全文获取类型
收费全文 | 83368篇 |
免费 | 10238篇 |
国内免费 | 2632篇 |
专业分类
电工技术 | 2810篇 |
综合类 | 11131篇 |
化学工业 | 12657篇 |
金属工艺 | 4702篇 |
机械仪表 | 2311篇 |
建筑科学 | 30022篇 |
矿业工程 | 1975篇 |
能源动力 | 1036篇 |
轻工业 | 1907篇 |
水利工程 | 5570篇 |
石油天然气 | 2061篇 |
武器工业 | 513篇 |
无线电 | 2380篇 |
一般工业技术 | 5574篇 |
冶金工业 | 2536篇 |
原子能技术 | 324篇 |
自动化技术 | 8729篇 |
出版年
2024年 | 72篇 |
2023年 | 642篇 |
2022年 | 1642篇 |
2021年 | 1844篇 |
2020年 | 1805篇 |
2019年 | 1505篇 |
2018年 | 1797篇 |
2017年 | 2098篇 |
2016年 | 2226篇 |
2015年 | 2493篇 |
2014年 | 7724篇 |
2013年 | 5373篇 |
2012年 | 7831篇 |
2011年 | 8502篇 |
2010年 | 7037篇 |
2009年 | 7335篇 |
2008年 | 5181篇 |
2007年 | 5540篇 |
2006年 | 4701篇 |
2005年 | 4024篇 |
2004年 | 3214篇 |
2003年 | 2755篇 |
2002年 | 2384篇 |
2001年 | 1921篇 |
2000年 | 1561篇 |
1999年 | 1165篇 |
1998年 | 822篇 |
1997年 | 665篇 |
1996年 | 525篇 |
1995年 | 400篇 |
1994年 | 365篇 |
1993年 | 261篇 |
1992年 | 190篇 |
1991年 | 152篇 |
1990年 | 125篇 |
1989年 | 81篇 |
1988年 | 57篇 |
1987年 | 53篇 |
1986年 | 15篇 |
1985年 | 20篇 |
1984年 | 22篇 |
1983年 | 20篇 |
1982年 | 28篇 |
1981年 | 10篇 |
1980年 | 29篇 |
1979年 | 7篇 |
1975年 | 2篇 |
1972年 | 2篇 |
1962年 | 2篇 |
1951年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 39 毫秒
1.
当前,我国水泥工业在可燃废弃物应用技术方面都还处于一家一户、自制自用、效率极低的初级阶段。发达国家的替代燃料:“垃圾衍生燃料”RDF、“固体回收燃料”SRF、“次煤”Subcoal和“纸塑垃圾衍生燃料”RPF制成的原材料都是可燃废弃物,只是处理工艺技术不同或者由垃圾中分拣出的可燃废弃物不同,制成颗粒状衍生燃料的品质不同,这些都可以替代部分甚或替代全部化石燃料在水泥窑炉中应用。我国大力发展“替代燃料”产业,有助于水泥工业消纳更多的“可燃废弃物”,为改善环境尤其是城镇环境和面貌,为我国的节能减排和绿色高质量发展发挥更大的作用。 相似文献
2.
Alessio Zandona Bernd Rüdinger Joachim Deubener 《Journal of the American Ceramic Society》2021,104(2):1146-1155
Glass powder samples of cordierite composition (doped with 8 mol% TiO2) were heat-treated to produce a series of increasingly SiO2-enriched Mg-bearing quartz solid solutions (Qss). The obtained materials were then analyzed by X-ray diffraction: Rietveld structural refinements revealed that Mg-bearing Qss phases possess trigonal symmetry and a compositionally dependent intermediate structural arrangement between those of low and high quartz. High-temperature diffraction measurements were performed up to 700°C to characterize the thermal expansion behavior of the crystals. At SiO2-rich compositions, a reversible high-to-intermediate inversion of the quartz structure is observed, which shifts with increasing stuffing to lower temperatures than the conventional 573°C for pure quartz. Similarities and differences to the better-established Li-bearing Qss are discussed in the text. 相似文献
3.
4.
利用水泥窑协同处置污染物可以缓解现阶段的环保压力,且具有良好的社会效益、环保效益及经济效益。文中以水泥窑协同处置为研究对象,探究其在我国的发展历程,并对其未来发展进行展望。 相似文献
5.
A superhydrophobic ceria-based composite coating is developed to improve anticorrosion properties of AZ61 magnesium alloy, fabricating via chemical conversion method followed by hydrothermal treatment. The cerium conversion coating has a block structure with microcracks. After the hydrothermal treatment, a dense CeO2 layer, porous CeO2 nanorods, and stearic absorbing layers are grown stepwise on the conversion coating. And the composite coating is hydrophobic or even superhydrophobic and has almost no microcracks. As the hydrothermal reaction time increases, the water contact angle of the composite coating first increases and then decreases, and it reaches the maximum value of 152° after hydrothermal treatment for 4 h. Both the dense CeO2 layer and the superhydrophobic stearic absorbing layer can effectively prevent the electrolyte from contacting the substrate; the corrosion current density of the superhydrophobic composite coating is lower than that of the hydrophilic composite coating and the cerium conversion coating, and has the best corrosion resistance. 相似文献
6.
7.
8.
Wafaa Mohamed SHABAN Khalid ELBAZ Mohamed AMIN Ayat gamal ASHOUR 《Frontiers of Structural and Civil Engineering》2022,16(3):329
This study presents a new systematic algorithm to optimize the durability of reinforced recycled aggregate concrete. The proposed algorithm integrates machine learning with a new version of the firefly algorithm called chaotic based firefly algorithm (CFA) to evolve a rational and efficient predictive model. The CFA optimizer is augmented with chaotic maps and Lévy flight to improve the firefly performance in forecasting the chloride penetrability of strengthened recycled aggregate concrete (RAC). A comprehensive and credible database of distinctive chloride migration coefficient results is used to establish the developed algorithm. A dataset composite of nine effective parameters, including concrete components and fundamental characteristics of recycled aggregate (RA), is used as input to predict the migration coefficient of strengthened RAC as output. k-fold cross validation algorithm is utilized to validate the hybrid algorithm. Three numerical benchmark analyses are applied to prove the superiority and applicability of the CFA algorithm in predicting chloride penetrability. Results show that the developed CFA approach significantly outperforms the firefly algorithm on almost tested functions and demonstrates powerful prediction. In addition, the proposed strategy can be an active tool to recognize the contradictions in the experimental results and can be especially beneficial for assessing the chloride resistance of RAC. 相似文献
9.
Izhar AHMAD Kashif Ali KHAN Tahir AHMAD Muhammad ALAM Muhammad Tariq BASHIR 《Frontiers of Structural and Civil Engineering》2022,16(5):589
In recent building practice, rapid construction is one of the principal requisites. Furthermore, in designing concrete structures, compressive strength is the most significant of all parameters. While 3-d and 7-d compressive strength reflects the strengths at early phases, the ultimate strength is paramount. An effort has been made in this study to develop mathematical models for predicting compressive strength of concrete incorporating ethylene vinyl acetate (EVA) at the later phases. Kolmogorov-Smirnov (KS) goodness-of-fit test was used to examine distribution of the data. The compressive strength of EVA-modified concrete was studied by incorporating various concentrations of EVA as an admixture and by testing at ages of 28, 56, 90, 120, 210, and 365 d. An accelerated compressive strength at 3.5 hours was considered as a reference strength on the basis of which all the specified strengths were predicted by means of linear regression fit. Based on the results of KS goodness-of-fit test, it was concluded that KS test statistics value (D) in each case was lower than the critical value 0.521 for a significance level of 0.05, which demonstrated that the data was normally distributed. Based on the results of compressive strength test, it was concluded that the strength of EVA-modified specimens increased at all ages and the optimum dosage of EVA was achieved at 16% concentration. Furthermore, it was concluded that predicted compressive strength values lies within a 6% difference from the actual strength values for all the mixes, which indicates the practicability of the regression equations. This research work may help in understanding the role of EVA as a viable material in polymer-based cement composites. 相似文献
10.
《Ceramics International》2022,48(22):33361-33372
Calcium phosphate cements (CPCs) have been increasingly used as synthetic bone substitutes for repair and regeneration of bone defects given their biocompatibility, resemblance to bone and malleability. Moreover, their use as local antibiotic delivery systems is of main interest against bone infections, avoiding the adverse effects of high dosages of conventional therapy. The main goals of this work were to improve the properties of a commercial CPC (Neocement®), turning it injectable, and to provide it with a new functionality as a drug delivery system able to ensure a sustained release of an antibiotic commonly used in orthopaedics (gentamicin sulphate, GS). For this, the influence of the liquid phase amount (%LP) and type of polymer contained in the formulation (chitosan, Chi, or hydroxypropyl methylcellulose, HPMC) on the basic properties of the material was evaluated. It was found that the formulation containing 42%LP + HPMC+1.87% wt GS was the best one. It showed suitable setting and mechanical properties, and injectability around 87% (much superior to the original Neocement®, with 31%). It ensured a sustained release of GS for at least 14 days, at antibacterial levels. The antibiotic released is highly effective against S. epidermidis, but also presents some antibacterial activity against S. aureus. The CPC revealed to be non-cytotoxic. Moreover, it demonstrated good flowability and connectivity with human cadaveric trabecular bone. 相似文献