全文获取类型
收费全文 | 1630篇 |
免费 | 116篇 |
国内免费 | 27篇 |
专业分类
电工技术 | 11篇 |
综合类 | 71篇 |
化学工业 | 201篇 |
金属工艺 | 13篇 |
机械仪表 | 39篇 |
建筑科学 | 117篇 |
矿业工程 | 763篇 |
能源动力 | 34篇 |
轻工业 | 137篇 |
水利工程 | 7篇 |
石油天然气 | 43篇 |
无线电 | 11篇 |
一般工业技术 | 67篇 |
冶金工业 | 124篇 |
原子能技术 | 12篇 |
自动化技术 | 123篇 |
出版年
2023年 | 7篇 |
2022年 | 30篇 |
2021年 | 26篇 |
2020年 | 51篇 |
2019年 | 26篇 |
2018年 | 37篇 |
2017年 | 30篇 |
2016年 | 62篇 |
2015年 | 60篇 |
2014年 | 66篇 |
2013年 | 80篇 |
2012年 | 65篇 |
2011年 | 136篇 |
2010年 | 82篇 |
2009年 | 89篇 |
2008年 | 73篇 |
2007年 | 103篇 |
2006年 | 104篇 |
2005年 | 89篇 |
2004年 | 81篇 |
2003年 | 81篇 |
2002年 | 36篇 |
2001年 | 42篇 |
2000年 | 48篇 |
1999年 | 45篇 |
1998年 | 51篇 |
1997年 | 30篇 |
1996年 | 24篇 |
1995年 | 21篇 |
1994年 | 14篇 |
1993年 | 23篇 |
1992年 | 17篇 |
1991年 | 9篇 |
1990年 | 2篇 |
1989年 | 1篇 |
1988年 | 10篇 |
1987年 | 7篇 |
1986年 | 1篇 |
1985年 | 2篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1979年 | 2篇 |
1978年 | 1篇 |
1977年 | 3篇 |
1976年 | 3篇 |
1956年 | 1篇 |
排序方式: 共有1773条查询结果,搜索用时 31 毫秒
1.
《中国稀土学报(英文版)》2022,40(7):1134-1147
In this study, the Bayan Obo rare earth concentrates mixed with Na2CO3 were used for roasting research. The phase change process of each firing stage was analyzed. The kinetic mechanism model of the continuous heating process was calculated. This study aims to recover valuable elements and optimize the production process to provide a certain theoretical basis. Using X-ray diffraction (XRD), Fourier infrared spectroscopy, scanning electron microscopy with energy dispersive spectrometry, the reaction process and the existence of mineral phases were analyzed. The variable temperature XRD and thermogravimetric method were used to calculate the roasting kinetics. The phase transition results show that carbonate-like substances first decompose into fine mineral particles, and CaO, MgO, and SiO2 react to form silicates, causing hardening. Further, REPO4 and NaF can directly generate CeF3 and CeF4 at high temperatures, and a part of CeF4 and NaF forms a solid solution substance Na3CeF7. Rare earth oxides calcined at a high temperature of 750 °C were separated to produce Ce0.6Nd0.4O1.8, Ce4O7, and LaPrO3+x. Then, BaSO4, Na2CO3, and Fe2O3 react to form barium ferrite BaFe12O19; the kinetic calculation results show that during the continuous heating process, the apparent activation energy E reaches the minimum in the entire reaction stage in the temperature range of 440–524 °C, and the reaction order n reaches the maximum, which indicates that the decomposition product REFO significantly impacts the reaction system and reduces the activation energy. The mechanism function is F(α) = [?ln (1?α)]1/3. The reaction order n reaches the minimum in the temperature range of 680–757 °C, and the apparent activation energy E is large. The difficulty of the reaction increases during the final stage. The reaction mechanism function is F(α) = [1?(1?α)1/3]2. Observing the entire reaction stage, the step of controlling the reaction rate changes from random nucleation to three-dimensional diffusion (spherical symmetry). 相似文献
2.
3.
《能源学会志》2020,93(2):642-648
The change of mineral composition in ash and the effect of CaO on the melting characteristics of coal ash were studied by adding different contents of CaO to coal ash. At the same time, the Factsage thermodynamics software was used to simulate the mineral changes in the synthetic ash to support and verify the experimental results. The results show that with the increase of CaO content, the melting characteristic temperature of coal ash first decreases and then rises. After adding a certain amount of CaO, the quartz with higher melting point completely disappears, and the melting point of the coal ash reaches a minimum value. And with the increase of CaO content, the appearance of wollastonite and single crystal calcium oxide mineral makes the melting point of coal ash gradually increase. It can be seen from the phase diagram calculated by Factsage that as the CaO content increases, the corresponding position of the coal ash gradually moves from the hematite region to the calcareous region. And the phenomenon of low temperature eutectic occurs when the CaO content is 35%, which is consistent with the trend of temperature change of the melting characteristics. These phenomena all indicate that the change in the melting point of coal ash is nonlinear as the content of CaO minerals increases. 相似文献
4.
Gang Gao Wei-Wei Zhang Guo-Fu M Guo Chen Tao Li Ling-Zhi Hu Zhi-Ming Yang Jian-Guo Wang Jun Yang 《石油科学(英文版)》2018,15(1):51-67
The Lower Cretaceous Xiagou Formation contains the major source rocks for the crude oils discovered in the Qingxi Sag and the South Uplift in the Jiuquan Basin, northwestern China. The Xiagou Formation source rock was formed in a closed, anoxic, reducing, alkaline lacustrine environment with a high salinity. Its high content of brittle minerals is favorable for the fracturing of reservoirs in source rock formations in the Qingxi Sag. The Xiagou Formation contains a great number of fair to excellent source rocks, and their organic matter (OM) came chiefly from plankton/algae and high plants as well as possibly bacterial organisms. The Xiagou Formation source rocks mainly contain Type II OM and some Type III and Type I OM, with good oil-generating potential. The source rock maturity is mainly in the early-mature and mature stages, and its Ro value corresponding to oil peak is about 0.8%, which is lower than classic oil peak Ro value of 1.0%; therefore, a great deal of hydrocarbon was generated before the classic oil peak Ro = 1.0%. Mature source rock in the Xiagou Formation tends to be distributed in the older members and at a greater depth. There is a better exploration potential of tight oil in the deep Qingxi Sag. 相似文献
5.
6.
Marcos Antônio Klunk Nattan Roberto Caetano Rommulo Vieira Conceição Paulo Roberto Wander Sudipta Dasgupta 《The International journal of environmental studies》2020,77(3):492-509
ABSTRACT Several Carbon Capture and Storage (CCS) techniques have been studied including injections of carbon dioxide (CO2) into the mature and/or depleted hydrocarbon reservoirs and deep saline aquifers. This work aims to test storing CO2 into the magnesium-rich evaporite strata and also into the stratigraphic intervals containing Mg-rich brines. The test simulates Mg-carbonation of the synthetic solution obtained from the Mg-evaporite mineral, bischofite – both experimentally in the laboratory condition and also through computerised geochemical simulation. The laboratory experiments, which resulted in the crystallisation of anhydrous magnesite, were analysed. The TOUGHREACTTM, Geochemist’s WorkbenchTM (GWB) and PHREEQCTM software simulated the experiments as computerised geochemical model and tested the results for natural geological conditions. The geochemical simulations successfully demonstrate the immense CCS potential for the Mg-evaporite (as well as the sedimentary strata charged with Mg-evaporitic brine) at their subsurface geological occurrences at elevated pressure-temperature and high salinity. 相似文献
7.
矿物的单体解离是其能被高效选别的关键因素之一,粉碎方法对矿物单体解离度有很大的影响。白云鄂博稀土矿含十几种稀土矿物,矿物共生密切,嵌布类型复杂,其中稀土主要富集在氟碳铈矿与独居石矿中。分析表明矿物因相互包裹穿插和交代而形成毗连、网脉、溶蚀和环状嵌布。为提高矿物的单体解离度,通过自主研发水射流矿物解离装置,探究了水射流速度对白云鄂博矿稀土单体解离度的影响。在同等粒度分布下,对高压水射流粉碎与常规球磨(铁介质)实验结果进行了对比,分析了两种粉碎方式对稀土矿物解离状态及颗粒界面的影响。激光共聚焦显微镜、矿物特征自动定量分析系统(AMICS)分析表明,高压水射流粉碎白云鄂博稀土矿物单体解离度优于球磨,具有解离度高、粒度相对均匀等特点;矿物颗粒天然界面保持较好、表面较光洁,稀土矿物集中在0.038 mm以下颗粒中,有益于稀土的浮选分离,对白云鄂博矿的矿石粉碎具有一定的指导意义。 相似文献
8.
《Ceramics International》2022,48(22):32867-32876
Herein, Factsage software and sintering experiment were conducted to predict and correlate thermodynamic calculations of Fe in a synthetic solid waste and the expansion behavior of ceramsite. With the increase of Fe2O3 content, the liquid phase content and viscosity in the multi-component system gradually decreased and the melting temperature range became wider. This can match with the generation of the liquid phase with proper viscosity in the ceramsite and the full expansion properties. At 400–1000 °C, iron as a network former was tetrahedrally coordinated with oxygen to form Hercynite (Al2FeO4) phase; at 1180–1200 °C, iron as a network modifier dissolved into the silicate mineral structure to form the eutectic composition of Diopside (Ca4Mg3.62Fe0.78Si7.6O24) and Ferrosolite (Si16Mg5.09Fe10.66Ca0.26O48). The formation of iron-bearing silicate facilitated the generation of the viscous layer, so that the outer layer of the ceramsite exhibited sealing performance. Finally, a preferable porous ceramsite with compressive strength of 10.7 MPa and an apparent density of 708 kg/m3 was obtained. This study analyzes the effect of Fe2O3 on the expansion behavior of porous ceramsite and provides new insight into how to analyze different solid wastes to produce ceramsite in a predictable way. 相似文献
9.
Noushin Mohammadifard Carolyn Gotay Karin H. Humphries Andrew Ignaszewski Ahmad Esmaillzadeh 《Critical reviews in food science and nutrition》2019,59(15):2375-2385
ABSTRACTAppropriate intake of micronutrient, such as electrolyte minerals is critical for the well-being of the cardiovascular health system. However, there are some debates regarding the impacts of dietary and/or supplemental intake of these minerals, on the risk of cardiovascular events and associated risk factors. High sodium intake is adversely associated with the risk of hypertension. Although many reports refered to the positive association of Na intake and cardiovascular events and all-cause mortality, however, other studies indicated that low Na intake is related to higher risk of all-cause mortality and HF-related events. By contrast, dietary potassium, magnesium and calcium have an inverse correlation with cardiovascular events and risk factors, especially with blood pressure. There are some controversies about cardiovascular effects and all-cause mortality of high Ca intake, including no effect, preventive or adverse effect with or without vitamin D. Calcium supplementation might be beneficial for prevention of cardiovascular events and all-cause mortality only in individuals with low intake. Moreover, calcium intake showed a J- or U-shaped association with the risk of cardiovascular diseases. Due to the controversies of the effect of electrolyte minerals especially sodium and calcium intake on cardiovascular events, large scale, well-designed long-term randomized clinical trials are required to evaluate the effect of minerals intake on cardiovascular events and all-cause mortality. In this review, we discuss the role of dietary and or supplemental sodium, potassium, magnesium, calcium, in cardiovascular health, as well as their clinical applications, benefits, and risks for the primary prevention of cardiovascular disease, in general population. 相似文献
10.
本文意在研究加拿大政府用于引导个人资金进入矿业初级勘探阶段的个人所得税优惠政策——可抵税流转股票及与其配套实施的矿产勘探税款抵减额度政策。分析其设计思路、实施方法,把握政策的目标和流程;通过案例分析,详细阐述其作用和实践效果。该项政策在加拿大已成功应用20余年,依然在持续有效地发挥着投资导向作用,使个人投资成为矿产初级勘探行业市场融资的重要渠道之一,对于缓解当前世界面临的矿业市场低迷引发的初级勘探阶段融资困难是行之有效的方法之一,对中国制定类似的财税政策具有启示作用。 相似文献