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   2171篇
  免费   46篇
  国内免费   4篇
电工技术   85篇
综合类   1篇
化学工业   397篇
金属工艺   75篇
机械仪表   34篇
建筑科学   31篇
能源动力   55篇
轻工业   204篇
无线电   290篇
一般工业技术   323篇
冶金工业   554篇
原子能技术   68篇
自动化技术   104篇
  2023年   8篇
  2022年   21篇
  2021年   40篇
  2020年   22篇
  2019年   28篇
  2018年   33篇
  2017年   34篇
  2016年   28篇
  2015年   30篇
  2014年   42篇
  2013年   110篇
  2012年   60篇
  2011年   72篇
  2010年   68篇
  2009年   68篇
  2008年   81篇
  2007年   80篇
  2006年   53篇
  2005年   50篇
  2004年   47篇
  2003年   54篇
  2002年   47篇
  2001年   37篇
  2000年   41篇
  1999年   69篇
  1998年   218篇
  1997年   133篇
  1996年   111篇
  1995年   62篇
  1994年   53篇
  1993年   52篇
  1992年   37篇
  1991年   19篇
  1990年   26篇
  1989年   26篇
  1988年   22篇
  1987年   11篇
  1986年   28篇
  1985年   18篇
  1984年   18篇
  1983年   15篇
  1982年   14篇
  1981年   16篇
  1980年   19篇
  1979年   21篇
  1978年   10篇
  1977年   17篇
  1976年   29篇
  1973年   5篇
  1967年   3篇
排序方式: 共有2221条查询结果,搜索用时 15 毫秒
51.
Understanding the genetic factors of diabetes is essential for addressing the global increase in type 2 diabetes. HNF1A mutations cause a monogenic form of diabetes called maturity-onset diabetes of the young (MODY), and HNF1A single-nucleotide polymorphisms are associated with the development of type 2 diabetes. Numerous studies have been conducted, mainly using genetically modified mice, to explore the molecular basis for the development of diabetes caused by HNF1A mutations, and to reveal the roles of HNF1A in multiple organs, including insulin secretion from pancreatic beta cells, lipid metabolism and protein synthesis in the liver, and urinary glucose reabsorption in the kidneys. Recent studies using human stem cells that mimic MODY have provided new insights into beta cell dysfunction. In this article, we discuss the involvement of HNF1A in beta cell dysfunction by reviewing previous studies using genetically modified mice and recent findings in human stem cell-derived beta cells.  相似文献   
52.
野外试验场黄土的理化分析   总被引:7,自引:6,他引:7  
本实验为低,中水平放射性废物浅地层处置安全评价提供现场土壤的物理化学参数。采样深度在0.5-9.1m范围内,每个样品进行10项测定;矿物组成,粒度分布、密度、总孔隙度、有效孔隙度、给水度、持水度、渗透系数、阳离子交换容量、含水量。  相似文献   
53.
54.
Residues of 17 pesticides in agricultural products were determined by LC/MS with an atmospheric pressure chemical ionization (APCI) interface in both positive and negative ion modes. Pesticides were extracted with acetonitrile, and the extracts were cleaned-up with a primary and secondary amine (PSA) mini-column eluted with acetone-hexane (1:1). Rice, orange and potato were spiked with the 17 pesticides at 0.1 microgram/g and analyzed by the proposed method. The average recoveries of these pesticides usually ranged from 70 to 98% and the relative standard deviations were usually around 10%. These results suggested that LC/MS with APCI could be used to determine the residue levels of the 17 pesticides in these crops.  相似文献   
55.
56.
For the design of radio local distribution systems in densely built-up areas, estimating how many subscribers are in sight from a nodal station is important. This paper proposes a method for estimating probability of success of line-of-sight paths termed visibility. Method validity is confirmed bypractical field examinations.  相似文献   
57.
Experimental results are shown on the frequency stabilization of a GaAlAs laser using a Doppler-free spectrum in the saturated absorption of the Cs-D2line at 852.1 nm. The frequency stability (Allan variance) between3.0 times 10^{-12}and1.0 times 10^{11}was obtained at the averaging time between 0.1 and 1000 s.  相似文献   
58.
Operation tests of a cavity designed for high purity mode operation of the submillimeter wave gyrotron FU VA has been carried out successfully. The observed emission patterns of several cavity modes appear very pure and are compared with calculated results. High purity mode operation has the advantage of making the conversion to Gaussian-like beams more efficient.  相似文献   
59.
Food poisoning from Staphylococcus aureus is sometimes caused by improper handling of food items in food preparation facilities. Prevention of contamination by employees is particularly important in facilities where a significant amount of food preparation is performed by hand. Some experiments have been performed to describe bacterial cross-contamination in the food preparation process, but there have been few studies of cross-contamination in actual food preparation facilities. Aiming to shed light on the transmission of S. aureus in food preparation facilities, this study collected samples of 66 strains of this bacterium from the fingers of food preparation staff, foodstuffs, prepared foods, cooking utensils, and cooking equipment and typed them with the ribotyping method. S. aureus from the same ribogroup was detected on the hands of a study participant, a faucet, knife, frying pan, and a salad, indicating that bacteria found on the hands of the study participant was transmitted to cooking utensils and prepared foods. Transmission (from a faucet to a frying pan handle) of bacteria by another person, a third party, was also detected.  相似文献   
60.
A simple and rapid multiresidue method was developed for the determination of twelve quinolones (ciprofloxacin, danofloxacin, difloxacin, enrofloxacin, flumequine, marbofloxacin, nalidixic acid, norfloxacin, ofloxacin, orbifloxacin, oxolinic acid and sarafloxacin) in muscle, liver, chicken eggs, milk, prawn and rainbow trout.The quinolones were extracted from a sample with acetonitrile-water (95 : 5). A fifth part of the filtered extract was diluted with water to keep the acetonitrile ratio at ca. 60%, and passed through a C18 mini-column. The eluate was evaporated to dryness, and the residues were dissolved in methanol-water (30 : 70) for HPLC analysis.The quinolones were separated on a Inertsil ODS-3V column (4.6 mm i.d.x250 mm) with a gradient system of 0.1% phosphoric acid-acetonitrile as the mobile phase, with fluorescence detection.No interfering peak was found on the chromatograms of animal and fishery products, except for milk. The recoveries of the quinolones were over 60% from the animal and fishery products fortified at 0.1 microg/g, and the quantification limits of the quinolones were 0.005 microg/g. This proposed method was found to be effective and suitable for the screening of the quinolones in animal and fishery products.  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