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   276528篇
  免费   4256篇
  国内免费   866篇
电工技术   5342篇
综合类   352篇
化学工业   40433篇
金属工艺   10657篇
机械仪表   8856篇
建筑科学   6985篇
矿业工程   1178篇
能源动力   6960篇
轻工业   24232篇
水利工程   2711篇
石油天然气   3971篇
武器工业   68篇
无线电   36004篇
一般工业技术   53000篇
冶金工业   49636篇
原子能技术   5515篇
自动化技术   25750篇
  2021年   2348篇
  2019年   2277篇
  2018年   3810篇
  2017年   3881篇
  2016年   4106篇
  2015年   2628篇
  2014年   4492篇
  2013年   12406篇
  2012年   7284篇
  2011年   9908篇
  2010年   7706篇
  2009年   8599篇
  2008年   9509篇
  2007年   9402篇
  2006年   8466篇
  2005年   7795篇
  2004年   7415篇
  2003年   7209篇
  2002年   6839篇
  2001年   6770篇
  2000年   6435篇
  1999年   6546篇
  1998年   14575篇
  1997年   10530篇
  1996年   8398篇
  1995年   6667篇
  1994年   5955篇
  1993年   5804篇
  1992年   4777篇
  1991年   4345篇
  1990年   4247篇
  1989年   3965篇
  1988年   3767篇
  1987年   3310篇
  1986年   3190篇
  1985年   3765篇
  1984年   3559篇
  1983年   3172篇
  1982年   3000篇
  1981年   3096篇
  1980年   2875篇
  1979年   2794篇
  1978年   2609篇
  1977年   3049篇
  1976年   3702篇
  1975年   2430篇
  1974年   2406篇
  1973年   2410篇
  1972年   1915篇
  1971年   1793篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
The viability and β‐galactosidase activity of four Lactobacillus strains in milk drink containing gums during 28 days of refrigerated storage at 4 °C were assessed. The population of Lactobacillus rhamnosus GGB101 and Lactobacillus rhamnosus GGB103 were maintained, whereas the population of Lactobacillus reuteri DSM20016 and Lactobacillus reuteri SD2112 significantly decreased. The recommended level of 6 log CFU g?1 was exceeded for all tested trains throughout storage. The highest viable number of Lactobacillus rhamnosus GGB103 (8.76 ± 0.03 log CFU mL?1) was obtained in the product containing carrageenan–maltodextrin. The addition of guar–locust bean–carrageenan led to 20‐fold increase in the level of β‐galactosidase activity for L. rhamnosus GGB101 (1208 ± 2.12 Miller units mL?1) compared to the control (61 ± 2.83 Miller units mL?1). Our results suggested that gums could be added to milk to improve viability and enhance β‐galactosidase activity of Lactobacillus.  相似文献   
42.
43.
44.
45.
46.
47.
In this paper, we report on the indoor concentrations from a suite of full-scale outdoor tracer-gas point releases conducted in the downtown area of Oklahoma City in 2003. A point release experiment consisted of releases of sulfur hexafluoride (SF6) in multiple buildings and from different outdoor locations. From the measurements, we are able to estimate the concentration variations indoors for a building operating under “typical” operating conditions. The mean indoor spatial coefficients of variation are 30% to 45% from a daytime outdoor release are around 80% during an outdoor evening release. Having estimates of the spatial coefficient of variation provides stakeholders, including first responders, with the likely range of concentrations in the building when little is known about the building characteristics and operating behavior, such as developing urban-scale hazard and consequence analyses. We show differences in indoor measurements at different distances to the release points, floors of the building, and heating, ventilation, and air conditioning system (HVAC) operation. We also show estimates at different time resolutions. The statistics show that in the studied medium to large commercial buildings, spatial differences would result in peak indoor concentrations in certain parts of the buildings that may be substantially higher than the building average. To our knowledge, very few tracer gas measurements have been conducted in buildings of this scope, particularly with measurements on multiple floors and within a floor. The resulting estimates of spatial variability provide a unique opportunity for hazard assessment, and comparison to multi-zone models.  相似文献   
48.
The diagnosis and treatment of prostate cancer (PCa) is a major health-care concern worldwide. This cancer can manifest itself in many distinct forms and the transition from clinically indolent PCa to the more invasive aggressive form remains poorly understood. It is now universally accepted that glycan expression patterns change with the cellular modifications that accompany the onset of tumorigenesis. The aim of this study was to investigate if differential glycosylation patterns could distinguish between indolent, significant, and aggressive PCa. Whole serum N-glycan profiling was carried out on 117 prostate cancer patients’ serum using our automated, high-throughput analysis platform for glycan-profiling which utilizes ultra-performance liquid chromatography (UPLC) to obtain high resolution separation of N-linked glycans released from the serum glycoproteins. We observed increases in hybrid, oligomannose, and biantennary digalactosylated monosialylated glycans (M5A1G1S1, M8, and A2G2S1), bisecting glycans (A2B, A2(6)BG1) and monoantennary glycans (A1), and decreases in triantennary trigalactosylated trisialylated glycans with and without core fucose (A3G3S3 and FA3G3S3) with PCa progression from indolent through significant and aggressive disease. These changes give us an insight into the disease pathogenesis and identify potential biomarkers for monitoring the PCa progression, however these need further confirmation studies.  相似文献   
49.
50.
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