全文获取类型
收费全文 | 234713篇 |
免费 | 27747篇 |
国内免费 | 18946篇 |
专业分类
电工技术 | 20933篇 |
技术理论 | 3篇 |
综合类 | 24663篇 |
化学工业 | 29594篇 |
金属工艺 | 15665篇 |
机械仪表 | 16603篇 |
建筑科学 | 17721篇 |
矿业工程 | 9468篇 |
能源动力 | 5992篇 |
轻工业 | 24603篇 |
水利工程 | 8064篇 |
石油天然气 | 9214篇 |
武器工业 | 3367篇 |
无线电 | 25675篇 |
一般工业技术 | 20813篇 |
冶金工业 | 9460篇 |
原子能技术 | 4063篇 |
自动化技术 | 35505篇 |
出版年
2024年 | 1228篇 |
2023年 | 3929篇 |
2022年 | 9376篇 |
2021年 | 12099篇 |
2020年 | 8789篇 |
2019年 | 6110篇 |
2018年 | 6353篇 |
2017年 | 7154篇 |
2016年 | 6302篇 |
2015年 | 10443篇 |
2014年 | 13130篇 |
2013年 | 15575篇 |
2012年 | 19137篇 |
2011年 | 20367篇 |
2010年 | 19248篇 |
2009年 | 17771篇 |
2008年 | 18849篇 |
2007年 | 18001篇 |
2006年 | 15801篇 |
2005年 | 12855篇 |
2004年 | 9072篇 |
2003年 | 6290篇 |
2002年 | 5792篇 |
2001年 | 5207篇 |
2000年 | 4336篇 |
1999年 | 2196篇 |
1998年 | 1063篇 |
1997年 | 800篇 |
1996年 | 739篇 |
1995年 | 632篇 |
1994年 | 495篇 |
1993年 | 376篇 |
1992年 | 355篇 |
1991年 | 240篇 |
1990年 | 199篇 |
1989年 | 186篇 |
1988年 | 138篇 |
1987年 | 92篇 |
1986年 | 84篇 |
1985年 | 56篇 |
1984年 | 53篇 |
1983年 | 56篇 |
1982年 | 50篇 |
1981年 | 54篇 |
1980年 | 78篇 |
1979年 | 52篇 |
1977年 | 12篇 |
1973年 | 13篇 |
1959年 | 53篇 |
1951年 | 52篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
81.
Qun Ren Haijun Su Jun Zhang Haifang Liu Weidan Ma Guangrao Fan Di Zhao Min Guo Lin Liu Hengzhi Fu 《Ceramics International》2019,45(6):6632-6638
Directionally solidified microstructures of Al2O3-Er3Al5O12 eutectic and off-eutectic in situ composite ceramics were explored under abrupt-change pulling rate conditions. Corresponding temperature distributions and interface locations were studied. In eutectic composition, fluctuation of eutectic spacing occurred when the pulling rate increased abruptly. A gradually increase or abrupt increase in eutectic spacing was observed when the pulling rate decreased abruptly. In hypoeutectic and hypereutectic compositions, formation of the primary phases were suppressed when the pulling rate increased abruptly from 10?µm/s to 100?µm/s, while primary phases precipitated when the pulling rate decreased abruptly from 100?µm/s to 10?µm/s. The interface altitude decreased after the pulling rate increased abruptly, but increased after the pulling rate decreased abruptly. The liquid composition restriction (around the eutectic composition) at the eutectic interface plays an important role in the suppression of the primary dendrite and coupled eutectic oxides can be obtained in off-eutectic compositions even under higher solidification rate conditions. 相似文献
82.
Journal of Computer Science and Technology - New non-volatile memory (NVM) technologies are expected to replace main memory DRAM (dynamic random access memory) in the near future. NAND flash... 相似文献
83.
84.
In the early design stage, automotive modeling should both meet the requirements of aesthetics and engineering. Therefore, a vehicle CAD (computer aided design) model that can be easily adjusted by feedbacks is necessary. Based on CE-Bézier surface, this paper presents a set of algorithms for parametric segmentation and fairing surface generation in a car model. This model is defined by a simplified automotive template and relevant control points, shape parameters and segmentation parameters, which can be modified to alter the car form efficiently. With this model and the corresponding adjustment method, more than fifty various vehicle models are established in this research according to different parameters. And two methods for calculating similarity index between car models are constructed, which are suitable for brand design trend analysis and modelling design decisionmaking. 相似文献
85.
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
86.
87.
Tingen Zhu Wenping Li Qiqing Wang Yanbo Hu Kaifang Fan Jiafa Du 《Mine Water and the Environment》2020,39(1):57-67
A method to calculate the height of a water-conducting fractured zone (HWCFZ) was developed based on the plate and shell theory, and the development of the HWCFZ in bedrock and Q2l loess strata is discussed in detail. First, the subsidence-deflection curve equation of the overlying stratum is theoretically derived, and then the ultimate deflection and free space height of rock strata are calculated. Moreover, the strata tensile strain is calculated by using integral calculus. In addition, the failure state of the rock is analyzed by comparing the theoretically calculated tensile strain with the experimentally measured yield tensile strain, allowing one to attain the maximum value of HWCFZ. This approach was tested at the Jinjitan coal mine; the theoretically predicted, experimentally measured, and numerically computed maximum HWCFZ values were 189.5, 187.3, and 188.5 m, respectively, demonstrating the accuracy of the proposed method. These results are highly significant for safe and environment-friendly coal mining in northwest Shaanxi, China. 相似文献
88.
90.
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