全文获取类型
收费全文 | 7417篇 |
免费 | 817篇 |
国内免费 | 7篇 |
专业分类
电工技术 | 124篇 |
综合类 | 10篇 |
化学工业 | 2031篇 |
金属工艺 | 312篇 |
机械仪表 | 510篇 |
建筑科学 | 89篇 |
矿业工程 | 2篇 |
能源动力 | 315篇 |
轻工业 | 504篇 |
水利工程 | 12篇 |
石油天然气 | 1篇 |
无线电 | 1383篇 |
一般工业技术 | 1990篇 |
冶金工业 | 276篇 |
原子能技术 | 96篇 |
自动化技术 | 586篇 |
出版年
2024年 | 6篇 |
2023年 | 91篇 |
2022年 | 136篇 |
2021年 | 215篇 |
2020年 | 181篇 |
2019年 | 265篇 |
2018年 | 255篇 |
2017年 | 311篇 |
2016年 | 350篇 |
2015年 | 309篇 |
2014年 | 432篇 |
2013年 | 519篇 |
2012年 | 585篇 |
2011年 | 656篇 |
2010年 | 429篇 |
2009年 | 456篇 |
2008年 | 424篇 |
2007年 | 306篇 |
2006年 | 268篇 |
2005年 | 208篇 |
2004年 | 208篇 |
2003年 | 233篇 |
2002年 | 196篇 |
2001年 | 134篇 |
2000年 | 132篇 |
1999年 | 148篇 |
1998年 | 143篇 |
1997年 | 96篇 |
1996年 | 80篇 |
1995年 | 55篇 |
1994年 | 56篇 |
1993年 | 57篇 |
1992年 | 43篇 |
1991年 | 43篇 |
1990年 | 24篇 |
1989年 | 18篇 |
1988年 | 19篇 |
1987年 | 12篇 |
1986年 | 14篇 |
1985年 | 30篇 |
1984年 | 15篇 |
1983年 | 7篇 |
1982年 | 5篇 |
1981年 | 9篇 |
1980年 | 14篇 |
1979年 | 10篇 |
1977年 | 5篇 |
1976年 | 8篇 |
1975年 | 6篇 |
1974年 | 9篇 |
排序方式: 共有8241条查询结果,搜索用时 0 毫秒
991.
Multiwalled carbon nanotube (MWNT)/poly (vinyl alcohol) (PVA) blend membranes were prepared by the solution‐casting method to determine the effect of MWNTs with nanoscale empty inner space along the tube length on the pervaporation performance of a PVA membrane in the separation of alcohol/water mixtures. The blend membranes were then characterized with several analytical methods such as transmission electron microscopy, differential scanning calorimetry, and X‐ray diffractometry: Transmission electron microscopy showed that the MWNTs were homogeneously distributed through the PVA matrix. The glass‐transition temperature of the PVA membrane was increased from 69.21 to 78.53°C via blending with MWNTs. The crystallinity of the PVA matrix decreased with increasing MWNTs up to 5 wt % from 41 to 36%. The pervaporation properties of the blend membranes were completely different from those of the pure PVA membrane in the separation of water/ethanol mixtures. The flux of the membrane was increased with the amount of MWNTs, whereas the separation factor was maintained up to 1.0 wt % MWNTs. However, beyond that, it was reduced. These results suggested that two factors, the crystallinity of the membrane and the diameters of the MWNTs, affected the performance of the membranes. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009 相似文献
992.
Suk‐Woo Park Hyun‐Su Bae Zhi‐Cai Xing Oh Hyeong Kwon Man‐Woo Huh Inn‐Kyu Kang 《应用聚合物科学杂志》2009,112(4):2320-2326
Nylon 6 nanofibers containing silver nanoparticles (nylon 6/silver) were successfully prepared by electrospinning. The structure and properties of the electrospun fibers were studied with the aid of scanning electron microscopy, transmission electron microscopy, energy‐dispersive spectroscopy, and X‐ray diffraction. The structural analysis indicated that the fibers electrospun at maximum conditions were straight and that silver nanoparticles were distributed in the fibers. Finally, the antibacterial activities of the nylon 6/silver nanofiber mats were investigated in a broth dilution test against Staphylococcus aureus (Gram‐positive) and Klebsiella pneumoniae (Gram‐negative) bacteria. It was revealed that nylon 6/silver possessed excellent antibacterial properties and an inhibitory effect on the growth of S. aureus and K. pneumoniae. On the contrary, nylon 6 fibers without silver nanoparticles did not show any such antibacterial activity. Therefore, electrospun nylon 6/silver nanocomposites could be used in water filters, wound dressings, or antiadhesion membranes. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009 相似文献
993.
Weon Gyu Shin Chaolong Qi Jing Wang Heinz Fissan David Y.H. Pui 《Journal of aerosol science》2009,40(5):463-468
We investigated the dependence of unipolar diffusion charging of nanoparticles on the dielectric constant of the particle material experimentally. The examined nanoparticles (10–200 nm) cover a wide range of dielectric constant but have almost the same spherical or compact morphology. Measurements of both intrinsic charged fraction and mean charge per particle show very small differences among different materials. The level of the small difference is consistent with the estimation by Fuchs’ [(1963). On the stationary charge distribution on aerosol particles in bipolar ionic atmosphere. Geofisica Pura e Applicata, 56, 185–193] theory. 相似文献
994.
Membrane separation is an important processing technology used for separating food ingredients and fractionating value‐added components from food processing byproducts. Long‐term performance of polymeric membranes in food protein processing is impeded by the formation of fouled layers on the membrane surface as a result of protein adsorption onto the membrane surface. Surface modification of synthetic membranes, i.e., changing surface characteristics to reduce protein adsorption permanently, is one of the innovative ways of reducing the fouling of membrane surfaces. In this study, surface modification of flat‐sheet ultrafiltration membrane, polyethersulfone (PES), was investigated in improving the hydrophilicity of PES surfaces, thereby reducing adsorption of the protein caused by hydrophobic–hydrophobic interaction between the protein and the membrane. Hydrophilic polymer grafting through thin‐film composite using interfacial polymerization was employed to improve the hydrophilicity of the commercial PES membranes. Poly(vinyl alcohol), poly(ethylene glycol), and chitosan were chosen as hydrophilic polymers to graft on PES membrane because of their excellent hydrophilic property. Modified PES membranes were characterized by contact angle, FTIR, XPS, and AFM. Contact angles of modified PES membranes were reduced by 25 to 40% of that of the virgin PES membrane. XPS spectrum supported that the PES membranes were successfully modified by interfacial polymerization. Tapping‐mode AFM was used to examine the changes in surface topography of modified PES membranes. The PES membranes modified by interfacial polymerization showed lower roughness (from 1.2 to 2.0 nm) than that of virgin PES membrane (2.1 nm). The results of these instrumental analyses indicated that the PES membranes were successfully enhanced hydrophilically through interfacial polymerization. The protein adsorption on the modified membranes was reduced by 30 to 35% as a result of surface modification of the PES membranes using interfacial polymerization technique. Published 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009 相似文献
995.
Suk-Hwan Kang Kwang-Jae Woo Ki-Won Jun Yong Kang 《Korean Journal of Chemical Engineering》2009,26(6):1533-1538
Fischer-Tropsch synthesis for the production of C5+ hydrocarbons from syngas was carried out in a tubular fixed bed reactor (TFBR) and in a slurry bubble column reactor (SBCR).
The Co-based catalysts for FTS were prepared by the conventional wet-impregnation of γ-Al2O3. Effects of operating conditions such as GHSV (1,000–4,000 ml/g·hr), reaction temperature (220–250°C) and pressure (0.5–3.0MPa)
on the CO conversion and product selectivity of Co/γ-Al2O3 catalyst were examined in the TFBR and SBCR. The C5+ selectivity and olefin selectivity in an SBCR were found to be higher than that in a TFBR, whereas C2–C4 selectivity showed a reverse trend. The CO conversion and product distribution in an SBCR were less sensitive than that in
a TFBR with variations of reaction conditions. 相似文献
996.
In-Sun Cho Shin Tae Bae Dong Kyun Yim Dong Wan Kim Kug Sun Hong 《Journal of the American Ceramic Society》2009,92(2):506-510
CaNb2 O6 nanoparticles with a size range of 30–50 nm were synthesized by heat treatment at 600°C after a solvothermal process and their optical and photocatalytic properties were investigated. The prepared powders were characterized by X-ray powder diffractometer, field-emission scanning electron microscope, transmission electron microscope, UV-Vis diffuse reflectance spectroscopy, Fluorescence spectroscopy, and Raman spectroscopy. Compared with a powder of the same material prepared by a solid-state reaction (SS) method, the nanoparticles exhibited a higher Brunauer–Emmett–Teller (BET) surface area, more efficient light absorption, and enhanced photocatalytic activity for producing H2 from pure water under UV irradiation. The photoluminescence spectra revealed that a radiative recombination process is dominant in the powder prepared by the SS method (strong blue emission at 300 K) under UV light irradiation, while no obvious emission was observed in the nanoparticles. This decrease of the radiative recombination as well as the higher optical absorption ability and higher BET surface area resulting from the reduced dimensionality led to enhanced photocatalytic activity of the nanoparticles. 相似文献
997.
Cham Kim Jong Tae Kim Ki Soo Kim Seonju Jeong Ho Young Kim Yoon Soo Han 《Electrochimica acta》2009,54(24):5715-5720
In this study, we developed an immobilized TiO2 semiconductor on an ITO glass substrate (TiO2/ITO) and investigated its photocatalytic and electrochemical performance. The TiO2/ITO samples were prepared via a spin-coating process followed by calcination and were used for the photocatalytic or electrochemical degradation of an organic dye pollutant. The measured photocatalytic performance was comparable to that reported in previous publications; however, a remarkable result was obtained in our electrochemical system. The formation of hydroxyl radicals (OH) strongly dominated the electrochemical system, which resulted in outstanding degradation performance. Therefore, we propose a commercializable photoelectrochemical system that can maximize the degradation of pollutants in wastewater treatment plants. 相似文献
998.
Mrityunjay K. Singh Tae G. Kang Patrick D. Anderson Han E. H. Meijer Andy N. Hrymak 《American Institute of Chemical Engineers》2009,55(9):2208-2216
Various designs of the so called Low-Pressure Drop (LPD) static mixer are analyzed for their mixing performance using the mapping method. The two types of LPD designs, the RR and RL type, show essentially different mixing patterns. The RL design provides globally chaotic mixing, whereas the RR design always yields unmixed regions separated by KAM boundaries from mixed regions. The crossing angle between the elliptical plates of the LPD is the key design parameter to decide the performance of various designs. Four different crossing angles from 90° to 160° are used for both the RR and RL designs. Mixing performance is computed as a function of the energy to mix, reflected in overall pressure drop for all designs. Optimization using the flux-weighted intensity of segregation versus pressure drop proves the existence of the best mixer with an optimized crossing angle. The optimized angle proves to be indeed the LLPD design used in practice: the RL-120 with θ = 120°, although RL-140 θ = 140° performs as good. Shear thinning shows minor effects on the mixing profiles, and the main optimization conclusions remain unaltered. © 2009 American Institute of Chemical Engineers AIChE J, 2009 相似文献
999.
Masato Takeuchi Junichi Deguchi Manabu Hidaka Shiro Sakai Kyoungja Woo Pyuck-Pa Choi Jong-Ku Park Masakazu Anpo 《Applied catalysis. B, Environmental》2009,89(3-4):406-410
The photocatalytic oxidation of gaseous acetaldehyde with O2 on commercial TiO2 nano-particles could be successfully enhanced by a simple mechanical blending with a high-silica mordenite (MOR) zeolite, the surface of which showed high hydrophobic properties. When the TiO2 nano-particles of ca. 5–20 wt% were mixed with the MOR zeolite powders in an agate mortar for only 5 min, the blended TiO2/MOR samples showed higher photocatalytic reactivity as compared to the pure TiO2 nano-particles. Since the high-silica zeolite powders are highly transparent in UV light regions, the incident UV light is effectively irradiated onto the whole part of the TiO2 nano-particles without any loss of light intensity. Furthermore, the siliceous MOR zeolite powders effectively adsorb the gaseous acetaldehyde molecules and supply them onto the surfaces of the blended TiO2 nano-particles, resulting in an enhancement of the photocatalytic reactivity. 相似文献
1000.
Eui-Baek Byun Ha-Yeon Song Woo Sik Kim Jeong Moo Han Ho Seong Seo Sang-Hyun Park Kwangwook Kim Eui-Hong Byun 《International journal of molecular sciences》2021,22(14)
Although cisplatin is one of most effective chemotherapeutic drugs that is widely used to treat various types of cancer, it can cause undesirable damage in immune cells and normal tissue because of its strong cytotoxicity and non-selectivity. This study was conducted to investigate the cytoprotective effects of Cudrania tricuspidata fruit-derived polysaccharides (CTPS) against cisplatin-induced cytotoxicity in macrophages, lung cancer cell lines, and a mouse model, and to explore the possibility of application of CTPS as a supplement for anticancer therapy. Both cisplatin alone and cisplatin with CTPS induced a significant cytotoxicity in A549 and H460 lung cancer cells, whereas cytotoxicity was suppressed by CTPS in cisplatin-treated RAW264.7 cells. CTPS significantly attenuated the apoptotic and necrotic population, as well as cell penetration in cisplatin-treated RAW264.7 cells, which ultimately inhibited the upregulation of Bcl-2-associated X protein (Bax), cytosolic cytochrome c, poly (adenosine diphosphateribose) polymerase (PARP) cleavage, and caspases-3, -8, and -9, and the downregulation of B cell lymphoma-2 (Bcl-2). The CTPS-induced cytoprotective action was mediated with a reduction in reactive oxygen species production and mitochondrial transmembrane potential loss in cisplatin-treated RAW264.7 cells. In agreement with the results obtained above, CTPS induced the attenuation of cell damage in cisplatin-treated bone marrow-derived macrophages (primary cells). In in vivo studies, CTPS significantly inhibited metastatic colonies and bodyweight loss as well as immunotoxicity in splenic T cells compared to the cisplatin-treated group in lung metastasis-induced mice. Furthermore, CTPS decreased the level of CRE and BUN in serum. In summation, these results suggest that CTPS-induced cytoprotective action may play a role in alleviating the side effects induced by chemotherapeutic drugs. 相似文献