全文获取类型
收费全文 | 96927篇 |
免费 | 16677篇 |
国内免费 | 11600篇 |
专业分类
电工技术 | 6891篇 |
技术理论 | 9篇 |
综合类 | 11562篇 |
化学工业 | 2157篇 |
金属工艺 | 1394篇 |
机械仪表 | 7012篇 |
建筑科学 | 3764篇 |
矿业工程 | 2037篇 |
能源动力 | 1038篇 |
轻工业 | 1731篇 |
水利工程 | 1651篇 |
石油天然气 | 3287篇 |
武器工业 | 1317篇 |
无线电 | 19593篇 |
一般工业技术 | 6205篇 |
冶金工业 | 1345篇 |
原子能技术 | 943篇 |
自动化技术 | 53268篇 |
出版年
2024年 | 268篇 |
2023年 | 1590篇 |
2022年 | 3042篇 |
2021年 | 3833篇 |
2020年 | 3898篇 |
2019年 | 3070篇 |
2018年 | 2783篇 |
2017年 | 3530篇 |
2016年 | 3899篇 |
2015年 | 4740篇 |
2014年 | 6963篇 |
2013年 | 6331篇 |
2012年 | 7986篇 |
2011年 | 8269篇 |
2010年 | 6757篇 |
2009年 | 6651篇 |
2008年 | 7242篇 |
2007年 | 7961篇 |
2006年 | 6552篇 |
2005年 | 5828篇 |
2004年 | 4815篇 |
2003年 | 3970篇 |
2002年 | 3042篇 |
2001年 | 2372篇 |
2000年 | 1901篇 |
1999年 | 1409篇 |
1998年 | 1108篇 |
1997年 | 951篇 |
1996年 | 755篇 |
1995年 | 674篇 |
1994年 | 550篇 |
1993年 | 410篇 |
1992年 | 311篇 |
1991年 | 284篇 |
1990年 | 241篇 |
1989年 | 181篇 |
1988年 | 153篇 |
1987年 | 107篇 |
1986年 | 101篇 |
1985年 | 125篇 |
1984年 | 95篇 |
1983年 | 105篇 |
1982年 | 82篇 |
1981年 | 53篇 |
1980年 | 26篇 |
1979年 | 39篇 |
1978年 | 15篇 |
1977年 | 22篇 |
1976年 | 14篇 |
1959年 | 13篇 |
排序方式: 共有10000条查询结果,搜索用时 17 毫秒
1.
To benefit from recent advances in modeling and computational algorithms,as well as the availability of new covariance data,sensitivity and uncertainty analyses are needed to quantify the impact of uncertain sources on the design parameters of small prismatic high-temperature gas-cooled reactors(HTGRs).In particular,the contribution of nuclear data to the keff uncertainty is an important part of the uncertainty analysis of small-sized HTGR physical calculations.In this study,a small-sized HTGR designed by China Nuclear Power Engineering Co.,Ltd.was selected for keff uncertainty analysis during full lifetime burnup calculations.Models of the cold zero power(CZP)condition and full lifetime burnup process were constructed using the Reactor Monte Carlo Code RMC for neutron transport calculation,depletion calculation,and sensitivity and uncertainty analysis.For the sensitivity analysis,the Contribution-Linked eigenvalue sensitivity/Uncertainty estimation via Track length importance Characterization(CLUTCH)method was applied to obtain sensitive infor-mation,and the"sandwich"method was used to quantify the keff uncertainty.We also compared the keff uncertainties to other typical reactors.Our results show that 235U is the largest contributor to keff uncertainty for both the CZP and depletion conditions,while the contribution of 239Pu is not very significant because of the design of low discharge burnup.It is worth noting that the radioactive capture reaction of 28Si significantly contributes to the keff uncer-tainty owing to its specific fuel design.However,the keff uncertainty during the full lifetime depletion process was relatively stable,only increasing by 1.12%owing to the low discharge burnup design of small-sized HTGRs.These numerical results are beneficial for neutronics design and core parameters optimization in further uncertainty prop-agation and quantification study for small-sized HTGR. 相似文献
2.
Recently, single image super-resolution (SISR) has been widely applied in the fields of underwater robot vision and obtained remarkable performance. However, most current methods generally suffered from the problem of a heavy burden on computational resources with large model sizes, which limited their real-world underwater robotic applications. In this paper, we introduce and tackle the super resolution (SR) problem for underwater robot vision and provide an efficient solution for near real-time applications. We present a novel lightweight multi-stage information distillation network, named MSIDN, for better balancing performance against applicability, which aggregates the local distilled features from different stages for more powerful feature representation. Moreover, a novel recursive residual feature distillation (RRFD) module is constructed to progressively extract useful features with a modest number of parameters in each stage. We also propose a channel interaction & distillation (CI&D) module that employs channel split operation on the preceding features to produce two-part features and utilizes the inter channel-wise interaction information between them to generate the distilled features, which can effectively extract the useful information of current stage without extra parameters. Besides, we present USR-2K dataset, a collection of over 1.6K samples for large-scale underwater image SR training, and a testset with an additional 400 samples for benchmark evaluation. Extensive experiments on several standard benchmark datasets show that the proposed MSIDN can provide state-of-the-art or even better performance in both quantitative and qualitative measurements. 相似文献
3.
4.
This paper analyses the perception of Artificial Intelligence (AI) by individuals in Spain and the factors associated with it. It uses data from 6308 individuals from a 2018 Spanish survey. A binary logit regression model is formulated and estimated for the attitude towards robots and AI and its possible determinants. As main results are that a gender gap is detected, and that people have a negative attitude if they are not interested in scientific discoveries and technological developments and if AI and robots are not useful at work. 相似文献
5.
6.
7.
为了解决机器人辅助在线检测系统示教过程中效率低、人为干预多的问题,针对孔类特征,提出一种通过处理光刀图像获取机器人位姿纠正参数的方法。在该方法中,纠偏过程按照将图像光刀线调整为水平方向、将被测特征调整至图像中央、根据不同特征调整最优扫描方向3个步骤进行。根据光刀图像可以求出测量坐标系与被测特征的位姿关系,并得到该位姿与理想测量位姿的偏差。经过坐标变换即可得到在机器人基坐标系下的调整参数。另外,可利用电脑控制机器人运动,从而实现了纠偏过程的自动化。实验结果表明,该方法可将初始的示教位姿修正为理想位姿,且比传统方式效率更高。 相似文献
8.
The ways in which environmental priorities are framed are varied and influenced by political forces. One technological advance--the proliferation of government open data portals (ODPs)--has the potential to improve governance through facilitating access to data. Yet it is also known that the data hosted on ODPs may simply reflect the goals and interests of multiple levels of political power. In this article, I use traditional statistical correlation and regression techniques along with newer natural language processing and machine learning algorithms to analyze the corpus of datasets hosted on government ODPs (total: 49,066) to extract patterns that relate scales of governance and political liberalism/conservatism to the priorities and meaning attached to environmental issues. I find that state-level and municipal-level ODPs host different categories of environmental datasets, with municipal-level ODPs generally hosting more datasets pertaining to services and amenities and state-level ODPs hosting more datasets pertaining to resource protection and extraction. Stronger trends were observed for the influences of political conservatism/liberalism among state-level ODPs than for municipal-level ODPs. 相似文献
9.
10.
According to the circle-packing theorem, the packing efficiency of a hexagonal lattice is higher than an equivalent square tessellation. Consequently, in several contexts, hexagonally sampled images compared to their Cartesian counterparts are better at preserving information content. In this paper, novel mapping techniques alongside the wavelet compression scheme are presented for hexagonal images. Specifically, we introduce two tree-based coding schemes, referred to as SBHex (spirally-mapped branch-coding for hexagonal images) and BBHex (breadth-first block-coding for hexagonal images). Both of these coding schemes respect the geometry of the hexagonal lattice and yield better compression results. Our empirical results show that the proposed algorithms for hexagonal images produce better reconstruction quality at low bits per pixel representations compared to the tree-based coding counterparts for the Cartesian grid. 相似文献