全文获取类型
收费全文 | 9854篇 |
免费 | 806篇 |
国内免费 | 576篇 |
专业分类
电工技术 | 322篇 |
技术理论 | 1篇 |
综合类 | 560篇 |
化学工业 | 1259篇 |
金属工艺 | 2260篇 |
机械仪表 | 904篇 |
建筑科学 | 106篇 |
矿业工程 | 148篇 |
能源动力 | 299篇 |
轻工业 | 721篇 |
水利工程 | 63篇 |
石油天然气 | 418篇 |
武器工业 | 80篇 |
无线电 | 654篇 |
一般工业技术 | 1170篇 |
冶金工业 | 833篇 |
原子能技术 | 94篇 |
自动化技术 | 1344篇 |
出版年
2024年 | 35篇 |
2023年 | 162篇 |
2022年 | 343篇 |
2021年 | 389篇 |
2020年 | 322篇 |
2019年 | 283篇 |
2018年 | 251篇 |
2017年 | 298篇 |
2016年 | 337篇 |
2015年 | 400篇 |
2014年 | 499篇 |
2013年 | 567篇 |
2012年 | 611篇 |
2011年 | 699篇 |
2010年 | 534篇 |
2009年 | 595篇 |
2008年 | 506篇 |
2007年 | 593篇 |
2006年 | 534篇 |
2005年 | 498篇 |
2004年 | 417篇 |
2003年 | 383篇 |
2002年 | 353篇 |
2001年 | 303篇 |
2000年 | 253篇 |
1999年 | 227篇 |
1998年 | 150篇 |
1997年 | 138篇 |
1996年 | 112篇 |
1995年 | 97篇 |
1994年 | 84篇 |
1993年 | 51篇 |
1992年 | 48篇 |
1991年 | 41篇 |
1990年 | 31篇 |
1989年 | 24篇 |
1988年 | 14篇 |
1987年 | 8篇 |
1986年 | 6篇 |
1985年 | 2篇 |
1984年 | 10篇 |
1983年 | 3篇 |
1982年 | 3篇 |
1981年 | 6篇 |
1978年 | 2篇 |
1975年 | 3篇 |
1958年 | 2篇 |
1957年 | 1篇 |
1955年 | 2篇 |
1954年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
Wireless sensor networks (WSNs) are a kind of communication networks having independent sensor nodes that form multi-hop ad hoc network to transfer data. In the past few years, various transport control protocols in wireless sensor networks (WSNs) have been developed and proposed in the literature. In this paper, we have analyzed pump slowly, fetch quickly (PSFQ) protocol and presented an improved transport layer protocol for wireless sensor networks. The improved protocol has been analyzed based on various factors such as average latency and average error tolerance and it is found that the proposed protocol is better than PSFQ in terms of these factors. 相似文献
82.
利用热力学基础数据和相关软件对F-T合成催化剂COS和H_2S中毒的热力学进行了计算。在热力学上,Ru、Fe、Co的COS中毒在F-T合成反应可以发生的条件下均是自发过程。F-T合成反应体系中10~(-9)级的COS即可使Ru基催化剂中的金属Ru生成RuS_2而中毒。Fe和Co毒化后生成的硫化物种类较多,对这些反应的热力学计算结果表明,对于不同的反应,其平衡常数的差异很大,对应中毒反应发生时,所需的COS和H_2S的浓度也不同,对COS的要求更为严格。由于Fe基F-T合成催化剂活性相的复杂性,利用对催化剂相关性质的修饰开发具有一定抗硫性的铁基F-T合成催化剂是可行的;对于Co催化剂,利用F-T合成的反应特点和催化剂改性开发具有一定抗硫性催化剂是可能的。 相似文献
83.
Similarity relations in concept lattices 总被引:6,自引:0,他引:6
84.
Failure detection and consensus in the crash-recovery model 总被引:2,自引:0,他引:2
Summary. We study the problems of failure detection and consensus in asynchronous systems in which processes may crash and recover,
and links may lose messages. We first propose new failure detectors that are particularly suitable to the crash-recovery model.
We next determine under what conditions stable storage is necessary to solve consensus in this model. Using the new failure
detectors, we give two consensus algorithms that match these conditions: one requires stable storage and the other does not.
Both algorithms tolerate link failures and are particularly efficient in the runs that are most likely in practice – those
with no failures or failure detector mistakes. In such runs, consensus is achieved within time and with 4 n messages, where is the maximum message delay and n is the number of processes in the system.
Received: May 1998 / Accepted: November 1999 相似文献
85.
由于连入Internet,为用户提供各种信息服务。资源共享和开放是Internet特点,因而Internet的安全机制很松散,而用户对网络信息系统要求有较高的安全性,其内部的许多数据和文件严禁未经授权的访问。因此,设计与开发保证内部各种信息的安全机制是实现该网络顺利运行的关键。 相似文献
86.
Abstract— Bit‐partitioned and conventional shifts, as well as type transformations of multimedia data, are frequently used for display image‐processing systems. A data manipulation unit with fault‐recovery capability based on redundancies is proposed for system‐on‐panel with low processing technology yield. Utilizing data manipulations that are similar to normal shift operation, a proposed data‐manipulation unit is designed with a few additional paths added to the existing barrel shifter. The design methodologies are verified with FPGA and the performance is evaluated in terms of the advantages. 相似文献
87.
On basic properties of fault-tolerant multi-topology routing 总被引:1,自引:0,他引:1
Multi-topology routing has recently gained popularity as a simple yet efficient traffic engineering concept. Its basic purpose is to separate different classes of network traffic, which are then transported over disjoint logical topologies. Multi-topology routing is used as a basis for implementation of an IP fast reroute scheme called Multiple Routing Configurations (MRC).MRC has a range of attractive properties, but they do come at a cost. In order to guarantee recovery from any single link or node failure in the network, MRC has to maintain several logical topologies and thus an increased amount of routing information. The number of the logical topologies in MRC need not be large; even simple heuristic algorithms often yield good results in practice. However, why this is the case is not fully understood yet.In this paper, we introduce a theoretical framework for fault-tolerant multi-topology routing (FT-MTR). MRC is a practical implementation of FT-MTR in connectionless IP networks. We use FT-MTR to study how the internal topological structure of the communication network relates to two important problems. The first problem is minimizing the number of logical topologies and thus the routing state in FT-MTR. We show how to use the sets of nodes that separate the topology graph to devise an advanced heuristic for “intelligent” construction of the logical topologies. Finding the separating sets in a topology graph is computationally demanding; we present an algorithm that performs well in tested real network topologies. We evaluate the separation-set based heuristic for the logical topology construction and show that it outperforms the known MRC heuristics.The second problem is the FT-MTR load distribution after a failure. We use the separating sets to devise a novel algorithm for failure load distribution. This algorithm does not require knowledge of the traffic demand matrix, still, our tests indicate that it performs as good as, or better than, known MRC load-distribution algorithms that do require the demand matrix as input. 相似文献
88.
XIAO Hui-jun WEI Da-kuan 《通讯和计算机》2008,5(2):12-18
The Incomplete and Fuzzy Decision Information System (IFDIS) with both missing data and fuzzy decisions is rather extensively applications, which is the generalizations of complete information system, incomplete information system and fuzzy decision information system. In this paper, on the base of notion of the tolerance relation and the concept of IFDIS, the rough set model of IFDIS based on tolerance relation is proposed and the properties of the models are discussed, and then the definitions of(upper- or lower-) consistent reduction are suggested and knowledge reduction based on discernibility matrix is presented. The optimal fuzzy decision rules and its acquisition algorithm are proposed. Finally we provide an example to illustrate the validity of the algorithm. 相似文献
89.
异步传输模式ATM是国际化电信联盟建议用于宽带综合业务数字网(B-ISDN)的传输模式。容错是提高网络可靠性的主要方法。该文讨论了一种新的容错ATM交换机结构。该结构以Banyan交换机结构为基础,通过增加子交换单元和扩展链路来增加冗余路径的数目,该结构可以容错多个故障,并且冗余路径的数目随着交换机级数的增加而指数增长。同现有文献中其它容错ATM交换机对比分析可以看出,在具有相近的交换元素个数的前提下,建议的交换机提供了更高的容错能力。 相似文献
90.