全文获取类型
收费全文 | 21870篇 |
免费 | 1178篇 |
国内免费 | 603篇 |
专业分类
电工技术 | 773篇 |
技术理论 | 14篇 |
综合类 | 2699篇 |
化学工业 | 2912篇 |
金属工艺 | 616篇 |
机械仪表 | 1049篇 |
建筑科学 | 2928篇 |
矿业工程 | 1068篇 |
能源动力 | 539篇 |
轻工业 | 1848篇 |
水利工程 | 780篇 |
石油天然气 | 1223篇 |
武器工业 | 192篇 |
无线电 | 895篇 |
一般工业技术 | 1566篇 |
冶金工业 | 2423篇 |
原子能技术 | 171篇 |
自动化技术 | 1955篇 |
出版年
2024年 | 29篇 |
2023年 | 218篇 |
2022年 | 384篇 |
2021年 | 516篇 |
2020年 | 630篇 |
2019年 | 388篇 |
2018年 | 335篇 |
2017年 | 441篇 |
2016年 | 547篇 |
2015年 | 642篇 |
2014年 | 1619篇 |
2013年 | 1179篇 |
2012年 | 1564篇 |
2011年 | 1667篇 |
2010年 | 1351篇 |
2009年 | 1402篇 |
2008年 | 1156篇 |
2007年 | 1362篇 |
2006年 | 1409篇 |
2005年 | 1142篇 |
2004年 | 929篇 |
2003年 | 857篇 |
2002年 | 693篇 |
2001年 | 574篇 |
2000年 | 439篇 |
1999年 | 355篇 |
1998年 | 265篇 |
1997年 | 184篇 |
1996年 | 206篇 |
1995年 | 122篇 |
1994年 | 98篇 |
1993年 | 88篇 |
1992年 | 59篇 |
1991年 | 43篇 |
1990年 | 65篇 |
1989年 | 43篇 |
1988年 | 49篇 |
1987年 | 34篇 |
1986年 | 30篇 |
1984年 | 42篇 |
1982年 | 25篇 |
1971年 | 22篇 |
1966年 | 28篇 |
1965年 | 20篇 |
1964年 | 29篇 |
1963年 | 21篇 |
1959年 | 30篇 |
1957年 | 21篇 |
1955年 | 32篇 |
1954年 | 26篇 |
排序方式: 共有10000条查询结果,搜索用时 125 毫秒
11.
本文借助计算机中的视觉自动检测技术来测量在果实表面的着色度,并对该颜色进行了分级,进一步的对颜色进行分析与研究,进而来获得出最终的水果果实的彩色图像,进一步的分析出对应的结果。因此,在本文中,对果实表面颜色进行了全面综合的分析与研究,进而来得出对应的果实颜色分级标准和原则。 相似文献
12.
Carriers of genetic material are divided into vectors of viral and non-viral origin. Viral carriers are already successfully used in experimental gene therapies, but despite advantages such as their high transfection efficiency and the wide knowledge of their practical potential, the remaining disadvantages, namely, their low capacity and complex manufacturing process, based on biological systems, are major limitations prior to their broad implementation in the clinical setting. The application of non-viral carriers in gene therapy is one of the available approaches. Poly(amidoamine) (PAMAM) dendrimers are repetitively branched, three-dimensional molecules, made of amide and amine subunits, possessing unique physiochemical properties. Surface and internal modifications improve their physicochemical properties, enabling the increase in cellular specificity and transfection efficiency and a reduction in cytotoxicity toward healthy cells. During the last 10 years of research on PAMAM dendrimers, three modification strategies have commonly been used: (1) surface modification with functional groups; (2) hybrid vector formation; (3) creation of supramolecular self-assemblies. This review describes and summarizes recent studies exploring the development of PAMAM dendrimers in anticancer gene therapies, evaluating the advantages and disadvantages of the modification approaches and the nanomedicine regulatory issues preventing their translation into the clinical setting, and highlighting important areas for further development and possible steps that seem promising in terms of development of PAMAM as a carrier of genetic material. 相似文献
13.
Perceived situational appropriateness crucially informs decisions about what to eat and drink, and this contextual-cognitive factor of food choice helps to understand why in certain situations, despite high acceptability, a non-consumption decision is made. Being shaped primarily by accumulated experience and familiarity, appropriateness is influenced by culture, but inter-individual variability within populations also exists. Consumer segmentation based on appropriateness ratings was recently reported in work with Australian consumers, with segment differences relating to how adaptive or conforming consumers’ perceptions were of appropriateness for a range of foods and beverages (F&B) for use in daily main eating occasions [Jaeger et al.; Fd. Qual. Pref., 2019, e103701]. Believing in the strength and value of cumulative evidence, the present research was informed by the broad paradigm of replication and extension. This directed that empirical execution, data analysis and reporting strategy directly and extensively defined this work. In two studies with consumers from Denmark (n = 780) and New Zealand (NZ, n = 448), partial replication was achieved for situationally Adaptive and Conforming consumer segments in regard to breakfast, lunch and dinner (morning, midday and evening meals, respectively). Extending to three different eating occasions in NZ, partial replication of Adaptive and Conforming consumer segments was obtained. It appeared that these segments exist for some but not all eating occasions and that cultural differences are also at play. The present research also replicated the relationship between perceived appropriateness and F&B liking/disliking, whereby liked products can be both appropriate and inappropriate, depending on the eating occasions. Consumer segments based on appropriateness ratings had similar profiles, which also replicated Jaeger et al. (2019). 相似文献
14.
Paweł Lula Octavian Dospinescu Daniel Homocianu Napoleon-Alexandru Sireteanu 《计算机、材料和连续体(英文)》2021,66(3):2425-2443
Our primary research hypothesis stands on a simple idea: The evolution of top-rated publications on a particular theme depends heavily on the progress and maturity of related topics. And this even when there are no clear relations or some concepts appear to cease to exist and leave place for newer ones starting many years ago. We implemented our model based on Computer Science Ontology (CSO) and analyzed 44 years of publications. Then we derived the most important concepts related to Cloud Computing (CC) from the scientific collection offered by Clarivate Analytics. Our methodology includes data extraction using advanced web crawling techniques, data preparation, statistical data analysis, and graphical representations. We obtained related concepts after aggregating the scores using the Jaccard coefficient and CSO Ontology. Our article reveals the contribution of Cloud Computing topics in research papers in leading scientific journals and the relationships between the field of Cloud Computing and the interdependent subdivisions identified in the broader framework of Computer Science. 相似文献
15.
16.
17.
我国是富煤贫油少气的国家,煤炭是我国最重要的一次能源。但从能源激烈的竞争市场环境而言,当前我国煤炭行业发展出现了困境。为了更好地发展六盘水地区的煤炭行业,结合竞争战略理论和六盘水市的煤炭行业发展状况,运用PEST分析法和波特五力模型对六盘水市煤炭行业进行分析,得出整合资源,结合自身优势大力吸引人才,最终达到产业转型的生态化煤炭发展战略模型。分析结果可为提高六盘水煤炭行业竞争力提供理论支持。 相似文献
18.
In this research, we utilise a multi-method braided approach for a real-world health care intervention in rural India. We first use action research to conceptually underpin the role of self-help groups, disease profiles and appropriate interventions in health care behaviour change and improvement. Action research is then coupled with a non-linear integer-programming-based simulation to determine how health care resources need to be distributed over time, disease type and groups. The action research provides specific research questions and distributional forms needed for the optimisation analysis, while the non-linear integer-programming simulation provides specific recommendations on where and when to distribute resources. External validity of the study is ensured by the adoption of recommendations in the field as part of the action research. Findings from this research have important policy implications. For example, it identifies the value of continuous embedded interventions as opposed to periodic ones and the importance of flexibility in terms of which community groups and disease types to serve over time. This research also provides an important bridge between the operations research, health care in developing nations, organisational theory and humanitarian operations bodies of knowledge. 相似文献
19.
在经济不断发展的大背景下,人们的审美意识也不断增强,对于建筑材料与环境艺术的融合提出了更高的要求,并在现在的环境艺术设计中加入了更多新鲜有趣的理念。然而由于固有理念的束缚和一味求新、求变思想的出现,对于传统建筑材料的使用却遇到了不足。其实,在当代环境艺术设计中,环境设计的基本元素,不仅要能表现艺术,在视角和造景效果上也要能体现出很大的美学价值。本文结合当前传统建材料的应用情况,对其与当代环境艺术设计的结合做一个简单的阐述,对实际设计的美学造诣深入探究,让有价值的传统建筑材料绽放光彩。 相似文献
20.
"三违"行为是导致煤矿生产安全事故发生的主要因素,本文在对企业及工人等各个方面开展调查的基础上,分析煤矿企业"三违"现状、产生原因,提出反"三违"的措施建议,可指导煤矿规范操作行为,有效防范事故发生。 相似文献