全文获取类型
收费全文 | 1595篇 |
免费 | 1篇 |
专业分类
综合类 | 52篇 |
化学工业 | 37篇 |
金属工艺 | 1篇 |
机械仪表 | 5篇 |
建筑科学 | 31篇 |
轻工业 | 10篇 |
水利工程 | 2篇 |
无线电 | 1篇 |
一般工业技术 | 10篇 |
冶金工业 | 1423篇 |
自动化技术 | 24篇 |
出版年
2023年 | 2篇 |
2022年 | 1篇 |
2020年 | 1篇 |
2019年 | 2篇 |
2018年 | 3篇 |
2015年 | 11篇 |
2014年 | 18篇 |
2013年 | 16篇 |
2012年 | 16篇 |
2011年 | 11篇 |
2010年 | 14篇 |
2009年 | 12篇 |
2008年 | 15篇 |
2007年 | 11篇 |
2006年 | 4篇 |
2005年 | 2篇 |
2004年 | 8篇 |
2003年 | 8篇 |
2002年 | 1篇 |
2001年 | 2篇 |
1999年 | 38篇 |
1998年 | 397篇 |
1997年 | 239篇 |
1996年 | 153篇 |
1995年 | 103篇 |
1994年 | 84篇 |
1993年 | 92篇 |
1992年 | 12篇 |
1991年 | 28篇 |
1990年 | 27篇 |
1989年 | 31篇 |
1988年 | 25篇 |
1987年 | 27篇 |
1986年 | 18篇 |
1985年 | 14篇 |
1983年 | 3篇 |
1982年 | 8篇 |
1981年 | 6篇 |
1980年 | 8篇 |
1978年 | 5篇 |
1977年 | 32篇 |
1976年 | 82篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1971年 | 1篇 |
1965年 | 1篇 |
1960年 | 1篇 |
1954年 | 1篇 |
排序方式: 共有1596条查询结果,搜索用时 15 毫秒
81.
82.
83.
OBJECTIVES: This study sought to identify risk markers associated with the provision of new restorations in children and to investigate whether the carious status of a tooth surface is associated with the restorative decisions of dentists. METHODS: A total of 911 schoolchildren in grades one, two, and three were randomly selected from the island of Montreal, Quebec, Canada. Dental examinations were carried out in 1990, 1991, and 1992. Tooth surfaces of first permanent molars were classified as sound, noncavitated, and cavitated. The carious status of a tooth was matched with restorative decisions reported to the insurance board. RESULTS: The presence of a carious cavity was a strong risk marker for placement of new restorations (odds rations > or = 4.11). After one year, less than 2 percent of sound tooth surfaces of first permanent molars were restored and about 21 percent of noncavitated tooth surfaces were restored. When new class I restorations placed in maxillary first permanent molars within 3-6 months after the baseline examination were evaluated, we found that between 73 percent and 86 percent of these new restorations were placed in sound or noncavitated tooth surfaces. A similar trend also was observed in mandibular first permanent molars. Poor agreement between epidemiologic diagnosis and restorative decisions was found. The restorative profile of dentists was a significant risk marker for placement of new restorations. CONCLUSION: The majority of new restorations in first permanent molars were placed in sound and noncavitated tooth surfaces because of the ubiquitous prevalence of these tooth surfaces and the validity problems of current caries diagnosis methods. 相似文献
84.
PR Burchat GJ Feldman T Barklow AM Boyarski DL Burke JM Dorfan L Gladney G Hanson K Hayes RJ Hollebeek WR Innes JA Jaros D Karlen AJ Lankford RR Larsen BW LeClaire NS Lockyer V Lüth C Matteuzzi RA Ong ML Perl B Richter K Riles MC Ross JM Yelton C Zaiser GS Abrams D Amidei AR Baden J Boyer F Butler G Gidal MS Gold G Goldhaber L Golding J Haggerty D Herrup I Juricic JA Kadyk ME Nelson PC Rowson H Schellman WB Schmidke PD Sheldon GH Trilling de la Vaissiere C DR Wood ME Levi T Schaad 《Canadian Metallurgical Quarterly》1987,35(1):27-41
85.
Massive hemorrhage caused by a perforating Gianturco-Z stent resulting in an aortoesophageal fistula
PD Siersema TG Tan FF Sutorius J Dees M van Blankenstein 《Canadian Metallurgical Quarterly》1997,29(5):416-420
Squamous cell carcinoma of the tonsil has a relatively poor prognosis. Aggressive surgery, radiation therapy and combinations of irradiation and surgery have been employed but there exists some controversy about the efficacy of these treatment modalities. The purpose of this paper is to compare the efficacy of treatment between the surgery followed by radiation therapy and the preoperative radiation therapy followed by surgical resection. The medical records of 33 patients treated for squamous cell carcinoma of the tonsil at the Department of Otolaryngology-Head and Neck Surgery, Korea University Hospital between 1989-1993 were reviewed retrospectively. None of the patients were stage I, but stage II, III, and IV were four, five, and 24 patients, respectively. There were 30 males and three females. The most common histopathology was moderately differentiated squamous cell carcinoma (20/33). The 13 patients treated initially with surgery had an overall three-year survival rate of 38.5%, and the rate for the 20 patients treated initially with radiation was 40%. The main pattern of treatment failure was a local recurrence and neck metastases, and pathologic differentiation thought to be an important prognostic factor. Complications are fewer in patients treated initially with surgery (23.1%) than patients initially treated with radiation (50.0%). There is no difference in the efficacy between the two therapeutic groups. 相似文献
86.
JP Vuillez E Levrot M Mousseau PD Buffaz M Bolla R Payan M Comet R Schaerer 《Canadian Metallurgical Quarterly》1997,84(11):1033-1042
Immunoscintigraphy using indium-111-labeled OC125 monoclonal antibody F(ab')2 fragments is a technic complementary of morphological imaging (i.e. ultrasonography and computed tomography). It allows early detection of recurrences of ovarian carcinomas. We performed immunoscintigraphy 30 times in 26 patients who previously underwent radical treatment for ovarian carcinoma, and were suspected to have a recurrence. Our purposes were appreciation of diagnostic accuracy of the method, and above all its impact on clinical decisions and evolution of the patients. There were, after reevaluation of the results, 18 true positives, 7 true negatives, 3 false negatives and 2 false positive cases (sensitivity 85.7%, specificity 77.8%). Bayesian analysis showed positive and negative predictive values of 86% and 87% when probability of recurrence a priori was 50%, and 80% and 58% when probability of recurrence a priori was 70%. The result of immunoscintigraphy contributed to clinical decisions in 24 cases out of 30, and led to a correct decision for the patient in 21 cases. Conversely, for the 6 cases in which the result has not been considered, to take this result into account would have been beneficial in 4 cases, but harmful in 2. Finally, survival tended to be longer when immunoscintigraphy was negative, which could be associated with a better prognosis. We conclude that OC125-immunoscintigraphy may be useful for ovarian carcinoma follow-up and may contribute to a better therapeutic strategy. 相似文献
87.
Dipl.-Ing. C. Konrad Prof. Dr.-Ing. habil W. Walther Dipl.-Ing. T. Reimann Dr. rer. nat. A. Rogge Dipl.-Geol. P. Stengel PD Dr. sc. agr. R. Well 《Grundwasser》2008,13(1):42-49
Comparison of hydraulic and chemical properties of sediments from flush- and core drillings in the area of Peine (Germany). Because of financial constraints, investigations of nitrate metabolism are often based on disturbed borehole samples. It is arguable, however, whether disturbed samples are suitable for these types of investigations. Disadvantages of disturbed samples in comparison to undisturbed core samples are well known and include possible contamination of the sample by mud additives, destruction of the sediment formation and the insecurity concerning the correct depth allocation. In this study, boreholes were drilled at three locations to a maximum depth of 50?m. The extracted samples, as intact sediment cores and drill cuttings, were studied with regard to chemical and hydraulic parameters of the aquifer sediments. The results show: 1. hydraulic parameters are not affected by clay-based mud; 2. disturbed samples contain less fine grain material relative to the core samples, and the hydraulic conductivity can only be estimated from catch samples; 3. catch samples contain fewer reducing agents (sulphides, organic carbon) than core samples in hydraulically passive zones (defined as K < 10–6?m?·?s–1); 4. the results of analyses of disturbed and undisturbed core samples are in good agreement for hydraulically active zones (K ≥ 10–6?m?·?s–1). 相似文献
88.
89.
AK Souid MC Ziemba AS Dubansky M Mazur M Oliphant FD Thomas M Ratner PD Sadowitz 《Canadian Metallurgical Quarterly》1993,72(6):2042-2048
The authors presented the cases of two children with inflammatory myofibroblastic (IMF) tumor and reviewed the literature to facilitate the preoperative recognition, delineate the clinical features, and describe the natural history of this entity. The first child had IMF tumor arising from the mesentery of the small intestine. He presented with an abdominal mass associated with severe inflammatory response manifested by fever, impaired growth, thrombocytosis, and microcytic, hypochromic anemia. After surgical resection, his fever resolved and his growth rate and the laboratory abnormalities normalized. Five months after initial diagnosis, the fever, anemia, and thrombocytosis recurred along with two tumors arising from the omentum and the abdominal soft tissue. After the second surgery, he remains free of recurrent disease for 30 months. The second child presented with a lung mass that was radiologically indistinguishable from pulmonary sequestration. After surgical resection, she remains free of recurrent disease for 18 months. IMF tumor should be considered in any solid tumor that occurs in association with a chronic inflammatory response. IMF tumor should also be considered in the differential diagnosis of pulmonary sequestration. 相似文献
90.