全文获取类型
收费全文 | 1020篇 |
免费 | 138篇 |
国内免费 | 31篇 |
专业分类
电工技术 | 44篇 |
综合类 | 34篇 |
化学工业 | 187篇 |
金属工艺 | 28篇 |
机械仪表 | 23篇 |
建筑科学 | 13篇 |
矿业工程 | 8篇 |
能源动力 | 117篇 |
轻工业 | 1篇 |
水利工程 | 1篇 |
石油天然气 | 605篇 |
无线电 | 20篇 |
一般工业技术 | 46篇 |
冶金工业 | 3篇 |
原子能技术 | 2篇 |
自动化技术 | 57篇 |
出版年
2024年 | 4篇 |
2023年 | 45篇 |
2022年 | 112篇 |
2021年 | 147篇 |
2020年 | 173篇 |
2019年 | 140篇 |
2018年 | 91篇 |
2017年 | 43篇 |
2016年 | 96篇 |
2015年 | 52篇 |
2014年 | 80篇 |
2013年 | 77篇 |
2012年 | 35篇 |
2011年 | 4篇 |
2010年 | 5篇 |
2009年 | 10篇 |
2008年 | 6篇 |
2007年 | 3篇 |
2006年 | 5篇 |
2005年 | 5篇 |
2004年 | 4篇 |
2003年 | 1篇 |
2002年 | 5篇 |
2001年 | 5篇 |
2000年 | 3篇 |
1999年 | 7篇 |
1998年 | 2篇 |
1996年 | 4篇 |
1995年 | 2篇 |
1994年 | 2篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1991年 | 3篇 |
1990年 | 3篇 |
1989年 | 6篇 |
1988年 | 3篇 |
1982年 | 1篇 |
1981年 | 3篇 |
排序方式: 共有1189条查询结果,搜索用时 31 毫秒
41.
井漏是钻井过程中常见的复杂难题,针对常用聚合物凝胶堵漏剂抗温性能差、承压封堵能力弱的问题,通过分子结构设计,以丙烯酰胺、甲基丙烯酸丁酯和2-丙烯酰氨基-2-甲基丙磺酸为单体,柔性纤维为强化材料,过硫酸铵为引发剂,通过与自制大分子交联剂BWL聚合反应,制备了一种新型抗高温纤维强化凝胶堵漏剂。研究了柔性纤维对凝胶堵漏剂流变性能的影响,通过扫描电镜、热重、承压堵漏实验等对凝胶堵漏剂的微观结构、热稳定性、吸水膨胀性和承压堵漏性能进行了研究。结果表明:柔性纤维增强了凝胶堵漏剂的空间网架结构,使其韧性更强;凝胶堵漏剂颗粒具有良好的热稳定性和吸水膨胀性,通过“吸水膨胀、挤压充填”的堵漏原理对漏失通道进行封堵,在140℃下对高渗透性漏失层的封堵承压高于7 MPa,对宽裂缝漏失通道封堵后承压高于5 MPa,可满足高温高压漏失地层中堵漏目的。 相似文献
42.
油井在生产过程中适度出砂开采可以降低成本、提高开发效率和油井产能。通过室内模拟油井出砂环境实验,研发了一套对油井出砂产生的高频振动信号进行实时监测的系统。该系统通过对不同粒径的砂粒撞击管壁产生的高频振动信号进行时频分析,确定了砂粒撞击管壁产生的振动信号所在的频率段为10 000~20 000 Hz,得到了油井出砂状态下砂粒的振动特征频率,进而获得了不同出砂量与信号时域幅值和自功率谱幅值的关系曲线,实现了对油井出砂量的实时检测,验证了高频振动信号监测油井出砂的可行性。 相似文献
43.
A generic algorithmic framework for nonlinear ensemble filtering based on Gaussian mixtures and fuzzy clustering techniques is introduced. The framework generalizes the ensemble Kalman filter and relaxes the assumption of a Gaussian prediction distribution. A theoretical analysis of the proposed procedure is provided, establishing strong consistency under suitable assumptions. Specific implementations are discussed and adjustments that are necessary in high-dimensional settings are proposed. A simple implementation of the filter is shown to work well in common testbeds, providing substantial gains over the ensemble Kalman filter. 相似文献
44.
《Energy Policy》2013
Interest in the role embodied energy plays in international trade and its subsequent impact on energy security has grown. As a developed nation, the UK's economic structure has changed from that of a primary producer to that of a primary consumer. Although the UK's energy consumption appears to have peaked, it imports a lot of energy embodied in international trade alongside the more obvious direct energy imports. The UK has seen increasing dependency on imported fossil energy since the UK became a net energy importer in 2005. In this paper an energy input–output model is established to calculate not only the amount of fossil energy embodied in UK's imports and exports, but also the sector and country distributions of those embodied fossil energy. The research results suggest the following: UK's embodied fossil energy imports have exceeded embodied fossil energy exports every year since 1997, UK embodied energy imports through the so-called ‘Made in China’ phenomena are the largest accounting for 43% of total net fossil energy imports. If net embodied fossil energy imports are considered, the gap between energy consumption and production in UK is much larger than commonly perceived, with subsequent implications to the UK's energy security. 相似文献
45.
为了监测天然气水合物生成及分解过程中物性参数的变化规律,需要在反应釜中安装各种传感器测点,而测点的引入会对反应釜中的流体流动产生影响。为了有效减少测点对反应釜产生的干扰,利用数值模拟方法对测点尺寸与测点最小间距之间的关系进行了定量研究。结果表明,传感器测点的引入会对反应釜中的渗流场产生影响,测点尺寸越大、测点的间距越小,对渗流场的影响越大;对于尺寸为10 mm、9 mm、8 mm、7 mm和6 mm的测点,相应测点最小间距分别为60 mm、54 mm、48 mm、42 mm和36 mm时测点对反应釜流场的影响可以忽略不计。因此对反应釜进行传感器测点排布时,测点的间距不得小于测点尺寸的6倍,研究结果对同类实验反应釜中测点的合理布置具有重要参考价值。 相似文献
46.
Elastic impedance inversion with high efficiency
and high stability has become one of the main directions of
seismic pre-stack inversion. The nonlinear elastic impedance
inversion method based on a fast Markov chain Monte Carlo
(MCMC) method is proposed in this paper, combining
conventional MCMC method based on global optimization
with a preconditioned conjugate gradient (PCG) algorithm
based on local optimization, so this method does not depend
strongly on the initial model. It converges to the global
optimum quickly and efficiently on the condition that efficiency
and stability of inversion are both taken into consideration
at the same time. The test data verify the feasibility
and robustness of the method, and based on this method, we
extract the effective pore-fluid bulk modulus, which is
applied to reservoir fluid identification and detection, and
consequently, a better result has been achieved. 相似文献
47.
《Energy》2005,30(11-12):2194-2205
From the perspective of energy security and environmental sustainability, the use of currently underutilized residual heavy oil can increase the value and applicability of Integrated Gasification Combined Cycle (IGCC) power generation systems. In order to utilize such fuel in IGCC applications reliably and effectively, it is essential to understand the phenomena within the gasifier. Therefore, the gasification characteristics of Orimulsion™ (registered trademark of BITOR Ltd) were studied using a 2.4 t/d research. The gasifier has many unique measurement devices, such as heat flux probes, sampling devices for hot gas and partially reacted solids, an optical gas analyzer (laser Raman), etc. The gasifier provides a range of performance indicators, such as calorific value of the product gas, cold gas efficiency, carbon conversion efficiency, and the vertical distribution of those results. Gasification reaction mechanisms and the vertical distribution of heat flux, which are required for effective modeling of gasification phenomena, were also studied under various operating conditions. These results are of the form that can be used in the design and operation of actual gasifiers for use with feedstocks like Orimulsion™. 相似文献
48.
以太网适合于小型局域网,特别适合上网集中和用户数目多的高校局域网,提出一种基于以太网的宿舍楼宇网络规划,就其物理链路中的布线相关要求做了探讨,就管理网络和用户网络的Vlan、IP规划和安排等做阐述,最后给出网络拓扑图和网络规划具体实施流程。 相似文献
49.
环渤中地区新近系控藏模式与高丰度油藏勘探实践 总被引:1,自引:0,他引:1
环渤中地区新构造运动强烈,新近系是主要的含油层系。新近系勘探早期集中于凸起区和陡坡带,而斜坡带和凹陷区由于缺乏油气运移条件的系统性研究导致其勘探成效较差。基于前人研究和钻井资料,从分析环渤中地区新近系油气运移路径出发,通过建立“汇聚脊-断层-圈闭(脊-断-圈)”三元控藏模式,明确了受潜山风化壳汇聚脊控制的深层油气的汇聚能力是新近系油气富集的先决条件,并以圈闭面积为核心创建了聚油指数,用于定量评价深层油气的汇聚能力;明确了断层垂向运移是新近系成藏的关键,断层与汇聚脊、区域盖层的配置关系决定了断层的垂向运移量,当深层盖层的断接厚度小于220 m时油气可运移至浅层;明确了圈闭因素是新近系成藏的最终环节,圈闭与断层的配置关系控制了浅层油气的侧向分流能力,其中,“双断型砂体”的侧向充注能力较强。“汇聚脊-断层-圈闭”三元控藏模式进一步丰富了渤海油田晚期成藏理论,在指导发现大-中型新近系油田以及其他他源层系的勘探中展现出良好的应用前景。 相似文献
50.
地震属性可在一定程度上反映断层的空间特征,但对噪声很敏感,对复杂断裂的检测效果不佳。常规断层增强算法首先根据属性体计算断层方向,然后增强断层方向的断层信息,压制非断层方向的其他信息,但计算精度依赖于断层方向的计算精度。为此,基于断层在平面上具有线性特征、在空间上具有平面特征的假设,提出基于动态时间规整(DTW)的断层增强方法。利用DTW方法计算断层图像的最优断层线,运用非线性平滑、正向积累和反向追踪等方法有效提高了最优断层线的求解精度,完全去除了断层属性图像中的非断层信息,使断层更连续、清晰,断层分布、延伸特征更明显,同时去除了地震属性图像中的一些非线性局部特征。将复杂断层分解为局部窗口内的简单断层,然后在局部窗口内计算最优断层线,最后综合局部最优断层线得到最终的复杂断层增强结果。模型试算和实际资料处理结果表明,所提方法能抑制断层图像中的非断层信息,断层经过增强处理后更连续、清晰,具有较好的鲁棒性和适用性。 相似文献