全文获取类型
收费全文 | 2291篇 |
免费 | 145篇 |
国内免费 | 2篇 |
学科分类
工业技术 | 2438篇 |
出版年
2022年 | 29篇 |
2021年 | 48篇 |
2020年 | 32篇 |
2019年 | 44篇 |
2018年 | 50篇 |
2017年 | 66篇 |
2016年 | 67篇 |
2015年 | 76篇 |
2014年 | 88篇 |
2013年 | 131篇 |
2012年 | 110篇 |
2011年 | 165篇 |
2010年 | 103篇 |
2009年 | 105篇 |
2008年 | 123篇 |
2007年 | 110篇 |
2006年 | 101篇 |
2005年 | 79篇 |
2004年 | 59篇 |
2003年 | 63篇 |
2002年 | 42篇 |
2001年 | 41篇 |
2000年 | 43篇 |
1999年 | 40篇 |
1998年 | 50篇 |
1997年 | 41篇 |
1996年 | 42篇 |
1995年 | 33篇 |
1994年 | 21篇 |
1993年 | 30篇 |
1992年 | 23篇 |
1991年 | 21篇 |
1990年 | 17篇 |
1989年 | 22篇 |
1988年 | 18篇 |
1987年 | 12篇 |
1986年 | 25篇 |
1985年 | 20篇 |
1984年 | 20篇 |
1983年 | 16篇 |
1982年 | 13篇 |
1981年 | 18篇 |
1980年 | 13篇 |
1979年 | 19篇 |
1978年 | 20篇 |
1977年 | 17篇 |
1976年 | 15篇 |
1974年 | 12篇 |
1973年 | 11篇 |
1970年 | 10篇 |
排序方式: 共有2438条查询结果,搜索用时 15 毫秒
111.
Busarakorn Mahayothee Nilobon Komonsing Pramote Khuwijitjaru Marcus Nagle Joachim Müller 《International Journal of Food Science & Technology》2019,54(2):460-470
In this study, drying of red-fleshed dragon fruit at different temperatures (40, 50, 60, 70 and 80 °C) and air velocities (1.0 and 1.5 m s−1) was conducted under the specific humidity of 25 g H2O kg−1 dry air. The results showed that drying at higher temperatures resulted in shorter drying times. However, temperature and air velocity did not significantly affect the total betacyanin contents and antioxidant capacities in dried products. Seven betacyanins identified by LC-MS were betanin, isobetanin, phyllocactin, isophyllocactin, betanidin 5 –O-(6′O-3-hydroxybutyryl)-β-glucoside, isobetanidin 5 –O-(6′O-3-hydroxybutyryl)-β-glucoside and decarboxylated phyllocactin. In addition, the temperature increased the isomerisation of betacyanins. The most preferable condition for preserving the colour and betacyanin contents of red-fleshed dragon fruit was the drying at a temperature of 80 °C and air velocity of 1.5 m s−1 since it could shorten the drying time and give a bright red colour to the dried product as well as it had no significant impact on the betacyanins. 相似文献
112.
Hsu MT Knittel J Morizur JF Bachor HA Bowen WP 《Journal of the Optical Society of America. A, Optics, image science, and vision》2010,27(12):2583-2587
We present an experimental demonstration of an optical pattern recognition scheme based on spatial homodyne detection. Our scheme is adaptive, all-optical, utilizes a single-element photo-detector, and provides a single parameter readout to quantify the efficacy of pattern recognition, thereby allowing very fast pattern recognition speeds. The spatial homodyne detector was applied to the identification of one- and two-dimensional phase profiles. 相似文献
113.
114.
L.N.S.A. Thummalakunta Chian Haw YongKrishnamoorthy Ananthanarayanan Joachim Luther 《Organic Electronics》2012,13(10):2008-2016
We present a solution-processed pseudo bi-layer organic solar cell with poly(3-hexyl thiophene) (P3HT) as donor and indene-C60 bisadduct (ICBA) as acceptor. The devices were fabricated by sequential processing of the active components followed by a thermal annealing treatment. An efficiency of 5.9% was achieved under AM 1.5G irradiation (1000 W/m2). The obtained efficiency is attributed to an enhanced nanomorphology that arises from the inter-diffusion of the ICBA molecules into a layer of pre-organised polymer (P3HT) and also due to the subsequent crystallisation of the ICBA molecules. These processes facilitate efficient charge generation and extraction. Time of flight-secondary ion mass spectroscopy (TOF-SIMS) depth profiling was carried out for different thermal annealing treatments of these pseudo bi-layer devices, which reveals full inter-diffusion of ICBA into the polymer P3HT. Photo-CELIV (charge extraction by linearly increasing voltage) studies elucidates that the thermal annealing imparts crystallinity to the fullerene phase which results in the improvement of charge carrier mobility. 相似文献
115.
Svetlana S. van Bavel Maik Bärenklau Gijsbertus de With Harald Hoppe Joachim Loos 《Advanced functional materials》2010,20(9):1458-1463
The performance of polymer solar cells (PSC) strongly depends on the 3D morphological organization of the donor and acceptor compounds within the bulk heterojunction active layer. The technique of electron tomography is a powerful tool for studying 3D morphology of the layers composed of poly(3‐hexylthiophene) (P3HT) and a fullerene derivative ([6,6]‐phenyl‐C61‐butyric acid methyl ester; PCBM), especially to quantify the amount and distribution of fibrillar P3HT nanocrystals throughout the volume of the active layer. In this study, electron tomography is used to characterize P3HT/PCBM layers with different blend compositions, both before and after thermal annealing. The power conversion efficiency of the corresponding PSCs is strongly dependent on the overall crystallinity of P3HT and the way P3HT crystals are distributed throughout the thickness of the active layer. 相似文献
116.
This paper contributes to empirical research on the role of regional policy for entrepreneurship by focusing on the link between two stylized facts that emerged from a number of studies for Germany and other countries: Entry rates differ between regions, and the propensity to become an entrepreneur is influenced by socio-demographic variables and attitudes. We develop a theoretical framework to discuss this link, and we test whether for a person of a given age, degree of schooling, attitude towards risk etc. regional variables and, therefore, regional policies, do matter for the decision to start a new business ceteris paribus. Our econometric study is based on data for 10.000 persons from a recent representative survey of the population in ten German planning regions, the Regional Entrepreneurship Monitor (REM). We use a version of the probit model that takes care of the regional stratification of the data, and the results of the nonlinear models are carefully interpreted and illustrated. We find that the propensity to step into self-employment is, among others, higher for males, unemployed, people with contacts to a role model, and with past entrepreneurial experience, who live in more densely populated and faster growing regions with higher rates of new firm formation, while risk aversion and high prices of land have the opposite impact. Interestingly, it does not matter whether the region has a left or right government. However, many implications for entrepreneurship supporting policies in German regions are discussed in the final section.Research for this paper was done as part of the project Regional Entrepreneurship Monitor REM Germany financially supported by the German Research Foundation (DFG STE 628/7-1/2 and WA 610/2-1/2). We thank two anonymous referees and the guest editors of this issue for comments that led to an extensive revision of an earlier version. 相似文献
117.
118.
In this contribution the problem of maximizing the efficiency of a hybrid power unit at a specified output power level by optimizing the generator current trajectory as well as the design variables that can be chosen during the machine design process is investigated. The concept is demonstrated based on a hybrid single-cylinder diesel engine that is coupled to an electric generator. By developing a model of the system and using open-loop optimal control the optimal operating strategy and the optimal machine design are determined. Besides that, the problems occurring in the application of this strategy to a test rig are discussed. For this purpose, a model-free real-time optimization concept based on extremum seeking control is presented. The effectiveness of both the model-based and the model-free concept are demonstrated by simulation and experimental results. 相似文献
119.
120.