全文获取类型
收费全文 | 2456篇 |
免费 | 142篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 25篇 |
综合类 | 1篇 |
化学工业 | 624篇 |
金属工艺 | 41篇 |
机械仪表 | 56篇 |
建筑科学 | 73篇 |
矿业工程 | 2篇 |
能源动力 | 101篇 |
轻工业 | 169篇 |
水利工程 | 9篇 |
石油天然气 | 4篇 |
无线电 | 282篇 |
一般工业技术 | 486篇 |
冶金工业 | 124篇 |
原子能技术 | 11篇 |
自动化技术 | 591篇 |
出版年
2024年 | 2篇 |
2023年 | 28篇 |
2022年 | 42篇 |
2021年 | 66篇 |
2020年 | 62篇 |
2019年 | 53篇 |
2018年 | 73篇 |
2017年 | 62篇 |
2016年 | 90篇 |
2015年 | 63篇 |
2014年 | 103篇 |
2013年 | 178篇 |
2012年 | 184篇 |
2011年 | 228篇 |
2010年 | 174篇 |
2009年 | 147篇 |
2008年 | 146篇 |
2007年 | 151篇 |
2006年 | 103篇 |
2005年 | 89篇 |
2004年 | 67篇 |
2003年 | 50篇 |
2002年 | 53篇 |
2001年 | 49篇 |
2000年 | 34篇 |
1999年 | 40篇 |
1998年 | 55篇 |
1997年 | 40篇 |
1996年 | 20篇 |
1995年 | 16篇 |
1994年 | 17篇 |
1993年 | 17篇 |
1992年 | 20篇 |
1991年 | 10篇 |
1990年 | 12篇 |
1989年 | 6篇 |
1988年 | 4篇 |
1987年 | 9篇 |
1986年 | 6篇 |
1985年 | 2篇 |
1984年 | 3篇 |
1983年 | 5篇 |
1982年 | 5篇 |
1979年 | 1篇 |
1978年 | 2篇 |
1977年 | 5篇 |
1976年 | 3篇 |
1975年 | 1篇 |
1970年 | 1篇 |
1956年 | 1篇 |
排序方式: 共有2599条查询结果,搜索用时 15 毫秒
211.
Intidhar Bouali Hajer Trabelsi Ikram Bou Abdallah Ali Albouchi Lucy Martine Stéphane Grégoire Ghaith Bouzaien Mhemmed Gandour Sadok Boukhchina Olivier Berdeaux 《Journal of the American Oil Chemists' Society》2013,90(12):1869-1876
Among oil compounds, fatty acids, tocopherols and xanthophylls (lutein and zeaxanthin) are of special interest due to their nutritional properties. The identification and quantification of these compounds in pecan nuts (Carya illinoinensis) could therefore be very useful to produce functional foods rich in compounds of this type. This paper reports studies on their accumulation and the effect of ripening on the content of these high value-added compounds. The total lipid content increased during the ripening. Saturated and polyunsaturated fatty acids decreased significantly, whereas, monounsaturated fatty acids increased during the ripening of pecan nut fruit. Maximum levels of total tocopherol (279.53 mg/kg oil) and xanthophyll (6.18 mg/kg oil) were detected at 20th weeks after the flowering date. These amounts decreased gradually as ripening advances. The early stages of pecan ripening seem to have nutritional and pharmaceutical interests. These results may be useful for evaluating the pecan nut quality and determining the optimal period when the pecans accumulated the maximum of these nutritional and healthy compounds. 相似文献
212.
Olivier Kaczor Yann-Gaël Guéhéneuc Sylvie Hamel 《Information and Software Technology》2010,52(2):152-168
Design patterns are important in software maintenance because they help in understanding and re-engineering systems. They propose design motifs, solutions to recurring design problems. The identification of occurrences of design motifs in large systems consists of identifying classes whose structure and organization match exactly or approximately the structure and organization of classes as suggested by the motif. We adapt two classical approximate string matching algorithms based on automata simulation and bit-vector processing to efficiently identify exact and approximate occurrences of motifs. We then carry out two case studies to show the performance, precision, and recall of our algorithms. In the first case study, we assess the performance of our algorithms on seven medium-to-large systems. In the second case study, we compare our approach with three existing approaches (an explanation-based constraint approach, a metric-enhanced explanation-based constraint approach, and a similarity scoring approach) by applying the algorithms on three small-to-medium size systems, JHotDraw, Juzzle, and QuickUML. Our studies show that approximate string matching based on bit-vector processing provides efficient algorithms to identify design motifs. 相似文献
213.
Laetitia Hédouin Olivier Pringault Paco BustamanteRenaud Fichez Michel Warnau 《Water research》2011,45(2):483-496
The bioaccumulation and retention capacities of some key local contaminants of the New Caledonia lagoon (Ag, As, Cd, Co, Cr, Cu, Mn, Ni and Zn) have been determined in the oyster Isognomon isognomon and the edible clam Gafrarium tumidum during transplantation experiments. In a first set of experiments, oysters and clams from a clean site were transplanted into contaminated sites. Uptake kinetics determined in the field indicated that for Cr and Cu in oysters and Co, Ni, and Zn in clams, concentrations in transplanted bivalves reached those of resident organisms after 100d, whereas for the other elements, it would require a longer time for transplanted bivalves to reach the same levels as in the resident populations (e.g., up to 3 years for Cd). However, the slow uptake rate for metals observed in the latter transplantation is rather related to low bioavailability of metals at the contaminated sites than to low bioaccumulation efficiency of the organisms. Indeed, results of a second transplantation experiment into two highly contaminated stations indicated a faster bioaccumulation of metals in both bivalves. Results of both transplantations point out that the clam G. tumidum is a more effective bioindicator of mining contamination than I. isognomon, since it is able to bioaccumulate the contaminants to a greater extent. However the very efficient metal retention capacity noted for most elements indicates that organisms originating from contaminated sites would not be suitable for monitoring areas of lower contamination. Hence, geographical origin of animals to be transplanted in a monitoring perspective should be carefully selected. 相似文献
214.
Etienne Videcoq Olivier Quemener Myriam Lazard Alain Neveu 《International Journal of Heat and Mass Transfer》2008,51(19-20):4743-4752
This paper presents the advantages of a Branch Eigenmodes Reduced Model used in a control process of a heating system.The experimental setup is a 3D heat conductive system in which a heat source is set. First, the reduced model is used to solve the non-linear Inverse Heat Conduction Problem: identification of the heat source strength variations from time-varying temperatures. Then, the reduced model is used to control hot points in the system. The objective of the method is to allow sequential temperature control by decreasing the computation time necessary for the simulation. 相似文献
215.
Perrin Francois Bertrand Olivier Pernier Jacques 《IEEE transactions on bio-medical engineering》1987,(4):283-288
Scalp current density (SCD) makes possible the identification of scalp sources and sinks of current. SCD is reference independent and its peaks and troughs are sharper than those of the scalp potential (SP). SCD, by comparison to SP, reflects mainly the activity of cortical generators. SCD mapping appears to be a valuable tool to spatially split smeared SP distribution due to simultaneously active generators. The SCD map may be computed from any sufficiently smooth mathematical SP map. An evaluation of the error of SCD estimation is given for a surface spline method of interpolation of SP. An example of the simultaneous use of SP and SCD in the analysis of somatosensory evoked data is given. 相似文献
216.
Brosson P. Labourie C. Le Gouezigou L. Lievin J.L. Jacquet J. Leblond F. Olivier A. Leclerc D. 《Electronics letters》1989,25(24):1623-1624
Measurements of threshold current density and external efficiency on broad-area laser-waveguide structure have led to the determination of the optical loss and differential loss d alpha /dN approximately=1.1-2.3 *10/sup -17/ cm/sup 2/ at lambda =1.53 mu m in a lambda /sub g/=1.30 mu m GaInAsP layer. This measurement will be useful for the design of tunable lasers.<> 相似文献
217.
Gaëtan Rimmelé Véronique Barlet-Gouédard Olivier Porcherie Bruno Goffé Fabrice Brunet 《Cement and Concrete Research》2008,38(8-9):1038-1048
Efficient and safe storage of injected supercritical carbon dioxide (CO2) underground is now one potential solution for reducing CO2 emissions in the atmosphere. Preventing any CO2 leakage through a wellbore annulus after injection is a key to maintaining long-term wellbore integrity. Most wells in depleted oil and gas fields may be re-used to inject CO2. These wells were mostly cemented with conventional Portland cement. It is thus crucial to study how such cement behaves at depth in CO2-rich fluids.Set cement samples are exposed to CO2 fluids under pressure and temperature to simulate downhole conditions. The degraded cement exhibits significant mineralogical changes and heterogeneous porosity distribution. The bulk porosity evolution, as well as local porosity gradients through the samples, is quantified using combined mercury porosimetry and back-scattered electron image analysis. Both techniques show an initial sealing stage related to calcium carbonate precipitation plugging the porosity, followed by a dissolution stage marked by a significant increase of porosity. 相似文献
218.
We present a numerical simulation for the blow molding of an industrial high density polyethylene part. The rheology of the polymeric material is described by means of an integral viscoelastic fluid model with a multi-mode relaxation spectrum. A membrane element is applied for performing the blow molding simulation of geometrically complex objects such as a bottle with a handle; the motion governing equations are described by means of a Lagrangian representation. The contact between the parison and the moving mold is handled by means of a robust algorithm. The numerical tool is applied for the production of a bottle with a handle. The predicted results are compared with their experimental counterparts. In particular, we focus on the thickness distribution of the blow product. 相似文献
219.
Michail Vlachos Aris Anagnostopoulos Olivier Verscheure Philip S. Yu 《The VLDB Journal The International Journal on Very Large Data Bases》2009,18(1):77-98
This paper answers the following question; given a multiplicity of evolving 1-way conversations, can a machine or an algorithm discern the conversational pairs in an online fashion, without understanding the content of the communications? Our analysis indicates that this is possible, and can be achieved just by exploiting the temporal dynamics inherent in a conversation. We also show that our findings are applicable for anonymous and encrypted conversations over VoIP networks. We achieve this by exploiting the aperiodic inter-departure time of VoIP packets, hence trivializing each VoIP stream into a binary time-series, indicating the voice activity of each stream. We propose effective techniques that progressively pair conversing parties with high accuracy and in a limited amount of time. Our findings are verified empirically on a dataset consisting of 1,000 conversations. We obtain very high pairing accuracy that reaches 97% after 5 min of voice conversations. Using a modeling approach we also demonstrate analytically that our result can be extended over an unlimited number of conversations. 相似文献
220.
Jean-Paul Mazellier Olivier Faynot Sorin Cristoloveanu Simon Deleonibus Philippe Bergonzo 《Diamond and Related Materials》2008,17(7-10):1248-1251
We examine here by electro-thermal simulation tools (SILVACO's Atlas) a configuration of Silicon-On-Insulator substrate for Fully-Depleted MOSFET architectures, incorporating diamond as buried insulator, and compare it with traditional silicon dioxide BOX for the future technological nodes of the ITRS (90 nm and below). Our aim is to give major trends to be followed in order to optimize diamond integration from electrical and thermal points of view, constraints that must be kept in mind in parallel with the technological work on thin diamond films. In this theoretical study, we perform a benchmarking between SiO2 and diamond BOX. We first point out that the BOX thickness should not be more than few hundred nanometers to maintain electrical performances. From thermal point of view, we demonstrate that the replacement of 100 nm thick buried oxide by a 100 nm thick diamond layer can lead to about 50% reduction of the temperature when only 33% decrease can be obtained with Ultra Thin SiO2 BOX (20 nm). Furthermore, thick diamond BOX avoids the parasitic capacitances issue that reduces Ultra Thin BOX devices working frequency. 相似文献