全文获取类型
收费全文 | 483篇 |
免费 | 8篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 3篇 |
化学工业 | 93篇 |
金属工艺 | 4篇 |
机械仪表 | 8篇 |
建筑科学 | 52篇 |
矿业工程 | 3篇 |
能源动力 | 16篇 |
轻工业 | 74篇 |
水利工程 | 5篇 |
石油天然气 | 1篇 |
无线电 | 35篇 |
一般工业技术 | 65篇 |
冶金工业 | 45篇 |
原子能技术 | 3篇 |
自动化技术 | 85篇 |
出版年
2023年 | 5篇 |
2022年 | 3篇 |
2021年 | 11篇 |
2020年 | 5篇 |
2019年 | 4篇 |
2018年 | 14篇 |
2017年 | 7篇 |
2016年 | 6篇 |
2015年 | 9篇 |
2014年 | 13篇 |
2013年 | 25篇 |
2012年 | 23篇 |
2011年 | 17篇 |
2010年 | 20篇 |
2009年 | 20篇 |
2008年 | 22篇 |
2007年 | 24篇 |
2006年 | 29篇 |
2005年 | 16篇 |
2004年 | 19篇 |
2003年 | 14篇 |
2002年 | 15篇 |
2001年 | 8篇 |
2000年 | 9篇 |
1999年 | 9篇 |
1998年 | 17篇 |
1997年 | 8篇 |
1996年 | 5篇 |
1995年 | 7篇 |
1994年 | 12篇 |
1993年 | 8篇 |
1992年 | 10篇 |
1991年 | 7篇 |
1990年 | 5篇 |
1989年 | 12篇 |
1988年 | 5篇 |
1987年 | 2篇 |
1986年 | 3篇 |
1985年 | 4篇 |
1984年 | 4篇 |
1983年 | 4篇 |
1981年 | 2篇 |
1979年 | 5篇 |
1976年 | 8篇 |
1975年 | 3篇 |
1974年 | 3篇 |
1971年 | 2篇 |
1967年 | 2篇 |
1957年 | 1篇 |
1955年 | 1篇 |
排序方式: 共有492条查询结果,搜索用时 15 毫秒
81.
Kools SA Berg MP Boivin ME Kuenen FJ van der Wurff AW van Gestel CA van Straalen NM 《The Science of the total environment》2008,406(3):462-468
This study tested the hypothesis that soils with a deprived biodiversity due to metal pollution are less stable than non-polluted soils, containing a more diverse community. For this, soils were sampled from specific grasslands in the Netherlands that contain elevated heavy metal concentrations (Cu, Pb and Zn). Soils that showed the largest differences in metal concentrations were incubated in the laboratory using Terrestrial Model Ecosystems (TMEs). This approach enabled simultaneous measurement of structural (bacteria, nematodes, enchytraeids, earthworms) and functional parameters (nitrogen leaching, feeding activity, CO2 production, plant growth). The highest polluted soils showed a lower bacterial growth, and decreased enchytraeid and nematode biomass and diversity, hence a deprived community. More nitrate leached from high polluted soils, while all other functional endpoints did not differ. Additional stress application of zinc and heat was used to test the stability. Zinc treatment caused effects only in the higher polluted soils, observed at several moments in time for enchytraeids, CO2 fluxes and plant growth. Heat stress caused a large reduction in enchytraeid and earthworm biomass. Ammonium leaching was decreased by heat treatments in the most polluted soils, while CO2 was increased by heat in less polluted soils. Most effects were seen in the most polluted systems and it was concluded that they seem less stable. 相似文献
82.
Diffusion-weighted magnetic resonance imaging MRI) and especially diffusion tensor imaging (DTI) have proven to be useful for the characterization of the microstructure of brain white matter structures in vivo. However, DTI suffers from a number of limitations in characterizing more complex situations. The most notable problem occurs when multiple fibre bundles are present within a voxel. In this paper, we have expanded the existing Q-ball imaging method to a Bayesian framework in order to fully characterize the uncertainty around the fibre directions, given the quality of the data. We have done this by using a recently proposed spherical harmonics decomposition of the diffusion-weighted signal and the resulting Q-ball orientation distribution function. Moreover, we have incorporated a model selection procedure which determines the appropriate smoothness of the orientation distribution function from the data. We show by simulation that our framework can indeed characterize the posterior probability of the fibre directions in cases with multiple fibre populations per voxel and have provided examples of the algorithm's performance on real data where this situation is known to occur. 相似文献
83.
Merel Stiekema Frans C. S. Ramaekers Dimitrios Kapsokalyvas Marc A. M. J. van Zandvoort Rogier J. A. Veltrop Jos L. V. Broers 《International journal of molecular sciences》2021,22(19)
A- and B-type lamins are type V intermediate filament proteins. Mutations in the genes encoding these lamins cause rare diseases, collectively called laminopathies. A fraction of the cells obtained from laminopathy patients show aberrations in the localization of each lamin subtype, which may represent only the minority of the lamina disorganization. To get a better insight into more delicate and more abundant lamina abnormalities, the lamin network can be studied using super-resolution microscopy. We compared confocal scanning laser microscopy and stimulated emission depletion (STED) microscopy in combination with different fluorescence labeling approaches for the study of the lamin network. We demonstrate the suitability of an immunofluorescence staining approach when using STED microscopy, by determining the lamin layer thickness and the degree of lamin A and B1 colocalization as detected in fixed fibroblasts (co-)stained with lamin antibodies or (co-)transfected with EGFP/YFP lamin constructs. This revealed that immunofluorescence staining of cells does not lead to consequent changes in the detected lamin layer thickness, nor does it influence the degree of colocalization of lamin A and B1, when compared to the transfection approach. Studying laminopathy patient dermal fibroblasts (LMNA c.1130G>T (p.(Arg377Leu)) variant) confirmed the suitability of immunofluorescence protocols in STED microscopy, which circumvents the need for less convenient transfection steps. Furthermore, we found a significant decrease in lamin A/C and B1 colocalization in these patient fibroblasts, compared to normal human dermal fibroblasts. We conclude that super-resolution light microscopy combined with immunofluorescence protocols provides a potential tool to detect structural lamina differences between normal and laminopathy patient fibroblasts. 相似文献
84.
Ren L van Winsen Len J
A Lipman Steef Biesterveld Bert A
P Urlings Jos M
A Snijders Frans van Knapen 《Journal of the science of food and agriculture》2001,81(3):342-346
To protect consumers from Salmonella infection acquired through the consumption of pork meat, it is necessary to eradicate Salmonella from pork. In order to achieve this, the whole pork production chain should be free from Salmonella, including the pigs at the farm. In epidemiological studies it was concluded that the use of fermented feed plays a significant role in the reduction of Salmonella prevalence in pig farms. However, the mechanism of Salmonella reduction in fermented feed is not known. A controlled feed fermentation was performed using a pure culture of Lactobacillus plantarum. pH reduction, organic acid profiles and bacterial counts were determined. In L plantarum‐fermented feed, lactic acid and acetic acid were produced and the pH dropped to a value below 4.0. Antimicrobial products (bacteriocins) could not be detected. The results showed that the produced lactic and acetic acid and the pH in the feed are responsible for Salmonella reduction in fermented feed. L plantarum did not show any other antimicrobial effect on Salmonella. © 2000 Society of Chemical Industry 相似文献
85.
86.
Dirk Louwers Bert J. Kip Edo Peters Frans Souren Simme Douwe P. Flapper 《Computers & Industrial Engineering》1999,36(4):855
Re-using the huge quantities of carpet waste that are yearly generated has become a must. A facility location–allocation model for the collection, preprocessing and redistribution of carpet waste is presented. This model differs from other mathematical models for supporting the design of the logistic structure of reuse networks among others in a completely free choice of the locations for preprocessing and in explicitly taking into account depreciation costs. Two applications of the model, one in Europe and one in the United States of America, are described. 相似文献
87.
Hannele Holttinen Peter Meibom Antje Orths Bernhard Lange Mark O'Malley John Olav Tande Ana Estanqueiro Emilio Gomez Lennart Söder Goran Strbac J Charles Smith Frans van Hulle 《风能》2011,14(2):179-192
There are dozens of studies made and ongoing related to wind integration. However, the results are not easy to compare. IEA WIND R&D Task 25 on ‘Design and Operation of Power Systems with Large Amounts of Wind Power’ collects and shares information on wind generation impacts on power systems, with analyses and guidelines on methodologies. In the state‐of‐the‐art report (October, 2007), and the final report of the 3 years period (July, 2009) the most relevant wind power grid integration studies have been analysed especially regarding methodologies and input data. Several issues that impact on the amount of wind power that can be integrated have been identified. Large balancing areas and aggregation benefits of wide areas help in reducing the variability and forecast errors of wind power as well as help in pooling more cost effective balancing resources. System operation and functioning electricity markets at less than day‐ahead time scales help reduce forecast errors of wind power. Transmission is the key to aggregation benefits, electricity markets and larger balancing areas. Best practices in wind integration studies are described. There is also benefit when adding wind power to power systems: it reduces the total operating costs and emissions as wind replaces fossil fuels and this should be highlighted more in future studies. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
88.
Frans Vainio Michael Maier Esa Alhoniemi Mika Johnsson Olli S. Nevalainen 《国际生产研究杂志》2013,51(8):2201-2218
Several production planning tasks in the printed circuit board (PCB) assembly industry involve the estimation of the component placement times for different PCB types and placement machines. This kind of task may be, for example, the scheduling of jobs or line balancing for single or multiple jobs. The simplest approach to time estimation is to let the production time be a linear function of the number of components to be placed. To achieve more accurate results, the model should include more parameters (e.g. the number of different component types, the number of different component shapes, the dimensions of the PCBs, etc.). In this study we train multilayer neural networks to approximate the assembly times of two different types of assembly machines based on several parameter combinations. It turns out that conventional learning methods are prone to overfitting when the number of hidden units of the network is large in relation to the number of training cases. To avoid this and complicated training and testing, we use Bayesian regularisation to achieve efficient learning and good accuracy automatically. 相似文献
89.
Information about sampling rates and equilibration times of passive samplers is essential in their calibration in field monitoring studies as well as sorption studies. The kinetics of a sampler depends on the distribution coefficient between the sampler material and aqueous phase and the exchange rates of chemicals between these phases. In this study, the elimination kinetics of four poly(dimethylsiloxane) (PDMS) passive samplers with different surface-volume ratios are compared. The samplers were loaded with polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs) that cover a broad range of hydrophobicities. The surface-volume ratios of the samplers could largely explain the observed kinetics. Furthermore, a simple diffusion-based model illustrates that the exchange of chemicals was limited by diffusion through the aqueous diffusion layer surrounding the sampler. On the basis of this simple diffusion model, equilibration times are predicted for organic chemicals that vary in hydrophobicity and samplers with different dimensions and polymeric phases. This information is of importance in the selection of a passive sampler for a specific purpose. 相似文献
90.
Allesø M Velaga S Alhalaweh A Cornett C Rasmussen MA van den Berg F de Diego HL Rantanen J 《Analytical chemistry》2008,80(20):7755-7764
Near-infrared (NIR) spectroscopy is a well-established technique for solid-state analysis, providing fast, noninvasive measurements. The use of NIR spectroscopy for polymorph screening and the associated advantages have recently been demonstrated. The objective of this work was to evaluate the analytical potential of NIR spectroscopy for cocrystal screening using Raman spectroscopy as a comparative method. Indomethacin was used as the parent molecule, while saccharin and l-aspartic acid were chosen as guest molecules. Molar ratios of 1:1 for each system were subjected to two types of preparative methods. In the case of saccharin, liquid-assisted cogrinding as well as cocrystallization from solution resulted in a stable 1:1 cocrystalline phase termed IND-SAC cocrystal. For l-aspartic acid, the solution-based method resulted in a polymorphic transition of indomethacin into the metastable alpha form retained in a physical mixture with the guest molecule, while liquid-assisted cogrinding did not induce any changes in the crystal lattice. The good chemical peak selectivity of Raman spectroscopy allowed a straightforward interpretation of sample data by analyzing peak positions and comparing to those of pure references. In addition, Raman spectroscopy provided additional information on the crystal structure of the IND-SAC cocrystal. The broad spectral line shapes of NIR spectra make visual interpretation of the spectra difficult, and consequently, multivariate modeling by principal component analysis (PCA) was applied. Successful use of NIR/PCA was possible only through the inclusion of a set of reference mixtures of parent and guest molecules representing possible solid-state outcomes from the cocrystal screening. The practical hurdle related to the need for reference mixtures seems to restrict the applicability of NIR spectroscopy in cocrystal screening. 相似文献