全文获取类型
收费全文 | 2417篇 |
免费 | 114篇 |
国内免费 | 5篇 |
专业分类
电工技术 | 40篇 |
综合类 | 9篇 |
化学工业 | 695篇 |
金属工艺 | 44篇 |
机械仪表 | 61篇 |
建筑科学 | 125篇 |
矿业工程 | 9篇 |
能源动力 | 81篇 |
轻工业 | 224篇 |
水利工程 | 20篇 |
石油天然气 | 8篇 |
无线电 | 194篇 |
一般工业技术 | 418篇 |
冶金工业 | 212篇 |
原子能技术 | 23篇 |
自动化技术 | 373篇 |
出版年
2023年 | 28篇 |
2022年 | 41篇 |
2021年 | 47篇 |
2020年 | 36篇 |
2019年 | 49篇 |
2018年 | 56篇 |
2017年 | 56篇 |
2016年 | 77篇 |
2015年 | 72篇 |
2014年 | 85篇 |
2013年 | 123篇 |
2012年 | 107篇 |
2011年 | 152篇 |
2010年 | 115篇 |
2009年 | 106篇 |
2008年 | 123篇 |
2007年 | 109篇 |
2006年 | 82篇 |
2005年 | 84篇 |
2004年 | 66篇 |
2003年 | 72篇 |
2002年 | 57篇 |
2001年 | 41篇 |
2000年 | 34篇 |
1999年 | 45篇 |
1998年 | 67篇 |
1997年 | 39篇 |
1996年 | 38篇 |
1995年 | 36篇 |
1994年 | 33篇 |
1993年 | 35篇 |
1992年 | 26篇 |
1991年 | 24篇 |
1990年 | 24篇 |
1989年 | 25篇 |
1988年 | 14篇 |
1987年 | 16篇 |
1986年 | 24篇 |
1985年 | 25篇 |
1984年 | 21篇 |
1983年 | 15篇 |
1982年 | 13篇 |
1981年 | 14篇 |
1980年 | 16篇 |
1979年 | 12篇 |
1978年 | 17篇 |
1977年 | 12篇 |
1976年 | 22篇 |
1975年 | 14篇 |
1974年 | 20篇 |
排序方式: 共有2536条查询结果,搜索用时 15 毫秒
41.
Modelling water dynamics with DNDC and DAISY in a soil of the North China Plain: A comparative study
Roland Kröbel Qinping Sun Joachim Ingwersen Xinping Chen Fusuo Zhang Torsten Müller Volker Römheld 《Environmental Modelling & Software》2010,25(4):583-601
The performance of the DNDC and Daisy model to simulate the water dynamics in a floodplain soil of the North China Plain was tested and compared. While the DNDC model uses a simple cascade approach, the Daisy model applies the physically based Richard's equation for simulating water movement in soil. For model testing a three years record of the soil water content from the Dong Bei Wang experimental station near Beijing was used. There, the effect of nitrogen fertilization, irrigation and straw removal on soil water and nitrogen dynamics was investigated in a three factorial field experiment applying a split-split-plot design with 4 replications. The dataset of one treatment was used for model testing and calibration. Two other independent datasets from further treatments were employed for validating the models. For both models, the simulation results were not satisfying using default parameters. After parameter optimisation and the use of site-specific van Genuchten parameters, however, the Daisy model performed well. But, for the DNDC model, parameter optimisation failed to improve the simulation result. Owing to the fact that many biological processes such as plant growth, nitrification or denitrification depend strongly on the soil water content, our findings bring us to the conclusion that the site-specific suitability of the DNDC model for simulating the soil water dynamics should be tested before further simulation of other processes. 相似文献
42.
Hao Fang Lihua DouJie Chen Roland LenainBenoit Thuilot Philippe Martinet 《Control Engineering Practice》2011,19(5):468-478
Path following control problem of autonomous vehicles is investigated, concerning both unmeasurable sliding effects and lateral disturbances which lead to some difficulties in designing autonomous control under complex environment. To deal with the sliding effects, sideslip angles are modeled and reconstructed by estimating the tire cornering stiffness, which plays important role in analyzing the sliding effects. To this end, a Luenberger-type observer is designed, which is able to identify the tire cornering stiffness adaptively even in presence of time-varying lateral disturbances. Furthermore, to guarantee high-precision guidance, a sliding mode controller is designed based on chained system theory, and this controller is shown to be robust to both the lateral disturbances and the inaccuracy of the sliding reconstruction. Simulations illustrate that the proposed methods can reconstruct the sliding angles and provide high-accuracy anti-sliding control even in presence of the time-varying lateral disturbances. 相似文献
43.
Christoph Bosshard Roland Bouffanais Michel Deville Ralf Gruber Jonas Latt 《Computers & Fluids》2011,44(1):1-8
In this paper, a comprehensive performance review of an MPI-based high-order three-dimensional spectral element method C++ toolbox is presented. The focus is put on the performance evaluation of several aspects with a particular emphasis on the parallel efficiency. The performance evaluation is analyzed with the help of a time prediction model based on a parameterization of the application and the hardware resources. Two tailor-made benchmark cases in computational fluid dynamics (CFD) are introduced and used to carry out this review, stressing the particular interest for clusters with up to thousands of cores. Some problems in the parallel implementation have been detected and corrected. The theoretical complexities with respect to the number of elements, to the polynomial degree, and to communication needs are correctly reproduced. It is concluded that this type of code has a nearly perfect speedup on machines with thousands of cores, and is ready to make the step to next-generation petaFLOP machines. 相似文献
44.
Roland H. C. Yap 《Constraints》2001,6(2-3):157-172
Approximate matching techniques based on string alignment are important tools for investigating similarities between strings, such as those representing DNA and protein sequences. We propose a constraint based approach for parametric sequence alignment which allows for more general string alignment queries where the alignment cost can itself be parameterized as a query with some initial constraints. Thus, the costs need not be fixed in a parametric alignment query unlike the case in normal alignment. The basic dynamic programming string edit distance algorithm is generalized to a naive algorithm which uses inequalities to represent the alignment score. The naive algorithm is rather costly and the remainder of the paper develops an improvement which prunes alternatives where it can and approximates the alternatives otherwise. This reduces the number of inequalities significantly and strengthens the constraint representation with equalities. We present some preliminary results using parametric alignment on some general alignment queries. 相似文献
45.
A positive and innovative organizational climate is of great importance in order to manage and adapt to change. Such a climate seldom evolves in organizations closely governed by rules and regulations. Because of ongoing organizational and technical changes within the Swedish Air Navigation Services Provider, a study concerning the organizational climate for changes and innovations was conducted to investigate the organization's capacity to cope with changes. Study locations were the two Swedish main air traffic control centers and parts of the civil aviation administration headquarters. In the study 390 subjects took part and the CCQ questionnaire was used to measure the organizational climate. The results show that the organizational climate is quite positive despite the rule-governed work. The results also show that administrative personnel assess the organizational climate as more positive than operative personnel. Comparisons between management positions did not result in any differences. 相似文献
46.
Pradeep K. Nalla Roland J. Weiss Prakash Peranandam Jürgen Ruf Thomas Kropf Wolfgang Rosenstiel 《Electronic Notes in Theoretical Computer Science》2006,135(2):47
In this paper we describe an algorithm for distributed, BDD-based bounded property checking and its implementation in the verification tool SymC. The distributed algorithm verifies larger models and returns results faster than the sequential version.The core algorithm distributes partitions of the state set to computation nodes after reaching a threshold size. The nodes proceed with image computation on the nodes asynchronously. The main scalability problem of this scheme is the overlap of state set partitions. We present static and dynamic overlap reduction techniques. 相似文献
47.
Roland Gerber 《电信纪事》1983,38(9-10):367-379
48.
49.
Bernd Altmayer Klaus W. Eichhorn und Roland Plapp 《Zeitschrift für Lebensmitteluntersuchung und -Forschung A》1982,175(3):172-174
Zusammenfassung Traubenmoste aus dem Weinanbaugebiet der Rheinpfalz wurden auf ihren Patulingehalt untersucht. Nach Extraktion und Reinigung wurde Patulin mit Hilfe der Hochleistungsflilssig- und Dünnschichtchromatographie bestimmt. Zur Extraktion des Patulins erwies sich die Verwendung von Extrelutsdulen als vorteilhaft. In 62% der untersuchten Proben (55) war kein Patulin nachweisbar, 22% enthielten weniger als 50 g, 16% mehr als 50 g Patulin pro Liter. Durch praxisübliche Mostschwefelung (100 mg Kaliumpyrosulîit/1) und Vergärung mit Hefen der GattungSaccharomyces konnte vorhandenes Patulin entfernt werden.
Analysis of patulin in grape juices and wine
Summary Grape juices from the wine-growing region of the palatinate Rheinpfalz were analysed for patulin. After extraction and purification patulin was determined by high performance liquid chromatography and thin layer chromatography. The use of Extrelut-columns for the extraction of patulin was found advantageous. 62% of the analysed samples (55) were free of patulin, 22% contained less than 50 g/l, 16% more than 50 g/l. By addition of sulfur dioxide to the must and fermentation withSaccharomyces sp. patulin could be removed from the samples.相似文献
50.
Christian Pruner Martin Fally Romano A. Rupp Roland P. May Jürgen Vollbrandt 《Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment》2006,560(2):598-605
Design and setup of an interferometer for cold and ultracold neutrons are described. As neutron optical components three holographically produced gratings are arranged in triple Laue geometry. The gratings are adjusted during their recording process in photosensitized polymer slabs once for ever. Employing this device we measured the coherence function of a cold neutron beam by means of interferometry. 相似文献