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   1685275篇
  免费   35833篇
  国内免费   11036篇
电工技术   40197篇
技术理论   11篇
综合类   12864篇
化学工业   292166篇
金属工艺   70483篇
机械仪表   51071篇
建筑科学   56049篇
矿业工程   14645篇
能源动力   53226篇
轻工业   127789篇
水利工程   17739篇
石油天然气   43585篇
武器工业   852篇
无线电   210598篇
一般工业技术   307088篇
冶金工业   212494篇
原子能技术   35420篇
自动化技术   185867篇
  2021年   19346篇
  2020年   14867篇
  2019年   17098篇
  2018年   20134篇
  2017年   19904篇
  2016年   24892篇
  2015年   21266篇
  2014年   33492篇
  2013年   93904篇
  2012年   43685篇
  2011年   58092篇
  2010年   50128篇
  2009年   57746篇
  2008年   53226篇
  2007年   50223篇
  2006年   51840篇
  2005年   46269篇
  2004年   46390篇
  2003年   45646篇
  2002年   44083篇
  2001年   41507篇
  2000年   39745篇
  1999年   40210篇
  1998年   61888篇
  1997年   49984篇
  1996年   42939篇
  1995年   35684篇
  1994年   32750篇
  1993年   32306篇
  1992年   27643篇
  1991年   24659篇
  1990年   24829篇
  1989年   23829篇
  1988年   22186篇
  1987年   20356篇
  1986年   19619篇
  1985年   22860篇
  1984年   22653篇
  1983年   20574篇
  1982年   19566篇
  1981年   19737篇
  1980年   18314篇
  1979年   18688篇
  1978年   17975篇
  1977年   18298篇
  1976年   20218篇
  1975年   16103篇
  1974年   15556篇
  1973年   15684篇
  1972年   13140篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
12.
Gelatin is one of the most important multifunctional biopolymers and is widely used as an essential ingredient in food, pharmaceutical, and cosmetics. Porcine gelatin is regarded as the leading source of gelatin globally then followed by bovine gelatin. Porcine sources are favored over other sources since they are less expensive. However, porcine gelatin is religiously prohibited to be consumed by Muslims and the Jewish community. It is predicted that the global demand for gelatin will increase significantly in the future. Therefore, a sustainable source of gelatin with efficient production and free of disease transmission must be developed. The highest quality of Bovidae-based gelatin (BG) was acquired through alkaline pretreatment, which displayed excellent physicochemical and rheological properties. The utilization of mammalian- and plant-based enzyme significantly increased the gelatin yield. The emulsifying and foaming properties of BG also showed good stability when incorporated into food and pharmaceutical products. Manipulation of extraction conditions has enabled the development of custom-made gelatin with desired properties. This review highlighted the various modifications of extraction and processing methods to improve the physicochemical and functional properties of Bovidae-based gelatin. An in-depth analysis of the crucial stage of collagen breakdown is also discussed, which involved acid, alkaline, and enzyme pretreatment, respectively. In addition, the unique characteristics and primary qualities of BG including protein content, amphoteric property, gel strength, emulsifying and viscosity properties, and foaming ability were presented. Finally, the applications and prospects of BG as the preferred gelatin source globally were outlined.  相似文献   
13.
14.
15.
16.
17.
18.
Garzan oil field is located at the south east of Turkey. It is a mature oil field and the reservoir is fractured carbonate reservoir. After producing about 1% original oil in place (OOIP) reservoir pressure started to decline. Waterflooding was started in order to support reservoir pressure and also to enhance oil production in 1960. Waterflooding improved the oil recovery but after years of flooding water breakthrough at the production wells was observed. This increased the water/oil ratio at the production wells. In order to enhance oil recovery again different techniques were investigated. Chemical enhanced oil recovery (EOR) methods are gaining attention all over the world for oil recovery. Surfactant injection is an effective way for interfacial tension (IFT) reduction and wettability reversal. In this study, 31 different types of chemicals were studied to specify the effects on oil production. This paper presents solubility of surfactants in brine, IFT and contact angle measurements, imbibition tests, and lastly core flooding experiments. Most of the chemicals were incompatible with Garzan formation water, which has high divalent ion concentration. In this case, the usage of 2-propanol as co-surfactant yielded successful results for stability of the selected chemical solutions. The results of the wettability test indicated that both tested cationic and anionic surfactants altered the wettability of the carbonate rock from oil-wet to intermediate-wet. The maximum oil recovery by imbibition test was reached when core was exposed 1-ethly ionic liquid after imbibition in formation water. Also, after core flooding test, it is concluded that considerable amount of oil can be recovered from Garzan reservoir by waterflooding alone if adverse effects of natural fractures could be eliminated.  相似文献   
19.
Journal of Computer and Systems Sciences International - It is shown that the Lyapunov theorem on the distribution properties of the sum of random variables with different distribution densities...  相似文献   
20.
Multimedia Tools and Applications - Mammograms are the images used by radiologists to diagnose breast cancer. Breast cancer is one of the most common cancers in women. The early detection of breast...  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