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   1190篇
  免费   15篇
  国内免费   1篇
电工技术   5篇
化学工业   90篇
金属工艺   5篇
机械仪表   1篇
建筑科学   30篇
矿业工程   7篇
能源动力   5篇
轻工业   31篇
水利工程   9篇
石油天然气   3篇
无线电   67篇
一般工业技术   53篇
冶金工业   858篇
原子能技术   1篇
自动化技术   41篇
  2022年   3篇
  2021年   4篇
  2019年   5篇
  2018年   5篇
  2017年   6篇
  2016年   8篇
  2015年   3篇
  2014年   6篇
  2013年   17篇
  2012年   9篇
  2011年   23篇
  2010年   13篇
  2009年   18篇
  2008年   19篇
  2007年   18篇
  2006年   16篇
  2005年   14篇
  2004年   6篇
  2003年   14篇
  2002年   5篇
  2000年   7篇
  1999年   34篇
  1998年   278篇
  1997年   156篇
  1996年   93篇
  1995年   55篇
  1994年   43篇
  1993年   63篇
  1992年   14篇
  1991年   13篇
  1990年   12篇
  1989年   17篇
  1988年   13篇
  1987年   9篇
  1986年   10篇
  1985年   13篇
  1984年   4篇
  1983年   6篇
  1982年   8篇
  1981年   11篇
  1980年   8篇
  1979年   8篇
  1978年   9篇
  1977年   22篇
  1976年   62篇
  1974年   2篇
  1973年   3篇
  1972年   4篇
  1971年   3篇
  1970年   3篇
排序方式: 共有1206条查询结果,搜索用时 15 毫秒
1.
This article describes the results of a survey of radiography program directors on positioning competencies for entry-level radiographers. The survey asked program directors to classify projections as essential, important, rarely needed or for reference only. The objective of the study was to rank radiographic projections from most to least important in clinical practice. The data are provided for use by educators and employers in determining which projections are essential entry-level competencies.  相似文献   
2.
OBJECTIVE: The purpose of this study was to evaluate ERCP and CT findings of ectopic drainage of the common bile duct into the duodenal bulb. CONCLUSION: Although rare, the diagnosis of ectopic drainage of the common bile duct into the duodenal bulb is important to prevent inadvertent damage during biliary tract or gastric surgery and to clarify the cause of chronic peptic ulcers.  相似文献   
3.
A case is described in which a pericardial branch of a nongrafted left internal mammary artery communicated directly with the distal left anterior descending artery, following saphenous vein bypass grafting. This type of collateralization following coronary artery bypass surgery seems to be very rare, and perhaps could protect the myocardium from severe ischemia.  相似文献   
4.
5.
The role of a depressor factor, atrial natriuretic peptide, in the development of arterial hypertension in adolescents with pubertal hypothalamic syndrome was studied in 52 patients and 13 healthy males aged 13-24 years. The duration of disease was 2-11 years. Radioimmunological methods were used to measure plasma atrial natriuretic peptide, plasma renin activity, and serum aldosterone. Patients with borderline arterial hypertension were found to have a significant reduction in their atrial natriuretic peptide levels, and this correlated directly with the renin-aldosterone system, demonstrating insufficiency of the depressor system in patients with pubertal hypothalamic syndrome and the involvement of atrial natriuretic peptide in the development of arterial hypertension, along with disturbances in the functional relationship between atrial natriuretic peptide and the renin-aldosterone system.  相似文献   
6.
7.
OBJECTIVE: To evaluate aspects of the natural history of AA amyloidosis complicating juvenile rheumatoid arthritis (JRA), and its response to therapy with chlorambucil. METHODS: Scintigraphy and 7-day turnover studies were performed in JRA patients with histologically proven (n = 35) or clinically suspected (n = 30) AA amyloidosis, following intravenous injection of 123I and 125I-labeled serum amyloid P component (SAP). Prospective monitoring studies were performed over 2-3 years in 20 patients with amyloidosis. All but 2 amyloidosis patients were treated with chlorambucil. RESULTS: Positive scanning results were obtained in all patients in whom imaging was performed within 12 years of positive biopsy findings of amyloid and in 5 patients with clinically suspected amyloidosis. Negative scanning results with normal SAP metabolism, indicating regression of amyloid, were obtained in 4 patients whose amyloidosis had been in full clinical remission for more than 12 years. Prospective monitoring studies in patients whose JRA-associated inflammatory activity was in remission demonstrated regression of amyloid in 8 patients and no substantial changes in 8 others; however, in 4 further patients with active inflammation, there was accumulation of amyloid. There was a very poor correlation between the amount of amyloid present at a particular site and the resultant organ dysfunction. CONCLUSION: Radiolabeled SAP scintigraphy and turnover studies are useful complementary tools in the diagnosis, screening, and quantitative monitoring of type AA amyloidosis in JRA. The amyloid deposits may progress and/or regress at different rates in different anatomic sites over short periods.  相似文献   
8.
Deconvolution of measurement system effects from pulse response measurements is demonstrated to yield reproducible, accurate characterization of the impulse response (and vector frequency response) of a photodetector or photoreceiver, as well as the intensity waveform of an optical pulse. Calibration is based on a <3-ps FWHM (full width at half maximum) optical pulse and a 50-GHz 3-dB bandwidth electrical sampling system. Vector characterization of a photodetector/photoreceiver to >40 GHz and an optical pulse source to >30 GHz are demonstrated. Calibration and effects of noise are discussed  相似文献   
9.
10.
We give a parametrized family of rational interval maps of degree two, each ergodic, exact and preserving a measure equivalent to a Lebesgue measure. The family includes the unique quadratic Chebyshev polynomial as its only polynomial map. We extend the family to other settings on the circle and real line. We also give numerical approximations to the entropy of the equivalent invariant measure and the Hausdorff dimension of the singular measure of maximal entropy.  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