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91.
92.
CMOS artificial subretinal chip for natural light illumination 总被引:1,自引:0,他引:1
A novel CMOS oscillating pixel array for subretinal prosthesis used in natural light illumination is presented. Its prototype chips are fabricated in a standard 0.6 /spl mu/m CMOS technology. Experimental results show the device can deliver effective self-oscillation for subretinal electrical stimulation. 相似文献
93.
94.
Ultrahigh strength steels have been used increasingly in recent years for critical aircraft and aerospace structural applications.
In such applications, though materials performance is of prime consideration, cost and availability makes the low-alloy steels
an attractive option. This paper describes the development of an ultrahigh strength NiSiCrCoMo low-alloy steel, supported
by significant findings obtained from the basic studies that were aimed at understanding how solute additions influence fracture
resistance of iron, with and without the presence of carbon. The results of the basic studies, in combination with the work
of Garrison (1986) on a NiSiCr steel, have profitably been employed in the development of a NiSiCrCoMo low-alloy steel possessing
a strength-toughness combination quite comparable to the highly alloyed 250-grade maraging steel. Reproducibility of attractive
strength and toughness properties has been established in tonnage scale melts. This steel, in the softened condition, has
good formability and machinability. Weld parameters have also been established. The NiSiCrCoMo low-alloy steel thus meets
the requirements of performance and cost rendering it an attractive option for advanced structural applications. 相似文献
95.
M. Valsan D. Sundararaman K. Bhanu Sankara Rao S. L. Mannan 《Metallurgical and Materials Transactions A》1995,26(5):1207-1219
A comparative evaluation of the low-cycle fatigue (LCF) behavior of type 316LN base metal, 316 weld metal, and 316LN/316 weld
joints was carried out at 773 and 873 K. Total strain-controlled LCF tests were conducted at a constant strain rate of 3 ×
10−3 s−1 with strain amplitudes in the range ±0.20 to ±1.0 pct. Weld pads with single V and double V configuration were prepared by
the shielded metal-arc welding (SMAW) process using 316 electrodes for weld-metal and weld-joint specimens. Optical microscopy,
scanning electron microscopy (SEM), and transmission electron microscopy (TEM) of the untested and tested samples were carried
out to elucidate the deformation and the fracture behavior. The cyclic stress response of the base metal shows a very rapid
hardening to a maximum stress followed by a saturated stress response. Weld metal undergoes a relatively short initial hardening
followed by a gradual softening regime. Weld joints exhibit an initial hardening and a subsequent softening regime at all
strain amplitudes, except at low strain amplitudes where a saturation regime is noticed. The initial hardening observed in
base metal has been attributed to interaction between dislocations and solute atoms/complexes and cyclic saturation to saturation
in the number density of slip bands. From TEM, the cyclic softening in weld metal was ascribed to the annihilation of dislocations
during LCF. Type 316LN base metal exhibits better fatigue resistance than weld metal at 773 K, whereas the reverse holds true
at 873 K. The weld joint shows the lowest life at both temperatures. The better fatigue resistance of weld metal is related
to the brittle transformed delta ferrite structure and the high density of dislocations at the interface, which inhibits the
growth rate of cracks by deflecting the crack path. The lower fatigue endurance of the weld joint was ascribed to the shortening
of the crack initiation phase caused by surface intergranular crack initiation and to the poor crack propagation resistance
of the coarse-grained region in the heat-affected zone. 相似文献
96.
A compact T-shaped dielectric resonator antenna (DRA) with two equilateral-triangle cross sections is investigated in this letter. The DRA is vertically placed on a finite ground plane and excited by a coaxial probe to provide broadband and conical radiation patterns. In order to examine the proposed design, simulations and measurements were employed to investigate the proposed antenna, and a good agreement between them was obtained. The proposed design produces an impedance bandwidth of more than 60% from 1.6 to 3.1GHz, which effectively covers several promising application bands in contemporary wireless communication systems, such as digital communication systems (DCS: 1710-1880MHz), personal communication systems (PCS: 1850-1990MHz), universal mobile telecommunication systems (UMTS: 1920-2170MHz), wireless local area networks (WLANs: 2.4-2.485GHz). Additionally, stable conical patterns were also obtained within the interest frequency band. 相似文献
97.
1,3,5‐Triglyceratetriazine [first tier (G1)] and tri(1,3,5‐triglycerate) triazine [second tier (G2)] dendrimers were prepared with 1,3,5‐trichlorotriazine and sodium glycerate in a 1 : 3 mass ratio in an ethanolic medium.G1 and G2 were amorphous, white, solid substances. Their structures were elucidated with IR, 1H‐NMR, and 13C‐NMR, and their thermal stability was studied with thermogravimetric analysis. The activation energy was calculated with the Freeman–Carroll model. Densities, viscosities, and surface tensions for 0.01–0.08 mol/kg aqueous solutions increased at 0.01 mol/kg for sodium glycerate, 1,3,5‐trichlorotriazine, 1,3,5‐triazine triglycerate chloride, G1, and G2. These values were measured at 298.15 K. The apparent molal volume, reduced viscosity, and inherent viscosity were calculated from the densities and viscosities, respectively. The data were regressed for the limiting densities, limiting apparent molal volumes, intrinsic viscosities, limiting inherent viscosities, and limiting surface tensions for solute–solvent interactions. The positive limiting apparent molal volume values were noted in the order of G2 > 1,3,5‐triazine triglycerate chloride > G1 > 1,3,5‐trichlorotriazine > sodium glycerate, with weaker hydrophilic intermolecular interactions of G2. The higher intrinsic viscosity and limiting inherent viscosity values for G2 implied stronger G2–H2O hydrophilic interactions, and the higher limiting apparent molal volume of G2 indicated slightly higher dynamic conformational changes in comparison with G1, with stronger structural activities. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 相似文献
98.
Sodium‐ion conducting polymer electrolytes based on poly(vinyl alcohol) complexed with sodium bromide were prepared with a solution‐casting technique. The structure of these films was determined with X‐ray diffraction, and the complexation of the salt with the polymer was confirmed with Fourier transform infrared spectroscopy studies. Electrical conductivity was measured with an alternating‐current impedance analyzer in the frequency range of 100 Hz to 1 MHz and in the temperature range of 303–373 K. It was observed that the magnitude of conductivity increased with the increase in the salt concentration as well as the temperature. The nature of the charge transport in these polymer electrolyte films was determined with both Wagner's polarization technique and the Watanabe technique. The dominant conducting species were found to be ions, particularly anions. Optical absorption studies were performed in the wavelength range of 200–600 nm, and the absorption edge, direct band gap, and indirect band gap values were evaluated. Electrochemical cells were fabricated, and their discharge characteristics were studied. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 相似文献
99.
Sajan D. George Rajesh Komban K. G. K. Warrier P. Radhakrishnan V. P. N. Nampoori C. P. G. Vallabhan 《International Journal of Thermophysics》2007,28(1):123-132
The laser induced non-destructive photoacoustic technique has been employed to measure the thermal diffusivity of lanthanum
phosphate ceramics prepared by the sol–gel route. The thermal diffusivity value was evaluated by knowing the transition frequency
between the thermally thin to thermally thick region from the log–log plot of photoacoustic amplitude versus chopping frequency.
Analysis of the data was carried out on the basis of the one-dimensional model of Rosencwaig and Gersho. The present investigation
reveals that the sintering temperature has great influence on the propagation of heat carriers and hence on the thermal diffusivity
value. The results were interpreted in terms of variations in porosity with sintering temperature as well as with changes
in grain size. 相似文献
100.
Synthesis and characterization of acidic properties of Al-SBA-15 materials with varying Si/Al ratios
G. Muthu Kumaran Shelu Garg Kapil Soni Manoj Kumar J.K. Gupta L.D. Sharma K.S. Rama Rao G. Murali Dhar 《Microporous and mesoporous materials》2008,114(1-3):103-109
Al-SBA-15 of varying Si/Al ratios in the range 11.4–78.4 was synthesized using tri-block copolymer P123. The calcined materials were examined by XRD, pore size distribution, surface area, 27Al NMR spectroscopy. The acidity and acid strength distribution were studied using microcalorimetric adsorption of NH3. The acidic properties were also examined by cumene cracking reaction as a function of Si/Al ratios. Systematic variation of acidity and activity was observed as a function of Si/Al ratio. The initial heats of NH3 adsorption correlated well with activity indicate that acid sites with ΔH > 100 kJ/mole is responsible for cumene cracking activity. Linear correlations were obtained with total acidity and cumene cracking activities. The tetrahedral aluminum was found to be responsible for the observed acidities and catalytic activities. 相似文献