全文获取类型
收费全文 | 27752篇 |
免费 | 3350篇 |
国内免费 | 1840篇 |
专业分类
电工技术 | 1993篇 |
技术理论 | 5篇 |
综合类 | 2348篇 |
化学工业 | 5623篇 |
金属工艺 | 1288篇 |
机械仪表 | 891篇 |
建筑科学 | 1597篇 |
矿业工程 | 1180篇 |
能源动力 | 2185篇 |
轻工业 | 1055篇 |
水利工程 | 606篇 |
石油天然气 | 1003篇 |
武器工业 | 181篇 |
无线电 | 1891篇 |
一般工业技术 | 2737篇 |
冶金工业 | 3243篇 |
原子能技术 | 223篇 |
自动化技术 | 4893篇 |
出版年
2024年 | 81篇 |
2023年 | 661篇 |
2022年 | 916篇 |
2021年 | 1046篇 |
2020年 | 1141篇 |
2019年 | 1034篇 |
2018年 | 908篇 |
2017年 | 1091篇 |
2016年 | 1124篇 |
2015年 | 1109篇 |
2014年 | 1830篇 |
2013年 | 1813篇 |
2012年 | 2142篇 |
2011年 | 2445篇 |
2010年 | 1855篇 |
2009年 | 1828篇 |
2008年 | 1724篇 |
2007年 | 1727篇 |
2006年 | 1448篇 |
2005年 | 1132篇 |
2004年 | 920篇 |
2003年 | 831篇 |
2002年 | 680篇 |
2001年 | 551篇 |
2000年 | 479篇 |
1999年 | 409篇 |
1998年 | 325篇 |
1997年 | 273篇 |
1996年 | 287篇 |
1995年 | 198篇 |
1994年 | 195篇 |
1993年 | 135篇 |
1992年 | 131篇 |
1991年 | 83篇 |
1990年 | 54篇 |
1989年 | 37篇 |
1988年 | 38篇 |
1987年 | 24篇 |
1986年 | 26篇 |
1985年 | 29篇 |
1984年 | 26篇 |
1983年 | 24篇 |
1982年 | 18篇 |
1981年 | 22篇 |
1980年 | 14篇 |
1979年 | 8篇 |
1978年 | 6篇 |
1977年 | 8篇 |
1964年 | 6篇 |
1951年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
马勇 《金属材料与冶金工程》2003,31(1):21-24
通过煤种,入窑球冷态强度和还原过程强度,以及钛精矿与煤灰混合物的软化温度等分析探讨了钛精矿预热球团回转窑直接还原产生结圈的可能性,获得了可以避免结圈的结论。 相似文献
62.
基于DMF捕获系统频率选择性信道下捕获性能的分析 总被引:1,自引:0,他引:1
对基于数字匹配滤波器(DMF)捕获系统在频率选择性信道下的捕获性能进行了深入讨论,利用状态转移图推导出单次驻留判决方式时平均捕获时间的表达式,对平均捕获时间与多径分量的关系进行了数字分析。得出的主要结论是:对于多径分量为非衰落信号时,多径分量之间的能量差别越大,系统捕获性能越好,多径分量的能量相等时,系统捕获性能最差,且随着可以分离的多径路数的增加下降;对于多径分量为慢衰落信号时,多径信道的捕获性能好于单径信道(非频率选择性衰落信道),且多径分量之间的能量差别越大,系统捕获性能越差,当多径分量的能量相等时,捕获性能最好,这与非衰落信道的情形相反。因此在频率选择性衰落信道中,采用分集接收可以改善系统的捕获性能。 相似文献
63.
Abstract: This paper presents a novelty detection-based technique to identify core material properties of honeycombs and cellular structures. A numerical model (finite element) representing full scale and/or reduced size of the cellular solid is used to generate transmissibilities between topological homologous points at cells in different locations. In order to make the procedure robust against noise, these transmissibilities are artificially corrupted. This step is representative of a series of experimentally obtained measurements which automatically return information relating to the size and shape of data noise along with the mean measurement. The next stage, both in this paper and in the proposal for the experimental approach, is to generate several further sets of transmissibilities from the finite element model; the only difference being that the core material properties are altered from the original values. A novelty detection framework is then adopted to find a similarity measure between each of these 'test' transmissibilities and the original set thereby identifying the material properties. Although this work is concerned with identifying only one material property, the methodology extends to identifying several properties. 相似文献
64.
1 Introduction Acquiring knowledge is constantly encountered in the mechanical product evaluation process, such as during setting up evaluation index system and determining evaluation knowledge. The most useful expression form of knowledge is production rule whenever concerning the field knowledge or decision knowledge. How to effectively acquire and express the knowledge becomes the issue that the evaluation work must solve at first. One of an important application of the rough set theory is … 相似文献
65.
Some therapists hold that the Bobo and other aggressive toys should be excluded from the playroom as they elicit acting-out behavior that is transferred to the world outside the playroom. However, many therapists view the inclusion of these items as imperative elements that facilitate positive growth and maturation in the child. Interviews with authorities in the field of play therapy support the position that the inclusion of the Bobo is not only useful, but a therapeutic necessity. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
66.
67.
Lash Steven J.; Stephens Robert S.; Burden Jennifer L.; Grambow Steven C.; DeMarce Josephine M.; Jones Mark E.; Lozano Brian E.; Jeffreys Amy S.; Fearer Stephanie A.; Horner Ronnie D. 《Canadian Metallurgical Quarterly》2007,21(3):387
Although continuing care is strongly related to positive treatment outcomes for substance use disorder (SUD), participation rates are low and few effective interventions are available. In a randomized clinical trial with 150 participants (97% men), 75 graduates of a residential Veterans Affairs Medical Center SUD program who received an aftercare contract, attendance prompts, and reinforcers (CPR) were compared to 75 graduates who received standard treatment (STX). Among CPR participants, 55% completed at least 3 months of aftercare, compared to 36% in STX. Similarly, CPR participants remained in treatment longer than those in STX (5.5 vs. 4.4 months). Additionally, CPR participants were more likely to be abstinent compared to STX (57% vs. 37%) after 1 year. The CPR intervention offers a practical means to improve adherence among individuals in SUD treatment. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
68.
化学还原法制备纳米铜粉的研究 总被引:18,自引:1,他引:17
本文采用KBH4在液相中化学还原CuSO4,并加入KOH和络合剂EDTA ,制得了纳米级的纯净的铜粉 ,通过调整反应物的浓度 ,可以消除Cu2 O等杂质。制备的纳米铜粉还存在一定程度的团聚 ,需试验加入分散剂来改善。 相似文献
69.
The noise of aerodynamics nature from modern transonic fan is examined from its sources with the perspective of noise reduction through aero-acoustics design using advanced Computational Fluid Dynamics (CFD) tools. In particular the problems associated with the forward propagating noise in the front is addressed. It is identified that the shock wave spillage from the leading edge near the fan tip is the main source of the tone noise. Two different approaches have been studied to reduce the forward arc tone noise and two state-of-art transonic fans are designed using the strategies developed. The following rig tests show that while the fans exhibit other noise problems, the primary goals of noise reduction have been achieved through both fans and the novel noise reduction concept vindicated. 相似文献
70.
对唐钢薄板坯连铸机生产的SS400钢的生产工艺进行了分析,认为薄板坯连铸机生产的SS400钢,在采取了精炼站在线定氧,将钢水全氧控制在25×10~(-6)左右,同时连铸采取保护浇注和轻压下等技术后,能够确保薄板坯连铸SS400钢的顺利浇注,轧制的板带材表面质量良好,机械性能符合要求。 相似文献