全文获取类型
收费全文 | 6772篇 |
免费 | 706篇 |
国内免费 | 518篇 |
专业分类
电工技术 | 582篇 |
技术理论 | 2篇 |
综合类 | 888篇 |
化学工业 | 434篇 |
金属工艺 | 132篇 |
机械仪表 | 456篇 |
建筑科学 | 521篇 |
矿业工程 | 169篇 |
能源动力 | 179篇 |
轻工业 | 188篇 |
水利工程 | 198篇 |
石油天然气 | 235篇 |
武器工业 | 80篇 |
无线电 | 387篇 |
一般工业技术 | 723篇 |
冶金工业 | 182篇 |
原子能技术 | 39篇 |
自动化技术 | 2601篇 |
出版年
2024年 | 7篇 |
2023年 | 105篇 |
2022年 | 146篇 |
2021年 | 172篇 |
2020年 | 237篇 |
2019年 | 205篇 |
2018年 | 190篇 |
2017年 | 188篇 |
2016年 | 260篇 |
2015年 | 265篇 |
2014年 | 375篇 |
2013年 | 470篇 |
2012年 | 417篇 |
2011年 | 461篇 |
2010年 | 350篇 |
2009年 | 399篇 |
2008年 | 401篇 |
2007年 | 435篇 |
2006年 | 430篇 |
2005年 | 387篇 |
2004年 | 311篇 |
2003年 | 275篇 |
2002年 | 272篇 |
2001年 | 189篇 |
2000年 | 159篇 |
1999年 | 133篇 |
1998年 | 115篇 |
1997年 | 103篇 |
1996年 | 85篇 |
1995年 | 81篇 |
1994年 | 71篇 |
1993年 | 44篇 |
1992年 | 41篇 |
1991年 | 36篇 |
1990年 | 32篇 |
1989年 | 27篇 |
1988年 | 17篇 |
1987年 | 7篇 |
1986年 | 12篇 |
1985年 | 12篇 |
1984年 | 19篇 |
1983年 | 9篇 |
1982年 | 9篇 |
1981年 | 6篇 |
1980年 | 6篇 |
1979年 | 5篇 |
1978年 | 3篇 |
1977年 | 2篇 |
1961年 | 2篇 |
1956年 | 2篇 |
排序方式: 共有7996条查询结果,搜索用时 250 毫秒
1.
This paper proposes an approach to improve the performance of no-reference video quality assessment for sports videos with dynamic motion scenes using an efficient spatiotemporal model. In the proposed method, we divide the video sequences into video blocks and apply a 3D shearlet transform that can efficiently extract primary spatiotemporal features to capture dynamic natural motion scene statistics from the incoming video blocks. The concatenation of a deep residual bidirectional gated recurrent neural network and logistic regression is used to learn the spatiotemporal correlation more robustly and predict the perceptual quality score. In addition, conditional video block-wise constraints are incorporated into the objective function to improve quality estimation performance for the entire video. The experimental results show that the proposed method extracts spatiotemporal motion information more effectively and predicts the video quality with higher accuracy than the conventional no-reference video quality assessment methods. 相似文献
2.
Ziwen Wu Tianping Zhang 《International Journal of Adaptive Control and Signal Processing》2021,35(9):1768-1788
In this article, the issue of adaptive finite-time dynamic surface control (DSC) is discussed for a class of parameterized nonlinear systems with full state constraints. Using the property of logarithmic function, a one-to-one nonlinear mapping is constructed to transform a constrained system into an unconstrained system with the same structure. The nonlinear filter is constructed to replace the first-order linear filter in the traditional DSC, and the demand on the filter time constant is reduced. Based on finite-time stable theory and using modified DSC, the finite-time controller is designed via DSC. Theoretical analysis shows that all the signals in the closed-loop system are semiglobal practical finite-time stable. Furthermore, none of the states are outside the defined open set. In the end, simulation results are presented to demonstrate the effectiveness of the proposed control schemes with both linear filters and nonlinear filters. 相似文献
3.
This paper offers an overall picture of the importance of Strategic Environmental Assessment (SEA) in Romania and its opportunities and constraints. The role, scope and effectiveness of SEA in Romania are presented in two good practice examples and examined in order to highlight the strengths and weaknesses of the procedure at national and local scale. In practice, the number of SEA procedures is very high due to the legislation in force, and it is increasingly effective in decision-making about programmes and plans. SEA can be viewed as a great opportunity for the implementation of sustainable development in practice. It also continues to be an important procedural and decisional instrument for management and monitoring of socioeconomic development, spatial planning and environmental protection in Romania. 相似文献
4.
5.
Rui
Zhang Junmin Li Jianmin Jiao 《International Journal of Adaptive Control and Signal Processing》2020,34(7):919-936
This article investigates an adaptive fuzzy tracking control problem for a class of nontriangular form systems with asymmetric time-varying full state constraints. Unknown functions are approximated by the fuzzy logic systems. A domination approach is employed to tackle the nontriangular form structure. Time-varying asymmetric barrier Lyapunov functions (ABLFs) are adopted to ensure full-state constraints satisfaction. Based on the backstepping technique and time-varying ABLFs, an adaptive controller is proposed and guarantees that all the signals in the closed-loop system are ultimately bounded and the time-varying full state constraints are met. Simulation examples are presented to further demonstrate the effectiveness of the proposed approach. 相似文献
6.
Bharti M. Shinde 《热应力杂志》2020,43(10):1234-1257
Abstract In the present study, thermoelastic analysis of laminated composite and sandwich shells (cylindrical/spherical) is presented using fifth-order shear and normal deformation theory. The significant characteristic of the present theory is that it includes the effects of both transverse shear and normal deformations. The mathematical formulation uses the principle of virtual work to derive the variationally consistent governing equations and traction free boundary conditions. To obtain the static solution, these governing equations are solved by employing Navier’s solution technique. The shell is subjected to a mechanical/thermal load sinusoidally distributed over the top surface of the shell. The thermal load linearly varies across the thickness of the shell. The present results are compared with other higher-order models and 3D elasticity solution wherever possible. Thermal stresses presented in this study will act as a benchmark for the future work. 相似文献
7.
This paper presents a conjectural-variation-based equilibrium model of a single-price electricity market. The main characteristic of the model is that the market equilibrium equations incorporate the effect of the voltage constraints on the companies’ strategic behavior. A two-stage optimization model is used to solve the market equilibrium. In the first stage, an equivalent optimization problem is used to compute the day-ahead market clearing process. In the second stage, some generation units have to modify their active and reactive power in order to meet the technical constraints of the transmission network. These generation changes are determined by computing an AC optimal power flow. 相似文献
8.
探讨桑叶-苦瓜混合粉对正常小鼠血糖、血脂、抗氧化能力的影响,为评价桑叶-苦瓜混合粉是否适用于正常人群提供参考。用不同质量浓度的桑叶-苦瓜混合液灌胃正常小鼠30 d,测定小鼠体质量、血糖浓度、糖耐量、脂代谢和抗氧化的相关指标。结果表明:与对照组比较,桑叶-苦瓜混合粉显著抑制正常小鼠体质量增加,随灌胃质量浓度增加该作用趋于平稳;当灌胃0.20 g/mL桑叶-苦瓜混合粉时,对血糖浓度无明显影响,雌、雄小鼠血糖曲线下面积下降率分别为14.18%、15.69%,肝糖原含量分别增加1.93、1.98倍;血清总胆固醇浓度分别下降17.19%、18.92%,甘油三酯浓度分别下降15.00%、16.79%,低密度脂蛋白胆固醇浓度分别下降41.67%、45.83%,高密度脂蛋白胆固醇浓度分别上升64.52%、72.22%;肝脏丙二醛含量分别下降36.71%、37.73%,超氧化物歧化酶活力分别上升41.77%、48.41%,谷胱甘肽过氧化物酶活力分别上升29.04%、27.21%。桑叶-苦瓜混合粉对正常小鼠的血糖、血脂水平和抗氧化功能有调节作用,不会对健康造成不利影响。 相似文献
9.
针对工程实际中涉及非正态分布变量的封隔器胶筒密封不可靠问题,建立胶筒力学可靠性模型,提出Edgeworth级数和四阶矩的机械可靠性灵敏度数值分析方法;对密封胶筒力学模型的随机变量进行可靠性灵敏度对比分析,得出结构参数对封隔器胶筒可靠性的影响规律。结果表明:服从正态分布的几何尺寸比非正态分布的工作压差、密封载荷对封隔器胶筒可靠性的影响更显著,而非正态随机变量中,工作压差对胶筒密封可靠性的影响大于密封载荷的影响;随机方差灵敏度的增加,都会使胶筒趋向不可靠,但不同结构变量方差灵敏度的变化对胶筒密封可靠性的影响不尽相同。通过实例胶筒的可靠性灵敏度设计计算,验证该方法的有效性和准确性,工程应用中该方法可作为封隔器胶筒结构参数定量设计和可靠性设计的依据。 相似文献
10.