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   4276篇
  免费   101篇
  国内免费   7篇
电工技术   45篇
综合类   7篇
化学工业   544篇
金属工艺   47篇
机械仪表   81篇
建筑科学   56篇
矿业工程   1篇
能源动力   88篇
轻工业   127篇
水利工程   8篇
石油天然气   5篇
无线电   467篇
一般工业技术   450篇
冶金工业   2066篇
原子能技术   8篇
自动化技术   384篇
  2023年   10篇
  2022年   35篇
  2021年   52篇
  2020年   30篇
  2019年   36篇
  2018年   55篇
  2017年   44篇
  2016年   54篇
  2015年   43篇
  2014年   90篇
  2013年   191篇
  2012年   142篇
  2011年   156篇
  2010年   118篇
  2009年   153篇
  2008年   153篇
  2007年   137篇
  2006年   100篇
  2005年   84篇
  2004年   77篇
  2003年   71篇
  2002年   66篇
  2001年   49篇
  2000年   43篇
  1999年   95篇
  1998年   718篇
  1997年   421篇
  1996年   228篇
  1995年   164篇
  1994年   130篇
  1993年   133篇
  1992年   45篇
  1991年   60篇
  1990年   38篇
  1989年   33篇
  1988年   36篇
  1987年   33篇
  1986年   26篇
  1985年   27篇
  1984年   14篇
  1983年   8篇
  1982年   14篇
  1981年   13篇
  1980年   19篇
  1979年   4篇
  1978年   5篇
  1977年   28篇
  1976年   80篇
  1975年   5篇
  1973年   7篇
排序方式: 共有4384条查询结果,搜索用时 15 毫秒
1.
Journal of Signal Processing Systems - With the latest development of automation technology, object detection technology has received more and more research attention. Automated object detection...  相似文献   
2.
3.
4.
Ho  Y. S.  Chiu  C. H.  Tseng  T. M.  Chiu  W. T. 《Scientometrics》2003,57(3):369-376
Honour Index (HoI), a method to evaluate research performance within different research fields, was derived from the impact factor (IF). It can be used to rate and compare different categories of journals. HoI was used in this study to determine the scientific productivity of stem cell research in the Asian Four Dragons (Hong Kong, Singapore, South Korea and Taiwan) from 1981 to 2001. The methodology applied in this study represents a synthesis of universal indicator studies and bibliometric analyses of subfields at the micro-level. We discuss several comparisons, and conclude the developmental trend in stem cell research for two decades. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   
5.
Polyaryloxydiphenylsilanes were prepared from phosphorus‐containing diols and diphenydichlorolsilane through solution polymerization. With a stoichiometric imbalance in feed monomers, the resulting polymers exhibited moderate melting points and good processing properties. The polymers prepared showed initial decomposition temperatures above 340 °C, excellent thermal stability, high char yields at 850 °C and very high limited oxygen index values of 56–59. The polymers' char yields and their (P + Si) contents showed linear relationships. © 2003 Society of Chemical Industry  相似文献   
6.
Lead content of rice collected from various areas in the world   总被引:1,自引:0,他引:1  
Rice samples consumed by local populations were collected between 1990 and 1995 in 17 areas in the world, mostly from Asia (10 areas), but also from 7 areas outside of Asia. In total, 1528 samples were obtained (about one half from Japan) and were analyzed for lead (Pb) by electrothermal atomic absorption spectrometry. When the Pb contents in rice samples were classified into 10 areas in Asia, the highest and the lowest geometric means (GMs) were for Indonesia (38 ng/g) and Australia (2 ng/g), respectively. Among 7 regions outside Asia, the GM was highest for Spain (58 ng/g) and the lowest for the USA. (3 ng/g). Moreover, inter-regional differences were significant, when more than 100 samples from one area were divided into 3-9 regions and GMs for regions were compared. There was a marked difference in Pb contents in rice by areas and regions in the world. Nevertheless, comparison by area of the present results with those reported in literature show that there has been no substantial reduction in Pb in rice in the past decade either in Japan or elsewhere in the world.  相似文献   
7.
8.
Dynamic cardiomyoplasty (DCM) involves the electrical stimulation of a pedicled latissimus dorsi muscle flap wrapped around the falling ventricle as a means of cardiac assist. To further elucidate a potential neurohumoral mechanism for improvement of cardiac output after myoplasty, we evaluated the hemodynamic effects of in situ stimulation of the latissimus dorsi muscle (in the absence of cardiomyoplasty). In seven mongrel dogs, a nerve cuff electrode (Medtronic 6901) was placed around the left thoracodorsal nerve (TDN). This was attached to a pulse generator (Medtronic, Itrel 7420), delivering a 4.0 volt, 0.19 second on, 0.81 second off, 33 Hz, 210 microsecond pulse width, cyclic bursts similar to that used in DCM. Stroke volume index (SVI) and other hemodynamic parameters as well as plasma norepinephrine (NE) levels were measured at five stages: baseline, stimulator on at 0, 2, and 5 minutes, and stimulator off at 30 minutes after. The animals were then subjected to 4 weeks of rapid pacing at 240 beats/min (Medtronic 8329) to induce heart failure, and as the rapid pacing was discontinued, measurements were repeated as above. After rapid pacing, cardiac function was significantly depressed, and NE was elevated (133 +/- 69 versus 500 +/- 353 pg/mL, p < 0.05). In the normal hearts, TDN stimulation increased SVI, heart rate, systemic pressure, and NE levels. In heart failure, however, no significant changes in cardiac function and NE levels were noted. In conclusion, our data indicate that in the normal hearts, afferent impulses from TDN stimulation alone may augment cardiac function by means of a neurohumoral effect that is not seen in severe heart failure. The implications of these findings in DCM are discussed.  相似文献   
9.
Pre-transplant nephrectomy was done in a 25-year-old man for calculous pyelonephritis using a retroperitoneal laparoscopic approach with a newly devised ligature applicator-dissector- kidney retractor.  相似文献   
10.
PURPOSE: To select ideal radiologic projections for mapping and ablation of tachycardias of right ventricular outflow tract (RVOT). METHODS: Ten hearts from human corpses were studied utilizing radiopaque material to identify the pulmonary valve and three distinct sites on this valve: septal anterior (A), septal posterior (P) and free-wall (L). Next, the hearts were filmed in the frontal plane and in oblique projections with 15 degrees increments to the right and to the left. The projections in which the sites were lateralized on the valve, eased radiologic interpretation and were considered ideal for mapping and ablation. Depending on the proximity of the sites to the lateral extremes of the pulmonary valve, the projections were considered ideal ( ), intermediary (++) and inadequate (+). RESULTS: Projections [table: see text] CONCLUSION: The A site of RVOT was best indicated in the 60 and 45 degrees left anterior oblique projections; the 0 degree postero anterior projection was best for mapping the P site; the L region was best explored in the 60 degrees right anterior oblique projection.  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