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   850篇
  免费   23篇
  国内免费   2篇
电工技术   43篇
综合类   3篇
化学工业   131篇
金属工艺   27篇
机械仪表   16篇
建筑科学   14篇
能源动力   29篇
轻工业   52篇
水利工程   2篇
无线电   109篇
一般工业技术   144篇
冶金工业   176篇
原子能技术   42篇
自动化技术   87篇
  2023年   6篇
  2022年   11篇
  2021年   17篇
  2020年   12篇
  2019年   9篇
  2018年   17篇
  2017年   9篇
  2016年   11篇
  2015年   15篇
  2014年   15篇
  2013年   37篇
  2012年   36篇
  2011年   38篇
  2010年   39篇
  2009年   58篇
  2008年   43篇
  2007年   20篇
  2006年   26篇
  2005年   24篇
  2004年   17篇
  2003年   13篇
  2002年   10篇
  2001年   16篇
  2000年   10篇
  1999年   18篇
  1998年   76篇
  1997年   52篇
  1996年   25篇
  1995年   30篇
  1994年   27篇
  1993年   26篇
  1992年   6篇
  1991年   9篇
  1990年   8篇
  1989年   10篇
  1988年   8篇
  1987年   8篇
  1986年   6篇
  1985年   2篇
  1984年   8篇
  1983年   11篇
  1982年   5篇
  1981年   6篇
  1980年   2篇
  1979年   4篇
  1978年   2篇
  1977年   6篇
  1976年   7篇
  1972年   1篇
  1970年   1篇
排序方式: 共有875条查询结果,搜索用时 15 毫秒
121.
This paper presents a method for describing and reasoning about the behavior of VLSI circuits within the framework of Extended Temporal Logic. For a reasoning method, an “ω-graph approach” is proposed which is useful in verifying the validity of a design. Not only verification but also other reasoning about circuit properties, such as unknown signal identification, can be treated in a unified way by this ω-graph approach. This approach has been studied as a basis of an expert system for the authors’ VLSI CAD system.  相似文献   
122.
The electroencephalograms of 82 infants (between 27 and 37 weeks of conceptional age) recorded during the neonatal period were analyzed and compared with the ultimate clinical evolution. Three groups of infants were identified according to their neurological state at 3 years of age or older: group A: normal (34 infants), group B: minor neurological sequellae (13 infants) and group C: major neurological sequellae (17 infants). A fourth group (group D: 18 infants) died during the neonatal period. The E.E.Gs were classified as: normal, questionably abnormal, moderately abnormal or grossly abnormal. The analysis revealed that E.E.Gs classified as grossly abnormal, were found only in groups B, C and D. Serial E.E.Gs were of more value in distinguishing these groups. Only infants in groups C and D (with I exceptional case in group B) had E.E.Gs which remained abnormal for several weeks or which deteriorated during the neonatal period. This study shows the prognostic value of the E.E.G. recorded during the neonatal period, particularly serial recordings obtained during and after a period of clinical deterioration. A detailed statistical analysis of the E.E.Gs is in progress.  相似文献   
123.
Multi-elemental traces comprising particulate matter in natural water collected during summer in 1978 and 1979 from British Columbia, Canada, were analyzed by α-particle excited X-ray fluorometry. Common elements from all waters examined were Si, Cl, Ca and Fe. The similarity of their distribution in different aquatic environments was statistically analyzed. They were distributed homogeneously in the marine environment but heterogeneously in the freshwater environments. No heavy metals concerned with the environmental standards were detected for all waters examined.  相似文献   
124.
125.
An experimental guided millimeter-wave transmission system is constructed employing two 806-Mbit/s digital repeaters, an 8.4-km waveguide line loop, and channel coupling networks. This paper presents its characteristics, such as waveforms, amplitude and delay, error rate, and timing jitter in some detail.  相似文献   
126.
The letter reports results obtained with laboratory transmission experiments on high-speed digital signals by optical wavelength-division multiplexing, using a newly developed optical multiplexer and demultiplexer, as well as other high-performance optical devices and fibres.  相似文献   
127.
From January 1987 through June 1992, 18 patients with poor left ventricular function (left ventricular ejection fraction [LVEF] less than 0.3) underwent elective isolated primary coronary artery bypass surgery. The mean age was 56.4 years (range, 46 to 72 years), and 15 were males and 3 were females. Mean pre-operative LVEF measured by ventriculography was 0.26 +/- 0.03 (range, 0.19 to 0.30). Sixteen patients (88.9%) had a prior myocardial infarction and 9 (50%) had a history of congestive heart failure. Complete revascularization was the goal for all patients, and the mean number of bypass grafts was 3.0 +/- 0.8 per patient. The left anterior descending coronary artery (LAD) was revascularized in all patients. There were no operative deaths. Post-operative LVEF improved significantly from 0.26 +/- 0.03 to 0.42 +/- 0.11 (p = 0.0002), and the regional left ventricular wall motion improved in the diaphragmatic and posterobasal regions (p < 0.01). The patency of the grafts was 93.9% in all, and 100% for LAD. The mean follow-up period was 77 months, and the overall actuarial survival rate was 88.9% at 10 years. During follow-up periods, two patients died of congestive heart failure (CHF), and two required three rehospitalizations because of CHF. The overall cardiac event free rate was 75.8% at 10 years. In patients with poor left ventricular function, surgical revascularization can be performed safely, but congestive heart failure sometimes occurs during follow-up periods and may be the cause of death. Therefore alternate forms of therapy such as cardiac transplantation and/or TMLR should be considered in selected patients.  相似文献   
128.
If a loss of vacuum event (LOVE) occurs due to damage of the vacuum vessel of a nuclear fusion experimental reactor, some chemical reactions such as a graphic oxidation and a buoyancy-driven exchange flow take place after equalization of the gas pressure between the inside and outside of the vacuum vessel. The graphite oxidation would generate inflammable carbon monoxide and release tritium retained in the graphite. The exchange flow through the breaches may transport the carbon monoxide and tritium out of the vacuum vessel. To add confidence to the safety evaluations and analyses, it is important to grasp the basic phenomena such as the exchange flow and the graphite oxidation. Experiments of the exchange flow and the graphite oxidation were carried out to obtain the exchange flow rate and the rate constant for the carbon monoxide combustion, respectively. These experimental results were compared with existing correlations. We plan a scaled-model test and a full-scale model test for the LOVE.  相似文献   
129.
A simple method using ion-pair high-performance liquid chromatography was established for the rapid and precise determination of synephrine in thirty three species of oriental pharmaceutical decoctions containing Aurantii Nobilis Pericarpium. An ODS column and a mixed solvent system of water, acetonitrile, sodium dodecyl sulfate and phosphoric acid as a mobile phase were used for the separation. Synephrine was eluted without interference of other coexisting components within 15 min.  相似文献   
130.
A 44-year-old woman with stage IV non-Hodgkin's lymphoma (NHL) of the left ovary is described. She had an extended hysterectomy and bilateral salpingo-ophorectomy and thereafter received six courses of combination chemotherapy (cyclophosphamide, adriamycin, vincristine and predonisolone; CHOP). The patient is well with no evidence of recurrence at 12 months after surgery. The literature on primary ovarian lymphoma is reviewed.  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