全文获取类型
收费全文 | 124773篇 |
免费 | 10855篇 |
国内免费 | 7319篇 |
专业分类
电工技术 | 11777篇 |
技术理论 | 21篇 |
综合类 | 15189篇 |
化学工业 | 6636篇 |
金属工艺 | 2899篇 |
机械仪表 | 7707篇 |
建筑科学 | 21741篇 |
矿业工程 | 5192篇 |
能源动力 | 4056篇 |
轻工业 | 3114篇 |
水利工程 | 6295篇 |
石油天然气 | 3526篇 |
武器工业 | 1358篇 |
无线电 | 9798篇 |
一般工业技术 | 8953篇 |
冶金工业 | 6818篇 |
原子能技术 | 704篇 |
自动化技术 | 27163篇 |
出版年
2024年 | 277篇 |
2023年 | 1272篇 |
2022年 | 2413篇 |
2021年 | 3025篇 |
2020年 | 3310篇 |
2019年 | 2466篇 |
2018年 | 2464篇 |
2017年 | 3133篇 |
2016年 | 3854篇 |
2015年 | 4152篇 |
2014年 | 9510篇 |
2013年 | 8088篇 |
2012年 | 9461篇 |
2011年 | 9754篇 |
2010年 | 7622篇 |
2009年 | 8104篇 |
2008年 | 7972篇 |
2007年 | 9738篇 |
2006年 | 8329篇 |
2005年 | 6961篇 |
2004年 | 5867篇 |
2003年 | 5216篇 |
2002年 | 4150篇 |
2001年 | 3267篇 |
2000年 | 2710篇 |
1999年 | 2051篇 |
1998年 | 1507篇 |
1997年 | 1203篇 |
1996年 | 984篇 |
1995年 | 831篇 |
1994年 | 657篇 |
1993年 | 487篇 |
1992年 | 364篇 |
1991年 | 286篇 |
1990年 | 226篇 |
1989年 | 245篇 |
1988年 | 171篇 |
1987年 | 85篇 |
1986年 | 96篇 |
1985年 | 107篇 |
1984年 | 112篇 |
1983年 | 110篇 |
1982年 | 49篇 |
1981年 | 31篇 |
1980年 | 34篇 |
1979年 | 36篇 |
1978年 | 12篇 |
1977年 | 18篇 |
1961年 | 11篇 |
1959年 | 13篇 |
排序方式: 共有10000条查询结果,搜索用时 266 毫秒
31.
32.
Hitoshi Muta 《Journal of Nuclear Science and Technology》2019,56(5):367-368
Recent activities in the field of Nuclear Operational Management and Nuclear Safety Engineering, the studies related to risk analysis methodology, design, and operational management, physical phenomena, and emergency preparedness and nuclear security, have been progressed. Especially, ‘risk analysis methodology’ and ‘design and operational management’ are the main categories of the field, in which more than half of published articles on Journal of Nuclear Science and Technology are related to these categories. 相似文献
33.
Moritz Raab Simon Maier Ralph-Uwe Dietrich 《International Journal of Hydrogen Energy》2021,46(21):11956-11968
A large-scale point to point hydrogen transport is one strategy for a prospective energy import scenario for certain countries. The case for a hydrogen transport from Australia to Japan has been addressed in several studies. However, most studies lack transparency and detailed insights into the made assumptions thus a fair evaluation of different transport pathways is challenging. To address this issue, we developed a model where a large-scale point to point hydrogen transport of liquid hydrogen is compared with the transport via liquid organic hydrogen carrier (LOHC), namely via methyl cyclohexane and hydrogenated dibenzyl toluene. We analyzed, where energy is required along the different pathways, where hydrogen losses do occur and how the costs are put together. Furthermore, the influence of hydrogen feed costs is also considered. For hydrogen production costs of 5 €2018/kgH2 the total delivery costs are in the range of 6.40– 8.10 €2018/kgH2. 相似文献
34.
Previous experimental results indicate that the humidification conditions at the anode have an impact on the liquid water distribution in the cathode gas diffusion layer. Numerical simulations are developed to reproduce and analyze this effect. Results consistent with the experimental results are first obtained by playing with the partition coefficients of an advanced pore network model computing the liquid water formation and transfer in the cathode gas diffusion layer (GDL) for a large range of operating conditions. Then, a model for the full anode – cathode assembly is developed by combining the pore network model of the cathode GDL and a 1D model describing the heat and water transfer in the various components of the anode-cathode assembly. This enables one to generalize the dry – wet regime diagram introduced in a previous work by incorporating the effect of the humidity condition at the anode. 相似文献
35.
Journal of Computer Science and Technology - DOACROSS loops are significant parts in many important scientific and engineering applications, which are generally exploited pipeline/wave-front... 相似文献
36.
Miroslav Kárný Marko Ruman 《International Journal of Adaptive Control and Signal Processing》2021,35(5):660-675
Any knowledge extraction relies (possibly implicitly) on a hypothesis about the modelled-data dependence. The extracted knowledge ultimately serves to a decision-making (DM). DM always faces uncertainty and this makes probabilistic modelling adequate. The inspected black-box modeling deals with “universal” approximators of the relevant probabilistic model. Finite mixtures with components in the exponential family are often exploited. Their attractiveness stems from their flexibility, the cluster interpretability of components and the existence of algorithms for processing high-dimensional data streams. They are even used in dynamic cases with mutually dependent data records while regression and auto-regression mixture components serve to the dependence modeling. These dynamic models, however, mostly assume data-independent component weights, that is, memoryless transitions between dynamic mixture components. Such mixtures are not universal approximators of dynamic probabilistic models. Formally, this follows from the fact that the set of finite probabilistic mixtures is not closed with respect to the conditioning, which is the key estimation and predictive operation. The paper overcomes this drawback by using ratios of finite mixtures as universally approximating dynamic parametric models. The paper motivates them, elaborates their approximate Bayesian recursive estimation and reveals their application potential. 相似文献
37.
随着煤矿向深部发展,矿井动力灾害既表现出冲击地压的部分特征,又表现出冒顶的部分特征。2种典型的灾害打破以往冒顶与冲击地压的发生具有一种互为逆向性的认知规律,在深部高应力煤巷,特别是留顶煤巷道中出现了相互诱导、复合发生的新灾害类型。在总结山东、山西和新疆矿区典型巷道冲击致顶板(顶煤)动力灾害特征的基础上,提出了深部巷道冲击地压与冒顶复合灾害的概念、机理与分类,指出复合灾害机理关键点在于揭示巷道整体系统和破碎区子系统的稳定原理及其2者间的相互影响。建立了巷道发生复合灾害的力学模型,根据扰动响应失稳判据,提出并得到了巷道发生复合灾害的临界应力Pcr、临界软化区半径ρcr和最大容许采扰应力增量σmax,厘清了灾害发生的主控因素,分析了煤岩冲击倾向指数K、支护强度ps、巷道半径ρ0、煤岩强度σc等对灾害发生的影响规律,同时阐明了围岩塑性软化、破碎深度随地应力增加的发育规律。研究结果表明,破碎发育巷道的动力失稳主体为弹性区、软化区与破碎区构成的不稳定系统,垮落主体为破碎区;稳定的破碎区提升了巷道冲击启动临界值,使其启动难度增大,但破碎区的发育又易引起顶煤垮落;巷道稳定支护是解决复合灾害的关键,科学合理支护既能有效调控围岩破碎防冒,又能提升冲击启动临界值。通过理论研究,揭示了巷道冲击地压与冒顶复合灾害的发生机理,阐明了巷道软化与破碎区及其稳控支护对深部破碎发育巷道动力灾害防治的重要性。 相似文献
38.
This article theoretically and empirically analyzes backtesting portfolio value-at-risk (VaR) with estimation risk in an intrinsically multi-variate framework. It particularly takes into account the estimation of portfolio weights in forecasting portfolio VaR and its impact on backtesting. It shows that the estimation risk from estimating portfolio weights and that from estimating the multi-variate dynamic model make the existing methods in a univariate framework inapplicable. It proposes a general theory to quantify estimation risk applicable to the present problem and suggests practitioners a simple but effective way to implement valid inference to overcome the effect of estimation risk in backtesting portfolio VaR. In particular, we apply our theory to the efficient mean-variance-skewness portfolio for a multi-variate generalized autoregressive conditional heteroscedasticity model with multi-variate general hyperbolic distributed innovations. Some Monte Carlo simulations and an empirical application demonstrate the merits of our method. 相似文献
39.
WRESTORE (Watershed Restoration Using Spatio-Temporal Optimization of Resources) is a web-based, participatory planning tool that can be used to engage with watershed stakeholder communities, and involve them in using science-based, human-guided, interactive simulation–optimization methods for designing potential conservation practices on their landscape. The underlying optimization algorithms, process simulation models, and interfaces allow users to not only spatially optimize the locations and types of new conservation practices based on quantifiable goals estimated by the dynamic simulation models, but also to include their personal subjective and/or unquantifiable criteria in the location and design of these practices. In this paper, we describe the software, interfaces, and architecture of WRESTORE, provide scenarios for implementing the WRESTORE tool in a watershed community's planning process, and discuss considerations for future developments. 相似文献
40.
An organization requires performing readiness-relevant activities to ensure successful implementation of an enterprise resource planning (ERP) system. This paper develops a novel approach to managing these interrelated activities to get ready for implementing an ERP system. The approach enables an organization to evaluate its ERP implementation readiness by assessing the degree to which it can achieve the interrelated readiness relevant activities using fuzzy cognitive maps. Based on the interrelationship degrees among the activities, the approach clusters the activities into manageable groups and prioritizes them. To help work out a readiness improvement plan, scenario analysis is conducted. 相似文献