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131.
Murakami M Imamura E Shinohara H Kiri K Muramatsu Y Harada A Takada H 《Environmental science & technology》2008,42(17):6566-6572
We analyzed perfluorinated surfactants (PFSs) in 20 river samples and 5 wastewater secondary effluent samples in Japan to reveal their occurrence and sources. Nine PFS species were determined: perfluorooctanesulfonate (PFOS), perfluorooctane sulfonamide (FOSA), perfluoroheptanoate (PFHpA), perfluorooctanoate (PFOA), perfluorononanoate (PFNA), perfluorodecanoate (PFDA), perfluoroundecanoate (PFUA), perfluorododecanoate (PFDDA), and perfluorotridecanoate (PFTDA). PFSs were detected in all rivers, revealing nationwide contamination of rivers. In particular, 11 out of 20 river samples exceeded New Jersey guidance for PFOA in drinking water (40 ng/L). PFOS, PFHpA, PFOA, and PFNA were major species in Japan. Concentrations of PFOS, PFHpA, and PFNA in rivers were strongly correlated with population density, suggesting that the chemicals were derived from urban activities. PFOA showed a significant but weak correlation. We used crotamiton, a marker of sewage effluent, for further source analysis. Concentrations of PFOS, PFHpA, and PFNAwere strongly correlated with those of crotamiton, and plots of secondary effluents fell near the regression lines of rivers, indicating that the PFOS, PFHpA, and PFNA in rivers were derived from sewage effluent. On the other hand, PFOA was found at remarkably high levels (54-192 ng/L) in seven river samples containing low levels of crotamiton, suggesting that it was derived from nonsewage point sources, as well as sewage effluent. The total fluxes of sewage-derived PFOS, PFHpA, PFOA, and PFNA from Japan were estimated to be 3.6, 2.6, 5.6, and 2.6 t/year, respectively. This is the first report to identify PFOA in several rivers, derived from nonsewage point sources, by using a marker of sewage effluent. 相似文献
132.
Contrasting effects of water-soluble and water-insoluble dietary fibers on bile acid conjugation and taurine metabolism in the rat 总被引:2,自引:0,他引:2
The effect of the type of dietary fiber on the bile acid and taurine metabolism was examined in rats. Diets containing 10%
of various water-soluble fibers (citrus pectin, konjak mannan, guar gum) as compared to a fiber-free diet increased biliary
excretion of total bile acids. In contrast, water-insoluble dietary fibers (cellulose, corn bran, chitin; 10% in the diets)
as well as cholestyramine (5% in the diet) considerably, decreased bile acid excretion. Water-soluble dietary fibermediated
increases in bile acid excretion were totally attributable to increases in glycine-conjugates. Thus, these fibers greatly
increased by the bile acid glycine-to-taurine ratio (G/T). Excretio of glycine conjugates decreased more than that of taurine
conjugates in rats fed various water-insoluble dietary fibers. As a results, G/T in rats fed water-insoluble fibers was significantly
lowered as compared to G/T in animals fed a fiber-free diet. Cholestyramine did not affect the G/T ratio of bile acids. Fecal
bile acid excretion and the activities of hepatic cholesterol 7α-hydroxylase (EC 1.14.13.17) in rats fed various water-soluble
dietary fibers approximately doubled as compared to the respective values for rats fed a fiber-free diet. Whereas cholestyramine
greatly increased these parameters, water-insoluble fibers did not significantly affect them. Various water-soluble fibers
decreased hepatic concentration and urinary excretion of taurine as well as the activity of hepatic cysteine dioxygenase (EC
1.13.11.20). In contrast, water-insoluble fibers considerably increased hepatic taurine concentrations and enzyme activities.
The parameters for taurine metabolism were unaffected by cholestyramine. It was suggested that the types of dietary fiber
affected hepatic taurine synthesis and thus modified bile acid glycine/taurine ratios. 相似文献
133.
Masayuki Nagai Tatsuya Saeki Tadashi Nishino 《Journal of the American Ceramic Society》1990,73(5):1456-1460
Hydroxyapatite and Cl− -containing hydroxyapatite powders are prepared and characterized. Reversible substitution of CO2- 3 for OH− at the surface is presumed to be responsible for the sensor function. The role of Cl− , which is necessary to realize the sensor function and is incorporated during soaking treatment, is considered as follows. It may reduce the strain caused by the incorporation of CO2- 3 (which is larger than OH− ), and, hence, promote the reversible substitution reaction. This behavior is presumed because Cl− -containing hydroxyapatite samples exhibit sensor characteristics typical of CO2 without any treatment. 相似文献
134.
Tsuyoshi OchiaiYuichi Iizuka Kazuya NakataTaketoshi Murakami Donald A. TrykAkira Fujishima Yoshihiro KoideYuko Morito 《Diamond and Related Materials》2011,20(2):64-67
The electrochemical decomposition of environmentally persistent perfluorooctanoic acid (PFOA) was achieved by the use of a boron-doped diamond (BDD) electrode. The PFOA decomposition follows pseudo-first-order kinetics, with an observed rate constant (k1) of 2.4 × 10− 2 dm3 h− 1. Under the present reaction conditions, k1 increased with increasing current density and saturated at values over 0.60 mA cm− 2. Therefore, the rate-limiting step for the electrochemical decomposition of PFOA was the direct electrochemical oxidation at lower current densities. In the proposed decomposition pathway, direct electrochemical oxidation cleaves the C-C bond between the C7F15 and COOH in PFOA and generates a C7F15 radical and CO2. The C7F15 radical forms the thermally unstable alcohol C7F15OH, which undergoes F− elimination to form C6F13COF. This acid fluoride undergoes hydrolysis to yield another F− and the perfluorocarboxylic acid with one less CF2 unit, C6F13COOH. By repeating these processes, finally, PFOA was able to be totally mineralized to CO2 and F−. Moreover, whereas the BDD surface was easily fluorinated by the electrochemical reaction with the PFOA solution, medium pressure ultraviolet (MPUV) lamp irradiation in water was able to easily remove fluorine from the fluorinated BDD surface. 相似文献
135.
Yasumasa?Minemoto Shuji?AdachiEmail author Yuji?Shimada Toshihiro?Nagao Toshio?Iwata Yoshie?Yamauchi-Sato Takaya?Yamamoto Tadashi?Kometani Ryuichi?Matsuno 《Journal of the American Oil Chemists' Society》2003,80(7):675-678
The autoxidation processes of the cis-9,trans-11 (c9,t11) and trans-10,cis-12 (t10,c12) isomers of CLA were separately observed at ca. 0% RH and different temperatures. The t10,c12 CLA oxidized faster than the c9,t11 isomer at all tested temperatures. The first half of the oxidation process of t10,c12 CLA obeyed an autocatalytic-type rate expression, but the latter half followed first-order kinetics. On the other hand,
the entire oxidation process of c9,t11 CLA could be expressed by the autocatalytic-type rate expression. The apparent activation energies and frequency factors
for the autoxidation of the isomers were estimated from the rate constants obtained at various temperatures based on the Arrhenius
equation. The apparent activation energies for the CLA isomers were greater than those for the nonconjugated n−6 and n−3 PUFA
or their esters. However, the enthalpyentropy compensation held during the autoxidation of both the CLA and PUFA. This suggested
that the autoxidation mechanisms for the CLA and PUFA were essentially the same. 相似文献
136.
Water management in cathode gas diffusion electrode (GDE) of polymer electrolyte fuel cell (PEFC) is essential for high performance operation, because liquid water condensed in porous gas diffusion layer (GDL) and catalyst layer (CL) blocks oxygen transport to active reaction sites. In this study, the average liquid water content inside the cathode GDE of a low-temperature PEFC is experimentally and quantitatively estimated by the weight measurement, and the relationship between the water accumulation rate in the cathode GDE and the cell voltage is investigated. The liquid water behavior at the cathode is also visualized using an optical diagnostic, and the effects of operating conditions and GDL structures on the water transport in the cathode GDE are discussed. It is found that the liquid water content in the cathode GDE increases remarkably after starting the fuel cell operation due to the water production at the CL. At a high current density, the cell voltage drops suddenly after starting the operation in spite of a low water content in the cathode GDE. When the GDL thickness is increased, much water accumulates near the cathode CL and the fuel cell shuts down immediately after the operation. In the final section of this paper, the structure of cathode GDL that has several grooves for water removal is proposed to prevent water flooding and improve fuel cell performance. This groove structure is effective to promote the removal of the liquid water accumulated near the active catalyst sites. 相似文献
137.
Yan Liu Yoshihiro Kageyama Sumio Murakami 《International Journal of Mechanical Sciences》1998,40(2-3)
A new approach to creep cavitation damage is developed by combining the basic features of continuum damage mechanics and mechanism-based cavitation models. Based on a polycrystal microstructures simulated by Voronoi tessellation, an anisotropic continuum damage variable is defined, and its evolution is given by applying the mechanism-based equations of cavity nucleation and growth to each grain boundary. Macroscopic creep deformation coupled with the damage variable is calculated by damage mechanics equations. The proposed method has been applied to investigate the damage evolution under uniaxial tension and reversed shear loading conditions. 相似文献
138.
139.
140.
Nanospheres of poly(lactide-co-glycolide) (PLGA), a biodegradable polymer, have been prepared using the conventional solvent diffusion method. In this study,
a method combining the solvent diffusion method and a two-step (premix) membrane emulsification technique is proposed for
the preparation of monodisperse PLGA nanospheres with a diameter of 200 nm. The monodispersity of the PLGA nanospheres was
higher than that of nanospheres obtained by the conventional solvent diffusion method. Generally, preparation of small particles
or droplets by the membrane emulsification technique requires a supply of high-pressure nitrogen gas to force the emulsion
or dispersion solution through the small pores of the membrane. However, in the technique proposed here, low-pressure nitrogen
gas (0.02–0.11 kgf/cm2) is sufficient. Thus, using this technique, one can obtain monodisperse PLGA nanospheres with a diameter of 200 nm in a relatively
short period of time under low-pressure nitrogen gas. 相似文献