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   4265篇
  免费   88篇
  国内免费   4篇
电工技术   41篇
综合类   4篇
化学工业   923篇
金属工艺   95篇
机械仪表   83篇
建筑科学   177篇
矿业工程   11篇
能源动力   107篇
轻工业   403篇
水利工程   29篇
石油天然气   18篇
武器工业   2篇
无线电   356篇
一般工业技术   643篇
冶金工业   743篇
原子能技术   41篇
自动化技术   681篇
  2022年   35篇
  2021年   60篇
  2020年   36篇
  2019年   48篇
  2018年   76篇
  2017年   55篇
  2016年   64篇
  2015年   50篇
  2014年   113篇
  2013年   237篇
  2012年   158篇
  2011年   222篇
  2010年   137篇
  2009年   159篇
  2008年   195篇
  2007年   163篇
  2006年   161篇
  2005年   154篇
  2004年   127篇
  2003年   110篇
  2002年   118篇
  2001年   66篇
  2000年   80篇
  1999年   70篇
  1998年   159篇
  1997年   100篇
  1996年   90篇
  1995年   75篇
  1994年   59篇
  1993年   71篇
  1992年   45篇
  1991年   54篇
  1990年   47篇
  1989年   38篇
  1988年   43篇
  1987年   41篇
  1986年   64篇
  1985年   54篇
  1984年   51篇
  1983年   49篇
  1982年   46篇
  1981年   53篇
  1980年   46篇
  1979年   48篇
  1978年   44篇
  1977年   45篇
  1976年   41篇
  1975年   35篇
  1973年   25篇
  1972年   27篇
排序方式: 共有4357条查询结果,搜索用时 0 毫秒
1.
The TELEMAC project brings new methodologies from the Information and Science Technologies field to the world of water treatment. TELEMAC offers an advanced remote management system which adapts to most of the anaerobic wastewater treatment plants that do not benefit from a local expert in wastewater treatment. The TELEMAC system takes advantage of new sensors to better monitor the process dynamics and to run automatic controllers that stabilise the treatment plant, meet the depollution requirements and provide a biogas quality suitable for cogeneration. If the automatic system detects a failure which cannot be solved automatically or locally by a technician, then an expert from the TELEMAC Control Centre is contacted via the internet and manages the problem.  相似文献   
2.
Roasting coffee led to a drop in the ochratoxin A (OTA) concentration, as measured by the reference method, especially for dark type roasts. The way the beverage was prepared also affected the OTA content, which could paradoxically be higher than that of the initial roasted coffee. Assays on the thermal stability of pure OTA showed that it ought to be found in larger quantities in roasted coffee. This suggested that OTA was masked by reactions with the substrate during roasting. The absence of OTA in green coffee is therefore the best guarantee of safety.  相似文献   
3.
We report on a single‐layer organic memory device made of poly(N‐vinylcarbazole) embedded between an Al electrode and ITO modified with Ag nanodots (Ag‐NDs). Devices exhibit high ON/OFF switching ratios of 104. This level of performance could be achieved by modifying the ITO electrodes with some Ag‐NDs that act as trapping sites, reducing the current in the OFF state. Temperature dependence of the electrical characteristics suggest that the current of the low‐resistance state can be attributed to Schottky charge tunnelling through low‐resistance pathways of Al particles in the polymer layer and that the high‐resistance state can be controlled by charge trapping by the Al particles and Ag‐NDs.  相似文献   
4.
The standard least squares (LS) estimation algorithm is modified in such a way that it becomes passive. Therefore the scope of application of the LS algorithm is extended to those adaptive schemes whose convergence proof is based on passivity. The passive version of LS is presented in both continuous and discrete time.  相似文献   
5.
This study focuses on the visualization of a series of large earthquake simulations collectively called TeraShake. The simulation series aims to assess the impact of San Andreas Fault earthquake scenarios in Southern California. We discuss the role of visualization in gaining scientific insight and aiding unexpected discoveries.  相似文献   
6.
7.
This paper analyses the determination of visibility of journals in which researchers of INRA (National Institute for Agricultural Research) publish. The corpus is comprised of 671 articles published over a period of four years in 258 journals. The advantage of the method applied for determining the visibility of journals is that it combines two approaches: a) bibliometric indicators (coverage by the ISI-publications and by two specific French databases) and b) experts' opinions (10 economists and sociologists). The main results are: a) There is a convergence between the opinion of the experts and «visibility» in the databases, b) The impact factor confirms the main opinions of the experts. The first journals ranked by the experts and JCR Social Sciences are the same but represent only 40 per cent of the total journals analysed. The other journals were revealed by the experts and French databases.«Whoever seeks to pass a balanced but lucid judgement on the general trends of the activity carried out by the profession to which he belongs, is liable to say either banalities or to hurt his colleagues»The notion which we retain of core is that which is successively and conjointly validated by the experts and by the major databases representative of the field.This study was financed by the Department of Rural Economy and Sociology of INRA.  相似文献   
8.
Maltose long-chain fatty acid esters (MFAE), esterified at the 6 and 6′ position, were synthesized with stearic, palmitic, myristic, and oleic groups. Synthesis yields were 15–20% based on initial maltose present, and structural confirmation was obtained using plasma desorption mass spectrometry and nuclear magnetic resonance spectroscopy. These surfactants have surface tensions in the range of 34–36 dyn/cm at their critical micelle concentrations (CMC) of approximately 10−5–10−6 mol/L. The increased chain lengths have a marked effect, reducing CMC values for MFAE by approximately three orders of magnitude over similar carbohydrate-based dodecyl chain sources. Within chain lengths between 14 and 18 carbons, the rate of change in CMC is significant and decreases with increasing chain length for MFAE. The melting points of MFAE are approximately 40°C, and the heat capacities range from 1.6 to 1.9 J/g·K. These numbers are comparable to those of sucrose esters, indicating their applicability in similar uses. However, because MFAE, unlike sucrose, possess an anomeric carbohydrate carbon position, these surfactants maintain their reducing nature and are susceptible to further derivatization. They are also synthesized from renewable, economical carbohydrates and lipids and may provide an excellent alternative to pertrochemical-derived products.  相似文献   
9.
In this paper we study the coordination of different activities in a supply chain issued from a real case. Multiple suppliers send raw materials (RMs) to a distribution center (DC) that delivers them to a unique plant where the storage of the RMs and the finished goods is not possible. Then, the finished goods are directly shipped to multiple customers having just‐in‐time (JIT) demands. Under these hypotheses, we show that the problem can be reduced to multiple suppliers and one DC. Afterwards, we analyze two cases; in the first, we consider an uncapacitated storage at DC, and in the second, we analyze the capacitated storage case. For the first case, we show that the problem is NP‐hard in the ordinary sense using the Knapsack decision problem. We then propose two exact methods: a mixed integer linear program (MILP) and a pseudopolynomial dynamic program. A classical dynamic program and an improved one using the idea of Shaw and Wagelmans are given. With numerical tests we show that the dynamic program gives the optimal solution in reasonable time for quite large instances compared with the MILP. For the second case, the capacity limitation in DC is assumed, which makes the problem solving more challenging. We propose an MILP and a dynamic programming‐based heuristic that provides solutions close to the optimal solution in very short times.  相似文献   
10.
Microsystem Technologies - This paper presents recent advances on two dimensional length-extension mode (2D-LEM) quartz resonators providing high quality (Q) factor on resonances at a few MHz. The...  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