全文获取类型
收费全文 | 1447篇 |
免费 | 24篇 |
国内免费 | 5篇 |
专业分类
电工技术 | 59篇 |
综合类 | 4篇 |
化学工业 | 300篇 |
金属工艺 | 27篇 |
机械仪表 | 36篇 |
建筑科学 | 29篇 |
能源动力 | 47篇 |
轻工业 | 130篇 |
水利工程 | 6篇 |
无线电 | 113篇 |
一般工业技术 | 208篇 |
冶金工业 | 374篇 |
原子能技术 | 72篇 |
自动化技术 | 71篇 |
出版年
2023年 | 13篇 |
2022年 | 10篇 |
2021年 | 17篇 |
2020年 | 8篇 |
2019年 | 14篇 |
2018年 | 20篇 |
2017年 | 16篇 |
2016年 | 32篇 |
2015年 | 14篇 |
2014年 | 30篇 |
2013年 | 69篇 |
2012年 | 50篇 |
2011年 | 60篇 |
2010年 | 42篇 |
2009年 | 52篇 |
2008年 | 61篇 |
2007年 | 46篇 |
2006年 | 45篇 |
2005年 | 47篇 |
2004年 | 49篇 |
2003年 | 51篇 |
2002年 | 44篇 |
2001年 | 30篇 |
2000年 | 31篇 |
1999年 | 34篇 |
1998年 | 133篇 |
1997年 | 77篇 |
1996年 | 54篇 |
1995年 | 35篇 |
1994年 | 35篇 |
1993年 | 35篇 |
1992年 | 17篇 |
1991年 | 16篇 |
1990年 | 8篇 |
1989年 | 12篇 |
1988年 | 14篇 |
1987年 | 15篇 |
1986年 | 13篇 |
1985年 | 10篇 |
1984年 | 8篇 |
1983年 | 9篇 |
1982年 | 6篇 |
1981年 | 11篇 |
1980年 | 6篇 |
1979年 | 14篇 |
1978年 | 8篇 |
1977年 | 12篇 |
1976年 | 16篇 |
1974年 | 5篇 |
1972年 | 6篇 |
排序方式: 共有1476条查询结果,搜索用时 15 毫秒
991.
T Werfel A Morita M Grewe H Renz U Wahn J Krutmann A Kapp 《Canadian Metallurgical Quarterly》1996,107(6):871-876
The majority of allergen-specific T cells derived from inhalant allergen patch test lesions in patients with atopic dermatitis were previously found to produce a restricted type-2 cytokine pattern. Recent studies, however, have revealed that in chronic eczematous skin lesions of patients with atopic dermatitis, expression of the type-1 cytokine interferon-gamma predominates. To evaluate cytokine production by allergen-specific T cells in chronic atopic dermatitis, we established house dust mite (Dermatophagoides pteronyssinus)-specific T-cell clones from the dermis of chronic skin lesions of sensitized adult patients with atopic dermatitis. Frequencies of skin-derived T cells proliferating in the presence of Dermatophagoides pteronyssinus were between one in 138 and one in 4255, indicating that only a minority of skin-infiltrating T cells are allergen specific. When these cells were analyzed for their capacity to produce interferon-gamma, the majority (71%) of these cells were found to express interferon-gamma mRNA and to secrete interferon-gamma protein, either alone or in combination with interleukin-4. Phenotypic analysis revealed that 15% of skin-infiltrating allergen-specific T cells were CD8+. No selection of Vbeta elements was detected in Dermatophagoides pteronyssinus-specific T-cell clones. These studies demonstrate that allergen specificity of skin-infiltrating T cells is not restricted to a type-2 cytokine pattern in lesional atopic dermatitis. The notion that the majority of allergen-specific, skin-infiltrating T cells are capable of producing interferon-gamma further supports the concept that interferon-gamma expression has major pathogenetic relevance for the chronic phase of atopic dermatitis. 相似文献
992.
The anodic characteristics of the massive β-MnO2 doped with noble metals in sodium chloride solution
The anodic characteristics of the massive β-MnO2 doped with a slight amount of noble metals were investigated in NaCl aqueous solution. The doping of noble metal, especially Pd, decreases the chlorine overvoltage enormously. By the kinetic considerations, it was clarified that noble metal sites dispersed on the oxide surface serve effectively as an active site for the chlorine evolution reaction. Furthermore, it was suggested that new effective catalysts for the chlorine evolution might be developed by using such noble metal-doped β-MnO2 systems. 相似文献
993.
Isao Ishigaki Yosuke Morita Koichi Nishimura Norio Morishita Akihiko Ito 《应用聚合物科学杂志》1979,23(11):3383-3394
The iodine-initiated, solid-state copolymerization of the tetraoxane–1,3–dioxolane-methylal system has been studied by measuring the molecular weight distribution of the copolymer. The molecular weight distribution of the copolymer is found to be strongly dependent on the addition method of the 1,3-dioxolane–methylal solution to tetraoxane. The copolymer obtained by the one-addition copolymerization has a molecular weight distribution curve that shows a very broad distribution, with a discernible shoulder; and the copolymer obtained by the continuous-addition copolymerization has a very sharp curve. Particle size of the copolymer also influences the molecular weight distribution. For the one-addition copolymerization, the larger the particle size of the copolymer, the broader the molecular weight distribution. For the continuous-addition copolymerization, however, the molecular weight distribution is nearly constant regardless of particle size. The dependence of the molecular weight distribution on the polymerization time and the concentrations of iodine, 1,3-dioxolane, and methylal is discussed in detail. These results suggest that this copolymerization system is characterized by a reaction that proceeds from the surface to the center of the tetraoxane crystals. 相似文献
994.
Theoretical equations that describe the concentration profiles of immobilized and active species for reactive dyes were derived from the diffusion equation accompanied by the reaction with cellulose and water in the substrate. The diffusion coefficient D and the rate constant of the reaction with cellulose, kcell, and that with water in cellulose, kw, were estimated by using the theoretical equations and the cylindrical film roll method. The theory predicted that the apparent diffusion coefficients decreased with the hydrolysis of active species in cellulose. Results from diffusion experiments with C.I. Reactive Yellow 4 and Orange 1 show that the ratio P of kw to kcell for Orange 1 increased with increase in pH to about pH 13 and that the P for Yellow 4 was smaller than unity. Using an alternative experiment to diffusion, P of Orange 1 was measured to be 1.0–1.5, and that of Yellow 4 was smaller than unity at pH 11.6 at 30°C. It was therefore concluded that the D of active species was constant to a highly alkaline region and that the decrease in the apparent diffusion coefficient of Orange 1 was mainly due to the hydrolysis of active species in cellulose. 相似文献
995.
Li-Ngee Ho Hiroyasu Nishiguchi Katsutoshi Nagaoka Yusaku Takita 《Journal of Porous Materials》2006,13(3-4):237-244
A series of lanthanide (LA) phosphate were prepared by using N-(2-hydroxyethyl) ethylenediane-N,N′,N′-triacetic acid (H3hedtra) as a chelating agent. The obtained samples were characterized by using X-ray diffraction (XRD), nitrogen adsorption-desorption isotherm, thermal analysis (TG-DTA), transmission electron microscope (TEM) and TPD-ammonia desorption. The results showed that samples prepared through chelating agent route possessed smaller particle size which led to higher specific surface area with increased acidic sites compared with the reference samples prepared free of H3hedtra. It was also found that the acidic strength increased gradually from the light lanthanide phosphate to heavy lanthanide phosphate. Besides, pore size of the samples could be controlled by altering the mole ratio of the lanthanide(LA): H3hedtra. Pore size distribution of the samples became narrower through synthesis in the presence of H3hedtra. The precursor sol complex was investigated by FTIR and XRD and mesopore formation mechanism had been discussed. 相似文献
996.
A new type of cable supported bridge, cable-stayed CFT arch bridge, was proposed and its static strength was studied in this paper. Arch ribs consist of concrete filled steel tubes (CFT). CFTs have high resistance against bending moments and compressive axial forces and are ideal as arch ribs. A cable-stayed CFT arch bridge with a main-span of 300 m was designed and the safety of its structural members was checked by the limit state design method. Large deformation analysis was used to obtain sectional forces. The CFT arch ribs and the steel box girders and towers of the designed bridge satisfied the required safety criteria for ultimate design loads. The applied loads were further increased until the bridge collapsed when the arch ribs buckled. The amount of steel required for the cable-stayed CFT arch bridge was significantly lower than that for the cable-stayed bridge. It has been found that the proposed cable-stayed CFT arch bridge is feasible and potentially economical. 相似文献
997.
Effect of soluble microbial products on microbial metabolisms related to nutrient removal 总被引:2,自引:0,他引:2
In this study, the effect of soluble microbial products (SMP) on the metabolisms related to phosphate or nitrogen removal of activated sludge was investigated. Two anaerobic-aerobic activated sludge processes were operated, one with a hydraulic retention time (HRT) of 48 h (RunL) and the other 6.4 h (RunS). The longer HRT of RunL was intended to promote the accumulation of SMPs in the supernatant. With the sludge from RunS and the supernatant from both of the runs, supernatant exchange batch experiments (SEBEs) were conducted, in which the acetate uptake rate and phosphate release rates under anaerobic conditions and the phosphate uptake rate under aerobic conditions were measured as these metabolisms are related to enhanced biological phosphorus removal. The nitrification rate was also measured. The statistical analyses of the results from the SEBEs showed that the supernatant from RunL had an inhibitory effect on the anaerobic acetate uptake and nitrification of the sludge from RunS. The cause of which was attributed to SMPs in the supernatant from RunL. As a result, the inhibitory effect of SMPs on nitrification and anaerobic acetate uptake was confirmed. 相似文献
998.
Sobahan Mia Shota Mizukami Ryusei Fukuda Shigeki Morita Nobuyoshi Ohno 《Journal of Mechanical Science and Technology》2010,24(1):111-114
Different types of synthetic polyalphaolefin (PAO) oils and a mineral oil are considered in this study. High-pressure viscosity
test was done and pressure-viscosity coefficient was measured for all sample oils. Results showed the better performance of
PAO oils than the mineral oil. Authors also tested some other tribological properties such as low-temperature behavior, bulk
property, frictional coefficient, and wear behavior, which are important for wind turbine gear oil. Low-temperature behavior
and frictional property of PAO oils exhibited the better results. Study also showed that the prediction of low-temperature
fluidity is possible using the sound velocity in the oil. Finally, the presence of polymethakrylate (PMA) absorbent in PAO
oil exposed comparatively better results among all PAO oils. 相似文献
999.
Mitsuyuki Morita 《应用聚合物科学杂志》1994,52(5):711-719
The electrochromic behavior of polyaniline–poly(vinyl alcohol) composite films (CPAn–PVA) combined with electrochemically synthesized Prussian blue films (PB) was investigated in LiClO4? CH3CN nonaqueous aprotic solution. The combination was achieved by chemical deposition of CPAn–PVA on PB. When the combined films (CPAn–PVA–PB) are prepared with the appropriately low quantity of PB, CPAn–PVA–PB showed various visible absorption spectra overlapped roughly with the absorption of the component materials at different applied potentials. CPAn–PVA–PB provided the color change from green to blue at much lower applied potential than did CPAn–PVA. However, the combined PB eliminates protons from the first oxidized polyaniline chains to decrease the electrochemical activity of polyaniline. Therefore, to construct multicolor electrochromic devices by the combination of polyaniline with the other electrochromic materials, it is necessary to select the materials containing no deprotonation activity. © 1994 John Wiley & Sons, Inc. 相似文献
1000.
A precise absolute intensity calibration of a flat-field space-resolved extreme ultraviolet (EUV) spectrometer working in wavelength range of 60-400 ? is carried out using a new calibration technique based on radial profile measurement of the bremsstrahlung continuum in Large Helical Device. A peaked vertical profile of the EUV bremsstrahlung continuum has been successfully observed in high-density plasmas (n(e) ≥ 10(14) cm(-3)) with hydrogen ice pellet injection. The absolute calibration can be done by comparing the EUV bremsstrahlung profile with the visible bremsstrahlung profile of which the absolute value has been already calibrated using a standard lamp. The line-integrated profile of measured visible bremsstrahlung continuum is firstly converted into the local emissivity profile by considering a magnetic surface distortion due to the plasma pressure, and the local emissivity profile of EUV bremsstrahlung is secondly calculated by taking into account the electron temperature profile and free-free gaunt factor. The line-integrated profile of the EUV bremsstrahlung continuum is finally calculated from the local emissivity profile in order to compare with measured EUV bremsstrahlung profile. The absolute intensity calibration can be done by comparing measured and calculated EUV bremsstrahlung profiles. The calibration factor is thus obtained as a function of wavelength with excellent accuracy. It is also found in the profile analysis that the grating reflectivity of EUV emissions is constant along the direction perpendicular to the wavelength dispersion. Uncertainties on the calibration factor determined with the present method are discussed including charge-coupled device operation modes. 相似文献