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971.
高倍率低温可膨胀石墨制备的研究 总被引:6,自引:0,他引:6
本文以HNO3/HBrO3/KMnO4为氧化插层体系制备低温可膨胀石墨,研究了制备低温可膨胀石墨的最佳条件和物料配比,讨论了插层试剂对起始膨胀温度的影响,提出了氧化插层的机理.研究表明:制备低温可膨胀石墨的反应温度为室温(25 ℃);反应时间40 min;石墨、硝酸、溴酸钠、高锰酸钾的最佳质量比为1∶[KG-·2]3∶[KG-·2]0.1∶[KG-·2]0.07,由此方法制得的可膨胀石墨起始膨胀温度为130 ℃,600 ℃时膨胀容积为350 mL/g. 相似文献
972.
S. Mariccor A. B. Batoy Sabine Borgmann Karin Flick Josephine Griffith Jeffrey J. Jones Viswanathan Saraswathi Alyssa H. Hasty Peter Kaiser Charles L. Wilkins 《Lipids》2009,44(4):367-371
Here we describe a study of the feasibility of lipid and phospholipid (PL) profiling using matrix assisted laser desorption/ionization
(MALDI) Fourier transform mass spectrometry (FTMS) for two different applications. In this work PL profiles of different mammalian
tissues as well as those of whole cell organisms were examined. In particular, comparative analysis of lipid and PL profiles
of tissues from mice fed different diets was done and, in another application, MALDI FTMS was used to analyze PL profiles
of genetically modified Saccharomyces cerevisiae. Computational sorting of the observed ions was done in order to group the lipid and PL ions from complex MALDI spectra.
The PL profiles of liver tissues from mice fed different diets showed a cross correlation coefficient of 0.2580, indicating
significant dissimilarity, and revealed more than 30 significantly different peaks at the 99.9% confidence level. Histogram
plots derived from the spectra of wild type and genetically modified yeast resulted in a cross correlation coefficient 0.8941
showing greater similarity, but still revealing a number of significantly different peaks. Based on these results, it appears
possible to use MALDI FTMS to identify PLs as potential biomarkers for metabolic processes in whole cells and tissues. 相似文献
973.
Yutaka Kagawa Yasuo Kogo Hiroshi Hatta 《Journal of the American Ceramic Society》1989,72(6):1092-1094
Thermal expansion behaviors of a Si3 N4 -whisker-reinforced sodaborosilicate glass matrix composite are studied. An abrupt increase of the coefficient of thermal expansion is observed and is attributed to formation of crystobalite in the sodaborosilicate glass matrix. This thermal expansion behavior is discussed with special reference to the phase transformation of the crystobalite. 相似文献
974.
Koningsberger D.C. Mojet B.L. van Dorssen G.E. Ramaker D.E. 《Topics in Catalysis》2000,10(3-4):143-155
The physical principles of XAFS spectroscopy are given at a sufficiently basic level to enable scientists working in the field
of catalysis to critically evaluate articles dealing with XAFS studies on catalytic materials. The described data-analysis
methods provide the basic tools for studying the electronic and structural properties of supported metal, metal–oxide or metal–sulfide
catalysts. These methods include (a) fitting in R-space, (b) application of the difference file technique and (c) control of the fit procedure with k
1 and k
3 weighting with the help of phase- and amplitude-corrected Fourier transforms.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
975.
976.
Marcel Gratz Markus Wehring Petrik Galvosas Frank Stallmach 《Microporous and mesoporous materials》2009,125(1-2):30
The diffusional behavior of selected hydrocarbons adsorbed in NaX zeolites were investigated with pulsed magnetic field gradient (PFG) NMR methods in two different ways. First, the exchange time τexch of n-pentane between the interior and the exterior of the zeolite crystals was determined by two-dimensional diffusion exchange spectroscopy. The results were compared to the mean life time τintra as obtained by fast NMR tracer desorption method. Second, the diffusion of a propylene–propane mixture adsorbed in the zeolite was studied by Fourier transform PFG NMR, thus employing the chemical shift of the individual organic constituents as a second dimension for a selective evaluation of the PFG NMR signal decays and the subsequent extraction of corresponding diffusion coefficients. Modifications of NMR pulse sequences necessary for the application of ultra-high pulsed magnetic field gradients of up to in microporous materials are briefly discussed for both kind of experiments. 相似文献
977.
The aim of this investigation is to determine the effect of low‐filler volume fraction on the elastic modulus and the thermal expansion coefficient of particulate composites. In the theoretical part, theoretical model valid for low‐filler volume fractions is used to evaluate these two magnitudes. In the experimental part, low‐percentage filler contents of 3, 5, 7, and 10% are used. The density for these epoxy resin‐iron particle composites is also determined. At the same time, an attempt to explain some of the disagreements observed between theoretical values and experimental data on a qualitative basis is also made. This attempt is in part assisted by scanning electron microscopy (SEM) observations concerning structural inhomogeneities and fractographical data. The comparison of the theoretical values derived from the present model with experimental results and with theoretical values derived from other workers appears satisfactory in many cases, but in some others the discrepancies among them are considerable. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009 相似文献
978.
Degradation behavior of ZnO‐glass fiber‐unsaturated polyester composite under exposure to a metal halide lamp is investigated by means of DSC and FTIR. The FTIR results show that the UV photons can increase the carbonyl group on the surface, but ZnO can decrease the carbonyl content and further contribute to the breaking of single bond of carbon to oxygen on the surface. All of the results indicate that for pure unsaturated polyester under the UV exposure in air, the major reaction is photo‐initiated oxidation, whereas for the composites with ZnO, decarbonylation is the major effect. In addition, when the content of ZnO is not higher than 4 wt %, the composites are still transparent, and its effects on the crosslinking process and thermal stability are insignificant. Thus, ZnO can be used as a stabilizer of unsaturated polyester for the glass fiber reinforced polymer industry. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009 相似文献
979.
The structure, magnetic, and thermal expansion properties of chromium-substituted lithium ferrite have been investigated. The lattice constant (Å) decreases linearly as a (x) = 8.32366 − 0.04338x for Li0.5Fe2.5−xCrxO4 (x = 0.0–1.0). When increasing Cr content, the initial permeability decreased gradually. The average thermal expansion coefficient of Li0.5Fe2.5−xCrxO4 (x = 0.0–1.0) varied from 15.34 to 17.77 ppm/°C, with increasing Cr content, the average thermal expansion coefficient decreased. The average thermal expansion coefficient (ppm/°C) in the range of 25–850 °C give the polynomial correlation as follows, TEC (x) = 1 7.775 − 0.216x − 0.723x2 − 1.493x3 for Li0.5Fe2.5−xCrxO4 (x = 0.0–1.0). 相似文献
980.
Lithium aluminum silicate glasses of composition (wt%) 12.6Li2O–71.7SiO2–5.1Al2O3–4.9K2O–3.2B2O3–2.5P2O5 were prepared by the melt quench technique. These glasses were converted to glass–ceramics based on DTA data. X-ray diffraction (XRD) and Fourier transform infra-red spectroscopy (FTIR) were used to discern the phases evolved in the glass–ceramics. Phase morphology was studied using scanning electron microscopy (SEM). Thermal expansion coefficient (TEC) and glass transition temperature (Tg) of all samples were measured using thermo-mechanical analyzer (TMA). It was found that 3 h dwell time at crystallization temperature yielded samples with good crystallinity with a TEC of 9.461 × 10−6 °C−1. Glass–ceramic-to-metal compressive seal with SS-304 was fabricated using LAS glass–ceramic. The presence of metal housing and compressive stresses at the glass–ceramic-to-metal interface reduced average grain size and changed the overall microstructure. 相似文献