全文获取类型
收费全文 | 1628篇 |
免费 | 52篇 |
国内免费 | 183篇 |
专业分类
电工技术 | 34篇 |
综合类 | 71篇 |
化学工业 | 253篇 |
金属工艺 | 112篇 |
机械仪表 | 67篇 |
建筑科学 | 75篇 |
矿业工程 | 8篇 |
能源动力 | 18篇 |
轻工业 | 139篇 |
水利工程 | 49篇 |
石油天然气 | 64篇 |
武器工业 | 2篇 |
无线电 | 133篇 |
一般工业技术 | 657篇 |
冶金工业 | 43篇 |
原子能技术 | 20篇 |
自动化技术 | 118篇 |
出版年
2024年 | 17篇 |
2023年 | 72篇 |
2022年 | 86篇 |
2021年 | 103篇 |
2020年 | 36篇 |
2019年 | 19篇 |
2018年 | 17篇 |
2017年 | 17篇 |
2016年 | 14篇 |
2015年 | 16篇 |
2014年 | 20篇 |
2013年 | 26篇 |
2012年 | 164篇 |
2011年 | 234篇 |
2010年 | 48篇 |
2009年 | 41篇 |
2008年 | 136篇 |
2007年 | 119篇 |
2006年 | 94篇 |
2005年 | 83篇 |
2004年 | 50篇 |
2003年 | 48篇 |
2002年 | 42篇 |
2001年 | 40篇 |
2000年 | 37篇 |
1999年 | 47篇 |
1998年 | 47篇 |
1997年 | 36篇 |
1996年 | 31篇 |
1995年 | 23篇 |
1994年 | 16篇 |
1993年 | 15篇 |
1992年 | 17篇 |
1991年 | 16篇 |
1990年 | 7篇 |
1989年 | 9篇 |
1988年 | 1篇 |
1987年 | 6篇 |
1986年 | 4篇 |
1985年 | 2篇 |
1984年 | 1篇 |
1982年 | 5篇 |
1978年 | 1篇 |
排序方式: 共有1863条查询结果,搜索用时 15 毫秒
991.
Phase change solvents are attractive energy-efficient absorbents for carbon dioxide (CO2) capture due to CO2-rich phase formation. Potassium prolinate + water + ethanol (ProK/W/Eth) solution has shown good capture characteristics as a promising one in our previous work. In this work, absorption rate of CO2, solubility of N2O, and heat of absorption for ProK/W/Eth solution were investigated using a stirred cell reactor and a CPA201 reaction calorimeter and these results were also compared with the aqueous ProK and 30 mass% MEA solutions. Using ethanol as a solvent can substantially increase the CO2 physical solubility and the absorption rate of CO2 in ProK/W/Eth solutions is far higher than that in aqueous 30 mass% MEA solutions especially at a low CO2 loading range. Solid precipitation, obtained from the liquid-to-solid phase change absorption, was analyzed by 13C NMR and DSC-TGA. The enthalpy change for ProK/W/Eth solutions at various CO2 loading was also discussed. 相似文献
992.
Due to the characteristics of hesitant fuzzy sets (HFSs), one hesitant fuzzy element (HFE), which is the basic component of HFSs, can express the evaluation values of multiple decision makers (DMs) on the same alternative under a certain attribute. Thus, the HFS has its unique advantages in group decision making (GDM). Based on which, many scholars have conducted in-depth research on the applications of HFSs in GDM. We have viewed lots of relevant literature and divided the existing studies into three categories: theory, support and methods. In this paper, we elaborate on hesitant fuzzy GDM from these three aspects. The first aspect is mainly about the introduction of HFSs, HFPRs and some hesitant fuzzy aggregation operators. The second aspect describes the consensus process under hesitant fuzzy environment, which is an important support for a complete decision-making process. In the third aspect, we introduce seven hesitant fuzzy GDM approaches, which can be applied in GDM under different decision-making conditions. Finally, we summarize the research status of hesitant fuzzy GDM and put forward some directions of future research. 相似文献
993.
Electro-conductive Nanocrystalline Cellulose Film Filled with TiO2-Reduced-Graphene Oxide Nanocomposite 下载免费PDF全文
Imparting electro-conductive properties to nanocellulose-based products may render them suitable for applications in electronics, optoelectronics, and energy storage devices. In the present work, an electro-conductive nanocrystalline cellulose (NCC) film filled with TiO2-reduced-graphene oxide (TiO2-RGO) was developed. Initially, graphene oxide (GO) was prepared using the modified Hummers method and thereafter photocatalytically reduced using TiO2 as a catalyst. Subsequently, an electro-conductive NCC film was prepared via vacuum filtration with the as-prepared TiO2-RGO nanocomposite as a functional filler. The TiO2-RGO nanocomposite and the NCC/TiO2-RGO film were systematically characterized. The results showed that the obtained TiO2-RGO nanocomposite exhibited reduced oxygen-containing group content and enhanced electro-conductivity as compared with those of GO. Moreover, the NCC film filled with TiO2-RGO nanocomposite displayed an electro-conductivity of up to 9.3 S/m and improved mechanical properties compared with that of the control. This work could provide a route for producing electro-conductive NCC films, which may hold significant potential as transparent flexible substrates for future electronic device applications. 相似文献
994.
Because of high efficiency, energy conservation, simple operation, wide application range, and small size, the high-speed universal pulverizer has been well received by customers. However, its electrical motor can overheat when working, which hinders continuous operation of the pulverizer. In this study, a series of efforts were made to address this problem. Firstly, a detailed analysis of the working principle of the pulverizer was conducted and an optimization plan was proposed, consisting in punching ventilation holes on the surface of the original pulverizer. Simulations of the pulverizer flow field before and after optimization were performed. The hydrodynamic simulation results were used to conduct a steady state thermal analysis of the pulverizer, investigating the influence of the flow field on heat transfer. Additionally, experimental investigations were conducted on the pulverizer before and after optimization in order to measure and compare the parameters (motor working temperature, wind speed and temperature of the motor cooling system, vibration, noise, and pulverizing degree of the material) influencing the performance of the pulverizer. The numerical simulation results showed an increment in heat transfer caused by increment in air flow volume and velocity when air was injected into the pulverizer through bottom and side holes. Experimental results showed that the pulverizer with air injection through holes had the best performance when temperature, vibration, and refinement effect were considered as performance indicators.
The full text can be downloaded at https://link.springer.com/article/10.1007/s40436-017-0208-3 相似文献
995.
996.
We propose a new method for detecting activation in functional magnetic resonance imaging (fMRI) data. We project the fMRI time series on a low-dimensional subspace spanned by wavelet packets in order to create projections that are as non-Gaussian as possible. Our approach achieves two goals: it reduces the dimensionality of the problem by explicitly constructing a sparse approximation to the dataset and it also creates meaningful clusters allowing the separation of the activated regions from the clutter formed by the background time series. We use a mixture of Gaussian densities to model the distribution of the wavelet packet coefficients. We expect activated areas that are connected, and impose a spatial prior in the form of a Markov random field. Our approach was validated with in vivo data and realistic synthetic data, where it outperformed a linear model equipped with the knowledge of the true hemodynamic response. 相似文献
997.
Wang Z Zhang S Ding S Eremin SA Shen J 《Food additives & contaminants. Part A, Chemistry, analysis, control, exposure & risk assessment》2008,25(5):574-582
A new monoclonal antibody (Mab) against sulphamerazine (SMR) was produced and a fluorescence polarisation immunoassay (FPIA) based on the Mab was developed and optimized for the simultaneous qualitative screening of SMR, sulphamethazine (SMZ) and sulphadiazine (SDZ). The Mab, raised from mice immunized with SMR, was bound to bovine serum albumin (BSA) using glutaraldehyde as the coupling reagent. Fluorescein-labelled SMR and SMZ (tracer) were synthesized and purified by thin layer chromatography (TLC). Cross-reactivities below 3.6% were displayed in the optimized FPIA for another 14 sulphonamides when both tracers were employed. The limits of detection (LOD) were 0.9 ng g(-1) for SMR, 2 ng g(-1) for SMZ and 3.1 ng g(-1) for SDZ. Analysis of SMR, SMZ and SDZ fortified chicken muscle and honey samples by the FPIA showed average recoveries of 86-131% with a standard deviation (SD) of 4.6-32. Comparative analyses of a SMZ-treated chicken muscle sample by both FPIA and high performance liquid chromatograph (HPLC) showed a good correlation (r = 0.9991). The study demonstrates the practical application of FPIA in screening chicken muscle and honey samples for sulphonamides residues. 相似文献
998.
Liu K Wang H Chen KJ Guo F Lin WY Chen YC Phung DL Tseng HR Shen CK 《Nanotechnology》2010,21(44):445603
Controlling the size distribution of polymer-based nanoparticles is a challenging task due to their flexible core and surface structures. To accomplish such as task requires very precise control at the molecular level. Here we demonstrate a new approach whereby uniform-sized supramolecular nanoparticles (SNPs) can be reliably generated using a digital microfluidic droplet generator (DMDG) chip. A microfluidic environment enabled precise control over the processing parameters, and therefore high batch-to-batch reproducibility and robust production of SNPs with a very narrow size distribution could be realized. Digitally adjustment of the mixing ratios of the building blocks on the DMDG chip allowed us to rapidly scan a variety of synthesis conditions without consuming significant amounts of reagents. Nearly uniform SNPs with sizes ranging from 35 to 350?nm were obtained and characterized by transmission electron microscopy and dynamic light scattering. In addition, we could fine-tune the surface chemistry of the SNPs by incorporating an additional building block functionalized with specific ligands for targeting cells. The sizes and surface properties of these SNPs correlated strongly with their cell uptake efficiencies. This study showed a feasible method for microfluidic-assisted SNP production and provided a great means for preparing size-controlled SNPs with desired surface ligand coverage. 相似文献
999.
Doraiswamy A Ovsianikov A Gittard SD Monteiro-Riviere NA Crombez R Montalvo E Shen W Chichkov BN Narayan RJ 《Journal of nanoscience and nanotechnology》2010,10(10):6305-6312
Microneedle devices for transdermal delivery of nanoscale pharmacologic agents were fabricated out of organically-modified ceramic (Ormocer) materials using two photon polymerization. Out-of-plane hollow microneedle arrays with various aspect ratios were fabricated using this rapid prototyping process. Human epidermal keratinocyte (HEK) viability on Ormocer surfaces fabricated using two photon polymerization was similar to that on control surfaces. Nanoindentation studies were performed to determine hardness and Young's modulus values for Ormocer materials. Microneedies were shown to enable more rapid distribution of the PEG-amine quantum dot solution to the deep epidermis and dermis layers of porcine skin than topical administration. Our results suggest that two photon polymerization may be used to create microneedle arrays for transdermal delivery of nanoscale pharmacologic agents. 相似文献
1000.
Zhang H Chen D Zhang J Wang Z Cui Y Shen L 《Journal of nanoscience and nanotechnology》2010,10(11):7587-7591
Colloidal CdSe/Zn(0.5)Cd(0.5)Se/ZnSe/ZnS core/multishell quantum dots (QDs) were synthesized by using the well developed successive ion layer adsorption and reaction (SILAR) technique. The UV-vis and PL spectra, TEM, X-ray diffraction and Raman measurement were performed to investigate the structure and optical properties of prepared QDs during the growth of shell layers, which indicated that the stress in CdSe core became stronger with the increasing shell thickness. Due to the gradual adjustment of the lattice parameters in the radial direction and the radial increase of the respective valence- and conduction-band offsets, the optical measurements show a significant enhancement in the photoluminescence quantum yield (QY) and an expedited radiative decay in QDs overcoated with thicker shell. The temperature-dependent optical spectra were measured, and the relation between the microstructure and the optical properties of these core/multishell quantum dots was discussed. 相似文献