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   1538篇
  免费   118篇
电工技术   5篇
综合类   6篇
化学工业   460篇
金属工艺   16篇
机械仪表   15篇
建筑科学   122篇
矿业工程   1篇
能源动力   27篇
轻工业   299篇
水利工程   25篇
石油天然气   6篇
无线电   66篇
一般工业技术   255篇
冶金工业   193篇
原子能技术   3篇
自动化技术   157篇
  2024年   4篇
  2023年   23篇
  2022年   20篇
  2021年   84篇
  2020年   43篇
  2019年   57篇
  2018年   57篇
  2017年   49篇
  2016年   55篇
  2015年   52篇
  2014年   79篇
  2013年   119篇
  2012年   102篇
  2011年   138篇
  2010年   109篇
  2009年   80篇
  2008年   78篇
  2007年   77篇
  2006年   56篇
  2005年   53篇
  2004年   49篇
  2003年   44篇
  2002年   32篇
  2001年   17篇
  2000年   20篇
  1999年   12篇
  1998年   12篇
  1997年   14篇
  1996年   9篇
  1995年   12篇
  1994年   3篇
  1993年   11篇
  1992年   6篇
  1990年   4篇
  1989年   6篇
  1988年   5篇
  1987年   6篇
  1986年   3篇
  1985年   3篇
  1984年   9篇
  1982年   4篇
  1981年   4篇
  1980年   2篇
  1979年   2篇
  1977年   2篇
  1976年   7篇
  1975年   4篇
  1974年   3篇
  1972年   4篇
  1964年   2篇
排序方式: 共有1656条查询结果,搜索用时 437 毫秒
1.
2.
PURPOSE: Iron deficiency anemia (IDA) during pregnancy and infancy is still common in developed countries, especially in low-income groups. We examined the prevalence of anemia and IDA in healthy low-income pregnant women participating in the Early Childhood Initiatives (ECI) program, and in their infants when they reached six months of age. METHODS: Pregnant women were recruited by nutritionists. In mothers, hemoglobin (Hb), mean corpuscular volume, and serum ferritin (SF) were measured at 36 +/- 2 weeks of gestation. In infants, Hb, mean corpuscular volume, SF, serum iron, total iron binding capacity (TIBC), and transferrin saturation (TS) were measured at six months of age. Thirty-one mother-infant pairs participated. RESULTS: Among the 31 pregnant women participating in the ECI program, six (19.4%) were anemic (Hb <110 g/L) and five (16.1%) suffered from IDA (Hb <110 g/L and SF <10 microg/L). Among infants, seven of 23 (30.4%) were anemic (Hb <110 g/L) and five of 23 (21.7%) suffered from IDA (Hb <110 g/L plus two of the following: TIBC >60 micromol/L, SF <10 microg/L, serum iron <5.3 micromol/L, TS < or = 15%). CONCLUSIONS: The prevalence of anemia in this group of low-income pregnant women is comparable to that in privileged women. The prevalence of IDA in infants is comparable to that observed in other high-risk groups. Effective strategies are needed to prevent IDA in vulnerable groups.  相似文献   
3.
Glyconanoparticles which present carbohydrate and amino groups motifs at their surface were produced. These particles were highly stable and soluble in aqueous solutions. The presence of the carbohydrate groups also allowed the inclusion of more strongly binding groups, without affecting solubility. The binding of a model DNA, plasmid by these nanoparticles was studied by atomic force microscopy, transmission electron microscopy, and gel electrophoresis. Significant differences between the nanoparticles based on their affinities for the DNA were found, with implications for their potential use as nonviral gene delivery agents.  相似文献   
4.
The fluctuations observed by recording the picosecond pulses of a mode-locked laser with a synchroscan streak camera are due to the laser jitter and to the variations of the zero crossing of the synchronization. By means of a simple model, it is shown that the dispersions measured when the synchronization is generated from the mode-locker oscillator reflect the instantaneous time phase fluctuations of this oscillator. From the study of the experimental recordings with methods of time series analysis it results that the phase noise of the electronic oscillator is consistent with an underlying low-dimensional strange attractor.  相似文献   
5.
6.
7.
The processing costs involved in regional accent normalization were evaluated by measuring differences in lexical decision latencies for targets placed at the end of sentences with different French regional accents. Over a series of 6 experiments, the authors examined the time course of comprehension disruption by manipulating the duration and presentation conditions of accented speech. Taken together, the findings of these experiments indicate that regional accent normalization involves a short-term adjustment mechanism that develops as a certain amount of accented signal is available, resulting in a temporary perturbation in speech processing. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
8.
Machine Translation - Existing work on the animation of signing avatars often relies on pure procedural techniques or on the playback of Motion Capture (MoCap) data. While the first solution...  相似文献   
9.
Experimental investigations have been made in which single crystals of solid explosives such as cyclotrimethylene trinitramine, RDX, pentaerythritol tetranitrate, PETN, AgN3 and Pb(N3)2, were irradiated with a focused laser beam of wavelength 266 nm and duration 5 nsec in an ultra high vacuum system housing a fast and sensitive time-of-flight mass spectrometer. From the mass spectra (both +ve and -ve ions) of the chemical species obtained, possible decomposition schemes of RDX and PETN have been proposed. For silver and lead azides, the laser irradiation did not cause explosions if the power density was sufficiently low, but micrometre size craters were formed. In the mass spectra of AgN3 products N3 and silver cluster ions, Ag n +, have been found for the first time. It has been suggested that such investigations may possibly throw some light on our understanding of the reactions taking place in a deflagration/detonation wave.  相似文献   
10.
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