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61.
The paper proposes a new calibration method for parallel manipulators that allows efficient identification of the joint offsets using observations of the manipulator leg parallelism with respect to the base surface. The method employs a simple and low-cost measuring system, which evaluates deviation of the leg location during motions that are assumed to preserve the leg parallelism for the nominal values of the manipulator parameters. Using the measured deviations, the developed algorithm estimates the joint offsets that are treated as the most essential parameters to be identified. The validity of the proposed calibration method and efficiency of the developed numerical algorithms are confirmed by experimental results. The sensitivity of the measurement methods and the calibration accuracy are also studied. 相似文献
62.
We present a study of nickel-silicides ordered alloys by means of first-principles calculations. Emphasis was put on the phases (low and high temperatures) identified in the binary phase diagram, namely: Ni3Si-β1, -β2, and -β3, Ni31Si12-γ, Ni2Si-δ, -θ, Ni3Si2-?, NiSi-MnP and NiSi2-α. In addition, some common structures are computed for information: L12, D03 and D022. The simulations reproduce with a high accuracy lattice parameters and formation energies of main experimental structures, except for β2 and β3. Our results clarify the crystallographic nature of the γ structure, and the comparison of experimental Raman spectra and vibrational calculations will help experimentalists to identify without ambiguity NiSi3 structures. 相似文献
63.
Frédéric Golay Damien Lachouette Stéphane Bonelli Pierre Seppecher 《Computer Methods in Applied Mechanics and Engineering》2011,200(1-4):383-391
The aim of this study is to develop a numerical model for simulating surface erosion occurring at a fluid/soil interface subject to a flow process. Balance equations with jump relations are used. A penalization procedure including a fictitious domain method is used to compute the Stokes flow around obstacles, in order to avoid body-fitted unstructured meshes and instead use fast and efficient finite volume approximations on Cartesian meshes. The evolution of the water/soil interface is described by using a level set function. The ability of the model to predict the interfacial erosion of soils is confirmed by several numerical simulations. 相似文献
64.
Currently commercialised stand-alone street lighting systems based on the classical configuration coupling photovoltaic cells (PV) and battery cannot work all the year round in regions that are far from the equator. To improve the classical system, a hybrid system coupling a PV, a battery and a fuel cell is proposed. However, the sizing method of hybrid systems is a key issue in obtaining the cheapest system. To optimise the system, an original time-saving method is applied. Two optimization methods are used: first the genetic algorithms, then the simplex algorithms. A simulation model is used to evaluate the validity of the different hybrid configurations. After presenting the problem of stand-alone street lighting, the optimization methodology and the simulation model are detailed. Finally, an optimal configuration is obtained and shows that a 60 W street light would cost 7150€ with a lifetime of 25 years. The optimised parameters are also given and analysed. 相似文献
65.
The aim of this paper is to derive a double LDF non-isothermal model to describe mass transfer through a fixed bed of bi-disperse adsorbent pellets. Firstly, we perform an analysis concerning the different way the composition within the pellets can be described and the consequence on the model structure and compactness. Secondly, we present a bed model including a simplified intra-particle model that is based on a double LDF approximation. This bi-disperse pellet model reduces the number of variables and parameters that are needed. This simplified model is used to simulate breakthroughs of a methane/carbon dioxide mixture over a 5 A zeolite and of a 2,2-dimethylbutane/2-methylpentane mixture over a silicalite molecular sieve. It is also compared with a more detailed model based on Stefan-Maxwell theory that we have previously developed. 相似文献
66.
Gadolinium‐Doped Persistent Nanophosphors as Versatile Tool for Multimodal In Vivo Imaging 下载免费PDF全文
Thomas Maldiney Bich‐Thuy Doan Damien Alloyeau Michel Bessodes Daniel Scherman Cyrille Richard 《Advanced functional materials》2015,25(2):331-338
Recent breakthroughs in the rational development of multifunctional nanocarriers have highlightened the advantage of combining the complementary forces of several imaging modalities into one single nanotool fully dedicated to the biomedical field and diagnosis applications. A novel multimodal optical‐magnetic resonance imaging nanoprobe is introduced. Designed on the basis of a spinel zinc gallate structure doped with trivalent chromium and gadolinium, this nanocrystal bears the ability to serve as both a highly sensitive persistent luminescence nanoprobe for optical imaging, and a negative contrast agent for highly resolved magnetic resonance imaging (MRI). Additional proof is given that surface coverage can be modified in order to obtain stealth nanoparticles highly suitable for real‐time in vivo application in mice, showing delayed reticulo‐endothelial uptake and longer circulation time after systemic injection. 相似文献
67.
Laurène Legrand Sylvain Patinet Jean-Baptiste Leblond Joël Frelat Véronique Lazarus Damien Vandembroucq 《International Journal of Fracture》2011,170(1):67-82
Several groups have studied experimentally the deformation of the front of mode I cracks propagating quasistatically along
the interface between bonded plates. The theoretical interpretation of such experiments has always been based up to now on
a formula of Rice (ASME J Appl Mech 52:571–579, 1985); this formula provides the first-order variation of the local mode I stress intensity factor resulting from some small,
but otherwise arbitrary coplanar perturbation of the front of a semi-infinite crack in an infinite body. To be applicable
to bonded plates, this formula requires that the characteristic distance of variation of this perturbation in the direction
of the crack front be small compared to all other characteristic dimensions of the problem, and first of all the thickness
of the plates. This condition is unfortunately frequently violated in practice. The purpose of this paper is therefore to
provide a more exact formula for the variation of the local stress intensity factor, for the specific cracked geometry and
boundary conditions used in experiments; this should allow for more accurate theoretical interpretations. This is done in
two steps. The first one consists in adapting Rice’s (ASME J Appl Mech 52:571–579, 1985) treatment, applicable to the extreme case of plates of infinite thickness, to the other extreme one of plates of infinitesimal
thickness, using the standard Love-Kirchhoff plate theory. An interesting outcome of the analysis is that the distance from
the crack front to the boundary of the plate acts as a “cutoff length”, in the sense that when the distance between two points
on the crack front gets larger than it, the influence of the crack advance at the first point upon the stress intensity factor
at the second diminishes quickly; the plate thickness, however, plays no similar role. The second step consists in supplementing
the theoretical expressions applicable to extreme values of the plate thickness with finite element computations providing
results for intermediate values. These computations lead to the definition of a simple, approximate but accurate “interpolation
formula” for the variation of the local stress intensity factor, applicable to plates of arbitrary thickness. 相似文献
68.
Water reclamation plants frequently utilise reverse osmosis (RO), generating a concentrated reject stream as a by-product. The concentrate stream contains salts, and dissolved organic compounds, which are recalcitrant to biological treatment, and may have an environmental impact due to colour and embedded nitrogen. In this study, we characterise organic compounds in RO concentrates (ROC) and treated ROC (by coagulation, adsorption, and advanced oxidation) from two full-scale plants, assessing the diversity and treatability of colour and organic compounds containing nitrogen. One of the plants was from a coastal catchment, while the other was inland. Stirred cell membrane fractionation was applied to fractionate the treated ROC, and untreated ROC along with chemical analysis (DOC, DON, COD), colour, and fluorescence excitation-emission matrix (EEM) scans to characterise changes within each fraction. In both streams, the largest fraction contained <1 kDa molecules which were small humic substances, fulvic acids and soluble microbial products (SMPs), as indicated by EEM. Under optimal treatment conditions, alum preferentially removed >10 kDa molecules, with 17-34% of organic compounds as COD. Iron coagulation affected a wider size range, with better removal of organics (41-49% as COD) at the same molar dosage. As with iron, adsorption reduced organics of a broader size range, including organic nitrogen (26-47%). Advanced oxidation (UV/H2O2) was superior for complete decolourisation and provided superior organics removal (50-55% as COD). 相似文献
69.
Early trials and analysis of a new adhesion test are discussed. The test is designed for measuring the adhesion of paint to
deformable steel sheets as used in building, automotive, and other cladding applications, and does not require detailed knowledge
of the paint mechanical properties. A stiff overlay, such as an epoxy resin, is applied to the coating, and the steel substrate
is peeled away using a roll of well-defined radius to which the steel substrate is constrained. The propagation of a crack
within the paint or at some interface in the paint/metal system depends mostly on the mechanical properties and thickness
of the overlay and the radius of the constraining roll. The test is shown to discriminate better than existing practical adhesion
tests between paints of expected differing adhesion/cohesion, but also presents some inconsistencies that require further
work to resolve.
BHP Institute of Steel Processing and Products, Wollongong NSW 2522, Australia. 相似文献
70.
A new type of frequency-selective surface using aperture-coupled microstrip patches is described. The geometry uses two back-to-back arrays of microstrip antennas with coupling apertures in the common ground plane, and provides a narrow passband response that may be useful for radome and RCS reduction applications. Calculated results demonstrate the operation of the structure, and are verified with measurements using a waveguide simulator.<> 相似文献