全文获取类型
收费全文 | 5134篇 |
免费 | 657篇 |
国内免费 | 452篇 |
学科分类
工业技术 | 6243篇 |
出版年
2024年 | 19篇 |
2023年 | 52篇 |
2022年 | 97篇 |
2021年 | 109篇 |
2020年 | 165篇 |
2019年 | 135篇 |
2018年 | 142篇 |
2017年 | 167篇 |
2016年 | 200篇 |
2015年 | 175篇 |
2014年 | 321篇 |
2013年 | 290篇 |
2012年 | 412篇 |
2011年 | 477篇 |
2010年 | 339篇 |
2009年 | 333篇 |
2008年 | 357篇 |
2007年 | 435篇 |
2006年 | 337篇 |
2005年 | 321篇 |
2004年 | 257篇 |
2003年 | 219篇 |
2002年 | 167篇 |
2001年 | 152篇 |
2000年 | 121篇 |
1999年 | 85篇 |
1998年 | 54篇 |
1997年 | 54篇 |
1996年 | 37篇 |
1995年 | 39篇 |
1994年 | 43篇 |
1993年 | 23篇 |
1992年 | 21篇 |
1991年 | 21篇 |
1990年 | 11篇 |
1989年 | 5篇 |
1988年 | 7篇 |
1987年 | 6篇 |
1986年 | 2篇 |
1985年 | 5篇 |
1983年 | 2篇 |
1981年 | 2篇 |
1980年 | 5篇 |
1979年 | 8篇 |
1978年 | 3篇 |
1977年 | 2篇 |
1976年 | 2篇 |
1975年 | 2篇 |
1959年 | 1篇 |
1955年 | 1篇 |
排序方式: 共有6243条查询结果,搜索用时 15 毫秒
71.
72.
73.
Attitude control of operational satellites is still predominantly performed by standard controllers such as Proportional plus Derivative (PD) control laws, which are still preferred for implementation to the computationally intensive nonlinear optimal control techniques, representing higher implementation complexity. In this paper, an inverse optimal control approach based on phase space geometry is presented, which is easy to implement and free from numerical and computational issues. The optimal control objective is to minimize a norm of the control torque subject to a rapidity constraint on the convergence rate of a Lyapunov function, under the effect of a benchmark controller. The proposed optimization method is shown to significantly enhance the torque-rapidity trade-off compared to the benchmark controller, chosen to be a PD law then a sliding mode controller. The inverse optimal control scheme is implemented on an air bearing table experimental platform. 相似文献
74.
针对ZigBee网络的Cluster-Tree算法对簇首能量要求高、选择的路由非最佳路由等问题,结合节点能量分析和节点邻居表,提出一种改进的簇首生成方法,利用AODVjr算法为节点选择最佳路由。仿真结果证明,与原Cluster-Tree算法相比,改进的算法能有效提高数据发送成功率,减少源节点与目标节点间的跳数,降低端到端的报文传输时延,提高网络的使用价值。 相似文献
75.
76.
Tongqing Qiu Edward Chan Mao Ye Guihai Chen Ben Y. Zhao 《The Journal of supercomputing》2009,48(1):15-42
A self-organizing peer-to-peer system is built upon an application level overlay, whose topology is independent of an underlying
physical network. A well-routed message path in such systems may result in a long delay and excessive traffic due to the mismatch
between logical and physical networks. In order to solve this problem, we present a family of Peer-exchange Routing Optimization
Protocols (PROP) to reconstruct the overlay. It includes two policies: PROP-G for generic condition and PROP-O for optimized
one. Both theoretical analysis and simulation experiments show that these two protocols greatly reduce the average latency
of the overlay and achieve a better logical topology with low overhead. Their overall performance can be further improved
if combined with other recent approaches. Specifically, PROP-G can be easily applied to both structured and unstructured systems
without the loss of their primary characteristics, such as efficient routing and anonymity. PROP-O, on the other hand, is
more efficient, especially in a heterogenous environment where nodes have different processing capabilities.
相似文献
Edward ChanEmail: |
77.
78.
为测试某型飞机振动传感器性能,采用背靠背比较法振动测试方法,基于苏试振动台(VT-500)、功率放大器(LA-800)、单轴向电荷输出型加速度标准传感器(Ymc222A25)、电荷放大器(Ymc8102T)、普源信号发生器(DG1032Z)以及研华PCI工控机与A/D板卡(PCI-1716L),搭建振动传感器试验器振动测试平台,以DG1032Z输出作为振动激励信号源,基于VC ++6.0开发出信号发生器远程控制与板卡信号采集软件,对试验器的功能进行试验验证,结果表明其有效性.所研制的试验器可实现振动信号源的产生与标准/被测信号的校准,从而为某型飞机振动传感器的测试与修理提供技术支撑. 相似文献
79.
王述聪 《电脑编程技巧与维护》2013,(22):52-54
讲述Android手机应用开发实例.手机用户可通过查询,了解学校安排的课程信息,为师生提供了方便. 相似文献
80.
Any Gray code for a set of combinatorial objects defines a total order relation on this set: x is less than y if and only if y occurs after x in the Gray code list. Let ? denote the order relation induced by the classical Gray code for the product set (the natural extension of the Binary Reflected Gray Code to k-ary tuples). The restriction of ? to the set of compositions and bounded compositions gives known Gray codes for those sets. Here we show that ? restricted to the set of bounded compositions of an interval yields still a Gray code. An n-composition of an interval is an n-tuple of integers whose sum lies between two integers; and the set of bounded n-compositions of an interval simultaneously generalizes product set and compositions of an integer, and so ? put under a single roof all these Gray codes.As a byproduct we obtain Gray codes for permutations with a number of inversions lying between two integers, and with even/odd number of inversions or cycles. Such particular classes of permutations are used to solve some computational difficult problems. 相似文献