全文获取类型
收费全文 | 74676篇 |
免费 | 6119篇 |
国内免费 | 3018篇 |
专业分类
电工技术 | 3991篇 |
技术理论 | 9篇 |
综合类 | 4521篇 |
化学工业 | 12983篇 |
金属工艺 | 4186篇 |
机械仪表 | 4703篇 |
建筑科学 | 5759篇 |
矿业工程 | 2474篇 |
能源动力 | 2176篇 |
轻工业 | 4601篇 |
水利工程 | 1244篇 |
石油天然气 | 5084篇 |
武器工业 | 648篇 |
无线电 | 8160篇 |
一般工业技术 | 9170篇 |
冶金工业 | 3671篇 |
原子能技术 | 831篇 |
自动化技术 | 9602篇 |
出版年
2024年 | 372篇 |
2023年 | 1403篇 |
2022年 | 2318篇 |
2021年 | 3180篇 |
2020年 | 2487篇 |
2019年 | 2046篇 |
2018年 | 2255篇 |
2017年 | 2590篇 |
2016年 | 2276篇 |
2015年 | 2972篇 |
2014年 | 3613篇 |
2013年 | 4431篇 |
2012年 | 4507篇 |
2011年 | 5033篇 |
2010年 | 4214篇 |
2009年 | 4057篇 |
2008年 | 4066篇 |
2007年 | 3739篇 |
2006年 | 3793篇 |
2005年 | 3453篇 |
2004年 | 2169篇 |
2003年 | 1990篇 |
2002年 | 1797篇 |
2001年 | 1587篇 |
2000年 | 1722篇 |
1999年 | 2045篇 |
1998年 | 1704篇 |
1997年 | 1399篇 |
1996年 | 1351篇 |
1995年 | 1168篇 |
1994年 | 971篇 |
1993年 | 731篇 |
1992年 | 563篇 |
1991年 | 431篇 |
1990年 | 341篇 |
1989年 | 254篇 |
1988年 | 234篇 |
1987年 | 151篇 |
1986年 | 107篇 |
1985年 | 68篇 |
1984年 | 59篇 |
1983年 | 46篇 |
1982年 | 35篇 |
1981年 | 26篇 |
1980年 | 20篇 |
1979年 | 13篇 |
1978年 | 5篇 |
1976年 | 5篇 |
1972年 | 3篇 |
1959年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
针对最小二乘支持向量机(LSSVM)存建模中的重要参数如何选择问题.提出利用具有随机性、遍历性及规律性的混沌优化算法对LSSVM建模过程中的参数进行优化搜索,为了加快对较大搜索空间中的搜索速度,提出变尺度混沌优化算法与遗传算法相结合遗传算法的组合算法对LSSVM中的参数优化.组合算法克服了单一算法存在的早熟、局部收敛及寻优速度慢等问题,把混沌变最种群映射到LSSVM参数取值区间.按照遗传算法训练,同时利用训练集训练LSSVM,最终得到参数优化值.将该方法应用的谷氨酸发酵过程的建模研究,取得了较高建模精度,提高发酵过程资源利用率的同时增加了谷氨酸产量. 相似文献
993.
This study presents a novel weight-based multiobjective artificial immune system (WBMOAIS) based on opt-aiNET, the artificial immune system algorithm for multi-modal optimization. The proposed algorithm follows the elementary structure of opt-aiNET, but has the following distinct characteristics: (1) a randomly weighted sum of multiple objectives is used as a fitness function. The fitness assignment has a much lower computational complexity than that based on Pareto ranking, (2) the individuals of the population are chosen from the memory, which is a set of elite solutions, and a local search procedure is utilized to facilitate the exploitation of the search space, and (3) in addition to the clonal suppression algorithm similar to that used in opt-aiNET, a new truncation algorithm with similar individuals (TASI) is presented in order to eliminate similar individuals in memory and obtain a well-distributed spread of non-dominated solutions. The proposed algorithm, WBMOAIS, is compared with the vector immune algorithm (VIS) and the elitist non-dominated sorting genetic system (NSGA-II) that are representative of the state-of-the-art in multiobjective optimization metaheuristics. Simulation results on seven standard problems (ZDT6, SCH2, DEB, KUR, POL, FON, and VNT) show WBMOAIS outperforms VIS and NSGA-II and can become a valid alternative to standard algorithms for solving multiobjective optimization problems. 相似文献
994.
995.
Tian Y Shumway BR Gao W Youngbull C Holl MR Johnson RH Meldrum DR 《Sensors and actuators. B, Chemical》2010,150(2):579-587
Oxygen sensing films were synthesized by a chemical conjugation of functional platinum porphyrin probes in silica gel, polystyrene (PS), and poly(2-hydroxyethyl methacrylate) (PHEMA) matrices. Responses of the sensing films to gaseous oxygen and dissolved oxygen were studied and the influence of the matrices on the sensing behaviors was investigated. Silica gel films had the highest fluorescence intensity ratio from deoxygenated to oxygenated environments and the fastest response time to oxygen. PHEMA films had no response to gaseous oxygen, but had greater sensitivity and a faster response time for dissolved oxygen than those of PS films. The influence of matrices on oxygen response, sensitivity and response time was discussed. The influence is most likely attributed to the oxygen diffusion abilities of the matrices. Since the probes were chemically immobilized in the matrices, no leaching of the probes was observed from the sensing films when applied in aqueous environment. One sensing film made from the PHEMA matrix was used to preliminarily monitor the oxygen consumption of Escherichia coli (E. coli) bacteria. E. coli cell density and antibiotics ampicillin concentration dependent oxygen consumption was observed, indicating the potential application of the oxygen sensing film for biological application. 相似文献
996.
Based on the internal model control (IMC) structure, an iterative learning control (ILC) scheme is proposed for batch processes with model uncertainties including time delay mismatch. An important merit is that the IMC design for the initial run of the proposed control scheme is independent of the subsequent ILC for realization of perfect tracking. Sufficient conditions to guarantee the convergence of ILC are derived. To facilitate the controller design, a unified controller form is proposed for implementation of both IMC and ILC in the proposed control scheme. Robust tuning constraints of the unified controller are derived in terms of the process uncertainties described in a multiplicative form. To deal with process uncertainties, the unified controller can be monotonically tuned to meet the compromise between tracking performance and control system robust stability. Illustrative examples from the recent literature are performed to demonstrate the effectiveness and merits of the proposed control scheme. 相似文献
997.
This paper considers the existence of the equilibrium point and its global exponential robust stability for reaction-diffusion
interval neural networks with variable coefficients and distributed delays by means of the topological degree theory and Lyapunov-functional
method. The sufficient conditions on global exponential robust stability established in this paper are easily verifiable.
An example is presented to demonstrate the effectiveness and efficiency of our results. 相似文献
998.
999.
Real-time removal of ocular artifacts from EEG based on independent component analysis and manifold learning 总被引:1,自引:1,他引:0
Junfeng Gao Pan Lin Yong Yang Pei Wang Chongxun Zheng 《Neural computing & applications》2010,19(8):1217-1226
Frequent occurrence of ocular artifacts leads to serious problems in interpreting and analyzing the electroencephalogram (EEG).
In the present paper, a novel and robust technique is proposed to eliminate ocular artifacts from EEG signals in real time.
Independent Component Analysis (ICA) is used to decompose EEG signals. The features of topography and power spectral density
of those components are extracted. Moreover, we introduce manifold learning algorithm, a recently popular dimensionality reduction
technique, to reduce the dimensionality of initial features, and then those new features are fed to a classifier to identify
ocular artifacts components. A k-nearest neighbor classifier is adopted to classify components because classification results
show that manifold learning with the nearest neighbor algorithm works best. Finally, the artifact removal method proposed
here is evaluated by the comparisons of EEG data before and after artifact removal. The results indicate that the method proposed
could remove ocular artifacts effectively from EEG signals with little distortion of the underlying brain signals and be satisfied
the real-time application. 相似文献
1000.
Maintenance as an important part in manufacturing system can keep equipment in good condition. Many maintenance policies help
to decrease the unexpected failures and reduce high operational cost such as conventional preventive maintenance. But these
conventional preventive maintenance policies have the same time interval T that may easily neglect system’s reliability, because the system deteriorates with increased usage and age. Hence, this study
has developed a reliability-centred sequential preventive maintenance model for monitored repairable deteriorating system.
It is supposed that system’s reliability could be monitored continuously and perfectly, whenever it reaches the threshold
R, the imperfect repair must be performed to restore the system. In this model, system’s failure rate function and operational
cost are both considered by the effect of system’s corresponding condition, which helps to decide the optimal reliability
threshold R and preventive maintenance cycle number. Finally, through case study, the simulation results show that the improved sequential
preventive maintenance policy is more practical and efficient. 相似文献