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   1427篇
  免费   65篇
  国内免费   9篇
电工技术   69篇
综合类   3篇
化学工业   321篇
金属工艺   34篇
机械仪表   32篇
建筑科学   44篇
矿业工程   1篇
能源动力   60篇
轻工业   160篇
水利工程   7篇
石油天然气   3篇
无线电   144篇
一般工业技术   294篇
冶金工业   140篇
原子能技术   45篇
自动化技术   144篇
  2023年   7篇
  2022年   32篇
  2021年   58篇
  2020年   25篇
  2019年   41篇
  2018年   34篇
  2017年   26篇
  2016年   48篇
  2015年   42篇
  2014年   64篇
  2013年   88篇
  2012年   92篇
  2011年   130篇
  2010年   81篇
  2009年   81篇
  2008年   90篇
  2007年   70篇
  2006年   40篇
  2005年   46篇
  2004年   42篇
  2003年   36篇
  2002年   28篇
  2001年   29篇
  2000年   14篇
  1999年   11篇
  1998年   69篇
  1997年   41篇
  1996年   30篇
  1995年   12篇
  1994年   16篇
  1993年   16篇
  1992年   8篇
  1991年   8篇
  1990年   3篇
  1989年   4篇
  1988年   5篇
  1987年   2篇
  1986年   7篇
  1985年   4篇
  1984年   2篇
  1983年   6篇
  1982年   1篇
  1981年   2篇
  1980年   1篇
  1976年   5篇
  1975年   3篇
  1972年   1篇
排序方式: 共有1501条查询结果,搜索用时 15 毫秒
1.
The present paper includes experimental and analytical data on the fracture properties of a nickel-iron superalloy, a ferromagnetic austenite, at 4 K in magnetic fields of 0 and 6 T. The tensile, notch tensile and small punch tests are employed. A finite element analysis is also performed to convert the experimentally measured load-displacement data into useful engineering information. To interpret the results we review the available theory of the influence of magnetic field on the stress intensity factor for a crack in ferromagnetic materials.  相似文献   
2.
A 640-Gb/s high-speed ATM switching system that is based on the technologies of advanced MCM-C, 0.25-μm CMOS, and optical wavelength-division-multiplexing (WDM) interconnection is fabricated for future broadband backbone networks. A 40-layer, 160×114 mm ceramic MCM forms the basic ATM switch module with 80-Gb/s throughput. It consists of 8 advanced 0.25-μm CMOS LSIs and 32 I/O bipolar LSIs. The MCM has a 7-layer high-speed signal line structure having 50-Ω strip lines, high-speed signal lines, and 33 power supply layers formed using 50-μm thick ceramic layers to achieve high capacity. A uniquely structured closed-loop-type liquid cooling system for the MCM is used to cope with its high power dissipation of 230 W. A three-stage ATM switch is made using the optical WDM interconnection between high-performance MCMs. For WDM interconnection, newly developed compact 10-Gb/s, 8-WDM optical transmitter and receiver modules are used. These modules are each only 80×120×20 mm and dissipate 9.65 W and 22.5 W, respectively. They have a special chassis for cooling, which contains high-performance heat-conductive plates and micro-fans. An optical WDM router based on an arrayed waveguide router is used for mesh interconnection of boards. The optical WDM interconnect has 640-Gb/s throughput and simple interconnection  相似文献   
3.
We present a local Dissemination of EPIC, a project which has been devised to support health and social primary care by an information system. One key point of the EPIC project was a standardization effort at European level, providing a standardized basis for the management system based on client needs for planning and manpower control. Whilst EPIC has been designed as a general community information system, the main EPIC applications focus is on the care of the elderly. Savona is a middle size Italian town with a high percentage of elderly people and has already had an experience of integration of health and social care within an Italian project. It has therefore been regarded as a suitable site for the dissemination of EPIC. The EPIC application solved some of the information problems which emerged during the validation of the previous Italian project, such as the definition of the requirements; the collection, processing and retrieval of the clinical/social data; the definition of responsibilities and relations of the operators.  相似文献   
4.
The temperature dependence of luminescence from a long-lasting phosphor (LLP), SrAl2O4 : Eu2+,Dy3+, exposed to ionizing radiation has been measured to understand the LLP luminescence mechanism. Evaluation of the decay constants of the LLP exposed to -, β- or γ-rays at temperatures from 200 to 390 K showed that the decay constant is divided into four components ranging from 10−4 to 10−1 s−1 with activation energies of 0.02–0.35 eV.

Total luminous intensity from the LLP with changing irradiation temperature has its maximum value around the room temperature. Irradiation at elevated temperature (390 K) has the total luminescence pattern with monotonous decrease as temperature rises. As a result of evaluating the temperature dependence of luminescence, the luminescence mechanism is considered as follows:

 

Author Keywords: Radiation detection; Long-lasting phosphor; Luminescence; Temperature dependence; Fade-out effect  相似文献   

5.
According to the definition of the ICD-10 or DSM-III, sexual dysfunction is not caused by organic disorder or disease, and psychogenic. But, the patient who is suffered from sexual dysfunction caused by organic disorder or disease, has many psycho-social problems. So, in this article, all types of sexual dysfunction are subjected. Especially sexual hypofunction is mentioned. And the new type of sexual dysfunctions such as computer sex are also explained. Sex therapy of the Masters and Johnson method and the new sex therapy of Kaplan, H. are explained.  相似文献   
6.
The light scattering from the spherulites of polyethylene terephthalate grown near the glass transition temperature has been investigated. The Hv scattering profiles can be reproduced by the sum of the ideal spherulite scattering with the distribution of spherulite radius and the isotropic scattering from randomly oriented crystallites. The ratio of optical anisotropies in the isotropic scattering to the ideal spherulite scattering is obtained by the method established to eliminate the effects of the number density of spherulites and the coefficient depending on the experimental conditions. It is found that the anisotropy ratio is almost independent of the crystallization time and of temperature above 106 °C, while it is larger at a crystallization temperature of 103 °C. The spherulitic structure is discussed in terms of the anisotropy ratio.  相似文献   
7.
Double‐network (DN) hydrogels with high mechanical strength have been synthesized using the natural polymers bacterial cellulose (BC) and gelatin. As‐prepared BC contains 90 % water that can easily be squeezed out, with no more recovery in its swelling property. Gelatin gel is brittle and is easily broken into fragments under a modest compression. In contrast, the fracture strength and elastic modulus of a BC–gelatin DN gel under compressive stress are on the order of megapascals, which are several orders of magnitude higher than those of gelatin gel, and almost equivalent to those of articular cartilage. A similar enhancement in the mechanical strength was also observed for the combination of BC with polysaccharides, such as sodium alginate, gellan gum, and ι‐carrageenan.  相似文献   
8.
The dynamic characteristics involved in the loading process in the ocean environment are extremely complicated and difficult for exact evaluation. In this paper, parametric studies are presented to assess the influence of uncertainties associated with various assumptions and approximations, involved in modelling the dynamic loading processes of ocean environment, for the evaluation of dynamic response of offshore structures. These uncertainties are represented by the inertia coefficient and the drag coefficient of the Morison equation which defines the wave forcing function, the mean height of the input sea waves and the shear wave velocity of the soil. The results show that the effects of uncertainties are closely related to the natural frequency of the structure and the predominant frequency of the wave force. These uncertainties, except the variation in the shear wave velocity in the soil, contribute significantly to the dynamic response and the first passage probability evaluation of the offshore structure systems.  相似文献   
9.
To investigate whether tachykinins are released in the airways in response to stimulation of the esophagus, we studied the airway plasma extravasation induced by intraesophageal HCl in the presence or absence of neutral endopeptidase inhibitor phosphoramidon and NK1-receptor antagonist FK-888 in anesthetized guinea pigs. The airway plasma leakage was evaluated by measuring extravasated Evans blue dye in the animals pretreated with propranolol and atropine. Infusion of 1 N HCl into the esophagus significantly increased plasma extravasation in the trachea. Phosphoramidon significantly potentiated plasma extravasation in the trachea and main bronchi, whereas FK-888 significantly inhibited that extravasation in a dose-related manner. In the capsaicin-treated animals, airway plasma extravasation was completely inhibited even in the presence of phosphoramidon. Tracheal plasma extravasation potentiated by phosphoramidon was significantly inhibited in the bilateral vagotomized animals. These results suggest that 1) tachykinin-like substances are released to cause plasma extravasation in the airways as a result of intraesophageal HCl stimulation and 2) there are neural pathways communicating between the esophagus and airways, including the vagus nerve.  相似文献   
10.
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