全文获取类型
收费全文 | 1681篇 |
免费 | 6篇 |
专业分类
综合类 | 52篇 |
化学工业 | 48篇 |
金属工艺 | 5篇 |
机械仪表 | 2篇 |
建筑科学 | 33篇 |
能源动力 | 6篇 |
轻工业 | 15篇 |
水利工程 | 2篇 |
无线电 | 10篇 |
一般工业技术 | 15篇 |
冶金工业 | 1449篇 |
原子能技术 | 4篇 |
自动化技术 | 46篇 |
出版年
2023年 | 2篇 |
2020年 | 2篇 |
2019年 | 2篇 |
2018年 | 5篇 |
2017年 | 3篇 |
2015年 | 14篇 |
2014年 | 21篇 |
2013年 | 17篇 |
2012年 | 22篇 |
2011年 | 15篇 |
2010年 | 16篇 |
2009年 | 16篇 |
2008年 | 17篇 |
2007年 | 12篇 |
2006年 | 7篇 |
2005年 | 3篇 |
2004年 | 13篇 |
2003年 | 10篇 |
2002年 | 2篇 |
2001年 | 2篇 |
1999年 | 41篇 |
1998年 | 402篇 |
1997年 | 246篇 |
1996年 | 158篇 |
1995年 | 105篇 |
1994年 | 86篇 |
1993年 | 93篇 |
1992年 | 11篇 |
1991年 | 28篇 |
1990年 | 27篇 |
1989年 | 33篇 |
1988年 | 26篇 |
1987年 | 29篇 |
1986年 | 19篇 |
1985年 | 14篇 |
1983年 | 3篇 |
1982年 | 9篇 |
1981年 | 7篇 |
1980年 | 8篇 |
1978年 | 5篇 |
1977年 | 34篇 |
1976年 | 88篇 |
1975年 | 1篇 |
1974年 | 2篇 |
1973年 | 2篇 |
1971年 | 1篇 |
1969年 | 1篇 |
1965年 | 1篇 |
1960年 | 1篇 |
1954年 | 1篇 |
排序方式: 共有1687条查询结果,搜索用时 46 毫秒
111.
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
112.
Hanno Hardt 《The Journal of communication》1989,39(2):114-131
A review of U.S. press histories reveals a common failure to consider immigration and the formation of an ethnic press as constituent elements of an American culture and addresses the need for a cultural history of the media that breaks with current practices. 相似文献
113.
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
114.
115.
D O'Neill JA Morecroft AT Gibson PD Bull J Walker 《Canadian Metallurgical Quarterly》1999,2(2):176-179
We describe the clinical presentation and pathological features of an unusual case of tracheal agenesis. The axial derivatives of the primitive foregut between the larynx and stomach were represented by a single structure featuring sequential segmentation into regions showing exclusively tracheal or esophageal differentiation in a pattern that is not easily classified by existing nosologic systems nor explained by the conventional hypothesis of dysontogenesis. 相似文献
116.
117.
PD Dr. theol. habil. Arne Manzeschke 《Ethik in der Medizin》2011,23(4):271-282
Definition of the problem The hospital as an organization has undergone substantial changes during recent decades due to reforms in the health care system. There have been necessary and quite helpful modifications; however, some modifications raise the question: what public tasks should hospitals fulfill in the future? The following question, thus, arises: what kind of effectiveness, besides cutting costs, should be achieved by the permanent increase of efficiency in hospitals? Paradoxically spoken, the change of the organization hospital seems to be entailed by economization which at the same time is meant to be a remedy for change. Arguments This article reflects on the process of economization from an ethical perspective using patterns from organizational and institutional theory, e.g., a model to evaluate levels of economization contributed by the French sociologist Pierre Bourdieu, applied in this case to German hospitals. Conclusion Market-driven incentives are no answer to the question which goals (i.e., morally, socially, and legally) the health care system should meet. Therefore, public deliberation and performance-orientated shaping of the institutions is required. 相似文献
118.
119.
In recent years competitive pressure in mobile markets has increased remarkably. New business models and thus new actors have entered the market. This contribution analyzes the reconfiguration of value structures and strategies in mobile markets. For this purpose, mobile network operators?? service portfolio is analyzed on the basis of a worldwide survey, and the relevant current and future value creation activities are identified with consideration of additional actors and influence factors. On that basis, roles are developed, linked with regard to value flows and combined to a reference model for the mobile market value net. Subsequently, scenario planning is used to develop a set of criteria for the construction of corresponding future scenarios and the application of the reference model is demonstrated with such a scenario. 相似文献
120.