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   1795289篇
  免费   48040篇
  国内免费   17269篇
电工技术   49077篇
技术理论   31篇
综合类   23409篇
化学工业   316728篇
金属工艺   79328篇
机械仪表   60617篇
建筑科学   69257篇
矿业工程   20732篇
能源动力   57494篇
轻工业   134275篇
水利工程   20204篇
石油天然气   55830篇
武器工业   2362篇
无线电   224628篇
一般工业技术   318116篇
冶金工业   187928篇
原子能技术   36459篇
自动化技术   204123篇
  2022年   15812篇
  2021年   26213篇
  2020年   19633篇
  2019年   21146篇
  2018年   22482篇
  2017年   22749篇
  2016年   28373篇
  2015年   27957篇
  2014年   41780篇
  2013年   102958篇
  2012年   53277篇
  2011年   66988篇
  2010年   58149篇
  2009年   65391篇
  2008年   60144篇
  2007年   57035篇
  2006年   60758篇
  2005年   53383篇
  2004年   50681篇
  2003年   49482篇
  2002年   47912篇
  2001年   44396篇
  2000年   43241篇
  1999年   43612篇
  1998年   54188篇
  1997年   46501篇
  1996年   41780篇
  1995年   35950篇
  1994年   33176篇
  1993年   31641篇
  1992年   28491篇
  1991年   25159篇
  1990年   25017篇
  1989年   23886篇
  1988年   22212篇
  1987年   20258篇
  1986年   19583篇
  1985年   22840篇
  1984年   22843篇
  1983年   20687篇
  1982年   19562篇
  1981年   19599篇
  1980年   18189篇
  1979年   18772篇
  1978年   17943篇
  1977年   18088篇
  1976年   19783篇
  1975年   16127篇
  1974年   15651篇
  1973年   15735篇
排序方式: 共有10000条查询结果,搜索用时 31 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.
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