全文获取类型
收费全文 | 4613篇 |
免费 | 741篇 |
国内免费 | 454篇 |
专业分类
电工技术 | 539篇 |
综合类 | 673篇 |
化学工业 | 405篇 |
金属工艺 | 19篇 |
机械仪表 | 114篇 |
建筑科学 | 472篇 |
矿业工程 | 63篇 |
能源动力 | 81篇 |
轻工业 | 101篇 |
水利工程 | 113篇 |
石油天然气 | 13篇 |
武器工业 | 49篇 |
无线电 | 545篇 |
一般工业技术 | 462篇 |
冶金工业 | 75篇 |
原子能技术 | 7篇 |
自动化技术 | 2077篇 |
出版年
2024年 | 49篇 |
2023年 | 130篇 |
2022年 | 196篇 |
2021年 | 253篇 |
2020年 | 274篇 |
2019年 | 245篇 |
2018年 | 209篇 |
2017年 | 181篇 |
2016年 | 225篇 |
2015年 | 248篇 |
2014年 | 324篇 |
2013年 | 345篇 |
2012年 | 353篇 |
2011年 | 350篇 |
2010年 | 296篇 |
2009年 | 333篇 |
2008年 | 323篇 |
2007年 | 329篇 |
2006年 | 279篇 |
2005年 | 211篇 |
2004年 | 146篇 |
2003年 | 116篇 |
2002年 | 115篇 |
2001年 | 53篇 |
2000年 | 36篇 |
1999年 | 20篇 |
1998年 | 23篇 |
1997年 | 20篇 |
1996年 | 20篇 |
1995年 | 12篇 |
1994年 | 7篇 |
1993年 | 11篇 |
1992年 | 12篇 |
1991年 | 7篇 |
1990年 | 5篇 |
1989年 | 5篇 |
1988年 | 2篇 |
1987年 | 6篇 |
1986年 | 2篇 |
1984年 | 2篇 |
1983年 | 3篇 |
1982年 | 3篇 |
1980年 | 3篇 |
1978年 | 3篇 |
1977年 | 2篇 |
1973年 | 2篇 |
1964年 | 2篇 |
1963年 | 3篇 |
1960年 | 4篇 |
1955年 | 2篇 |
排序方式: 共有5808条查询结果,搜索用时 15 毫秒
41.
Effects of hydrological changes on cooperation in transnational catchments: the case of the Syr Darya 总被引:1,自引:0,他引:1
Water allocation along the Syr Darya River may be affected by climate change. Here we statistically model cooperation strategies, country profits, and sensitivity of cooperation, showing that the hydrological regime affects transboundary cooperation. Climate change in the twenty-first century may reduce glacial cover, and reducing stream flows, decreasing chances of cooperation and potentially raising conflicts. Comparison with other transboundary catchments in Central Asia indicates moderate-to-high risk of conflicts for the Syr Darya. A template is provided for assessment of the stability of cooperation in the Syr Darya basin, and in catchments similarly dependent on water availability. 相似文献
42.
Monte Carlo (MC) constitutes an important class of methods for the numerical solution of the general dynamic equation (GDE) in particulate systems. We compare four such methods in a series of seven test cases that cover typical particulate mechanisms. The four MC methods studied are: time-driven direct simulation Monte Carlo (DSMC), stepwise constant-volume Monte Carlo, constant number Monte Carlo, and multi-Monte Carlo (MMC) method. These MC's are introduced briefly and applied numerically to simulate pure coagulation, breakage, condensation/evaporation (surface growth/dissolution), nucleation, and settling (deposition). We find that when run with comparable number of particles, all methods compute the size distribution within comparable levels of error. Because each method uses different approaches for advancing time, a wider margin of error is observed in the time evolution of the number and mass concentration, with event-driven methods generally providing better accuracy than time-driven methods. The computational cost depends on algorithmic details but generally, event-driven methods perform faster than time-driven methods. Overall, very good accuracy can be achieved using reasonably small numbers of simulation particles, O(103), requiring computational times of the order 102−103 s on a typical desktop computer. 相似文献
43.
鲁兵 《电脑编程技巧与维护》2014,(14):127-127
阐述了中职学校美工设计课程在教学设置中存在的问题,提出了相应的观点,论述了在中职学校美工设计课程的定位,培养具有一定综合素质和一技之长的中职学生。同时指出了传统的的教学课程结构已经不适应当今社会对人才培养目标的需要,必须进行课程改革,以适应社会发展的需求。 相似文献
44.
秦旭 《电脑编程技巧与维护》2014,(12):144+147-144,147
中职类学校的游戏设计类专业,应该让学生学习些简单的游戏引擎设计,让学生能全面感知游戏的构成,从而有利于学生的就业和未来的再学习。 相似文献
45.
Integrated Game Based Guidance with Nonlinear Autopilot Design for Maneuvering Target Interception
下载免费PDF全文
![点击此处可从《Asian journal of control》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Li‐Chen Fu 《Asian journal of control》2014,16(2):431-440
The integrated game theory based guidance law with nonlinear autopilot (GGNA) system is presented in this paper. The guidance law is designed based on linear differential game theory while considering the motion of the target in 3‐D space such that the distance between the missile and the target is minimized faster than before. The autopilot system based on quaternion representation is developed using sliding mode control method to generate the attitude command. The stability of the integrated guidance and nonlinear autopilot system is analyzed with Lyapunov stability theory. In addition, this research assumes wingless missiles in our context in order to reduce the nonlinear effect from the aerodynamics. Furthermore, in order to extend the operation range of missiles from endo‐atmosphere to exo‐atmosphere, the missiles are equipped with Thrust Vector Control (TVC) mechanisms and Divert Control System (DCS). Finally, extensive simulations incorporating aerodynamic models are demonstrated to verify the validity of the proposed integrated guidance/autopilot systems. Moreover, the simulation results reveal that the mission of intercepting a maneuvering target is successfully accomplished. 相似文献
46.
In this contribution, a model reduction technique for population balance systems describing particulate processes is presented. This technique is based on integral approximation and allows the derivation of highly accurate moment models. In contrast to other model reduction methods which can be found in literature, this integral approximation technique can be applied for arbitrarily complex phenomena specifications. The applicability of the presented method will be demonstrated for different example processes by comparing the dynamic behavior of the original population balance models with those of the derived reduced models of moments. 相似文献
47.
Cláudio P. Ribeiro Jr. 《Chemical engineering science》2004,59(12):2363-2377
The study of bubble size distributions in direct-contact evaporators was addressed both theoretically and experimentally. Recently developed models for calculating bubble coalescence and breakage frequencies in isothermal bubble columns were adapted to the population balance equation using the bubble mass as the internal coordinate which was discretized using an expansion of the number density function by impulse functions. A sparger model was developed based on experimental data for a non-coalescing system and using bubble formation models for isothermal and non-isothermal conditions. Bubble size distributions in a direct-contact evaporator operating in the quasi-steady-state regime for four different gas superficial velocities, including the homogeneous and heterogeneous regimes, together with the sparger model, were used for estimating the three empirical parameters from the population balance model, which were observed to be functions of the gas superficial velocity. In all cases considered, the population balance model fitted the experimental data rather well and the regressed parameters exhibit the physically expected behavior with changes in the gas superficial velocity. 相似文献
48.
研究了由风险中性制造商和风险规避零售商构成的供应链创新投资问题。通过运用条件风险价值(CVaR)对企业的风险偏好进行测度,构建了分散供应链和集中供应链两种情况下的企业决策模型,并根据数值实验对模型作了进一步的分析。研究结果表明:零售商越担心风险,其对创新的投入越少,并会减少销售量以应对市场风险,从而使得供应链的整体收益下降;分散供应链下的创新投入、销售量和供应链的期望收益低于集中供应链下的创新投入、销售量和供应链的期望收益。施行收益共享契约后,分散供应链下的创新投入和销售量达到了集中供应链下的决策水平,制造商和零售商的期望收益均得到提高。 相似文献
49.
50.
基于Q学习的DDoS攻防博弈模型研究 总被引:1,自引:0,他引:1
新形势下的DDoS攻防博弈过程和以往不同,因此利用现有的方法无法有效地评估量化攻防双方的收益以及动态调整博弈策略以实现收益最大化。针对这一问题,设计了一种基于Q学习的DDoS攻防博弈模型,并在此基础上提出了模型算法。首先,通过网络熵评估量化方法计算攻防双方收益;其次,利用矩阵博弈研究单个DDoS攻击阶段的攻防博弈过程;最后,将Q学习引入博弈过程,提出了模型算法,用以根据学习效果动态调整攻防策略从而实现收益最大化。实验结果表明,采用模型算法的防御方能够获得更高的收益,从而证明了算法的可用性和有效性。 相似文献