全文获取类型
收费全文 | 17752篇 |
免费 | 2823篇 |
国内免费 | 4331篇 |
专业分类
电工技术 | 394篇 |
技术理论 | 1篇 |
综合类 | 1915篇 |
化学工业 | 941篇 |
金属工艺 | 195篇 |
机械仪表 | 180篇 |
建筑科学 | 6468篇 |
矿业工程 | 5368篇 |
能源动力 | 325篇 |
轻工业 | 357篇 |
水利工程 | 1859篇 |
石油天然气 | 4483篇 |
武器工业 | 29篇 |
无线电 | 271篇 |
一般工业技术 | 773篇 |
冶金工业 | 876篇 |
原子能技术 | 86篇 |
自动化技术 | 385篇 |
出版年
2024年 | 65篇 |
2023年 | 185篇 |
2022年 | 546篇 |
2021年 | 732篇 |
2020年 | 765篇 |
2019年 | 631篇 |
2018年 | 632篇 |
2017年 | 755篇 |
2016年 | 830篇 |
2015年 | 804篇 |
2014年 | 1231篇 |
2013年 | 1141篇 |
2012年 | 1577篇 |
2011年 | 1636篇 |
2010年 | 1199篇 |
2009年 | 1248篇 |
2008年 | 1136篇 |
2007年 | 1285篇 |
2006年 | 1286篇 |
2005年 | 1280篇 |
2004年 | 1042篇 |
2003年 | 855篇 |
2002年 | 631篇 |
2001年 | 524篇 |
2000年 | 497篇 |
1999年 | 457篇 |
1998年 | 343篇 |
1997年 | 330篇 |
1996年 | 251篇 |
1995年 | 262篇 |
1994年 | 223篇 |
1993年 | 153篇 |
1992年 | 99篇 |
1991年 | 68篇 |
1990年 | 53篇 |
1989年 | 40篇 |
1988年 | 28篇 |
1987年 | 19篇 |
1986年 | 26篇 |
1985年 | 8篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1982年 | 4篇 |
1981年 | 8篇 |
1980年 | 7篇 |
1979年 | 10篇 |
1959年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
2.
为了解破碎围岩分别采用锚杆支护、锚喷支护以及锚喷+锚索耦合三种支护方式下的支护效果,进而为破碎围岩巷道选择合理的支护方式提供参考。通过借助FLAC3D软件建立数值模型,分析不同支护条件下的破碎围岩巷道位移量、应力分布以及塑性区的时空演化特征。结果表明,采用锚喷+锚索耦合支护时,可以较好的控制巷道围岩的位移量、减小应力集中效应、缩小塑性区的影响范围。 相似文献
3.
以重庆市甄子岩29号危岩体为研究对象,基于现场调查和分析解剖,建立UDEC离散元数值计算模型,对其演化变形过程进行模拟分析。研究表明,在巨大的自重作用下,由于基座岩体岩质软,岩体较破碎,且基座外侧为直立的陡崖,具有完整的临空面,从而使基座岩体易发生压缩流变及剪切流变,进而使危岩体存在滑移垮塌的危险。 相似文献
4.
Effective management of the risks associated with acid rock drainage (ARD) requires the ability to identify material with a potential to generate ARD reliably. With the increasing prevalence of quantitative mineralogy (Quantitative XRD, auto-SEM), opportunity exists to use mineralogy at all stages in ARD characterisation and prediction. This study uses a mineralogical approach across the head grade samples and the residues obtained under leach conditions of several common ARD characterisation tests (Acid Neutralising Capacity, Net Acid Generation), as well as the University of Cape Town (UCT) biokinetic test to evaluate the extent to which acid-neutralising minerals react. The results show the contribution of the carbonates to the acid neutralising capacity, as well as the partial dissolution of intermediate weathering silicate minerals such as chlorite and mica. 相似文献
5.
J. Cochard P. Léonide J. Borgomano Y. Guglielmi G. Massonnat J-P. Rolando L. Marié A. Pasquier 《Journal of Petroleum Geology》2020,43(1):75-94
Upper Barremian – Lower Aptian inner platform “Urgonian” limestones in the Mont de Vaucluse region, SE France, consist of alternating metre-scale microporous and tight intervals. This paper focuses on the influence of structural deformation on the reservoir properties of the Urgonian limestone succession in a study area near the town of Rustrel. Petrographic, petrophysical and structural data were recovered from five fully-cored boreholes, from the walls of a 100 m long underground tunnel, and from a 50 m long transect at a nearby outcrop. The data allowed reservoir property variations in the Urgonian limestones to be studied from core to reservoir scale. Eleven Reservoir Rock Types (RRTs) were identified based on petrographic features (texture, grain size), reservoir properties (porosity, permeability), and the frequency of structural discontinuities such as fractures, faults and stylolites. Tight and microporous reservoir rock types were distinguished. Tight reservoir rock types were characterised by early cementation of intergranular pore spaces and by the presence of frequent structural discontinuities. By contrast microporous reservoir rock types contained preserved intragranular microporosity and matrix permeability, but had very few structural discontinuities. Observed vertical alternations of microporous and tight rock types are interpreted to have been controlled by the early diagenesis of the Urgonian carbonates. Deformation associated with regional-scale tectonic phases, including Albian – Cenomanian “Durancian” uplift (∼105 to 96 Ma) and Pyrenean compression (∼55 to 25 Ma), resulted in the modification of the initial petrophysical properties of the Urgonian limestones. An early diagenetic imprint conditioned both the intensity of structural deformations and the associated circulations of diagenetic and meteoric fluids. Evolution of the Reservoir Rock Types is therefore linked both to the depositional conditions and to subsequent phases of structural deformation. 相似文献
6.
Wang Hay Kan Chenxi Wei Dongchang Chen Tao Bo Bao‐Tian Wang Yan Zhang Yangchao Tian Jun‐Sik Lee Yijin Liu Guoying Chen 《Advanced functional materials》2019,29(17)
Lithium‐rich disordered rock‐salt oxides have attracted great interest owing to their promising performance as Li‐ion battery cathodes. While experimental and theoretical efforts are critical in advancing this class of materials, a fundamental understanding of key property changes upon Li extraction is largely missing. In the present study, single‐crystal synthesis of a new disordered rock‐salt cathode material, Li1.3Ta0.3Mn0.4O2 (LTMO), and its use as a model compound to investigate Li concentration–driven evolution of local cationic ordering, charge compensation, and chemical distribution are reported. Through the combined use of 2D and 3D X‐ray nanotomography, it is shown that Li removal accompanied by oxygen oxidation is correlated with the development of morphological defects such as particle cracking. Chemical heterogeneity, quantified by subparticle level distribution of Mn valence state, is minimal during Mn redox, which drastically increases upon the formation of cracks during oxygen redox. Density functional theory and bond valence sum mismatch calculations reveal the presence of local short‐range ordering in the pristine oxide, which gradually disappears along with the extraction of Li. The study suggests that with cycling the transformation into true cation–disordered state can be expected, which likely impacts the voltage profile and obtainable energy density of the oxide cathodes. 相似文献
7.
Rock joints infilled with sediments can strongly influence the strength of rock mass. As infilled joints often exist under unsaturated condition, this study investigated the influence of matric suction of infill on the overall joint shear strength. A novel technique that allows direct measurement of matric suction of infill using high capacity tensiometers (HCTs) during direct shear of infilled joints under constant normal stiffness (CNS) is described. The CNS apparatus was modified to accommodate the HCT and the procedure is explained in detail. Joint specimens were simulated by gypsum plaster using three-dimensional (3D) printed surface moulds, and filled with kaolin and sand mixture prepared at different water contents. Shear behaviours of both planar infilled joints and rough joints having joint roughness coefficients (JRCs) of 8–10 and 18–20 with the ratios of infill thickness to asperity height (t/a) equal to 0.5 were investigated. Matric suction shows predominantly unimodal behaviour during shearing of both planar and rough joints, which is closely associated with the variation of unloading rate and volumetric changes of the infill material. As expected, two-peak behaviour was observed for the rough joints and both peaks increased with the increase of infill matric suction. The results suggest that the contribution of matric suction of infill on the joint peak normalised shear stress is relatively independent of the joint roughness. 相似文献
8.
湘中海相浅层湘冷1井酸压工艺研究及应用 总被引:2,自引:0,他引:2
湘冷1井具有气层埋藏浅(400m-500m)、纵向上裂隙发育的特点,属低孔、低渗的含泥质灰岩致密储层。大量室内实验和研究采用“前置液酸压+闭合酸化”工艺技术,并优选了相应降阻酸和闭合酸配方。通过酸压实现了该井工业油气流的突破,取得了明显的增产效果,为新区海相浅层气的开发探索出了一套成熟的改造增产措施。 相似文献
9.
10.
中原油田岩石可钻性与声波时差关系研究 总被引:3,自引:0,他引:3
选取中原油田的大量岩心,采用常规岩石力学测试方法测定了岩石的可钻性、声波测试方法测定了岩石和岩屑声波时差,通过对测得的岩石可钻性级值和声波时差进行回归拟合,得出了中原油田岩石可钻性与声波时差的关系式。现场应用表明,该关系式较好地反映了中原油田地层岩石可钻性与声波时差的关系,可以在优选钻头时作为参考或直接应用。 相似文献