全文获取类型
收费全文 | 6148篇 |
免费 | 609篇 |
国内免费 | 17篇 |
专业分类
电工技术 | 90篇 |
综合类 | 14篇 |
化学工业 | 1457篇 |
金属工艺 | 237篇 |
机械仪表 | 436篇 |
建筑科学 | 116篇 |
矿业工程 | 2篇 |
能源动力 | 276篇 |
轻工业 | 614篇 |
水利工程 | 14篇 |
石油天然气 | 1篇 |
无线电 | 1173篇 |
一般工业技术 | 1487篇 |
冶金工业 | 179篇 |
原子能技术 | 108篇 |
自动化技术 | 570篇 |
出版年
2024年 | 13篇 |
2023年 | 110篇 |
2022年 | 151篇 |
2021年 | 271篇 |
2020年 | 207篇 |
2019年 | 209篇 |
2018年 | 272篇 |
2017年 | 253篇 |
2016年 | 309篇 |
2015年 | 258篇 |
2014年 | 331篇 |
2013年 | 437篇 |
2012年 | 451篇 |
2011年 | 548篇 |
2010年 | 414篇 |
2009年 | 438篇 |
2008年 | 326篇 |
2007年 | 232篇 |
2006年 | 234篇 |
2005年 | 184篇 |
2004年 | 177篇 |
2003年 | 155篇 |
2002年 | 141篇 |
2001年 | 87篇 |
2000年 | 86篇 |
1999年 | 83篇 |
1998年 | 90篇 |
1997年 | 67篇 |
1996年 | 56篇 |
1995年 | 51篇 |
1994年 | 25篇 |
1993年 | 12篇 |
1992年 | 22篇 |
1991年 | 13篇 |
1990年 | 15篇 |
1989年 | 9篇 |
1988年 | 9篇 |
1987年 | 7篇 |
1986年 | 3篇 |
1985年 | 6篇 |
1984年 | 2篇 |
1983年 | 1篇 |
1981年 | 2篇 |
1980年 | 3篇 |
1979年 | 1篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1974年 | 1篇 |
排序方式: 共有6774条查询结果,搜索用时 15 毫秒
71.
Inorganic–organic hybrid materials for the optical waveguide were synthesized by the sol–gel process starting from the acid-catalyzed solutions of phenyltrimethoxysilane, methyltriethoxysilane, and tetraethylorthosilicate. The control of the refractive index in the organically modified silicate films was achieved by varying the content of phenyltrimethoxysilane incorporated as a refractive index modifier. A single spin-coating with the precursor solution produced a crack-free buffer layer of 22-μm thickness with a dense microstructure. For the fabrication of the patterned guiding layer on top of the buffer layer, the microfluidic lithography method was used. The patterned microlines of the linewidth of 20–35 μm with a sharp edge definition could form by filling the precursor solutions into the microchannels associated with the polydimethylsiloxane microfluidic device. The patterned guiding layer was optically transparent as similar as the bare quartz glass at the wavelength above 500 nm and had a low propagation loss of 0.77 dB/cm at 1310 nm. 相似文献
72.
Polyurethane anionomer dispersions were prepared from hydrogenated diphenylmethane diisocyanate (H12MDI) or isophorone diisocyanate (JPDI), poly(caprolactone) (PCL) diol, 1,4-butane diol (BD), and dimethylolpropionic acid (DMPA). Upon neutralization of the DMPA with triethylamine (TEA), the NCO-terminated polyurethane (PU) ionomers were self-emulsified by adding water, followed by chain extension using triethylenetetramine (TETA) in aqueous media. Polyurethanes from H12MDI showed coarser dispersion and better tensile properties over those from IPDI. Polyurethanes prepared by the one-shot method had better dispersion and tensile properties over those by the two-shot method. When some of the PCL diol was replaced by DMPA or BD, tensile strength increased and ductility decreased due mainly to the increased chain rigidity and intermolecular forces. © 1994 John Wiley & Sons, Inc. 相似文献
73.
The effects of estrogen-induced hyperlipidemia on plasma lipid peroxidation, fatty acid composition and osmotic fragility
of erythrocytes in chickens were studied. Young male chickens implanted with estrogen for three wk developed a marked hyperlipidemia.
Plasma levels of triglyceride, cholesterol and phospholipid were elevated 68-, four- and 24-fold, respectively, over controls.
There was also a two-fold increase in plasma lipid peroxidation measured by the thiobarbituric acid test. Vitamin E supplement
(1,000 IU/kg diet) reduced the plasma lipid peroxidation to the control level, but had no effect on the plasma lipid content.
Estrogen-induced hyperlipidemia resulted in changes in the fatty acid composition of membrane lipids of erythrocytes. The
major changes were an increase in oleic acid from 10.0% to 14.2% and a decrease in linoleic acid from 31.3% to 26.0%. The
erytrocytes with an altered membrane fatty acid composition were found to have an increased osmotic fragility. It was apparent
that there was a direct correlation between the oleic acid content and the osmotic fragility of erythrocytes. 相似文献
74.
Kee Man LeeTae Kwon Kim Won Jin KimSeung Gon Kim Jeong Park Sang In Keel 《Fuel》2002,81(17):2249-2255
A visualization study on the effect of forcing amplitude in tone-excited jet diffusion flames has been conducted. Visualization techniques are employed using optical schemes, which are a light scattering photography. Flame stability curve is attained according to Reynolds number and forcing amplitude at a fuel tube resonant frequency. Flame behavior is globally grouped into two from attached flame to blown-out flame according to forcing amplitude; one sticks the tradition flame behavior which has been observed in general jet diffusion flames and the other shows a variety of flame modes such as the flame of a feeble forcing amplitude where traditionally well-organized vortex motion evolves, a fat flame, an elongated flame, and an in-burning flame. Particular attention is focused on an elongation flame, which is associated with a turnabout phenomenon of vortex motion, and on a reversal of the direction of vortex roll-up. It is found that the flame length with forcing amplitude is the direct outcome of the evolution process of the formed inner flow structure. Especially the negative part of the acoustic cycle under the influence of a strong positive pressure gradient causes the shapes of the fuel stem and fuel branch part and even the direction of vortex roll-up to dramatically change. 相似文献
75.
Hydrogen sulfide gas was removed in a 2-dimensional gas-lift reactor by the photosynthetic microorganismChlorobium thiosulfatophilum using light emitting diodes (LEDs) as a light source. LEDs saved light energy by 99% compared with the incandescent light
source. The plate-type gas-lift reactor removed hydrogen sulfide five times better per unit mg of protein, and performed two
times better in the maximum performance per unit luminous flux, compared with cylindrical fermentors. 相似文献
76.
Mun-Soo Yun Ki-Young Jeong Eui-Wan Lee Bong-Soo Jin Seong-In Moon Chil-Hoon Doh 《Korean Journal of Chemical Engineering》2006,23(2):230-236
The aim of this paper is to study the electrochemical behavior of Si-C material synthesized by heating a mixture of silicon
and polyvinylidene fluoride (PVDF) in the ratios of 5, 20, and 50 wt%. The particle size of the synthesized material was found
to be increased with increase in the PVDF ratio. The coexistence of silicon with carbon was confirmed from the XRD analysis.
A field emission scanning electron microscope (FESEM) study performed with the material proved the improvement in coating
efficiency with increase in the PVDF ratio. Coin cells of the type 2025 were made by using the synthesized material, and the
electrochemical properties were studied. An electrode was prepared by using the developed Si-C material. Si-C|Li cells were
made with this electrode. A charge|discharge test was performed for 20 cycles at 0.1 C hour rate. Initial charge and discharge
capacities of Si-C material derived from 20 wt% of PVDF was found to be 1,830 and 526 mAh|g, respectively. Initial charge/discharge
characteristics of the electrode were analyzed. The level of reversible specific capacity was about 216mAh/g at Si-C material
derived from 20 wt% of PVDF, initial intercalation efficiency (IIE), intercalation efficiency at initial charge/discharge,
was 68%. Surface irreversible specific capacity was 31 mAh/g, and average specific resistance was 2.6 ohm * g. 相似文献
77.
Ki-Pung Yoo Hun Yong Shin Min Jeong Noh Seong Sik You 《Korean Journal of Chemical Engineering》1997,14(5):341-346
To design a supercritical fluid extraction process for the separation of bioactive substances from natural products, a quantitative
knowledge of phase equilibria between target biosolutes and solvent is necessary. How-ever, mostly no such information is
available in literature to date. Thus in the present study, illustratively the solubility of bioactive coumarin and its various
derivatives (i.e., hydroxy-, methyl-, and methoxy-derivatives) in supercritical CO2 were measured at 308.15–328.15 K and 10–30 MPa. Also, the pure physical properties such as normal boiling point, critical
constants, acentric factor, molar volume and standard vapor pressure for coumarin and its derivatives were estimated. By these
estimated information, the measured solubilities were quantitatively correlated by an approximate lattice equation of state
proposed recently by the present authors. 相似文献
78.
Case-based context ontology construction using fuzzy set theory for personalized service in a smart home environment 总被引:1,自引:1,他引:0
Mye Sohn Sunghwan Jeong Hyun Jung Lee 《Soft Computing - A Fusion of Foundations, Methodologies and Applications》2014,18(9):1715-1728
To provide context-based personalized services utilizing smart appliances in a smart home environment, we propose a framework for PersonAlized Service disCovery Using FuZZY-based CBR and Context Ontology (PASCUZZY). Basically, the PASCUZZY framework is implemented on case-based context ontology. To generate and manage the case instances on the case-based context ontology, we adopt the fuzzy set theory to transpose numerical-type context data sensed from the surrounding environment. The context is transposed to linguistic-type context instances on the context ontology. In addition, to formalize and manage the context and services as multi-attributed data, the context ontology was developed reflecting the structure of cases borrowed from case-based reasoning. Furthermore, we propose adaptation methods to adjust the generic fuzzy membership functions depending on the inhabitants’ context. It is performed by modifying the values of the membership number and/or modifying the numbers of the linguistic terms that are based on the inhabitants’ context to affect the membership numbers. The adapted membership functions return the personalized degree of memberships depending on the specialized context of a specific fuzzy variable. Inevitably, the number of cases on the case-based context ontology will be increased from time to time. We apply Ward’s method not only to reduce the search effort via a hierarchical clustering on the case-based context ontology but also to find the most similar service as a solution to the new context. To verify the superiority of the PASCUZZY framework, we perform two kinds of evaluations. First, we evaluate the effectiveness of the adaptation of the fuzzy membership functions. Second, we verify the effectiveness of the application of a clustering method to the case instances of the case-based context ontology to identify the most similar service. Results of the experiment verified the effectiveness and superiority of the PASCUZZY framework. 相似文献
79.
Tae Oan Ahn Chang Kee Kim Byung Kyu Kim Han Mo Jeong Jung Do Huh 《Polymer Engineering and Science》1990,30(6):341-349
Binary blends of ethylene vinyl alcohol copolymers, containing 62 (EVOH-62) and 71 (EVOH-71) mole percent vinyl alcohols, with nylons (nylon-6, nylon-6/12, and nylon-12) have been prepared from melt mixing in a twin screw compounding machine. Morphological, thermal, rheological, and mechanical properties were determined. EVOH-62/nylon-6 and EVOH-71/nylon-6 blends showed homogeneous phase morphologies in the nylon-6-rich region, and fine phase separations (c.a. 2 × 10?7 m) in the EVOH-rich region. Melting point depression, positive deviations in viscosity and flexural modulus, and negative deviation in impact strength from the simple additive rule were generally observed. And the results were possibly interpreted in terms of compatibility and increased nylon/EVOH interactions over the nylon/nylon interactions. On the contrary, clean phase separations in large domains were observed from EVOH-71/nylon-6/12 and EVOH-71 /nylon-12 blends. Fibrillation was also obtained from EVOH rich blends. Probably due to the incompatible nature of these blends, yield at low rate of shear and a mechanical property drop were also observed. 相似文献
80.
Specimens of two engineerig plastics i.e., poly(ether imide), PEI, and poly(2,6-dimethyl- 1,4-phenylene ether), PPE, were injection molded employing a 40t Van Dorn injection molding machine and industrial practices. The mold and melt temperatures and the injection speed were varied in a limited range which furnished acceptable samples. The density, birefringence, residual stress distributions, flexure and tensile properties, and crack development of the injection molded specimens were studied. Vacuum compression molded samples were also prepared to investigate the role played by the cooling rate in shaping microstructural distributions. The results revealed significant differences in the development of microstructure of the molded specimens of the two resins, which was related to rheology and molding conditions on one hand and to development of cracks and ultimate properties on the other hand. 相似文献