全文获取类型
收费全文 | 2819篇 |
免费 | 222篇 |
国内免费 | 2篇 |
学科分类
工业技术 | 3043篇 |
出版年
2023年 | 46篇 |
2022年 | 24篇 |
2021年 | 120篇 |
2020年 | 88篇 |
2019年 | 73篇 |
2018年 | 98篇 |
2017年 | 94篇 |
2016年 | 121篇 |
2015年 | 114篇 |
2014年 | 147篇 |
2013年 | 168篇 |
2012年 | 164篇 |
2011年 | 183篇 |
2010年 | 108篇 |
2009年 | 129篇 |
2008年 | 129篇 |
2007年 | 115篇 |
2006年 | 79篇 |
2005年 | 92篇 |
2004年 | 71篇 |
2003年 | 73篇 |
2002年 | 55篇 |
2001年 | 32篇 |
2000年 | 42篇 |
1999年 | 37篇 |
1998年 | 104篇 |
1997年 | 60篇 |
1996年 | 34篇 |
1995年 | 48篇 |
1994年 | 26篇 |
1993年 | 25篇 |
1992年 | 20篇 |
1991年 | 13篇 |
1990年 | 17篇 |
1989年 | 21篇 |
1988年 | 14篇 |
1987年 | 15篇 |
1986年 | 14篇 |
1985年 | 10篇 |
1984年 | 11篇 |
1983年 | 17篇 |
1982年 | 10篇 |
1981年 | 14篇 |
1980年 | 17篇 |
1979年 | 10篇 |
1978年 | 11篇 |
1977年 | 15篇 |
1976年 | 12篇 |
1974年 | 15篇 |
1972年 | 9篇 |
排序方式: 共有3043条查询结果,搜索用时 31 毫秒
91.
Carolin Kaiser Johannes Kröckel Freimut Bodendorf 《Information Systems and E-Business Management》2013,11(4):597-621
An increasing number of people are joining online social networks. By interacting with each other, network members influence one another’s opinion. These influencing effects can be utilized by marketing. A wave of influence can be triggered by addressing only a few opinion leaders in the network. Targeting the right opinion leaders is a big challenge. This paper presents a new approach which simulates the spread of opinions when influencing certain opinion leaders. In contrast to other approaches, the influencing effects are not assumed but revealed by real data. The principles of opinion formation are detected by ant mining algorithms before they are applied to simulate the spread of opinions. The approach is applied to an online gaming community and provides valuable insights for marketing. 相似文献
92.
Relative deprivation and energy poverty: when does unequal access to electricity cause dissatisfaction? 下载免费PDF全文
In the least developed countries, unequal access to infrastructure is a major form of inequality. We examine the conditions under which unequal electricity access causes dissatisfaction. The question is important because grievances could prompt demands for policy change. We argue that feelings of relative deprivation both cause dissatisfaction and create hope for improvement. Empirically, we analyze household survey data from five East African countries. All else constant, households living close to a power line are less satisfied with their lighting solution but also have more hope for improvement. Because household lighting is the most important use for electricity in a poor household, this supports the relative deprivation hypothesis. Households that are reminded of their deprivation by the power line are both less satisfied and believe something can be done to solve the problem. To inform policy, we also show that the proximity of a power line decreases the household's interest in solar home systems as an alternative to grid electrification, whereas valuation for solar lanterns seems to be increasing. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
93.
Maria Smolle Stefan Uranitsch Armin Gerger Martin Pichler Johannes Haybaeck 《International journal of molecular sciences》2014,15(8):13993-14013
The latest investigations of long non-coding RNAs (lncRNAs) have revealed their important role in human cancers. LncRNAs are larger than 200 nucleotides in length and fulfill their cellular purpose without being translated into proteins. Though the molecular functions of some lncRNAs have been elucidated, there is still a high number of lncRNAs with unknown or controversial functions. In this review, we provide an overview of different lncRNAs and their role in human cancers. In particular, we emphasize their importance in tumorigenesis of colorectal cancer, the third most common cancer worldwide. 相似文献
94.
95.
Daniel Ritzberger Johannes Höflinger Zhang Peng Du Christoph Hametner Stefan Jakubek 《International Journal of Hydrogen Energy》2021,46(21):11878-11893
In order to mitigate the degradation and prolong the lifetime of polymer electrolyte membrane fuel cells, advanced, model-based control strategies are becoming indispensable. Thereby, the availability of accurate yet computationally efficient fuel cell models is of crucial importance. Associated with this is the need to efficiently parameterize a given model to a concise and cost-effective experimental data set. A challenging task due to the large number of unknown parameters and the resulting complex optimization problem. In this work, a parameterization scheme based on the simultaneous estimation of multiple structured state space models, obtained by analytic linearization of a candidate fuel cell stack model, is proposed. These local linear models have the advantage of high computational efficiency, regaining the desired flexibility required for the typically iterative task of model parameterization. Due to the analytic derivation of the local linear models, the relation to the original parameters of the non-linear model is retained. Furthermore, the local linear models enable a straight-forward parameter significance and identifiability analysis with respect to experimental data. The proposed method is demonstrated using experimental data from a 30 kW commercial polymer electrolyte membrane fuel cell stack. 相似文献
96.
97.
98.
Plasmaprimer — functional coatings for adhesion improvement When replacing solvent based paint or adhesion promoter partly new production processes are necessary. Plasma enhanced chemical vapor deposition offers to change the surface characteristics of parts according to the necessities of the following application. At the same time improvements in adhesion, in handling and environmental compatibility can be achieved. In this article an according production method is described and perspectives of new developments are shown. 相似文献
99.
Jan Penckwitt Robert van Geldern Burkard Hagspiel Birgit Packebusch Alexander Mahr Klaus Burkhardt Johannes A. C. Barth 《Grundwasser》2016,21(3):217-225
Infiltration of groundwater into sewer systems increases the costs for wastewater treatment plant operators. This study explores groundwater infiltration to urban sewer systems in the city of Nuremberg (Germany). Measurements of stable isotopes at the water works, storage tanks, groundwater, and the sewage network were carried out to define input end members for mass balance calculations. Only minor differences in oxygen stable isotopes (δ18OH2O) were found between most sewer and drinking water samples which ranged around (??9.5?±?0.1) ‰. One exception was water from a water works at Genderkingen that is situated about 80 km south of Nuremberg. Here, drinking water from bank filtrate of the Lech River had more negative δ18OH2O values of ??11.4?‰. This difference of 1.5?‰ revealed maximum possible groundwater contributions of 41?% by mass balance calculations. To obtain more accurate results, we suggest testing the use of deuterium-enriched water (D2O) added to the sewer system. 相似文献
100.