全文获取类型
收费全文 | 67363篇 |
免费 | 7379篇 |
国内免费 | 3705篇 |
专业分类
电工技术 | 5659篇 |
技术理论 | 8篇 |
综合类 | 5130篇 |
化学工业 | 9908篇 |
金属工艺 | 4125篇 |
机械仪表 | 4292篇 |
建筑科学 | 5579篇 |
矿业工程 | 2367篇 |
能源动力 | 2046篇 |
轻工业 | 4280篇 |
水利工程 | 1618篇 |
石油天然气 | 3370篇 |
武器工业 | 801篇 |
无线电 | 7970篇 |
一般工业技术 | 7493篇 |
冶金工业 | 2833篇 |
原子能技术 | 917篇 |
自动化技术 | 10051篇 |
出版年
2024年 | 370篇 |
2023年 | 1324篇 |
2022年 | 2770篇 |
2021年 | 3640篇 |
2020年 | 2737篇 |
2019年 | 2086篇 |
2018年 | 2401篇 |
2017年 | 2611篇 |
2016年 | 2386篇 |
2015年 | 3335篇 |
2014年 | 3994篇 |
2013年 | 4691篇 |
2012年 | 5250篇 |
2011年 | 5550篇 |
2010年 | 4731篇 |
2009年 | 4415篇 |
2008年 | 4269篇 |
2007年 | 3862篇 |
2006年 | 3635篇 |
2005年 | 2982篇 |
2004年 | 2008篇 |
2003年 | 1459篇 |
2002年 | 1323篇 |
2001年 | 1061篇 |
2000年 | 1008篇 |
1999年 | 925篇 |
1998年 | 695篇 |
1997年 | 563篇 |
1996年 | 577篇 |
1995年 | 404篇 |
1994年 | 341篇 |
1993年 | 243篇 |
1992年 | 209篇 |
1991年 | 120篇 |
1990年 | 108篇 |
1989年 | 80篇 |
1988年 | 75篇 |
1987年 | 44篇 |
1986年 | 33篇 |
1985年 | 29篇 |
1984年 | 14篇 |
1983年 | 12篇 |
1982年 | 14篇 |
1981年 | 10篇 |
1980年 | 10篇 |
1979年 | 7篇 |
1976年 | 9篇 |
1975年 | 3篇 |
1959年 | 9篇 |
1951年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
171.
Jakobi et al. for the first time proposed a novel and practical quantum private query (QPQ) protocol based on SARG04 (Scarani et al. in Phys Rev Lett 92:057901, 2004) quantum key distribution protocol (Jakobi et al. in Phys Rev A 83:022301, 2011). Gao et al. generalized Jakobi et al’s protocol and proposed a flexible QPQ protocol (Gao et al. in Opt Exp 20(16):17411–17420, 2012). When $\theta <\pi /4$ , Gao et al’s protocol exhibits better database security than Jakobi et al’s protocol, but has a higher probability with which Bob can correctly guess the address of Alice’s query. In this paper, we propose a flexible B92-based QPQ protocol. Although SARG04 protocol is a modification of B92 protocol and can be seen as a generalization of B92 protocol, our protocol shows different advantages from Gao et al’s protocol. It can simultaneously obtain better database security and a lower probability with which Bob can correctly guess the address of Alice’s query when $\theta <\pi /4$ . By introducing entanglement, the proposed QPQ protocol is robust against channel-loss attack, which also implies lower classical communication complexity. Similar to Gao et al’s protocol, it is flexible, practical, and robust against quantum memory attack. 相似文献
172.
Jiwei Wen Li Peng Sing Kiong Nguang 《International Journal of Control, Automation and Systems》2014,12(3):473-485
In this paper, the finite-time control problem is investigated for a class of discrete-time Markovian jump systems (MJLSs) with deterministic switching and time-delay. The considered systems are subject to a piecewise-constant transition probability (TP) matrix, which leads to both the deterministic switches and stochastic jumps. First, the stochastic finite-time boundedness (SFTB) and l 2 gain analysis for the systems are studied by employing the average dwell time (ADT) approach. Note that a finite-time weighted l 2 gain is obtained to measure the disturbance attenuation level. Then, the mode-dependent and variation-dependent controller is designed such that the resulting closed-loop systems are stochastically finite-time bounded and have a guaranteed disturbance attenuation level. Finally, a numerical example is given to verify the potential of the developed results. 相似文献
173.
Guang-yu Zhu Gao-na Lu Chen-Guang Yang Peng Zhang 《Personal and Ubiquitous Computing》2014,18(8):1955-1961
Unified judgment standards and methods are often adopted to identify traffic state in certain road network based on traffic flow parameters. However, drivers often have different perceptions about the traffic state on different road sections, since their expectations on traffic state vary more or less from each other on different road sections. In particular, under the vehicle networking, out of considerations for safety and other relevant factors, requirements for the correlation and coordination of running vehicles have also raised significantly. Therefore, it is necessary to take driver’s perception about the driving conditions of certain road sections into consideration to adjust the release of traffic state. This paper has provided a comprehensive traffic state evaluation model linked with driver’s perception under the vehicle networking. The authors first establish an ANFIS model based on the T–S model and then conduct statistical analysis on drivers’ perceptions about certain traffic state. At last, the authors use the results of statistical analysis as regulatory factors to amend the parameters input through ANFIS. Through simulation, this paper has demonstrated that the model established has a high rate of convergence, a high identification precision and the generalization ability to conduct researches on the identification of traffic state. 相似文献
174.
局部特征和全局特征是图像的两种重要的特征描述,在图像分类时起着至关重要的作用。据此提出一种通过融合全局与局部特征核量化图像分类方法。首先,分析全局特征及局部特征各自优缺点,并对图像进行特征提取;其次,通过核方法将特征映射到适当的高维空间中,来进行码书的获取与量化,并进行特征的融合以更好地对图像进行描述;最后,采用基于直方图交叉核的支持向量机对获取的量化特征进行分类。通过实验证明了所提出的方法的可行性。 相似文献
175.
运动发酵单胞(Zymomonas mobilis)ATCC29191菌株在含1~3g/L甘氨酸的液体培育12小时的菌体,用含20g/L的溶菌酶溶液处理12小时,可以稳定得到80%~90%的原生质球。原生质球稀释后在底层再生培养基上涂布,上面复盖一层半固体培养基,30℃培养5~7小时,再生率可达10~(-2)水平。 相似文献
176.
Semi‐Markovian jump systems, due to the relaxed conditions on the stochastic process, and its transition rates are time varying, can be used to describe a larger class of dynamical systems than conventional full Markovian jump systems. In this paper, the problem of stochastic stability for a class of semi‐Markovian systems with mode‐dependent time‐variant delays is investigated. By Lyapunov function approach, together with a piecewise analysis method, a sufficient condition is proposed to guarantee the stochastic stability of the underlying systems. As more time‐delay information is used, our results are much less conservative than some existing ones in literature. Finally, two examples are given to show the effectiveness and advantages of the proposed techniques. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
177.
In this paper, a generalized robust H ∞ filtering method is proposed for a class of singular Markovian jump systems, whose generality is mainly embodied that the desired filter could bear perturbances in terms of uncertainties on its parameter matrices. Firstly, an LMI condition of robust mode‐dependent filter is developed. Based on the given result, a new approach to mode‐independent H ∞ filter is presented, which establishes a direct connection between mode‐dependent and mode‐independent filters. Secondly, when the transition rate matrix is with elementwise bounded uncertainties or partially unknown, sufficient conditions of such robust mode‐dependent and mode‐independent filters are all developed within LMI frameworks. Finally, a numerical example is used to demonstrate the effectiveness of the proposed methods. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
178.
In this paper, the problem of non‐fragile observer‐based H ∞ control for discrete‐time switched delay systems is investigated. Both data missing and time delays are taken into account in the links from sensors to observers and from controllers to actuators. Because data missing satisfies the Bernoulli distribution, such problem is transformed into an H ∞ control problem for stochastic switched delay systems. Average dwell time approach is used to obtain sufficient conditions on the solvability of such problems. A numerical example and a real example for water quality control are provided to illustrate the effectiveness and potential applications of the proposed techniques. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
179.
Microcellular foaming of biodegradable Bionolle in supercritical CO2 has been produced. The effects of a series of variable factors, such as saturation temperature, saturation pressure, and depressurization time and step on the foam structures and density, were studied through measurement of density and SEM observation. The experimental results show that higher saturation temperatures lead to an increase in bulk densities; and different depressurization time and step result in different product cell morphology. In addition, at some saturation temperature, the orientation of the cells can be found in the product morphology. XRD experimental results show that the foaming treatment with SC CO2 increased the crystallinity of Bionolle. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2901–2906, 2006 相似文献
180.
针对服务流程建模语言BPEL4WS难以满足用户个性化需求也无法适应动态环境变化的问题,提出了一种动态优化BPEL4WS中流程服务的方法。该方法给出了一种Web服务交互代价计算模型,用来评价用户对Web服务的偏好程度以及实时环境下Web服务交互的现实代价。将BPEL4WS描述的服务组合流程转换为服务组合流程树,并借助领域本体对流程树节点进行语义检查,消除流程树中不合法的流程组合。通过深度优先遍历流程树,利用单亲遗传算法对流程服务进行优化组合。最后给出应用算例,并对用来优化组合流程服务的单亲遗传算法的适用性与 相似文献