全文获取类型
收费全文 | 2671篇 |
免费 | 319篇 |
国内免费 | 244篇 |
专业分类
电工技术 | 145篇 |
综合类 | 327篇 |
化学工业 | 218篇 |
金属工艺 | 92篇 |
机械仪表 | 233篇 |
建筑科学 | 215篇 |
矿业工程 | 77篇 |
能源动力 | 76篇 |
轻工业 | 103篇 |
水利工程 | 155篇 |
石油天然气 | 107篇 |
武器工业 | 23篇 |
无线电 | 342篇 |
一般工业技术 | 299篇 |
冶金工业 | 46篇 |
原子能技术 | 24篇 |
自动化技术 | 752篇 |
出版年
2024年 | 10篇 |
2023年 | 53篇 |
2022年 | 82篇 |
2021年 | 107篇 |
2020年 | 100篇 |
2019年 | 103篇 |
2018年 | 76篇 |
2017年 | 96篇 |
2016年 | 113篇 |
2015年 | 112篇 |
2014年 | 205篇 |
2013年 | 163篇 |
2012年 | 212篇 |
2011年 | 236篇 |
2010年 | 165篇 |
2009年 | 152篇 |
2008年 | 177篇 |
2007年 | 188篇 |
2006年 | 157篇 |
2005年 | 127篇 |
2004年 | 135篇 |
2003年 | 80篇 |
2002年 | 67篇 |
2001年 | 61篇 |
2000年 | 50篇 |
1999年 | 50篇 |
1998年 | 24篇 |
1997年 | 18篇 |
1996年 | 15篇 |
1995年 | 16篇 |
1994年 | 12篇 |
1993年 | 10篇 |
1992年 | 13篇 |
1991年 | 7篇 |
1990年 | 12篇 |
1989年 | 6篇 |
1988年 | 1篇 |
1987年 | 4篇 |
1986年 | 3篇 |
1985年 | 3篇 |
1984年 | 1篇 |
1983年 | 2篇 |
1982年 | 2篇 |
1981年 | 1篇 |
1980年 | 3篇 |
1979年 | 1篇 |
1976年 | 3篇 |
排序方式: 共有3234条查询结果,搜索用时 50 毫秒
1.
Yigit Kazancoglu 《国际生产研究杂志》2020,58(14):4246-4266
End of life (EOL) phase of a product is receiving more attention due to increase in environmental concerns, and many studies have been conducted for value creation in EOL, focusing on concepts as remanufacturing, reuse and recycling in sustainable production manner. This study especially focuses on one of global problem, e-waste. To minimise the amount of wastes and maximise recovered materials from EOL, disassembly is one of the most important concept, associated with reuse, and balancing disassembly line in an optimal way is essential for organisations. In disassembly line balancing (DLB), not only precedence of tasks, but also risk criteria related to environment and human safety should be considered for sustainability. The aim of this study is to propose a model based on triple bottom line (TBL) dimensions, i.e. human safety, environmental safety and business criteria. To achieve sustainability in DLB, and for risk assessment in sustainable DLB, it had been decided to use a multi-criteria method, i.e. TODIM, acronym in Portuguese of ‘Tomada de Decisão Iterativa Multicritério’. The proposed model included 22 disassembly criteria categorised under TBL dimensions, which are derived from the literature. Implementation of the study was conducted for computer disassembly processes, and as a result of the study approximately 12% an improvement in cycle time was succeeded. In the long run, the integration of sustainability in disassembly operations may contribute to the competitive advantage of the company in terms of differentiation and corporate image by achieving business, environment and human targets simultaneously. 相似文献
2.
The paper considers the problem of stabilization of systems possessing a multiple zero eigenvalue at the origin. The controller that we propose, uses multiple delayed measurements instead of derivative terms. Doing so, we increase the performances of the closed loop in presence of system uncertainties and/or noisy measurements. The problem formulation and the analysis is presented through a classical engineering problem which is the stabilization of an inverted pendulum on a cart moving horizontally. On one hand, we perform a nonlinear analysis of the center dynamics described by a three dimensional system of ordinary differential equations with a codimension-three triple zero bifurcation. On the other hand, we present the complementary stability analysis of the corresponding linear time invariant system with two delays describing the behavior around the equilibrium. The aim of this analysis is to characterize the possible local bifurcations. Finally, the proposed control scheme is numerically illustrated and discussed. 相似文献
3.
This paper presents an adaptive backstepping-based multilevel approach for the first time to control nonlinear interconnected systems with unknown parameters. The system consists of a nonlinear controller at the first level to neutralize the interaction terms, and some adaptive controllers at the second level, in which the gains are optimally tuned using genetic algorithm. The presented scheme can be used in systems with strong couplings where completely ignoring the interactions leads to problems in performance or stability. In order to test the suitability of the method, two case studies are provided: the uncertain double and triple coupled inverted pendulums connected by springs with unknown parameters. The simulation results show that the method is capable of controlling the system effectively, in both regulation and tracking tasks. 相似文献
4.
Structures of grain boundaries and triple line junctions in nanocrystalline materials are of interest owing to large fractions
of atoms in nanocrystalline materials being at these interfacial positions. Grain boundary and triple line junction structures
in nanocrystalline palladium have been studied using high-resolution transmission electron microscopy (HRTEM). The main micro
structural features observed include the varying atomic structures of grain boundaries and the presence of disordered regions
at triple line junctions. Also, there is variation in lattice parameters in different nanocrystalline grains. Geometric phase
analysis is used to quantify atomic displacements within nanocrystalline grains. Displacement fields thus detected indicate
links to the interface structures. 相似文献
5.
为了研究Furuta摆在倒立点附近的稳定控制问题,采用基于T-S模糊模型的一类连续模糊动态系统控制方法,首次进行Furuta摆的模糊状态空间建模,并采用模糊切换的思想,设计了Furuta摆在倒立点附近的稳定控制器,进而分析了系统稳定性。与已有的方法相比,该方法的优点是稳定区域大、调节时间短。数字仿真结果验证了方法的有效性。 相似文献
6.
综合应用地震属性、测井数据反演储层参数 总被引:4,自引:0,他引:4
本文研究了样点地震属性的特征提取,利用BP神经网络建立测井声波时差和地震属性的非线性映射关系。采用距离加权平均对研究区所有井的反演结果进行外推。为了提高分辨率和计算结果的准确性,详细分析、研究了适合于地震信号分解和重构的小波,以及测井声波时差和地震波阻抗与层界面的关系。最后,对反演的声波时差资料进行界面影响校正,进而计算出较符合实际情况的孔隙率参数。经已知井和新钻井验证,计算结果和实际情况相一致,效果令人满意。 相似文献
7.
8.
Marie-Claude Druguet David E. Zeitoun 《Computers & Fluids》2003,32(4):515-533
Numerical simulations are investigated to describe precisely the shock wave reflections in supersonic steady air flow field. The main objectives are to study the influence of the wedge trailing edge corner angle, of the numerical methods and of the viscous effects on the shock wave reflections and on the hysteresis behavior. The computations are done with different MUSCL-TVD finite volume schemes and the corresponding results are compared. The flow viscosity is also taken into account and comparisons are made between inviscid and viscous flow simulations. The results display the non-negligible influence of the numerical scheme accuracy on the results, mainly on the position and height of the Mach stem, and the relatively weak influence of the flow viscosity on these parameters. Comparisons between numerical results and experimental data have also been done and a good agreement is only observed for small wedge angles mainly due to the three-dimensional effects in the experimental setup. 相似文献
9.
在川渝地区,钻定向井、水平井必然要面对地层岩性变化大、硬度高等复杂地质情况,常常会遇到因井下复杂、事故、修改地质目标等原因需要填井侧钻。侧钻的方法不同,侧钻的成功率和效率差异很大。文中分析了川渝地区近几年硬地层定向井、水平井侧钻效率不高、有时甚至失败的原因,归纳总结了近几年常用的几种侧钻方法的施工效果,提出要根据具体条件灵活应用这几种侧钻方法。 相似文献
10.
For the investigations of the gas-liquid phase equilibria, a new apparatus has been developed capable of simultaneously determining the pressure and the liquid and vapor densities using Archimedes' principle. The relative measurement uncertainties of the liquid and vapor densities of R134a (purity, 99.999%) at 313 K are 2×10–4 and 7×10–4, respectively (95% confidence level). For the measurements in the liquid region along nine quasi-isochores at pressures up to 5 MPa, an isochoric apparatus was used. The relative measurement uncertainty ofpv/(RT) is less than 1×10–3. In addition to the investigation of the (p, v, T) properties, the temperature and pressure at the triple point and the vapor pressure between the triple point and 265 K were measured. On the basis of these data, a vapor pressure correlation has been developed that reproduces the measured vapor pressures within the uncertainty of measurement. The results of our measurements are compared with a fundamental equation for R134a, which is based on the measurements of other research groups.Paper presented at the Twelfth Symposium on Thermophysical Properties, June 19–24, 1994, Boulder, Colorado, U.S.A. 相似文献