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   57028篇
  免费   4131篇
  国内免费   886篇
电工技术   1544篇
技术理论   1篇
综合类   1396篇
化学工业   10891篇
金属工艺   1917篇
机械仪表   1986篇
建筑科学   2748篇
矿业工程   649篇
能源动力   1417篇
轻工业   6938篇
水利工程   644篇
石油天然气   1453篇
武器工业   123篇
无线电   4305篇
一般工业技术   8703篇
冶金工业   9264篇
原子能技术   430篇
自动化技术   7636篇
  2024年   159篇
  2023年   692篇
  2022年   995篇
  2021年   1763篇
  2020年   1364篇
  2019年   1402篇
  2018年   2016篇
  2017年   2094篇
  2016年   2077篇
  2015年   1939篇
  2014年   2423篇
  2013年   4099篇
  2012年   3450篇
  2011年   3399篇
  2010年   2785篇
  2009年   2685篇
  2008年   2550篇
  2007年   2375篇
  2006年   2103篇
  2005年   1820篇
  2004年   1464篇
  2003年   1310篇
  2002年   1300篇
  2001年   939篇
  2000年   898篇
  1999年   1024篇
  1998年   2897篇
  1997年   2045篇
  1996年   1450篇
  1995年   947篇
  1994年   739篇
  1993年   738篇
  1992年   372篇
  1991年   320篇
  1990年   241篇
  1989年   223篇
  1988年   243篇
  1987年   183篇
  1986年   160篇
  1985年   163篇
  1984年   155篇
  1983年   112篇
  1982年   155篇
  1981年   155篇
  1980年   160篇
  1979年   92篇
  1978年   83篇
  1977年   280篇
  1976年   630篇
  1973年   65篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
121.
Immunofluorescence microscopic observations indicated that a monoclonal antibody, Vmp 18, raised against the peptide 199-208 of murine interleukin 1 alpha, cross-reacted with an antigenic determinant of Drosophila thorax muscles. Immunoelectron microscopic analysis showed that the gold particles were mainly localized in the Z-line which is the attachment site of thin filaments from adjacent sarcomeres. On the contrary, the antibody failed to mark the Z-line in vertebrate skeletal muscle. A Western blot of total protein extract from Drosophila thorax muscles bound a protein of 43 kDa. Our observations suggest that the Vmp 18 antibody could contribute to clarify the composition of the Z-line in insect's flight muscles.  相似文献   
122.
123.
A cross-sectional study was performed to obtain risk factors for hepatitis B disease, HBsAg carriers and immunised personnel, among 2470 workers in a general hospital in Madrid, Spain. The data obtained were analyzed with multiple logistic regression to obtain beta coefficients for variables. The results of the analysis show that being a nurse or being regularly exposed to blood are the most important risk factors for hepatitis B acquisition. The length of time working at the same job activity was also a risk factor. The resulting beta coefficients allow the construction for a hepatitis non-immunised, HBsAg carrier and immunised HBV status, which can select subjects for a hepatitis B vaccination program.  相似文献   
124.
二氧化碳增油技术在孤岛油田的应用   总被引:1,自引:0,他引:1  
介绍了二氧化碳增油机理和二氧化碳增油技术在孤岛油田的应用情况。现场应用表明 ,二氧化碳非混相驱油是封闭小断块油田的有效增产措施 ,二氧化碳酸化 (压裂 )助排能起到缩短排液时间 ,保护油气层的作用  相似文献   
125.
Following up on recent studies of the Zn-rich corners of the Zn-Fe-Ni and Zn-Fe-Si ternary systems, a 450 °C isothermal section of the Zn-Fe-Ni-Si quaternary phase diagram with the Zn composition being fixed at 93 at.% was determined experimentally using optical microscopy, scanning electron microscopy (SEM) coupled with energy dispersive x-ray spectroscopy (EDS), and x-ray diffractometry (XRD). FeSi was found to be in equilibrium with almost all phases in the section, including the T, ζ, Ni-δ, NiSi2, and FeSi2 phases, as well as the liquid phase (L). Silicon solubilities in the T, ζ, and Ni-δ phases were rather limited. However, the solubilities of Fe and Zn in the NiSi2 phase, at 4.5 at.% and 7.2 at.%, respectively, were appreciable. The existence of the (L+NiSi2+Ni-δ) three-phase equilibrium state apparently prevents other Ni-Si compounds from entering equilibrium with the liquid at 450 °C. No true quaternary compound was found in the study.  相似文献   
126.
ABSTRACT: :
Soybeans ( Glycine max ) were soaked and ground to obtain soymilk. The soymilk was cooked in an open tank and held at 85 to 90 deg;C. Yuba films were picked up in 20 min intervals and dried for 20 min. Yuba films were soaked in chicken-flavor solutions (25% and 35%), and baking soda (BS) solutions (0%, 1%, 2%, and 3% BS), and cooked at 100 °C for 30 min, 60 min, and 90 min. TIA decreased (p < 0.05) with the increase of heating time and BS concentration. In vitro protein digestibility (IVPD) decreased with heating time and BS concentration (p < 0.05). Sensory characteristics were affected by flavor concentration. By using 0% BS, 25% of the chicken flavor concentration, and a short heating time method, meat-like products with low TIA, high IVPD, and good sensory characteristics were obtained.  相似文献   
127.
Generation of Technology-Independent Retargetable Analog Blocks   总被引:1,自引:0,他引:1  
This paper introduces a complete methodology for retargeting of analog cells to different sets of specifications. This methodology is technology-independent, thus allowing the migration, from one technology to another, of the circuit under retargeting. Careful integration of the device sizing and layout generation tasks via the incorporation of layout constraints during the sizing process allows to generate fully functional designs in a few minutes. The methodology is illustrated via the retargeting of a fully-differential Miller-compensated two-stage operational amplifier for a new set of specifications and two different technological processes.An erratum to this article can be found at  相似文献   
128.
郝素青 《山西建筑》2002,28(3):120-121
统计调查是统计工作的最基本环节,统计工作的质量在很大程度上取决于统计调查的质量。我国原有的统计调查方法体系已不再适应社会主义市场经济的新形势。鉴于面临着改革的新问题,论述了统计调查方法体制改革的目标模式和原则,提出了科学合理的统计调查体系,使统计工作更发适应社会主义市场经济体制的需求。  相似文献   
129.
130.
考察了渣油加氢处理催化剂制备过程中引入一种低硅铝比沸石的情况,它不仅提高催化剂的酸性,而且由于引入的分子筛孔径集中,最终使催化剂具有集中的孔分布,弥补了制备高活性催化剂采用混捏法的不足,制备出来的催化剂性能更优异。  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