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   687篇
  免费   24篇
  国内免费   2篇
电工技术   49篇
综合类   4篇
化学工业   184篇
金属工艺   7篇
机械仪表   9篇
建筑科学   5篇
能源动力   34篇
轻工业   44篇
水利工程   2篇
石油天然气   2篇
无线电   52篇
一般工业技术   158篇
冶金工业   86篇
原子能技术   19篇
自动化技术   58篇
  2023年   3篇
  2022年   7篇
  2021年   17篇
  2020年   3篇
  2019年   9篇
  2018年   8篇
  2017年   14篇
  2016年   15篇
  2015年   10篇
  2014年   28篇
  2013年   41篇
  2012年   31篇
  2011年   39篇
  2010年   27篇
  2009年   33篇
  2008年   45篇
  2007年   33篇
  2006年   38篇
  2005年   34篇
  2004年   22篇
  2003年   17篇
  2002年   22篇
  2001年   11篇
  2000年   9篇
  1999年   13篇
  1998年   32篇
  1997年   19篇
  1996年   16篇
  1995年   19篇
  1994年   17篇
  1993年   13篇
  1992年   5篇
  1991年   7篇
  1990年   6篇
  1989年   4篇
  1987年   2篇
  1986年   3篇
  1985年   6篇
  1984年   5篇
  1983年   7篇
  1982年   2篇
  1981年   5篇
  1979年   1篇
  1978年   2篇
  1977年   1篇
  1976年   4篇
  1975年   2篇
  1974年   1篇
  1971年   1篇
  1969年   1篇
排序方式: 共有713条查询结果,搜索用时 15 毫秒
701.
For improving the ozone consumption efficiency (OCE) of the ozone-electrolysis process, an ozone-electrolysis system with an independent electrolytic cell from an ozone contactor (indirect ozone injection system) and a three-dimensional electrode were introduced in this study. The reactor successfully enhanced the OCE and the ratio of 1,4-dioxane degradation rate to ozone injection rate (RDO) in comparison with the previous reactor. The three-dimensional electrode also contributed the improvement of the OCE and the RDO due to lowering the current density on the cathode. As the indirect ozone injection system allows higher degree of freedom for the reactor design, it is useful for application of ozone-electrolysis to practical water treatments.  相似文献   
702.
One of the key challenges for the design of sustainable chemical processes is to incorporate such concepts in the early phases of process design. In recent years, a few frameworks have been published to this direction, focusing mainly on continuous processes. However, the wide use of batch processes for the production of “low volume high value” chemicals makes the extension of such frameworks to this production environment indispensable. In the present study a recently presented multi-stage framework for multi-objective continuous process assessment is modified to incorporate batch process design aspects (e.g., cycle times, equipment utilization) in the form of early design phase indicators. Accordingly, a Productivity Loss Index (PLI) is defined for estimating periodic costs and environmental impacts, economic and environmental indicators are adjusted and a procedure to generate a base case separation process flowsheet is implemented. The modified framework is demonstrated on the design of a production process for 4-(2-methoxyethyl)-phenol considering seven potential synthesis routes.  相似文献   
703.
A two-dimensional, sheet-like dielectric barrier discharge microplasma that can be generated in supercritical fluids was developed. With this type of plasma, generated in supercritical xenon, nanocrystalline diamonds and diamondoid-like sp3 bonded nano-hydrocarbons were synthesized by using adamantane as a precursor and seed. Pressure and temperature were set close to the critical point of xenon at 6.3 MPa and 290.2 K, respectively. The peak-to-peak voltage for microplasma generation was between 3.4 and 7.1 kV, at a frequency of 10 kHz and the power consumption of the microplasma determined from the I-V measurements reached about 30 mW. Transmission electron microscopy analysis of the lattice of the synthesized particles revealed crystal structures similar to those observed in nanodiamonds, while micro-Raman spectra yielded features also found in Raman and ab initio computational studies of diamondoids.  相似文献   
704.
Vascular endothelial cells cover the luminal surface of blood vessels and contribute to the prevention of vascular disorders such as atherosclerosis. Metallothionein (MT) is a low molecular weight, cysteine-rich, metal-binding, inducible protein, which protects cells from the toxicity of heavy metals and active oxygen species. Endothelial MT is not induced by inorganic zinc. Adequate tools are required to investigate the mechanisms underlying endothelial MT induction. In the present study, we found that an organoantimony compound, tris(pentafluorophenyl)stibane, induces gene expression of MT-1A and MT-2A, which are subisoforms of MT in bovine aortic endothelial cells. The data reveal that MT-1A is induced by activation of both the MTF-1–MRE and Nrf2–ARE pathways, whereas MT-2A expression requires only activation of the MTF-1–MRE pathway. The present data suggest that the original role of MT-1 is to protect cells from heavy metal toxicity and oxidative stress in the biological defense system, while that of MT-2 is to regulate intracellular zinc metabolism.  相似文献   
705.
Abstract

To improve the water resistance of bamboo flour/high-density polyethylene (HDPE) composites, the effects of plastic content, coupling agents, and the addition of micro-fibrillated cellulose (MFC) on formulations were studied, and their rheological and mechanical properties were evaluated. The composites were prepared by injecting molding with a basic composition of equivalent amounts of bamboo flour and HDPE, and the melting fluidity of the compounds, tensile strength, and tensile modulus of the composites were determined. An increase in water resistance was detected in all three tests. By increasing the plastic content, negative effects such as a decreased tensile modulus were observed. When evaluating the compatibility between bamboo flour and plastic using coupling agents and MFC addition, positive effects were noted for water resistance, melting fluidity, and tensile modulus. We also confirmed that the procedure used to increase the compatibility between bamboo flour and plastic could easily be used for industrial applications by changing the coupling agents. Overall, a novel positive property (increased tensile modulus) and an increased water resistance were observed after MFC addition.  相似文献   
706.
One of the strengthening methods of composite connection is the employment of reinforcing elements in the adhesive layer. Using of additional elements in the adhesive layer make uniform stress distribution and improves the strength and toughness of the connection. In this paper, metal wires were used to reinforce the adhesive joints of composites. The effects of the number of wires, wire diameter, wire stiffness, angle of wire and the adhesive type on the strength of the adhesive reinforced bonded composite joints were investigated experimentally and numerically. A finite element model was developed to study the stress distribution in the reinforced adhesive joints. The numerical results showed a good agreement with the experimental observation. It was found that increasing the number of wires and wire diameter, choosing a stiffer material for the wire and increasing the wire angle, uniform the stress distribution and reduced the maximum and average stress values in the adhesive layer. For the appropriate reinforcing wire parameters, the joint strength increased more than 90% in this study. It also observed that the using metal wires as a reinforcing element was more effective in the ductile adhesion than the brittle ones.  相似文献   
707.
The objective of this study is to make clear the effect of neutron irradiation on mechanical properties of laser weldments using irradiated material. This estimation is necessary for the application to joining coolant piping of the ITER blanket. Irradiation testing was performed at Japan Material Testing Reactor (JMTR). On the irradiation condition for weldments using irradiated material, fast neutron fluence was 1.4 × 1024 n/m2, which corresponds to a displacement damage rate of 0.26 displacement per atom (dpa) and irradiation temperature 200 °C. The results of this study show that tensile properties of all weldments changed into that of base material by the effect of neutron irradiation. The results of hardness tests show that irradiation hardening at an irradiation damage dose of 0.3 dpa is almost same as that at irradiation damage 0.6 dpa. It is concluded that irradiated weldments using irradiated material were moved toward irradiated base material on tensile and hardness properties up to 0.6 dpa. On the other hand, tensile properties of base material were changed by the effect of neutron irradiation up to about 0.3 dpa, and with much less change from 0.3 dpa to 0.6 dpa. It is inferred that the effect of neutron irradiation of SS316LN-IG almost saturated up to 0.3 dpa.  相似文献   
708.
Structural changes during the creep process of ultrahigh‐strength polyethylene fiber (UHSPE) were investigated using X‐ray and the solid‐state NMR techniques. As the creep strain increases, the quantity of the amorphous phase area estimated by the 13C‐NMR method increases until the final creep rupture. On the other hand, the amorphous quantity estimated by the X‐ray method does not change noticeably. To explain this contrast, we proposed a new model that illustrates how the defects such as chain ends incorporated into the crystalline phase are excluded from the crystallite and agglomerate to generate a new amorphous area, which has a size hardly detected by the X‐ray method. These small amorphous areas are considered to cause a decrease in the tensile strength and the successive final creep rupture. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 312–320, 2001  相似文献   
709.
The growth responses of Vibrio parahamolyticus to pH, NaCl concentration and temperature changes were studied using serotype O3:K6 and other strains. Growth curves were obtained for 27 different sets of conditions, comprised of three levels of NaCl concentration, pH and temperature. The temperature, pH and NaCl concentrations most favorable for growth were in the order of 25 degrees C, 20 degrees C and 15 degrees C, pH 8, 7 and 5.8, and 1%, 3% and 7%, respectively. The bacteria grew most rapidly at 25 degrees C, at a pH of 7 or 8 in the presence of 1% or 3% NaCl, with the population (initial, ca. 2.5 log CFU/mL) reaching a level log 7 CFU/mL at 12 h. A growth predictive model using the Gompertz equation was generated from the experimental data for any combination of NaCl concentration, pH and temperature within the range used in this study.  相似文献   
710.
Lithium chloride (LiCl) modified magnesium hydroxide (Mg(OH)2) is a potential new material for chemical heat pumps. However, there is insufficient information concerning its dehydration and hydration behavior. In this study, the dehydration and hydration reactions, corresponding to the heat storage and the heat output operations, respectively, of authentic Mg(OH)2 and LiCl-modified Mg(OH)2 were investigated by thermogravimetric methods and near infrared spectroscopy. The dehydration of authentic Mg(OH)2 proceeded as a one-step reaction. In contrast, the dehydration of LiCl-modified Mg(OH)2 occurred in two steps. The dehydration reaction rates were increased by LiCl modification of the Mg(OH)2 surface, while the activation energy for the first-order dehydration reaction was lowered. The mechanism for the hydration reaction of magnesium oxide (MgO) was different to that for the hydration of LiCl-modified MgO. This difference was explained by the effect of the LiCl on the MgO particle surface.  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