全文获取类型
收费全文 | 684篇 |
免费 | 27篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 8篇 |
化学工业 | 252篇 |
金属工艺 | 27篇 |
机械仪表 | 18篇 |
建筑科学 | 37篇 |
矿业工程 | 5篇 |
能源动力 | 19篇 |
轻工业 | 54篇 |
水利工程 | 8篇 |
石油天然气 | 2篇 |
无线电 | 29篇 |
一般工业技术 | 114篇 |
冶金工业 | 42篇 |
原子能技术 | 7篇 |
自动化技术 | 90篇 |
出版年
2022年 | 24篇 |
2021年 | 32篇 |
2020年 | 9篇 |
2019年 | 5篇 |
2018年 | 19篇 |
2017年 | 23篇 |
2016年 | 24篇 |
2015年 | 13篇 |
2014年 | 29篇 |
2013年 | 57篇 |
2012年 | 25篇 |
2011年 | 43篇 |
2010年 | 19篇 |
2009年 | 47篇 |
2008年 | 26篇 |
2007年 | 27篇 |
2006年 | 18篇 |
2005年 | 20篇 |
2004年 | 16篇 |
2003年 | 20篇 |
2002年 | 12篇 |
2001年 | 15篇 |
2000年 | 13篇 |
1999年 | 3篇 |
1998年 | 3篇 |
1997年 | 5篇 |
1996年 | 8篇 |
1995年 | 5篇 |
1994年 | 9篇 |
1993年 | 4篇 |
1992年 | 7篇 |
1990年 | 5篇 |
1989年 | 6篇 |
1988年 | 8篇 |
1987年 | 10篇 |
1986年 | 8篇 |
1985年 | 10篇 |
1984年 | 11篇 |
1983年 | 11篇 |
1982年 | 9篇 |
1981年 | 9篇 |
1980年 | 9篇 |
1979年 | 6篇 |
1977年 | 3篇 |
1976年 | 7篇 |
1975年 | 2篇 |
1974年 | 4篇 |
1973年 | 3篇 |
1970年 | 2篇 |
1956年 | 2篇 |
排序方式: 共有712条查询结果,搜索用时 32 毫秒
41.
Absorption and photoreflectance spectroscopy of zinc phthalocyanine (ZnPc) thin films grown by thermal evaporation 总被引:1,自引:0,他引:1
Optical properties of the as-deposited and annealed ZnPc layers have been investigated using absorption, reflectance and modulated photoreflectance methods. The absorption coefficient of ZnPc layers was directly determined from the transmission and reflection spectra. The absorption spectra were analyzed in terms of the mixed Lorentz–Lorenz model. We found that annealing thin layers at 580 K caused a structural transformation, which results in the decrease of the absorption coefficient and the shifting of all peak position to lower energies except for the peak of the N-band. Photoreflectance spectroscopy confirmed that there exist three transitions in the Q-band region of the studied material. Complex refractive index and dielectric constants of the ZnPc layer were directly found from the spectral data. 相似文献
42.
A laboratory scale submerged filter filled with crushed marble was used for the nitrification process investigation. The results obtained showed that the alkaline reactor filling material react with the hydrogen ions released during the process course which enables reactor exploitation without any pH value or alkalinity control. 相似文献
43.
Zbigniew K. Walczak 《应用聚合物科学杂志》1973,17(1):169-176
The flow pattern of molten polymer through capillaries was studied by using a tracing method. An incompatible polymer was added to polypropylene as a tracer, and the influence of shear in a capillary rheometer on the tracer particle size as well as on the distribution of the particles in the extrudate in relation to flow was studied. It was found that the particle size varied inversely with shear rate of extrusion, capillary aspect ratio, polymer viscosity, and extrusion temperature. The flow was found to be of the telescopic type, and the tracer particle size was independent of position along the radius of the cylindrical extrudate. It is assumed that the supermolecular structure of a polymer melt is of the cluster type suggested by Busse, and it is postulated that spherical clusters of molecules in the melt are modified by shear analogously to the spherical particles of the incompatible tracer polymer. The large spectrum of melt properties obtainable, by various shearing treatments, from a polymer of constant molecular structure suggests that a wide range of supermolecular structures must be possible in the polymer melt. 相似文献
44.
45.
EPR studies using naturally abundant and 95Mo-enriched molybdenum have shown that reduced MoO
x
/SiO2catalysts with different dispersion of molybdenum provide a unique opportunity for molecular-level investigations of surface phenomena involved in the bonding to and activation of small molecules by oxide surfaces. Different types of electron transfer (ET) processes accompanying the activation of O2and N2O as well as the reactivity of O-and CH2OH transients with coadsorbed CH3OH and O2, respectively, have been identified. They include nondissociative and dissociative ET, surface intramolecular ET, and electroprotic transformation (ET coupled with proton transfer). In the case of methanol dehydrogenation it was found that if the reaction occurs on the MoO
x
cluster centers, ET exhibits a complementary character, in contrast to isolated Mo centers where noncomplementary ET accompanied by migration of the hydroxymethyl intermediate is observed. 相似文献
46.
Model-Supported Impact Assessment for the Water Sector in Central Germany Under Climate Change—A Case Study 总被引:1,自引:0,他引:1
Fred Fokko Hattermann Mathias Weiland Shaochun Huang Valentina Krysanova Zbigniew W. Kundzewicz 《Water Resources Management》2011,25(13):3113-3134
Climate change challenges water managers and researchers to find sustainable management solutions, in order to avoid undesirable
impacts on water resources, environment and water-dependent sectors. Needed are projections into the future for the main driving
forces, the resulting pressures on water resources, and quantification of the impacts. Modeling studies can play an important
role in investigating, quantifying, and communicating possible impacts of climate change, with account of uncertainty of the
results. However, climate change related impacts and a need for adaptation still play a minor role in current river basin
management plans that have to comply e.g. with the EU Water Framework Directive (WFD). One important reason is that climate
impact assessment is generally done in research institutes, while management plans are designed by practitioners working in
national and regional environmental agencies and water supply companies. Knowledge transfer from science to practice and visa
versa is often missing. In the present study, we propose a methodology and a case study for model-supported decision making
in the water sector applicable to a participatory water resources planning process. The methodology is applied in a case study
investigating climate change impacts on water resources. The case study area is the German State of Saxony-Anhalt, where the
task was to develop a climate change impact assessment including possible adaptation measures as basis for a federal adaptation
directive. 相似文献
47.
G Galazka LJ Windsor H Birkedal-Hansen JA Engler 《Canadian Metallurgical Quarterly》1999,38(4):1316-1322
Human stromelysin-1 (SL-1) is a member of the stromelysin subfamily of matrix metalloproteinases (MMPs). The MMPs play a major role in the degradation of the extracellular matrix (ECM) during normal and pathological conditions. SL-1 like the other MMPs can be activated in vitro by the stepwise removal of the propeptide that contains a single unpaired cysteine which coordinates the active site zinc. Other residues in the propeptide also play a role in maintaining the latency of the enzymes. Deletion mutants and single-site amino acid replacements within the propeptide of a carboxyl-terminally truncated stromelysin-1 (mini-SL-1) were constructed and expressed in Escherichia coli to further examine what amino acids within the propeptide of SL-1 are important for maintaining latency. While the natural enzyme displayed some limited tendency to spontaneously (autolytically) convert to lower Mr in a stepwise manner and finally to the fully processed form, all of the truncation mutants of more than 19 amino acids generated in E. coli showed greatly accelerated self-cleavage indicative of diminished stability and/or resistance to proteolysis of the residual propeptide. Mutant Delta63 as well as other mutants in which most of the propeptide had been deleted no longer responded to exposure to the organomercurial APMA by accelerated autolytic processing. Rather, APMA inhibited the autolytic processing in these mutants, further confirming the complexity of the action of this organomercurial in the activation of pro-MMPs. 相似文献
48.
The thermal degradation of acrylic pressure-sensitive adhesives at 250 °C was investigated using pyrolysis-gas chromatography. Knowledge of the types and amounts of pyrolysis products will provide important information on the thermal degradation of acrylic adhesives and the mechanisms involved. Unsaturated monomers including butyl acrylate and butyl methacrylate were formed during thermal degradation of butyl acrylate–acrylic acid copolymers. As a result of side chain reactions in the thermal destruction of the butyl acrylate–acrylic acid-based self-adhesives, a remarkable amount of butyl alcohol was produced. The unsaturated monomers formed as a result of thermal degradation could potentially be used in a new polymerization process. 相似文献
49.
The design of thin structures must take into account the overall instability and the instability of component plates in the form of local buckling. This investigation is concerned with the interactive buckling of thin-walled structures with central intermediate stiffeners under axial compression and/or a constant bending moment. The structures are assumed to be simply supported at the ends. The lower bound estimation of load-carrying capacity on the basis of the post-buckling behaviour of thin-walled structures with imperfections is studied when the distortional deformations are taken into account. The asymptotic expansion established by Byskov and Hutchinson (AIAA J. 15 (1977) 941) is employed in the numerical calculations performed using the transition matrix method. The present paper is a continuation of previous work by the authors (Int. J. Solids Struct. 32 (1995) 1501; 33 (1996) 315; 37 (2000) 3323), where the interactive buckling of thin-walled beam-columns with central intermediate stiffeners in the first- and the second-order approximation were considered. In the solution obtained, the transformation of buckling modes with an increase in the load up to the ultimate load, the effect of cross-sectional distortions and the shear lag phenomenon are included. The results obtained are compared with data reported by other authors. 相似文献
50.
The system concepts of importance to hydrological sciences are reviewed. The epochs of the development of systems sciences are discussed and their links with hydrological and water resources research are illustrated. Potentials and limitations of the system approach are discussed and the perspectives of further applications are sketched. 相似文献