全文获取类型
收费全文 | 16931篇 |
免费 | 1716篇 |
国内免费 | 844篇 |
专业分类
电工技术 | 864篇 |
综合类 | 902篇 |
化学工业 | 3462篇 |
金属工艺 | 549篇 |
机械仪表 | 381篇 |
建筑科学 | 715篇 |
矿业工程 | 1465篇 |
能源动力 | 1021篇 |
轻工业 | 786篇 |
水利工程 | 127篇 |
石油天然气 | 3606篇 |
武器工业 | 64篇 |
无线电 | 983篇 |
一般工业技术 | 893篇 |
冶金工业 | 2033篇 |
原子能技术 | 123篇 |
自动化技术 | 1517篇 |
出版年
2024年 | 66篇 |
2023年 | 224篇 |
2022年 | 417篇 |
2021年 | 552篇 |
2020年 | 556篇 |
2019年 | 478篇 |
2018年 | 453篇 |
2017年 | 537篇 |
2016年 | 664篇 |
2015年 | 612篇 |
2014年 | 1083篇 |
2013年 | 1212篇 |
2012年 | 1349篇 |
2011年 | 1392篇 |
2010年 | 944篇 |
2009年 | 890篇 |
2008年 | 784篇 |
2007年 | 962篇 |
2006年 | 940篇 |
2005年 | 803篇 |
2004年 | 689篇 |
2003年 | 644篇 |
2002年 | 596篇 |
2001年 | 479篇 |
2000年 | 379篇 |
1999年 | 341篇 |
1998年 | 260篇 |
1997年 | 219篇 |
1996年 | 200篇 |
1995年 | 195篇 |
1994年 | 120篇 |
1993年 | 98篇 |
1992年 | 72篇 |
1991年 | 53篇 |
1990年 | 52篇 |
1989年 | 36篇 |
1988年 | 18篇 |
1987年 | 24篇 |
1986年 | 18篇 |
1985年 | 14篇 |
1984年 | 12篇 |
1983年 | 8篇 |
1982年 | 10篇 |
1981年 | 3篇 |
1980年 | 6篇 |
1979年 | 4篇 |
1978年 | 3篇 |
1977年 | 3篇 |
1976年 | 3篇 |
1951年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 187 毫秒
91.
分布系统中多米诺效应的分析与消除 总被引:3,自引:0,他引:3
分布系统中发生故障后,错误信息在进程间的传播,以及由此引起的系统恢复过程中的多米诺效应是分布系统容错恢复技术所面临的最重要与最困难的问题.目前各种研究工作偏重于具体的系统动态恢复技术.本文的研究重点在于首次揭示多米诺效应本身固有的数量特征及其与分布系统技术参数间的联系,给出多米诺效应动态消除技术,引入系统额外开销的下限,并针对动态技术的缺点,探讨多米诺效应的静态消除技术,为解决困难开辟新途径. 相似文献
92.
93.
大规模高含硫原油的炼制工艺必须配套设置脱硫和硫磺回收装置。笔者针对硫磺回收装置的特点,为确保装置的安全平稳运行,提出了该装置自动控制设计中需要严格监控的工艺参数及重点部位,叙述了仪表选型原则和精确测量与控制的原理和方法。 相似文献
94.
The problem of recovery of three-dimensional microstructural parameters from two-dimensional images is addressed in its inverse form. Three-dimensional inhomogeneous solids with known microstructures are generated virtually and images of their cross-sections are analyzed. Three different types of randomly oriented microcracks and microcracks having preferential orientation with some scatter. Somewhat unexpected result is that, in all the cases considered, three-dimensional defect densities are very close to average values of corresponding two-dimensional parameters. 相似文献
95.
Ronak A. Kapadia Simant R. Upreti Ali Lohi Ioannis Chatzis 《Journal of Petroleum Science and Engineering》2006,51(3-4):214-222
In this work, a mathematical model is developed and simulated to determine gas dispersion along with solubility during the vapor extraction (Vapex) of live oil from a laboratory scale physical model. The physical model is a rectangular block of homogenous porous medium saturated with heavy oil and bitumen. At a given temperature and pressure, the block is initially exposed on its side to a solvent gas, which diffuses into the medium and gets absorbed. The absorption of gas reduces the viscosity of heavy oil and bitumen causing it to drain under gravity. The low-viscosity “live oil” is produced at the bottom of the porous block. The production of live oil with time is accompanied by the shrinkage of oil in the block as well as its increased exposure to gas from top. These phenomena of Vapex are described by the mathematical model, which is used to calculate live oil production with various values of gas solubility and dispersion. Their optimal values are determined for the vapor extraction of Cold Lake bitumen with butane by matching calculated live oil production with its experimental values published earlier. 相似文献
96.
Ariosto B. Jorge Gabriel O. Ribeiro Timothy S. Fisher 《International journal for numerical methods in engineering》2003,56(1):117-144
This work presents two new error estimation approaches for the BEM applied to 2D potential problems. The first approach involves a local error estimator based on a gradient recovery procedure in which the error function is generated from differences between smoothed and non‐smoothed rates of change of boundary variables in the local tangential direction. The second approach involves the external problem formulation and gives both local and global measures of error, depending on a choice of the external evaluation point. These approaches are post‐processing procedures. Both estimators show consistency with mesh refinement and give similar qualitative results. The error estimator using the gradient recovery approach is more general, as this formulation does not rely on an ‘optimal’ choice of an external parameter. This work presents also the use of a local error estimator in an adaptive mesh refinement procedure. This r‐refinement approach is based on the minimization of the standard deviation of the local error estimate. A non‐linear programming procedure using a feasible‐point method is employed using Lagrange multipliers and a set of active constraints. The optimization procedure produces finer meshes close to a singularity and results that are consistent with the problem physics. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
97.
提高页岩干馏装置采油率的建议 总被引:1,自引:0,他引:1
分析了影响采油效率的三大因素,提出了改进建议。采用新的回收工艺对系统内含油瓦斯进行回收,以提高采油效益。 相似文献
98.
《The Journal of Adhesion》2008,84(3):231-239
A process to fabricate stretchable gold tracks on silicone rubber substrates is studied by XPS, static water contact angle measurement, AFM, and SEM. The process involves several steps: removing uncured oligomers by hexane Soxhlet extraction; pre-stretching the substrate; activating the strained silicone surface by an oxygen plasma treatment; coating the strained substrate with 5 nm titanium and 80 nm gold layers; and finally releasing the sample. The plasma treatment creates a thin brittle silica-like layer that temporarily increases the substrate's surface energy. Indeed, the plasma treatment is followed by a hydrophobic recovery. As a consequence, the delay between plasma treatment and metal deposition has to be reduced as much as possible. The silica-like layer can be nicely observed after release. The entire process allows us to obtain stretchable metallized samples that remain conductive even after an excessive deformation leading to electrical failure. 相似文献
99.
稀散金属镓锗在选冶回收过程中的富集行为分析 总被引:3,自引:0,他引:3
凡口铅锌矿稀散金属镓锗主要是以类质同像形式存在于闪锌矿中,如何有效地综合回收镓锗是凡口矿建矿以来研究的主要课题之一。针对凡口矿综合回收稀散金属镓锗的历史、现状与进展,重点研究了镓锗在选矿回收和湿法冶炼过程中的富集行为及走向,为开发镓锗综合回收新技术提供理论指导,从而提高企业经济效益。 相似文献
100.