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   145篇
  免费   9篇
电工技术   1篇
化学工业   40篇
金属工艺   3篇
机械仪表   5篇
建筑科学   6篇
矿业工程   1篇
能源动力   15篇
轻工业   29篇
石油天然气   2篇
无线电   3篇
一般工业技术   20篇
冶金工业   15篇
原子能技术   3篇
自动化技术   11篇
  2023年   3篇
  2022年   10篇
  2021年   9篇
  2020年   5篇
  2019年   4篇
  2018年   8篇
  2017年   7篇
  2016年   6篇
  2015年   1篇
  2014年   7篇
  2013年   18篇
  2012年   15篇
  2011年   15篇
  2010年   7篇
  2009年   3篇
  2008年   7篇
  2007年   1篇
  2006年   7篇
  2005年   4篇
  2004年   2篇
  2003年   3篇
  2002年   1篇
  1998年   1篇
  1997年   1篇
  1996年   2篇
  1995年   1篇
  1991年   2篇
  1990年   1篇
  1987年   1篇
  1981年   2篇
排序方式: 共有154条查询结果,搜索用时 31 毫秒
1.
Diabetic neuropathy (DN), the most common chronic and progressive complication of diabetes mellitus (DM), strongly affects patients’ quality of life. DN could be present as peripheral, autonomous or, clinically also relevant, uremic neuropathy. The etiopathogenesis of DN is multifactorial, and genetic components play a role both in its occurrence and clinical course. A number of gene polymorphisms in candidate genes have been assessed as susceptibility factors for DN, and most of them are linked to mechanisms such as reactive oxygen species production, neurovascular impairments and modified protein glycosylation, as well as immunomodulation and inflammation. Different epigenomic mechanisms such as DNA methylation, histone modifications and non-coding RNA action have been studied in DN, which also underline the importance of “metabolic memory” in DN appearance and progression. In this review, we summarize most of the relevant data in the field of genetics and epigenomics of DN, hoping they will become significant for diagnosis, therapy and prevention of DN.  相似文献   
2.
The gravity flow characteristics of pharmaceutically important granules were studied in a cylindrical hopper with attachable orifice disk at the bottom. Results indicate that materials property and orifice diameter play key role in determining mass flow rate while keeping environmental condition (temperature) at fixed range. A new dimensionally analyzed equation was developed to predict gravity flow of pharmaceutically important granules. The developed correlation agreed well with the experimental data. Calcium gluconate and lactose were used for preparing granules. Generally, glidant/lubricant materials are added to pharmaceutical granules during tablet manufacturing process, in order to improve physical property of granular material. Hence, the effect of glidant/lubricant on mass flow of granules through hopper was also studied. Magnesium stearate (1.5%) was added as glidant before granulation.  相似文献   
3.
Due to the extensive growth of grid computing networks, security is becoming a challenge. Usual solutions are not enough to prevent sophisticated attacks fabricated by multiple users especially when the number of nodes connected to the network is changing over the time. Attackers can use multiple nodes to launch DDoS attacks which generate a large amount of security alerts. On the one hand, this large number of security alerts degrades the overall performance of the network and creates instability in the operation of the security management solutions. On the other hand, they can help in camouflaging other real attacks. To address these issues, a?correlation mechanism is proposed which reduces the security alerts and continue detecting attacks in grid computing networks. To obtain the more accurate results, a?major portion of the experiments are performed by launching DDoS and Brute Force (BF) attacks in real grid environment, i.e., the Grid??5000 (G5K) network.  相似文献   
4.
A two-stage mathematical model was developed to describe adsorbate removal in a dead-end powdered activated carbon/ultrafiltration (PAC/UF) membrane process. Para-nitrophenol (PNP) was used as the model organic compound. The first stage accounted for adsorbate removal during transport from the initial PAC contact with the PNP solution to the membrane system, and the second stage accounted for additional PNP removal due to the retention of the PAC in a growing bed on the membrane surface. The PAC adsorptive capacity was described using the Langmuir isotherm, whose parameters were estimated from isotherm experiments. Transport of the PNP through the PAC particle was described using the homogeneous surface diffusion model and the surface diffusivity was estimated from batch experiments. The two stage model predicted the effluent concentrations from the PAC/UF process during the early stages of the experiments, but model improvements are required to more accurately predict the latter stages. A batch model can be used to describe the effluent PNP concentration from the PAC/UF process if dispersion is neglected.  相似文献   
5.
The authors examined the degree to which workers were engaging in financial, health, interpersonal/leisure, and work planning for retirement, exploring whether demographic and psychological variables inhibited or promoted planning in each of these domains. Planning in each domain was influenced by a unique set of variables. Goals emerged as a consistent and positive predictor of planning. Gender accounted for health and interpersonal/leisure planning, while work planning behavior was negatively predicted by income. Time perspective also helped to clarify the amount of retirement planning undertaken in the financial and interpersonal/leisure domains. Practical implications for designing retirement interventions are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
6.
Sulfur was impregnated onto activated carbon fibers (ACFs) through H2S oxidation catalyzed by the sorbent surface in a fixed-bed reactor. By changing the temperature and duration of the sulfur impregnation process, ACFs with different sulfur contents were developed. Characterization of ACFs before and after sulfur impregnation was conducted by surface area analysis, energy dispersive X-ray analysis, thermogravimetric analysis, X-ray photoelectron spectroscopy, and temperature programmed desorption. Vapor phase mercury adsorption experiments were carried out in a fixed-bed reactor. Sulfur was impregnated mainly as elemental sulfur and the amount of sulfur deposited on the ACF increased with an increase in impregnation temperature. Higher temperature leads to more uniform sulfur distribution inside the sorbent pores. The impregnation process can be explained by a combination of pore filling and monolayer adsorption, with the former mechanism predominating at low temperatures. In the absence of sulfur, the mercury adsorption capacity can be correlated with surface area and pore volume.  相似文献   
7.
A study of the contact mechanisms between a resonator probe sensor and a broad range of engineering surfaces is presented. The resonator-based touch sensor used in these studies consists of a prismatic beam clamped at one end with a spherical probe attached at the other. Pairs of piezoelectric (PZT) elements cemented at either side of the beam along its axis are employed; one to actuate and the other to pick up the strain signals. Over a band of frequencies near to a resonance, the sensor behaves like second-order system. When oscillated near to its resonant frequency, interactions between the probe tip and specimen are detected by monitoring phase or frequency shifts using phase-locking techniques. As the probe approaches and contacts a surface, a range of phenomena are observed. Approximate theoretical models have been developed to predict the effects characteristic of added mass, stiffness, and damping (i.e., kinetic, potential and dissipative energy transfer) for contacts between clean solids and when contaminant films are present. These models predict that phase and frequency shifts can either increase or decrease depending upon the dominant phenomena in the contact region. For example, when a solid surface is contacted by a clean probe, the resonant frequency can either increase or decrease depending upon the ratio of elastic modulus to density, and this is demonstrated with contact measurements made on metals and rubbers. A systematic method for the identification of the dominant effect (if there is one) based on observations of frequency or phase shifts using either constant phase or constant frequency monitoring is presented.  相似文献   
8.
Desorption of hydrogen atoms from the (110) surface of rutile magnesium hydride (MgH2) was investigated using density functional theory (DFT) and pseudopotential method. System was represented by (110) (2×2) slab MgH2 supercell with 12 atomic layers along the z-axis. The H-desorption was modeled by the successive release of the four two-fold bonded H atoms from the (110) surface of MgH2. Dependence of the H-desorption energy on number and configuration of remaining surface hydrogen atoms has been determined. The features of the H atoms diffusion from the bulk towards the surface have been investigated, too. The results suggest that decrease in number of surface H atoms generally lowers the H-desorption energy in each desorption step and that both the H–H and the Mg–H interatomic interactions strongly influence the H-desorption process. The hydrogen vacancy formation energy in the first three sub-surface layers also exhibits a pronounced dependence on concentration. These findings lead to the conclusion that tendency of the MgH2 (110) surface to preserve a maximum possible surface H concentration in its most stable configuration is the limiting factor for the H-desorption kinetics. In principle, the obtained results allow us to determine preferred paths of surface and sub-surface H-diffusion for a wide range of H concentrations and the principle features of the MgH2 dehydrogenation process, at least for the H-rich region. Being rather comprehensive, the approach is applicable for other metal hydrides, as well.  相似文献   
9.
The advent of readily accessible, inexpensive Web-conferencing applications has opened the door for distance psychotherapy supervision, using video recordings of treated clients. Although relatively new, this method of supervision is advantageous given the ease of use and low cost of various Internet applications. This method allows periodic supervision from point to point around the world, with no travel costs and no long gaps between direct training contacts. Web-conferencing permits face-to-face training so that the learner and supervisor can read each other's emotional responses while reviewing case material. It allows group learning from direct supervision to complement local peer-to-peer learning methods. In this article, we describe the relevant literature on this type of learning method, the practical points in its utilization, its limitations, and its benefits. (PsycINFO Database Record (c) 2011 APA, all rights reserved)  相似文献   
10.
The adsorption and the redox processes of two first-generation salicylaldiamine dendritic ligands and their copper, cobalt and nickel metallo-functionalized complexes have been studied at two types of carbon electrode surface. Glassy carbon (GC) was used in an electrochemistry study and highly oriented pyrolitic graphite (HOPG) in ex situ atomic force microscopy (AFM) imaging. All salicylaldimine ligands and their metallo-functionalized complexes adsorb on the surface of the HOPG electrode, resulting in the formation of nanoclusters and films, which vary between 0.9 and 6 nm in size, depending on the metallo-functionalized salicylaldimine dendrimer chemical composition and solution concentration. Differential pulse voltammetry of the surface-confined films has shown that the anodic reactions observed correspond to the oxidation of the hydroxyl groups present in the ligand structure of all compounds. However, by following the changes in peak currents, potentials and width at half height it has been shown that destabilization of the ligand internal structure occurred in the metallo-functionalized complexes depending on the metal involved. The electrochemical behaviour of the surface-confined films observed in buffer solution was related to the morphology, obtained by AFM, of the immobilised first-generation salicylaldiamine dendritic ligands and corresponding salicylaldimine metallo-functionalized complexes.  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