全文获取类型
收费全文 | 3812篇 |
免费 | 89篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 35篇 |
综合类 | 2篇 |
化学工业 | 567篇 |
金属工艺 | 53篇 |
机械仪表 | 72篇 |
建筑科学 | 222篇 |
矿业工程 | 9篇 |
能源动力 | 63篇 |
轻工业 | 297篇 |
水利工程 | 48篇 |
石油天然气 | 17篇 |
武器工业 | 1篇 |
无线电 | 302篇 |
一般工业技术 | 633篇 |
冶金工业 | 1048篇 |
原子能技术 | 39篇 |
自动化技术 | 495篇 |
出版年
2021年 | 49篇 |
2020年 | 35篇 |
2019年 | 42篇 |
2018年 | 46篇 |
2017年 | 46篇 |
2016年 | 61篇 |
2015年 | 51篇 |
2014年 | 80篇 |
2013年 | 208篇 |
2012年 | 152篇 |
2011年 | 176篇 |
2010年 | 139篇 |
2009年 | 140篇 |
2008年 | 183篇 |
2007年 | 145篇 |
2006年 | 121篇 |
2005年 | 119篇 |
2004年 | 90篇 |
2003年 | 86篇 |
2002年 | 80篇 |
2001年 | 70篇 |
2000年 | 72篇 |
1999年 | 71篇 |
1998年 | 220篇 |
1997年 | 159篇 |
1996年 | 111篇 |
1995年 | 76篇 |
1994年 | 70篇 |
1993年 | 82篇 |
1992年 | 40篇 |
1991年 | 32篇 |
1990年 | 38篇 |
1989年 | 48篇 |
1988年 | 55篇 |
1987年 | 31篇 |
1986年 | 35篇 |
1985年 | 45篇 |
1984年 | 60篇 |
1983年 | 37篇 |
1982年 | 40篇 |
1981年 | 49篇 |
1980年 | 42篇 |
1979年 | 30篇 |
1978年 | 33篇 |
1977年 | 46篇 |
1976年 | 67篇 |
1975年 | 33篇 |
1974年 | 25篇 |
1973年 | 28篇 |
1972年 | 18篇 |
排序方式: 共有3903条查询结果,搜索用时 15 毫秒
11.
Fe–Co bimetallic metals supported on CaCO3 support have been prepared using three different methods for the preparation of the catalysts; wet impregnation (IMP), deposition–precipitation (DP) and reverse micelle impregnation (RM). By careful choice and optimization of CVD reaction conditions and catalyst preparation procedures, we have tailored the nanofabrication of CNTs using 5 wt.% Fe–Co/CaCO3. High yields of ‘clean’ MWNTs with near 100% selectivity and excellent reproducibility were obtained (1215% and 835% yields for the IMP and DP methods respectively). The RM technique enabled more precise control over the size of the CNTs and a narrower diameter distribution (3–5 nm i.d. and 10–15 nm o.d.) was obtained. 相似文献
12.
13.
14.
Joos F. Miguel Snaddon Robert W. L. Johnson Neil A. 《Industry Applications, IEEE Transactions on》1985,(6):1366-1372
Droplet growth is examined in a water-in-oil type emulsion where the droplets are subjected exclusively to viscous and dielectrophoretic forces. The latter are produced by the interaction of the droplets with an otherwise uniformly imposed electric field. Theoretical considerations are presented as a basis for understanding and interpreting the experiments. An emulsion consisting of deionized water droplets in a silicone oil of specific gravity I is subjected to a uniform 60 Hz, ac electrostatic field. Initially, the droplets are fairly monodisperse with mean diameters of approximately 25 , sm. The changes in droplet size distributions with time are examined with a laser diffraction system for water volume fractions ranging from 0.001 to 0.1 and applied fields ranging from 52 to 520 kVm-1. The average droplet size increases exponentially with time; we examine the exponent's dependence on average field strength and droplet volume fraction. 相似文献
15.
IH Robertson JB Mattingley C Rorden J Driver 《Canadian Metallurgical Quarterly》1998,395(6698):169-172
Patients with extensive damage to the right hemisphere of their brain often exhibit unilateral neglect of the left side of space. The spatial attention of these patients is strongly biased towards the right, so their awareness of visual events on the left is impaired. Extensive right-hemisphere lesions also impair tonic alertness (the ability to maintain arousal). This nonspatial deficit in alertness is often considered to be a different problem from spatial neglect, but the two impairments may be linked. If so, then phasically increasing the patients' alertness should temporarily ameliorate their spatial bias in awareness. Here we provide evidence to support this theory. Right-hemisphere-neglect patients judged whether a visual event on the left preceded or followed a comparable event on the right. They became aware of left events half a second later than right events on average. This spatial imbalance in the time course of visual awareness was corrected when a warning sound alerted the patients phasically. Even a warning sound on the right accelerated the perception of left visual events in this way. Nonspatial phasic alerting can thus overcome disabling spatial biases in perceptual awareness after brain injury. 相似文献
16.
B Tomkinson E Robertson R Yalamanchili R Longnecker E Kieff 《Canadian Metallurgical Quarterly》1993,67(12):7298-7306
Five overlapping type 1 Epstein-Barr virus (EBV) DNA fragments constituting a complete replication- and transformation-competent genome were cloned into cosmids and transfected together into P3HR-1 cells, along with a plasmid encoding the Z immediate-early activator of EBV replication. P3HR-1 cells harbor a type 2 EBV which is unable to transform primary B lymphocytes because of a deletion of DNA encoding EBNA LP and EBNA 2, but the P3HR-1 EBV can provide replication functions in trans and can recombine with the transfected cosmids. EBV recombinants which have the type 1 EBNA LP and 2 genes from the transfected EcoRI-A cosmid DNA were selectively and clonally recovered by exploiting the unique ability of the recombinants to transform primary B lymphocytes into lymphoblastoid cell lines. PCR and immunoblot analyses for seven distinguishing markers of the type 1 transfected DNAs identified cell lines infected with EBV recombinants which had incorporated EBV DNA fragments beyond the transformation marker-rescuing EcoRI-A fragment. Approximately 10% of the transforming virus recombinants had markers mapping at 7, 46 to 52, 93 to 100, 108 to 110, 122, and 152 kbp from the 172-kbp transfected genome. These recombinants probably result from recombination among the transfected cosmid-cloned EBV DNA fragments. The one recombinant virus examined in detail by Southern blot analysis has all the polymorphisms characteristic of the transfected type 1 cosmid DNA and none characteristic of the type 2 P3HR-1 EBV DNA. This recombinant was wild type in primary B-lymphocyte infection, growth transformation, and lytic replication. Overall, the type 1 EBNA 3A gene was incorporated into 26% of the transformation marker-rescued recombinants, a frequency which was considerably higher than that observed in previous experiments with two-cosmid EBV DNA cotransfections into P3HR-1 cells (B. Tomkinson and E. Kieff, J. Virol. 66:780-789, 1992). Of the recombinants which had incorporated the marker-rescuing cosmid DNA fragment and the fragment encoding the type 1 EBNA 3A gene, most had incorporated markers from at least two other transfected cosmid DNA fragments, indicating a propensity for multiple homologous recombinations. The frequency of incorporation of the nonselected transfected type 1 EBNA 3C gene, which is near the end of two of the transfected cosmids, was 26% overall, versus 3% in previous experiments using transfections with two EBV DNA cosmids. In contrast, the frequency of incorporation of a 12-kb EBV DNA deletion which was near the end of two of the transfected cosmids was only 13%.(ABSTRACT TRUNCATED AT 400 WORDS) 相似文献
17.
Neil Kirkpatrick 《Packaging Technology and Science》1993,6(3):159-172
Solid-waste management, and in particular the disposal of used packaging, is currently the subject of much topical debate. This is driven by both consumer and legislative pressures. Consumers see used packaging as a highly visible element of municipal solid waste, complaining of excessive packaging and low levels of recycling. Legislators, perhaps in pandering to the views expressed by consumer bodies, have been active within the CEC and individual Member States by introducing (or proposing) legislation or similar regulatory tools and targets to facilitate a greater diversion of used packaging from disposal by landfill to alternative solid-waste management practices, in particular recycling, which are widely accepted to have a lower impact on the environment. In this paper the relative environmental profiles of pursuing alternative solid-waste management practices to disposal by landfill are explored, focusing not just on solid waste per se but also on associated considerations of energy consumption and emissions, which are invariably overlooked as factors contributing to the environmental impact of solid-waste management practices. 相似文献
18.
Graham A. Jullien Wenzhe Luo Neil M. Wigley 《The Journal of VLSI Signal Processing》1996,14(2):207-220
This paper discusses strategies for implementing DSP systems using residue replication. The theory, recently introduced by two of the authors, uses formal polynomial ring mappings, from binary representations, to direct product ring implementation of integer processing arrays. The mapping produces completely independent computational arrays each computing over the same ring. This paper describes an architecture and processing array to implement, and take advantage of, the special computational ring structures that result from the mapping. A brief review of the theory and mapping techniques, is followed by the discussion of the architecture and VLSI design of an efficient inner product processing array using Fermat Primes. 相似文献
19.
20.