全文获取类型
收费全文 | 3148篇 |
免费 | 53篇 |
专业分类
电工技术 | 13篇 |
化学工业 | 196篇 |
金属工艺 | 16篇 |
机械仪表 | 16篇 |
建筑科学 | 27篇 |
矿业工程 | 3篇 |
能源动力 | 32篇 |
轻工业 | 192篇 |
水利工程 | 6篇 |
石油天然气 | 5篇 |
无线电 | 42篇 |
一般工业技术 | 137篇 |
冶金工业 | 2367篇 |
原子能技术 | 2篇 |
自动化技术 | 147篇 |
出版年
2022年 | 14篇 |
2021年 | 24篇 |
2020年 | 19篇 |
2019年 | 24篇 |
2018年 | 36篇 |
2017年 | 25篇 |
2016年 | 37篇 |
2015年 | 17篇 |
2014年 | 39篇 |
2013年 | 53篇 |
2012年 | 47篇 |
2011年 | 57篇 |
2010年 | 40篇 |
2009年 | 45篇 |
2008年 | 30篇 |
2007年 | 48篇 |
2006年 | 33篇 |
2005年 | 27篇 |
2004年 | 17篇 |
2003年 | 19篇 |
2002年 | 34篇 |
2001年 | 20篇 |
2000年 | 13篇 |
1999年 | 93篇 |
1998年 | 774篇 |
1997年 | 465篇 |
1996年 | 283篇 |
1995年 | 141篇 |
1994年 | 120篇 |
1993年 | 136篇 |
1992年 | 28篇 |
1991年 | 24篇 |
1990年 | 21篇 |
1989年 | 30篇 |
1988年 | 34篇 |
1987年 | 17篇 |
1986年 | 18篇 |
1985年 | 13篇 |
1983年 | 4篇 |
1982年 | 10篇 |
1981年 | 8篇 |
1980年 | 16篇 |
1979年 | 3篇 |
1978年 | 4篇 |
1977年 | 63篇 |
1976年 | 152篇 |
1975年 | 6篇 |
1974年 | 3篇 |
1973年 | 3篇 |
1955年 | 3篇 |
排序方式: 共有3201条查询结果,搜索用时 15 毫秒
1.
CP Kubicek R Messner F Gruber M Mandels EM Kubicek-Pranz 《Canadian Metallurgical Quarterly》1993,268(26):19364-19368
We prepared [U-14C]cellobiose by cultivating Acetobacter pasteurianus in the presence of [U-14C]glucose and hydrolyzing the [U-14C]cellulose formed with beta-glucosidase-free cellulase from Trichoderma reesei. This 14C-labeled cellobiose was used to investigate the presence of an uptake system for cellobiose in T. reesei. Evidence was obtained for the presence of a high affinity (Km for cellobiose 0.3 microM) but low activity (2.5 milliunits/mg fungal dry weight) cellobiose permease. The permease is formed constitutively, but higher levels are formed after addition of sophorose (glucosyl-beta-1,2-diglucoside), a reputed cellulase inducer. The permease appears to be specific for beta-diglucosides, as the uptake of [U-14C]cellobiose is inhibited by sophorose, gentiobiose (glucosyl-beta-1,3-glucoside), and cellobiose. Under these conditions, cellooligodextrines (n, 4-7; final concentration, 1 mM) are not inhibitors. Glucose, but no other monosaccharides, inhibits the permease. The hypersecretory mutant T. reesei RUT C-30 exhibits elevated permease activities, whereas in T. reesei QM 9979, a mutant strain defective in the induction of cellulases by cellulose or sophorose, strongly reduced permease activities were demonstrated. The results stress a hitherto not recognized point of control in the induction of cellulases by T. reesei at the level of uptake of cellulose oligosaccharides. 相似文献
2.
HM Krumholz Y Wang EM Parent J Mockalis M Petrillo MJ Radford 《Canadian Metallurgical Quarterly》1997,157(19):2242-2247
3.
According to FDA regulations, a combination drug is not efficacious unless each component contributes to the claimed effects. For a univariate endpoint, this implies that the combination at specific doses must be superior to each of its components at the same doses. More demanding is the property of synergy, in which the effect of the combination must be superior to the effect expected based on those of its components. If it is equal to those effects, it is additive, and if it is inferior, it is antagonistic. We give regions in the combination dose plane where these concepts are well defined. If the effect of the combination is greater than the greatest effect achievable by any of its components it is therapeutically synergistic. A combination can be antagonistic, yet its components can still contribute to the claimed effects. If it is additive, synergistic or therapeutically synergistic, its components must contribute to the claimed effects. We relate these concepts and provide designs and sequential procedures for determining whether a combination is therapeutically synergistic, synergistic, additive, antagonistic and contributing or antagonistic and non-contributing. 相似文献
4.
EM Renz 《Canadian Metallurgical Quarterly》1997,50(7):225-227
The Dieulafoy lesion, also referred to as exulceratio simplex, caliber-persistent artery anomaly, or cirsoid aneurysm, is a relatively rare, yet possibly fatal cause of gastrointestinal bleeding. Recent journal articles suggest that this pathological entity is not as uncommon as once thought. Advances in endoscopic technique and esophagogastroduodenoscopy (EGD) have greatly assisted in earlier diagnosis and added options to the treatment regimen for this lesion. The relationship of this anomaly to possible exsanguination makes it essential that both medical and surgical endoscopists be knowledgeable of the anatomy, diagnosis, and management of this pathology. Several therapeutic approaches to Dieulafoy's lesion are available and are described. 相似文献
5.
A. E. Bohe J. J. Andrade Gamboa E. M. Lopasso D. M. Pasquevich 《Journal of Materials Science》1996,31(13):3469-3474
A chlorination process for recovering Zr from zircaloy scrap has been studied. Zircaloy chlorination was possible at temperatures as low as 220 °C. The scale microstructure and its effect on the zircaloy reactivity was analysed using Thermogravimetric analysis (TGA), X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDXS) and scanning electron microscopy (SEM) techniques. A solid-solid phase transformation took place into the oxide scale during the zircaloy chlorination. Zirconium, as ZrCl4(g), was separated from the oxide scale and chlorides of Cr and Fe. The effect of the reaction temperature was also analysed. 相似文献
6.
7.
We conducted a study to determine if the risk of airway compromise following tonsillectomy with uvulopalatopharyngoplasty justifies the added cost and inconvenience of step-down monitoring in an intensive care unit. We performed a retrospective chart review of 130 patients with obstructive sleep apnea who had undergone isolated tonsillectomy with uvulopalatopharyngoplasty at our tertiary care center. The average length of stay in the step-down unit was 18 hours. We found that only eight of these patients (6.2%) had a postoperative desaturation level of less than 90%, including three of 12 patients (25%) who had comorbid conditions. No patient had an adverse respiratory event. We conclude that step-down monitoring in an intensive care unit is not necessary, although caution should be exercised in monitoring patients with comorbidities because they appear to be more prone to desaturation. A complete lack of adverse respiratory events has not been reported in previous studies. 相似文献
8.
An efficient method for computing the fields of large scatterers is presented. The current is expanded in terms of modes defined as complex exponential functions. The modes are represented efficiently by means of spline functions. Analytical expressions have been obtained to compute efficiently the fields due to the current modes. 相似文献
9.
10.
A Van Aarem M Wagenaar AJ Pinckers PL Huygen EM Bleeker-Wagemakers BJ Kimberling CW Cremers 《Canadian Metallurgical Quarterly》1995,16(4):151-158
Thirty-seven patients, comprising 24 familial cases and 13 isolated patients with Usher syndrome type II (USH2), underwent ophthalmologic examination. Based on the degree of hearing loss, normal vestibular function, and gene-linkage analysis, familial cases were assumed to have USH2A. An analysis of genetic heterogeneity failed to reveal the presence of a second locus in the Dutch population. Although the patients appear to belong to a genetically homogeneous group, remarkable ophthalmologic variability was found. Corrected visual acuity decreased with age and remarkable differences in visual acuity were found within one family. Fundoscopic findings were classified as type A if attenuated vessels and bone corpuscles in all quadrants were found or as type B if findings other than these were found. The prevalence of type A significantly increased with age. 相似文献