全文获取类型
收费全文 | 36773篇 |
免费 | 4692篇 |
国内免费 | 2985篇 |
专业分类
电工技术 | 3676篇 |
综合类 | 3494篇 |
化学工业 | 4988篇 |
金属工艺 | 2384篇 |
机械仪表 | 2341篇 |
建筑科学 | 2780篇 |
矿业工程 | 1209篇 |
能源动力 | 882篇 |
轻工业 | 4350篇 |
水利工程 | 1120篇 |
石油天然气 | 1073篇 |
武器工业 | 531篇 |
无线电 | 4105篇 |
一般工业技术 | 3649篇 |
冶金工业 | 1693篇 |
原子能技术 | 593篇 |
自动化技术 | 5582篇 |
出版年
2024年 | 309篇 |
2023年 | 799篇 |
2022年 | 1643篇 |
2021年 | 2229篇 |
2020年 | 1617篇 |
2019年 | 1102篇 |
2018年 | 1206篇 |
2017年 | 1415篇 |
2016年 | 1263篇 |
2015年 | 1986篇 |
2014年 | 2297篇 |
2013年 | 2676篇 |
2012年 | 2961篇 |
2011年 | 3210篇 |
2010年 | 2834篇 |
2009年 | 2608篇 |
2008年 | 2728篇 |
2007年 | 2452篇 |
2006年 | 2214篇 |
2005年 | 1723篇 |
2004年 | 1193篇 |
2003年 | 811篇 |
2002年 | 798篇 |
2001年 | 717篇 |
2000年 | 581篇 |
1999年 | 260篇 |
1998年 | 108篇 |
1997年 | 104篇 |
1996年 | 81篇 |
1995年 | 80篇 |
1994年 | 58篇 |
1993年 | 47篇 |
1992年 | 31篇 |
1991年 | 33篇 |
1990年 | 36篇 |
1989年 | 46篇 |
1988年 | 24篇 |
1987年 | 28篇 |
1986年 | 19篇 |
1985年 | 9篇 |
1983年 | 13篇 |
1982年 | 5篇 |
1981年 | 15篇 |
1980年 | 19篇 |
1979年 | 11篇 |
1977年 | 5篇 |
1976年 | 5篇 |
1968年 | 4篇 |
1959年 | 9篇 |
1951年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
2.
3.
This study assessed the collection efficiency (CE) of two popularly used sampling devices (BioSampler and Coriolis sampler) for fungal aerosols. Phosphate‐buffered saline (PBS) supplemented with or without surfactant (Tween‐20, Tween‐80, or Triton X‐100) and antifoam agent was prepared and used as collection liquids. The agar impactor (BioStage) was simultaneously operated with liquid‐based samplers to collect fungi from seven sites located at a university building, public library, and animal farming. Fungal concentrations determined by liquid samplers were divided by those by BioStage, and the ratio values represented CE. Results indicate that the CE of BioSampler was superior to that of Coriolis (P = 0.0001) and the PBS containing surfactant collected fungi better than that without surfactant (P < 0.0001), whereas antifoam agent showed no influence (P = 0.8). Moreover, fungal concentrations determined by BioSampler with surfactant‐added PBS were statistically indifferent from those by BioStage (P > 0.05) with a Spearman correlation coefficient of 0.81‐0.83 (P < 0.01). In addition to sampler and collection liquid, sampling location was also identified as a significant CE factor (P = 0.006), implying potential influences by fungal genera in the studied fields. Overall, BioSampler with surfactant‐supplemented PBS (eg, Triton X‐100) is recommended considering the great CE and compatibility with a variety of analytical assays. 相似文献
4.
5.
6.
Yanqiu Shao Jiqing Han Ting Liu Yongzhen Zhao 《International Journal of Speech Technology》2007,10(1):45-55
In real speech, not like lexical words (LWs), prosodic words (PWs) are basic rhythmic units. The naturalness of a Text-to-Speech
(TTS) system is directly influenced by the segmentation of the PWs. Most of the PWs are the combination of several LWs. In
this paper, three Lexical Combination Models are proposed to combine LWs into PWs, including a Directed Acyclic Graph Model,
a Segmentation Model and a Markov Model (MM). To cope with the situation where some long LWs should be segmented into two
or more PWs, a Lexical Split Model (LSM) is applied to the long LWs. Experimental results prove that relatively constant results
with various training data can be obtained from a MM. The Transformation-Based Error Driven Learning (TBED) algorithm, for
its high performance of individual property, is applied in combination with the MM to improve the precision of PW segmentation.
Experiments show that among the three proposed models, the MM combined with TBED and LSM, leads to the best performance, in
which a precision of 93.00% and a recall of 93.23% are achieved. The perception test indicates that by using PWs as the lowest
prosodic units a speech sounds more natural and acceptable than by using LWs.
This paper is supported by NSFC Project (60503071); 973 Natural Basic Research Program of China (2004CB318102); Postdoctor
Science Foundation of P. R. China (20070420275). 相似文献
7.
8.
已建成的兰州重离子加速器的真空室是一个大型整体结构的超高真空容器,直径约10m,高4.5m,重65000kg,内表面积211m~2,容积100m~3,工作真空度为5×10~(-5)Pa。采用有限单元法在计算机上用SAP-5C程序对真空室受力分析进行了计算。真空室结构材料选用瑞典Uddeholm钢厂生产的316 L 超低碳不锈钢。承制此大型容器的是航天工业部风华机器厂。由于结构庞大,首先将真空室分成八大块和几小块在工厂制造,然后运至现场焊制成一整体容器并进行机械加工。所有密封焊缝均用着色渗透液,X-射线探伤和氦质谱探漏仪进行检查和探漏。 相似文献
9.
10.
文章通过对五口井的现场应用介绍,阐述了快速色谱分析技术在油气层识别和解释方面的准确性,探讨了该技术在薄油气层的发现和评价、快速钻进条件下油气层的发现、对油气层全烃组份变化的统一、水平井的地质导向以及排除钻井液添加荆对油气显示的影响五个方面的优势,从而论证了快速色谱分析技术在油气勘探中的应用价值。 相似文献