全文获取类型
收费全文 | 243747篇 |
免费 | 2949篇 |
国内免费 | 1243篇 |
专业分类
电工技术 | 4831篇 |
综合类 | 264篇 |
化学工业 | 35478篇 |
金属工艺 | 10866篇 |
机械仪表 | 7079篇 |
建筑科学 | 6240篇 |
矿业工程 | 481篇 |
能源动力 | 6273篇 |
轻工业 | 24163篇 |
水利工程 | 1836篇 |
石油天然气 | 1337篇 |
武器工业 | 3篇 |
无线电 | 31052篇 |
一般工业技术 | 44922篇 |
冶金工业 | 50184篇 |
原子能技术 | 3860篇 |
自动化技术 | 19070篇 |
出版年
2021年 | 1573篇 |
2019年 | 1425篇 |
2018年 | 2328篇 |
2017年 | 2225篇 |
2016年 | 2447篇 |
2015年 | 1907篇 |
2014年 | 3163篇 |
2013年 | 10802篇 |
2012年 | 5458篇 |
2011年 | 7793篇 |
2010年 | 6288篇 |
2009年 | 6966篇 |
2008年 | 7563篇 |
2007年 | 7665篇 |
2006年 | 7036篇 |
2005年 | 6523篇 |
2004年 | 6247篇 |
2003年 | 6268篇 |
2002年 | 6244篇 |
2001年 | 6377篇 |
2000年 | 5803篇 |
1999年 | 6424篇 |
1998年 | 16578篇 |
1997年 | 11610篇 |
1996年 | 8958篇 |
1995年 | 6700篇 |
1994年 | 5908篇 |
1993年 | 5737篇 |
1992年 | 4053篇 |
1991年 | 3996篇 |
1990年 | 3589篇 |
1989年 | 3506篇 |
1988年 | 3448篇 |
1987年 | 2907篇 |
1986年 | 2845篇 |
1985年 | 3415篇 |
1984年 | 3053篇 |
1983年 | 2748篇 |
1982年 | 2554篇 |
1981年 | 2573篇 |
1980年 | 2437篇 |
1979年 | 2273篇 |
1978年 | 2241篇 |
1977年 | 2817篇 |
1976年 | 4175篇 |
1975年 | 1902篇 |
1974年 | 1799篇 |
1973年 | 1784篇 |
1972年 | 1462篇 |
1971年 | 1320篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
After recording transiently evoked otoacoustic emissions (TEOAEs) to a click stimulus in guinea pigs by using the IL088 which was developed by Bray and Kemp (1987) for easy recording and analysis of TEOAE, the changes after intravenous administration of furosemide (30 mg/kg or 50 mg/kg) were examined. The wave of the TEOAE could be detected from 20 of 24 ears (83%). After the i.v. injection of furosemide (30 mg/kg), TEOAE powers (total echo power and highest peak power in FFT pictures) decreased quickly and showed minimum values after 5-10 min. Then they increased rapidly and recovered normally within 60 min after injection. However, no ears showed TEOAEs during the 5- to 10-min period following the injection of the 50-mg/kg dose of furosemide. They then recovered slowly as compared with the group treated with the lower dose of furosemide (30 mg/kg). These changes are similar to those of the endocochlear potential (EP) after furosemide injection. These data support the notion that the EP can contribute to the mechanism of TEOAE generation. 相似文献
993.
A. Silaban D. P. Harrison M. H. Berggren M. C. Jha 《Chemical Engineering Communications》1991,107(1):55-71
Cylindrical pellets of zinc ferrite high temperature desulfurization sorbent have been prepared using a number of formulation recipes and induration conditions. Physical and structural properties of the resultant sorbents were measured, and reactivity and durability screening tests were carried out using a single pellet electrobalance reactor. The formulation variables studied were ZnO to Fe2O3 ratio, Fe2O3 source, and the addition of inorganic (bentonite) and organic (methocel) binders to the sorbents. Pellet induration conditions ranged from 0.25 hours at 815°C to 4.0 hours at 1038°C. Stronger pellets having greater attrition resistance resulted when 5% bentonite was added to the formulation recipe and when the pellets were indurated at high temperature for extended times. In contrast, bentonite content was not a significant factor in determining sorbent reactivity and durability, both of which were improved by mild induration conditions. Sorbent regeneration temperature was found to be an important factor in improving reaction durability, as was the addition of 0.5% methocel to the formulation recipe. Pellets containing catalyst-grade Fe2O3 were more reactive than those containing pigment-grade Fe2O3. This effect, however, was less important than the effect of induration conditions. 相似文献
994.
Examined intake profiles of 54 depressed women survivors of child sexual abuse presenting for a specialized group therapy program at a community mental health center. The 32 therapy completers were compared with the 22 dropouts. Both groups possessed extensive and severe childhood and adult abuse histories. Both were extremely socially disadvantaged and clinically impaired as measured on the Millon Clinical Multiaxial Inventory (MCMI). Dropouts were more likely to have been battered as children and to have been sexually abused only within the family. Completers were more likely to have been multiply offended both by intrafamilial and extrafamilial perpetrators. The groups differed in terms of marital status and extent of economic dependence on spouse. Dropouts appeared to be more actively enmeshed in the abuse cycle at the time of therapy. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
995.
996.
In 12 men aged 20-25 men who had minor craniocerebral trauma the profiles of daily secretion of ACTH, beta-endorphin and cortisol were studied. The studies were carried out on the second day after the trauma. Plasma concentrations of the hormones were determined on 8.00, 12.00, 17.00 and 22.00 hours. Statistically significantly increased, in relation to healthy persons, (p < 0.01) values of plasma hormone concentration were found at all time points. In 50% of the patients (six cases) a disturbance was found of the profile of daily secretion of ACTH and beta-endorphin. The disturbance of the profile of cortisol secretion was found only in one patient. 相似文献
997.
Rosenfarb Irwin S.; Goldstein Michael J.; Mintz Jim; Nuechterlein Keith H. 《Canadian Metallurgical Quarterly》1995,104(2):259
The authors examined whether young, recently discharged schizophrenic patients from high (n?=?34) and low (n?=?14) expressed emotion (EE) families differ in their level of subclinical symptomatology during a direct interaction task. Compared with patients from low-EE homes, patients from high-EE homes showed significantly more odd and disruptive behavior with family members. High-EE relatives were more likely than low-EE relatives to respond with criticism to the first unusual thought verbalized by the patient; when this occurred, the probability of a second unusual thought was augmented. Results suggest that high-EE family members may display negative attitudes toward patients in part because they are exposed to higher levels of unusual or disruptive behavior than low-EE relatives. The data also support a bidirectional, transactional model of the relationship between relatives' EE and patient psychopathology. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
998.
Granularity is a well known concept in parallel processing. While intuitively, the distinction between coarse-grain and fine-grain paralellism is clear, there is no rigorous definition. This paper develops two notions of granularity, each defined formally and represented by a single rational number. The two notions are compared and contrasted with each other and with previously proposed definitions of granularity.Supported, in part, by NSA OCREAE Grant MDA904-85-H-0002. Currently on leave at the National Science Foundation. 相似文献
999.
1000.
What does keeping one's eye on the ball mean? 总被引:2,自引:0,他引:2