全文获取类型
收费全文 | 150619篇 |
免费 | 14859篇 |
国内免费 | 9581篇 |
专业分类
电工技术 | 11749篇 |
技术理论 | 2篇 |
综合类 | 18311篇 |
化学工业 | 18897篇 |
金属工艺 | 7267篇 |
机械仪表 | 10464篇 |
建筑科学 | 18570篇 |
矿业工程 | 6732篇 |
能源动力 | 5079篇 |
轻工业 | 9326篇 |
水利工程 | 6622篇 |
石油天然气 | 7071篇 |
武器工业 | 2022篇 |
无线电 | 9628篇 |
一般工业技术 | 18426篇 |
冶金工业 | 6317篇 |
原子能技术 | 2521篇 |
自动化技术 | 16055篇 |
出版年
2024年 | 538篇 |
2023年 | 1729篇 |
2022年 | 3541篇 |
2021年 | 4105篇 |
2020年 | 4487篇 |
2019年 | 3892篇 |
2018年 | 3669篇 |
2017年 | 4699篇 |
2016年 | 5295篇 |
2015年 | 5486篇 |
2014年 | 9032篇 |
2013年 | 8565篇 |
2012年 | 11695篇 |
2011年 | 11700篇 |
2010年 | 9074篇 |
2009年 | 9423篇 |
2008年 | 8528篇 |
2007年 | 10746篇 |
2006年 | 9470篇 |
2005年 | 7959篇 |
2004年 | 6629篇 |
2003年 | 5695篇 |
2002年 | 4764篇 |
2001年 | 4004篇 |
2000年 | 3529篇 |
1999年 | 3046篇 |
1998年 | 2397篇 |
1997年 | 2067篇 |
1996年 | 1747篇 |
1995年 | 1564篇 |
1994年 | 1318篇 |
1993年 | 961篇 |
1992年 | 862篇 |
1991年 | 599篇 |
1990年 | 507篇 |
1989年 | 493篇 |
1988年 | 348篇 |
1987年 | 203篇 |
1986年 | 162篇 |
1985年 | 74篇 |
1984年 | 71篇 |
1983年 | 36篇 |
1982年 | 47篇 |
1981年 | 57篇 |
1980年 | 35篇 |
1979年 | 39篇 |
1978年 | 17篇 |
1975年 | 18篇 |
1959年 | 33篇 |
1951年 | 14篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
911.
In the robotic eye-in-hand measurement system, a hand-eye calibration method is essential. From the perspective of 3D reconstruction, this paper first analyzes the influence of the line laser sensor hand-eye calibration error on the 3D reconstructed point clouds error. Based on this, considering the influence of line laser sensor measurement errors and the need for high efficiency and convenience in robotic manufacturing systems, this paper proposes a 3D reconstruction-based robot line laser hand-eye calibration method. In this method, combined with the point cloud registration technique, the newly defined error-index more intuitively reflects the calibration result than traditional methods. To raise the performance of the calibration algorithm, a Particle Swarm Optimization - Gaussian Process (PSO-GP) method is adopted to improve the efficiency of the calibration. The experiments show that the Root Mean Square Error (RMSE) of the reconstructed point cloud can reach 0.1256 mm when using the proposed method, and the reprojection error is superior to those using traditional hand-eye calibration methods. 相似文献
912.
针对ViBe算法在动态背景下存在鬼影消除时间长、算法适应性差、前景检测噪声多的问题,本文提出一种基于ViBe算法框架的改进算法.该算法采用鬼影检测法标记第1帧中的鬼影区域,并向位于鬼影区域的背景模型中强制引入背景样本,从而快速抑制鬼影;在像素分类过程中,引入自适应分类阈值,解决全局阈值易受动态噪声干扰的问题;在背景模型更新中,根据像素分类的匹配值来动态决定更新因子,提高算法适应场景变化的能力.定性与定量的对比实验结果表明,本文算法相较于ViBe算法能够有效地检测动态背景下的运动目标,应用于河流漂浮物检测场景中也有较好的效果. 相似文献
913.
目前,在各地均有商贸活动开展,且参与人员众多,如果公安机关事先未做好预案,一旦发生突发性事件,人员疏散不到位,极易造成群死群伤事件。文章以商品大集为例,构建参与人员的流动模型,利用计算机技术实现流量和流动状况的模拟仿真,获得接近实际的流动的时间和动态过程.利于事先对类似活动拥堵情况进行准确评估。 相似文献
914.
介绍了避雷器三极法测量接地电阻的接线、测量原理及测量电压的选取,根据测得的历史数据建立了基于回归分析的接地电阻变化趋势预测模型,并通过标准离差检验证明了该预测模型可用于实际接地电阻的预测。实践表明,该测量与预测方法切实可行,能在一定程度上避免因接地电阻超标而引发的雷击事故。 相似文献
915.
916.
对于采用星敏感器的航天器姿态确定问题,提出了一种快速的姿态优化估计方法;首先,根据Rodrigues参数和观测向量之间的线性关系,引入四元数,构造了不同的非奇异的优化准则;其次,借助四元数,求解了基于该准则的姿态优化算法;误差协方差分析和数值仿真结果表明,该算法与著名的QUaternion ESTmation(QUEST)算法相比,在相同的操作系统环境下,具有相同的姿态估计精度,但计算速度更快,对两种算法选取间隔为2000次的仿真步长,统计数据长度为100个采样点,最后对结果加权求平均值,统计结果显示仅为QUEST的三分之一;这种姿态优化估计方法具有一定的工程应用价值。 相似文献
917.
Hongfei Li 《国际强度与非线性控制杂志
》2012,22(8):875-891
》2012,22(8):875-891
Time‐delay systems described by coupled differential‐functional equations include as special cases many types of time‐delay systems and coupled differential‐difference systems with time delays. This article discusses the discretized Lyapunov–Krasovskii functional (LKF) method for the stability problem of coupled differential‐difference equations with multiple discrete and distributed delays. Through independently dividing every delay region that the plane regions consists in two delays to discretize LKF, the exponential stability conditions for coupled systems with multiple discrete and distributed delays are established based on a linear matrix inequality (LMI). The numerical examples show that the analysis limit of delay bound in which the systems are stable may be approached by our result. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
918.
《Optimization methods & software》2012,27(4):573-585
Interior point (IP) algorithms for Min Cost Flow (MCF) problems have been shown to be competitive with combinatorial approaches, at least on some problem classes and for very large instances. This is in part due to availability of specialized crossover routines for MCF; these allow early termination of the IP approach, sparing it with the final iterations where the Karush Kuhn-Tucker (KKT) systems become more difficult to solve. As the crossover procedures are nothing but combinatorial approaches to MCF that are only allowed to perform few iterations, the IP algorithm can be seen as a complex ‘multiple crash start’ routine for the combinatorial ones. We report our experiments of allowing one primal-dual combinatorial algorithm to MCF to perform as many iterations as required to solve the problem after being warm-started by an IP approach. Our results show that the efficiency of the combined approach critically depends on the accurate selection of a set of parameters among very many possible ones, for which designing accurate guidelines appears not to be an easy task; however, they also show that the combined approach can be competitive with the original combinatorial algorithm, at least on some ‘difficult’ instances. 相似文献
919.
To overcome the disadvantages of the location algorithm based on received signal strength indication(RSSI) in the existing wireless sensor networks(WSNs),a novel adaptive cooperative location algorithm is proposed.To tolerate some minor errors in the information of node position,a reference anchor node is employed.On the other hand,Dixon method is used to remove the outliers of RSSI,the standard deviation threshold of RSSI and the learning model are put forward to reduce the ranging error of RSSI and improve the positioning precision effectively.Simulations are run to evaluate the performance of the algorithm.The results show that the proposed algorithm offers more precise location and better stability and robustness. 相似文献
920.
In this article, we consider the project critical path problem in an environment with hybrid uncertainty. In this environment, the duration of activities are considered as random fuzzy variables that have probability and fuzzy natures, simultaneously. To obtain a robust critical path with this kind of uncertainty a chance constraints programming model is used. This model is converted to a deterministic model in two stages. In the first stage, the uncertain model is converted to a model with interval parameters by alpha-cut method and distribution function concepts. In the second stage, the interval model is converted to a deterministic model by robust optimization and min-max regret criterion and ultimately a genetic algorithm with a proposed exact algorithm are applied to solve the final model. Finally, some numerical examples are given to show the efficiency of the solution procedure. 相似文献