全文获取类型
收费全文 | 78958篇 |
免费 | 7404篇 |
国内免费 | 4064篇 |
专业分类
电工技术 | 4957篇 |
技术理论 | 3篇 |
综合类 | 7118篇 |
化学工业 | 13051篇 |
金属工艺 | 4238篇 |
机械仪表 | 4678篇 |
建筑科学 | 6387篇 |
矿业工程 | 2181篇 |
能源动力 | 1894篇 |
轻工业 | 8498篇 |
水利工程 | 1597篇 |
石油天然气 | 3607篇 |
武器工业 | 697篇 |
无线电 | 8420篇 |
一般工业技术 | 8340篇 |
冶金工业 | 3090篇 |
原子能技术 | 801篇 |
自动化技术 | 10869篇 |
出版年
2024年 | 314篇 |
2023年 | 1296篇 |
2022年 | 2475篇 |
2021年 | 3281篇 |
2020年 | 2589篇 |
2019年 | 2113篇 |
2018年 | 2215篇 |
2017年 | 2453篇 |
2016年 | 2239篇 |
2015年 | 3194篇 |
2014年 | 4325篇 |
2013年 | 4857篇 |
2012年 | 5650篇 |
2011年 | 6134篇 |
2010年 | 5655篇 |
2009年 | 5317篇 |
2008年 | 5390篇 |
2007年 | 5017篇 |
2006年 | 4814篇 |
2005年 | 4019篇 |
2004年 | 2762篇 |
2003年 | 2251篇 |
2002年 | 2244篇 |
2001年 | 1922篇 |
2000年 | 1573篇 |
1999年 | 1388篇 |
1998年 | 977篇 |
1997年 | 782篇 |
1996年 | 729篇 |
1995年 | 625篇 |
1994年 | 440篇 |
1993年 | 288篇 |
1992年 | 243篇 |
1991年 | 211篇 |
1990年 | 151篇 |
1989年 | 126篇 |
1988年 | 109篇 |
1987年 | 58篇 |
1986年 | 53篇 |
1985年 | 27篇 |
1984年 | 21篇 |
1983年 | 16篇 |
1982年 | 19篇 |
1981年 | 6篇 |
1980年 | 19篇 |
1979年 | 12篇 |
1978年 | 4篇 |
1976年 | 4篇 |
1959年 | 4篇 |
1951年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
41.
Understanding semantic word shifts in scientific domains is essential for facilitating interdisciplinary communication. Using a data set of published papers in the field of information retrieval (IR), this paper studies the semantic shifts of words in IR based on mining per-word topic distribution over time. We propose that semantic word shifts not only occur over time, but also over topics. The shifts are examined from two perspectives, the topic-level and the context-level. According to the over-time word-topic distribution, stable words and unstable words are recognized. The diverging and converging trends in the unstable type reveal characteristics of the topic evolution process. The context-level shifts are further detected by similarities between word vectors. Our work associates semantic word shifts with the evolving of topics, which facilitates a better understanding of semantic word shifts from both topics and contexts. 相似文献
42.
43.
Qiang Xia Tao Feng Xiaowei Lou Ying Wang Yangying Sun Daodong Pan Jinxuan Cao 《International Journal of Food Science & Technology》2020,55(2):669-680
As a decisive attribute, flavour could be influenced by HP treatments through multiple physical and chemical pathways within the high pressure (HP)-assisted meat curing process. This investigation aimed to identify the major pathway influencing volatile flavour patterns of two representative vinasse-cured duck (VCD) products with HP treatments (150–300 MPa/15 min), including wet and dry types, by employing headspace fingerprinting as an untargeted approach. Results suggested that HP treatments greatly lowered moisture contents and increased Warner-Bratzler shear force and thiobarbituric acid reactive substances of the cured samples. According to multivariate models, the volatile flavour patterns of the HP-processed VCD could be clearly separated from the unprocessed samples, but the VCD pressurised at different intensities represented similar volatile fingerprinting, which was validated by e-nose analysis. The discriminant analysis (OPLS-DA) model outlined vinasse-derived ethanol, acetic acid, 3-methyl-1-butanol, 2-methyl-1-butanol, phenethyl alcohol and 2-methyl-3-octanone as the major discriminant aromas across the unpressurised and pressurised samples. 相似文献
45.
The application of deep learning in the field of object detection has
experienced much progress. However, due to the domain shift problem, applying an
off-the-shelf detector to another domain leads to a significant performance drop. A
large number of ground truth labels are required when using another domain to train
models, demanding a large amount of human and financial resources. In order to avoid
excessive resource requirements and performance drop caused by domain shift, this
paper proposes a new domain adaptive approach to cross-domain vehicle detection. Our
approach improves the cross-domain vehicle detection model from image space and
feature space. We employ objectives of the generative adversarial network and cycle
consistency loss for image style transfer in image space. For feature space, we align
feature distributions between the source domain and the target domain to improve the
detection accuracy. Experiments are carried out using the method with two different
datasets, proving that this technique effectively improves the accuracy of vehicle
detection in the target domain. 相似文献
46.
Multimedia Tools and Applications - In recent years, various chaotic maps have been used for image encryption. However, most of these image encryption algorithms entail a lot of floating-point... 相似文献
47.
Wang Lu-di Zhou Wei Xing Ying Liu Na Movahedipour Mahmood Zhou Xiao-guang 《浙江大学学报:C卷英文版》2019,20(3):405-413
Frontiers of Information Technology & Electronic Engineering - Reconstruction of a 12-lead electrocardiogram (ECG) from a serial 3-lead ECG has been researched in the past to satisfy the need... 相似文献
48.
49.
中国深层煤层气资源丰富,但总体勘探和认识程度较低,尚未形成较为系统的深层煤层气地质理论。通过解剖分析准噶尔盆地白家海凸起和鄂尔多斯盆地临兴区块深层"超饱和"煤层气井的试气/生产动态,估算原地游离气的含气量,分析了深层"超饱和"煤层气的形成条件。研究表明:①深层"超饱和"煤层气储层中除吸附气外,还含有原地游离气,用常规试气方法可直接获得气流,煤层气的产出不明显依赖于排水降压;②埋藏超过一定深度,在煤阶和温度的综合作用下,煤的吸附能力将随埋深的继续增加而降低,煤层中吸附气的饱和度有增加的趋势,在达到吸附饱和后,出现原地游离气并形成"超饱和"煤层气,盆地深层具有"超饱和"煤层气形成的优势条件;③由于地温梯度和压力梯度的不同,不同盆地"超饱和"煤层气出现的临界深度不同,异常高压和异常高热流可以降低深层"超饱和"煤层气形成的临界深度;④深层"超饱和"煤层气开发具有大大缩短见气时间、充分利用地层能量和累积产水量低等优势,有望成为未来煤层气勘探开发的一个重要领域。 相似文献
50.
Although Mg alloy possesses high specific strength, low density, and good biocompatibility, poor corrosion resistance hinders its further applications. In the present study, an innovative protective layer against corrosion was prepared on the AZ31 Mg alloy via alkali pretreatment followed by vanillic acid treatment. The alkali pretreatment supplied –OH for the AZ31 Mg alloy surface to react with vanillic acid. The vanillic acid treatment played a crucial role in enhancing the corrosion resistance due to the excellent ability to act as a barrier and retard aqueous solution penetration, which effectively isolated the underlying Mg alloy from the corrosive environment. The corrosion current density of alkali and vanillic acid-treated Mg alloy (AZ31V) almost showed two orders of magnitude lower values in comparison with that of the AZ31 Mg alloy, and the corrosion potential of AZ31V Mg alloy increased from −1.41 to −1.25 V. The immersion tests proved that there was no occurrence of severe corrosion. Hence, the alkali pretreatment and vanillic acid treatment may represent a promising method to improve the corrosion resistance of Mg alloy. 相似文献