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   11429篇
  免费   855篇
  国内免费   351篇
电工技术   53篇
综合类   303篇
化学工业   989篇
金属工艺   129篇
机械仪表   242篇
建筑科学   98篇
矿业工程   7篇
能源动力   139篇
轻工业   5499篇
水利工程   41篇
石油天然气   478篇
武器工业   18篇
无线电   613篇
一般工业技术   3631篇
冶金工业   56篇
原子能技术   36篇
自动化技术   303篇
  2024年   122篇
  2023年   278篇
  2022年   345篇
  2021年   531篇
  2020年   497篇
  2019年   432篇
  2018年   426篇
  2017年   572篇
  2016年   495篇
  2015年   448篇
  2014年   624篇
  2013年   726篇
  2012年   750篇
  2011年   810篇
  2010年   632篇
  2009年   764篇
  2008年   420篇
  2007年   598篇
  2006年   587篇
  2005年   383篇
  2004年   421篇
  2003年   307篇
  2002年   268篇
  2001年   187篇
  2000年   146篇
  1999年   153篇
  1998年   113篇
  1997年   81篇
  1996年   80篇
  1995年   55篇
  1994年   63篇
  1993年   65篇
  1992年   68篇
  1991年   51篇
  1990年   46篇
  1989年   40篇
  1988年   13篇
  1987年   13篇
  1986年   3篇
  1985年   10篇
  1984年   4篇
  1983年   1篇
  1982年   1篇
  1980年   4篇
  1962年   1篇
  1959年   1篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
A panel of experienced assessors was used to test the effect of irradiation at 2.5kGy (250krad) on the sensory quality of 1-day and 21-day-old turkey breast fillets stored at 1°C in either oxygen-permeable polythene or an oxygen-impermeable barrier film. In the application of Free Choice Profiling and Generalized Procrustes Analysis, assessors used their own terms to describe the appearance, odour and flavour of the samples.
The irradiated samples showed negligible growth of micro-organisms across 21 days of storage. Radiation treatment resulted in an intense pink colour in the raw and cooked samples, which was maintained during storage in oxygen-impermeable film, but decreased in samples exposed to oxygen during storage. Radiation also produced a set of unpleasant raw odour notes variously described as sour, rancid, mature, bad meat or putrid in the samples stored in oxygen-impermeable film. These notes were unlike the sulphurous notes previously associated with protein denaturation in irradiated chicken and were apparently distinct from the odour notes that developed in corresponding non-irradiated samples.  相似文献   
52.
Reduced ascorbic acid (RAA) content, total chlorophyll and green color retention, enzyme activities and texture changes were followed in broccoli spears packaged in polymeric film and nonpackaged during 96 hr storage (10°C). Concentrations within packages monitored by gas chromatography were (CO2,) 8% and (02) 10%. RAA retention, moisture content, total chlorophyll and color retention were greater in packaged broccoli. No differences were found between packaged and nonpackaged broccoli for ascorbate oxidase and peroxidase activities, or texture.  相似文献   
53.
We investigated pasteurization and storage of blue crabmeat in steel cans, aluminum cans, plastic cans, nonbarrier pouches, and barrier pouches. Fresh meat was packed in copolymer polyethylene/polypro-pylene cups, Saran® over-wrapped or vacuum skin packaged polystyrene trays, and nonbarrier pouches. Meat pasteurized in plastic and aluminum cans had better sensory and microbiological quality and longer shelf life than meat packed in steel cans. Oxygen-barrier pouches had the lowest quality and shortest shelf life. Nonbarrier pouches had product with quality similar to meat in steel cans, but with an extended shelf life. No packaging materials improved the microbiological shelf life of freshly cooked meat. Vacuum skin packaging resulted in improved sensory qualities of freshly cooked and picked meat.  相似文献   
54.
Food supply chains are increasingly complex and dynamic due to (i) increasing product proliferation to serve ever diversifying and globalising markets as a form of mass customisation with resulting global flows of raw materials, ingredients and products, and (ii) the need to satisfy changing and variable consumer and governmental demands with respect to food safety, animal welfare, and environmental impact. Transparency in the food supply chain is essential to guarantee food quality and provenance to all users of food and food products. Intensified information exchange and integrated information systems involving all chain actors are needed to achieve transparency with respect to a multitude of food properties.In this paper, specific challenges of food supply chains are highlighted. Major elements are addressed that support transparency to consumers, the government and food companies, which are considered the claimants of transparency. Elements considered to be enablers of transparency are governance mechanisms, quality and safety standards and information exchange. The paper specifies these transparency claimants and enablers for food supply chains and identifies major information system functions and information technology applications needed to comply with transparency demands. It thereby provides a framework for transparency analysis in food supply chains.  相似文献   
55.
A unique substrate MCPM (Mitsubishi Copper Polyimide Metal-base) technology has been developed by applying our basic copper/polyimide technology.1 This new substrate technology MCPM is suited for a high-density, multi-layer, multi-chip, high-power module/package, such as used for a computer. The new MCPM was processed using a copper metal base (110 × 110 mm), full copper system (all layers) with 50-μm fine lines. As for pad metallizations for the IC assembly, we evaluated both Ni/Au for chip and wire ICs and solder for TAB ICs. The total number of assembled ICs is 25. To improve the thermal dispersion, copper thermal vias are simultaneously formed by electro-plating. This thermal via is located between the IC chip and copper metal base, and promotes heat dispersion. We employed one large thermal via (4.5 mm?) and four small vias (1.0 mm?) for each IC pad. The effect of thermal vias and/or base metal is simulated by a computer analysis and compared with an alumina base substrate. The results show that the thermal vias are effective at lowering the temperature difference between the IC and base substrate, and also lowering the temperature rise of the IC chip. We also evaluated the substrate’s reliability by adhesion test, pressure cooker test, etc.  相似文献   
56.
The shear strength and aging characteristics of 63Sn–37Pb solder bumps were characterized with variation in solder ball and UBM pad sizes. The shear strength increased with shorter effective crack size,a effs which was determined with the solder ball and pad sizes. The shear strength of the solder bumps on Au/Ni/Cu and Ni/Cu did not change significantly with reflow time. Substantial decrease in the shear strength occurred for the solder bumps formed on Au/Ni/Cu with aging treatment, and the shear strength after aging was also related to the bump shape which was determined with the solder ball and pad sizes.  相似文献   
57.
赵小艳  陈良伦  何清玉 《安徽化工》2004,30(6):13-15,18
说明了水基传送带润滑剂的作用机理、性能要求,详细介绍了现有的水基传送带润滑剂的特点,并简单介绍了水基传送带润滑剂的发展前景和趋势。  相似文献   
58.
塑料在包装领域有着广泛的应用,其中聚酯(PET)性能优良,应用领域不断扩大。介绍了塑料包装不断通现的新技术,以及塑料包装环保问题的几点思路。  相似文献   
59.
The electrodiffusion technique was performed in order to investigate the shear rate on a scraped surface heat exchanger. Microelectrodes were placed inside: the walls of the outer cylinder; the inlet and outlet bowls; the rotor and the blades. Highly viscous Newtonian fluid (Emkarox HV45 solutions) and non-Newtonian model fluid (aqueous solutions of CMC) were used. The electrodiffusion method allowed us to measure wall shear rates. Maximum shear rate was observed at the scraping surface and caused by blades scraping, high shear rate was also measured on the leading edge of the blades. In the other parts of the exchanger, shear rate remained low but the development of Taylor vortices completely modified the scraped surface heat exchangers behaviour inside the surface of the bowls. A dimensionless representation of the friction factor was established for the inner and outer wall surface of the exchanger.  相似文献   
60.
浅论食品化学污染及其防治策略   总被引:2,自引:0,他引:2  
魏林 《贵州化工》2006,31(2):30-33
分析了食品化学污染的主要途径,以及这些污染物对人体健康的危害性,对食品化学污染的防治策略进行了探讨。  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