全文获取类型
收费全文 | 9934篇 |
免费 | 999篇 |
国内免费 | 696篇 |
专业分类
电工技术 | 106篇 |
综合类 | 847篇 |
化学工业 | 1197篇 |
金属工艺 | 859篇 |
机械仪表 | 140篇 |
建筑科学 | 2062篇 |
矿业工程 | 829篇 |
能源动力 | 254篇 |
轻工业 | 62篇 |
水利工程 | 894篇 |
石油天然气 | 3819篇 |
武器工业 | 11篇 |
无线电 | 41篇 |
一般工业技术 | 236篇 |
冶金工业 | 198篇 |
原子能技术 | 21篇 |
自动化技术 | 53篇 |
出版年
2024年 | 32篇 |
2023年 | 139篇 |
2022年 | 409篇 |
2021年 | 498篇 |
2020年 | 421篇 |
2019年 | 375篇 |
2018年 | 356篇 |
2017年 | 411篇 |
2016年 | 546篇 |
2015年 | 474篇 |
2014年 | 665篇 |
2013年 | 607篇 |
2012年 | 823篇 |
2011年 | 687篇 |
2010年 | 460篇 |
2009年 | 462篇 |
2008年 | 412篇 |
2007年 | 524篇 |
2006年 | 556篇 |
2005年 | 437篇 |
2004年 | 361篇 |
2003年 | 341篇 |
2002年 | 271篇 |
2001年 | 237篇 |
2000年 | 207篇 |
1999年 | 174篇 |
1998年 | 122篇 |
1997年 | 97篇 |
1996年 | 74篇 |
1995年 | 83篇 |
1994年 | 77篇 |
1993年 | 39篇 |
1992年 | 48篇 |
1991年 | 22篇 |
1990年 | 31篇 |
1989年 | 16篇 |
1988年 | 20篇 |
1987年 | 10篇 |
1986年 | 7篇 |
1985年 | 22篇 |
1984年 | 24篇 |
1983年 | 13篇 |
1982年 | 15篇 |
1981年 | 2篇 |
1980年 | 10篇 |
1979年 | 12篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
1.
Prediction of methane adsorption content in continental coal-bearing shale reservoir using SLD model
Shale gas, as an important unconventional resource, has drawn global attention. It is mainly composed of adsorption gas and free gas. Adsorption gas content could play an important guiding role on both the selection of favorable perspective area and the exploration and exploitation of shale gas resources. In order to accurately measure adsorption gas content, a new approach was established to predict the adsorption isotherm of methane on shale. Based on the simplified local-density (SLD) method, both the adsorption isotherms of illite, illite/smectite mixed-layer, cholorite and type III kerogen and the total shale rock could be well fitted. The fitting results show good coincidences with the true experimental test data, which proves the method is reasonable and dependable and the prediction results are effective and credible. In addition, the good simulation results show that the SLD parameters can reflect the pore structure characteristics and corresponding adsorption characteristics of the shale samples, which can be used for the quantitative characterization of shale pore system. 相似文献
2.
《Ceramics International》2022,48(8):10506-10515
The search for materials and methods capable of reducing human impacts on the environment is of utmost importance nowadays. This study's primary purpose was to analyze the technical feasibility of ceramic composites production utilizing Fundão Dam's Iron Ore Tailings (IOT), Blast Furnace Slag (BFS) from charcoal, and Foundry Sand (FS) as partial substitutes for the traditional raw materials – sand and clay – for application in building industry materials. The composites were molded in rectangular specimens and fired at temperatures of 900, 950, 1000, 1050, and 1200 °C. The developed materials were analyzed and characterized by X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS), Thermogravimetry (TGA), and Differential Thermal Analysis (DTA). The obtained materials had flexural strength modulus of up to 12.19 MPa, water absorption ranging from 2 to 22%, linear shrinkage ranging from 0.02 to 6.50%, and apparent density ranging from 2.03 to 1.63 g/cm3. The study of the internal structure formation process revealed the formation of amorphous structures in the composites. The results demonstrated that these waste materials may be jointly used in construction materials, contributing to the reduction of natural resource extraction, besides enabling their correct disposal, minimizing environmental impacts, and improving the life quality of the surrounding communities. 相似文献
3.
PETROLEUM POTENTIAL, THERMAL MATURITY AND THE OIL WINDOW OF OIL SHALES AND COALS IN CENOZOIC RIFT BASINS, CENTRAL AND NORTHERN THAILAND 总被引:1,自引:0,他引:1
Oil shales and coals occur in Cenozoic rift basins in central and northern Thailand. Thermally immature outcrops of these rocks may constitute analogues for source rocks which have generated oil in several of these rift basins. A total of 56 oil shale and coal samples were collected from eight different basins and analysed in detail in this study. The samples were analysed for their content of total organic carbon (TOC) and elemental composition. Source rock quality was determined by Rock‐Eval pyrolysis. Reflected light microscopy was used to analyse the organic matter (maceral) composition of the rocks, and the thermal maturity was determined by vitrinite reflectance (VR) measurements. In addition to the 56 samples, VR measurements were carried out in three wells from two oil‐producing basins and VR gradients were constructed. Rock‐Eval screening data from one of the wells is also presented. The oil shales were deposited in freshwater (to brackish) lakes with a high preservation potential (TOC contents up to 44.18 wt%). They contain abundant lamalginite and principally algal‐derived fluorescing amorphous organic matter followed by liptodetrinite and telalginite (Botryococcus‐type). Huminite may be present in subordinate amounts. The coals are completely dominated by huminite and were formed in freshwater mires. VR values from 0.38 to 0.47%Ro show that the exposed coals are thermally immature. VR values from the associated oil shales are suppressed by 0.11 to 0.28%Ro. The oil shales have H/C ratios >1.43, and Hydrogen Index (HI) values are generally >400 mg HC/g TOC and may reach 704 mg HC/ gTOC. In general, the coals have H/C ratios between about 0.80 and 0.90, and the HI values vary considerably from approximately 50 to 300 mg HC/gTOC. The HImax of the coals, which represent the true source rock potential, range from ~160 to 310 mg HC/g TOC indicating a potential for oil/gas and oil generation. The steep VR curves from the oil‐producing basins reflect high geothermal gradients of ~62°C/km and ~92°C/km. The depth to the top oil window for the oil shales at a VR of ~0.70%Ro is determined to be between ~1100 m and 1800 m depending on the geothermal gradient. The kerogen composition of the oil shales and the high geothermal gradients result in narrow oil windows, possibly spanning only ~300 to 400 m in the warmest basins. The effective oil window of the coals is estimated to start from ~0.82 to 0.98%Ro and burial depths of ~1300 to 1400 m (~92°C/km) and ~2100 to 2300 m (~62°C/km) are necessary for efficient oil expulsion to occur. 相似文献
4.
5.
6.
7.
琼东南盆地深水区经历了断陷、断拗和拗陷3大构造演化和沉积充填阶段,主要发育4种沉积体系,相应地形成了4类主要储层:1)陵三段扇三角洲或滨海相砂岩储层;2)三亚、梅山组滨浅海相砂岩储层;3)三亚—莺黄组低位体储层;4)梅山组台地边缘礁滩灰岩储层。平面上,储层发育具有明显的分带性,可划分为:北部浅水陆架滨岸砂岩、三角洲砂岩储层发育带;中央坳陷低位体储层发育带;南部永乐隆起区碳酸盐岩储层发育带。深水区主要位于后2个带,每个带储层发育的控制因素不同,可以进一步划分为多个储层发育区。每个储层发育区存在多套储盖组合,每套储盖组合在多个储层区中发育。其中台地灰岩储层可能成为南部隆起区具有重要意义的勘探层系。 相似文献
8.
9.