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   3299篇
  免费   201篇
  国内免费   25篇
电工技术   62篇
综合类   2篇
化学工业   875篇
金属工艺   43篇
机械仪表   74篇
建筑科学   158篇
矿业工程   1篇
能源动力   103篇
轻工业   258篇
水利工程   12篇
石油天然气   3篇
武器工业   1篇
无线电   299篇
一般工业技术   590篇
冶金工业   163篇
原子能技术   28篇
自动化技术   853篇
  2024年   5篇
  2023年   41篇
  2022年   134篇
  2021年   152篇
  2020年   78篇
  2019年   92篇
  2018年   100篇
  2017年   93篇
  2016年   150篇
  2015年   116篇
  2014年   148篇
  2013年   224篇
  2012年   210篇
  2011年   239篇
  2010年   200篇
  2009年   201篇
  2008年   193篇
  2007年   168篇
  2006年   122篇
  2005年   99篇
  2004年   119篇
  2003年   99篇
  2002年   66篇
  2001年   51篇
  2000年   43篇
  1999年   38篇
  1998年   38篇
  1997年   23篇
  1996年   39篇
  1995年   27篇
  1994年   29篇
  1993年   20篇
  1992年   19篇
  1991年   10篇
  1990年   6篇
  1989年   11篇
  1987年   12篇
  1986年   5篇
  1985年   16篇
  1984年   18篇
  1983年   10篇
  1982年   9篇
  1981年   8篇
  1980年   3篇
  1979年   8篇
  1978年   4篇
  1977年   8篇
  1976年   7篇
  1975年   3篇
  1973年   3篇
排序方式: 共有3525条查询结果,搜索用时 15 毫秒
81.
The main aim of this study was to identify the most relevant cytokines which, when assessed in the earliest stages from hospital admission, may help to select COVID-19 patients with worse prognosis. A retrospective observational study was conducted in 415 COVID-19 patients (272 males; mean age 68 ± 14 years) hospitalized between May 2020 and March 2021. Within the first 72 h from hospital admission, patients were tested for a large panel of biomarkers, including C-reactive protein (CRP), Mid-regional proadrenomedullin (MR-proADM), Interferon-γ, interleukin 6 (IL-6), IL-1β, IL-8, IL-10, soluble IL2-receptor-α (sIL2Rα), IP10 and TNFα. Extensive statistical analyses were performed (correlations, t-tests, ranking tests and tree modeling). The mortality rate was 65/415 (15.7%) and a negative outcome (death and/or orotracheal intubation) affected 98/415 (23.6%) of cases. Univariate tests showed the majority of biomarkers increased in severe patients, but ranking tests helped to select the best variables to put on decisional tree modeling which identified IL-6 as the first dichotomic marker with a cut-off of 114 pg/mL. Then, a good synergy was found between IL-10, MR-proADM, sIL2Rα, IP10 and CRP in increasing the predictive value in classifying patients at risk or not for a negative outcome. In conclusion, beside IL-6, a panel of other cytokines representing the degree of immunoparalysis and the anti-inflammatory response (IP10, sIL2Rα and IL-10) showed synergic role when combined to biomarkers of systemic inflammation and endothelial dysfunction (CRP, MR-proADM) and may also better explain disease pathogenesis and suggests targeted intervention.  相似文献   
82.
This paper presents a novel system for production of pure oxygen based on the integration of a solid oxide fuel cell (SOFC) and a solid oxide electrolyzer (SOEC). In the proposed arrangement, the SOFC provides electricity, heat and H2O in vapour phase to the SOEC which carries out the inverse reactions of the SOFC, that is the separation of H2O into H2 (used as a fuel for the SOFC) and O2 (representing the yield of the system). Simulations carried out in different operating conditions show that when the integrated SOFC–SOEC device runs at low current densities (less than 1000 A m−2), pure oxygen can be generated with an electric consumption comparable to mid-size cryogenic air separation units, and significantly lower than small scale systems based on the PSA technology.  相似文献   
83.
84.
85.
In this article, we reports the effects of the processing conditions on the morphological and hollow attributes of polystyrene micrometric hollow particles produced by the use of a recently developed technique based on the gas foaming of spherical, dense particles. By modulating the foaming temperature and saturation pressure, we produced hollow particles with different attributes in terms of hollow dimensions, eccentricity, and open–close features. The results from these small systems were compared, and we found agreement with what is typically observed in bulk polymeric foaming, for example, an increase in the foaming efficiency with saturation pressure and the nonmonotonic effect of temperature. Furthermore, we observed an increase in the hollow number when using nucleating agents with respect to the neat polymer and when using nitrogen with respect to carbon dioxide as the blowing agent. The effects of particle manipulation before foaming to achieve hollow elongated or distorted particles are also reported. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44236.  相似文献   
86.
The present paper deals with the synthesis of porous, sintered glass‐ceramics obtained at temperatures below 1150°C, originating from inorganic polymers based on fayalite slag. Firing led to the evaporation of water, dehydroxylation, and oxidation of Fe2+ above 345°C. For heating >700°C, the Si–O stretching band shifted from the 1160 and 750 cm?1 to the 1255 and 830 cm?1 region, due to a structural reorganization of the amorphous phase, whereas Fe–O bands appeared at 550 cm?1. The final microstructure consisted predominantly of an amorphous phase, hematite, and franklinite. The open porosity and compressive strength decreased and increased, respectively, as the firing temperature increased. The final values suggest properties comparable to that of structural lightweight concrete, still, the materials synthesized herein, are lighter, and made primarily from secondary resources.  相似文献   
87.
The direct ink writing of an ink composed of a preceramic polymer and fillers was used to produce hardystonite (Ca2ZnSi2O7) bioceramic scaffolds. Suitable formulations were developed for the extrusion of fine filaments (350 μm diameter) through a nozzle. The preceramic polymer was employed with the double purpose of contributing to the rheology of the ink by increasing its viscosity and of forming the hardystonite phase upon heat treatment by reacting with the fillers. A control of the rheology is essential when spanning features have to be produced, and therefore the main rheological characteristics of the inks were measured (flow curves, dynamic oscillation tests, viscosity recovery tests) and compared to models reported in the literature. Highly porous scaffolds (up to 80% total porosity) were produced and heat treated in air or in nitrogen atmosphere. The influence of the heat‐treatment atmosphere on the morphology, crystalline phase assemblage, and compressive strength of the scaffolds was investigated.  相似文献   
88.
Although the development of super‐resolution microscopy dates back to 1994, its applications have been primarily focused on visualizing cellular structures and targets, including proteins, DNA and sugars. We now report on a system that allows both monitoring of the localization of exogenous small molecules in live cells at low resolution and subsequent super‐resolution imaging by using stochastic optical reconstruction microscopy (STORM) on fixed cells. This represents a powerful new tool to understand the dynamics of subcellular trafficking associated with the mode and mechanism of action of exogenous small molecules.  相似文献   
89.
90.
Several studies on Emergency Management are available in the literature, but most of them do not consider how the human behavior during an emergency can affect the evacuation process. Therefore, the novel contribution of this article is the implementation of an agent‐based model to describe the evacuation, due to a blast in a public area, integrated with a human behavior analytical model. Each agent has its own behavior that is described in a layered framework. The first layer simulates the “agent's features” function. Then, an “individual module” describes dynamically the emotional aspects using (i) the Decision Field Theory, (ii) a stationary stochastic model, and (iii) the results coming from a questionnaire. An agent‐based model with integrated human behavior is proposed to test critical infrastructures in emergency conditions without performing full scale evacuation tests. Analyses could be performed both in real time with a hazard scenario and at the design level to predict the system response to identify the optimal configuration. Therefore, the development of the proposed methodology could support both designers and policy makers in the decision‐making process.  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