全文获取类型
收费全文 | 967篇 |
免费 | 2篇 |
专业分类
电工技术 | 1篇 |
化学工业 | 21篇 |
金属工艺 | 15篇 |
机械仪表 | 7篇 |
建筑科学 | 12篇 |
能源动力 | 1篇 |
轻工业 | 19篇 |
水利工程 | 16篇 |
石油天然气 | 1篇 |
无线电 | 13篇 |
一般工业技术 | 40篇 |
冶金工业 | 783篇 |
原子能技术 | 7篇 |
自动化技术 | 33篇 |
出版年
2021年 | 3篇 |
2019年 | 2篇 |
2018年 | 5篇 |
2015年 | 2篇 |
2014年 | 5篇 |
2013年 | 8篇 |
2012年 | 5篇 |
2011年 | 12篇 |
2010年 | 4篇 |
2009年 | 9篇 |
2008年 | 10篇 |
2007年 | 6篇 |
2006年 | 12篇 |
2005年 | 8篇 |
2004年 | 5篇 |
2003年 | 8篇 |
2002年 | 6篇 |
2001年 | 7篇 |
2000年 | 5篇 |
1999年 | 27篇 |
1998年 | 222篇 |
1997年 | 124篇 |
1996年 | 77篇 |
1995年 | 44篇 |
1994年 | 56篇 |
1993年 | 41篇 |
1992年 | 6篇 |
1991年 | 13篇 |
1990年 | 6篇 |
1989年 | 17篇 |
1988年 | 14篇 |
1987年 | 12篇 |
1986年 | 10篇 |
1985年 | 10篇 |
1984年 | 4篇 |
1983年 | 6篇 |
1982年 | 4篇 |
1981年 | 6篇 |
1980年 | 15篇 |
1979年 | 4篇 |
1978年 | 5篇 |
1977年 | 32篇 |
1976年 | 73篇 |
1975年 | 3篇 |
1974年 | 3篇 |
1972年 | 2篇 |
1969年 | 2篇 |
1959年 | 1篇 |
1955年 | 1篇 |
1948年 | 1篇 |
排序方式: 共有969条查询结果,搜索用时 15 毫秒
101.
Twenty-seven patients who had a unilateral displaced intra-articular fracture of the calcaneus were managed with a cast instead of with reduction or an operation. The clinical result after a mean of six years (range, two to ten years) was excellent in five patients, good in five, fair in seven, and poor in ten. The sixteen patients who were re-examined for this study and for whom the gait was analyzed demonstrated abnormalities in ground-reaction force with regard to vertical force (F3) and temporal force factors (T2, T3, T6, and T9). Analysis of temporal and distance factors showed a trend toward a decreased proportion of single-limb support on the involved side. Three-dimensional motion analysis of the ankle and hindfoot was performed with electrogoniometers as the subject walked on a level surface, on a 10-degree side-slope, and up and down stairs. Motion was decreased in the sagittal, coronal, and transverse planes during walking on level ground and on a side-sloping surface. Significant decreases in motion in these planes were also seen during walking up and down stairs. Although these patients did not have a subsequent reconstructive operation, most had a residual functional deficit. 相似文献
102.
Y Lee JW Kim IA Lee HB Kang YK Choe HG Lee JS Lim HJ Kim C Park IS Choe 《Canadian Metallurgical Quarterly》1996,39(4):833-842
Considerable genomic microdiversity has been reported previously among Helicobacter pylori isolates. We have constructed genome maps of four unrelated H. pylori strains (NCTC11637, NCTC11639, UA802 and UA861) using pulsed-field gel electrophoresis (PFGE) with NotI and NruI, hybridization with extracted PFGE DNA fragments and probing with 17 gene probes. These strains of H. pylori were compared with a fifth unrelated H. pylori strain NCTC11638 mapped previously. Considerable diversity in gene arrangement was evident among the five H. pylori maps, and no consistent gene clustering was found. The association of only four genes, katA (catalase gene), vacA (vacuolating cytotoxin gene), hpaA (a putative adhesin gene), and pfr (bacterial ferritin gene) were generally conserved within approximately the same 25% of the genome; however, the order of these genes also varied. Our study demonstrates that macrodiversity, i.e. variability in gene order, in addition to microdiversity, is a characteristic of the H. pylori genome. 相似文献
103.
Intermittent antegrade tepid versus cold blood cardioplegia in elective myocardial revascularization
AC Fiore MT Swartz R Nevett PJ Vieth RA Magrath A Sherrick HB Barner 《Canadian Metallurgical Quarterly》1998,65(6):1559-64; discussion 1564-5
BACKGROUND: The ideal temperature for blood cardioplegia administration remains controversial. METHODS: Fifty-two patients who required elective myocardial revascularization were prospectively randomized to receive intermittent antegrade tepid (29 degrees C; group T, 25 patients) or cold (4 degrees C; group C, 27 patients) blood cardioplegia. RESULTS: The two cohorts were similar with respect to all preoperative and intraoperative variables. The mean septal temperature was higher in group T (T, 29.6 degrees +/- 1.1 degrees C versus 17.5 degrees +/- 3.0 degrees C; p < 0.0001). After reperfusion, group T exhibited significantly greater lactate and acid release despite similar levels of oxygen extraction (p < 0.05). The creatine kinase-MB isoenzyme release was significantly lower in group T (764 +/- 89 versus 1,120 +/- 141 U x h/L; p < 0.04). Hearts protected with tepid cardioplegia demonstrated significantly increased ejection fraction with volume loading, improvement in left ventricular function at 12 hours, and decreased need for postoperative inotropic support (p < 0.05). The frequency of ventricular defibrillation after cross-clamp removal was lower in this cohort (p < 0.05). There were no hospital deaths, and both groups had similar postoperative courses. CONCLUSIONS: Intermittent antegrade tepid blood cardioplegia is a safe and efficacious method of myocardial protection and demonstrates advantages when compared with cold blood cardioplegia in elective myocardial revascularization. 相似文献
104.
The behavioural consequences of neonatal lesions of the frontal cortex are limited as compared with similar lesions performed in adulthood. The present study has investigated, using unbiased quantitative methods with randomized systematic sampling, the total neuronal cell numbers in the mediodorsal nucleus of the thalamus after aspiration lesions of the medial prefrontal cortex performed in neonatal and in adult rats. It was found that the reduction in total cell numbers after neonatal prefrontal cortex lesions was similar to that found after adult cortex lesions. In neonatally lesioned animals the neuronal cell density was significantly increased by 13%, whereas in adult lesioned animals it was unchanged. On the other hand, the volume of the mediodorsal nucleus was reduced by 27% in neonatally, and 20% in adult lesioned animals. Total neuronal cell number of the mediodorsal nucleus was significantly decreased in neonatally as well as in adult lesioned rats, by 14% and 21%, respectively. These findings are discussed in the light of the previously proposed role of the thalamus as a neural substrate of functional sparing after neonatal cortical lesions. 相似文献
105.
MA Gamba M Martinelli HJ Schaad RA Streuli J DiPersio L Matter HB Ris F Marchal EL Kaplan DL Stevens R Malinverni 《Canadian Metallurgical Quarterly》1997,24(6):1118-1121
Invasive group A streptococcus (GAS) infections are emerging diseases; however, person-to-person transmission of invasive GAS producing life-threatening infection has been observed rarely. We report a small intrafamilial cluster of life-threatening GAS infections. A previously healthy 47-year-old father developed necrotizing fasciitis of the neck. Two days later, his 16-year-old daughter developed streptococcal angina, pneumonia, and pleural empyema. Both patients had signs of streptococcal toxic shock syndrome. Pulsed field gel electrophoresis revealed that the M6 strains of GAS isolated from the father and daughter had identical patterns. Cases of person-to-person transmission of invasive GAS infection reported in the literature are also reviewed. 相似文献
106.
PURPOSE: Many patients with urological disease do not speak English. In medical studies restricting patients to those who speak only English undermines efforts to understand disease because restrictions decrease efficiency of patient recruitment, and because language and culture are associated with variable outcomes. In Spanish speaking locations, such as South Florida, studies would suffer severe selection bias if patients were required to speak English. To allow grouping in future studies of English and Spanish speaking patients we examined the English-Spanish reliability of select instruments that measure health related quality of life in patients with urological disease. MATERIALS AND METHODS: We assembled available Spanish versions and translated English versions of questions regarding satisfaction, the American Urological Association symptom index, the University of California, Los Angeles Prostate Cancer Index and a pain inventory. We then examined English-Spanish reliability by asking bilingual men 50 years old or older to complete English and Spanish versions at the same sitting. A convenience sample was recruited from outpatients and volunteers at the Miami Veterans Affairs Medical Center and population based subjects living in largely Hispanic Hialeah, Florida. Reliability estimates were calculated with kappa coefficients for categorical data and intraclass correlation coefficients for quantitative data. RESULTS: A total of 100 subjects a median of 59 years old completed the questionnaire, including 55 born in Puerto Rico or Cuba, while the remainder were born at various sites throughout the Americas and Spain. Reliability estimates showed that kappa = > 0.81 for almost all items. For 2 items relating to health and social interactions reliability was poor, and stratification showed that poor reliability was primarily a feature of subjects in good health who are theoretically socially active. CONCLUSIONS: Almost all items tested have excellent English-Spanish reliability in a mixed sample of bilingual men. Nonreliability of 2 items relating to health and social interactions probably originates from the effect of language on perception, and invalidates English and Spanish grouping of these items. Because the sample represents many dialects of Spanish, the translations tested may be transported to other cities. In studies that use these instruments investigators can reasonably group answers from English and Spanish speaking study subjects or study the effects of acculturation on quality of life. 相似文献
107.
Initiation of Myxococcus xanthus multicellular development requires integration of information concerning the cells' nutrient status and density. A gain-of-function mutation, sasB7, that bypasses both the starvation and high cell density requirements for developmental expression of the 4521 reporter gene, maps to the sasS gene. The wild-type sasS gene was cloned and sequenced. This gene is predicted to encode a sensor histidine protein kinase that appears to be a key element in the transduction of starvation and cell density inputs. The sasS null mutants express 4521 at a basal level, form defective fruiting bodies, and exhibit reduced sporulation efficiencies. These data indicate that the wild-type sasS gene product functions as a positive regulator of 4521 expression and participates in M. xanthus development. The N terminus of SasS is predicted to contain two transmembrane domains that would locate the protein to the cytoplasmic membrane. The sasB7 mutation, an E139K missense mutation, maps to the predicted N-terminal periplasmic region. The C terminus of SasS contains all of the conserved residues typical of the sensor histidine protein kinases. SasS is predicted to be the sensor protein in a two-component system that integrates information required for M. xanthus developmental gene expression. 相似文献
108.
109.
110.
OBJECTIVE: The aim of this study was to investigate audiologic features and the lesion site of sensorineural deafness with mitochondrial DNA mutation at position 3243. STUDY DESIGN: Case review. SETTING: The study was conducted at the Kochi Medical School. PATIENTS: A case of sensorineural deafness in a patient who had a mitochondrial DNA mutation was presented. The incidence of deafness and diabetes mellitus (DM) was very high in the patient's family, but she did not have DM. MAIN OUTCOME MEASURES: The patient's mitochondrial DNA was examined. Furthermore, the pure-tone audiogram, the Bekesy audiogram, an auditory brain stem response, and the electrocochleogram were analyzed. RESULTS: The patient's mitochondrial DNA had a point mutation at codon 3243 (A-->G). The pure-tone audiogram showed moderate sensorineural deafness. An auditory brain stem response showed normal latencies. The electrocochleogram showed an enhanced negative summating potential. CONCLUSIONS: It was speculated that the lesion site of the auditory system was the inner ear. The possible sites in the inner ear were hair cells, the stria vascularis, and the endolymphatic sac. 相似文献