全文获取类型
收费全文 | 18943篇 |
免费 | 1786篇 |
国内免费 | 333篇 |
专业分类
电工技术 | 4903篇 |
综合类 | 1102篇 |
化学工业 | 853篇 |
金属工艺 | 884篇 |
机械仪表 | 1860篇 |
建筑科学 | 800篇 |
矿业工程 | 160篇 |
能源动力 | 6130篇 |
轻工业 | 152篇 |
水利工程 | 1094篇 |
石油天然气 | 406篇 |
武器工业 | 112篇 |
无线电 | 318篇 |
一般工业技术 | 899篇 |
冶金工业 | 504篇 |
原子能技术 | 85篇 |
自动化技术 | 800篇 |
出版年
2024年 | 96篇 |
2023年 | 259篇 |
2022年 | 436篇 |
2021年 | 532篇 |
2020年 | 551篇 |
2019年 | 445篇 |
2018年 | 380篇 |
2017年 | 522篇 |
2016年 | 719篇 |
2015年 | 787篇 |
2014年 | 1427篇 |
2013年 | 919篇 |
2012年 | 1426篇 |
2011年 | 1649篇 |
2010年 | 1155篇 |
2009年 | 1119篇 |
2008年 | 988篇 |
2007年 | 1245篇 |
2006年 | 1155篇 |
2005年 | 850篇 |
2004年 | 742篇 |
2003年 | 696篇 |
2002年 | 514篇 |
2001年 | 473篇 |
2000年 | 423篇 |
1999年 | 356篇 |
1998年 | 217篇 |
1997年 | 169篇 |
1996年 | 175篇 |
1995年 | 145篇 |
1994年 | 98篇 |
1993年 | 85篇 |
1992年 | 58篇 |
1991年 | 54篇 |
1990年 | 51篇 |
1989年 | 54篇 |
1988年 | 35篇 |
1987年 | 21篇 |
1986年 | 8篇 |
1985年 | 2篇 |
1984年 | 3篇 |
1983年 | 2篇 |
1982年 | 2篇 |
1981年 | 6篇 |
1980年 | 6篇 |
1979年 | 5篇 |
1978年 | 1篇 |
1977年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
991.
《Thin》2015
Liquid storage steel tanks are vertical above-ground cylindrical shells and as typical thin-walled structures, they are very sensitive to buckling under wind loads, especially when they are empty or at low liquid level. Previous studies revealed discrepancies in buckling resistance of empty tanks between the design method proposed by the American Standard API 650 and the analytical formulas recommended by the European Standard EN1993-1-6 and EN1993-4-2. This study presents a comparison between the provisions of current design codes by performing all types of numerical buckling analyses recommended by Eurocodes (i.e. LBA-linear elastic bifurcation analysis, GNA-geometrically nonlinear elastic analysis of the perfect tank and GNIA-geometrically nonlinear elastic analysis of the imperfect tank). Such analyses are performed in order to evaluate the buckling resistance of two existing thin-walled steel tanks, with large diameters and variable wall thickness. In addition, a discussion is unfolded about the differences between computational and analytical methods and the conservatism that the latter method imposes. An influence study on the geometric imperfections and the boundary conditions is also conducted. Investigation on the boundary conditions at the foot of the tank highlights the sensitivity to the fixation of the vertical translational degree of freedom. Further, it is indicated that the imperfection magnitude recommended by the EN1993-1-6 is extremely unfavorable when applied to large diameter tanks. Comments and conclusions achieved could be helpful in order to evaluate the safety of the current design codes and shed more light towards the most accurate one. 相似文献
992.
In this work, we propose an index that allows a public authority to order different projects for the construction of onshore wind energy plants and that explicitly takes into account their environmental quality. Wind farm projects are defined as vectors of four attributes: the technical properties of each project, its social impact, its environmental impact, and the share of earnings that proponents offer to the collectivity in compensation for the negative externalities of the wind plant. We define an absolute index that allows the ordering of different proposals and evaluation of the acceptability of each project, providing the monetary value of each point and inducing a truthful revelation of firms' private information. Moreover, we calibrate the index on the basis of data referring to wind plants in Southern Italy and derive the corresponding iso-scoring curves. 相似文献
993.
In this work, a micro wind turbine will be designed and built for a series of wind tunnel tests (rotor dynamics and Wind Turbine (WT) start-up velocity). Its design stems from an original numerical code, developed by the authors, based on the Blade Element Momentum (BEM) Theory. 相似文献
994.
High-penetration renewable energy-based generators (REGs) in distribution systems have increased the importance of impact assessment involving these systems. This assessment focuses on power quality (PQ) and compatibility between REGs and existing system components. Electric vehicle (EV) technology has also recently achieved a substantial market share. This technology requires the development of charging stations similar to current petroleum fuelling stations in the near future. Thus, the effect of EV stations (EVSs) on PQ must also be considered. This study presents a PQ analysis on the effects of high-penetration EVS and REG systems, including wind turbines, grid-connected photovoltaics (PVs), and fuel cell (FC) power generation units on a modified 16-bus distribution system under different loading and weather conditions. All data on EVS, wind farm, PV, and FC units as well as weather conditions presented in this paper were collected from different power companies and the Malaysian Meteorological Department. The system is modelled and simulated using the MATLAB/Simulink software to study the effects of these technologies on system performances at various penetration levels. Simulation results indicated that the presence of high-penetration EVSs and REGs can cause severe PQ problems such as frequency and voltage fluctuations, voltage drop, harmonic distortion and power factor reduction. 相似文献
995.
In the case of a flexible container subjected to the wind loads, the container has a high susceptibility to flow-induced deformations and vibrations. This paper presents the work of numerical simulations about its dynamic responses under horizontal wind actions. The container body is assumed to be a Belytschko-Tsay membrane, which includes nonlinearities. Water movement and sloshing are modelled using multi-material ALE method. Interaction between the container and fluid is studied by penalty method, and the large eddy simulation (LES) method is used for simulating turbulence. This paper analyses the problems in container stability, deformation and stress distribution. The results indicate that the reinforcement belt cannot only reduce the container stress but also improve container stability in the wind domain. The maximum stress positions are on the lee side corner of the container. Variation in container vertical acceleration is much larger than the horizontal one. 相似文献
996.
主要根据多年来大型化工企业热电联产装置运行管理过程中出现的典型问题进行详细地分析,介绍了某省煤化集团大型化工企业锅炉、汽轮机、除尘器等设备事故的处理经验,以及实际运行操作的注意事项,以达到提高司炉、司机、除尘操作水平的目的。 相似文献
997.
998.
本文对门式刚架轻型房屋钢结构的荷载取值、结构设计和计算、优化设计中应引起重视的问题做一定的分析、探讨,供设计同行参考。 相似文献
999.
This paper analyses the deployment of wind power and the related local controversies using actor-network theory (ANT). ANT provides conceptual instruments for a fine-tuned analysis of the contingencies that condition a project’s success or failure by focusing on the micro-decisions that intertwine the material aspects of the technology, the site where it is implemented, the participation process, and the social relations in which they are embedded. By considering controversies as alternative efforts of competing networks of actors to ‘frame’ the reality and enroll others, ANT sheds light on the complex and political nature of planning a wind farm project, insofar as it consist in aligning material and human behaviours into a predictable scenario. ‘Overflows’ occur when actors do not conform to expectations, adopt conflicting positions and develop their own interpretations of the project, thus obliging designers to adapt their frames and change their plans. To demonstrate this framework, we apply it to the case of a wind farm project in the South of France, near Albi. Our analysis suggests a new approach to examining wind power projects in terms of the interaction between globally circulating technologies, unique characteristics of the site, the participation process and the social dynamics that emerge when these are combined. 相似文献
1000.
During heat treatment process, the distortion behavior inevitably appears in hydraulic turbine blade castings. In this research, a technology was developed for real-time measurement of the distortion in hydraulic turbine blade castings at the still air cooling and forced air cooling stages during heat treatment process. The method was used to measure the distortion behavior at the cooling stages in both normalizing and tempering processes. At the normalization, the distortion at the blade corner near outlet side undergoes four stages with alternating bending along positive and negative directions. At the tempering stage, the distortion could be divided into two steps. The temperature difference between the two surfaces of blade casting was employed to analyze the distortion mechanism. The measured results could be applied to guide the production, and the machining allowance could be reduced by controlling the distortion behavior. 相似文献