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341.
Namsin Park Takeyuki Shiraishi Kazuyoshi Kamisugi Yoshitaka Hara Keita Iizuka Takashi Kado Shuzi Hayase 《Journal of Applied Electrochemistry》2008,38(3):371-375
A direct ethanol fuel cell (DEFC), which is less prone to ethanol crossover, is reported. The cell consists of PtRu/C catalyst as the anode, Nafion® 117 membrane, and Ni–Co–Fe (NCF) composite catalyst as the cathode. The NCF catalyst was synthesized by mixing Ni, Co, and Fe complexes into a polymer matrix (melamine-formaldehyde resins), followed by heating the mixture at 800 °C under inert atmosphere. TEM and EDX experiments suggest that the NCF catalyst has alloy structures of Ni, Co and Fe. The catalytic activity of the NCF catalyst for the oxygen reduction reaction (ORR) was compared with that of commercially available Pt/C (CAP) catalyst at different ethanol concentrations. The decrease in open circuit voltage (Voc) of the DEFC equipped with the NCF catalysts was less than that of CAP catalyst at higher ethanol concentrations. The NCF catalyst was less prone to ethanol oxidation at cathode even when ethanol crossover occurred through the Nafion®117 film, which prevents voltage drop at the cathode. However, the CAP catalyst did oxidize ethanol at the cathode and caused a decrease in voltage at higher ethanol concentrations. 相似文献
342.
Placid Rodriguez 《Metallurgical and Materials Transactions A》2004,35(9):2697-2705
A critical review of available results on the dependence of grain size on the activation parameters for deformation, specifically,
the activation volume, V*, and the thermal component of flow stress, σ*, has been carried out with a view to verifying the Armstrong prediction that identifies the Hall-Petch (H-P) intercept with
the easy slip system and the H-P slope with the most difficult system in polycrystals. The influence of slip system choice
is demonstrated using results on Cd and Zr. The Armstrong prediction is valid for basal slip hcp metals, such as Cd and Zn,
with V* and σ* determined by the difficult pyramidal slip. For the prism slip metals such as Zr and Ti, V* and σ* are controlled by interstitial solutes and are independent of grain size. The results on Zr are used to highlight the influence
of dynamic strain aging on the H-P parameters. In bcc metals, in which the Peierls-Nabarro barrier is the rate-controlling
obstacle, V* and σ* are again independent of grain size. For fcc metals, correlation of the H-P slope with the cross-slip stress, predicted
by the Armstrong model, has been demonstrated for a few cases. The variation of V* with grain size in Ni as reported by Narutani and Takamura (Acta Metall. Mater., 1991, vol. 227, pp. 2037–49) is newly interpreted in terms of the Armstrong model that associates the H-P intercept in fcc
metals with dislocation intersections and the H-P slope with cross-slip, and provides realistic results for the activation
volumes for the two processes.
This article is based on a presentation given in the symposium “Dynamic Deformation: Constitutive Modeling, Grain Size, and
Other Effects: In Honor of Prof. Ronald W. Armstrong,” March 2–6, 2003, at the 2003 TMS/ASM Annual Meeting, San Diego, California,
under the auspices of the TMS/ASM Joint Mechanical Behavior of Materials Committee. 相似文献
343.
Instrumental characterization of clay by XRF,XRD and FTIR 总被引:2,自引:0,他引:2
Instrumental characterizations of the clay were performed by different techniques such as XRF, XRD and FTIR. XRF shows the
chemical compositions of the clay where Al-oxide and silica oxide are present in major quantity whereas XRD confirms the presence
of these minerals in clay. FTIR studies show the presence of quartz, alumina, haematite and different mineral matters. 相似文献
344.
Thin layers of silver and titanium were deposited onto commercial Ti–48Al particles by magnetron sputtering prior to their consolidation by hot isostatic pressing and subsequent heat treatment.
Based on picnometry and electron probe microanalysis results, average values of 1.5 and 2.5 at.%, respectively, were obtained
for the silver and titanium contents in the coated particles. The surface modified Ti–48Al particles exhibited improved sintering ability than the unmodified ones. The consolidated samples have duplex microstructures
formed by γ-TiAl and γ-TiAl + α2-Ti3Al grains. Ag-rich nanoprecipitates were detected in the microstructure of the compacted Ti-48Al + Ag sample. The coatings are no longer visible at the grains boundaries after a subsequent homogenization heat treatment
at 1200°C. The highest values of hardness and Young’s modulus were obtained for the Ti–48Al + Ag sample, associated with a higher density and a lower percentage of pores. 相似文献
345.
Moshe Dayan 《Journal of Superconductivity and Novel Magnetism》2007,20(3):239-247
Here I establish the field perturbation theory of pseudogaps in HTSC. The proposed ground state suggests an internal particle-hole
field, which is normal to nesting surfaces, and having twice the Fermi wave number. It is proved that the system violates
momentum conservation by the wave vector of this internal field. This violation applies to the quasi-particle propagators,
as well as to the interactions. Interaction vertices via the Pauli matrix-τ1 are established. This, in turn, establishes the validity of the pseudogap Hartree self-energy. 相似文献
346.
The reaction between MgO and graphite powders under flowing argon atmosphere was studied using a dynamic thermogravimetric
method. In the temperature range 293 to 1973 K, the effects of compacting pressure, magnesia/carbon ratio, heating rate, Ar
carrier-gas flow rate, and CO-partial pressure were investigated. An experimentally determined reaction mechanism was proposed
and discussed. The reduction process could be divided into two stages. The first stage includes the direct reaction between
MgO and graphite particles and partial gas-solid reaction at relatively low temperature (below 1750 K). The overall reaction
rate depends on the solid phase-boundary reaction between magnesia and carbon particles. The second stage is the gas-solid
reaction between CO and MgO, which determines the overall reaction rate. The apparent activation energies of the two stages
were estimated to be 208.29 and 374.13 kJ/mol, respectively. 相似文献
347.
The paper firstly defined the remote sensing information quantification, analyzed the necessity of developing remote sensing quantification, figured out the application guidelines requirement, and pointed out the importance of quantification research. Then taking the remote sensing application research of CBERS-02 data quantification as the example, the paper described the whole quantification system of “remotely sensed digital signal-radiation information-field parameter inversion”. Finally the paper gave the prospect for the development trend of the quantitative remote sensing. 相似文献
348.
349.
Jan Paca Eva Klapkova Martin Halecky Kim Jones Carlos Riccardo Soccol 《Clean Technologies and Environmental Policy》2007,9(1):69-74
The removal of a mixture of painting solvents from waste air using a biofiltration process was evaluated in this project.
The pollutants removed included hydrophobic (aromatic hydrocarbons) and hydrophilic (water soluble ketones and esters) compounds.
A trickle bed reactor with a defined immobilized mixed culture on polyethylene Pall rings was utilized in this biodegradation
study. The removal efficiencies (RE) of the individual groups of pollutants during loading experiments were determined. An
increase of the aromatic hydrocarbons loading resulted in a drop of their REAROM with no effect on the RE value of ketones. The overloading of ketones caused a rapid drop in REAROM and a small drop in REKET. To achieve a restoration of the biocatalyst degradation properties after the increase in loading, an addition of phosphate
to the aqueous medium was implemented which successfully restored the removal efficiency. 相似文献
350.
Twenty-five years of natural coordinates 总被引:3,自引:0,他引:3
Javier García de Jalón 《Multibody System Dynamics》2007,18(1):15-33
In the early eighties, the author and co-workers created and further developed the natural coordinates to describe the motion
of 2-D and 3-D multibody systems. Natural coordinates do not need angles or angular parameters to define orientation, leading
to constant inertia matrices and to the simplest form of the constraint equations. Natural coordinates are composed by the
Cartesian coordinates of some points and the Cartesian components of some unit vectors distributed on the different bodies
of the system. The points and vectors can be located in the joints, being shared by contiguous bodies, decreasing or even
eliminating the need to set joint constraints and reducing the total number of variables. However, other authors prefer not
to share variables in order to get even simpler equations and to keep a bigger decoupling of equations, which is preferable
in some cases.
In this paper the history of natural coordinates is reviewed, as well as the main contributions coming from other research
groups. In the second part of the paper some application areas in which natural coordinates can be particularly advantageous
are examined.
Commemorative Contribution. 相似文献