全文获取类型
收费全文 | 5228篇 |
免费 | 119篇 |
国内免费 | 27篇 |
专业分类
电工技术 | 412篇 |
综合类 | 17篇 |
化学工业 | 1504篇 |
金属工艺 | 136篇 |
机械仪表 | 138篇 |
建筑科学 | 189篇 |
矿业工程 | 1篇 |
能源动力 | 244篇 |
轻工业 | 506篇 |
水利工程 | 19篇 |
石油天然气 | 7篇 |
无线电 | 292篇 |
一般工业技术 | 918篇 |
冶金工业 | 189篇 |
原子能技术 | 214篇 |
自动化技术 | 588篇 |
出版年
2023年 | 30篇 |
2022年 | 59篇 |
2021年 | 96篇 |
2020年 | 52篇 |
2019年 | 63篇 |
2018年 | 75篇 |
2017年 | 63篇 |
2016年 | 112篇 |
2015年 | 79篇 |
2014年 | 151篇 |
2013年 | 321篇 |
2012年 | 188篇 |
2011年 | 307篇 |
2010年 | 258篇 |
2009年 | 280篇 |
2008年 | 316篇 |
2007年 | 262篇 |
2006年 | 203篇 |
2005年 | 220篇 |
2004年 | 178篇 |
2003年 | 162篇 |
2002年 | 166篇 |
2001年 | 106篇 |
2000年 | 96篇 |
1999年 | 97篇 |
1998年 | 108篇 |
1997年 | 74篇 |
1996年 | 74篇 |
1995年 | 55篇 |
1994年 | 81篇 |
1993年 | 70篇 |
1992年 | 57篇 |
1991年 | 76篇 |
1990年 | 54篇 |
1989年 | 77篇 |
1988年 | 65篇 |
1987年 | 39篇 |
1986年 | 73篇 |
1985年 | 56篇 |
1984年 | 53篇 |
1983年 | 57篇 |
1982年 | 60篇 |
1981年 | 47篇 |
1980年 | 42篇 |
1979年 | 41篇 |
1978年 | 41篇 |
1977年 | 28篇 |
1976年 | 28篇 |
1975年 | 18篇 |
1973年 | 17篇 |
排序方式: 共有5374条查询结果,搜索用时 0 毫秒
121.
Comparison of thermophilic anaerobic digestion characteristics between single-phase and two-phase systems for kitchen garbage treatment 总被引:1,自引:0,他引:1
Lab-scale single-phase and two-phase thermophilic methane fermentation systems (SPS and TPS, respectively) were operated and fed with artificial kitchen waste. In both SPS and TPS, the highest methane recovery ratio of 90%, in terms of chemical oxygen demand by dichromate (CODcr), was observed at an organic loading rate (OLR) of 15 gCODcr/(l.d). The ratio of particle CODcr remaining to total CODcr in the influent was 0.1 and the ratio of NH(4)-N concentration to the input total nitrogen concentration was 0.5 in both SPS and TPS. However, the propionate concentration in the SPS reactor fluctuated largely and was 2 gCODcr/l higher than that in TPS, indicating less stable digestion. Regardless, efficient kitchen waste degradation can be accomplished in both SPS and TPS at an OLR of <20 gCODcr/(l.d), even though TPS may be more stable and easier to maintain. Bacillus coagulans predominated with an occupied ratio of approximately 90% in the acid fermentation reactor of TPS, and then a richer microbial community with a higher Shannon index value was maintained in the methane fermentation reactor of TPS than in the SPS reactor. 相似文献
122.
Design of a photocatalyst for bromate decomposition: surface modification of TiO2 by pseudo-boehmite
The rate of BrO3- reduction by a commercial TiO2 photocatalyst under UV illumination in an aqueous solution was increased by lowering the pH from 7 to 5. The effect is attributable to an enhancement of the electrical interaction between BrO3- and the positively charged surfaces of the TiO2 photocatalyst. The surface charge can be controlled by a surface modification of the TiO2 photocatalyst without controlling the pH of the water. In fact, the isoelectric point of surface-modified TiO2 was higher than that of the unloaded TiO2 photocatalyst, resulting in an increase in the rate of the photocatalytic reduction of BrO3- at a neutral pH. This increase is explained by an increase in the amount of adsorbed BrO3- on the photocatalyst surface. 相似文献
123.
Samad Ahadian Hiroshi Mizuseki Yoshiyuki Kawazoe 《Microfluidics and nanofluidics》2010,9(2-3):319-328
A new methodology, namely, artificial neural network (ANN) approach was proposed for modeling and predicting flow behavior of the polyethylene melt through nanochannels of nanoporous alumina templates. Wetting length of the nanochannels was determined to be a function of time, temperature, diameter of nanochannels, and surface properties of the inner wall of the nanochannels. An ANN was designed to forecast the relationship between the length of wetting as output parameter and other aforementioned parameters as input variables. It was demonstrated that the ANN method is capable of modeling this phenomenon with high accuracy. The designed ANN was then employed to obtain the wetting length of the nanochannels for those cases, which were not reported by the wetting experiments. The results were then analyzed statistically to identify the effect of each independent variable, namely, time, temperature, diameter of nanochannels, and surface properties of the inner wall of nanochannels as well as their combinations on the wetting length of the nanochannels. Interesting results were attained and discussed. 相似文献
124.
Kazunori Komatani Shinichi Ueno Tatsuya Kawahara Hiroshi G. Okuno 《User Modeling and User-Adapted Interaction》2005,15(1-2):169-183
We address the issue of appropriate user modeling to generate cooperative responses to users in spoken dialogue systems. Unlike
previous studies that have focused on a user’s knowledge, we propose more generalized modeling. We specifically set up three
dimensions for user models: the skill level in use of the system, the knowledge level about the target domain, and the degree of urgency. Moreover, the models are automatically derived by decision tree learning using actual dialogue data collected by the system.
We obtained reasonable accuracy in classification for all dimensions. Dialogue strategies based on user modeling were implemented
on the Kyoto City Bus Information System that was developed at our laboratory. Experimental evaluations revealed that the
cooperative responses adapted to each subject type served as good guides for novices without increasing the duration dialogue
lasted for skilled users. 相似文献
125.
Highly transparent cellulose hydrogels with physical crosslinkage were prepared from nonaqueous organic cellulose solutions and viscose by coagulating and regenerating cellulose in an aqueous solution containing a water‐miscible organic solvent. Nonaqueous organic cellulose solutions used were LiCl/dimethylacetamide, paraformaldehyde/dimethyl sulfoxide, and triethylammonium chloride/dimethyl sulfoxide. Preparation conditions and physical properties of the transparent cellulose hydrogels were studied. The transparency of the cellulose hydrogels depended on the composition of the aqueous solution containing the organic solvent. Furthermore, transparent cellulose hydrogels from viscose showed high tensile strength. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3020–3025, 2003 相似文献
126.
Guozhang Wu Kun Zhang Kiyoji Takagi Hironari Sano Hiroshi Yui 《Polymer International》2016,65(1):102-108
The effects of morphological changes on the thermal expansion, toughness and heat resistance of polyamide‐6 (PA)/styrene–ethylene–butylene–styrene (SEBS)/polyphenylene ether (PPE) blends were investigated. Compared with the typical ‘sea (PA matrix)–island (PPE domain)–lake (SEBS in PPE domain)’ morphology, an injection‐molded ternary blend with a preferential distribution of SEBS component at the interface between PA and PPE exhibited a low coefficient of linear thermal expansion (CLTE) in the flow direction. This low CLTE was ascribed to the deformation of SEBS and PA into a co‐continuous microlayer network structure during injection molding. Consequently, the expansion preferentially occurred towards the thickness direction. Further CLTE reduction either by a change in PA viscosity or by the selective location of an inorganic filler was examined, and its influences on impact strength and heat resistance are discussed based on transmission electron microscopy observations. © 2015 Society of Chemical Industry 相似文献
127.
The reductive removal of nitric oxide from flue gases by reaction with polyacrylonitrile-based active carbon fibres (PAN-ACF) activated with sulphuric acid has been studied at 423–632 K, using a circulating flow reactor. Nitric oxide (0.67 mmol) was completely removed via reduction with 1 g activated carbon under optimum conditions in 210 and 60 min at 423 and 623 K, respectively. N2 was formed as NO was removed. Some oxygen remained on the carbon surface at 423 K, but was desorbed as CO or CO2 on subsequent heating to 623 K. The bimolecular reaction of NO reduction over PAN-ACF, and the possible active sites of oxygen surface groups are discussed in the light of a kinetic study and a comparison of the fibre activation at different temperatures. 相似文献
128.
Tsuyoshi Hagio Kazuo Kobayashi Hisayoshi Yoshida Hiroaki Yasunaga Hiroshi Nishikawa 《Journal of the American Ceramic Society》1989,72(8):1482-1484
Pressureless sintering of hexagonal boron nitride (BN) was performed using a powder activated by mechano-chemical treatments. Physical properties of the sintered BN bodies depend on the type of starting powder and the conditions of the treatments. The BN body, which was obtained at 2000°C using an appropriate activated powder, was 99 wt% pure and was excellent in mechanical and physical properties, in spite of its low density (1.64 g/cm3 ). 相似文献
129.
Hajime Miyama Kouichi Tanaka Yoshio Nosaka Nobuyuki Fujii Hiroshi Tanzawa Shoji Nagaoka 《应用聚合物科学杂志》1988,36(4):925-933
Polyacrylonitrile-g-poly(N,N-dimethylaminoethyl methacrylate) was synthesized photochemically and quaternized. The positively charged membranes made from the quaternized graftcopolymer showed high ultrafiltration rate for water by adding poly(vinyl alcohol) to casting solution and washing it out after the casting. In buffered saline solution, the permeability of the membranes was very small at pH below isoelectric point of albumin but increased markedly at higher pH. On the other hand, the permeability for γ-globulin was very small and did not show any pH dependence. 相似文献
130.
Melting temperature of a film biaxially stretched in one step in air at 152 or 140°C increases with increase of vA, whereas heat of fusion and density decrease with increase of vA, where vA is the degree of stretching in area. The rapid decrease in density occurs for vA > 10. Extrapolation of the plot of the density versus vA?1/2 gives a value of 0.870 g/cm3 at infinite vA, which has been reported as the amorphous density of isotactic polypropylene by Farrow. This is so because the fine structure of the film becomes more and more amorphous with further stretching and reaches completely amorphous state at infinite vA. The temperature of stretching has a strong effect on the thermal behavior of a film; a low stretching temperature (140°C) brings about lower melting temperature, heat of fusion, and density. Crystallinity after melt press has not so large an effect on the melting behavior as the stretching temperature. Melting temperature and the shape of the thermogram also depend on the heating rate. There is an appropriate heating rate depending on vA which gives the minimum melting temperature. With stretched samples, a small side peak or a shoulder appears at a relatively low temperature in the thermogram when a high heating rate is used. 相似文献