全文获取类型
收费全文 | 255024篇 |
免费 | 30069篇 |
国内免费 | 20356篇 |
专业分类
电工技术 | 22359篇 |
技术理论 | 1篇 |
综合类 | 27771篇 |
化学工业 | 32489篇 |
金属工艺 | 16577篇 |
机械仪表 | 17474篇 |
建筑科学 | 19285篇 |
矿业工程 | 9962篇 |
能源动力 | 6235篇 |
轻工业 | 30079篇 |
水利工程 | 8598篇 |
石油天然气 | 8984篇 |
武器工业 | 3539篇 |
无线电 | 27440篇 |
一般工业技术 | 22293篇 |
冶金工业 | 10411篇 |
原子能技术 | 4223篇 |
自动化技术 | 37729篇 |
出版年
2024年 | 1646篇 |
2023年 | 4362篇 |
2022年 | 10015篇 |
2021年 | 12638篇 |
2020年 | 9437篇 |
2019年 | 6618篇 |
2018年 | 6781篇 |
2017年 | 7994篇 |
2016年 | 7160篇 |
2015年 | 11439篇 |
2014年 | 14496篇 |
2013年 | 16983篇 |
2012年 | 20674篇 |
2011年 | 22059篇 |
2010年 | 20965篇 |
2009年 | 19717篇 |
2008年 | 20666篇 |
2007年 | 19802篇 |
2006年 | 17429篇 |
2005年 | 14025篇 |
2004年 | 10023篇 |
2003年 | 6983篇 |
2002年 | 6577篇 |
2001年 | 5816篇 |
2000年 | 4647篇 |
1999年 | 2030篇 |
1998年 | 843篇 |
1997年 | 604篇 |
1996年 | 559篇 |
1995年 | 482篇 |
1994年 | 313篇 |
1993年 | 270篇 |
1992年 | 239篇 |
1991年 | 171篇 |
1990年 | 137篇 |
1989年 | 150篇 |
1988年 | 113篇 |
1987年 | 76篇 |
1986年 | 61篇 |
1985年 | 40篇 |
1984年 | 35篇 |
1983年 | 39篇 |
1982年 | 36篇 |
1981年 | 35篇 |
1980年 | 72篇 |
1979年 | 49篇 |
1976年 | 5篇 |
1965年 | 5篇 |
1959年 | 54篇 |
1951年 | 56篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
52.
Ying Chen HuiLi Zhang YuNing Liang YanHua Gao Yongchao Li 《Petroleum Science and Technology》2019,37(7):787-795
In this study, a simple hydrothermal synthesis method was adapted for the preparation of Co-doping Co2+/F-/TiO2 nanotubes photocatalyst, and the micro-nano structure of catalysts prepared by biomimetic technology which makes the catalyst have super-oleophilicity property. Co2+/F-/TiO2 revealed improved photocatalytic performance for denitrification of light oil compared to single TiO2 photocatalysts. The enhance of photocatalytic activity can be attributed to narrowing the band gap, increasing the light response wavelength and exposing more highly active crystal surfaces due to synergistic effects of Co2+ and F? in the photocatalyst. 相似文献
53.
主要阐述在距离台技术大楼2 km远的海盐一家门频道采、编、播系统的构建。整个系统的搭建,充分考虑了时间、空间、距离等各方面的要求,突出异地构建的特点,融合了电视台的节目录制、安全播出、计算机网络、远程控制等多方面技术。 相似文献
54.
55.
目的: 探讨自身免疫性溶血性贫血(AIHA)患者外周血中调节性B细胞(Bregs)的表达及其在该病发病中的意义。方法:选择16例自身免疫性溶血性贫血患者和14例健康志愿者为研究对象,用流式细胞术分析外周血CD19+IL-10+调节性B细胞及CD19+CD24hiCD27+调节性B细胞的表达;ELISA方法检测培养上清液中IL-10的水平。结果:自身免疫性溶血性贫血患者外周血中CD19+IL-10+调节性B细胞、CD19+CD24hiCD27+调节性B细胞的表达分别为(1.27±0.39)%、(9.85±2.18)%,健康志愿者组分别为(2.92±0.71)%、(26.47±4.31)%,两组比较差异有统计学意义(P<0.05);自身免疫性溶血性贫血患者细胞培养上清中IL-10的水平低于健康志愿者组(P<0.05)。结论:自身免疫性溶血性贫血患者外周血中CD19+IL-10+调节性B细胞及CD19+CD24hiCD27+调节性B细胞比例降低,提示调节性B细胞可能参与自身免疫性溶血性贫血的发病过程。 相似文献
56.
57.
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
58.
59.
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
60.
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