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41.
Summary New types of comb-shaped polyesters have been prepared by transesterification of 2,2-dioctadecyl-1,3-propanediol and the three isomeric diphenyl phthalates. Intrinsic viscosity and SEC analyses allowed determination of DPs (60–89) and molar masses; results compare well with absolute average weight molar masses (56,000–118,000) determined by low-angle laser light scattering. High-resolution 13C NMR reveals the characteristic aromatic and glycol polyester patterns; it resolves many side-chain methylene carbons, but shows no evidence of end-groups. All the polyesters are crystalline as shown by X-ray diffractometry and DSC, the crystallinity being exclusively due to the octadecyl side-group crystallization in the hexagonal form. The results indicate that the crystallinity decreases substantially when going from the ortho- to the terephthalate polyester. 相似文献
42.
The influence of the linoleic acid levels of diets containing partially hydrogenated marine, oils (HMO) rich in isomeric 16∶1,
18∶1, 20∶1 and 22∶1 fatty acids on the fatty acid profiles of lipids from rat liver, heart and adipose tissue was examined.
Five groups of rats were fed diets containing 20 wt% fat−16% HMO+4% vegetable oils. In these diets, the linoleic acid contents
varied between 1.9% and 14.5% of the dietary fatty acids, whereas the contents oftrans fatty acids were 33% in all groups. A sixth group was fed a partially hydrogenated soybean oil (HSOY) diet containing 8%
linoleic acid plus 32%trans fatty acids, mainly 18∶1, and a seventh group, 20% palm oil (PALM), with 10% linoleic acid and notrans fatty acids.
As the level of linoleic acid in the HMO diets increased from 1.9% to 8.2%, the contents of (n−6) polyunsaturated fatty acids
(PUFA) in the phospholipids increased correspondingly. At this dietary level of linoleic acid, a plateau in (n−6) PUFA was
reached that was not affected by further increase in dietary 18∶2(n−6) up to 14.5%. Compared with the HSOY- or PALM-fed rats,
the plateau value of 20∶4(n−6) were considerably lower and the contents of 18∶2(n−6) higher in liver phosphatidylcholines
(PC) and heart PC. Heart phosphatidylethanolamines (PE) on the contrary, had elevated contents of 20∶4(n−6), but decreased
22∶5(n−6) compared with the PALM group.
All groups fed HMO had similar contents oftrans fatty acids, mainly 16∶1 and 18∶1, in their phospholipids, irrespective of the dietary 18∶2 levels, and these contents were
lower than in the HSOY group.
High levels of linoleic acid consistently found in triglycerides of liver, heart and adipose tissue of rats fed HMO indicated
that feeding HMO resulted in a reduction of the conversion of linoleic acid into long chain PUFA that could not be overcome
by increasing the dietary level of linoleic acid. 相似文献
43.
Nina Hammer Ingvar Kvande Wouter van Beek De Chen Magnus Rønning 《Topics in Catalysis》2007,45(1-4):25-29
In situ X-ray absorption spectroscopy (XAS) has been performed to investigate the active site on Au-based catalysts in the water-gas
shift (WGS) reaction. The surface area and hence the WGS activity is higher for AuTiO2 catalysts supported on carbon nanofibres (CNF) than TiO2. The WGS reaction rate depends on the Au coordination number with an apparent maximum close to eight which corresponds to
a particle size of approximately 2.5–3.0 nm. A likely cause for the changes in the electronic structure of Au is the adsorption
of CO on the surface, which also creates a small positive charge in the Au atoms. The catalytic activity significantly improves
when titania is present compared to Au deposited directly on CNF. 相似文献
44.
Erik Løvaas 《Journal of the American Oil Chemists' Society》1991,68(6):353-358
The antioxidative effects of spermine, spermidine and putrescine were determined by measurement of primary and secondary oxidation products of polyunsaturated fatty acids, using gas and liquid chromatography as well as spectrophotometric recordings. It was demonstrated that polyamines inhibit the oxidation of polyunsaturated fatty acids,α-tocopherol and carotenoid pigments. Both linear and nonlinear dose/response relationships have been observed. The efficiency of a given polyamine was correlated with the number of amine groups in the molecule. Spermine was, thus, more efficient than spermidine, which in turn had a higher efficiency than putrescine. The relative antioxidative effect was as follows: spermine (100.0), spermidine (61.0), putrescine (23.0), ethoxyquin (27.6), ascorbyl palmitate (18.3), octyl gallate (7.9), tert butylhydroquinone (6.3), butylated hydroxyanisole (3.6) andα-tocopherol (3.4). 相似文献
45.
Repeated administration of highly purified eicosapentaenoic acid (as ethyl ester) resulted in a decrease in plasma triglycerides
and high density lipoprotein (HDL) cholesterol. This was accompanied by a stimulation in the activities of carnitine palmitoyltransferase,
fatty acyl-CoA oxidase and peroxisomal β-oxidation in the liver. The results suggest that the triglyceride-lowering effect
observed with eicosapentaenoic acid may be due to a reduced supply of fatty acids for hepatic triglyceride synthesis because
of increased fatty acid oxidation. Eicosapentaenoic acid feeding marginally affected the triglyceride content of heart and
mitochondrial and peroxisomal enzyme activities. 相似文献
46.
Radiation‐induced graft copolymerization of maize starch/acrylic acid has been performed. Also, natural byproduct wood pulp was used after chemical treatment for the removal of metal ions from the investigated wastewater. The surface and structure morphology of the wood pulp and starch/acrylic acid were investigated by scanning electron microscopy and infrared spectroscopy. The physical parameters, such as swelling, gel percentage, and grafting efficiency (%) of starch/acrylic acid copolymer, were studied. The factors affecting the abilities of the prepared materials for removing heavy metal ions and dyes from aqueous solutions were studied. It was found that the maximum metal uptake is in the following sequence: Fe3+ > Cr3+ > Pb2+ > Cd2+. The adsorption capacity of such investigated metal ions increases with the increase of pH values. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci, 2006 相似文献
47.
Rønnestad H 《Meat science》1991,30(3):257-264
The aim of the study was to ascertain whether the amino acid 3-methylhistidine can be used to quantify skeletal meat protein in meat trimmings. 3-Methyhistidine from different carcass trimmings was quantified by a fluorescent HPLC method. Four trimmings with three subsamples each were examined. The subsamples were analysed in duplicate. The results showed high analytical variations between duplicates and subsamples. The average concentration of 3-methylhistidine in the four trimmings was 135 μg/g fat-free and connective tissue-free meat. Compared to earlier studies this value is high. Because of the rather high analytical variation, further research must be done to evaluate the use of 3-methylhistidine as an indicator for skeletal meat proteins in whole carcass trimmings. 相似文献
48.
Christian Schøning Tor Grande 《JOM Journal of the Minerals, Metals and Materials Society》2006,58(2):58-61
The infiltration of molten electrolyte and sodium is known to deteriorate the refractory in aluminum electrolysis. The mineralogical
changes due to reactions with molten fluorides have previously been described throughly, while the effect of sodium has not
been considered in detail. This paper presents an experimental study of the chemical stability of some refractory materials
in sodium-rich environments. The materials were exposed to sodium vapor at 800°C for 4 hours. The mineralogical transformations
and deterioration of the materials due to reactions with sodium were analyzed by x-ray diffraction and optical and electron
microscopy. 相似文献
49.
E. E. Abd El Aal W. Zakria A. Diab S. M. Abd El Haleem 《Journal of Materials Engineering and Performance》2003,12(2):172-178
The anodic dissolution of nickel was studied galvanostatically in hydrochloric acid solutions of various concentrations. The
reaction orders of chloride ion and hydrogen ion concentrations were found to be 0.5 and 1.0, respectively. An anodic Tafel
slope equal to 120 ± 10 mV · decade−1 was obtained. The dissolution rate of nickel at constant acid concentration was increased with stirring of the solution and
increasing temperature. The activation energy, ΔH, for the anodic dissolution process was found to be 12 kcal · mol−1. The presence of oxygen in solutions assisted the passivation process. The effect of addition of aniline and some of its
derivatives (o-, m-, and p-anisidine) as inhibitors on the dissolution kinetics of Ni in 1 M HCl was also investigated. These
compounds inhibited the anodic dissolution of nickel without affecting the Tafel slope, indicating that the adsorption of
such inhibitors could not interfere with the mechanism of metal dissolution. 相似文献
50.