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   13913篇
  免费   1210篇
  国内免费   596篇
电工技术   765篇
技术理论   1篇
综合类   938篇
化学工业   2578篇
金属工艺   738篇
机械仪表   892篇
建筑科学   974篇
矿业工程   394篇
能源动力   406篇
轻工业   967篇
水利工程   255篇
石油天然气   709篇
武器工业   92篇
无线电   1546篇
一般工业技术   1886篇
冶金工业   633篇
原子能技术   182篇
自动化技术   1763篇
  2024年   57篇
  2023年   247篇
  2022年   349篇
  2021年   564篇
  2020年   469篇
  2019年   366篇
  2018年   434篇
  2017年   477篇
  2016年   388篇
  2015年   546篇
  2014年   673篇
  2013年   853篇
  2012年   827篇
  2011年   813篇
  2010年   799篇
  2009年   726篇
  2008年   674篇
  2007年   720篇
  2006年   727篇
  2005年   589篇
  2004年   417篇
  2003年   468篇
  2002年   546篇
  2001年   440篇
  2000年   356篇
  1999年   375篇
  1998年   323篇
  1997年   288篇
  1996年   245篇
  1995年   195篇
  1994年   164篇
  1993年   117篇
  1992年   102篇
  1991年   83篇
  1990年   62篇
  1989年   48篇
  1988年   41篇
  1987年   24篇
  1986年   31篇
  1985年   10篇
  1984年   16篇
  1983年   8篇
  1982年   8篇
  1981年   11篇
  1980年   14篇
  1979年   6篇
  1978年   3篇
  1977年   3篇
  1976年   8篇
  1959年   3篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
911.
聚丙烯纤维产品的新进展   总被引:1,自引:0,他引:1  
间述聚丙烯纤维产品的新进展,介绍了近几年来新型超细聚丙烯短程纤维,高强高模量聚丙烯纤维及新型多聚丙烯纤维的开发与应用,预计了在21世纪,聚丙烯纤维的应用会得到更大的发展。  相似文献   
912.
913.
914.
本文介绍了基于可编程控制器PLC技术的备自投装置的设计思路,通过对输入输出方式,逻辑判断条件,软件编程等方面的分析,说明该装置在中压环网柜备自投控制功能方面的实际应用,最后展望该装置的应用前景。  相似文献   
915.
Image processing requires an excellent image contrast‐enhancement technique to extract useful information invisible to the human or machine vision. Because of the histogram flattening, the widely used conventional histogram equalization image‐enhancing technique suffers from severe brightness changes, rendering it undesirable. Hence, we introduce a contrast‐enhancement dynamic histogram‐equalization algorithm method that generates better output image by preserving the input mean brightness without introducing the unfavorable side effects of checkerboard effect, artefacts, and washed‐out appearance. The first procedure of this technique is; normalizing input histogram and followed by smoothing process. Then, the break point detection process is done to divide the histogram into subhistograms before we can remap the gray level allocation. Lastly, the transformation function of each subhistogram is constructed independently. © 2011 Wiley Periodicals, Inc. Int J Imaging Syst Technol, 21, 280‐289, 2011;  相似文献   
916.
SI住宅干式内装系统架空地面施工技术是在地板下采用CP地脚螺栓支撑,架空空间内铺设机电管线。与一般的直铺地板相比,本方法地面温度相对较高,地面干燥,温度、湿度适中。在架空地板施工的基础上,实施地暖干式铺法施工。地暖干式铺法施工由基层聚苯乙烯泡沫板、中间层导热板及加热管、顶层水泥承压板组成,用尼龙胀塞与底层地面进行固定。将以前由工人在现场自由安装的管道敷设到预制好的衬板中,规整有序,同时减少施工过程中对材料的损坏。  相似文献   
917.
With increasing molybdenum ore mining, the difficult to treat ores, i.e., lower-grade and fine-disseminated ores have gradually increased in importance. Kerosene was widely used as the conventional collector of molybdenum flotation all along, but it does not adapt well to the flotation of molybdenite in difficult to treat ores. Meanwhile, kerosene has been cancelled from the manufacture catalogue in China, which makes large refineries no longer produce it, and in turn makes it difficult for a molybdenum flotation plant to purchase kerosene and makes it even harder for kerosene to keep a stable composition. Therefore, many molybdenum flotation plants began to apply diesel oil instead of kerosene as collector for molybdenite. However, the flotation results reveal that diesel oil from different manufacturers or being of different specifications from the same manufacturers has a different effect on the flotation of molybdenite, and pulp temperature has an obvious effect on the flotation efficiency of diesel oil. In pulp temperatures ranging from 10 to 30 °C, the flotation recovery of molybdenite increases with increasing high-boiling component in diesel oil. When pulp temperature is below 10 °C, the flotation recovery of molybdenite is related to the dispersibility of diesel oil, i.e., the proportion of high-boiling and low-boiling component in diesel oil. Therefore, a molybdenum flotation plant should not blindly apply diesel oil instead of kerosene as the collector for molybdenite, but should select diesel oil that is suitable for the properties of its ore. This technical note is helpful to better select the proper collector for a molybdenum flotation plant.  相似文献   
918.
BACKGROUND: In this study, a plug‐flow A2O (anaerobic/anoxic/oxic) reactor, with a working volume of 52.5 L, was employed to investigate the performance of biological nutrients removal and microbial population variations when treating low C/N ratio domestic wastewater. RESULTS: Results showed that TN removal was significantly affected by the shortage of carbon source while phosphorus removal was only slightly affected. The effluent soluble orthophosphate‐phosphorus (SOP) concentration was lower than 0.50 mg L?1 but the TN concentration was over 20 mg L?1 when the C/N ratio was 4.43. There was denitrifying phosphorus removal in the anoxic reactor and this was enhanced by increasing the volume ratio of anoxic reactor and maintaining appropriate mixed liquor recycle rate. More than 60% of the SOP were removed in anoxic reactors by denitrifying phosphorus removal when the volume ratio of anaerobic/anoxic/oxic was 1/1.4/1.6 and the mixed liquor recycle rate was 250%. The TN concentration of effluent decreased to 11.34 mg L?1 and SOP concentration was still lower than 0.5 mg L?1 in this condition. The main microorganisms found in the process by polymerase chain reaction‐denaturing gradient gel electrophoresis (PCR‐DGGE) and the functional biodiversity are discussed. CONCLUSION: Traditional design and operating parameters of A2O are not appropriate for treating low C/N wastewater. Enhancing the denitrifying phosphorus removal ratio in an A2O process is an effective way to increase the removal rate of N and P from low C/N wastewater. Copyright © 2010 Society of Chemical Industry  相似文献   
919.
The purpose of this study was to investigate in vivo biocompatibility and osteogenesis as well as degradability of the porous strontium-doped calcium polyphosphate (SCPP) scaffolds as a biomaterial for bone substitute applications. The evaluation was performed on a rabbit model over a period of 16 weeks by histology combined with image analysis, X-ray microradiography and immunohistochemistry methods. The histological and X-ray microradiographic results showed that the SCPP scaffold exhibited good biocompatibility and extensive osteoconductivity with host bone. Moreover, a significant more bone formation was observed in the SCPP group compared with that in the CPP group, especially at the initial stage after implantation. New bone volumes (NBVs) of the SCPP group determined at week 4, 8 and 16 were 14, 27 and 45%, respectively. Accordingly, NBVs of the CPP group were 10, 19 and 40%. Immunohistochemical results revealed that both the expression of collagen type I and bone morphogenetic proteins in the SCPP group were higher than that in the CPP group, which might be associated with the release of strontium ions during the implantation. In addition, during 16 weeks implantation the SCPP scaffold exhibited similar degradability with the CPP scaffold in vivo. Both scaffolds showed the greatest degradation rate for the first 4 weeks, and then the degradation rate gradually decreased. The results presented in this study demonstrated that SCPP scaffold can be considered as a biocompatible material, making it attractive for bone substitute application purposes.  相似文献   
920.
This article presents solar energy or specifically the solar photovoltaic (PV) development outlook in Malaysia. The paper first introduces the massive potential of solar energy in the country, the key players in the solar energy development and the early solar energy policies, and programmes in the country. The most important to the PV development is the Malaysia Building Integrated Photovoltaic initiative, which is presented in this paper followed by an explanation on the Feed-in Tariff recently introduced in the country to encourage new solar PV projects. The outlook for solar PV in Malaysia is optimistic and as the uptake of solar PV increases, the unit cost is coming down rapidly. Solar PV is expected to be the most competitive Renewable Energy (RE) source, with the potential to achieve grid parity for electrical power in the country in the near future, and surpassing all other REs combined by 2050.  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