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   654篇
  免费   15篇
  国内免费   1篇
电工技术   11篇
化学工业   129篇
金属工艺   22篇
机械仪表   6篇
建筑科学   9篇
矿业工程   1篇
能源动力   27篇
轻工业   81篇
水利工程   2篇
无线电   66篇
一般工业技术   110篇
冶金工业   138篇
原子能技术   6篇
自动化技术   62篇
  2022年   6篇
  2021年   8篇
  2020年   9篇
  2019年   12篇
  2018年   8篇
  2017年   9篇
  2016年   12篇
  2015年   10篇
  2014年   20篇
  2013年   26篇
  2012年   24篇
  2011年   31篇
  2010年   40篇
  2009年   35篇
  2008年   21篇
  2007年   35篇
  2006年   23篇
  2005年   19篇
  2004年   9篇
  2003年   13篇
  2002年   15篇
  2001年   14篇
  2000年   13篇
  1999年   18篇
  1998年   43篇
  1997年   36篇
  1996年   23篇
  1995年   17篇
  1994年   17篇
  1993年   15篇
  1992年   5篇
  1991年   3篇
  1990年   3篇
  1989年   3篇
  1988年   2篇
  1987年   4篇
  1986年   3篇
  1985年   6篇
  1984年   2篇
  1983年   3篇
  1982年   2篇
  1981年   5篇
  1980年   5篇
  1979年   3篇
  1978年   4篇
  1977年   7篇
  1976年   12篇
  1975年   3篇
  1974年   3篇
  1973年   3篇
排序方式: 共有670条查询结果,搜索用时 15 毫秒
101.
102.
Atheroma lesions are often found in multiple localizations. In addition, operative mortality for aneurysms of the non-ruptured sub-renal aorta is mainly related to coronary risk. In an attempt to reduce coronary risk, coronarography was performed in all patients (n = 297) from January 1989. Operation for the aneurysm was performed in 192 patients (reasons for not operating were small size of the aneurysm, other contraindication). There were 5 deaths, all related to coronary artery disease. Coronary bypass was performed in 42 patients either before (n = 38) or at the same time (n = 4) as the operation for the aneurysm of the aorta. There were no operative deaths. These results clearly demonstrate the importance of search and treatment of associated coronary lesions in all patients with an aneurysm of the subrenal abdominal aorta. Coronary lesions should be treated whenever morphology allows.  相似文献   
103.
Changes of terpene content in milk from cows grazing natural diversified upland pasture were examined in this observational trial. A homogeneous plot divided into 2 subplots was used from May 31 to July 1, 2003 (first growth) and again from October 1 to October 7, 2003 (vegetative regrowth). Each subplot was grazed by 6 dairy cows in 2 ways: strip grazing (SG), with new allocations of pasture strips at 2-d intervals, and paddock grazing (PG). The PG subplot was divided into 3 paddocks and the cows were moved to a new paddock on June 13 and June 24, 2003. Milk from the 6 cows was collected twice a week, pooled, and used for terpene analyses by dynamic headspace gas chromatography-mass spectrometry system. Twenty mono- and 23 sesquiterpenes desorbing from the milk fat were separated. The most abundant monoterpenes were β-pinene, α-pinene, γ-terpinene, limonene, α-tujene, terpinolene, and α-phellandrene. The most abundant sesquiterpenes were β-caryophyllene, α-copaene, β-cedrene, transmuurola-4-(14)-5-diene, β-bisabolene, and δ-cadinene. Both mono- and sesquiterpenes in SG milk increased across time with an 8-fold increase in total terpenes in milk from the beginning to the end of June. In parallel, dicotyledons, including the main terpene-rich plants, increased from 17 to 31% of total biomass of the vegetation and the development of Dactylis glomerata progressed from boot to ripening stage. The terpenes in PG milk were equivalent to those in SG milk for the first paddock at the beginning of June and remained constant or doubled for the sum of mono- and sesquiterpenes, respectively. The lower variability of the PG milk terpene content could be related to the opportunity that PG cows had to choose ingested herbage, whereas the SG cows had limited choice within the smaller allocated pasture strips. Milk from cows grazing regrowth pastures in October contained low levels of terpenes, and values were similar for PG and SG milks. Change in the sum of monoterpenes is representative of changes for most monoterpenes (except for limonene) and, conversely, the change in the sum of sesquiterpenes mainly reflected changes in β-caryophyllene and α-copaene. In addition to effects of botanical composition of pasture, it appears that terpene content in milk may vary according to factors linked to grazing management that need more intensive study. Nevertheless, current results raise questions about the precision of terpenes as feed tracers.  相似文献   
104.
105.
In the past decade, long-term sorption and thermochemical heat storage has generated lot of interest. This paper presents the state of the art in this field of research, materials used in these systems and technological difficulties that researchers are set against. An emphasis is put on recent demonstrative projects including absorption and adsorption for long-term solar energy storage. It emerges that considerable breakthrough have been made. Even though there is no mature long-term sorption or thermochemical energy storage yet, primarily due to the high cost of materials, the suitability of this technology to long-term storage remains its main power of attracting.  相似文献   
106.
The stress induced leakage current (SILC) in Si/SiO2 structures with thin gate oxides has a steady-state component which increases drastically when the oxide thickness decreases. It is generally agreed that the SILC is due to electron tunnelling trough stress-induced traps. However, it was observed that the SILC, created by Fowler–Nordheim injection, decays continuously when, after stress, the samples are positively or negatively biased at a low voltage. The decay is irreversible as long as the gate oxide is not biased at a high voltage. The present article adds complementary observations. It shows, first that the above phenomenon is observed in 3.5 nm thick oxides, secondly, that this phenomenon is stable as long as the temperature stays below 200°C, and thirdly, that during the SILC decay, the interface state density does not diminish.  相似文献   
107.
A series of new cationic surfactants was prepared by condensation of lactic acid with N,N-dimethyl propylamine, followed successively by acetylation with acid chloride or ester and by quaternization with dimethylsulfate. Each surfactant and its precursors' structural assignments were based on infrared spectra and 1H and 13C nuclear magnetic resonance spectra. Critical micelle concentrations, contact angles, kinetics of drop spreading, and foam capacities were determined.  相似文献   
108.
Muscle models are useful in bio-inspired robotic, because they allow to reproduce accurately natural motion. When they are used for robotic issue, they need to be compact and embeddable. The non-integer model order has the advantage to ensure a parametrical parsimony that permits to implant it easily on an embedded system. Thus, a fractional multi-model of muscle was identified and presented in later paper. This model is able to predict the response of a motor unit to an electrical stimulation, considering isometric contractions (that is to say, muscle length is constant). There are three different physiological types of motor unit (FR, FF, and S). The aim of this work is to study muscle length impact on the multi-model and the limitations of the linear multi-model. Previous paper was published using FR type motor unit. In this paper, the results of the study using S type motor unit are presented.  相似文献   
109.
Cluster computers represent a cost-effective alternative solution to supercomputers. In these systems, it is common to constrain the memory address space of a given processor to the local motherboard. Constraining the system in this way is much cheaper than using a full-fledged shared memory implementation among motherboards. However, memory usage among motherboards can be unfairly balanced.  相似文献   
110.
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