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   179篇
  免费   7篇
  国内免费   4篇
电工技术   2篇
化学工业   42篇
金属工艺   2篇
机械仪表   1篇
建筑科学   4篇
能源动力   16篇
轻工业   11篇
水利工程   2篇
石油天然气   5篇
无线电   27篇
一般工业技术   40篇
冶金工业   23篇
原子能技术   1篇
自动化技术   14篇
  2023年   4篇
  2022年   4篇
  2021年   9篇
  2020年   8篇
  2019年   5篇
  2018年   8篇
  2017年   5篇
  2016年   16篇
  2015年   3篇
  2014年   11篇
  2013年   17篇
  2012年   8篇
  2011年   12篇
  2010年   9篇
  2009年   10篇
  2008年   11篇
  2007年   7篇
  2006年   3篇
  2005年   4篇
  2004年   5篇
  2003年   2篇
  2002年   1篇
  2001年   3篇
  1999年   4篇
  1998年   4篇
  1997年   3篇
  1996年   1篇
  1995年   4篇
  1994年   3篇
  1993年   1篇
  1991年   1篇
  1988年   1篇
  1985年   3篇
排序方式: 共有190条查询结果,搜索用时 15 毫秒
181.
An approach to automated outlining the left ventricular contour and its bounded area in gated isotopic ventriculography is proposed. Its purpose is to determine the ejection fraction (EF), an important parameter for measuring cardiac function. The method uses a modified version of the fuzzy C-means (MFCM) algorithm and a labeling technique. The MFCM algorithm is applied to the end diastolic (ED) frame and then the (FCM) is applied to the remaining images in a “box” of interest. The MFCM generates a number of fuzzy clusters. Each cluster is a substructure of the heart (left ventricle, ...). A cluster validity index to estimate the optimum clusters number present in image data point is used. This index takes account of the homogeneity in each cluster and is connected to the geometrical property of data set. The labeling is only performed to achieve the detection process in the ED frame. Since the left ventricle (LV) cluster has the greatest area of the cardiac images sequence in ED phase, a framing operation is performed to obtain, automatically, the “box” enclosing the LV cluster. The EF assessed in 50 patients by the proposed method and a semi-automatic one, routinely used, are presented. A good correlation between the two methods EF values is obtained (R=0.93). The LV contour found has been judged very satisfactory by a team of trained clinicians  相似文献   
182.
The purpose of the study was to develop and validate a high-performance liquid chromatography (HPLC) method which can be further applied to understand the mechanism, kinetics, isotherm, and thermodynamics of bile acid adsorption onto bile acid sequestrants. To investigate these properties a HPLC method was developed using peerless C-8 (150 x 4.6?mm, 5?µm) column with a detection wavelength of 200?nm and run time of about 12.5?min. Bile salts glycocholic (GC), glycochenodeoxycholic (GCDC), and taurodeoxycholic acid (TDC), were used and colesevelam hydrochloride was employed as the bile acid sequestrant. The calibration range was found linear from 10 to 6500?mgL?1 for GC and GCDC and 4to 2400?mg L?1 for TDC. The precision was less than 8.8% and accuracy was found well within the range of 85 to 115%. On treating the data with various established models, it was known that, the adsorption kinetics followed the pseudo second order equation indicating chemisorption mechanism. Equilibrium isotherms revealed that the linear form of Langmuir model was the best fit. The separation factor (RL) calculated revealed that the reaction is favorable and reversible. The positive value of heat of sorption (B) calculated from Temkin model indicated towards the exothermic nature of adsorption. The adsorption energy (E) calculated from Dubinin-Kaganer-Radushkevich model was found to be greater than 8 KJmol?1 conforming chemisorption mechanism. The Gibbs free energy calculated established the affinity of bile salts as TDC?>?GCDC?>?GC.  相似文献   
183.
Multispiked gold nanoparticles are required in large quantities for many fundamental studies and applications like (bio)sensing, but their preparation in high yield by the bottom-up chemical synthetic method is challenging. A water-based, non-'seed-mediated', straightforward method for the synthesis of gold nanoparticles with well-developed surface spikes is reported here. The yield of multispiked gold particles is very high (>90%). The method allows the tuning of the number and size of the spikes and the overall size of the particles, and hence the localized surface plasmon resonances of the particles over the broad spectral range in the visible and near-infrared. A mechanism for the evolution of twinned, sharp-tipped surface protrusions has been proposed based on systematic spectrophotometric and transmission electron microscopic studies, which were employed to elucidate the morphological features, structure, chemical composition, and optical properties of the multispiked gold nanoparticles.  相似文献   
184.
Due to their long lifetime and high efficacy, light emitting diodes have the potential to revolutionize the illumination industry. However, self heat and high environmental temperature which will lead to increased junction temperature and degradation due to electrical overstress can shorten the life of the light emitting diode. In this research, a methodology to investigate the degradation of the LED emitter has been proposed. The epoxy lens of the emitter can be modelled using simplified Eyring methods whereas an equation has been proposed for describing the degradation of the LED emitters.  相似文献   
185.
The concentration of hydriodic and sulfuric acid aqueous solutions by membrane distillation (MD) was experimentally investigated. Two commercial hydrophobic membranes, with two different recirculation batch configurations, were tested: direct contact membrane distillation (DCMD) with a polypropylene (PP) capillary membrane, and air-gap membrane distillation (AGMD) with polytetrafluoroethylene (PTFE) flat-sheet membrane. Feed temperatures were 58 °C for DCMD and 80 °C for AGMD, with cooling water at 15 °C and 1 atm operating pressure in both cases. H2SO4 concentration in the feed solution increased from 1.1 up to 7.0 mol/L with the DCMD and from 0.9 up to 10.1 mol/L with the AGMD. HI concentration increased from 0.3 up to 7.0 mol/L with the DCMD and from 0.3 up to 8.0 mol/L with the AGMD. The latter value is higher than the azeotropic concentration of the HI/H2O (7.57 mol/L) mixture and, hence, HI further separation from water can be easily achieved with conventional distillation units. Durability of PTFE membrane in acid solutions was assessed too.  相似文献   
186.
The α-amylase inhibitory activity of 28 varieties of chick pea (Cicer arietinum L) was determined, and KGT/GBS-8 was found to have the greatest activity (81.4 units g?1). The inhibitor was heat labile and the inhibitory activity decreased during germination.  相似文献   
187.
188.
Two-dimensional layered transition metal dichalcogenides have emerged as promising materials for supercapacitors and hydrogen evolution reaction (HER) applications. Herein, the molybdenum sulfide (MoS2)@vanadium sulfide (VS2) and tungsten sulfide (WS2)@VS2 hybrid nano-architectures prepared via a facile one-step hydrothermal approach is reported. Hierarchical hybrids lead to rich exposed active edge sites, tuned porous nanopetals-decorated morphologies, and high intrinsic activity owing to the strong interfacial interaction between the two materials. Fabricated supercapacitors using MoS2@VS2 and WS2@VS2 electrodes exhibit high specific capacitances of 513 and 615 F g1, respectively, at an applied current of 2.5 A g1 by the three-electrode configuration. The asymmetric device fabricated using WS2@VS2 electrode exhibits a high specific capacitance of 222 F g1 at an applied current of 2.5 A g1 with the specific energy of 52 Wh kg1 at a specific power of 1 kW kg1. For HER, the WS2@VS2 catalyst shows noble characteristics with an overpotential of 56 mV to yield 10 mA cm2, a Tafel slope of 39 mV dec−1, and an exchange current density of 1.73 mA cm2. In addition, density functional theory calculations are used to evaluate the durable heterostructure formation and adsorption of hydrogen atom on the various accessible sites of MoS2@VS2 and WS2@VS2 heterostructures.  相似文献   
189.
Scope: Mushrooms are valued as an edible and medical resource for millennia. As macrofungi, they possess conserved molecular components recognized by innate immune cells like macrophages, yet unlike pathogenic fungi, they do not trigger the immune system in the same way. That these well-tolerated foods both avoid immuno-surveillance and have positive health benefits, highlights the dearth of information on the interactions of mushroom-derived products with the immune system. Methods and results: Using powders produced from the common white button mushroom, Agaricus bisporus, it is observed that pre-treatment of mouse and human macrophages with mushroom powders attenuates innate immune signaling triggered by microbial ligands like LPS and  β-glucans, including NFκB activation and pro-inflammatory cytokine production. This effect of mushroom powders is observed at lower doses of TLR ligands, suggesting a model of competitive inhibition whereby mushroom compounds bind and occupy innate immune receptors, precluding activation by microbial stimuli. This effect is preserved following simulated digestion of the powders. Moreover, in vivo delivery of mushroom powders attenuates the development of colitis in a DSS-mouse model. Conclusion: This data highlights an important anti-inflammatory role for powdered A. bisporus mushrooms, which can be further utilized to develop complementary approaches to modulate chronic inflammation and disease.  相似文献   
190.
Due to various structural and optical properties, metal chalcogenide nanomaterials are favorable candidates for different optoelectronic applications. In the current report, Cu2Te/NiTe nanocomposites were synthesized via the facile hydrothermal method. With the variation of concentration of Cu and Ni, various materials had been prepared along with pure Cu2Te and NiTe. The observed several vibrational modes in the material through the Raman spectroscopy are well agreed with the appearing phases. The morphological study confirmed the nanostructures are combination of nanoparticles with sheets. The size of nanoparticles varied in the range of 66–34 nm. The absorbance spectra of the nanocomposite exhibit a blueshift and support the enhancement in the optical bandgap. The value of bandgap energy of the composite samples has been noted in the range of 1.8–2.2 eV. This bandgap range enables the material for various optoelectronic applications such as solar cell and other photovoltaic devices. Thermal analysis of the material demonstrates the presences of several endothermic and exothermic peaks. Thus, several studies on the material prevail its various applicability as optoelectronics as well as other thermal application.  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