首页 | 官方网站   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   707篇
  免费   23篇
  国内免费   1篇
工业技术   731篇
  2023年   10篇
  2022年   17篇
  2021年   36篇
  2020年   21篇
  2019年   21篇
  2018年   27篇
  2017年   12篇
  2016年   14篇
  2015年   13篇
  2014年   25篇
  2013年   26篇
  2012年   21篇
  2011年   26篇
  2010年   24篇
  2009年   14篇
  2008年   25篇
  2007年   11篇
  2006年   13篇
  2005年   5篇
  2004年   6篇
  2003年   10篇
  2002年   6篇
  2001年   3篇
  2000年   2篇
  1999年   16篇
  1998年   65篇
  1997年   44篇
  1996年   44篇
  1995年   29篇
  1994年   23篇
  1993年   20篇
  1992年   2篇
  1991年   9篇
  1990年   8篇
  1989年   7篇
  1988年   4篇
  1987年   2篇
  1986年   6篇
  1985年   3篇
  1984年   3篇
  1983年   6篇
  1982年   5篇
  1981年   7篇
  1980年   9篇
  1979年   2篇
  1978年   3篇
  1977年   6篇
  1976年   10篇
  1975年   4篇
  1974年   3篇
排序方式: 共有731条查询结果,搜索用时 0 毫秒
31.
The building-cube method (BCM) is a new generation algorithm for CFD simulations. The basic idea of BCM is to simplify the algorithm in all stages of flow computation to achieve large-scale simulations. Calculation of a pressure field using the Successive Over Relaxation (SOR) method consumes most of the total execution time required for BCM. In this paper, effective implementations on modern vector and scalar processors are investigated. NEC SX-9 and Intel Nehalem-EX are the latest vector and scalar processors. Those processors have much higher peak performances than their previous-generation processors. However, their memory bandwidth improvement cannot catch up with the performance improvement of processors. This is the so-called memory wall problem. In our paper, we discuss optimization techniques for implementation of the SOR method based on architectural characteristics of these modern processors, and evaluate their effects on the sustained performances of these processors for BCM.  相似文献   
32.
Attachment between parent and child plays a crucial role in the healthy development of the child. Accordingly disturbances in parental bonding will be linked with the development of mental disorders later in life. The present study examines the relationship between parental bonding and mental health in healthy adolescents. Participants were 847 Israeli high school students who completed the Parental Bonding Instrument (PBI), the Brief Symptom Inventory (BSI), the General Well-Being (GWB), the Perceived Social Support (PSS), and the Social Desirability scale (SDS). In general, Israeli adolescents reported more parental care and less control than did Australian adolescents and adults. Female subjects reported more maternal care than did males. Subjects who reported high care and low control (optimal bonding) reported less distress, better general well-being and better social support that did all other groups. In contrast, those who reported low care and high control (affectionless control bonding) had the highest BSI scores and the lowest GWB and PSS scores. These results are in line with Bowlby's theory of attachment. They also show that specific configuration of parental bonding are linked with distress and isolation in adolescents.  相似文献   
33.
PURPOSE: The aim of this study was to determine the concentration of interleukin-1 alpha in human embryo culture medium with or without oviductal cell coculture and to correlate the interleukin-1 alpha levels with pregnancy. METHODS: Culture media from 32 in vitro fertilization and embryo transfer cycles were assayed for interleukin-1 alpha by immunoassay technique. Human embryos were cultured in Earles' balanced salt solution supplemented with 15% preovulatory serum (sEBSS) in 16 of these cycles, while embryos in the rest of the cycles were cocultured with human oviductal cells in sEBSS. RESULTS: Both sEBSS and spent sEBSS after embryo culture contained low or undetectable levels of interleukin-1 alpha in the pregnant and nonpregnant cycles. On the other hand, oviductal cells significantly increased the amount of interleukin-1 alpha immunoreactivity in the conventional culture medium or coculture medium (P < 0.001, Mann-Whitney rank sum test). The concentrations of interleukin-1 alpha in the spent sEBSS after oviductal cell culture and after coculture with human embryos were 1.5 +/- 1.0 and 1.3 +/- 0.9 pg/ml, respectively. There was no difference in the interleukin-1 alpha concentration between the pregnant and the nonpregnant coculture cycles. CONCLUSIONS: These data showed that human oviductal cells produced interleukin-1 alpha immunoreactivity in a coculture system. However, this production could not be used as a marker for successful embryo implantation.  相似文献   
34.
BACKGROUND: The effect of saccarose supplementation provided through drinking water during feed withdrawal on meat and liver colour was investigated in a total of 50 broilers (five floor pens with 10 broilers) at 43 days. Treatments consisted of: (1) full‐fed control broilers fed the standard broiler diet and water for the full 10 h (control); (2) fasted broilers receiving only water (FW); (3) 1 g (0.01SW); (4) 2 g (0.02SW); and (5) 3 g (0.03SW) saccarose L?1 supplemented water for the 10 h. The CIE colour values representing lightness (L*), redness (a*), and yellowness (b*) were measured on raw livers, breast and thigh meats. RESULTS: Full‐fed broilers had lower dressing percentage, higher abdominal fat and liver yield and lighter thigh meat coloration than the FW birds (P < 0.05). The 0.02SW and 0.03SW resulted in live shrinks that were lower (P < 0.05) than those found in FW broilers. The 0.02SW and 0.03SW resulted in liver colours that were lighter than those found in FW and 0.01SW birds but darker than from control birds (P < 0.05). CONCLUSION: It was concluded that saccarose supplementation during feed withdrawal appears to have a measurable impact on live shrink, and lightness of liver and thigh meat colour in broilers. Copyright © 2007 Society of Chemical Industry  相似文献   
35.
36.
This paper presents synthesis, photophysical, electrochemical, thermal and morphological properties of Schiff bases containing various side-group substitutions and polyurethanes (PUs) containing azomethine linkage. Morphological properties of PUs containing azomethine bonding were investigated by scanning electron microscopy (SEM). SEM images showed that PU containing azomethine consist of semi-crystalline particles. Thermal transitions in PUs containing azomethine units were studied using DSC. The obtained DSC curves showed that PUs containing azomethine are semi-crystalline materials due to they contain both crystallization and melting peaks. Electrochemical properties also investigated by using cyclic voltammetry (CV). According to the cyclic voltommagrams and CV data, PUs containing azomethine have below 2.0 eV electrochemical band gap.  相似文献   
37.
The development of chemical sensors and biosensors over several decades has been investigated resulting in novel and very interesting sensor devices with great promise for many areas of applications including food technology. The incorporation of such sensors into the food packaging technology has resulted what we call smart or intelligent packaging. These are truly integrated and interdisciplinary systems that invoke expertise from the fields of chemistry, biochemistry, physics and electronics as well as food science and technology. Smart packaging utilises chemical sensor or biosensor to monitor the quality & safety of food from the producers to the costumers. This technology can result in a variety of sensor designs that are suitable for monitoring of food quality and safety, such as freshness, pathogens, leakage, carbon dioxide, oxygen, pH, time or temperature. Thus, this technology is needed as on-line quality control and safety in term of consumers, authorities and food producers, and has great potential in the development of new sensing systems integrated in the food packaging, which are beyond the existing conventional technologies, like control of weight, volume, colour and appearance.  相似文献   
38.
The aim of this study was to investigate the effects of impregnation with Imersol-Aqua on the compression strength of some solid wood materials. For this aim, Oriental beech (Fagus orientalis Lipsky), European oak (Quercus petrea Liebl.), Scotch pine (Pinus sylvestris Lipsky), Uludag fir (Abies Bornmülleriana Mattf.), Oriental spruce (Picea orientalis Lipsky) and Lombardy poplar (Populus nigra Lipsky) wood samples were prepared according to TS 2595 and impregnated with Imersol-Aqua, commonly being used in construction wood materials by the method of short, medium and long-term of dipping according to ASTM D 1413 and producers’ definition. After the impregnation process, compression strength was measured according to TS 2595. Consequently, among the non-impregnated wood materials, the highest compression strength was obtained in beech and pine samples. Compression strength at this situation from the highest to lowest can be enumerated beech, pine, oak, spruce, fir and poplar. With regard to the impregnation period, the sequence form the highest to lowest was as long-term, medium-term and short-term dipping. In the interaction of wood material and impregnation period, the highest compression strength values were obtained in Scotch pine (71.220 N mm−2) impregnated with long-term dipping method whereas the lowest in Lombardy poplar (35.710 N mm−2) impregnated with short-term dipping method.

In consequence, in the massive constructions and furniture elements that the compression strength after the impregnation is of great concern, long-term impregnation of solid wood material could be recommended.  相似文献   

39.
40.
This paper presents a methodology of a design optimization technique that can be useful in assessing the best configuration of a finned‐tube evaporator, using a thermoeconomic approach. The assessment has been carried out on a direct expansion finned‐tube evaporator of a vapor compression cycle for a roof‐top bus air‐conditioning (AC) system at a specified cooling capacity. The methodology has been conducted by studying the effect of some operational and geometrical design parameters for the evaporator on the entire cycle exergy destruction or irreversibility, AC system coefficient of performance (COP), and total annual cost. The heat exchangers for the bus AC system are featured by a very compact frontal area due to the stringent space limitations and structure standard for the system installation. Therefore, the current study also takes in its account the effect of the variation of the design parameters on the evaporator frontal area. The irreversibility due to heat transfer across the stream‐to‐stream temperature difference and due to frictional pressure drops is calculated as a function of the design parameters. A cost function is introduced, defined as the sum of two contributions, the investment expense of the evaporator material and the system compressor, and the operational expense of AC system that is usually driven by an auxiliary engine or coupled with the main bus engine. The optimal trade‐off between investment and operating cost is, therefore, investigated. A numerical example is discussed, in which a comparison between the commercial evaporator design and optimal design configuration has been presented in terms of the system COP and evaporator material cost. The results show that a significant improvement can be obtained for the optimal evaporator design compared with that of the commercial finned‐tube evaporator that is designed based on the conventional values of the design parameters. Copyright © 2007 John Wiley & Sons, Ltd.  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-23

京公网安备 11010802026262号