全文获取类型
收费全文 | 1606篇 |
免费 | 50篇 |
国内免费 | 10篇 |
专业分类
电工技术 | 13篇 |
综合类 | 1篇 |
化学工业 | 480篇 |
金属工艺 | 35篇 |
机械仪表 | 9篇 |
建筑科学 | 63篇 |
矿业工程 | 2篇 |
能源动力 | 32篇 |
轻工业 | 172篇 |
水利工程 | 10篇 |
石油天然气 | 8篇 |
无线电 | 166篇 |
一般工业技术 | 306篇 |
冶金工业 | 144篇 |
原子能技术 | 13篇 |
自动化技术 | 212篇 |
出版年
2023年 | 8篇 |
2022年 | 12篇 |
2021年 | 19篇 |
2020年 | 10篇 |
2019年 | 13篇 |
2018年 | 19篇 |
2017年 | 25篇 |
2016年 | 26篇 |
2015年 | 27篇 |
2014年 | 41篇 |
2013年 | 88篇 |
2012年 | 59篇 |
2011年 | 98篇 |
2010年 | 68篇 |
2009年 | 70篇 |
2008年 | 90篇 |
2007年 | 64篇 |
2006年 | 72篇 |
2005年 | 50篇 |
2004年 | 65篇 |
2003年 | 54篇 |
2002年 | 69篇 |
2001年 | 32篇 |
2000年 | 32篇 |
1999年 | 36篇 |
1998年 | 32篇 |
1997年 | 20篇 |
1996年 | 25篇 |
1995年 | 24篇 |
1994年 | 26篇 |
1993年 | 24篇 |
1992年 | 24篇 |
1991年 | 16篇 |
1990年 | 18篇 |
1989年 | 23篇 |
1988年 | 19篇 |
1987年 | 15篇 |
1986年 | 16篇 |
1985年 | 30篇 |
1984年 | 13篇 |
1983年 | 23篇 |
1982年 | 14篇 |
1981年 | 13篇 |
1980年 | 19篇 |
1979年 | 18篇 |
1978年 | 15篇 |
1976年 | 16篇 |
1975年 | 20篇 |
1974年 | 10篇 |
1966年 | 7篇 |
排序方式: 共有1666条查询结果,搜索用时 10 毫秒
991.
Pesticide residues survey in citrus fruits 总被引:3,自引:0,他引:3
The use of pesticides is widespread in citrus fruits production for pre- and post-harvest protection and many chemical substances may be applied in order to control undesirable moulds or insects. A survey was carried out to evaluate levels of pesticide residues in citrus fruits. Two multiresidue analytical methods were used to screen samples for more than 200 different fungicides, insecticides and acaricides. A total of 240 samples of citrus fruits including lemon, orange, mandarin, grapefruit, lime, pomelo and kumquat were taken in various markets in the Geneva area during the year 2003. Ninety-five percent of the 164 samples issued from classical agriculture contained pesticides and 38 different compounds have been identified. This high percentage of positive samples was mainly due to the presence of two post-harvest fungicides, imazalil and thiabendazole, detected in 70% and 36% of samples respectively. Only three samples exceeded the Swiss maximum residue limits (MRLs). Fifty-three samples sold with the written indication “without post-harvest treatment” were also controlled. Among theses samples, three exceeded the Swiss MRLs for penconazole or chlorpyrifos and 18 (34%) did not respect the written indication since we found large amounts of post-harvest fungicides. Finally, 23 samples coming from certified organic production were analysed. Among theses samples, three contained small amounts of pesticides and the others were pesticides free. 相似文献
992.
Substantial Variability Across Individuals in the Vascular and Nutrigenomic Response to an Acute Intake of Curcumin: A Randomized Controlled Trial 下载免费PDF全文
993.
Milena Popova Boryana Trusheva Daniela Antonova Simone Cutajar David Mifsud Claude Farrugia Iva Tsvetkova Hristo Najdenski Vassya Bankova 《Food chemistry》2011
Seventeen Maltese propolis samples were studied by GC–MS after silylation. They exhibited the typical Mediterranean chemical profile, rich in diterpene compounds (18–92% of TIC, GC–MS): 32 individual diterpenes were identified; 22 of them were present in each specimen. The other abundant compound group was that of sugars and sugar derivatives. In some samples, however, another compound group was observed (0–12% of TIC, GC–MS); the corresponding mass spectra were consistent with mono- and sesquiterpenyl esters of substituted benzoic acids. Two new propolis constituents of this group, daucane diterpene esters of hydroxybenzoic acids, were isolated. Their origin is suggested to be Ferula communis, as they are taxonomic markers for this species. All propolis samples were active against Staphylococcus aureus but only those with high concentrations of terpenyl esters showed antifungal activity against Candida albicans. The present results confirm that Mediterranean propolis is a valuable natural product with potential to improve human health. 相似文献
994.
Claude P. Champagne Nancy Gardner Michel Piette Daniel St-Gelais 《International Dairy Journal》1994,4(8):789-795
Petrifilm™ aerobic plate counts were compared to Elliker and M17 agar counts for the enumeration of Lactococcus strains. There were no significant differences between counts obtained with the three methods, which suggests that Petrifilm™ plates can be used as a time-saving method for the determination of lactococci starter populations. The standard method of using Petrifilm™, in which 1 ml of sample is analysed, can be modified to have multiple inoculations on the same dry medium culture plates, such that four aliquots of 0·1 ml are added to a single Petrifilm™ plate. Counts obtained with the multiple inoculation method did not differ significantly from the standard single inoculation method recommended by the Petrifilm™ manufacturer. 相似文献
995.
Picart L Thiebaud M René M Pierre Guiraud J Cheftel JC Dumay E 《The Journal of dairy research》2006,73(4):454-463
Raw whole milk of high microbial quality (58 degrees C), but markedly decreased above 200 MPa when Tin=24 degrees C (T2>60 degrees C). In contrast to inactivation induced by continuous short-time thermal treatments, ALP inactivation induced by HP homogenisation was clearly due to mechanical forces (shear, cavitation and/or impact) in the HP valve and not to the short (<1 s) residence time at temperature T2 in the same valve. Inactivation of the three exogenous microorganisms led to similar conclusions. Homogenisation at 250 MPa or 300 MPa (Tin=24 degrees C) induced a 2-3 log cycle reduction of the total endogenous milk flora and a 1.5-1.8 log cycle reduction of inoculated List. innocua. Higher reduction ratios (2-4 log cycles) were obtained for the two other microorganisms. The highest levels of ALP inactivation corresponded to the highest extents of microbial reduction. Running the milk twice or three times through the homogeniser (recycling), keeping temperature T1 approximately 29 degrees C and pressure=200 MPa, increased homogenisation efficiency. 相似文献
996.
997.
Stéphane Claude Pat Niranjanan Frank Jiang Dave Duncan Dominic Garcia Mark Halman Haoling Ma Ivan Wevers Keith Yeung 《Journal of Infrared, Millimeter and Terahertz Waves》2014,35(6-7):563-582
This paper presents the performance of production Band 3 receivers (84-116 GHz) for the Atacama Large Millimeter Array (ALMA) that operate in Chile at 5000 m altitude. The fabrication, and testing of a total of 73 receivers necessitated stringent quality control during assembly and custom designed automated test set for accurate and reproducible measurement results. Interfaces to the ALMA receiver system are described in details. The average single side band noise temperature of band 3 production receivers is 33.2 K, with a minimum of 24.4 K and a maximum of 45.5 K. As for image rejection, the average is 18 dB, with a minimum at 12 dB and a maximum of 21 dB. Other performances with test methodology are described such as gain variation within the IF band, the gain and phase stability, gain compression, and beam patterns. This paper also describes the interfaces to the ALMA front end system, the testing methodology used, and the test results. 相似文献
998.
Hélène Barberousse Olivier Roiseux Christelle Robert Michel Paquot Claude Deroanne Christophe Blecker 《Journal of the science of food and agriculture》2008,88(9):1494-1511
Ferulic acid (4‐hydroxy‐3‐methoxycinnamic acid) is the most widespread hydroxycinnamic acid in the plant world, where it is a key molecule in cell wall architecture. Owing to its high antioxidant properties, ferulic acid shows large potential applications in food industry as well as in the health and cosmetic markets. There is thus a high interest in extracting this high‐value compound from waste materials of the agricultural industry, which requires the selection of an appropriate quantification method. This paper therefore gives an overview of analytical methodologies developed over past decades for quantification of ferulic acid and its oligomers. Copyright © 2008 Society of Chemical Industry 相似文献
999.
Alain BarthéLémy Bernard Colombeau Claude Froehly Laurent Lefort Stephane Ménard Michel vampouille 《电信纪事》1997,52(11-12):569-574
The basic principles of new ultrafast all-optical processing devices are experimentally demonstrated. One type of device relies on the interaction between an input signal and two colliding spatial solitons of a different wavelength in a planar waveguide with third order nonlinearity. The devices which belong to the second type are based on second order nonlinear interactions (degenerate difference frequency mixing) and operate as ultrafast sampling gate or as deflector or as phase conjugator. We report in a second part the design and performances of a laser that could be used to trigger the above mentionned systems. The laser cavity has two arms and two separate diode-pumped laser crystals (Nd/YAG). The two laser beams are coherently recombined inside the resonator into a single Gaussian beam. Picosecond pulses emission is ensured by passive mode-locking thanks to a nonlinear mirror set-up. 相似文献
1000.
Claude Thibeault 《Journal of Electronic Testing》2000,16(4):339-353
This paper presents a diagnostic method based on differential IDDQprobabilistic signatures, inspired by telecommunications systems. The method and its unique features are described. Then, results from an IC monitor containing controllable faults show the capability of the method to diagnose actual activated faults, despite a strong experimental current standard variation. These results validate previous simulation procedures, which are applied to quantify effects not covered by the monitor experiment, that is, the effect of the load of a bridged node and the effect of the bridge resistance value. These experimental and simulation results reveal the robustness of the proposed diagnosis method, that has identified and located every single fault considered so far. 相似文献