全文获取类型
收费全文 | 6989篇 |
免费 | 292篇 |
国内免费 | 8篇 |
专业分类
电工技术 | 79篇 |
化学工业 | 1091篇 |
金属工艺 | 109篇 |
机械仪表 | 132篇 |
建筑科学 | 212篇 |
矿业工程 | 11篇 |
能源动力 | 179篇 |
轻工业 | 543篇 |
水利工程 | 50篇 |
石油天然气 | 10篇 |
无线电 | 647篇 |
一般工业技术 | 1205篇 |
冶金工业 | 1966篇 |
原子能技术 | 64篇 |
自动化技术 | 991篇 |
出版年
2023年 | 43篇 |
2022年 | 73篇 |
2021年 | 111篇 |
2020年 | 83篇 |
2019年 | 125篇 |
2018年 | 141篇 |
2017年 | 125篇 |
2016年 | 124篇 |
2015年 | 111篇 |
2014年 | 179篇 |
2013年 | 343篇 |
2012年 | 229篇 |
2011年 | 329篇 |
2010年 | 245篇 |
2009年 | 237篇 |
2008年 | 279篇 |
2007年 | 271篇 |
2006年 | 205篇 |
2005年 | 176篇 |
2004年 | 155篇 |
2003年 | 157篇 |
2002年 | 146篇 |
2001年 | 116篇 |
2000年 | 119篇 |
1999年 | 141篇 |
1998年 | 484篇 |
1997年 | 292篇 |
1996年 | 214篇 |
1995年 | 160篇 |
1994年 | 152篇 |
1993年 | 149篇 |
1992年 | 82篇 |
1991年 | 72篇 |
1990年 | 77篇 |
1989年 | 87篇 |
1988年 | 78篇 |
1987年 | 70篇 |
1986年 | 50篇 |
1985年 | 58篇 |
1984年 | 86篇 |
1983年 | 70篇 |
1982年 | 60篇 |
1981年 | 59篇 |
1980年 | 62篇 |
1979年 | 72篇 |
1978年 | 55篇 |
1977年 | 75篇 |
1976年 | 125篇 |
1975年 | 49篇 |
1974年 | 43篇 |
排序方式: 共有7289条查询结果,搜索用时 118 毫秒
31.
N. E. Shchepina V. V. Avrorin G. A. Badun V. M. Fedoseev S. E. Ukhanov S. B. Lewis 《Radiochemistry》2007,49(6):630-632
Ion-molecule reactions of free phenyl cations with six-membered nitrogen-containing heterocyclic compounds: α-, β-, and γ-picolines, were studied. Phenyl cations were generated by tritium β-decay in double-labeled benzene. The mechanism of competing reactions of electrophilic addition to the nitrogen heteroatom in the ring and electrophilic substitution of the C-H bond in the pyridine ring was examined. The effect of methyl substituent in the pyridine molecule on the reaction pathway was evaluated. A one-step procedure for nuclear-chemical synthesis of tritium-labeled N-phenylpicolinium salts and phenyl-substituted picolines was developed. 相似文献
32.
Ramirez Juan R.; Crano William D.; Quist Ryan; Burgoon Michael; Alvaro Eusebio M.; Grandpre Joseph 《Canadian Metallurgical Quarterly》2004,18(1):3
The authors investigated relationships between marijuana and inhalant use and several cultural and demographic factors in Anglo American and Hispanic American adolescents (N=1,094). Outcome measures assessed lifetime and 30-day marijuana and inhalant use. Predictors and covariates used in logistic regression analyses were region, grade, gender, knowledge, acculturation, familism, and parental monitoring. Hispanic Americans exhibited higher usage across all measures. In this group, high acculturation was associated with low marijuana, but high inhalant, use. Across all participants, positive family relations and parental monitoring were strongly associated with attenuated marijuana use hut only among those most knowledgeable about drugs. Familism and monitoring were not associated with diminished usage among the less knowledgeable. For inhalants, monitoring combined with high knowledge or high familism was associated with diminished usage. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
33.
34.
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
35.
R Lewis 《Canadian Metallurgical Quarterly》1998,24(3):95-97
The management of pain in patients with burn wounds is complex and problematic. Burn-wound pain is severe, inconsistent and underestimated. Patients experience severe pain, especially during procedures, until wound healing has occurred. A multi-modality approach is needed for effective management of pain, which requires an understanding of the mechanisms of pain. Altered pharmacokinetics and pharmacodynamics in burn-wound patients makes drug actions unpredictable. Opioids alone are seldom sufficient for pain control. The multi-modality approach includes the use of opioids and non-steroidal anti-inflammatory, anxiolytic and alternative drugs. Ketamine has been found to be a useful agent for analgesia in burn-wound patients; a dose of 10 mg/kg qid per os was found to be an effective adjunct to pain therapy. 相似文献
36.
J. W. Huang J. M. Ryan K. L. Bray T. F. Kuech 《Journal of Electronic Materials》1995,24(11):1539-1546
The defect engineering in metalorganic vapor phase epitaxy InxGa1-xAs and InP by controlled oxygen doping using diethyl aluminum ethoxide (DEALO) was developed in this study. DEALO doping has
led to the incorporation of Al and O, and the compensation of shallow Si donors in InxGa1−xAs: Si with 0 ≤ x ≤ 0.25. With the same DEALO mole fraction during growth, the incorporation of Al and O was found to be independent
of x, but the compensation of Si donors decreases with increasing In content. Deep level transient spectroscopy analysis on
a series of InxGa1-xAs: Si. samples with 0 ≤ x ≤ 0.18 revealed that oxygen incorporation led to a set of deep levels, similar to those found in
DEALO doped GaAs. As the In composition was increased, one or more of these deep levels became resonant with the conduction
band and led to a high electron concentration in oxygen doped In0.53Ga0.47As. Low temperature photoluminescence emission measurements at 12K on the same set of samples revealed the quenching of the
near-band edge peak, and the appearance of new oxygen-induced emission features. DEALO doping in InP has also led to the incorporation
of Al and O, and the compensation of Si donors due to oxygen-induced multiple deep levels. 相似文献
37.
Network management in large heterogeneous communication environments requires the incorporation of more advanced tools than are currently available, especially in the area of fault management. By providing an informational infrastructure for documenting network behavior and maintenance activities, TTSs (trouble ticket systems) have provided some relief for the fault management problem. Researchers have recognized TTSs as a means for realizing more advanced functions in network management platforms to effect automatic trouble ticket generation, fault diagnostics, and the correlation of multiple views network problems and behavior. The authors describe current research trends towards understanding and implementing these advanced functions in a TTS framework 相似文献
38.
Kovacs G.T.A. Storment C.W. Halks-Miller M. Belczynski C.R. Jr. Santina C.C.D. Lewis E.R. Maluf N.I. 《IEEE transactions on bio-medical engineering》1994,41(6):567-577
A new process for the fabrication of regeneration microelectrode arrays for peripheral and cranial nerve applications is presented. This type of array is implanted between the severed ends of nerves, the axons of which regenerate through via holes in the silicon and are thereafter held fixed with respect to the microelectrodes. The process described is designed for compatibility with industry-standard CMOS or BiCMOS processes (it does not involve high-temperature process steps nor heavily-doped etch-stop layers), and provides a thin membrane for the via holes, surrounded by a thick silicon supporting rim. Many basic questions remain regarding the optimum via hole and microelectrode geometries in terms of both biological and electrical performance of the implants, and therefore passive versions were fabricated as tools for addressing these issues in on-going work. Versions of the devices were implanted in the rat peroneal nerve and in the frog auditory nerve. In both cases, regeneration was verified histologically and it was observed that the regenerated nerves had reorganized into microfascicles containing both myelinated and unmyelinated axons and corresponding to the grid pattern of the via holes. These microelectrode arrays were shown to allow the recording of action potential signals in both the peripheral and cranial nerve settings, from several microelectrodes in parallel 相似文献
39.
40.
This paper describes a fifth-order, low-pass switched capacitor filter for video applications. It has a 4-MHz cutoff frequency and uses a parallel biquadratic structure with double sampling to achieve an 80-MHz input sampling rate in a 2-μm CMOS process. The prototype filter is fully differential, occupies an active area of 11 mm2 , and dissipates 190 mW 相似文献