全文获取类型
收费全文 | 9801篇 |
免费 | 1287篇 |
国内免费 | 1101篇 |
专业分类
电工技术 | 220篇 |
综合类 | 853篇 |
化学工业 | 623篇 |
金属工艺 | 130篇 |
机械仪表 | 260篇 |
建筑科学 | 217篇 |
矿业工程 | 99篇 |
能源动力 | 124篇 |
轻工业 | 320篇 |
水利工程 | 180篇 |
石油天然气 | 156篇 |
武器工业 | 42篇 |
无线电 | 2595篇 |
一般工业技术 | 611篇 |
冶金工业 | 79篇 |
原子能技术 | 48篇 |
自动化技术 | 5632篇 |
出版年
2024年 | 26篇 |
2023年 | 119篇 |
2022年 | 156篇 |
2021年 | 202篇 |
2020年 | 299篇 |
2019年 | 203篇 |
2018年 | 236篇 |
2017年 | 306篇 |
2016年 | 360篇 |
2015年 | 509篇 |
2014年 | 681篇 |
2013年 | 746篇 |
2012年 | 832篇 |
2011年 | 879篇 |
2010年 | 734篇 |
2009年 | 790篇 |
2008年 | 786篇 |
2007年 | 807篇 |
2006年 | 641篇 |
2005年 | 589篇 |
2004年 | 485篇 |
2003年 | 407篇 |
2002年 | 295篇 |
2001年 | 252篇 |
2000年 | 184篇 |
1999年 | 130篇 |
1998年 | 108篇 |
1997年 | 78篇 |
1996年 | 70篇 |
1995年 | 64篇 |
1994年 | 44篇 |
1993年 | 37篇 |
1992年 | 31篇 |
1991年 | 20篇 |
1990年 | 13篇 |
1989年 | 9篇 |
1988年 | 8篇 |
1987年 | 9篇 |
1986年 | 10篇 |
1985年 | 4篇 |
1984年 | 9篇 |
1983年 | 10篇 |
1982年 | 2篇 |
1981年 | 3篇 |
1980年 | 5篇 |
1978年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
自动交换光网络的概念一经提出即受到业界的广泛关注,运营商尤其对其寄予了厚望。本文首先概要地介绍了ASON的优点,然后重点论述了ASON的信令与路由功能,包括对它们的要求以及标准化工作。 相似文献
12.
We consider the switchbox routing problem of two-terminal nets in the case when all thek nets lie on two adjacent sides of the rectangle. Our routing model is the standard two-layer model. We develop an optimal algorithm that routes all the nets whenever a routing exists. The routing obtained uses the fewest possible number of vias. A more general version of this problem (adjacent staircase) is also optimally solved.This research was supported in part by NSA Contract No. MDA-904-85H-0015, NSF Grant No. DCR-86-00378, and by NSF Engineering Research Centers Program NSFD CDR 88003012. 相似文献
13.
14.
Recent technological advances have made it possible to support long lifetime and large volume streaming data transmissions
in sensor networks. A major challenge is to maximize the lifetime of battery-powered sensors to support such transmissions.
Battery, as the power provider of the sensors, therefore emerges as the key factor for achieving high performance in such
applications. Recent study in battery technology reveals that the behavior of battery discharging is more complex than we
used to think. Battery powered sensors might waste a huge amount of energy if we do not carefully schedule and budget their
discharging. In this paper we study the effect of battery behavior on routing for streaming data transmissions in wireless
sensor networks. We first give an on-line computable energy model to mathematically model battery discharge behavior. We show
that the model can capture and describe battery behavior accurately at low computational complexity and thus is suitable for
on-line battery capacity computation. Based on this battery model we then present a battery-aware routing (BAR) protocol to
schedule the routing in wireless sensor networks. The routing protocol is sensitive to the battery status of routing nodes
and avoids energy loss. We use the battery data from actual sensors to evaluate the performance of our protocol. The results
show that the battery-aware protocol proposed in this paper performs well and can save a significant amount of energy compared
to existing routing protocols for streaming data transmissions. Network lifetime is also prolonged with maximum data throughput.
As far as we know, this is the first work considering battery-awareness with an accurate analytical on-line computable battery
model in sensor network routing. We believe the battery model can be used to explore other energy efficient schemes for wireless
networks as well. 相似文献
15.
分布存储多机系统中的消息传递技术 总被引:9,自引:1,他引:8
本文回顾了分布存储多机系统中消息传递技术几十年来的发展,介绍了现阶段消息传递技术的主要研究成果,例如wormhole寻径技术,虚通道流控制技术等。最后,对消息传递技术今后的研究方向作出了一些设想。 相似文献
16.
17.
B. Bary 《Cement and Concrete Research》2006,36(11):2061-2073
In this paper, the porosity of cementitious materials is described in terms of pore size distribution by means of a 3-dimensional overlapping sphere system with polydispersivity in size. On the basis of results established by Lu and Torquato [B. Lu, S. Torquato, Nearest-surface distribution functions for polydispersed particle systems, Phys. Rev. A 45(8) (1992) 5530-5544] and Torquato [S. Torquato, Random Heterogeneous Media: Microstructure and Macroscopic Properties. Springer-Verlag: New York, 2001] providing relations for nearest-neighbor distribution functions, the volume fraction of pores having a radius larger than a prescribed value is explicitly expressed. By adopting an appropriate size distribution function for the sphere system, it is shown that the pore size distribution of cementitious materials as detected for instance by mercury intrusion porosimetry (MIP), which generally points out several pore classes, can be well approached. On the basis of this porosity representation, the evaluation of the capillary pressure in function of the saturation degree is provided. The model is then applied to the simulation of the saturation degree versus relative humidity adsorption curves. The impact of the pore size distribution, the temperature and the thickness of the adsorbed water layer on these parameters are assessed and analyzed for three model materials having different pore characteristics. 相似文献
18.
A novel dynamic survivable routing in WDM optical networks with/without sparse wavelength conversion
Vinh Trong Le Xiaohong Jiang Son Hong Ngo Susumu Horiguchi Yasushi Inoguchi 《Optical Switching and Networking》2006,3(3-4):173-190
In this paper, we study the dynamic survivable routing problem, both in optical networks without wavelength conversion and in optical networks with sparse wavelength conversion, and propose a novel hybrid algorithm for it based on the combination of mobile agents technique and genetic algorithms (GA). By keeping a suitable number of mobile agents in the network to cooperatively explore the network states and continuously report cycles (that are formed by two disjoint-link routes) into the routing tables, our new hybrid algorithm can promptly determine the first population of cycles for a new request based on the routing table of its source node, without the time consuming process associated with current GA-based lightpath protection schemes. We further improve the performance of our algorithm by introducing a more advanced fitness function that is suitable for both the above networks. Extensive simulation studies on the ns-2 network simulator show that our hybrid algorithm achieves a significantly lower blocking probability than the conventional survivable routing algorithms for all the cases we studied. 相似文献
19.
20.
武钢氧气公司在大型空分设备循环冷却水系统中,采用化学法和物理法进行水处理效果的实践探索,从原理和监测数据上进行了对比、分析研究,确认物理法具有高效除垢、防垢、杀菌灭藻、缓蚀以及净化等功能,可以取代化学法进行循环水处理。 相似文献