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   183211篇
  免费   9049篇
  国内免费   3733篇
电工技术   4744篇
技术理论   1篇
综合类   6311篇
化学工业   29544篇
金属工艺   9394篇
机械仪表   9039篇
建筑科学   6950篇
矿业工程   1877篇
能源动力   4411篇
轻工业   12672篇
水利工程   2673篇
石油天然气   2447篇
武器工业   468篇
无线电   23492篇
一般工业技术   32678篇
冶金工业   9247篇
原子能技术   1545篇
自动化技术   38500篇
  2024年   248篇
  2023年   1301篇
  2022年   2459篇
  2021年   3550篇
  2020年   2595篇
  2019年   2491篇
  2018年   16829篇
  2017年   15868篇
  2016年   12795篇
  2015年   4034篇
  2014年   5043篇
  2013年   6768篇
  2012年   10100篇
  2011年   17169篇
  2010年   14597篇
  2009年   12180篇
  2008年   13022篇
  2007年   13241篇
  2006年   5504篇
  2005年   5614篇
  2004年   4669篇
  2003年   4238篇
  2002年   3348篇
  2001年   2522篇
  2000年   2173篇
  1999年   1789篇
  1998年   2419篇
  1997年   1619篇
  1996年   1310篇
  1995年   898篇
  1994年   762篇
  1993年   698篇
  1992年   485篇
  1991年   462篇
  1990年   385篇
  1989年   340篇
  1988年   300篇
  1987年   252篇
  1986年   200篇
  1985年   155篇
  1984年   134篇
  1983年   92篇
  1982年   63篇
  1981年   81篇
  1979年   61篇
  1978年   65篇
  1977年   88篇
  1976年   117篇
  1955年   63篇
  1954年   68篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
111.
Metals and Materials International - This study investigated the influence of the initial grain size on the plastic deformation and tunnel defects that occurred from friction stir welding of...  相似文献   
112.
113.
Metallurgical and Materials Transactions B - The concentration and chemical bonding state of carbon in direct-reduced iron (DRI) might affect DRI melting temperature and rate. The effects of carbon...  相似文献   
114.
We study a maritime inventory routing problem, in which shipments between production and consumption nodes are carried out by a fleet of vessels. The vessels have specific capacities and can be chartered under different agreements. The inventory levels of all consumption nodes and some production nodes should be maintained within specified bounds; for the remaining production nodes, orders should be picked up within pre-defined time windows. We propose a discrete-time mixed-integer programming model. In the face of new information and uncertainty, this optimization model has to be re-solved, as the horizon is rolled forward. We discuss how to account for different sources of uncertainty. We present a rolling-horizon reoptimization framework that allows us to study different policies that impact the quality of the implemented solution, so we can identify the optimal set of policies.  相似文献   
115.
The effect of biochar substituted for anthracite as reductant on magnetizing-roasting pyrite cinder was investigated.The key of magnetizing-roasting is the gasification reaction between reductants and CO2.Since biochar could react with CO2 more rapidly at lower temperature,the reactivity of biochar is better than that of anthracite.The gasification of biochar could produce reducing condition ofφCO/(φCO+φCO2)about 10%-20% between 700-800 ℃,which is in accord with the atmosphere and temperature of Fe2O3 reduction.So it is beneficial to the reduction of iron mineral of pyrite cinder.Compared with anthracite,biochar could decrease the roasting temperature from825 to 750 ℃ and roasting time from 20 to 15min,which shows that a better effect of magnetization could be obtained in the condition of lower temperature and shorter time.Using biochar as reductant,iron concentrate extracted from pyrite cinder as about 64%iron grade could be produced,and the recovery is over 90% under the condition of above 90% grinding particle less than 0.045 mm and magnetic intensity of 0.124-0.194 T.  相似文献   
116.
We present a distribution‐free tabular cumulative sum chart for monitoring the variability of an autocorrelated process. A quantity known as the asymptotic variance parameter is employed as a measure of the variability, and a distribution‐free tabular cumulative sum chart is applied to variance estimates calculated from batches of nonoverlapping samples. The proposed chart is applicable to a stationary process with a general marginal distribution and a general autocorrelation structure. It also determines control limits analytically without trial‐and‐error simulations. The performance of the proposed chart is tested on stationary processes with both normal and nonnormal marginals with various autocorrelation structures. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   
117.
118.
Journal of Mechanical Science and Technology - In the industry, globe valves, which are commonly used to precise control the flow rate along with opening and closing flow in pipes, are technically...  相似文献   
119.
Vegetable soup (VS), a plant-based functional food, has been used as a traditional folk medicine and is attracting attention for its ability to enhance the immune response. β-Glucan, a well-established and effective immunomodulator, has synergistic effects when used in combination with some bioactive compounds. In the present study, we aimed to evaluate the synergistic immunomodulatory effects of the combination of VS and β-glucan on macrophage-mediated immune responses. β-Glucan was demonstrated to synergistically enhance the VS-stimulated immune response, including the production of interleukin-6, tumor necrosis factor-α, and nitric oxide, mainly through the mitogen-activated protein kinase pathway in macrophages. In addition, this combination has the potential for further development in functional foods with immune-enhancing activity.Supplementary InformationThe online version contains supplementary material available at 10.1007/s10068-021-00888-x.  相似文献   
120.
Food Science and Biotechnology - St. Paul’s Wort (Siegesbeckia orientalis L.) confers anti-oxidative, anti-inflammatory, anti-allergic, anti-infertility, and immunosuppressive properties....  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