全文获取类型
收费全文 | 3394篇 |
免费 | 291篇 |
国内免费 | 278篇 |
专业分类
电工技术 | 7篇 |
综合类 | 194篇 |
化学工业 | 279篇 |
金属工艺 | 22篇 |
机械仪表 | 41篇 |
建筑科学 | 215篇 |
矿业工程 | 449篇 |
能源动力 | 88篇 |
轻工业 | 5篇 |
水利工程 | 75篇 |
石油天然气 | 2481篇 |
武器工业 | 4篇 |
无线电 | 6篇 |
一般工业技术 | 71篇 |
冶金工业 | 10篇 |
原子能技术 | 1篇 |
自动化技术 | 15篇 |
出版年
2024年 | 1篇 |
2023年 | 44篇 |
2022年 | 126篇 |
2021年 | 161篇 |
2020年 | 158篇 |
2019年 | 135篇 |
2018年 | 127篇 |
2017年 | 132篇 |
2016年 | 182篇 |
2015年 | 158篇 |
2014年 | 264篇 |
2013年 | 192篇 |
2012年 | 275篇 |
2011年 | 279篇 |
2010年 | 155篇 |
2009年 | 147篇 |
2008年 | 131篇 |
2007年 | 137篇 |
2006年 | 201篇 |
2005年 | 163篇 |
2004年 | 148篇 |
2003年 | 129篇 |
2002年 | 99篇 |
2001年 | 78篇 |
2000年 | 81篇 |
1999年 | 76篇 |
1998年 | 42篇 |
1997年 | 36篇 |
1996年 | 34篇 |
1995年 | 22篇 |
1994年 | 19篇 |
1993年 | 5篇 |
1992年 | 6篇 |
1991年 | 4篇 |
1990年 | 3篇 |
1989年 | 3篇 |
1985年 | 1篇 |
1984年 | 2篇 |
1981年 | 5篇 |
1980年 | 1篇 |
1977年 | 1篇 |
排序方式: 共有3963条查询结果,搜索用时 15 毫秒
1.
《中国有色金属学会会刊》2021,31(11):3530-3548
In-situ LA-ICP-MS and S isotopes of pyrite from the Baoshan Cu polymetallic deposit were conducted to investigate the ore-forming process and the enrichment mechanism of elements. Three generations of pyrite (Py I, Py II, and Py III) in the skarn-type ores and pyrite in the carbonate-hosted sulfide ores from central, western, and northern (C_Py, W_Py, and N_Py) mining districts are selected for comparison. Compared with Py I and Py III, the contents of most elements in Py II are apparently higher. The As and Se contents are high within a wide range and are decoupled in the growth band of the C_Py. The highest As, Se, and Pb contents were found in W_Py and N_Py. These results indicate the drastic changes in the temperature and fluid mixing during the mineralization. The occurrence of fluctuation and change in temperature and f(O2) was triggered by intermittent pulses of magmatic-hydrothermal fluids, mixing with meteoric water, and water−rock interactions. The sulfur isotopes of all species of pyrite indicated the magmatic source. The change in the f(O2) conditions caused slight differences in the sulfur isotope compositions. Consequently, a metallogenic model was proposed to explain the ore-forming processes. 相似文献
2.
3.
《International Journal of Hydrogen Energy》2019,44(11):5220-5229
At present, the proportion of tight oil in non-renewable hydrogen energy is increasing. According to an initial exploration and attemptable practice on the exploration of tight oil, it is found that the cost can be controlled effectively and positive effects are achieved. But this technique cannot make sure the proppants filled uniformly in the long fracture. Several researches on the proppants migration experiment devices and factors influencing on proppant setting are reviewed and a new set of experimental device to simulate the laws of proppants setting in long fracture is developed. This device can simulate the main factors influencing proppants setting performance. It analyzes several factors such as wall filtration, construction displacement, sand concentration, proppant size and density, viscosity of fracturing fluid is used to rank the influencing degree of every factor. Considering the effects of mutual interference between proppants, width of fracture, rough fracture surface and fracture surface filtration during the proppants setting progress, the mathematical model of proppant setting is modified by adding sand concentration correction factor, wall effect correction factor and filtration correction factor. The experimental data verify the accuracy of the settlement model is established using the data getting from experiment. 相似文献
4.
以宏景塔一矿回采工作面为研究对象,基于切顶卸压无煤柱自动成巷技术原理,采用数值模拟计算和现场实测的方法,对该矿成巷段巷道围岩支承压力分布及围岩变形规律进行分析。研究结果表明:随着工作面向前推进,巷道围岩支承压力呈先增大后减小最后趋于稳定的变化趋势,支承压力稳定值为13.5 MPa;受工作面回采动压的影响,距离工作面70 m以内,锚索受力急剧增大到恒阻值、巷道围岩变形明显;距离工作面70~150 m,锚索受力迅速减小、巷道围岩变形逐渐变缓;在距离工作面150 m之后,锚索受力仅有微量变化、巷道围岩变形趋于稳定。因此确定支护体回撤保守安全位置为工作面后方150 m。工程实践表明:所设支护体回撤距离能够应对巷道围岩变形,成巷效果良好。 相似文献
5.
针对赵固二矿煤层透气性低、钻孔有效影响半径小,实施定向长钻孔代替底板岩巷进行区域瓦斯治理期间钻孔工程量大、瓦斯抽采效果不理想的问题。结合煤层赋存特征及钻孔施工情况,采用定向长钻孔整体水力压裂增透技术,理论分析了合理坐封位置、压裂参数,完成200 m煤巷条带一次整体压裂,最大泵注压力24.3 MPa、累计注水量1 613 m3。并基于煤层全水分变化,考察确定了单个钻孔压裂影响范围达到巷道两帮30 m,有效改善了煤体储层特性,提高了煤层瓦斯抽采效率。在实现定向钻孔对预抽煤巷条带可靠控制的同时,最大程度降低了钻孔工程量、缩短了瓦斯治理周期,为实现矿区“以孔代巷”及高效安全开采提供了技术支撑。 相似文献
6.
7.
为了提高碎软煤层条带瓦斯抽采效率和效果,基于目前地面瓦斯抽采主要采用垂直井或从式井的方式抽采效果差、效率低的现状,通过理论和实验分析论证了穿岩层压裂改造煤储层的可行性,提出了在目标煤层顶板岩层中钻水平井,并通过垂直向下射孔以及采用泵送桥塞分段进行压裂的方式进行地面瓦斯抽采。试验结果表明:顶板分段压裂水平井单井产量高、高稳产期更长、产量衰减更慢;有效水平井段控制区域内瓦斯下降均匀,更有利于进行条带瓦斯抽采;相同投资条件下,采用水平井的方式瓦斯抽采效率和投入产出比更高。 相似文献
8.
9.
针对山西石港煤业有限责任公司煤与瓦斯突出制约安全生产的问题,采用了地面直井大液量水力压裂消突技术,有效解决了问题,实现了安全高效生产,可为类似条件的矿井提供借鉴。 相似文献
10.
The aim of this work was to prepare a novel dendritic branched nano-thickening agent by free radical polymerization of acrylamide (AM), acrylic acid (AA), sodium p-styrene sulfonate, dimethyl diallyl ammonium chloride, and multiwalled carbon nanotubes. The as-synthesized nano-thickening agent was characterized by Fourier transform infrared, Raman spectra, transmission electron microscope, 1H-NMR, and thermogravimetric analysis (TGA). Compared with the pristine polymer and partially hydrolyzed polyacrylamide (HPAM), thickening capacity, temperature resistance, and salt tolerance properties of the nano-thickening agent considerably improved, and the viscosity of 0.5% nano-polymer solution was 126.5 mPa·s. Additionally, the properties of the nano-gel prepared by nano-thickener, such as temperature and shear tolerance, viscoelasticity, sand carrying capacity, and gel breaking performance, were evaluated showing the satisfactory performance of the nano-gel under high temperature condition. The results indicated that the nano-thickener has potential applications in the field of oil and gas production. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48446. 相似文献