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   2065篇
  免费   17篇
  国内免费   9篇
电工技术   22篇
综合类   2篇
化学工业   230篇
金属工艺   14篇
机械仪表   16篇
建筑科学   49篇
矿业工程   1篇
能源动力   20篇
轻工业   128篇
水利工程   6篇
石油天然气   41篇
武器工业   1篇
无线电   96篇
一般工业技术   243篇
冶金工业   1113篇
原子能技术   12篇
自动化技术   97篇
  2021年   6篇
  2020年   10篇
  2019年   9篇
  2018年   11篇
  2017年   9篇
  2016年   7篇
  2014年   12篇
  2013年   37篇
  2012年   30篇
  2011年   66篇
  2010年   38篇
  2009年   33篇
  2008年   45篇
  2007年   36篇
  2006年   36篇
  2005年   36篇
  2004年   32篇
  2003年   49篇
  2002年   47篇
  2001年   32篇
  2000年   22篇
  1999年   55篇
  1998年   326篇
  1997年   190篇
  1996年   119篇
  1995年   101篇
  1994年   77篇
  1993年   85篇
  1992年   30篇
  1991年   36篇
  1990年   27篇
  1989年   31篇
  1988年   26篇
  1987年   18篇
  1986年   27篇
  1985年   25篇
  1984年   17篇
  1983年   23篇
  1982年   16篇
  1981年   20篇
  1980年   19篇
  1979年   15篇
  1978年   10篇
  1977年   38篇
  1976年   77篇
  1975年   9篇
  1974年   10篇
  1973年   13篇
  1972年   7篇
  1971年   7篇
排序方式: 共有2091条查询结果,搜索用时 15 毫秒
11.
K.Y. Wang  R.E. West  F. Kreith  P. Lynn 《Energy》1985,10(10):1165-1175
Alkali-metal carbonate salts meet the requirements for high-temperature solar central receiver systems, but because of their corrosiveness they present special problems in the design of storage tanks. In order to reduce corrosion and temperature sufficiently to retain strength in the storage containing wall, internal and thermal insulation is required. We present design options and operation criteria for sensible-heat, molten-salt storage with internal insulation.  相似文献   
12.
PURPOSE: Links between food service characteristics and residents' risk of malnutrition were examined. METHODS: Cognitively intact residents meeting inclusion criteria and living in one of 38 participating nursing homes were randomly sampled. The final sample consisted of 132 residents, who were screened for risk of malnutrition and completed a face-to-face interview questionnaire about dining experiences. Additional data came from participants' medical charts, and each institution's food service manager completed a written questionnaire. Frequencies and logistic regressions were used to describe the sample and to examine relationships between risk of malnutrition and food service characteristics. RESULTS: Overall, 37.4% of participants were at risk of malnutrition. Food service factors, including food packages, lids, and dishes that were difficult to manipulate (b=0.285, p=0.009), bulk food-delivery systems (b=1.329, p=0.036), overall food satisfaction (b=0.253, p=0.044), menu cycle length (b=-2.162, p=0.003), and porcelain dishes (b=-0.345, p=0.052), all were significantly associated with risk of malnutrition. CONCLUSIONS: Our findings clearly show a need for nursing homes to modify certain aspects of food service that may increase the risk of malnutrition among cognitively intact residents.  相似文献   
13.
铁电纳米粒子悬浮在向列相液晶母体中,增强介电各向异性,而且对施加的电场信号敏感。本文也展示了纳米粒子对所述复合材料可实现的总的相变的作用。这种方法也许可应用于设计新型显示材料。  相似文献   
14.
Successful Aging     
This issue's Works in Progress department presents six abstracts for projects that are developing interesting solutions to the elderly's quality of life challenges. The first two abstracts discuss projects that will help provide the elderly with freedom and independence by instrumenting their environments with supportive technology. The next two abstracts discuss projects building specialized user interfaces for addressing some of the challenges associated with aging, such as vision impairment. The final two abstracts present projects that will aid independence for the elderly by providing remote monitoring and assistance.  相似文献   
15.
We reviewed 187 depth recorded seizures in 33 patients with non-lesional temporal lobe complex partial seizures. All patients had a minimum of 1 year follow-up following temporal lobectomy. We classified seizure onset pattern as rhythmic activity, attenuation, or repetitive spikes or spike wave complexes. The most common pattern of seizure onset was rhythmic activity and the next most common pattern was repetitive spikes. Seventy-five seizures (49%) had only one seizure onset pattern, and 79 seizures (51%) had a combination of seizure onset patterns. The degree of hippocampal gliosis strongly predicted the type of seizure onset pattern (Chi square = 24.07, 2 d.f., P < 0.01). The rhythmic activity pattern was associated with mild gliosis, and the repetitive spike pattern was associated with severe gliosis. We classified seizure onset as focal or regional based on the number of electrode contacts that were involved by the ictal EEG. A focal seizure onset was associated with an excellent outcome following temporal lobectomy.  相似文献   
16.
The purpose of this study was to examine whether exposure of rat pups to alcohol postnatally over a period of brain development similar to that of the human 3rd trimester results in a permanent loss of cells in the inferior olivary nucleus. It was hypothesized that a deficit of neurons in the inferior olive, the sole source of climbing fibers, may contribute to the cerebellar dysfunction observed following exposure to alcohol during development. Sprague-Dawley rat pups were artificially reared and administered alcohol over postnatal days 4-9. One artificially reared group received a daily alcohol dose of 4.5 g/kg, administered as a 10.2% solution in 2 of 12 daily feedings (10.2% group). This pattern of alcohol administration resulted in high peak blood alcohol concentrations with near total clearance. The other artificially reared group was fed a diet made isocaloric to the alcohol-containing diet (gastrostomy control group). Pups were allowed to grow to adulthood and killed on postnatal day 115. The total number of neurons in the inferior olivary nucleus was estimated using unbiased stereological methods. Exposure to alcohol resulted in a significant deficit in the number of neurons in the inferior olive at 115 days of age. The total number of neurons in the alcohol-exposed group was 40.12 +/- 8.7 x 10(3), compared with 53.37 +/- 3.7 x 10(3) in the artificially reared controls. These results indicate that there is a permanent deficit of neurons in the inferior olive after postnatal exposure to alcohol.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
17.
This article is a discussion of the use of narrow-band light sources coupled with cameras equipped with band-pass filters to document patterned injuries on human skin. Several case reports are included.  相似文献   
18.
The survival rate of patients admitted to the Royal Prince Alfred Hospital (RPAH) from the central Sydney area with a major injury has improved since regionalization of trauma services in early 1992. This improvement has been attributed to education, better hospital care and changing trauma epidemiology. This study was conducted to assess whether the outcome of patients admitted with haemorrhagic shock had improved. This is proposed as a more subtle indicator of hospital performance than overall survival rates. A prospective before and after study was carried out comparing outcome in the 18 months preceding 1 January 1992 with that in the subsequent 18 months. Entry criteria to the study included all primary retrievals from the central Sydney area to RPAH with injury severity scores (ISS) > 15. Outcomes were compared generally and in those who were in a state of haemorrhagic shock (systolic blood pressure < or = 90 mmHg) on arrival at the emergency department. Three hundred and eight patients were entered into the study. Stratification showed similar numbers, demographic features and mechanisms of injury in the two groups. Forty patients were in a state of haemorrhagic shock on admission. The overall mortality was reduced from 31% to 11% (P < 0.001) over the two phases of the study. The mortality from blood loss in the 40 shocked patients fell from 10/25 in the first period to 2/15 (P = 0.07) in the latter. These improved survival rates were felt to reflect the value of the educational and organizational initiatives introduced following designation of the hospital as a trauma centre.  相似文献   
19.
20.
Metal-insulator-metal, MIM, capacitors have been fabricated using plasma deposited silicon nitride, SiNx, films deposited under varying deposition conditions. The electrical properties of the MIM capacitors and the corresponding physical properties of the SiNx films have been determined. The breakdown field strength of the films, which varied between 0.4–3.0 MVcm−1, has been related to the amount of hydrogen incorporated in the SiNx layers during deposition. Frenkel-Poole conduction through the silicon nitride has been observed at room temperature and this conduction mechanism is shown to be predominant and independent of the breakdown field strength, for the films investigated.  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