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   932篇
  免费   65篇
电工技术   8篇
化学工业   259篇
金属工艺   6篇
机械仪表   30篇
建筑科学   34篇
矿业工程   6篇
能源动力   53篇
轻工业   208篇
水利工程   7篇
石油天然气   2篇
无线电   54篇
一般工业技术   96篇
冶金工业   138篇
原子能技术   6篇
自动化技术   90篇
  2024年   2篇
  2023年   9篇
  2022年   35篇
  2021年   29篇
  2020年   22篇
  2019年   27篇
  2018年   26篇
  2017年   26篇
  2016年   35篇
  2015年   17篇
  2014年   47篇
  2013年   67篇
  2012年   56篇
  2011年   62篇
  2010年   39篇
  2009年   57篇
  2008年   39篇
  2007年   43篇
  2006年   23篇
  2005年   23篇
  2004年   20篇
  2003年   19篇
  2002年   33篇
  2001年   9篇
  2000年   13篇
  1999年   19篇
  1998年   49篇
  1997年   23篇
  1996年   25篇
  1995年   20篇
  1994年   11篇
  1993年   13篇
  1992年   9篇
  1991年   6篇
  1990年   5篇
  1989年   4篇
  1987年   4篇
  1985年   5篇
  1984年   1篇
  1982年   1篇
  1980年   1篇
  1979年   4篇
  1978年   1篇
  1976年   6篇
  1975年   4篇
  1974年   1篇
  1973年   1篇
  1972年   2篇
  1968年   1篇
  1943年   1篇
排序方式: 共有997条查询结果,搜索用时 15 毫秒
81.
Non‐digestible carbohydrate fraction (NDCF) consists of a range of bioactive compounds that escape digestion in the small intestine. NDCF is mainly composed of dietary fibre (DF) and non‐digestible oligosaccharides (NDO). The objective of this work was to analyse directly and compare the NDCF in two Brazilian cultivars of soybean seed with commercial flour. Brazil is the second major soybean producer in the world. The seed cultivars showed on average a NDCF value of 32.80 g per 100 g dry weight (dw). Regarding DF, insoluble DF (IDF) was the main fraction amounting on average to 98%. Uronic acids were significantly higher than neutral sugar (NS) in IDF and soluble DF (SDF) fractions. There was a considerable amount of Klason lignin – on average 84.14% of DF. Regarding NS profile, mannose was the most important sugar in SDF, whereas galactose and arabinose were predominant in IDF. Stachyose was the main oligosaccharide in NDO. DF and NDO were in the same proportion (94.2:5.8) in tested cultivars. No differences in swelling, water retention, or oil retention capacities between seed cultivars were detected. This study on non‐digestible carbohydrate components in soybean seed gives a different approach to the current nutritional knowledge on protein and oil constituents.  相似文献   
82.
New luminescent materials consisting of Eu3+ supported on silica gel functionalized with acetylacetone (EuAPG) and benzoyltrifiuoroacetone (EuBPG) showed a much more intense emission than Eu3+ supported either on silica gel (EuSG) or on silica gel functionalized with imidazole (EuIPG). The lifetimes of the Eu3+5D07F2 transition in the samples were determined. All the silica contained about 0.2–0.3 wt.% of Eu3+.  相似文献   
83.
I have designed two retractors with mobile endoscopes that allow an assistant to lift up the flap and the endoscope. By doing this, the assistant maintains the optical cavity open while the surgeon dissects. There are two models, one with 180-degree lateral swing and the other with motion in all directions (vertical and lateral).  相似文献   
84.
In this paper, we describe the blue photoluminescence (PL) observed in the multi-component oxosalt phosphor GdVO4:Ce3+. Different doping concentrations (0.25–1 mol%) and heat treatment (900–1100 °C) were used to evaluate which conditions would lead to the most suitable blue phosphor for optimal display performance. The cerium doping concentration influences the profile of the emission spectrum (broad peak at 412 nm under UV excitation at 330 nm), as reflected on the values of chromaticity coordinates. On the basis of luminescent properties, we can conclude that, among the phosphors prepared in this work the most adequate for a blue display is the one obtained via the combustion method using glycine as fuel, a 0.50 mol% cerium doping concentration, and heat treatment at 1000 °C.  相似文献   
85.
The influence of the injection of dexamethasone on ketogenesis in 12 day old suckling rats was studied in intestine and liver by determining mRNA levels and enzyme activity of the two genes responsible for regulation of ketogenesis: carnitine palmitoyl transferase I (CPT I) and mitochondrial HMG-CoA synthase. Dexamethasone produced a 2 fold increase in mRNA and activity of CPT I in intestine, but led to a decrease in mit. HMG-CoA synthase. In liver the mRNA levels and activity of both CPT I and mit. HMG-CoA synthase decreased. Comparison of these values with the ketogenic rate of both tissues following dexamethasone treatment suggests that mit. HMG-CoA synthase could be the main gene responsible for the regulation of ketogenesis in suckling rats. The changes produced in serum ketone bodies by dexamethasone, with a profile that is more similar to the ketogenic rate in the liver than that in the intestine, indicate that liver contributes more to ketone body synthesis in suckling rats. Two day treatment with dexamethasone produced no change in mRNA or activity levels for CPT I in liver or intestine. While mRNA levels for mit. HMG-CoA synthase changed little, the enzyme activity is decreased in both tissues.  相似文献   
86.
Forecasting airborne pollen concentrations is one of the most studied topics in aerobiology, due to its crucial application to allergology. The most used tools for this problem are single lineal regressions and autoregressive models (ARIMA). Notwithstanding, few works have used more sophisticated tools based in Artificial Intelligence, as are neural or neuro-fuzzy models. In this work, we applied some of these models to forecast olive pollen concentrations in the atmosphere of Granada (Spain). We first studied the overall performance of the selected models, then considering the data segmented into intervals (low, medium and high concentration), to test how they behave on each interval. Experimental results show an advantage of the neuro-fuzzy models against classical statistical methods, although there is still room for improvement.1  相似文献   
87.
This paper deals with a new method improving the static test for analogue-to-digital converters. The method is based on a histogram procedure using as test signals small-amplitude triangular waves superimposed on suitable constant offset values. The histogram is built over the converter fullscale by varying the offset step by step systematically. A small amplitude and a reduced time slope in comparison to the converter range and slew rate, respectively, lead to static test conditions. This procedure allows inexpensive function generators to be used and the test duration to be dramatically reduced. Experimental results of tests aimed at validating, characterizing, and comparing the proposed method on two different converter architectures are presented.  相似文献   
88.
In this paper we address the use of overdrive in the standard histogram test of analog to digital converters. The error in the estimation of the transition voltages due to the presence of additive noise is calculated and expressions for the minimum amount of overdrive required are presented. A comparison with previously published work is carried out.  相似文献   
89.
Investigated the role of practice tests in predictions about test performance on texts. Generally, Ss predicted their relative performance on tests accurately. However, answering practice-test questions that were drawn from the same pool as criterion-test questions did not improve prediction accuracy. The main reason for this was that practice-test scores for specific texts did not correlate with criterion-test scores. In addition, neither practice tests that were identical to the criterion tests nor practice tests consisting of the question stems improved the accuracy of test predictions relative to no-practice tests. With identical practice and criterion tests, accuracy of self-generated feedback correlated positively with the accuracy of test predictions. For similar practice and criterion tests, however, accurate experimenter-provided feedback reduced test-prediction accuracy, presumably because of the lack of reliability. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
90.
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