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991.
Christopher McConville Gavin P. Andrews Thomas P. Laverty A. David Woolfson R. Karl Malcolm 《应用聚合物科学杂志》2010,116(4):2320-2327
Silicone elastomer systems have been shown to offer potential for the fabrication of medical devices and sustained release drug delivery devices comprising low molecular weight drugs and protein therapeutics. For drug delivery systems in particular, there is often no clear rationale for selection of the silicone elastomer grade, particularly in respect of optimizing the manufacturing conditions to ensure thermal stability of the active agent and short cycle times. In this study, the cure characteristics of a range of addition‐cure and condensation‐cure, low‐consistency, implant‐grade silicone elastomers, either as supplied or loaded with the model protein bovine serum albumin (BSA) and the model hydrophilic excipient glycine, were investigated using oscillatory rheology with a view to better understanding the isothermal cure characteristics. The results demonstrate the influence of elastomer type, cure temperature, protein loading, and glycine loading on isothermal cure properties. By measuring the cure time required to achieve tan delta values representative of early and late‐stage cure conditions, a ratio t1/t2 was defined that allowed the cure characteristics of the various systems to be compared. Sustained in vitro release of BSA from glycine‐loaded silicone elastomer covered rod devices was also demonstrated over 14 days. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 相似文献
992.
A highly sensitive (pM), efficient (t < 20 min) detection assay was developed by designing surfaces with grafted antibodies. Through this approach, a short half-life antigen, glucagon, was rapidly detected in a biologically complex plasma/blood environment. Tailoring of graft composition eliminates the need for time-consuming blocking steps, significantly reducing antigen-antibody incubation times, while maintaining antibody specificity and activity toward target antigen. Grafted antibodies were bound through solvated, mobile polymer chains, thereby circumventing problems associated with antibody accessibility, analyte diffusion, and steric limitations. The efficiency of this assay is provided through grafting synthesized, acrylated antibodies in the presence of PEG monoacrylate. This procedure eliminates the need for blocking steps, due to a decrease in nonspecific protein interactions. These polymerizable antibodies were tethered with a range of densities while retaining biological activity. Moreover, biological activity of acrylated antibodies was compared to that of unmodified antibodies and remained comparable. The acrylated antibodies were grafted from substrate surfaces using controlled radical photopolymerization, maintaining the advantages of classical antibody immobilization techniques while providing improved detection. Through integrating this antibody conjugation chemistry and immunoassay approach with photolithographic techniques, construction of spatial patterns on a microfluidic device was demonstrated for efficient, parallel screening of multiple antigens. 相似文献
993.
Dable BK Love BA Battaglia TM Booksh KS Lilley MD Marquardt BJ 《Applied spectroscopy》2006,60(7):773-780
This article will demonstrate that Raman spectroscopy can be a useful tool for monitoring the chemical composition of hydrothermal vent fluids in the deep ocean. Hydrothermal vent systems are difficult to study because they are commonly found at depths greater than 1000 m under high pressure (200-300 bar) and venting fluid temperatures are up to 400 degrees C. Our goal in this study was to investigate the use of Raman spectroscopy to characterize and quantitate three Raman-active salts that are among the many chemical building blocks of deep ocean vent chemistry. This paper presents initial sampling and calibration studies as part of a multiphase project to design, develop, and deploy a submersible deep sea Raman instrument for in situ analysis of hydrothermal vent systems. Raman spectra were collected from designed sets of seawater solutions of carbonate, sulfate, and nitrate under different physical conditions of temperature and pressure. The role of multivariate analysis techniques to preprocess the spectral signals and to develop optimal calibration models to accurately estimate the concentrations of a set of mixtures of simulated seawater are discussed. The effects that the high-pressure and high-temperature environment have upon the Raman spectra of the analytes were also systematically studied. Information gained from these lab experiments is being used to determine design criteria and performance attributes for a deployable deep sea Raman instrument to study hydrothermal vent systems in situ. 相似文献
994.
Kinetics and degradation products resulting from the application of UV and UV/H(2)O(2) to the US EPA Contaminant Candidate List pesticide diazinon were studied. Batch experiments were conducted with both monochromatic (low pressure [LP] UV 253.7 nm) and polychromatic (medium pressure [MP] UV 200-300 nm) UV sources alone or in the presence of up to 50 mg l(-1) H(2)O(2), in a quasi-collimated beam apparatus. Degradation of diazinon by both UV and UV/H(2)O(2) exhibited pseudo first order reaction kinetics, and quantum yield of 8.6 x 10(-2) and 5.8 x 10(-2) mol E(-1) for LP and MP lamps respectively. Photolysis studies under MP UV lamp showed 2-isopropyl-6-methyl-pyrimidin-4-ol (IMP) to be the main degradation product of diazinon at aqueous solution pH values of 4, 7 and 10. Trace levels up to 1.8 x 10(-3) microM of diazinon oxygen analogue diethyl 2-isopropyl-6-methylpyrimidin-4-yl phosphate (diazoxon) were detected only during the UV/H(2)O(2) reaction. Decay of both products was observed, as the UV/H(2)O(2) reaction prolonged, yet no mineralization was achieved over the UV fluence levels examined. Photolysis kinetics, quantum yield and UV/H(2)O(2) degradation of the reaction product IMP was determined using MP UV lamp at pH values of 4, 7 and 10. 相似文献
995.
Christensen KB 《Journal of applied measurement》2006,7(4):407-417
The item parameters of a polytomous Rasch model can be estimated using marginal and conditional approaches. This paper describes how this can be done in SAS (V8.2) for three item parameter estimation procedures: marginal maximum likelihood estimation, conditional maximum likelihood estimation, and pairwise conditional estimation. The use of the procedures for extensions of the Rasch model is also discussed. The accuracy of the methods are evaluated using a simulation study. 相似文献
996.
Am 5. September 2009 wäre Hellmut Homberg einhundert Jahre alt geworden. Dies ist Anlass, an sein vor allem den Brückenbau bereicherndes Wirken zu erinnern und ein, wenn auch nicht vollständiges, Werkverzeichnis zu erstellen. Das gilt sowohl für die unter seiner maßgebenden Mitwirkung entworfenen Brücken als auch für seine völlig neuartigen, die statischen Berechnungen in der Praxis erleichternden, streng theoretisch hergeleiteten und eine zutreffende Bemessung der Kreuzwerke und orthotropen Fahrbahnplatten ermöglichenden Tafel‐ und Tabellenwerke. Teil I schildert Homberg s beruflichen Weg und versucht, ein Porträt zu zeichnen; Teil II ist seinen theoretischen Untersuchungen gewidmet, und Teil III geht auf besondere Brücken ein, und. Harmony between science and art in bridge‐building: Hellmut Homberg (1909–90) – life and work (part I). Hellmut Homberg would have been 100 years old on 5 September 2009. This is an opportunity to look back on his work which so enriched the world of bridge‐building in particular, and also a chance to compile a catalogue of his work, albeit incomplete. This applies to the bridges in which he played an influential role in their design and also to his books of mathematical and design tables that enabled the accurate design of beam grids and orthotropic bridge decks. The tables with their rigorous theoretical background were at the time quite new and eased structural calculations in everyday practice. Part I describes Homberg's professional career and attempts to draw a portrait of the man; part II is devoted to his theoretical studies, and part III deals with particular bridges. 相似文献
997.
Stefan Valentin Hermann S. Lichte Holger Karl Guillaume Vivier Sébastien Simoens Josep Vidal Adrian Agustin 《Wireless Personal Communications》2009,48(1):49-68
In future wireless networks devices may cooperate to form logical links. Each of these links may consist of several independent
physical channels which are shared by the cooperating partners. Even without multiple antennas this cooperation provides diversity
in time and space. This so-called cooperation diversity increases the robustness of the link vs. fading and interference. After surveying approaches in cooperation diversity we
focus on optimizing its performance by combining several cooperation schemes and by integrating cooperation into space-time
coding. For multiple scenarios, we further discuss the factors and benefits introduced by user cooperation and how cooperation-aware
resource allocation can be employed to further increase the performance of cooperative networks. When it comes to implementation,
the question arises how cooperation can be integrated efficiently into existing wireless networks. A case study for 802.11-based
WLANs reveals the issues that need to be solved in order to deploy cooperative techniques. We provide an overview of the state
of the art in implementing cooperation approaches, analyze how appropriate these approaches solve the issues, and, where appropriate,
point out their deficiencies. We conclude with a road map for future research necessary to tackle these deficiencies for the
practical implementation of cooperation in next generation mesh, WLAN, WMAN, and cellular standards.
相似文献
Adrian AgustinEmail: |
998.
Staaf E Brehwens K Haghdoost S Pachnerová-Brabcová K Czub J Braziewicz J Nievaart S Wojcik A 《Radiation protection dosimetry》2012,151(3):570-579
Exposure of humans to mixed fields of high- and low-linear energy transfer (LET) radiation occurs in many situations-for example, in urban areas with high levels of indoor radon as well as background gamma radiation, during airplane flights or certain forms of radiation therapy. From the perspective of health risk associated with exposure to mixed fields, it is important to understand the interactions between different radiation types. In most cellular investigations on mixed beams, two types of irradiations have been applied sequentially. Simultaneous irradiation is the desirable scenario but requires a dedicated irradiation facility. The authors have constructed a facility where cells can be simultaneously exposed to (241)Am alpha particles and 190-kV X-rays at 37°C. This study presents the technical details and the dosimetry of the setup, as well as validates the performance of the setup for clonogenic survival in AA8 Chinese hamster ovary cells. No significant synergistic effect was observed. The relative biological effectiveness of the alpha particles was 2.56 for 37 % and 1.90 for 10 % clonogenic survival. 相似文献
999.
Alejandra?de la?VegaEmail author Jan?Sumfleth Hans?Wittich Karl?Schulte 《Journal of Materials Science》2012,47(6):2648-2657
In this study, the behaviour of carbon nanotube/epoxy and carbon black/epoxy composites under dynamic load is studied via
dynamic mechanical thermal analysis (DMTA) in combination with DC electrical resistivity measurements. DMTA measurements are
carried out at fixed temperature whilst the dynamic loading frequency is varied. With this procedure, a loading frequency-dependence
of the phase shift between DC electrical resistance and mechanical elongation (δ
R–ε) is observed, although the force and elongation of the sample are still in phase. Moreover, the magnitude of this phase shift,
as well as the amplitude of the DC electrical resistance change shows a clear dependence on the initial electrical conductivity
of the samples. In addition, temperature sweeps are carried out to investigate the temperature dependency of the piezoresistance
of the samples. An abrupt change in their sensitivity is observed as soon as the glass transition of the polymer is reached.
However, the trend of the resistance change beyond the glass transition is substantially different between the nanocomposites
containing carbon black and carbon nanotubes, revealing a strong influence of the network characteristics on the piezoresistive
behaviour of these novel materials. 相似文献