全文获取类型
收费全文 | 3851篇 |
免费 | 2篇 |
专业分类
化学工业 | 12篇 |
机械仪表 | 1篇 |
轻工业 | 25篇 |
水利工程 | 1篇 |
无线电 | 2篇 |
一般工业技术 | 2篇 |
冶金工业 | 3800篇 |
自动化技术 | 10篇 |
出版年
2019年 | 1篇 |
2018年 | 1篇 |
2017年 | 2篇 |
2013年 | 1篇 |
2012年 | 3篇 |
2011年 | 3篇 |
2009年 | 2篇 |
2008年 | 3篇 |
2006年 | 2篇 |
2005年 | 1篇 |
2004年 | 5篇 |
2003年 | 14篇 |
2000年 | 2篇 |
1999年 | 137篇 |
1998年 | 1252篇 |
1997年 | 779篇 |
1996年 | 475篇 |
1995年 | 232篇 |
1994年 | 215篇 |
1993年 | 219篇 |
1992年 | 19篇 |
1991年 | 31篇 |
1990年 | 35篇 |
1989年 | 46篇 |
1988年 | 31篇 |
1987年 | 26篇 |
1986年 | 22篇 |
1985年 | 24篇 |
1984年 | 1篇 |
1983年 | 5篇 |
1982年 | 13篇 |
1981年 | 23篇 |
1980年 | 28篇 |
1979年 | 3篇 |
1978年 | 4篇 |
1977年 | 57篇 |
1976年 | 133篇 |
1975年 | 2篇 |
1970年 | 1篇 |
排序方式: 共有3853条查询结果,搜索用时 15 毫秒
91.
92.
93.
J Hernández Martínez FJ Ruiz López JJ Martínez Garcerán MC Abellán Martínez P Méndez Martínez F Sánchez Gascón 《Canadian Metallurgical Quarterly》1997,33(1):50-51
Foreign body aspiration requires emergency bronchoscopic examination when the product is chemically active. We describe the case of a female patient who aspirated a ferrous sulfate tablet that, in spite of being extracted immediately, caused lesions that persisted in the bronchial tree for 6 weeks. We then discuss the potential of ferrous sulfate substance to cause damage to the tracheobronchial tree. 相似文献
94.
95.
The matrix metalloproteinases appear to play a key role in mammary tissue remodeling during involution. By immunoprecipitation and immunoblot using antibodies against 60K gelatinase which appears during involution a 90K polypeptide has been identified as its inactive proenzyme in the early involuting rat mammary gland. 90K polypeptide was isolated from the second day involuting rat mammary gland by immunoaffinity chromatography. On proteolytic digestion, the inactive 90K polypeptide was converted to active gelatinase. Primary cultures of mammary epithelial cells secreted the 90K polypeptide. These results indicated that the 60K inducible MMP involved in mammary gland involution and remodeling is produced as a 90K proenzyme which is activated by proteolysis in the extracellular sites. 相似文献
96.
A Segovia Martínez C Pérez Fuentes J Torío Durántez MC García Tirado 《Canadian Metallurgical Quarterly》1998,22(9):562-569
OBJECTIVES: To find the social, demographic and family characteristics, the psychological malaise and reasons for consultation of normal and hyper-attenders at a primary care practice. DESIGN: Crossover study with a control. SETTING: Primary care. PATIENTS: 127 hyper-attenders (they attended the practice as often as, or more often than, the mean number of visits, stratified by sex and age) and 120 normal attenders chosen by stratified random sampling. INTERVENTIONS: Questionnaire with characterisation data, family demography, psychological malaise (Goldberg general health questionnaire) and reasons for consultation. RESULTS: To be considered a hyper-attender, the number of attendances per year ranged from > or = 8 (in 15 to 44-year olds) to > or = 20 (in men over 65). Hyper-attenders were about 12% of almost all groups, except in men between 45 and 64 and women over 64, in whom it was around 18%. We found no relevant differences between normal and hyper-attenders as to demography or perception of family function. In almost 60% of hyper-attenders and 34% of normal attenders (p < 0.001), psychological malaise was detected. CONCLUSIONS: If the definition of hyper-attenders is stratified by age and sex, their social and demographic characteristics are very different from in other studies, even though there are a similar number of them. However, these demographic and/or family characteristics are similar in normal and hyper-attenders. 相似文献
97.
M Carlier E Spitz MC Vacher-Lavenu P Villéger B Martin F Michel 《Canadian Metallurgical Quarterly》1996,26(4):409-407
Manual performance, direction, and degree of laterality were tested in monozygotic (MZ) twins (8-12 years old) of known chorion type and dizygotic (DZ) twins. Three manual tasks rarely employed in twin studies were used; dot-filling, tapping, and peg-moving tasks. No chorion effect was observed: the monochorionic and dichorionic MZs differed neither for frequency of discordant pairs nor for handedness, laterality measurements, and manual performance. The pooled MZs and DZs were then compared in a classic twin design. The within-pair resemblance was not higher in MZs than in DZs for variables measuring level of manual performance. For laterality scores intraclass correlations were close to zero in MZ and DZ twin groups. 相似文献
98.
MC Rodriguez-Matas F Lisbona AE Gómez-Ayala I López-Aliaga MS Campos 《Canadian Metallurgical Quarterly》1998,32(3):298-306
The permanent fibrocyte-like fish cell line RTG-2 from rainbow trout (Oncorhynchus mykiss) gonads was investigated by means of light and scanning electron microscopy with respect to alterations as a consequence of sublethal exposure to 0, 1, 10, 16, 25, and 50 mg/liter 3,5-dichlorophenol (3,5-DCP) for 24 h. Control RTG-2 cells were spindle-like in shape and almost three times longer than wide. In subconfluent cultures, they displayed widely spread, flat leading lamellae and formed small groups. Along the edges of the cell protrusions, numerous retraction fibrils could be identified. Except for shallow ridges and small folds, the surface of untreated cells was completely smooth. Following exposure to 3,5-DCP, distinct dose-dependent alterations in cell shape, the appearance of surface blebs and invaginations, as well as progressive retraction of cell extensions could be observed from the lowest test concentration. Morphological changes could be correlated to suppression of lactate dehydrogenase and reduced neutral red retention capacity. 相似文献
99.
100.