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81.
Graft copolymerization of acrylonitrile (AN) and methyl methacrylate (MMA) onto polychloroprene (CR) was carried out using benzoyl peroxide as initiator. The effects of mole ratio of AN to MMA, reaction temperature, reaction time, solvent, and initiator concentration on the graft copolymerization were examined. It was found that the thermal stability and weatherability of the AN—CR—MMA graft copolymer (ACM) were considerably better than those of CR. 相似文献
82.
Ki Soo ParkMyung Hun Cho Sang Ho ParkKee Suk Nahm Yang Kook SunYun Sung Lee Masaki Yoshio 《Electrochimica acta》2002,47(18):2937-2942
Layered Li0.7[M1/6Mn5/6]O2 (M=Li, Ni) was synthesized using a sol-gel method. P2-Na0.7[M1/6Mn5/6]O2 precursor was first synthesized by a sol-gel method, and then O2-Li0.7[M1/6Mn5/6]O2 was prepared by an ion exchange of Li for Na in P2-Na0.7[M1/6Mn5/6]O2 precursor. From charge/discharge curves, it was seen that Li0.7[Li1/6Mn5/6]O2 has two plateaus similar to those observed from a spinel structure, but Li0.7[Ni1/6Mn5/6]O2 holds a single plateau as observed from a typical layered structure. It was considered that Li0.7[Li1/6Mn5/6]O2 undergoes a phase transformation from layered to spinel structure during the charge/discharge cycle, but Li0.7[Ni1/6Mn5/6]O2 maintains O2-layered structure after the cycles. Li0.7[Ni1/6Mn5/6]O2 was higher in discharge capacity and retention rate than Li0.7[Li1/6Mn5/6]O2. 相似文献
83.
Polymer gel electrolytes were prepared by thermal crosslinking reaction of a series of acrylic end‐capped poly(ethylene glycol) and poly(propylene glycol) [P(EG‐co‐PG)] having various geometries and molecular weights. Acrylic end‐capped prepolymers were prepared by the esterification of low molecular weight (Mn: 1900–5000) P(EG‐co‐PG) with acrylic acid. The linear increase in the ionic conductivity of polymer gel electrolyte films was observed with increasing temperature. The increase in the conductivity was also monitored by increasing the molecular weight of precursor polymer. Nanocomposite electrolytes were prepared by the addition of 5 wt % of organically modified layered silicate (montmorillonite) into the gel polymer electrolytes. The enhancement of the ionic conductivity as well as mechanical properties was observed in the nanocomposite systems. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 894–899, 2004 相似文献
84.
Acicular goethite particles were synthesized by oxidation of an alkaline suspension of ferrous hydroxide using a bubble column with draft tubes of different diameters at a constant temperature of 40°C. The oxidation rate increased with decreasing draft tube diameter. The mean size based on the major axis of acicular particle decreased with increasing oxidation rate and decreasing draft tube diameter. The major axis was found to grow preferentially compared with the minor axis. The mean size of major axis was correlated well to the modified reaction rate defined as a product of the reaction rate per unit volume of the reactor multiplied by the ratio of the column diameter to the draft tube diameter, irrespective of the draft tube diameter. 相似文献
85.
An increase in the depolymerization of chitosan was found with an increased concentration of sodium perborate. Acetic anhydride was added to reacetylated chitosan in a molar ratio per gulcosamine unit, and the amide I band of IR spectra changed with the addition of acetic anhydride. Sixteen chitosans with various molecular weights (MWs) and degrees of deacetylation (DODs) were prepared. X‐ray diffraction patterns indicated their amorphous and partially crystalline states. Increases in the chitosan MW and DOD increased the tensile strength (TS). TS of the chitosan films ranged from 22 to 61 MPa. However, the elongation (E) of chitosan films did not show any difference with MW. TS of chitosan films decreased with the reacetylation process. However, E of chitosan films was not dependent on DOD. The water vapor permeabilities (WVPs) of the chitosan films without a plasticizer were between 0.155 and 0.214 ng m/m2 s Pa. As the chitosan MW increased, the chitosan film WVP increased, but the values were not significantly different. Moreover, the WVP values were not different from low DOD to high DOD. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 3476–3484, 2003 相似文献
86.
Han Mo Jeong Shang Hoon Lee Kwang Jae Cho Young Tae Jeong Kap Ku Kang Jae Kwon Oh 《应用聚合物科学杂志》2002,84(9):1709-1715
The block copolymer of poly(1‐hexadecene) (PHD) and polypropylene (PP) was effectively synthesized by the sequential polymerization of propylene and 1‐hexadecene by using highly isospecific TiCl3/Cp2Ti(CH3)2 (Cp = cyclopentadienyl). The block copolymers had two separate melting temperatures of constituent blocks. The modulus of PHD–PP block copolymer was enhanced as the content of sequentially polymerized PP block was increased. The elongation at break showed positive deviation at the intermediate compositions from the simple additive values of constituent homopolymers. Shape memory effect which utilizes the crystalline PHD block as a reversible phase and the crystalline PP block as a fixed structure was examined. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1709–1715, 2002; DOI 10.1002/app.10551 相似文献
87.
Hoo Kun Lee Kwan Sik Chun Hyun Soo Park Jong Hyun Cho 《Korean Journal of Chemical Engineering》1989,6(4):294-299
A mathematical model for an absorption of nitrogen oxides into water in packed column was developed based on the mass-transfer
coefficient in packed column and the chemical reaction accompanying NO
x
absorption produces HNO3 and HNO2 in the liquid phase. The subsequent dissociation of HNO2 in the liquid-phase results in the formation of HNO3 and NO gas, and then this NO gas follows to be oxidized by O2 in air. The important factors influenced on the absorption of NO
x
are the oxidation state of NO gas and the partial pressure of nitrogen oxides in the gas. The efficiency of NO
x
absorption increases with the increase of the partial pressure of NO
x
. The most critical value for using the model is the constant of
.The selection of 11×10−4kg·mol/atm·m2·sec for
resonable for this model. 相似文献
88.
Y. J. Cho P. S. Song C. G. Lee Y. Kang S. D. Kim L. T. Fan 《Chemical Engineering Communications》2005,192(3):257-271
Liquid dispersion in the radial direction was investigated in the riser of a viscous liquid-solid fluidized bed 0.102 m in diameter and 3.5 m in height. Pressure fluctuations in the riser were also measured and analyzed to examine the behavior of fluidized particles. Effects of liquid velocity (0.15-0.45 m/s), solid circulation rate (2-8 kg/m2s), particle size (1-3 mm), and liquid viscosity (0.96-38 mPas) on pressure fluctuations and the liquid radial dispersion coefficient were determined. The infinite space model was employed to obtain the radial dispersion coefficient from the radial concentration profiles of the tracer. The pressure fluctuations were analyzed by means of autocorrelation coefficient as well as power spectral density function. The dominant frequency obtained from the autocorrelation coefficient or power spectral density function of pressure fluctuations decreases with increasing liquid viscosity or liquid velocity, but it increases with increasing particle size. The liquid radial dispersion coefficient decreases with increasing liquid velocity or viscosity, but it increases as the solid circulation rate or particle size increases. The liquid radial dispersion coefficient is related closely to the resultant behavior of fluidized particles. The radial dispersion coefficient has been well correlated with operating variables in terms of dimensionless groups. 相似文献
89.
In a previous study, CETP inhibitory peptide (3 kDa) was isolated from hog plasma. The peptide, synthesized chemically according
to the amino acid sequence of the 3-kDa peptide (designated P28), showed CETP inhibitory activity both in vitro and in vivo [Cho et al. (1998) Biochim. Biophys. Acta 1391, 133–144]. We report herein further unique features of P28 when it was associated with the cholesteryl ester (CE)-donor and-acceptor lipoproteins. Lipoprotein substrates with P28 present in both HDL (as a CE-donor) and LDL (as a CE-acceptor) served as poor substrates, with CE-transfer activity decreased
up to 60% compared to normal substrates without P28. P28 was found to be located in HDL fractions of hog plasma and showed the same electromobility as that visualized by PAGE on
7% polyacrylamide gel under nondenaturing conditions. Addition of apolipoprotein A-1 (apoA-1) or apoB antibody to a normal
CE-transfer mixture did not alter CE-transfer activity. However, addition of apoA-1 or −B antibody to a CETP-inhibition mixture
decreased the inhibitory activity of P28 by ca. 20%. Western blot analysis revealed that P28 was associated only with human and hog HDL among several lipoproteins purified from human, hog, and rabbit. CFTP-inhibition
assays with various lipoprotein substrates revealed that P28 exhibited substrate-specific inhibitory activity. The inhibitory activity of P28 was highly dependent on the type of lipoprotein substrate (whether CE-donor or-acceptor); P28 inhibited CE transfer from HDL to LDL, but it did not inhibit CE transfer from HDL to HDL. 相似文献
90.
Changyong Choi Su Young Chae Tai‐Hyoung Kim Jung Keon Kweon Chong Su Cho Mi‐Kyeong Jang Jae‐Woon Nah 《应用聚合物科学杂志》2006,99(6):3520-3527
Diblock copolymers with different poly(ε‐caprolactone) (PCL) block lengths were synthesized by ring‐opening polymerization of ε‐caprolactone in the presence of monomethoxy poly(ethylene glycol) (mPEG‐OH, MW 2000) as initiator. The self‐aggregation behaviors and microscopic characteristics of the diblock copolymer self‐aggregates, prepared by the diafiltration method, were investigated by using 1H NMR, dynamic light scattering (DLS), and fluorescence spectroscopy. The PEG–PCL block copolymers formed the self‐aggregate in an aqueous environment by intra‐ and/or intermolecular association between hydrophobic PCL chains. The critical aggregation concentrations of the block copolymer self‐aggregate became lower with increasing hydrophobic PCL block length. On the other hand, reverse trends of mean hydrodynamic diameters were measured by DLS owing to the increasing bulkiness of the hydrophobic chains and hydrophobic interaction between the PCL microdomains. The partition equilibrium constants (Kv) of pyrene, measured by fluorescence spectroscopy, revealed that the inner core hydrophobicity of the nanoparticles increased with increasing PCL chain length. The aggregation number of PCL chain per one hydrophobic microdomain, investigated by the fluorescence quenching method using cetylpyridinium chloride as a quencher, revealed that 4–20 block copolymer chains were needed to form a hydrophobic microdomain, depending on PCL block length. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 99: 3520–3527, 2006 相似文献