全文获取类型
收费全文 | 1238篇 |
免费 | 68篇 |
国内免费 | 18篇 |
专业分类
电工技术 | 16篇 |
综合类 | 4篇 |
化学工业 | 327篇 |
金属工艺 | 34篇 |
机械仪表 | 32篇 |
建筑科学 | 24篇 |
能源动力 | 43篇 |
轻工业 | 53篇 |
水利工程 | 1篇 |
无线电 | 243篇 |
一般工业技术 | 222篇 |
冶金工业 | 103篇 |
原子能技术 | 2篇 |
自动化技术 | 220篇 |
出版年
2023年 | 11篇 |
2022年 | 26篇 |
2021年 | 35篇 |
2020年 | 16篇 |
2019年 | 24篇 |
2018年 | 27篇 |
2017年 | 31篇 |
2016年 | 37篇 |
2015年 | 33篇 |
2014年 | 71篇 |
2013年 | 107篇 |
2012年 | 59篇 |
2011年 | 72篇 |
2010年 | 64篇 |
2009年 | 76篇 |
2008年 | 66篇 |
2007年 | 69篇 |
2006年 | 56篇 |
2005年 | 42篇 |
2004年 | 37篇 |
2003年 | 36篇 |
2002年 | 34篇 |
2001年 | 22篇 |
2000年 | 21篇 |
1999年 | 16篇 |
1998年 | 48篇 |
1997年 | 29篇 |
1996年 | 17篇 |
1995年 | 17篇 |
1994年 | 16篇 |
1993年 | 13篇 |
1992年 | 5篇 |
1991年 | 6篇 |
1990年 | 3篇 |
1989年 | 10篇 |
1988年 | 7篇 |
1986年 | 5篇 |
1985年 | 9篇 |
1984年 | 9篇 |
1983年 | 3篇 |
1982年 | 6篇 |
1981年 | 4篇 |
1980年 | 2篇 |
1979年 | 4篇 |
1978年 | 2篇 |
1977年 | 3篇 |
1976年 | 3篇 |
1975年 | 3篇 |
1974年 | 3篇 |
1970年 | 2篇 |
排序方式: 共有1324条查询结果,搜索用时 0 毫秒
71.
Byrne Peter Tangney Brendan Sanchez-Villalon Pedro P. Ortega Manuel Wu Lin-Jung Chang Kao-En Hsiao Hsien-Sheng Sung Yao-Ting 《Distributed Systems Online, IEEE》2007,8(7):3-3
Works in progress from selected papers presented at the 2006 IADIS International Conference on Mobile Learning provide an overview of the diverse research being conducted in this field. 相似文献
72.
Investigation of the Phase Equilibria of Sn-Cu-Au Ternary and Ag-Sn-Cu-Au Quaternary Systems and Interfacial Reactions in Sn-Cu/Au Couples 总被引:1,自引:0,他引:1
Yee-Wen Yen Chien-Chung Jao Hsien-Ming Hsiao Chung-Yung Lin Chiapyng Lee 《Journal of Electronic Materials》2007,36(2):147-158
The phase equilibria of the Sn-Cu-Au ternary, Ag-Sn-Cu-Au quaternary systems and interfacial reactions between Sn-Cu alloys
and Au were experimentally investigated at specific temperatures in this study. The experimental results indicated that there
existed three ternary intermetallic compounds (IMCs) and a complete solid solubility between AuSn and Cu6Sn5 phases in the Sn-Cu-Au ternary system at 200°C. No quaternary IMC was found in the isoplethal section of the Ag-Sn-Cu-Au
quaternary system. Three IMCs, AuSn, AuSn2, and AuSn4, were found in all couples. The same three IMCs and (Au,Cu)Sn/(Cu,Au)6Sn5 phases were found in all Sn-Cu/Au couples. The thickness of these reaction layers increased with increasing temperature and
time. The mechanism of IMC growth can be described by using the parabolic law. In addition, when the reaction time was extended
and the Cu content of the alloy was increased, the AuSn4 phase disappeared gradually. The (Au, Cu)Sn and (Cu,Au)6Sn5 layers played roles as diffusion barriers against Sn in Sn-Cu/Au reaction couple systems. 相似文献
73.
74.
75.
The set of frequent closed itemsets uniquely determines the exact frequency of all itemsets, yet it can be orders of magnitude smaller than the set of all frequent itemsets. In this paper, we present CHARM, an efficient algorithm for mining all frequent closed itemsets. It enumerates closed sets using a dual itemset-tidset search tree, using an efficient hybrid search that skips many levels. It also uses a technique called diffsets to reduce the memory footprint of intermediate computations. Finally, it uses a fast hash-based approach to remove any "nonclosed" sets found during computation. We also present CHARM-L, an algorithm that outputs the closed itemset lattice, which is very useful for rule generation and visualization. An extensive experimental evaluation on a number of real and synthetic databases shows that CHARM is a state-of-the-art algorithm that outperforms previous methods. Further, CHARM-L explicitly generates the frequent closed itemset lattice. 相似文献
76.
Taiwan computer firms need to forecast trends in notebook shipments. The Bass diffusion model has been successfully applied to describe the empirical adoption curve for many new products and technological innovations. In order to improve the parameter estimates, a hybrid evolutionary algorithm, which couples genetic algorithms (GAs) with particle swarm optimization (PSO), is proposed. This hybrid approach can produce more accurate estimates of the parameters for the Bass diffusion model. In addition, the price index plays an important role in the notebook market. Thus, the modified diffusion model is proposed to investigate the forecasting performance for notebook shipments. The results illustrate that a hybrid approach outperforms other methods such as nonlinear algorithm, GA and PSO in terms of mean absolute percentage error. 相似文献
77.
Patel (1981) proposed a probabilistic approach to analyze the performance of synchronous multistage interconnection networks (MINs) based on a uniform reference model and the assumption of independent requests. Patel's model and analytical results have been widely adopted by numerous researchers as a basis to investigate various aspects of MINs. We study in detail the effects of the independence assumption on the accuracy of system performance and point out the factors which cause an inaccuracy. A new queueing model is then proposed and is shown to be very accurate. Since only six states are needed, independent of the size of MINs, this new model is very efficient computationally 相似文献
78.
With the growing number of routing entries, IP routing lookup has become the major performance bottleneck in backbone routers. In this paper, a complete hardware-based routing lookup system is proposed to achieve high-throughput and high-capacity for IPv6. The proposed system is a cache-centric, hash-based architecture that contains a routing lookup application specific integrated circuit (ASIC) and a memory set. A hash function is used to reduce lookup time for the routing table and ternary content addressable memory (TCAM) effectively resolves the collision problem. The gate count of the ASIC, excluding the binary content addressable memory (BCAM), is about 5306 gates, using an in-house 0.18 μm CMOS single-poly six-metal standard cell library. The results of post-layout simulations show that the ASIC operates in 3.6 ns so that the routing lookup system approaches 260 Mega lookups per second (Mlps), which is sufficient for 100 Gbps networks. The memory density is good, with each routing entry requiring only 64 bits. Moreover, the routing table only needs 10.24 KB on-chip BCAM, 20.04 KB off-chip TCAM and 29.29 MB DRAM for 3.6 M routing entries in the proposed system. 相似文献
79.
A median-filter-based ambiguity removal algorithm for NSCAT 总被引:5,自引:0,他引:5
80.
Three common phthalates, namely, dioctyl phthalate, diisodecyl phthalate, and trioctyl trimellitate, were used as plasticizers for poly(vinyl chloride) (PVC) processing, and the extraction of these plasticizers were investigated using supercritical CO2 fluids. Factors affecting the extractions of these phthalates were focused. The molecular weight of phthalates was found to dominate the level of extraction of low temperatures, whereas the content of carbonyl groups in the phthalate was a determining factor for the level of extraction of high temperatures. Negligible extraction was observed below the critical pressure of CO2. For 32°C, the level of the extraction is insignificant below density of ca 0.7 g/cm3, above which the level of the extraction increases roughly linearly with increasing density. For temperatures above 32°C, the density of CO2 for apparent extractions decreased with increasing temperatures. The threshold density of CO2 for extractions was found to be independent of the amount of a given phthalate in PVC. Two extraction rates during the extraction could be determined, with a higher rate in the first hour followed by a lower rate later in the extraction for all three phthalates. The effects of the extractions of phthalates on the flexibility of PVC were also investigated as well as the effects of the extrusion conditions, which could lead to various degrees of plasticization of PVC, on the level of extractions. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 4032–4037, 2003 相似文献