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   48868篇
  免费   2756篇
  国内免费   153篇
电工技术   706篇
综合类   64篇
化学工业   10131篇
金属工艺   2135篇
机械仪表   3239篇
建筑科学   1097篇
矿业工程   25篇
能源动力   2111篇
轻工业   3885篇
水利工程   269篇
石油天然气   87篇
武器工业   2篇
无线电   7808篇
一般工业技术   10657篇
冶金工业   3880篇
原子能技术   658篇
自动化技术   5023篇
  2024年   24篇
  2023年   537篇
  2022年   435篇
  2021年   1469篇
  2020年   1069篇
  2019年   1175篇
  2018年   1430篇
  2017年   1411篇
  2016年   1750篇
  2015年   1294篇
  2014年   2088篇
  2013年   3006篇
  2012年   3268篇
  2011年   3890篇
  2010年   2814篇
  2009年   2921篇
  2008年   2811篇
  2007年   2185篇
  2006年   2031篇
  2005年   1723篇
  2004年   1571篇
  2003年   1513篇
  2002年   1329篇
  2001年   1134篇
  2000年   996篇
  1999年   928篇
  1998年   1557篇
  1997年   991篇
  1996年   803篇
  1995年   557篇
  1994年   460篇
  1993年   406篇
  1992年   290篇
  1991年   274篇
  1990年   258篇
  1989年   241篇
  1988年   205篇
  1987年   168篇
  1986年   119篇
  1985年   115篇
  1984年   91篇
  1983年   61篇
  1982年   38篇
  1981年   39篇
  1980年   30篇
  1979年   30篇
  1978年   30篇
  1977年   38篇
  1976年   61篇
  1973年   20篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
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   
62.
63.
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   
64.
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   
65.
66.
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   
67.
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   
68.
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   
69.
This letter presents a small‐sized, high‐power single‐pole double‐throw (SPDT) switch with defected ground structure (DGS) for wireless broadband Internet application. To reduce the circuit size by using a slow‐wave characteristic, the DGS is used for the quarter‐wave (°/4) transmission line of the switch. To secure a high degree of isolation, the switch with DGS is composed of shunt‐connected PIN diodes. It shows an insertion loss of 0.8 dB, an isolation of 50 dB or more, and power capability of at least 50 W at 2.3 GHz. The switch shows very similar performance to the conventional shunt‐type switch, but the circuit size is reduced by about 50% simply with the use of DGS patterns.  相似文献   
70.
The adverse effect of nitrate on the phosphate release rate in the anaerobic phase was observed and was hardly explainable with conventional EBPR process models. Four possible mechanisms were proposed including substrate competition, reduced fermentation, parallel reaction and sequential reaction. Batch experiments were designed and conducted to identify the dominant mechanism. Results showed that the sequential reaction was the only possible mechanism where only denitrification occurred if any nitrate existed in the anaerobic phase. Then the phosphate release following after the nitrate was completely removed. Nitrate inhibition effect was added into the PHA storage rate to incorporate the sequential reaction in the conventional ASM3 plus EAWAG bio-P module (ASM3 + P). Nitrate inhibition coefficient, K(I,NO,PAO) was found to be as low as 0.05 mg/L. This correlated well with experimental observation where no also meant that the anaerobic compartment of a continuous flow reactor could be seriously affected by the residual nitrate contained in the sludge recycle flow. This phenomenon caused overestimation of the phosphate uptake rate and consequently underestimation of PO4(3-) -P concentration. This problem was resolved by incorporation of a nitrate inhibition term in the ASM3 + P for more accurate simulation of the EBPR process.  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