全文获取类型
收费全文 | 26483篇 |
免费 | 1566篇 |
国内免费 | 1259篇 |
专业分类
电工技术 | 1599篇 |
技术理论 | 1篇 |
综合类 | 1666篇 |
化学工业 | 398篇 |
金属工艺 | 504篇 |
机械仪表 | 2222篇 |
建筑科学 | 668篇 |
矿业工程 | 516篇 |
能源动力 | 313篇 |
轻工业 | 194篇 |
水利工程 | 230篇 |
石油天然气 | 842篇 |
武器工业 | 393篇 |
无线电 | 3793篇 |
一般工业技术 | 1003篇 |
冶金工业 | 521篇 |
原子能技术 | 434篇 |
自动化技术 | 14011篇 |
出版年
2024年 | 55篇 |
2023年 | 208篇 |
2022年 | 326篇 |
2021年 | 453篇 |
2020年 | 499篇 |
2019年 | 338篇 |
2018年 | 382篇 |
2017年 | 612篇 |
2016年 | 679篇 |
2015年 | 814篇 |
2014年 | 1529篇 |
2013年 | 1292篇 |
2012年 | 1732篇 |
2011年 | 2109篇 |
2010年 | 1369篇 |
2009年 | 1358篇 |
2008年 | 1581篇 |
2007年 | 1973篇 |
2006年 | 1864篇 |
2005年 | 1801篇 |
2004年 | 1549篇 |
2003年 | 1416篇 |
2002年 | 1055篇 |
2001年 | 754篇 |
2000年 | 635篇 |
1999年 | 536篇 |
1998年 | 417篇 |
1997年 | 326篇 |
1996年 | 283篇 |
1995年 | 260篇 |
1994年 | 191篇 |
1993年 | 143篇 |
1992年 | 95篇 |
1991年 | 86篇 |
1990年 | 71篇 |
1989年 | 70篇 |
1988年 | 64篇 |
1987年 | 42篇 |
1986年 | 42篇 |
1985年 | 46篇 |
1984年 | 40篇 |
1983年 | 29篇 |
1982年 | 27篇 |
1981年 | 28篇 |
1980年 | 18篇 |
1979年 | 14篇 |
1978年 | 17篇 |
1977年 | 15篇 |
1976年 | 31篇 |
1975年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
52.
D.H.R. Price J.A. Sharp 《International Journal of Electrical Power & Energy Systems》1985,7(3):131-137
Peak demand forecasts obtained from six different univariate forecasting methods, under a range of conditions, were used to drive a capacity acquisition model of a large electrical supply system; and the resulting physical and financial performance of the model was observed for each set of forecasts. The results obtained are discussed in the context of their implications for the choice of load forecasting method used in capacity acquisition planning by a power supply undertaking. 相似文献
53.
Roberson Debi; Davidoff Jules; Davies Ian R. L.; Shapiro Laura R. 《Canadian Metallurgical Quarterly》2004,133(4):554
This study unites investigations into the linguistic relativity of color categories with research on children's category acquisition. Naming, comprehension, and memory for colors were tracked in 2 populations over a 3-year period. Children from a seminomadic equatorial African culture, whose language contains 5 color terms, were compared with a group of English children. Despite differences in visual environment, language, and education, they showed similar patterns of term acquisition. Both groups acquired color vocabulary slowly and with great individual variation. Those knowing no color terms made recognition errors based on perceptual distance, and the influence of naming on memory increased with age. An initial perceptually driven color continuum appears to be progressively organized into sets appropriate to each culture and language. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
54.
The acquisition of new skills over a life span is a remarkable human ability. This ability, however, is constrained by age of acquisition (AoA); that is, the age at which learning occurs significantly affects the outcome. This is most clearly reflected in domains such as language, music, and athletics. This article provides a perspective on the neural and computational mechanisms underlying AoA in language acquisition. The authors show how AoA modulates both monolingual lexical processing and bilingual language acquisition. They consider the conditions under which syntactic processing and semantic processing may be differentially sensitive to AoA effects in second-language acquisition. The authors conclude that AoA effects are pervasive and that the neural and computational mechanisms underlying learning and sensorimotor integration provide a general account of these effects. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
55.
Takeshi Kondo Sang Min Lee Michal Malicki Benoit Domercq Seth R. Marder Bernard Kippelen 《Advanced functional materials》2008,18(7):1112-1118
We report on a single‐layer organic memory device made of poly(N‐vinylcarbazole) embedded between an Al electrode and ITO modified with Ag nanodots (Ag‐NDs). Devices exhibit high ON/OFF switching ratios of 104. This level of performance could be achieved by modifying the ITO electrodes with some Ag‐NDs that act as trapping sites, reducing the current in the OFF state. Temperature dependence of the electrical characteristics suggest that the current of the low‐resistance state can be attributed to Schottky charge tunnelling through low‐resistance pathways of Al particles in the polymer layer and that the high‐resistance state can be controlled by charge trapping by the Al particles and Ag‐NDs. 相似文献
56.
A new type of a single-axis azimuthal tracker is presented. The novel feature of this tracker is the ability to move the collector’s plane in two directions through a special support structure. This structure consists of a sliding mechanism on the central axis and a curved window on the cylindrical surface coaxial to the central axis. Consequently, the proposed novel heliotrope behaves similarly to a two-axis tracker. Two different windows designed on the cylindrical surface may be used to provide very high efficiencies throughout a year. Several performance measurements have been conducted on this novel tracker, a polar tracker and the reference two-axis tracker. Pyranometers, appropriately calibrated, were installed on all three systems to record the global incoming irradiance on the collector’s plane. It is shown that the new tracker system can be very efficient since its plane intercepts, at least, 98% of the insolation with respect to a two-axis tracker. The proposed system can be utilized in solar-related applications (photovoltaic or thermal). 相似文献
57.
说明了在异步串行通信(RS-232)的工作方式下,对所接收的数据进行接收、处理,丢弃乱码,并进行保存的可靠方法,并给出了相关的VC 语言程序. 相似文献
58.
Dealing with discrepancies in data is still a big challenge in data integration systems. The problem occurs both during eliminating duplicates from semantic overlapping sources as well as during combining complementary data from different sources. Though using SQL operations like grouping and join seems to be a viable way, they fail if the attribute values of the potential duplicates or related tuples are not equal but only similar by certain criteria. As a solution to this problem, we present in this paper similarity-based variants of grouping and join operators. The extended grouping operator produces groups of similar tuples, the extended join combines tuples satisfying a given similarity condition. We describe the semantics of this operator, discuss efficient implementations for the edit distance similarity and present evaluation results. Finally, we give examples of application from the context of a data reconciliation project for looted art. 相似文献
59.
60.
基于DMF捕获系统频率选择性信道下捕获性能的分析 总被引:1,自引:0,他引:1
对基于数字匹配滤波器(DMF)捕获系统在频率选择性信道下的捕获性能进行了深入讨论,利用状态转移图推导出单次驻留判决方式时平均捕获时间的表达式,对平均捕获时间与多径分量的关系进行了数字分析。得出的主要结论是:对于多径分量为非衰落信号时,多径分量之间的能量差别越大,系统捕获性能越好,多径分量的能量相等时,系统捕获性能最差,且随着可以分离的多径路数的增加下降;对于多径分量为慢衰落信号时,多径信道的捕获性能好于单径信道(非频率选择性衰落信道),且多径分量之间的能量差别越大,系统捕获性能越差,当多径分量的能量相等时,捕获性能最好,这与非衰落信道的情形相反。因此在频率选择性衰落信道中,采用分集接收可以改善系统的捕获性能。 相似文献