全文获取类型
收费全文 | 21652篇 |
免费 | 2005篇 |
国内免费 | 1199篇 |
专业分类
电工技术 | 3384篇 |
技术理论 | 1篇 |
综合类 | 2482篇 |
化学工业 | 826篇 |
金属工艺 | 386篇 |
机械仪表 | 1945篇 |
建筑科学 | 3115篇 |
矿业工程 | 759篇 |
能源动力 | 616篇 |
轻工业 | 445篇 |
水利工程 | 625篇 |
石油天然气 | 901篇 |
武器工业 | 585篇 |
无线电 | 2464篇 |
一般工业技术 | 2042篇 |
冶金工业 | 729篇 |
原子能技术 | 267篇 |
自动化技术 | 3284篇 |
出版年
2024年 | 50篇 |
2023年 | 202篇 |
2022年 | 338篇 |
2021年 | 449篇 |
2020年 | 528篇 |
2019年 | 440篇 |
2018年 | 385篇 |
2017年 | 529篇 |
2016年 | 661篇 |
2015年 | 696篇 |
2014年 | 1252篇 |
2013年 | 1202篇 |
2012年 | 1451篇 |
2011年 | 1682篇 |
2010年 | 1249篇 |
2009年 | 1281篇 |
2008年 | 1249篇 |
2007年 | 1564篇 |
2006年 | 1455篇 |
2005年 | 1202篇 |
2004年 | 1111篇 |
2003年 | 1001篇 |
2002年 | 797篇 |
2001年 | 719篇 |
2000年 | 660篇 |
1999年 | 494篇 |
1998年 | 377篇 |
1997年 | 331篇 |
1996年 | 290篇 |
1995年 | 235篇 |
1994年 | 181篇 |
1993年 | 122篇 |
1992年 | 117篇 |
1991年 | 71篇 |
1990年 | 84篇 |
1989年 | 53篇 |
1988年 | 60篇 |
1987年 | 52篇 |
1986年 | 22篇 |
1985年 | 25篇 |
1984年 | 26篇 |
1983年 | 25篇 |
1982年 | 8篇 |
1981年 | 10篇 |
1965年 | 9篇 |
1964年 | 12篇 |
1959年 | 10篇 |
1957年 | 10篇 |
1956年 | 9篇 |
1955年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 187 毫秒
1.
2.
针对某在建矿山深井开拓方案探索需求,通过对胶带运输系统发展应用情况介绍和胶带运输系统运输特性影响因素分析,并结合深井开拓胶带斜井方案与竖井加胶带斜井方案投资经济性比较,以及对胶带运输系统在运行过程中关键问题的分析和讨论,得出随着胶带运输技术的不断发展,在大规模深井开拓中,胶带斜井开拓将大有可为,为冶金矿山深井开拓方案选择提供决策支持。 相似文献
3.
This paper presents a stochastic performance modelling approach that can be used to optimise design and operational reliability of complex chemical engineering processes. The framework can be applied to processes comprising multiple units, including the cases where closed form process performance functions are unavailable or difficult to derive from first principles, which is often the case in practice. An interface that facilitates automated two-way communication between Matlab® and process simulation environment is used to generate large process responses. The resulting constrained optimisation problem is solved using both Monte Carlo Simulation (MCS) and First Order Reliability Method (FORM); providing a wide range of stochastic process performance measures. Adding such capabilities to traditional deterministic process simulators provides a more informed basis for selecting optimum design factors; giving a simple way of enhancing overall process reliability and cost-efficiency. Two case study systems are considered to highlight the applicability and benefits of the approach. 相似文献
4.
5.
为了提升高校实验数据处理水平,高校实验室的相关建设工作已经步入正轨,但层出不穷的信息安全问题也向高校实验室计算机网络维护工作提出了新的挑战。文章从现阶段高校实验室计算机网络的相关建设工作出发,简要论述引发网络故障的具体原因,并对其诊断技术进行探讨。 相似文献
6.
Yong Xu Yun Li Songlin Li Francis Balestra Gerard Ghibaudo Wenwu Li Yen‐Fu Lin Huabin Sun Jing Wan Xinran Wang Yufeng Guo Yi Shi Yong‐Young Noh 《Advanced functional materials》2020,30(20)
Unreliable mobility values, and particularly greatly overestimated values and severely distorted temperature dependences, have recently hampered the development of the organic transistor field. Given that organic field‐effect transistors (OFETs) have been routinely used to evaluate mobility, precise parameter extraction using the electrical properties of OFETs is thus of primary importance. This review examines the origins of the various mobilities that must be determined for OFET applications, the relevant extraction methods, and the data selection limitations, which help in avoiding conceptual errors during mobility extraction. For increased precision, the review also discusses device fabrication considerations, calibration of both the specific gate‐dielectric capacitance and the threshold voltage, the contact effects, and the bias and temperature dependences, which must actually be handled with great care but have mostly been overlooked to date. This review serves as a systematic overview of the OFET mobility extraction process to ensure high precision and will also aid in improving future research. 相似文献
7.
针对高可靠度机载多余度EWIS各组成部分寿命服从指数分布但参数未知的情况,提出采用无失效数据可靠度分析方法评估EWIS的可靠度水平。通过Monte-Carlo仿真方法对连接形式为“先并联、后串联”EWIS各组成部分寿命进行抽样,利用“最小最大值”方法获得系统寿命的抽样值,用概率纸检验法初步判断EWIS寿命是否服从威布尔分布,再用Pearson拟合优度检验法判断EWIS寿命是否服从威布尔分布。结合无故障飞行时间的样本值与EWIS寿命服从威布尔分布的假设,采用无失效数据分析方法评估EWIS的可靠度水平。研究方法对机载多余度EWIS无失效数据可靠度分析有一定的贡献。 相似文献
8.
Numerous design choices need to be made at several levels when designing high-tech products: technology, processes, architecture, components, materials… and these choices need to be made in relation to the product life cycle with the corresponding experts for each stage of the life cycle. At the same time, to ensure product sustainability, a specific focus on the future potential environmental impacts is highly recommended. In this research, an agile model is proposed to help designers make decisions while monitoring environmental performance indicators of high-tech solutions. The concept of Critical Product Life Cycle Parameters had to be introduced to facilitate the eco-design of the final product. The approach is illustrated by the Electric Vehicle Li-Ion Batteries case study. 相似文献
9.
10.
Lorena Rodríguez-López Myriam Rincón-Fontán Xanel Vecino Ana B. Moldes Jose M. Cruz 《Journal of surfactants and detergents》2020,23(1):79-90
Over the last few years, the global biosurfactant market has raised due to the increasing awareness among consumers, for the use of biological or bio-based products. Because of their composition, it can be speculated that these are more biocompatible and more biodegradable than their chemical homologous. However, at the moment, no studies exist in the literature about the biodegradability of biosurfactants. In this work, a biosurfactant contained in a crude extract, obtained from a corn wet-milling industry stream that ferments spontaneously in the presence of lactic acid bacteria, was subjected to a biodegradation study, without addition of external microbial biomass, under different conditions of temperature (5–45 °C), biodegradation time (15–55 days), and pH (5–7). For that, a Box–Behnken factorial design was applied, which allowed to predict the percentage of biodegradation for the biosurfactant contained in the crude extract, between the range of the independent variables selected in the study, obtaining biodegradation values between 3 and 80%. The percentage of biodegradation for the biosurfactant was calculated based on the increase in the surface tension of samples of the crude extract. Furthermore, it was also possible to predict the variation in t1/2 for the biosurfactant (time to achieve the 50% of biodegradation) under different conditions. 相似文献