全文获取类型
收费全文 | 11394篇 |
免费 | 649篇 |
国内免费 | 305篇 |
专业分类
电工技术 | 384篇 |
综合类 | 380篇 |
化学工业 | 1622篇 |
金属工艺 | 434篇 |
机械仪表 | 423篇 |
建筑科学 | 607篇 |
矿业工程 | 155篇 |
能源动力 | 305篇 |
轻工业 | 547篇 |
水利工程 | 115篇 |
石油天然气 | 287篇 |
武器工业 | 34篇 |
无线电 | 1488篇 |
一般工业技术 | 1316篇 |
冶金工业 | 2976篇 |
原子能技术 | 79篇 |
自动化技术 | 1196篇 |
出版年
2024年 | 19篇 |
2023年 | 113篇 |
2022年 | 194篇 |
2021年 | 314篇 |
2020年 | 189篇 |
2019年 | 191篇 |
2018年 | 254篇 |
2017年 | 253篇 |
2016年 | 261篇 |
2015年 | 254篇 |
2014年 | 390篇 |
2013年 | 554篇 |
2012年 | 499篇 |
2011年 | 619篇 |
2010年 | 552篇 |
2009年 | 517篇 |
2008年 | 572篇 |
2007年 | 458篇 |
2006年 | 468篇 |
2005年 | 339篇 |
2004年 | 297篇 |
2003年 | 303篇 |
2002年 | 272篇 |
2001年 | 229篇 |
2000年 | 216篇 |
1999年 | 301篇 |
1998年 | 1018篇 |
1997年 | 612篇 |
1996年 | 497篇 |
1995年 | 313篇 |
1994年 | 252篇 |
1993年 | 235篇 |
1992年 | 81篇 |
1991年 | 74篇 |
1990年 | 66篇 |
1989年 | 68篇 |
1988年 | 64篇 |
1987年 | 48篇 |
1986年 | 52篇 |
1985年 | 35篇 |
1983年 | 15篇 |
1982年 | 9篇 |
1981年 | 20篇 |
1980年 | 29篇 |
1979年 | 16篇 |
1978年 | 14篇 |
1977年 | 44篇 |
1976年 | 112篇 |
1975年 | 13篇 |
1974年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
71.
Yen-Jen Chang Shanq-Jang Ruan Feipei Lai 《Very Large Scale Integration (VLSI) Systems, IEEE Transactions on》2003,11(4):568-580
Power consumption is an increasingly pressing problem in modern processor design. Since the on-chip caches usually consume a significant amount of power, it is one of the most attractive targets for power reduction. This paper presents a two-level filter scheme, which consists of the L1 and L2 filters, to reduce the power consumption of the on-chip cache. The main idea of the proposed scheme is motivated by the substantial unnecessary activities in conventional cache architecture. We use a single block buffer as the L1 filter to eliminate the unnecessary cache accesses. In the L2 filter, we then propose a new sentry-tag architecture to further filter out the unnecessary way activities in case of the L1 filter miss. We use SimpleScalar to simulate the SPEC2000 benchmarks and perform the HSPICE simulations to evaluate the proposed architecture. Experimental results show that the two-level filter scheme can effectively reduce the cache power consumption by eliminating most unnecessary cache activities, while the compromise of system performance is negligible. Compared to a conventional instruction cache (32 kB, two-way) implemented with only the L1 filter, the use of a two-level filter can result in roughly 30% reduction in total cache power consumption. Similarly, compared to a conventional data cache (32 kB, four-way) implemented with only the L1 filter, the total cache power reduction is approximately 46%. 相似文献
72.
Concentrations of 11 trace elements were determined in 56 control and 98 Alzheimer's disease (AD) olfactory bulb, olfactory tract, olfactory trigone, piriform cortex and amygdala specimens by instrumental neutron activation analysis. Iron and zinc were significantly elevated and bromine was significantly depleted in olfactory regions of AD patients, compared with normal age-matched control subjects. Elevated iron could possibly play a role in neuronal degeneration in AD by enhancing reactive free radical formation. 相似文献
73.
74.
MJ Kania SD Keeling SP McGorray TT Wheeler GJ King 《Canadian Metallurgical Quarterly》1996,66(6):423-432
This study examined risk factors associated with incisor injury in 3396 third and fourth grade school children in Alachua County, Florida. One of six orthodontists completed a standardized examination form for each child to assess severity of incisor injury, gender, age, race, skeletal relationships, morphologic malocclusion, incisor exposure, interlabial gap, TMJ sounds, chin trauma, and history of lower facial trauma. One in five (19.2%) exhibited some degree of incisor injury. This was limited to a single tooth in 73.1% of those with injury, while enamel injury predominated (89.4%). The majority of the injuries (75.4%) were localized in the maxillary arch, with central incisors the most frequently traumatized. Chi-square tests of association indicated that gender, race, school, orthodontist, history of lower facial trauma, chin trauma, profile, and maxillary and mandibular horizontal positions were associated with incisor injury (P < 0.05). Wilcoxon rank sum tests identified differences in age, overjet, time of screening, and interlabial gap between those with and without injury (P < 0.05). Results of logistic regression analyses indicated risk of incisor injury was greater for children who had a prognathic maxilla, a history of trauma, were older, were male, and had greater overjet and mandibular anterior spacing. 相似文献
75.
Nener B.D. Lai S.T. Faraone L. Nassibian A.G. 《IEEE transactions on instrumentation and measurement》1993,42(5):913-919
A method of directly evaluating the activation energy ΔE, capture cross section σ, and density NT, of deep-level traps from the pulsed reverse bias capacitance transient is described. The main advantages of this technique are that it requires only a single temperature scan, and it can resolve nonexponential transients due to closely-spaced energy levels. The test samples used for this paper consisted of Schottky diodes fabricated on nonirradiated and 1-MeV electron-irradiated n-type VPE (vapor-phase epitaxy) GaAs wafers. The well known EL2 trap was identified with ΔE of 0.81 eV, and σ n of 1.0×10-13 cm2 for the nonirradiated sample. These values were found to be in good agreement with published data using established, conventional DLTS techniques. For the irradiated samples a nonexponential capacitance transient was found in the EL2 range of temperatures. The discussed technique was able to resolve two closely spaced deep levels lying at Ec-0.81 eV and Ec-0.84 eV, and with capture cross sections of 1.5×10-13 cm2 and 2.5×10-12 cm2, respectively 相似文献
76.
J Randerson L Cawkwell A Jack JA Child F Lewis N Hall P Johnson P Evans S Barrans GJ Morgan 《Canadian Metallurgical Quarterly》1996,93(1):160-162
Fluorescent polymerase chain reaction (PCR) was used to assay 12 microsatellite markers (APC x 2, DCC, P53 x 2, RB1, NM23, WT1, D6S260, D6S262, D6S281 and TNFa) to look for evidence of microsatellite instability in 40 cases of follicle centre cell lymphoma (FCC). Evidence of novel alleles seen in the tumour tissue but not the normal uninvolved tissue was seen in seven cases (17%). In only two of these cases (5%) was more than one locus involved but in these cases multiple affected loci were seen (4/12 and 7/12 respectively). The detection of microsatellite instability indicates a DNA repair defect such as that which would be predicted to occur in cells with mutated mismatch repair genes, a novel finding in FCC lymphoma. 相似文献
77.
78.
1. alpha-toxin of Staphylococcus aureus readily permeabilized rat uterine smooth muscle after incubation for a short time. 2. The permeabilized muscle responded to Ca2+ dose-dependently and repeatedly in the same manner. 3. The threshold concentration of Ca2+ for contraction was 0.1-0.3 microM and the maximal contraction was achieved with 1 or 3 microM Ca2+. 4. GTP gamma S or GTP augmented the contractile response to Ca2+. 5. GDP beta S or GDP suppressed the contraction. 6. The role of GTP-binding protein in sensitization of Ca(2+)-induced contractile response of smooth muscle is discussed. 相似文献
79.
80.