全文获取类型
收费全文 | 87037篇 |
免费 | 8764篇 |
国内免费 | 6650篇 |
专业分类
电工技术 | 7513篇 |
技术理论 | 5篇 |
综合类 | 7672篇 |
化学工业 | 7464篇 |
金属工艺 | 2969篇 |
机械仪表 | 3892篇 |
建筑科学 | 5516篇 |
矿业工程 | 1468篇 |
能源动力 | 2625篇 |
轻工业 | 2866篇 |
水利工程 | 1268篇 |
石油天然气 | 2301篇 |
武器工业 | 882篇 |
无线电 | 8337篇 |
一般工业技术 | 7250篇 |
冶金工业 | 5590篇 |
原子能技术 | 789篇 |
自动化技术 | 34044篇 |
出版年
2024年 | 282篇 |
2023年 | 1166篇 |
2022年 | 1666篇 |
2021年 | 2075篇 |
2020年 | 2574篇 |
2019年 | 2537篇 |
2018年 | 2220篇 |
2017年 | 3054篇 |
2016年 | 3434篇 |
2015年 | 3372篇 |
2014年 | 5233篇 |
2013年 | 6648篇 |
2012年 | 5378篇 |
2011年 | 6036篇 |
2010年 | 4536篇 |
2009年 | 5161篇 |
2008年 | 4873篇 |
2007年 | 5573篇 |
2006年 | 5035篇 |
2005年 | 4236篇 |
2004年 | 3525篇 |
2003年 | 3314篇 |
2002年 | 2963篇 |
2001年 | 2541篇 |
2000年 | 2299篇 |
1999年 | 1925篇 |
1998年 | 1601篇 |
1997年 | 1404篇 |
1996年 | 1165篇 |
1995年 | 983篇 |
1994年 | 850篇 |
1993年 | 758篇 |
1992年 | 575篇 |
1991年 | 540篇 |
1990年 | 406篇 |
1989年 | 330篇 |
1988年 | 255篇 |
1987年 | 238篇 |
1986年 | 183篇 |
1985年 | 244篇 |
1984年 | 227篇 |
1983年 | 196篇 |
1982年 | 179篇 |
1981年 | 121篇 |
1980年 | 89篇 |
1979年 | 99篇 |
1978年 | 67篇 |
1977年 | 74篇 |
1976年 | 24篇 |
1975年 | 21篇 |
排序方式: 共有10000条查询结果,搜索用时 671 毫秒
71.
实时数据管理系统是流程企业控制信息网络与管理信息网络平滑集成的基础,为两者的数据通讯提供桥梁。介绍了笔者在炼油化工C企业IMS建设中的实时数据管理引擎设计与开发,具有其先进性与实用性。 相似文献
72.
73.
Kicheon Kim 《ETRI Journal》2006,28(1):31-44
In a packet switching network, congestion is unavoidable and affects the quality of real‐time traffic with such problems as delay and packet loss. Packet fair queuing (PFQ) algorithms are well‐known solutions for quality‐of‐service (QoS) guarantee by packet scheduling. Our approach is different from previous algorithms in that it uses hardware time achieved by sampling a counter triggered by a periodic clock signal. This clock signal can be provided to all the modules of a routing system to get synchronization. In this architecture, a variant of the PFQ algorithm, called digitized delay queuing (DDQ), can be distributed on many line interface modules. We derive the delay bounds in a single processor system and in a distributed architecture. The definition of traffic contribution improves the simplicity of the mathematical models. The effect of different time between modules in a distributed architecture is the key idea for understanding the delay behavior of a routing system. The number of bins required for the DDQ algorithm is also derived to make the system configuration clear. The analytical models developed in this paper form the basis of improvement and application to a combined input and output queuing (CIOQ) router architecture for a higher speed QoS network. 相似文献
74.
Kruk Menno R.; Halász József; Meelis Wout; Haller József 《Canadian Metallurgical Quarterly》2004,118(5):1062
Aggressive behavior induces an adrenocortical stress response, and sudden stressors often precipitate violent behavior. Experiments in rats revealed a fast, mutual, positive feedback between the adrenocortical stress response and a brain mechanism controlling aggression. Stimulation of the aggressive area in the hypothalamus rapidly activated the adrenocortical response, even in the absence of an opponent and fighting. Hypothalamic aggression, in turn, was rapidly facilitated by a corticosterone injection in rats in which the natural adrenocortical stress response was prevented by adrenalectomy. The rapidity of both effects points to a fast, mutual, positive feedback of the controlling mechanisms within the time frame of a single conflict. Such a mutual facilitation may contribute to the precipitation and escalation of violent behavior under stressful conditions. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
75.
Gas/liquid mass transfer has been investigated using a stirred vessel gas/liquid contactor using non‐Newtonian media and carbon dioxide as absorbent and gas phase, respectively. The volumetric mass transfer coefficients at different operational variables have been determined. Non‐Newtonian media (liquid phase) were prepared as aqueous solutions of sodium carboxymethyl cellulose salt. The influence of the rheological properties, polymer concentration, stirring rate, and gas flow rate on mass transfer was studied for these liquid phases. Kinematic viscosity and density experimental data were used to calculate the average molecular weight corresponding to the polymer employed. The Ostwald model has been used to fit the rheological behavior of aqueous solutions of the polymer employed as absorbent phase. Reasonably good agreement was found between the predictions of the proposed models and the experimental data of mass transfer coefficients. 相似文献
76.
77.
某些微分方程和相应的积分方程之间的关系被讨论;这些微分方程通过边境小波变换可被转换成相应的积分方程,它们不仅在弱收敛意义下而且在范围数收敛意义下是等价的;关于这些微分方程的讨论就与相应的积分方程的讨论联系起来。 相似文献
78.
串行和并行接口模式是A/D转换器诸多分类中的一种,但却是应用中器件选择的一个重要指标.在同样的转换分辨率及转换速度的前提下,不同的接口方式不但影响了电路结构,更重要的是将在高速数据采集的过程中对采样周期产生较大影响.本文通过12位串行ADC ADS7822和并行ADC ADS774与AT89C51的接口电路,给出二者采样时间的差异性. 相似文献
79.
叙述了二代近贴聚焦像增强器批量生产所用真空设备性能及特点,同时给出了管子工艺考核结果及管子纳秒时间响应特性。工艺考核结果表明,制管工艺可靠、性能稳定,管子批量生产合格率大于70%。 相似文献
80.
This paper proposes an original method for obtaining analytical approximations of the invariant probability density function of multi-dimensional Hamiltonian dissipative dynamic systems under Gaussian white noise excitations, with linear non-conservative parts and nonlinear conservative parts. The method is based on an exact result and a heuristic argument. Its pertinence is attested by numerical tests. 相似文献