全文获取类型
收费全文 | 59766篇 |
免费 | 8059篇 |
国内免费 | 3336篇 |
专业分类
电工技术 | 9850篇 |
技术理论 | 5篇 |
综合类 | 5911篇 |
化学工业 | 10739篇 |
金属工艺 | 1737篇 |
机械仪表 | 3619篇 |
建筑科学 | 8315篇 |
矿业工程 | 1282篇 |
能源动力 | 6093篇 |
轻工业 | 1452篇 |
水利工程 | 1812篇 |
石油天然气 | 1607篇 |
武器工业 | 472篇 |
无线电 | 3636篇 |
一般工业技术 | 6029篇 |
冶金工业 | 1836篇 |
原子能技术 | 906篇 |
自动化技术 | 5860篇 |
出版年
2024年 | 245篇 |
2023年 | 999篇 |
2022年 | 1724篇 |
2021年 | 2006篇 |
2020年 | 2121篇 |
2019年 | 1885篇 |
2018年 | 1748篇 |
2017年 | 2055篇 |
2016年 | 2179篇 |
2015年 | 2396篇 |
2014年 | 3689篇 |
2013年 | 3755篇 |
2012年 | 4172篇 |
2011年 | 4693篇 |
2010年 | 3489篇 |
2009年 | 3595篇 |
2008年 | 3452篇 |
2007年 | 3982篇 |
2006年 | 3624篇 |
2005年 | 3205篇 |
2004年 | 2556篇 |
2003年 | 2364篇 |
2002年 | 1904篇 |
2001年 | 1572篇 |
2000年 | 1331篇 |
1999年 | 1093篇 |
1998年 | 863篇 |
1997年 | 783篇 |
1996年 | 679篇 |
1995年 | 564篇 |
1994年 | 446篇 |
1993年 | 350篇 |
1992年 | 315篇 |
1991年 | 220篇 |
1990年 | 223篇 |
1989年 | 194篇 |
1988年 | 162篇 |
1987年 | 99篇 |
1986年 | 76篇 |
1985年 | 62篇 |
1984年 | 77篇 |
1983年 | 53篇 |
1982年 | 38篇 |
1981年 | 17篇 |
1980年 | 16篇 |
1979年 | 8篇 |
1978年 | 4篇 |
1966年 | 8篇 |
1959年 | 15篇 |
1951年 | 28篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
51.
A Distributed Virtual Environment (DVE) system offers a computer-generated virtual world in which individuals located at different
places in the physical world can interact with one another. In order to achieve real-time response for a large user base,
DVE systems need to have a scalable architecture. In this paper, we present the design of a grid-enabled service oriented
framework for facilitating the construction of scalable DVE systems on computing grids. A service component called “gamelet”
is proposed, whose distinctive mark is its high mobility for supporting dynamic load sharing. We propose a gamelet migration
protocol which can ensure the transparency and efficiency of gamelet migration, and an adaptive gamelet load-balancing (AGLB)
algorithm for making gamelet redistribution decisions at runtime. The algorithm considers both the synchronization costs of
the DVE system and network latencies inherent in the grid nodes. The activities of the users and the heterogeneity of grid
resources are also considered in order to carry out load sharing more effectively. We evaluate the performance of the proposed
mechanisms through a multiplayer online game prototype implemented using the Globus toolkit. The results show that our approach
can achieve faster response times and higher throughputs than some existing approaches.
This research is supported in part by the China National Grid project (863 program) and the HKU Foundation Seed Grant 28506002. 相似文献
52.
53.
异构分层无线网络中基于逗留时间的动态流量均衡算法研究 总被引:1,自引:1,他引:0
为使异构分层无线网络能服务更多的移动用户,提出了一种基于逗留时间的动态流量均衡算法.该算法首先根据用户移动模型计算其在小区内的逗留时间,然后基于小区呼叫到达率和重叠覆盖小区的流量状态来确定一个周期内呼叫转移的数量,最后依据逗留时间门限值将重负载小区中满足条件的呼叫转移到轻负载的重叠覆盖小区中.为降低切换呼叫掉线率,还对异构网间的呼叫切换策略做了改进.仿真实验结果表明,本算法在新呼叫阻塞率和切换呼叫掉线率等性能指标上比传统方法有显著的提高. 相似文献
54.
The applicability of the identical elements (IE) model of arithmetic fact retrieval (T. C. Rickard, A. F. Healy, & L. E. Bourne, 1994) to cued recall from episodic (image and sentence) memory was explored in 3 transfer experiments. In agreement with results from arithmetic, speedup following even minimal practice recalling a missing word from an episodically bound word triplet did not transfer positively to other cued recall items involving the same triplet. The shape of the learning curve further supported a shift from episode-based to IE-based recall, extending some models of skill learning to cued recall practice. In contrast with previous findings, these results indicate that a form of representation that is independent of the original episodic memory underlies cued-recall performance following minimal practice. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
55.
56.
对CFG桩质量缺陷的探讨 总被引:2,自引:2,他引:0
根据具体工程的概况及水文地质条件,分析了CFG桩在地下水位出现大面积缩颈现象和复合地基载荷试验达不到设计要求的原因,并介绍了地基补强措施,以满足工程质量的要求。 相似文献
57.
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
58.
59.
G. Casalbore‐Miceli M.C. Gallazzi S. Zecchin N. Camaioni A. Geri C. Bertarelli 《Advanced functional materials》2003,13(4):307-312
Voltammetric and spectrophotometric measurements of poly(3,3″‐dipentoxy‐3′‐dicyanoethenyl‐2,2′:5′,2″‐terthiophene) (polyCN) films, in connection with other experimental evidence, reveal a normal oxidative, but a peculiar reductive behavior consisting of trapping of the negative charge during the cathodic scan. Another interesting property of polyCN films is the tendency to form strong intramolecular and intermolecular associations, probably charge‐transfer (CT) complexes. These properties could account for the fact that the photovoltaic performance does not improve when polyCN is blended with a polythiophene donor. 相似文献
60.
Communicating with sensors has long been limited either to wired connections or to proprietary wireless communication protocols. Using a ubiquitous and inexpensive wireless communication technology to create Sensor Area Networks (SANs) will accelerate the extensive deployment of sensor technology. Bluetooth, an emerging, worldwide standard for inexpensive, local wireless communication is a viable choice for SANs because of its inherent support for some of the important requirements – low power, small form factor, low cost and sufficient communication range. In this paper we outline an approach, centered on the Bluetooth technology, to support a sensor network composed of fixed wireless sensors for health monitoring of highways, bridges and other civil infrastructures. We present a topology formation scheme that not only takes into account the traffic generated by different sensors but also the associated link strengths, buffer capacities and energy availability. The algorithm makes no particular assumptions as to the placement of nodes, and not all nodes need to be in radio proximity of each other. The output is a tree shaped scatternet rooted at the sensor hub (data logger) that is balanced in terms of traffic carried on each of the links. We also analyze the scheduling, routing and healing aspects of the resulting sensor-net topology. 相似文献