全文获取类型
收费全文 | 48402篇 |
免费 | 14956篇 |
国内免费 | 475篇 |
专业分类
电工技术 | 1261篇 |
综合类 | 705篇 |
化学工业 | 18847篇 |
金属工艺 | 961篇 |
机械仪表 | 1468篇 |
建筑科学 | 2444篇 |
矿业工程 | 250篇 |
能源动力 | 1158篇 |
轻工业 | 7701篇 |
水利工程 | 459篇 |
石油天然气 | 566篇 |
武器工业 | 81篇 |
无线电 | 8241篇 |
一般工业技术 | 12649篇 |
冶金工业 | 1009篇 |
原子能技术 | 182篇 |
自动化技术 | 5851篇 |
出版年
2024年 | 56篇 |
2023年 | 207篇 |
2022年 | 353篇 |
2021年 | 664篇 |
2020年 | 1745篇 |
2019年 | 3406篇 |
2018年 | 3386篇 |
2017年 | 3779篇 |
2016年 | 4189篇 |
2015年 | 4281篇 |
2014年 | 4361篇 |
2013年 | 5588篇 |
2012年 | 3329篇 |
2011年 | 3092篇 |
2010年 | 3229篇 |
2009年 | 3066篇 |
2008年 | 2581篇 |
2007年 | 2403篇 |
2006年 | 2175篇 |
2005年 | 1753篇 |
2004年 | 1699篇 |
2003年 | 1790篇 |
2002年 | 1819篇 |
2001年 | 1574篇 |
2000年 | 1374篇 |
1999年 | 715篇 |
1998年 | 245篇 |
1997年 | 198篇 |
1996年 | 170篇 |
1995年 | 117篇 |
1994年 | 106篇 |
1993年 | 79篇 |
1992年 | 57篇 |
1991年 | 59篇 |
1990年 | 45篇 |
1989年 | 32篇 |
1988年 | 20篇 |
1987年 | 17篇 |
1986年 | 24篇 |
1985年 | 13篇 |
1984年 | 9篇 |
1983年 | 7篇 |
1982年 | 4篇 |
1981年 | 5篇 |
1980年 | 5篇 |
1979年 | 3篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1973年 | 1篇 |
1890年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
The purpose of this study was to analyse the adoption of crisis preparedness measures by meeting planners. The study sought to determine how the adoption of crisis preparedness measures relates to meeting planner characteristics and identify the elements that influence their adoption (or lack of adoption) of these measures. A survey of professional meeting planners identified significant differences in the frequency of use of some key core crisis preparedness measures. Additionally, 10 categories of elements influencing the adoption of or failure to adopt crisis preparedness measures were identified. The findings of this study should be of interest to meeting organizers and professionals who want to make their meetings more crisis prepared rather than crisis prone. 相似文献
992.
In this paper, we construct fuzzy renewal processes involving fuzzy random variables. We first extend the renewal processes to the fuzzy renewal processes where interarrival times, rewards, and stopping times are all fuzzy random variables. According to these fuzzy renewal processes, we then extend some theorems of renewal processes to those in fuzzy renewal processes. These are elementary renewal theorem, asymptotic expected average reward, and Wald's equation. In each part, we also give examples for applications. © 2010 Wiley Periodicals, Inc. 相似文献
993.
Kyung Min ByunAuthor VitaeNak-Hyeon KimAuthor Vitae Yeong Hwan KoAuthor VitaeJae Su YuAuthor Vitae 《Sensors and actuators. B, Chemical》2011,155(1):375-379
We demonstrated an enhanced surface plasmon resonance detection incorporating ZnO nanorod arrays (NRAs) built on a thin gold film. ZnO NRAs were fabricated by wet chemical growth method and used for the detection of DNA hybridization. Experimental results exhibited that ZnO NRAs provided a notable sensitivity improvement by more than 3 times, which is attributed to an increase in the surface reaction area. The measured sensitivity enhancement matched well with the numerical analyses based on the effective medium theory. Our approach is intended to show the feasibility and extend the applicability of the ZnO-based SPR biosensor to diverse biomolecular binding events. 相似文献
994.
Quay cranes (QCs) are the most important equipment for vessel operation in container terminals. It is important to efficiently
schedule the operations of QCs so that a high productivity may be achieved in terminals. Because the storage yard is shared
by multiple vessels, where the congestion of yard cranes and yard trucks must be considered, the operations of QCs for multiple
vessels must be simultaneously considered for QC scheduling. The objective terms include the QC make-span, the total traveling
distance of QCs, the expected delay time from interference, and the uniformity of workload among blocks. This study suggests
a heuristic algorithm based on a meta-heuristic search algorithm. Finally, a numerical experiment is carried out to test the
performance of the algorithm. 相似文献
995.
996.
In automated container terminals, containers are transported from the marshalling yard to a ship and vice versa by automated vehicles. The automated vehicle type studied in this paper is an automated lifting vehicle (ALV) that is capable of lifting a container from the ground by itself. This study discusses how to dispatch ALVs by utilizing information about pickup and delivery locations and time in future delivery tasks. A mixed-integer programming model is provided for assigning optimal delivery tasks to ALVs. A procedure for converting buffer constraints into time window constraints and a heuristic algorithm for overcoming the excessive computational time required for solving the mathematical model are suggested. Numerical experiments are reported to compare the objective values and computational times by a heuristic algorithm with those by an optimizing method and to analyze the effects of dual cycle operation, number of ALVs, and buffer capacity on the performance of ALVs. 相似文献
997.
Due to the deficiency of information, the membership function of a fuzzy variable cannot be obtained explicitly. It is a challenging work to find an appropriate membership function when certain partial information about a fuzzy variable is given, such as expected value or moments. This paper solves such problems for discrete fuzzy variables via maximum entropy principle and proves some maximum entropy theorems with certain constraints. A genetic algorithm is designed to solve the general maximum entropy model for discrete fuzzy variables, which is illustrated by some numerical experiments. 相似文献
998.
In overlay networks, the network characteristics before and after a vertical handoff would be drastically different. Consequently, in this paper, we propose an end‐to‐end based scheme to support protocol and application adaptation in vertical handoffs. First, we proposed a Vertical‐handoff Aware TCP, called VA‐TCP. VA‐TCP can identify the packet losses caused by vertical handoffs. If segments losses are due to vertical handoffs, VA‐TCP only retransmits the missing segments but does not invoke the congestion control procedure. Moreover, VA‐TCP dynamically estimates the bandwidth and round‐trip time in a new network. Based on the estimated bandwidth and round‐trip time, VA‐TCP adjusts its parameters to respond to the new network environment. Second, during a vertical handoff, applications also need to be adapted accordingly. Therefore, we design a programming interface that allows applications to be notified upon and adapt to changing network environments. To support our interface, we utilize the signal mechanism to achieve kernel‐to‐user notification. Nevertheless, signals cannot carry information. Thus, we implement the shared memory mechanism between applications and the kernel to facilitate parameters exchange. Finally, we also provide a handoff‐aware CPU scheduler so that tasks that are interested in the vertical‐handoff event are given preference over other processes to attain a prompt response for new network conditions. We have implemented a prototype system on the Linux kernel 2.6. From the experimental results, our proposed protocol and application adaptation mechanisms are shown to effectively improve the performance of TCP and applications during vertical handoffs. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
999.
We present a compiler that can be used to automatically obtain efficient Java implementations of parsing algorithms from formal specifications expressed as parsing schemata. The system performs an analysis of the inference rules in the input schemata in order to determine the best data structures and indexes to use, and to ensure that the generated implementations are efficient. The system described is general enough to be able to handle all kinds of schemata for different grammar formalisms, such as context‐free grammars and tree‐adjoining grammars, and it provides an extensibility mechanism allowing the user to define custom notational elements. This compiler has proven very useful for analyzing, prototyping and comparing natural‐language parsers in real domains, as can be seen in the empirical examples provided at the end of the paper. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
1000.