全文获取类型
收费全文 | 67620篇 |
免费 | 5499篇 |
国内免费 | 2959篇 |
专业分类
电工技术 | 3922篇 |
技术理论 | 7篇 |
综合类 | 4672篇 |
化学工业 | 11343篇 |
金属工艺 | 3843篇 |
机械仪表 | 4241篇 |
建筑科学 | 5741篇 |
矿业工程 | 1965篇 |
能源动力 | 1969篇 |
轻工业 | 4216篇 |
水利工程 | 1265篇 |
石油天然气 | 4577篇 |
武器工业 | 514篇 |
无线电 | 7368篇 |
一般工业技术 | 8341篇 |
冶金工业 | 3293篇 |
原子能技术 | 748篇 |
自动化技术 | 8053篇 |
出版年
2024年 | 228篇 |
2023年 | 1056篇 |
2022年 | 1768篇 |
2021年 | 2519篇 |
2020年 | 1960篇 |
2019年 | 1682篇 |
2018年 | 1906篇 |
2017年 | 2165篇 |
2016年 | 1961篇 |
2015年 | 2472篇 |
2014年 | 3358篇 |
2013年 | 3874篇 |
2012年 | 4388篇 |
2011年 | 4755篇 |
2010年 | 4242篇 |
2009年 | 4006篇 |
2008年 | 3943篇 |
2007年 | 3846篇 |
2006年 | 3864篇 |
2005年 | 3328篇 |
2004年 | 2230篇 |
2003年 | 1955篇 |
2002年 | 1702篇 |
2001年 | 1635篇 |
2000年 | 1695篇 |
1999年 | 1783篇 |
1998年 | 1382篇 |
1997年 | 1169篇 |
1996年 | 1050篇 |
1995年 | 936篇 |
1994年 | 769篇 |
1993年 | 556篇 |
1992年 | 433篇 |
1991年 | 336篇 |
1990年 | 312篇 |
1989年 | 226篇 |
1988年 | 174篇 |
1987年 | 107篇 |
1986年 | 104篇 |
1985年 | 60篇 |
1984年 | 41篇 |
1983年 | 26篇 |
1982年 | 33篇 |
1981年 | 23篇 |
1980年 | 13篇 |
1979年 | 3篇 |
1978年 | 1篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1959年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
992.
miRNA检测技术进展 总被引:2,自引:0,他引:2
miRNA做为一种非常重要的非编码蛋白的RNA.广泛存在于植物、病毒、哺乳动物当中.因其在细胞增殖、细胞死亡、肿瘤发生和哺乳动物细胞生长中重要的调节功能,其检测技术也受到越来越多的关注,很多关键的检测技术,比如印迹技术,阵列杂交技术,反转录PCR技术等等都在miRNA的检测中发挥了巨大的实用价值.该文基于此对miRNA近几年的检测技术进行了具体的综述. 相似文献
993.
为提高移动机器人定位系统的可靠性,设计了组合使用光纤陀螺仪、光电码盘和超声波传感器的定位系统,系统采用CAN总线的数据传输方式。ATmega16采集各传感器数据,再以CAN总线方式传输给PC机;PC机平台综合处理光纤陀螺、光电码盘与超声波返回的数据,实现移动机器人定位。定位算法以航迹推算为主,超声波传感器起辅助定位作用。实验表明定位系统可靠有效。 相似文献
994.
In this paper, the dynamic behaviors of a class of neural networks with time-varying delays are investigated. Some less weak
sufficient conditions based on p-norm and ∞-norm are obtained to guarantee the existence, uniqueness of the equilibrium point for the addressed neural networks
without impulsive control by applying homeomorphism theory. And then, by utilizing inequality technique, Lyapunov functional
method and the analysis method, some new and useful criteria of the globally exponential stability with respect to the equilibrium
point under impulsive control we assumed are derived based on p-norm and ∞-norm, respectively. Finally, an example with simulation is given to show the effectiveness of the obtained results. 相似文献
995.
Reliable multicast, the lossless dissemination of data from one sender to a group of receivers, has a wide range of important applications. Recently, network coding has been applied to the reliable multicast in wireless networks, where multiple lost packets with distinct intended receivers are XOR-ed together as one packet and forwarded via single retransmission, resulting in a significant reduction of bandwidth consumption. However, the simple XOR operation cannot fully exploit the potential coding opportunities and finding the optimal set of lost packets for XOR-ing is a complex NP-complete optimization problem. In this work, we intend to move beyond the simple XOR to more general coding operations. Specifically, we propose two new schemes (a static scheme which repeatedly retransmits one coding packet until all intended receivers receive it and a dynamic scheme which updates the coding packet once one or more receivers receive it) to encode packets with more general coding operations, which not only can encode lost packets with common intended receivers together to fully exploit the potential coding opportunities but also have polynomial-time complexity. We demonstrate, through both analytical and simulation results, that the proposed schemes can more greatly reduce the bandwidth requirement than the available coding-based schemes, especially in the case of high packet loss probabilities and a larger number of receivers. This reduction can vary from a few percents to over 15% depending on the packet loss probabilities and the number of receivers. 相似文献
996.
Akira Inoue 《国际自动化与计算杂志》2010,7(2):213-218
In this paper, robust stability of nonlinear plants represented by non-symmetric Prandtl-Ishlinskii (PI) hysteresis model is studied. In general, PI hysteresis model is the weighted superposition of play or stop hysteresis operators, and the slopes of the operators are considered to be the same. In order to make a hysteresis model, a modified form of non-symmetric play hysteresis operator with unknown slopes is given. The hysteresis model is described by a generalized Lipschitz operator term and a bounded parasitic term. Since the generalized Lipschitz operator is unknown, a new condition using robust right coprime factorization is proposed to guarantee robust stability of the controlled plant with the hysteresis nonlinearity. As a result, based on the proposed robust condition, a stabilized plant is obtained. A numerical example is presented to validate the effectiveness of the proposed method. 相似文献
997.
Copper nanofluids have been chemically synthesized by using home-made microfluidic reactors and by using a boiling flask-3-neck. The influence of flow rates of reactants, reactants concentrations, and surfactant concentrations on copper particle size and size distribution has been investigated. It has been found that neither of them has much influence on particle size and size distribution of copper nanoparticles synthesized in microfluidic reactors due to the fast and efficient mass diffusion in microscale dimension. The copper nanoparticles have an average size of about 3.4 nm with a relatively narrow size distribution of around 22% evaluated by the coefficient of variation. While the average size of copper nanoparticles synthesized by flask method changes from 2.7 to 4.9 nm with a coefficient of variation larger than 30%, depending on concentrations of [Cu(NH3)4]·(OH)2 and surfactant sodium dodecylbenzenesulfonate. In addition, by using microfluidic reactors the synthesis time of copper nanofluids can be reduced as much as one order of magnitude, from ~10 min to ~28 s. 相似文献
998.
Jingyun Ma Lei Jiang Xiaoyan Pan Huipeng Ma Bingcheng Lin Jianhua Qin 《Microfluidics and nanofluidics》2010,9(6):1247-1252
A straightforward method for microfluidic devices fabrication using sunlight as the ultraviolet (UV) source is established
in this work. This method is based on photolithography, but obviates the need for specialized UV exposure facility. Substrates
coated with photoresist were placed directly under sun in a perpendicular direction to the sunlight for exposure. Exposure
conditions were optimized for patterning features with different kinds of photoresist, photoresist of different thicknesses
and dimensions. Exposure time can be adjusted to obtain designed features on a mask with good lateral structure according
to the energy measured by UV meter (with a constant intensity of UV in sunlight). Masters produced under optimum exposure
conditions were used for the fabrication of several microfluidic devices with different materials, structures, or functions.
Resultant devices were shown eminently suitable for microfluidic applications such as electrophoretic separation, multiple
gradient generator, and pneumatic valve-based cell culture. This photolithographic method is simple, low cost, easy to operate,
and environmental friendly. Especially, the masters can be obtained in parallel simultaneously, which is suitable for chip
fabrication for mass production. It is also more attractive for the laboratories, in which the support for photolithographic
facility is not available. 相似文献
999.
基于可溯源技术水产养殖监控系统的设计 总被引:1,自引:0,他引:1
介绍了一种用于工厂化水产养殖场中的环境因子的监控系统设计,实现了对各关键环境参数的实时监测与控制,利用现场总线技术实现了监控网络的互连和数据的高效传输,并通过引入无线射频识别技术(RFID)从而实现水产品从生产、流通、消费全过程的可溯源功能;结果表明,溶解氧含量及控制精度,温度控制精度,氨氮含量控制范围,以及PH值控制范围,完全达到了设计要求,能够满足工厂化水产养殖的需要. 相似文献
1000.
信号适配问题是组建导弹发射控制系统的技术难点,是决定测试精度和确保发射控制安全有效的关键因素之一,在某型导弹发射控制研制过程中,综合采用双端差动输入、继电器输出、光电隔离和软件识别等方法,完成了模拟信号、开关信号(包括三态信号)的调理适配和复杂电磁环境下脉冲串信号的计数判读,实现了导弹武器与发控系统之间和强弱电之间的彻底隔离;该研究成果不仅为发射控制系统的信号适配提供了通用的设计方法,而且可为其他电子设备ATS的组建提供有益的借鉴。 相似文献