全文获取类型
收费全文 | 29033篇 |
免费 | 1223篇 |
国内免费 | 109篇 |
专业分类
电工技术 | 373篇 |
综合类 | 229篇 |
化学工业 | 4930篇 |
金属工艺 | 623篇 |
机械仪表 | 582篇 |
建筑科学 | 964篇 |
矿业工程 | 93篇 |
能源动力 | 933篇 |
轻工业 | 3850篇 |
水利工程 | 241篇 |
石油天然气 | 150篇 |
武器工业 | 6篇 |
无线电 | 2243篇 |
一般工业技术 | 4093篇 |
冶金工业 | 7104篇 |
原子能技术 | 238篇 |
自动化技术 | 3713篇 |
出版年
2023年 | 137篇 |
2022年 | 389篇 |
2021年 | 780篇 |
2020年 | 532篇 |
2019年 | 598篇 |
2018年 | 685篇 |
2017年 | 767篇 |
2016年 | 722篇 |
2015年 | 549篇 |
2014年 | 850篇 |
2013年 | 1400篇 |
2012年 | 1250篇 |
2011年 | 1575篇 |
2010年 | 1150篇 |
2009年 | 1200篇 |
2008年 | 1093篇 |
2007年 | 957篇 |
2006年 | 769篇 |
2005年 | 832篇 |
2004年 | 899篇 |
2003年 | 807篇 |
2002年 | 786篇 |
2001年 | 689篇 |
2000年 | 537篇 |
1999年 | 548篇 |
1998年 | 2288篇 |
1997年 | 1454篇 |
1996年 | 1022篇 |
1995年 | 660篇 |
1994年 | 519篇 |
1993年 | 576篇 |
1992年 | 222篇 |
1991年 | 289篇 |
1990年 | 233篇 |
1989年 | 201篇 |
1988年 | 214篇 |
1987年 | 163篇 |
1986年 | 173篇 |
1985年 | 182篇 |
1984年 | 128篇 |
1983年 | 92篇 |
1982年 | 120篇 |
1981年 | 128篇 |
1980年 | 122篇 |
1979年 | 91篇 |
1978年 | 76篇 |
1977年 | 182篇 |
1976年 | 301篇 |
1975年 | 83篇 |
1973年 | 49篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
991.
Müller MC Belei P de la Fuente M Strake M Kabir K Weber O Radermacher K Wirtz DC 《Proceedings of the Institution of Mechanical Engineers. Part H, Journal of engineering in medicine》2011,225(5):477-486
Pertrochanteric femoral fractures are common and intramedullary nailing is an accepted method for their surgical treatment. Accurate placement of the implant is essential to ensure fixation. The conventional technique can require multiple guide wire passes, and relies heavily on fluoroscopy. A computer-assisted planning and navigation system based on two-dimensional fluoroscopy for guide wire placement in the femoral neck has been developed, in order to perform intramedullary pertrochanteric fracture fixation using the proximal femoral nail (PFNA). The planning process was supported by a 'zero-dose C-arm navigation' system. The PFNA was inserted into 12, intact, femoral sawbones guided by the computer-based navigation, and into 12, intact, femoral sawbones using a conventional fluoroscopic-assisted technique. Guide wire and subsequent blade placement in the femoral neck was evaluated. The computer-assisted technique achieved a significant decrease in the number of required fluoroscopic images and in the number of guide wire passes. The obtained average blade placement accuracy in the femoral neck was equivalent to the conventional technique. The operation time was significantly longer in the navigation-assisted group. The addition of computer-assisted planning and surgical guidance to the intramedullary nailing of pertrochanteric femoral fractures offers a number of clinical benefits based on the results of this sawbone study. Further studies including fractured sawbones and cadaver models with extension of the navigation process to all steps of PFNA introduction and with the goal of reducing operation time are indispensable before integration of this navigation system into clinical practice. 相似文献
992.
Pastor JF Barbosa M de Paz FJ García M Ferrero E 《Microscopy research and technique》2011,74(10):910-919
The eight current species of bear (Ursidae) are widely distributed throughout Europe, Asia, and America. They are mainly encountered in the northern hemisphere, except for the spectacled bear and the sun bear, which are also found in the south of the equator. Adaptations of the masticatory apparatus (teeth, tongue, and musculature) to diet are one of the factors that imply the greatest structural changes in the cranium. This diet may be carnivorous, herbivorous, melliferous, or insectivorous, with one type of food predominating according to the time of year. The way in which food is eaten determines the morphology of the lingual surface; generally speaking, all bears put their mouth to the food, which, initially, they lick or they let the food stick to their tongue, as occurs when insects are eaten. As in all mammals, a distinction can be made between mechanical and gustatory papillae and the development and distribution of which depend on the species and their eating habits. In this study of the complete tongues of four species of adult bears, we describe the morphology of the lingual surfaces, the different types of papillae, their characteristics, and topographic distribution. It was seen that there were five main types of lingual papillae: filiform, conical, fungiform, foliate, and vallate. Morphology of the microgrooves and pores was similar to that observed in other mammals. In general, there were no great differences among the four species of bears studied, perhaps due to the similarity in the kind of food they consume in captivity. 相似文献
993.
椭球封头圆柱形爆炸容器振动特性研究 总被引:2,自引:1,他引:2
对椭球封头圆柱形爆炸容器在中心点爆炸状态下的 19次有效炮实验给予了介绍并对实验结果的壳体振动特性进行了分析。理论和实验分析表明 ,在封闭容器内爆炸冲击载荷具有明显的脉冲激励特征 ;容器壳体的振动频谱主要受前 10阶固有频率的影响 ;随着冲击载荷的增加 ,其壳体的主振频率将趋于相应壳体的呼吸频率 ,其应变增长具有减少的趋势 ;联接螺栓的振动模态主要受相应圆柱壳体和封头轴向振动模态的影响 ,并出现了在时域上其振动模态在圆柱壳振动模态和封头轴向振动模态间跳变的现象。 相似文献
994.
Bettina?Sch?ne-SeifertEmail author Daniel?R.?Friedrich Anke?Harney Stefan?Huster Heiner?Raspe 《Ethik in der Medizin》2018,30(4):325-341
Definition of the problem
“Medical necessity” (MedN) is the central regulatory concept for decisions about which services are covered by German statutory health insurance. Despite its seeming objectivity and dependence on physicians’ expert judgment, the concept is by no means clearly defined.Arguments
In this first of five planned papers on the conceptual analysis of MedN from the perspectives of philosophy and ethics of medicine, law, and (social) medicine, the focus lies on systemizing ongoing controversies.Conclusion
Our goal is to come up with a so far missing foundation for detailed debates. We aim to clarify MedN’s conceptual structure, function, contextuality, and ambiguities as well as the fundamental limits of conceptual investigations for the normative questions at issue of regulating medical services.995.
996.
Background
The international recruitment and migration of health workers has long been debated in the health policy literature. This study assesses to what extent the ethics of international recruitment are targeted in existing public health peer-reviewed literature, with a focus on concepts and in-depth consideration within articles. It further critically discusses hidden implications of this discourse regarding equity-creating health policy.Methods
We conducted a qualitative scoping literature review searching the databases PubMed and Web of Science. Articles were assessed for quality using the Critical Appraisal Skills Program (CASP) checklist for qualitative research. Drawing on a thematic analysis approach, common themes across the sample were identified, coded and analyzed.Results
A total of 17 articles were included in the analysis after searches and quality appraisal. These articles predominantly targeted nursing professions and physicians, and were written mainly by authors working in the Global North. Thematic analysis revealed that ethics are generally discussed in connection with overviews regarding the situation of health systems as well as regarding inequities between countries. Their focus lies more on migration between countries than between regions within a country. Proposed solutions are usually of an economic nature and range from global financial equalization between countries to national improvements in working conditions. Creative evaluation schemes for these solutions are rarely discussed in depth. Overall, the academic ethics discussion focuses predominantly on the health systems level, and views migration of health workers as problematic.Conclusions
Our results suggest that academic research operates and aims to inform policy within the current system, without necessarily proposing fundamental changes to the status quo. Thus, an ethics discourse of health workforce recruitment may serve to increase awareness of inequalities without supporting radical change. Further research into intersectional aspects of health worker migration, including gender and ethnicity, may be useful for the discussion on inequities.997.
998.
Definition of the problem
The concept of “ethics” has recently been incorporated into both the 2014 Model Professional Code for Dentists and the current version of the “National Competence-Based Catalog of Learning Objectives in Dental Medicine” (NKLZ, Nationaler Kompetenzbasierter Lernzielkatalog Zahnmedizin). The study presented here addresses the question which relevance this has for the relevance of the new concept accomplished for the dental profession and society.Arguments
To this end, the societal processes that are related to the autonomous freedom of action of the dental profession are discussed. Therefore the sociological fields of discourse such as profession (and the effect of its constitutive antinomies), trust, education, expertise, practice of treatments and sanction are reviewed for their potential of having connections to each other and serving as a structural frame concerning an ethically reflected acting of the professional. The basis of the professional freedom of action is the trust of society and the individual patient in the professionally acting dentist.Conclusion
The study arrives at the conclusion that it was a serious omission for many decades not to make young dentists aware of the ethical foundations of dental activity on an institutionally established basis and thus failing to encourage them to constantly reflect their professional expertise in relation to the problems to be solved. This deficit has now been identified. It is absolutely essential to implement an institutionalized structure dealing with ethical questions within the scope of dental medicine.999.
1000.
Daniël D. Heikoop Joost C.F. de Winter Bart van Arem Neville A. Stanton 《Theoretical Issues in Ergonomics Science》2016,17(3):284-303
As automation in vehicles becomes more prevalent, the call for understanding the behaviour of the driver while driving an automated vehicle becomes more salient. Although a variety of driver behaviour models exist, and various psychological constructs have been said to be influenced by automation, an empirically testable psychological model of automated driving has yet to be developed. Building upon Stanton and Young's model of driving automation, this article presents an updated model of interrelated psychological constructs. The proposed model was created based upon a systematic literature search of driving automation papers and a subsequent quantification of the number of reported links between a selected set of psychological constructs. A secondary aim of this article is to reach consensus in the use of psychological constructs regarding driving automation. Henceforth special attention is paid to resolving the issue of construct proliferation. 相似文献