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   1435篇
  免费   2篇
综合类   1篇
化学工业   32篇
金属工艺   12篇
机械仪表   29篇
建筑科学   12篇
能源动力   5篇
轻工业   18篇
水利工程   4篇
石油天然气   9篇
无线电   14篇
一般工业技术   36篇
冶金工业   1244篇
自动化技术   21篇
  2020年   1篇
  2017年   1篇
  2016年   5篇
  2015年   4篇
  2014年   6篇
  2013年   21篇
  2012年   9篇
  2011年   9篇
  2010年   7篇
  2009年   13篇
  2008年   7篇
  2007年   7篇
  2006年   4篇
  2005年   8篇
  2004年   5篇
  2003年   7篇
  2002年   2篇
  2001年   5篇
  2000年   3篇
  1999年   51篇
  1998年   399篇
  1997年   207篇
  1996年   153篇
  1995年   69篇
  1994年   51篇
  1993年   61篇
  1992年   12篇
  1991年   16篇
  1990年   11篇
  1989年   20篇
  1988年   16篇
  1987年   12篇
  1986年   11篇
  1985年   8篇
  1984年   8篇
  1983年   5篇
  1982年   8篇
  1981年   12篇
  1980年   13篇
  1979年   1篇
  1978年   5篇
  1977年   36篇
  1976年   112篇
  1975年   6篇
  1974年   3篇
  1972年   1篇
  1970年   1篇
  1968年   1篇
  1959年   1篇
  1955年   2篇
排序方式: 共有1437条查询结果,搜索用时 19 毫秒
101.
We report a case of gastric outlet obstruction simulating gastric antral neoplasm resulting from a perforated Meckel's diverticulum. Presentation of this nature has not been previously reported.  相似文献   
102.
Flash photolysis experiments have been carried out for the first time on a hemoglobin ferrous cyanide adduct with an 8 ns laser pulse. A 95% nonexponential rebinding process occurs within 2 micros after full photolysis in ferrous cyanide dimeric Scapharca inaequivalvis hemoglobin (HbI), indicating that once photolyzed the cyanide anion is not able to escape from the protein matrix and rebinds to the heme iron. The resonance Raman spectrum of the 10 ns photoproduct is identical to that of the fully relaxed deoxy derivative, indicating that in the ferrous cyanide HbI adduct protein relaxation occurs within 10 ns after photolysis. This behavior is at variance with that of the carbonmonoxy HbI derivative in which very little geminate rebinding is observed and the photoproduct relaxes with a lifetime of 1 micros. The fast relaxation of the cyanide HbI photoproduct can be accounted for by the small perturbation of the heme structure induced by cyanide binding to ferrous HbI. This is consistent with a deoxy-like conformation of the HbI ferrous cyanide adduct and implies that the pathway for relaxation involves only minor local rearrangements of the heme moiety. Photolysis experiments carried out on ferrous cyanide horse myoglobin, which can be saturated only partially, show a qualitatively similar behavior in ligand rebinding, indicating that the geminate process of the cyanide anion is a general phenomenon in hemoproteins.  相似文献   
103.
104.
105.
106.
This study determined the rate and associated factors of red light infringement among urban commuter cyclists. A cross-sectional observational study was conducted using a covert video camera to record cyclists at 10 sites across metropolitan Melbourne, Australia from October 2008 to April 2009. In total, 4225 cyclists faced a red light and 6.9% were non-compliant. The main predictive factor for infringement was direction of travel, cyclists turning left (traffic travels on the left-side in Australia) had 28.3 times the relative odds of infringement compared to cyclists who continued straight through the intersection. Presence of other road users had a deterrent effect with the odds of infringement lower when a vehicle travelling in the same direction was present (OR = 0.39, 95% CI 0.28–0.53) or when other cyclists were present (OR = 0.26, 95% CI 0.19–0.36). Findings suggest that some cyclists do not perceive turning left against a red signal to be unsafe and the opportunity to ride through the red light during low cross traffic times influences the likelihood of infringement.  相似文献   
107.
108.
We have measured the Fourier transform spectrum of natural OCS from 3700 to 4800 cm-1 with a near Doppler resolution and a line-position accuracy between 4 and 8 x 10(-5) cm-1. For the normal isotopic species, 37 vibrational transitions have been analyzed for both frequencies and intensities. We also report 15 bands of OC34S, eight bands of O13CS, nine bands of OC33S, and two bands of 18OCS. Important effective Herman-Wallis terms are explained on the basis of eigenvectors. A comparison of different line-pointing programs is also presented. Copyright 1998 Academic Press.  相似文献   
109.
110.
Diurnal platyrrhines, both di- and trichromats, have magnocellular (M-) and parvocellular (P-) retinal ganglion cells which are morphologically very similar to those found in catarrhines. Catarrhine central P ganglion cells contact single midget bipolar cells, which contact single cones. Physiological recordings of retinal ganglion cells of dichromatic Cebus monkeys showed very similar cell properties to the catarrhine macaque, except that P ganglion cells lacked colour-opponency. We describe the presence of single-headed midget bipolar cells in the Cebus retina. These midget bipolar cells have axon terminal sizes in the same range as the dendritic tree sizes of P ganglion cells as far as 2 mm of retinal eccentricity. This result supports the view that, as in catarrhines, central P ganglion cells of platyrrhines receive input from single midget bipolar cells which in turn, receive input from single cones. This finding is consistent with the idea that a P pathway with one-to-one connectivity was present in the anthropoid ancestor before the divergence between catarrhines and platyrrhines.  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