internet Suspend/Resume System   总被引:1,自引:0,他引:1  
The Internet suspend/resume model of mobile computing cuts the tight binding between PC state and PC hardware. By layering a virtual machine on distributed storage, ISR lets the VM encapsulate execution and user customization state; distributed storage then transports that state across space and time. This article explores the implications of ISR for an infrastructure-based approach to mobile computing. It reports on experiences with three versions of ISR and describes work in progress toward the OpenISR version  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