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   1317篇
  免费   6篇
电工技术   9篇
化学工业   65篇
金属工艺   31篇
机械仪表   22篇
建筑科学   30篇
矿业工程   2篇
能源动力   11篇
轻工业   22篇
水利工程   4篇
石油天然气   1篇
无线电   39篇
一般工业技术   60篇
冶金工业   972篇
原子能技术   4篇
自动化技术   51篇
  2022年   5篇
  2018年   4篇
  2017年   4篇
  2016年   5篇
  2015年   3篇
  2013年   16篇
  2012年   9篇
  2011年   11篇
  2010年   5篇
  2009年   7篇
  2008年   18篇
  2007年   23篇
  2006年   15篇
  2005年   17篇
  2004年   23篇
  2003年   15篇
  2002年   16篇
  2001年   10篇
  2000年   9篇
  1999年   48篇
  1998年   302篇
  1997年   177篇
  1996年   117篇
  1995年   62篇
  1994年   56篇
  1993年   61篇
  1992年   8篇
  1991年   11篇
  1990年   14篇
  1989年   16篇
  1988年   14篇
  1987年   17篇
  1986年   10篇
  1985年   15篇
  1984年   4篇
  1983年   10篇
  1982年   12篇
  1981年   7篇
  1980年   22篇
  1979年   7篇
  1978年   4篇
  1977年   23篇
  1976年   51篇
  1975年   3篇
  1974年   4篇
  1971年   3篇
  1970年   6篇
  1966年   2篇
  1962年   3篇
  1961年   3篇
排序方式: 共有1323条查询结果,搜索用时 15 毫秒
991.
Gestational diabetes mellitus (GDM) is associated with defects in insulin secretion and insulin action, and women with a history of GDM carry a high risk for the development of non-insulin-dependent diabetes mellitus (NIDDM). Assessment of subjects with a history of GDM who are currently normoglycemic should help elucidate some of the underlying defects in insulin secretion or action in the evolution of NIDDM. We have studied 14 women with normal oral glucose tolerance who had a history of GDM. They were compared with a group of control subjects who were matched for both body mass index (BMI) and waist-to-hip ratio (WHR). All subjects underwent tests for the determination of oral glucose tolerance, ultradian oscillations in insulin secretion during a 28-h glucose infusion, insulin secretion in response to intravenous glucose, glucose disappearance after intravenous glucose (Kg), and insulin sensitivity (SI) as measured by the Bergman minimal model method. The BMI in the post-GDM women was similar to that in the control subjects (24.9 +/- 1.2 vs. 25.4 +/- 1.4 kg/m2, respectively), as was the WHR ratio (0.80 +/- 0.01 vs. 0.76 +/- 0.01, respectively). The post-GDM women were slightly older (35.2 +/- 0.9 vs. 32.1 +/- 1.4 years, P = 0.04). The fasting plasma glucose levels were significantly higher in the post-GDM group than in the control group (4.9 +/- 0.1 vs. 4.4 +/- 0.1 mmol/l, respectively, P < 0.001) and remained higher at each of the subsequent determinations during the oral glucose tolerance test, although none had a result indicative of either diabetes or impaired glucose tolerance.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
992.
993.
994.
G.P. Saha  J. Stephenson 《Energy》1980,5(2):167-175
This paper describes an engineering-economic model which was developed to simulate residential energy use in New Zealand from 1976 to 2000. The model is sensitive to major technological, economic and demographic determinants. It deals with energy use at the national level for four types of fuels (electricity, oil, gas, and “other”) and four types of end uses (space heating, water heating, cooking, and “other”). Simulations from 1961 to 1978 show that the model accurately predicts data on energy use, appliance stock, intensity of use of the appliances, and the construction of new housing units for the historical simulation and ex-post forecast periods. The model demonstrates that the potential of conservation programmes employing proven technology to reduce energy use can be substantial; in fact, it is possible to achieve a nearly zero energy growth with little effect on life style.  相似文献   
995.
Hybridization of tRNAs of Drosophila melanogaster to polytene chromosomes   总被引:1,自引:0,他引:1  
Highly purified tRNAs from Drosophila melanogaster were iodinated with 125I and hybridized to squashes of polytene chromosomes of Drosophila silivary glands followed by autoradiography to localize binding sites. Most tRNAs hybridize strongly to more than one site and weakly to one or more additional sites. The major sites for various tRNAs are the following: tRNA2Arg, 42A, 84F1,2; tRNA2Asp, 29DE; tRNA3Gly, 22BC, 35BC, 57BC, tRNA2Lys, 42A, 42E; tRNA5Lys, 84AB, 87B; tRNA2Met, 48B5-7, 72F1-2, 83F-84A; tRNA3Met, 46A1-2, 61D1-2, 70F1-2; tRNA4Ser, 12DE, 23E; tRNA7Ser, 12DE, 23E; tRNA3aVal, 64D; tRNA3bVal, 84d3-4, 92b1-9; tRNA4Val, 56D3-7, 70BC.  相似文献   
996.
997.
Captopril, an angiotensin-converting enzyme inhibitor, is being evaluated as an antihypertensive agent. We report on a patient who developed the nephrotic syndrome while on captopril 450 mg/d. Her urinary protein excretion was 5-7 g/24 h, plasma albumin concentration was 25 g/l, plasma cholesterol was 16,2 mmol/l, and she had oedema. Renal biopsy showed subepithelial deposits on the basement membrane.  相似文献   
998.
A study was conducted to provide a means for reconciliation of the conflicting data on the relationship of negative mood state to altruism. Whereas some studies have shown that negative mood leads to increases in altruistic action, others have shown the reverse. It was hypothesized that the inconsistency of these results was due to differences in the ages and consequent levels of socialization of the subjects employed in the earlier studies. In order to test the hypothesis, subjects from three age groups (6-8, 10-12, and 15-18 years old) were asked to think of either depressing or neutral events and were subsequently given the opportunity to be privately generous. Consistent with predictions from the negative state relief model of altruism, the youngest, least socialized subjects were somewhat less generous in the negative mood condition, but this relationship progressively reversed itself until in the oldest, most socialized group, the negative mood subjects were significantly more generous than neutral mood controls. The data were taken as support for a hedonistic conception of altruism that views adult benevolence as self-gratification. It is suggested that the reward character of benevolence derives from the socialization experience.  相似文献   
999.
1000.
An array of microstrip antenna panels was designed for use on a small instrumented satellite as part of a 400-MHz telemetry link between that satellite and NASA's shuttle spacecraft. A roughly omnidirectionalphi-plane pattern was desired. The 1.4-wavelength diameter of the satellite and the various ports and structures on its surface presented strong constraints on the antenna array design. Eight antennas, each one a quarter-wavelength panel with one radiating and one shorted edge, were chosen. Aphi-plane pattern ripple of 4.4 dB and a gain of at least 0.1 dB relative to a half-wavelength dipole were realized. The design technique used for the individual antenna panels included the study of feed-point location for impedance matching and the effect of losses in the dielectric. A superposition method was used to synthesize the radiation patterns for different numbers and different excitations of antennas on the satellite.  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