全文获取类型
收费全文 | 5544篇 |
免费 | 123篇 |
国内免费 | 18篇 |
专业分类
电工技术 | 32篇 |
综合类 | 6篇 |
化学工业 | 767篇 |
金属工艺 | 105篇 |
机械仪表 | 74篇 |
建筑科学 | 88篇 |
矿业工程 | 6篇 |
能源动力 | 103篇 |
轻工业 | 146篇 |
水利工程 | 17篇 |
石油天然气 | 11篇 |
无线电 | 304篇 |
一般工业技术 | 700篇 |
冶金工业 | 2869篇 |
原子能技术 | 26篇 |
自动化技术 | 431篇 |
出版年
2023年 | 18篇 |
2022年 | 34篇 |
2021年 | 62篇 |
2020年 | 53篇 |
2019年 | 47篇 |
2018年 | 73篇 |
2017年 | 55篇 |
2016年 | 75篇 |
2015年 | 53篇 |
2014年 | 77篇 |
2013年 | 197篇 |
2012年 | 117篇 |
2011年 | 155篇 |
2010年 | 140篇 |
2009年 | 163篇 |
2008年 | 128篇 |
2007年 | 126篇 |
2006年 | 107篇 |
2005年 | 91篇 |
2004年 | 110篇 |
2003年 | 91篇 |
2002年 | 86篇 |
2001年 | 79篇 |
2000年 | 67篇 |
1999年 | 146篇 |
1998年 | 861篇 |
1997年 | 497篇 |
1996年 | 307篇 |
1995年 | 189篇 |
1994年 | 174篇 |
1993年 | 204篇 |
1992年 | 71篇 |
1991年 | 71篇 |
1990年 | 73篇 |
1989年 | 79篇 |
1988年 | 77篇 |
1987年 | 63篇 |
1986年 | 52篇 |
1985年 | 63篇 |
1984年 | 40篇 |
1983年 | 41篇 |
1982年 | 31篇 |
1981年 | 33篇 |
1980年 | 46篇 |
1978年 | 24篇 |
1977年 | 70篇 |
1976年 | 122篇 |
1975年 | 16篇 |
1974年 | 19篇 |
1973年 | 24篇 |
排序方式: 共有5685条查询结果,搜索用时 54 毫秒
71.
RP Allaker KA Young T Langlois R de Rosayro JM Hardie 《Canadian Metallurgical Quarterly》1997,14(4):127-130
Animal bite wounds are amongst the most common types of traumatic injuries in humans. The organisms isolated from these wounds generally reflect the oral flora of the biting animal, and may be fastidious in nature and difficult to identify. This study was undertaken to determine the prevalence of Eikenella corrodens, Actinobacillus actinomycetemcomitans, Porphyromonas and Prevotella spp. in supragingival dental plaque collected from the right maxillary canine and carnassial teeth and the right mandibular canine tooth of dogs. In part one of the study, 30 dogs were used. E. corrodens was found in 62% of these dogs and 44% of individual plaque samples. A. actinomycetemcomitans was not detected in any of the dogs sampled. In part two, 34 dogs were used to determine the prevalence of the black pigmented anaerobic bacilli (Porphyromonas and Prevotella spp.). Porphyromonas gingivalis was present in 68% of these dogs and 47% of individual plaque samples. Prevotella intermedia was present in 44% of the dogs and 23% of individual plaque samples. The recently described Porphyromonas canoris, Porphyromonas salivosa, Porphyromonas cangingivalis, Porphyromonas cansulci, Porphyromonas crevioricanis and Prevotella denticola species were isolated from only 9%, 6%, 3%, 3%, 3% and 3% of dogs respectively. Porphyromonas gingivicanis was not isolated from any of the animals sampled. In conclusion, black-pigmented anaerobic bacilli were isolated from 91% of the animals sampled and therefore constitute a significant risk with respect to bite wound infections. It is also suggested that the prevalence of E. corrodens in wound infections has been underestimated in previous reports because of use of inappropriate techniques for detecting this organism. 相似文献
72.
W. Harmon Ray 《加拿大化工杂志》1991,69(3):626-629
A brief review of addition polymerization processes is presented with a summary of the key characteristics classified by kinetic mechanism (free-radical, anionic, cationic, group transfer, or Ziegler–Natta), phase behavior, and reactor type. A practical approach to modelling in the industrial R & D environment is discussed in terms of a CAD package for polymerization processes. 相似文献
73.
DM Clark PM Salkovskis LG Ost E Breitholtz KA Koehler BE Westling A Jeavons M Gelder 《Canadian Metallurgical Quarterly》1997,65(2):203-213
Cognitive accounts of panic predict that panic disorder patients will be particularly prone to misinterpret autonomic sensations. Several studies have produced results consistent with this prediction, but each is open to alternative interpretation. To clarify matters, 2 studies administered the Body Sensations Interpretation Questionnaire (BSIQ) to panic patients and controls. Panic patients were more likely to interpret ambiguous autonomic sensations as signs of immediately impending physical or mental disaster and were more likely than other anxiety disorder patients and nonpatients to believe these interpretations. In a 3rd study, a brief version of the BSIQ was shown to have satisfactory test-retest reliability, to change with treatment, and to discriminate treatments that varied in their effects on panic. 相似文献
74.
Eleven Spectralon1 (a sintered polytetrafluoroethylene-based material) and 16 BaSO4 reference reflectance panels were calibrated using a field calibration technique. The Spectralon panels differed both in their directional/hemispherical and directional/directional reflectance. However, the differences were sufficiently small that “general” calibration equations were developed. For panels constructed of the same material and with the same methods as those used in these experiments, the directional/directional reflectance may be within ± 0.020 at 10°, ± 0.015 at 45°, and ± 0.041 at 80° of that predicted by the “general” equations. For field measurements, these values are considerably better than those that would be obtained using a value of the directional/hemispherical reflectance. The directional/directional reflectance of the 16 BaSO4 panels varied considerably among panels, so much so that it was not feasible to develop “general” calibration equations. Apparently, the nonlambertian properties of BaSO4 panels are dependent upon the method of applying the barium sulfate coating. 相似文献
75.
76.
77.
RE Droleskey PJ Holman KA Waldrup DE Corrier GG Wagner 《Canadian Metallurgical Quarterly》1993,79(3):424-434
Babesia odocoilei continuously cultured in white-tailed deer (Odocoileus virginianus) erythrocytes was examined by transmission and scanning electron microscopy. Merozoites, trophozoites, intermediate-stage forms, and dividing forms were observed. Merozoites possessed a single nucleus, inner membrane complex, rhoptries, free ribosomes, rough endoplasmic reticulum, and single membrane-bound vesicles. Trophozoites lacked an inner membrane complex and rhoptries. Intermediate stages were characterized by distinct segments of inner membrane complex. Dividing forms ranged from cells with an elongated nucleus to mature daughter cells joined by a ringlike structure. Babesia odocoilei was characterized by its close proximity to the erythrocyte membrane, membranous structures resembling feeding organelles, and reproduction via a method resembling budding sensu stricto. 相似文献
78.
TM H?ltt? KA R?nnholm H Jalanko M Ala-Houhala M Antikainen C Holmberg 《Canadian Metallurgical Quarterly》1997,17(6):573-580
The aim of this study was to examine the effect of intensive practice in table tennis on perceptual coincident timing. The main question was whether the perceptual demands encountered in fast ball sports produce modifications of the perceptual visual system. Expert table tennis players and novices were compared in a perceptual task which consisted of estimating, by pressing a key, the arrival of a moving stimulus at a target. The stimulus, which was presented either at constant velocity or at constant deceleration, reproduced as closely as possible the natural visual demands encountered in table tennis. The difference between the time of response and the time of arrival of the stimulus at a target position was measured over 40 trials for each of the 16 participants. The results showed no effect of expertise under the constant-velocity condition but an effect under the decelerative condition, indicating that experts were less trajectory-dependent than novices. This result was interpreted as reflecting a better adaptation of the perceptual system of experts to the constraints encountered during table tennis and specifically to the perceptual demands resulting from varied and decelerated ball trajectories. Finally, some limitations of the coincidence anticipation procedure are highlighted, concerning its use in practical settings for evaluating athletes or detecting sport talents, and the need for the simulation conditions during testing to reproduce as closely as possible the perceptual demands of real life is discussed. 相似文献
79.
Wide band gap a-SiOx:H films have been prepared by the photochemical decomposition of a SiH4, CO2 and H2 gas mixture. Deposition parameters namely the CO2 to SiH4 gas flow ratio, H2 dilution and chamber pressure were optimized in order to achieve highly photoconducting (1 × 10-6 S cm-1) films with an optical gap of 1.99 eV. The optical gap was found to increase with an increase in the CO2 to SiH4 flow ratio. A decrease in the photoconductivity, refractive index, spin g-value and a simultaneous increase in the spin density are attributed to an incorporation of oxygen into the films. Upon hydrogen
dilution the photoconductivity of a-SiOx:H films was observed to improve along with an increase of the optical gap. The spin density of a-SiOx:H films was of the order of 1017 cm-9. The optoelectronic properties of the films have been correlated with the bonding configurations in the film, deposition
parameters and the growth kinetics.
This revised version was published online in November 2006 with corrections to the Cover Date. 相似文献
80.
WG Wolfe AL Vaughn HF Seigler JW Hathorn KA Leopold FG Duhaylongsod 《Canadian Metallurgical Quarterly》1993,105(4):749-55; discussion 755-6
Since 1985, 229 cases of carcinoma of the esophagus have been considered for entry into a protocol with the use of preoperative chemotherapy and radiation therapy followed by surgical intervention as the primary element of treatment. One hundred sixty-five patients (93 with adenocarcinoma and 72 with squamous cell carcinoma) had esophagogastrectomy. The 5-year survival of the protocol patients who underwent resection was 25% for both groups--squamous cell carcinoma and adenocarcinoma. Of the protocol patients with squamous cell carcinoma who underwent resection, 40% had a sterilized specimen, whereas of those with adenocarcinoma, 20% had a sterilized specimen. If the patient had a sterilized specimen, the 5-year survival was approximately 60% for adenocarcinoma and 40% for squamous cell carcinoma. Those patients with adenocarcinoma and Barrett's esophagus had a 5-year survival of 55%. Of the patients who underwent only esophagectomy and esophagogastrectomy and had not been entered into the protocol, none lived beyond 3 years. The operative mortality rate for those who had esophagogastrectomy was 5%. Sixty-four patients completed the radiation therapy and chemotherapy but did not undergo surgical procedures because of progressive disease or refusal. Of those patients who completed chemotherapy and radiation therapy without surgical intervention, 5-year survival was 18% in patients with squamous cell carcinoma, whereas no patients with adenocarcinoma survived beyond 3 years. The finding of a sterilized specimen after esophagectomy is a favorable prognostic factor in patients with adenocarcinoma or squamous cell carcinoma. The finding that patients with Barrett's esophagus and adenocarcinoma have an improved chance for survival is perhaps related to an earlier diagnosis. It is clear that some patients with squamous cell carcinoma who did not undergo surgical procedures did have a sterilized specimen, because the survival in this group approached 20% at 5 years. 相似文献