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   1503篇
  免费   148篇
  国内免费   78篇
电工技术   11篇
综合类   58篇
化学工业   695篇
金属工艺   23篇
机械仪表   11篇
建筑科学   47篇
矿业工程   33篇
能源动力   77篇
轻工业   66篇
水利工程   9篇
石油天然气   32篇
武器工业   8篇
无线电   15篇
一般工业技术   96篇
冶金工业   248篇
原子能技术   278篇
自动化技术   22篇
  2024年   5篇
  2023年   10篇
  2022年   42篇
  2021年   49篇
  2020年   62篇
  2019年   49篇
  2018年   38篇
  2017年   37篇
  2016年   53篇
  2015年   41篇
  2014年   62篇
  2013年   225篇
  2012年   59篇
  2011年   86篇
  2010年   61篇
  2009年   84篇
  2008年   61篇
  2007年   65篇
  2006年   67篇
  2005年   72篇
  2004年   64篇
  2003年   52篇
  2002年   48篇
  2001年   65篇
  2000年   40篇
  1999年   29篇
  1998年   26篇
  1997年   21篇
  1996年   18篇
  1995年   11篇
  1994年   16篇
  1993年   16篇
  1992年   17篇
  1991年   12篇
  1990年   5篇
  1989年   7篇
  1988年   4篇
  1987年   8篇
  1986年   4篇
  1985年   8篇
  1984年   14篇
  1983年   5篇
  1982年   2篇
  1974年   1篇
  1967年   1篇
  1963年   1篇
  1959年   1篇
  1958年   2篇
  1957年   1篇
  1951年   1篇
排序方式: 共有1729条查询结果,搜索用时 0 毫秒
141.
矿物质催化指数与焦炭反应性关系   总被引:18,自引:1,他引:17  
研究了矿物质(氧化物)以添加和吸附两种方式负载到焦炭中,对焦炭溶剂损反应性的作用规律,建立了矿物质对焦炭溶损反应性的综合评价指标(MCI),提出了煤的Vd和MCI是决定焦炭溶损反应性的两个独立变量,并据此建立了预测焦炭溶损反应性和反应后强度的数学模型。  相似文献   
142.
The surface of a screen-printed carbon electrode (SPCE) was modified by using amorphous carbon nitride (a-CNx) thin film deposited by reactive magnetron sputtering. Scanning electron microscopy and photoelectron spectroscopy measurements were used to characterise respectively the morphology and the chemical structure of the a-CNx modified electrodes. The incorporation of nitrogen in the amorphous carbon network was demonstrated by X ray photoelectron spectroscopy. The a-CNx layers were deposited on both carbon screen-printed electrode (SPCE) and silicon (Si) substrates. A comparative study showed that the nature of substrate, i.e. SPCE and Si, has a significant effect on both the surface morphology of deposited a-CNx film and their electrochemical properties. The improvement of the electrochemical reactivity of SPCE after a-CNx film deposition was highlighted both by comparing the shapes of voltammograms and calculating the apparent heterogeneous electron transfer rate constant.  相似文献   
143.
In a sample of 247 college students, the contributions of adult attachment orientations and several other boundary regulation variables to measures of self-splitting (i.e., the tendency to report diffuse and chaotic self-experiences) and other-splitting (i.e., the tendency to acknowledge unstable perceptions of and feelings toward one's friends) were explored. Adult attachment orientations and self-other boundary regulation variables, respectively, explained unique variance in each criterion measure. High levels of attachment anxiety and self-concealment and low levels of self-other differentiation contributed most prominently to self-splitting, whereas high attachment anxiety, low emotional reactivity, and high needs for social approval best predicted other-splitting. Implications of these findings for advancing a more delineated understanding of splitting tendencies are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
144.
The regime of the nuclear burning wave (NBW) in a fast reactor (FR) is described using the non-stationary diffusion equation for neutron transport and equations of the fuel component burn-up and of nuclear kinetics for precursor nuclei of delayed neutrons. A critical two-zone fast reactor of cylindrical form with metal fuel of the U–Pu cycle is considered. The initiation of nuclear burning in an enriched ignition zone by means of an external neutron flux that is turned off at an early stage of FR operation has been simulated. The possibility of creating a self-organizing regime of a running NBW in the breeding zone along the reactor axis has been demonstrated. The neutron leakage in a transverse direction was taken into account using the concept of radial buckling. The calculation results of the space–time evolution of neutron flux in this system using the effective multi-group approximation are presented. The average fuel burn-up is about 50%. The velocity of NBW propagation strongly depends on the transverse size of FR. For example, in the reactor of 110 cm radius and 500 cm length the NBW velocity is about 22 cm/year.  相似文献   
145.
The controlled hydrolysis of the dichlorine-containing iron(II) clathrochelate FeBd2(Cl2Gm)(BF)2 precursor (where Bd2− and Cl2Gm2− are α-benzyldioxime and dichloroglyoxime dianions, respectively) afforded the hydroxy-containing clathrochelate derivatives with the hydroxyl substituent inherently bound to the ribbed chelate fragment of the macrobicyclic ligand. The triethylammonium and tetra-n-butylammonium salts of the clathrochelate [FeBd2(OClGm)(BF)2] anion have been characterized using elemental analysis, MALDI-TOF mass spectrometry, IR, UV–Vis, 57Fe Mössbauer and 1H, 13C{1H}, 11B and 19F NMR spectroscopies, and X-ray crystallography. The X-ray structural data for this deprotonated anion showed strong delocalization of its negative charge into the clathrochelate framework.  相似文献   
146.
唐河倒虹吸工程是南水北调中线总干渠工程中的大型建筑物之一,主体混凝土截至目前已基本完成,所验收单元工程质量优良率为92%,混凝土内实外光,施工缝连接平顺,无裂缝.现就混凝土施工中的原材料选定、配合比、温度控制、管身混凝土关键部位的施工措施等内容进行了浅释.  相似文献   
147.
Stress corrosion cracking (SCC) raises a lot of questions concerning complexity of stacked physical mechanisms. Synergy between electrochemical processes and mechanical field near the crack tip is now recognized. However, the influence of mechanical behaviour on corrosion processes is not well established and only few works dealt with this effect. Consequently, it seems to be necessary to determine the influence of the plastic strain on the surfaces reactivity in aqueous mediums. The great part of this work was devoted to the development of an electrochemical cell on a bench of mechanical test in order to carry out in situ measurements of current density. Three levels of interaction have been discussed taking into account the different expression of plastic deformation (dislocation density and distribution, slip bands emergence, stress field) in order to study the effect of mechanical state on dissolution, on passivation processes, and on stability of oxide film of polycrystalline nickel in H2SO4 solution.  相似文献   
148.
A new method for estimating reactivity parameters, such as moderator temperature coefficient (MTC) and void reactivity coefficient (VRC), is proposed using steady-state noise data. In order to solve the ill-posed problem of reactivity parameter estimation, a concept of a gray box model is newly introduced. The gray box model includes a first principle based model and a black-box fitting model. The former model acts as a priori knowledge based constraints in a parameter estimation problem. After establishing the gray box and noise source models, the maximum likelihood estimation method based on Kalman filter is applied. Furthermore, it is shown that the frequency domain approach of the gray box model is useful in the case of VRC estimation. The effectiveness of the proposed algorithms is shown through numerical simulation and actual plant data analysis.  相似文献   
149.
The authors evaluated whether completing a multi-item assessment of smoking craving (the Questionnaire of Smoking Urges [QSU]) promoted increases in smoking craving. A sample of 39 regular smokers was randomly assigned to 1 of 3 manipulations (each of 3 min duration): (a) complete the QSU–Brief (10 items), (b) complete a noncraving questionnaire that was structurally identical to the QSU–Brief (scale-based control), and (c) a time-based control. Participants responded to an oral question assessing their degree of craving immediately before and after the manipulations. Results indicated that the QSU did not promote increases in craving compared to the 2 control conditions. Despite continuing debate over the most appropriate self-report measure of craving, investigators who use the QSU–Brief can be reasonably sure that the scores that result are not biased due to reactivity effects. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
150.
This study examined the modulatory function of Duchenne and non-Duchenne smiles on subjective and autonomic components of emotion. Participants were asked to hold a pencil in their mouth to either facilitate or inhibit smiles and were not instructed to contract specific muscles. Five conditions--namely lips pressing, low-level non-Duchenne smiling, high-level non-Duchenne smiling, Ducherme smiling, and control--were produced while participants watched videoclips that were evocative of positive or negative affect. Participants who displayed Duchenne smiles reported more positive experience when pleasant scenes and humorous cartoons were presented. Furthermore, they tended to exhibit different patterns of autonomic arousal when viewing positive scenes. These results support the facial feedback hypothesis and suggest that facial feedback has more powerful effects when facial configurations represent valid analogs of basic emotional expressions. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  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