全文获取类型
收费全文 | 3869篇 |
免费 | 204篇 |
国内免费 | 36篇 |
专业分类
电工技术 | 60篇 |
综合类 | 67篇 |
化学工业 | 834篇 |
金属工艺 | 166篇 |
机械仪表 | 155篇 |
建筑科学 | 202篇 |
矿业工程 | 42篇 |
能源动力 | 250篇 |
轻工业 | 549篇 |
水利工程 | 24篇 |
石油天然气 | 38篇 |
武器工业 | 2篇 |
无线电 | 210篇 |
一般工业技术 | 576篇 |
冶金工业 | 349篇 |
原子能技术 | 48篇 |
自动化技术 | 537篇 |
出版年
2024年 | 20篇 |
2023年 | 43篇 |
2022年 | 76篇 |
2021年 | 108篇 |
2020年 | 136篇 |
2019年 | 119篇 |
2018年 | 166篇 |
2017年 | 148篇 |
2016年 | 175篇 |
2015年 | 103篇 |
2014年 | 171篇 |
2013年 | 391篇 |
2012年 | 207篇 |
2011年 | 216篇 |
2010年 | 180篇 |
2009年 | 224篇 |
2008年 | 178篇 |
2007年 | 162篇 |
2006年 | 130篇 |
2005年 | 83篇 |
2004年 | 95篇 |
2003年 | 119篇 |
2002年 | 162篇 |
2001年 | 125篇 |
2000年 | 65篇 |
1999年 | 55篇 |
1998年 | 131篇 |
1997年 | 69篇 |
1996年 | 52篇 |
1995年 | 28篇 |
1994年 | 28篇 |
1993年 | 15篇 |
1992年 | 10篇 |
1991年 | 16篇 |
1990年 | 11篇 |
1989年 | 10篇 |
1988年 | 6篇 |
1987年 | 7篇 |
1986年 | 8篇 |
1985年 | 11篇 |
1984年 | 7篇 |
1983年 | 11篇 |
1982年 | 4篇 |
1980年 | 3篇 |
1979年 | 3篇 |
1978年 | 4篇 |
1976年 | 6篇 |
1974年 | 2篇 |
1973年 | 2篇 |
1965年 | 3篇 |
排序方式: 共有4109条查询结果,搜索用时 15 毫秒
101.
This study focuses on the fabrication of poly(vinyl alcohol)/ poly(vinyl pyrrolidone)-Iodine nanofibers via electrospinning. Electrospun fibers were characterized by FT-IR, DSC and SEM techniques. DSC results indicated that the thermal stability of nanofibers were improved after the addition of chitosan and poloxamer 188. SEM images showed that the spongiform structure is much more compact and fibrous in the case of added chitosan, with an average fiber diameter of 374 nm, whereas the addition of poloxamer 188 resulted in a more porous and beaded composition, with average fiber diameter of 489 nm. 相似文献
102.
Demet Aydınoğlu Özkan Akgül Vildan Bayram 《Polymer-Plastics Technology and Engineering》2013,52(16):1706-1722
Polacrylamide nanocomposite hydrogels were prepared by in situ free radical polymerization reaction in presence of Spirulina microalgae, which is immobilized in montmorillonite clay (Sp-MMT). The nanocomposite hydrogel having 1 wt.% Sp-MMT clay was found to have desired exfoliated structure, maximum swelling and improved thermal stability. It also showed maximum metal adsorption capacity, which is about 312% higher than that of neat PAAm hydrogel at the highest metal concentration. The presence of Spirulina's porous network structure where all potential binding sites are under receptive position was found to be responsible for the dramatic increase in the metal adsorption and swelling behavior. 相似文献
103.
Duygu Tuncer Çiğdem Çelik Sevi Burçak Çehreli Neslihan Arhun 《Journal of Adhesion Science and Technology》2013,27(13):1288-1297
Aim: The aim was to compare the microleakage of resin composite bonded with different adhesive systems in class-II cavities at enamel or dentine margins. Material and methods: 60 extracted human molar teeth received slot cavity preparations on mesial and distal surfaces (mesial cervical margin was prepared in enamel and distal in dentine). They were randomly divided into five groups (n?=?12) according to the adhesive system: Group-A: Silorane Bond (S), Group-B: Adper Single Bond 2 (SB), Group-C: Clearfil SE Bond (CSE), Group-D: Single Bond Universal (USel) (selective etch-and-rinse), Group-E: Single Bond Universal (USE) (all-in-one). The preparations were restored using the same resin composite (Filtek Ultimate) except Group A which was restored by Silorane composite. The teeth were thermocycled, immersed in dye, sectioned, and dye penetration was evaluated quantitatively using image analysis. The data were analyzed using the two-way analysis of variance and Bonferroni test. Results: In all groups, there was no statistically significant difference between enamel margins at occlusal and gingival sites (p?>?0.05). The statistical difference between Group-A (S) and Group-B (SB) was significant at all margins. Group-B (SB) presented the greatest microleakage amounts at all margins and the highest scores were obtained in the dentine. Likewise, SB demonstrated statistically significant differences between dentine and enamel margins (occlusal and gingival)(p?<?0.05). Conclusion: All adhesive systems showed similar microleakage values between enamel margins in occlusal and gingival regions. However, when the gingival margin is located in the dentine, etch&rinse adhesive systems may not be a choice in terms of microleakage prevention. 相似文献
104.
Mehmet Uysal Ramazan Karslioğlu Ahmet Alp Hatem Akbulut 《Ceramics International》2013,39(5):5485-5493
Core–shell nanostructured Ni-coated Al2O3 composite powders were synthesised by using the electroless plating method. The influence of the chemical components and powder concentration in the Ni coating was investigated by scanning electron microscopy, energy dispersive spectroscopy, and X-ray diffraction techniques. The results show that the concentration of the plating components plays an important role in the formation of core–shell Al2O3/Ni composite powders. The nickel content in the composite powders could be effectively controlled by adjusting the nickel chloride content and the concentration of NaH2PO2·H2O in the plating solution. The nanostructure of the crystalline Ni coatings was observed to be very attractive for achieving good bonding between ceramic particles and matrices for composite production. 相似文献
105.
H. Erdem Çamurlu Ahmet Gençer Burcu Becer Şükrü Özdoğan 《Ceramics International》2013,39(8):8589-8595
Effect of potassium carbonate addition on the carbothermic formation of hexagonal boron nitride (hBN) was investigated by keeping the K2CO3 added B2O3+C mixtures in nitrogen atmosphere at 1400 °C for 40–160 min. K2CO3 amount was varied in the range of 10–60 wt% of the B2O3+C mixture. Products were subjected to XRD and quantitative analyses, SEM and TEM observations, and particle size measurement. Amount of hBN increased considerably with K2CO3 addition; also particle size and crystallinity improved. Catalytic role of K2CO3 was suggested as forming a potassium borate melt in which hBN particles form, in addition to carbothermic formation reaction. Effect of K2CO3 on increasing the hBN amount decreased when it was used over 40%. This was attributed to the rapid evaporation of the formed potassium borate liquid. 相似文献
106.
Vedat Sarıboğa Hasan Özdemir M.A. Faruk Öksüzömer 《Journal of the European Ceramic Society》2013,33(8):1435-1446
La0.8Sr0.2Ga0.83Mg0.17O2.815 (LSGM) materials are synthesized with a fast and facile cellulose templating method for the first time and characterized by XRD, EIS, Archimedes method and SEM–EDS. LSGM powders with a phase purity of 91.7 mol% are obtained after the calcination at 1300 °C for 12 h. SEM–EDS results indicate possible decomposition and reconstruction of the LSGM phase due to the diffusion of Sr-rich species to the grain boundaries for the sample sintered at 1500 °C for 6 h. Maximum conductivity value is found to be 4.2 × 10?2 S cm?1 at 800 °C for the sample calcined at 1300 °C for 12 h and sintered at 1400 °C for 6 h. Phase purity, stability and relative density are the important factors for obtaining high performance LSGM electrolytes. Therefore, cellulose templating method is a promising candidate for the preparation of LSGM electrolytes. 相似文献
107.
108.
Hakan Demiral ?lknur DemiralBelgin Karabacako?lu Fatma Tümsek 《Chemical Engineering Research and Design》2011,89(2):206-213
Activated carbons were produced from olive bagasse and their characteristics were investigated. Olive bagasse was first carbonized at 500 °C in N2 atmosphere. Then, the obtained chars were activated with steam. The effects of activation temperature and duration were examined. The resultant activated carbons were characterized by measuring their porosities and pore size distributions. The activated carbons produced had the BET surface areas ranging from 523 to 1106 m2/g. The total pore volume was increased from 0.2981 to 0.6067 cm3/g. Adsorption capacity was demonstrated by the iodine numbers. The surface chemical characteristics of activated carbons were determined by FTIR spectroscopic method and Boehm's titration method. The microstructure of the activated carbons prepared was examined by scanning electron microscopy (SEM). The experimental data was proved that the properties of activated carbons depend on the final temperature of the process and duration of treatment at the final temperature. 相似文献
109.
Derya Koçak Hasene Keskin Sibel Fadıloğlu Boleslaw Kowalski Fahrettin Göğüş 《Journal of the American Oil Chemists' Society》2011,88(10):1531-1538
Characterization of the fatty acid and triacylglycerol composition of terebinth fruit oil and the synthesis of structured
lipids (SL) were performed in this study. Interesterification reaction of terebinth fruits oil (Pistacia terebinthus L.) with caprylic acid (CA) and stearic acid (SA) to produce a SL was performed in n-hexane using immobilized sn-1,3 specific lipase from Mucor miehei. The effect of reaction conditions and relationship among them were analyzed by response surface methodology (RSM) with a
four-factors five-level central composite rotatable experimental design. The four major factors chosen were enzyme load (10–30 wt%
based on substrates), reaction time (7–18 h), reaction temperature (40–60 °C) and substrate mole ratio (terebinth oil:SA:CA
1:1:1–1:1:3). The best fitting quadratic model was determined by regression and backward elimination. Based on the fitted
model, the optimal reaction conditions for the incorporation of CA and SA were found to be temperature 50 °C; time 18 h; enzyme
load 30 wt%; substrate ratio 1:1:3. Under these optimum conditions, the incorporation of SA and CA could be obtained as 19
and 14%, respectively. 相似文献
110.
Selective CO oxidation over promoted Au/γ-Al2O3 catalysts in the presence of CO2 and H2O in the feed
Tuğba Davran-Candan Sadi T. TezcanlıRamazan Yıldırım 《Catalysis communications》2011,12(12):1149-1152
In this work, the effect of promoter type (Mg, Mn, Ce, Co, Fe and Ni) on selective CO oxidation performance of Au/γ-Al2O3 was studied with the realistic feed stream containing CO2 and H2O. The effects of Au loading, promoter loading, reaction temperature and the feed composition were also investigated. It was found that MgO was the best promoter in the presence of CO2 and H2O, and 1.25 wt.% Mg was sufficient for promotion. The CO conversion decreased with the addition of CO2 while the presence of H2O had some positive effects. 相似文献