全文获取类型
收费全文 | 26317篇 |
免费 | 1343篇 |
国内免费 | 130篇 |
专业分类
电工技术 | 974篇 |
综合类 | 136篇 |
化学工业 | 5394篇 |
金属工艺 | 691篇 |
机械仪表 | 652篇 |
建筑科学 | 1577篇 |
矿业工程 | 370篇 |
能源动力 | 742篇 |
轻工业 | 2302篇 |
水利工程 | 211篇 |
石油天然气 | 576篇 |
武器工业 | 7篇 |
无线电 | 2161篇 |
一般工业技术 | 4234篇 |
冶金工业 | 3493篇 |
原子能技术 | 175篇 |
自动化技术 | 4095篇 |
出版年
2023年 | 191篇 |
2022年 | 429篇 |
2021年 | 663篇 |
2020年 | 479篇 |
2019年 | 501篇 |
2018年 | 664篇 |
2017年 | 675篇 |
2016年 | 747篇 |
2015年 | 635篇 |
2014年 | 910篇 |
2013年 | 1561篇 |
2012年 | 1413篇 |
2011年 | 2374篇 |
2010年 | 1398篇 |
2009年 | 1230篇 |
2008年 | 1266篇 |
2007年 | 1200篇 |
2006年 | 1046篇 |
2005年 | 906篇 |
2004年 | 1207篇 |
2003年 | 1030篇 |
2002年 | 931篇 |
2001年 | 614篇 |
2000年 | 471篇 |
1999年 | 563篇 |
1998年 | 463篇 |
1997年 | 343篇 |
1996年 | 310篇 |
1995年 | 280篇 |
1994年 | 250篇 |
1993年 | 231篇 |
1992年 | 180篇 |
1991年 | 116篇 |
1990年 | 185篇 |
1989年 | 172篇 |
1988年 | 114篇 |
1987年 | 130篇 |
1986年 | 135篇 |
1985年 | 148篇 |
1984年 | 140篇 |
1983年 | 119篇 |
1982年 | 137篇 |
1981年 | 134篇 |
1980年 | 108篇 |
1979年 | 116篇 |
1978年 | 81篇 |
1977年 | 120篇 |
1976年 | 97篇 |
1975年 | 71篇 |
1974年 | 66篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
31.
32.
33.
太钢4号高炉喷煤站从1990年起采用MFD-Ⅲ型脉动反吹式布袋除尘器。这种除尘器采用脉动式反吹清灰设施,合理布置布袋间距,布袋支撑骨架及选用针呢材质的布袋,过滤面积大,反吹清灰效果好,设备运行平稳,除尘效率高达99.8%,排放浓度小于10mg/m^3,故障率低。 相似文献
34.
Tight frequency-to-amplitude relationships are observed in spontaneous human steady gait. If required, however, they can be modified. The following experiments were aimed at the processes underlying this flexibility, which forms the fundamental basis of the intentional adaptive capabilities of locomotion. In Exp 1, Ss had to intentionally modify the frequency-to-amplitude relationship (leading to preferred or nonpreferred steady states). In Exp 2, they had to temporarily perturbate the stride-frequency-to-amplitude relationship to intentionally shorten or lengthen 1 stride. Within the important constraints exerted by the head–arm–trunk system on leg movement, the results pointed out 2 main strategies that allow the S to intentionally adapt stride organization on-line: adjustment of the tonic properties of the oscillating leg to achieve nonpreferred steady states and phasic action to ensure temporary movement away from a steady state. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
35.
Remote sensing of species mixtures in conifer plantations using LiDAR height and intensity data 总被引:2,自引:0,他引:2
Daniel N.M. Donoghue Peter J. Watt Nicholas J. Cox Jimmy Wilson 《Remote sensing of environment》2007,110(4):509-522
In even-aged, single species conifer plantations LiDAR height data can be modelled to provide accurate estimates of tree height and volume. However, it is apparent that growth models developed for single species stands are not directly transferable to a more general situation of mixed species plantations. This paper evaluates the ability of small footprint, dual-return, pulsed airborne LiDAR data to estimate the proportion of the productive species when mixed with a nurse crop in closed canopy plantations. A study area located in Galloway Forest District in Scotland is used as an example of Lodgepole pine and Sitka spruce mixed plantation; this area contains good examples of a wide range of pure and mixed species plantation types. Three species groups are studied: areas of pure Sitka spruce, areas of pure Lodgepole pine and areas where the two species have been planted together. Two approaches are assessed for detection of plantation mixtures: the first uses LiDAR intensity data to separate spruce and pine species and the second uses LiDAR-derived canopy density measures, coefficient of variation, skewness, percent of ground returns (which provides a measure of canopy openness) and the mean canopy height, which enables areas with height variations to be identified. From analysis of LiDAR data extracted from 54 study plots using logistic regression, the coefficient of variation and LiDAR intensity data provide the most useful predictors of the proportion of spruce in a pine/spruce mixture with coefficients of determination (R2) of 0.914 and 0.930 respectively. The method could be developed as a mapping tool, which in combination with existing inventory data should help to improve timber volume forecasting for mixed species even-aged plantations. 相似文献
36.
Due to the fact that human activities and most sustainability issues are closely related to energy use, the energy system is a sound framework for providing lead indicators for sustainable development. Common energy-economic models enable the estimation of future states of the energy system. An energy system-based lead indicator set can be used to develop consistent and coherent future indicator estimates and to track sustainability, a clear advantage over existing sets. 相似文献
37.
Sven Beyer Christian Jacobi Daniel Kröning Dirk Leinenbach Wolfgang J. Paul 《International Journal on Software Tools for Technology Transfer (STTT)》2006,8(4-5):411-430
In the verified architecture microprocessor (VAMP) project we have designed, functionally verified, and synthesized a processor
with full DLX instruction set, delayed branch, Tomasulo scheduler, maskable nested precise interrupts, pipelined fully IEEE
compatible dual precision floating point unit with variable latency, and separate instruction and data caches. The verification
has been carried out in the theorem proving system PVS. The processor has been implemented on a Xilinx FPGA.
A shorter version of this article with the title “Instantiating uninterpreted functional units and memory system: functional
verification of the VAMP” appeared in [8]. The work reported here was done while all the authors were with Saarland University. 相似文献
38.
Nguyen-Huy Dung Pardo Marie-Paule Dogguy.Smiri Leïla 《Materials Research Bulletin》1982,17(3):293-300
The Mn0.23Ga1.85S3 phase belongs to the solid solution , stable at low temperature in the Ga2S3MnS system. It is hexagonal superstructure of the wurtzite, with the Ga2S3α′ type (; Z = 6; space groupe P61 or P65). Its crystal structure has been refined by the least squares method to a final R = 0.06 with 323 independant reflections. This structure is closely related to Ga2S3 α described by Hahn and Frank, and differs only by the partial occupation of the vacant metal site of Ga2S3 by Mn atoms in statistical disorder. 相似文献
39.
Many analyses of boxed microstrip discontinuities require the location of large numbers of high-order modes. Using Sturm-Liouville theory, this letter derives a relationship between microstrip modes and slab-loaded guide modes, leading to an efficient mode location algorithm for microstrip, including microstrip with finite strip thickness.<> 相似文献
40.
We study deterministic finite automata (DFA) with recursive calls, that is, finite sequences of component DFAs that can call each other recursively. DFAs with recursive calls are akin to recursive state machines and unrestricted hierarchic state machines. We show that they are language equivalent to deterministic pushdown automata (DPDA). 相似文献