全文获取类型
收费全文 | 1042篇 |
免费 | 50篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 15篇 |
化学工业 | 239篇 |
金属工艺 | 38篇 |
机械仪表 | 11篇 |
建筑科学 | 72篇 |
矿业工程 | 7篇 |
能源动力 | 15篇 |
轻工业 | 127篇 |
水利工程 | 7篇 |
石油天然气 | 6篇 |
无线电 | 62篇 |
一般工业技术 | 159篇 |
冶金工业 | 222篇 |
原子能技术 | 2篇 |
自动化技术 | 111篇 |
出版年
2023年 | 9篇 |
2022年 | 18篇 |
2021年 | 36篇 |
2020年 | 12篇 |
2019年 | 22篇 |
2018年 | 28篇 |
2017年 | 28篇 |
2016年 | 31篇 |
2015年 | 21篇 |
2014年 | 31篇 |
2013年 | 69篇 |
2012年 | 53篇 |
2011年 | 63篇 |
2010年 | 46篇 |
2009年 | 45篇 |
2008年 | 34篇 |
2007年 | 44篇 |
2006年 | 36篇 |
2005年 | 36篇 |
2004年 | 19篇 |
2003年 | 20篇 |
2002年 | 27篇 |
2001年 | 9篇 |
2000年 | 12篇 |
1999年 | 18篇 |
1998年 | 45篇 |
1997年 | 41篇 |
1996年 | 14篇 |
1995年 | 16篇 |
1994年 | 16篇 |
1993年 | 9篇 |
1992年 | 11篇 |
1991年 | 10篇 |
1990年 | 11篇 |
1989年 | 14篇 |
1988年 | 5篇 |
1987年 | 5篇 |
1986年 | 10篇 |
1985年 | 11篇 |
1984年 | 8篇 |
1983年 | 5篇 |
1980年 | 5篇 |
1977年 | 9篇 |
1976年 | 9篇 |
1975年 | 8篇 |
1974年 | 6篇 |
1973年 | 7篇 |
1971年 | 6篇 |
1966年 | 4篇 |
1960年 | 4篇 |
排序方式: 共有1093条查询结果,搜索用时 15 毫秒
61.
Characterization of activated sludge flocs by confocal laser scanning microscopy and image analysis 总被引:7,自引:0,他引:7
Schmid M Thill A Purkhold U Walcher M Bottero JY Ginestet P Nielsen PH Wuertz S Wagner M 《Water research》2003,37(9):2043-2052
In this study we present a new approach to determine volumes, heterogeneity factors, and compositions of the bacterial population of activated sludge flocs by 3D confocal imaging. After staining the fresh flocs with fluorescein-isothiocyanate, 75 stacks of images (containing approx. 3000 flocs) were acquired with a confocal laser scanning microscope. The self-developed macro 3D volume and surface determination for the KS 400 software package combined the images of one stack to a 3D image and calculated the real floc volume and surface. We determined heterogeneity factors like the ratio of real floc surface to the surface of a sphere with the respective volume and the fractal dimension (D(f)). According to their significant influence on floc integrity and quality, we also investigated the chemical composition of flocs and quantified their bacterial population structure by using group-specific rRNA-targeted probes for fluorescence in situ hybridization. By a settling experiment we enriched flocs with poor settling properties and determined the above-mentioned parameters. This approach revealed shifts in floc volume, heterogeneity, and bacterial and chemical composition according to the settling quality of the flocs. 相似文献
62.
Scouring at Bed Sills as a Response to Flash Floods 总被引:1,自引:0,他引:1
Matteo Tregnaghi Andrea Marion Stephen Coleman 《Canadian Metallurgical Quarterly》2009,135(6):466-475
The temporal development of clear-water local scour depth at bed sills in uniform gravel beds is considered. Experiments are presented on the development of scour holes under unsteady hydraulic conditions, with the triangular-shaped hydrographs tested being of different durations and different rates of flow variation. Based on the experimental results and a theoretical framework, a method is given for the definition and prediction of the scouring process under unsteady flows in terms of a dimensionless temporal parameter. A “flash flood” is here defined as an event for which the scour doesn’t attain its potential magnitude, i.e., the equilibrium value for the peak hydrograph flow rate. This flood nature is dependent on both the characteristics of the flood event itself and the characteristics of the stream. A quantitative measure of what constitutes a flash flood is given in terms of the identified temporal parameter. Results show that the ratio between the final scour depth and the potential scour depth at a bed sill for a given hydrograph can be estimated as a function of the identified temporal parameter. 相似文献
63.
A risk-based strategy for Listeria monocytogenes has been developed by New Zealand Food Safety Authority. Incidents of L. monocytogenes in ready-to-eat foods reported to the regulatory authority were analysed to identify common factors that contributed to the contamination. In addition, the current regulatory framework and available food industry guidance were reviewed to prepare a strategy that will provide a consistent and informed approach to managing the risk of L. monocytogenes. Also recognised is the future impact of an aging population and an increase in the availability and range of chilled ready-to-eat foods that should be integrated into the strategy if an objective of ‘no increase in the reported incidence of foodborne listeriosis after five years’ is to be achieved. 相似文献
64.
Marion Alignan Jane RocheAndrée Bouniols Muriel CernyZephirin Mouloungui Othmane Merah 《Food chemistry》2009
Cereals are an important source of sterols and stanols in the human diet. The present study underlines the effect of genotype and weather conditions in bread wheat, on total sterol and stanol content (TSS), agronomic traits, proteins and ash content under organic conditions. Variations in TSS as well as other characters between two sowing dates were observed. A broad genotypic variability was also reported since extreme genotypes differed by more than 30 mg 100 g−1 DW for TSS, with total stanol content varying twofold. Moreover, two groups of genotypes that differed in agronomic production, ash and protein content were depicted, based on their response to an increase in temperature. This result suggests that the genotypic factor prevails over the sowing date factor for determining sterol and stanol traits in wheat cultivated under organic conditions. Nevertheless, a strong interaction exists between the two factors, which can be used to drive bioaccumulation of these molecules. 相似文献
65.
Ellen Marie Flaten Marion Seiersten Jens-Petter Andreassen 《Chemical Engineering Research and Design》2010
Induction time for precipitation of calcium carbonate precipitated in mono ethylene glycol and water has been studied by conductivity measurements at ethylene glycol concentrations of 0–90 wt% and temperatures from 25 to 80 °C. The supersaturation ratios, S, were in the range of 3–10. The effect of the solvent was separated from the effect of the supersaturation and temperature. Increasing the concentration of ethylene glycol prolongs the induction times for precipitation of CaCO3 considerably although the supersaturation actually increases, especially at lower temperatures. It was shown that this effect cannot be explained by the change in the interfacial tension. Induction time studies in seeded and unseeded experiments were performed in order to separate changes in the nucleation rate from the impact of the growth time in the varying solvent compositions. The results show that crystal growth is retarded, causing the increased induction time in ethylene glycol containing solutions, and hence that the nucleation rate is actually promoted by ethylene glycol. The nucleation rates determined by measured particle numbers and induction times from unseeded experiments were underestimated for the same reason, thereby illustrating the complexity of nucleation rate investigations in mixed solvents. 相似文献
66.
We are interested in an optimal packing density problem for material flows on conveyor belts in two spatial dimensions. The control problem is concerned with the initial configuration of parts on the belt to ensure a high overall flow rate and to further reduce congestion. An adjoint approach is used to compare the optimization results from the microscopic model based on a system of ordinary differential equations with the corresponding macroscopic model relying on a hyperbolic conservation law. Computational results highlight similarities and differences of both optimization models and emphasize the benefits of the macroscopic approach. 相似文献
67.
A critical appraisal of capillary electrochromatography 总被引:1,自引:0,他引:1
68.
69.
M. Kerry Garrett John J. Strain Marion D. B. Allen 《Journal of the science of food and agriculture》1976,27(7):603-611
The composition of the product of algal culture in the liquid phase of slurry has been examined. The material consists of cells of the cultured alga (Chlorella vulgaris) together with those of the endogenous microbial community, and contains approximately 42% true protein, 23% carbohydrate, 16% lipid and 9% nucleic acid. The protein is deficient in the sulphur amino acids but rich in lysine. The latter feature appears to be related to the presence of hexanoic acid in slurry. The endogenous microorganisms do not make a significant direct contribution to the composition of material harvested after algal culture. Light and temperature have only slight effects upon composition of the harvested material. 相似文献
70.
Marion Jeanne Christine Guillemot Thomas Guionnet Florelle Pauchet 《Signal, Image and Video Processing》2007,1(1):77-87
This paper addresses the problem of error-resilient decoding of bitstreams produced by the CABAC (context-based adaptive binary
arithmetic coding) algorithm used in the H.264 video coding standard. The paper describes a maximum a posteriori (MAP) estimation
algorithm improving the CABAC decoding performances in the presence of transmission errors. Methods improving the re-synchronization
and error detection capabilities of the decoder are then described. A variant of the CABAC algorithm supporting error detection
based on a forbidden interval is presented. The performances of the decoding algorithm are first assessed with theoretical
sources and by considering different binarization codes. They are compared against those obtained with Exp-Golomb codes and
with a transmission chain making use of an error-correcting code. The approach has been integrated in an H.264/MPEG-4 AVC
video coder and decoder. The PSNR gains obtained are discussed. 相似文献