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101.
Long-term impact of chronosequential land use change on soil carbon stocks on a Swedish farm 总被引:1,自引:0,他引:1
Thomas K?tterer Liselotte Andersson Olof Andrén Jan Persson 《Nutrient Cycling in Agroecosystems》2008,81(2):145-155
Agricultural practices and land use significantly influence soil carbon storage. The processes that are affected by land use
and management are generally understood, but uncertainties in projections are high. In this paper, we investigate the long-term
effects of chronosequential land use change from grassland to cropland and vice versa on soil carbon stock dynamics in four fields on a Swedish farm. Between 1850 and 1920, three of the fields were converted
from grassland into cropland, and one was converted back to grassland in 1971. The fourth (control) field is a grassland that
has never been ploughed. In 1937, the four fields were sampled at 111 points in a regular grid (25 or 50 m) and the dried
soil samples were stored at our Department. In 1971 and 2002, the original grid points were revisited and re-sampled. Land
use changes affected the soil C stock significantly. In 1937, carbon stocks were significantly smaller in the arable fields
than in the grassland soil. In the field that was converted from arable back to grassland, soil C increased significantly
at an average rate of about 0.4 Mg ha−1 year−1. A soil C balance model (ICBM) driven by standard meteorological data and soil carbon input estimated from yield records
described soil carbon dynamics reasonably well, although the range of simulated relative changes in C stocks between 1937
and 2002 in the four fields (from −7.4 to +8.8%) was narrower than those measured (from −19.5 to +16.5%). There are only few
long-term studies in Northern Europe available for quantifying the effect of land use change on soil carbon stocks and the
results presented here are therefore useful for improving predictions of changes in soil carbon driven by land use change. 相似文献
102.
André Campaniço Dr. Marta P. Carrasco Dr. Mathew Njoroge Ronnett Seldon Prof. Kelly Chibale Dr. João Perdigão Prof. Isabel Portugal Prof. Digby F. Warner Prof. Rui Moreira Prof. Francisca Lopes 《ChemMedChem》2019,14(16):1537-1546
Herein we report the screening of a small library of aurones and their isosteric counterparts, azaaurones and N-acetylazaaurones, against Mycobacterium tuberculosis. Aurones were found to be inactive at 20 μm , whereas azaaurones and N-acetylazaaurones emerged as the most potent compounds, with nine derivatives displaying MIC99 values ranging from 0.4 to 2.0 μm . In addition, several N-acetylazaaurones were found to be active against multidrug-resistant (MDR) and extensively drug-resistant (XDR) clinical M. tuberculosis isolates. The antimycobacterial mechanism of action of these compounds remains to be determined; however, a preliminary mechanistic study confirmed that they do not inhibit the mycobacterial cytochrome bc1 complex. Additionally, microsomal metabolic stability and metabolite identification studies revealed that N-acetylazaaurones are deacetylated to their azaaurone counterparts. Overall, these results demonstrate that azaaurones and their N-acetyl counterparts represent a new entry in the toolbox of chemotypes capable of inhibiting M. tuberculosis growth. 相似文献
103.
Helga Tima Adrienn Berkics Zoltán Hannig András Ittzés Eleonóra Kecskésné Nagy Csilla Mohácsi-Farkas 《Food Additives and Contaminants: Part B: Surveillance Communications》2018,11(1):37-42
Among Fusarium mycotoxins, deoxynivalenol (DON) is the most common contaminant in case of cereals and cereal-based foods in Hungary. In this study, Hungarian wheat (n = 305), maize (n = 108), wheat flour (n = 179) and pasta (n = 226) samples were analysed (N = 818). The samples were collected during 2008–2015 in Hungary. Applied methods of analysis were enzyme-linked immunosorbent assay and liquid-chromatography coupled with a mass spectrometer. Results were compared and evaluated with Hungarian weather data. Among cereal samples, in 2011, wheat was contaminated with DON (overall average ± standard deviation was 2159 ± 2818 µg kg?1), which was above the maximum limit (ML). In case of wheat flour and pasta, no average values above ML were found during 2008–2015, but higher DON contamination could be observed in 2011 as well (wheat flour: 537 ± 573 µg kg?1; pasta: 511 ± 175 µg kg?1). 相似文献
104.
Optimization of cashew gum and chitosan for microencapsulation of pequi oil by complex coacervation 下载免费PDF全文
105.
Sebastian Siwek Javane Oktaee Sven Grasselt-Gille André Wagenführ 《Holz als Roh- und Werkstoff》2018,76(2):499-507
This research investigated the effect of different fractions of commercial wood flour (Type c100 from JRS, Germany) on mechanical and physical properties of wood-polymer composites (WPC). The fractions were named regarding the mean lengths of their particles in µm; 80, 130, 255, 405 and 485. The composite samples were manufactured with 30 wt% of wood flour fractions of all five groups as well as the not fractionated flour, and 70 wt% of cellulose propionate (CP). The melt mass-flow rate (MFR) of the different granules, tensile strength, and modulus of elasticity, flexural strength, flexural modulus and the impact strength of the injection molded specimens as well as the water uptake were determined in this study. WPCs with the specific size range used in this investigation exhibited improved strength and modulus of elasticity in tensile and flexural tests, compared to pure CP. Using fraction 255, the mechanical properties increased the most. Tensile strength rose by 28 and 13% compared to CP and to WPC with the not fractioned wood powder, respectively. Fraction 255 increased flexural strength by 33 and 5% compared to CP and WPC with the not fractioned flour. The MFR (tested at 190 °C with 7.16 kg) of WPC_255 is the lowest with 2.3 g/10 min. Composites with the smallest particles showed the least water uptake. 相似文献
106.
André H. A. van den Oord P. D. van Wassenaar 《Zeitschrift für Lebensmitteluntersuchung und -Forschung A》1997,205(2):125-130
In the literature there are reports that 31 di-and tripeptides elicit umami (i.e. monosodium L-glutamate-like or MSG-like) or savoury tastes. However, the occurrence of “umami peptides” is questioned with regard to the
high specificity of those that give an umami taste. A total of 12 dipeptides and 4 tripeptides were selected for a re-examination
of their taste properties. Criteria were that: (1) their taste has been described as umami, savoury or brothy; (2) they have
a threshold value; and (3) they should fit into the theoretical framework of L-glutamyl peptides discussed. The peptides – in aqueous solutions, at room temperature, at pH 6.0 and 4.0, and at concentrations
well above the reported threshold values – were tasted. Panel members were selected on the basis of their ability to perceive
the umami taste of 2.67 mM MSG at pH 6.0. None of the peptides tested was found to elicit an umami taste. The taste of L-glutamic acid in the peptides was lost and furthermore the taste of bitter amino acids in the peptides was no longer perceivable.
Within the range of Glu-X peptides, even Glu-Glu and Glu-Asp, which have previously been reported to elicit umami tastes,
did not taste MSG-like either in pure solution or in the presence of sodium chloride. The tripeptide Ala-Glu-Ala, reported
to have an “umami threshold” value as low as 0.8 mM, was found not to have an umami taste or any other specific taste up to
10 mM. The general occurrence of umami peptides appears to be highly unlikely.
Received: 6 December 1996 相似文献
107.
Koczor Sándor Vuts József Caulfield John C. Withall David M. Sarria André Pickett John A. Birkett Michael A. Csonka Éva Bálintné Tóth Miklós 《Journal of chemical ecology》2021,47(6):525-533
Journal of Chemical Ecology - The sex pheromone composition of alfalfa plant bugs, Adelphocoris lineolatus (Goeze), from Central Europe was investigated to test the hypothesis that insect species... 相似文献
108.
109.
Cleide Borsoi Betina Hansen Ruan Ezequiel Gemmer Marcos Aurélio Dahlem Júnior Edson Luiz Francisquetti Ademir José Zattera Ruth Marlene Campomanes Santana André Luis Catto 《应用聚合物科学杂志》2021,138(45):51350
This study presents the preparation of post-consumer polypropylene (r-PP) composites filled with 30 wt% yerba mate (YM) stick particles. To improve the fiber–matrix adhesion, three surface treatments were performed: alkaline treatment with sodium hydroxide (NaOH) and use of 3-aminopropyltriethoxysilane (APTS) and maleic anhydride graft polypropylene copolymer (PP-g-MA) as coupling agents. Mechanical properties including tensile, flexural, and impact resistance were determined, and chemical (Fourier transform infrared spectroscopy [FTIR]), physical (water absorption), and morphological analyses were performed. The main findings show that the treatments were efficient in improving the mechanical properties of the composites, with emphasis on the r-PP/YM30/APTS and r-PP/YM30/PP-g-MA composites, which proved to be superior in tensile, flexion and impact strength and absorption of water compared to the untreated composite. The morphological analysis showed a better interaction between the fiber and the polymeric matrix for the composites with YM/APTS and YM/PP-g-MA, which corroborates the results of tensile and flexural strength, as well as with the spectra of FTIR in which the chemical modification of the fibers is observed. However, the results show that these treatments are promising in obtaining composites with recycled matrix with better properties. 相似文献
110.
Maria T. M. Bizarria André L. F. de M. Giraldi Cesar M. de Carvalho Jose I. Velasco Marcos A. d'Ávila Lucia H. I. Mei 《应用聚合物科学杂志》2007,104(3):1839-1844
Recycled PET/organoclay nanocomposites were prepared by melt intercalation process with several amounts (1, 3, and 5 wt %) of clay modified with quaternary ammonium salt (DELLITE 67G) dispersed in a recycled poly(ethylene terephthalate) (rPET) matrix. The resultant mechanical properties (modulus and yield strength) of the nanocomposites were found to be different from those of rPET. Wide angle X‐ray scattering (WAXS) and Transmission Electron Microscopy (TEM) measurements have shown that although complete exfoliation was not achieved, delaminated clay platelets could be observed. Thermal analysis did not show significant changes in the thermal properties from those of recycled PET. Mechanical testing showed that nanocomposite properties were superior to the recycled PET in terms of strength and elasticity modulus. This improvement was attributed to nanoscale effects and strong interaction between the rPET matrix and the clay interface, as revealed by WAXS and TEM. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1839–1844, 2007 相似文献