全文获取类型
收费全文 | 23243篇 |
免费 | 1949篇 |
国内免费 | 876篇 |
专业分类
电工技术 | 320篇 |
综合类 | 3293篇 |
化学工业 | 2049篇 |
金属工艺 | 2817篇 |
机械仪表 | 3527篇 |
建筑科学 | 4773篇 |
矿业工程 | 647篇 |
能源动力 | 267篇 |
轻工业 | 424篇 |
水利工程 | 628篇 |
石油天然气 | 1666篇 |
武器工业 | 175篇 |
无线电 | 832篇 |
一般工业技术 | 2524篇 |
冶金工业 | 707篇 |
原子能技术 | 72篇 |
自动化技术 | 1347篇 |
出版年
2024年 | 117篇 |
2023年 | 340篇 |
2022年 | 518篇 |
2021年 | 664篇 |
2020年 | 677篇 |
2019年 | 626篇 |
2018年 | 700篇 |
2017年 | 852篇 |
2016年 | 876篇 |
2015年 | 815篇 |
2014年 | 1479篇 |
2013年 | 1341篇 |
2012年 | 1624篇 |
2011年 | 1771篇 |
2010年 | 1530篇 |
2009年 | 1459篇 |
2008年 | 1238篇 |
2007年 | 1656篇 |
2006年 | 1438篇 |
2005年 | 1125篇 |
2004年 | 1040篇 |
2003年 | 806篇 |
2002年 | 599篇 |
2001年 | 530篇 |
2000年 | 494篇 |
1999年 | 352篇 |
1998年 | 255篇 |
1997年 | 232篇 |
1996年 | 188篇 |
1995年 | 194篇 |
1994年 | 98篇 |
1993年 | 84篇 |
1992年 | 84篇 |
1991年 | 53篇 |
1990年 | 38篇 |
1989年 | 33篇 |
1988年 | 41篇 |
1987年 | 16篇 |
1986年 | 8篇 |
1985年 | 12篇 |
1984年 | 10篇 |
1983年 | 6篇 |
1982年 | 7篇 |
1980年 | 5篇 |
1960年 | 4篇 |
1959年 | 4篇 |
1957年 | 3篇 |
1956年 | 5篇 |
1955年 | 6篇 |
1954年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
O. A. Lambri J. I. Prez-Landazbal J. A. Cano V. Recarte 《Materials Science and Engineering: A》2004,370(1-2):459-463
Mechanical spectroscopy, neutron diffraction and differential scanning calorimetry (DSC) were performed on commercial Fe–6 wt.% Si alloy after quenching from high temperature. The damping spectrum shows a peak at around 800 K and an associated modulus defect. The modulus shows an increase during the second and subsequent heating runs. In addition, an anomaly in the modulus behavior has been found at around 400 K. Different thermal treatments allows to obtain two different recovery degrees of the quenched-in defects. The influence of the recovery degree on the 800 K internal friction peak and on the anelastic modulus has been evaluated and confirm the validity of the grain boundary mechanism associated to this peak. Experimental results are discussed on the basis of recovery and ordering processes. 相似文献
22.
P. A. Boucard L. Champaney 《International journal for numerical methods in engineering》2003,57(9):1259-1281
The aim of the present work is to develop an application of the LArge Time INcrement (LATIN) approach for the parametric analysis of static problems with multiple contacts. The methodology adopted was originally introduced to solve viscoplastic and large‐transformation problems. Here, the applications concern elastic, quasi‐static structural assemblies with local non‐linearities such as unilateral contact with friction. Our approach is based on a decomposition of the assembly into substructures and interfaces. The interfaces play the vital role of enabling the local non‐linearities, such as contact and friction, to be modelled easily and accurately. The problem on each substructure is solved by the finite element method and an iterative scheme based on the LATIN method is used for the global resolution. More specifically, the objective is to calculate a large number of design configurations. Each design configuration corresponds to a set of values of all the variable parameters (friction coefficients, prestress) which are introduced into the mechanical analysis. A full computation is needed for each set of parameters. Here we propose, as an alternative to carrying out these full computations, to use the capability of the LATIN method to re‐use the solution to a given problem (for one set of parameters) in order to solve similar problems (for the other sets of parameters). Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
23.
A system whose partial information is known and partial information is unknown is called gray system. In this paper, the compatibility relationship between Styrene-Butadiene-Styrene (SBS) modifier and base asphalt composition was studied by correlation analysis method. The analysis results of correlation level show that aromatics and asphaltene of base asphalt affect SBS modified effect mainly as the content of SBS is lower, while the content of aromatics and resin become the main effect factors as SBS content is increased. 相似文献
24.
25.
从范围、原材料要求、组分要求、物理力学性能等方面对比分析了我国现行油毡瓦标准与欧美标准的区别,提出了我国制订沥青油毡瓦国家标准的的原则。 相似文献
26.
管材拉伸时把模具定径区看作准塑区,利用塑性条件,研究定径区摩擦力对拉伸力的影响,并对计算公式进行探讨。证明管材空拉(减径不减壁)时摩擦力影响可忽略不计,但减径、减壁拉伸同时进行时,定径区摩擦力对拉伸力的影响就必须考虑。 相似文献
27.
This study reports the influence of methyl isopropyl ketone on the tribological performance of zinc dialkyldithiophosphate. The lubricity and friction and wear tests of 500 SN neutral base stock oil containing zinc dialkyldithiophosphate with methyl isopropyl ketone were carried out by MQ-800 four-ball and MM-200 block-on-ring tribometers respectively. The experimental results show that methyl isopropyl ketone decreases the wear resistance and the load-carrying capacity of zinc dialkyldithiophosphate. The friction reduction of zinc dialkyldithiophosphate was lowered as well because of the addition of ketone. The friction and wear mechanism of zinc dialkyldithiophosphate with trace ketone was studied by optical microscopy IR, SEM, XPS and ferrography. The variations of the tribological performance of zinc dialkyldithiophosphate with ketone could be partly attributed to the decreases of active species, such as phosphorus and zinc, which are responsible for the formation of anti-wear films, on the rubbing surface due to the existence of ketone. 相似文献
28.
29.
以灌溉、防洪为主的峡口水库大坝,为沥青混凝土面板堆石坝,为研究低温抗裂性能,对沥青混凝土面板破损取样,进行了配比和多种力学性能试验,并与原面板设计指标进行了对比。由于面板经受住了-20℃以下的低温考验,其所用沥青指标、破损取样试验结果,特别是冻断低温指标,对确定水工沥青混凝土低温抗裂检验标准有重要参考价值。 相似文献
30.
One of the new physical methods that provides much information about the processes going on in a friction contact zone in real time is acoustic emission (AE). Basic experimental results of AE in friction are presented and analysed. Using AE signals we can get an indication about the state of the friction processes, about the quality of solid and liquid layers on the contacting surfaces in real time, sometimes about intensity of wear, changing of wear and friction regimes and so on. The influence of sliding velocity, load, roughness and some physical and mechanical properties of the body on the parameters of AE are also given. Some attention to the practical implementation of these techniques for control of capability for work of friction pairs in real conditions are given. Modern methods and devices enable condition monitoring of sliding and rolling bearings. 相似文献