全文获取类型
收费全文 | 353574篇 |
免费 | 28362篇 |
国内免费 | 15525篇 |
专业分类
电工技术 | 20820篇 |
技术理论 | 45篇 |
综合类 | 25343篇 |
化学工业 | 58923篇 |
金属工艺 | 20713篇 |
机械仪表 | 22498篇 |
建筑科学 | 27435篇 |
矿业工程 | 11540篇 |
能源动力 | 9698篇 |
轻工业 | 23698篇 |
水利工程 | 6714篇 |
石油天然气 | 23195篇 |
武器工业 | 2807篇 |
无线电 | 38485篇 |
一般工业技术 | 38988篇 |
冶金工业 | 18004篇 |
原子能技术 | 3625篇 |
自动化技术 | 44930篇 |
出版年
2024年 | 1110篇 |
2023年 | 5224篇 |
2022年 | 8834篇 |
2021年 | 13437篇 |
2020年 | 10178篇 |
2019年 | 8318篇 |
2018年 | 9670篇 |
2017年 | 10816篇 |
2016年 | 9910篇 |
2015年 | 13727篇 |
2014年 | 17354篇 |
2013年 | 20834篇 |
2012年 | 22739篇 |
2011年 | 25211篇 |
2010年 | 22288篇 |
2009年 | 21107篇 |
2008年 | 20690篇 |
2007年 | 19745篇 |
2006年 | 20119篇 |
2005年 | 17706篇 |
2004年 | 11994篇 |
2003年 | 10710篇 |
2002年 | 9913篇 |
2001年 | 8831篇 |
2000年 | 8799篇 |
1999年 | 9391篇 |
1998年 | 7152篇 |
1997年 | 6117篇 |
1996年 | 5794篇 |
1995年 | 4767篇 |
1994年 | 3847篇 |
1993年 | 2601篇 |
1992年 | 2053篇 |
1991年 | 1554篇 |
1990年 | 1217篇 |
1989年 | 981篇 |
1988年 | 809篇 |
1987年 | 485篇 |
1986年 | 388篇 |
1985年 | 238篇 |
1984年 | 186篇 |
1983年 | 139篇 |
1982年 | 124篇 |
1981年 | 72篇 |
1980年 | 95篇 |
1979年 | 43篇 |
1978年 | 17篇 |
1977年 | 23篇 |
1976年 | 28篇 |
1973年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
一、项目背景滨河千年古村桥南,地处福建省沿海城市泉州市的东端,作为连接东南亚和欧洲地中海的海上贸易网络—“海上丝绸之路”的起点而久负盛名。曾几何时,万国客商云集、千帆相竞的盛景而今已渐渐归于淡泊和悠远(图1)。桥南村隶属洛江区,镶嵌在一座山脉公园与洛阳江入海口之间。洛阳桥横跨江口,直通对岸洛阳小镇,这座千年花岗岩古桥已被确定为国家级物质文化遗产,桥村共生的格局使桥南民居历经时代历练,折射出本地区不同历史时期独特的建筑文化光影(图2)。泉州市政府于2004年开始申请“海上丝绸之路”成为联合国教科文组织世界文化遗址,… 相似文献
992.
993.
以ERP为切入点,简要的剖析了ERP的概念、ERP在齐鲁石化公司的实施过程以及在齐鲁石化公司产生的影响。 相似文献
994.
995.
Lake-Level Change and Water Balance Analysis at Lake Qinghai,West China during Recent Decades 总被引:7,自引:0,他引:7
Xiao-Yan Li He-Ye Xu Yong-Liang Sun Deng-Shan Zhang Zhi-Peng Yang 《Water Resources Management》2007,21(9):1505-1516
Lake Qinghai, the largest saline lake with an area of 4,260 km2 (2000) and average depth of 21 m (1985) in West China, has experienced severe decline in water level in recent decades. This
study aimed to investigate water balance of the lake and identify the causes for the decline in lake level. There was a 3.35-m
decline in water level with an average decreasing rate of 8.0 cm year−1 between 1959 and 2000. The lake water balance showed that mean annual precipitation between 1959 and 2000 over the lake was
357 ± 10 mm, evaporation was 924 ± 10 mm, surface runoff water inflow was 348 ± 21 mm, groundwater inflow was 138 mm ± 9 and
the change in lake level was −80 ± 31 mm. The variation of lake level was highly positively correlated to surface runoff and
precipitation and negatively to evaporation, the correlation coefficients were 0.89, 0.81 and −0.66, respectively. Water consumption
by human activities accounts for 1% of the evaporation loss of the lake, implying that water consumption by human activities
has little effect on lake level decline. Most dramatic decline in lake level occurred in the warm and dry years, and moderate
decline in the cold and dry years, and relatively slight decline in the warm and wet years, therefore, the trend of cold/warm
and dry climate in recent decades may be the main reasons for the decline in lake level. 相似文献
996.
997.
Ya-Li Song Jia Li Ling Yin Tian Huang Ping Gao 《The International Journal of Advanced Manufacturing Technology》2007,31(11-12):1058-1065
This paper presents a newly developed CAD approach for a quick and accurate design of a dental posterior prosthesis. The approach arises from the basic idea that every human tooth has its own specific features. Based upon the features of the standard posterior tooth, the initial data containing the defined feature points are firstly acquired from the scanned points of the standard tooth. The standard prosthetic profile is thereby formulated using the bicubic Nurbs surface fitting technique. This profile has the two functions of possessing the same features with the patient’s missing posterior tooth, and the adjustability with the feature points and the defined B-spline profile feature curves. For the purpose of the adjustment of the established model, the global and occlusal feature curves are proposed considering the individual patient’s original information. According to these curves, the corresponding standard prosthetic profile is locally adjusted to meet the fit of the global size and occlusal surface. Finally, a close and continuous profile of a posterior crown is generated. Using this design, a posterior prosthesis is successfully manufactured in the computer-aided machining process. 相似文献
998.
999.
Gossip (or epidemic) algorithms have recently become popular solutions to multicast message dissemination in peer-to-peer systems. Nevertheless, it is not straightforward to apply gossip to on-demand streaming because it often fails to achieve a timely delivery. To solve this problem and taking into account the characteristic of peers randomly joining and leaving in peer-to-peer systems, an Efficient Membership Management Protocol (EMMP) has been presented. Every node only needs to keep contact with O (log(N)) nodes, and EMMP can support the reliable dissemination of messages. Considering the “distance” between peers, it causes the major data to be transmitted in a local area and reduces the backbone’s traffic, and speeds up the dissemination of messages between peers. This paper has adopted the “goodfriend” mechanism to reduce the influence on the system when a peer fails or leaves. Simulation results show that EMMP is highly efficient, and both the redundancy and the delay of the system are well solved. 相似文献
1000.
Ma Weidong Liu Wen Wenmin Wang Luo Yong Bu Qinlian Xiouli Zhao Jiang Shan Li Wei 《Photonics Technology Letters, IEEE》2007,19(15):1115-1117
An athermal 40-channel dense wavelength-division-multiplexing multi/demultiplexer using a novel combination technology is proposed. It consists of one 1times4 100- to 400-GHz spacing interleaver filter and four sub-arrayed-waveguide gratings (AWGs). The temperature-dependent wavelength shift of the combined device is successfully suppressed to 0.058 nm in the -20degC to 70degC temperature range. Moreover, the combined device's adjacent crosstalk (typically -35 dB) is much better than conventional AWGs (typically -25 dB). 相似文献