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991.
J. Herrero-Mart��n C. Mazzoli V. Scagnoli L. Paolasini H. Walker Y. Xiao T. Brueckel R. Mittal N. Kumar S. K. Dhar A. Thamizhavel Y. Su 《Journal of Superconductivity and Novel Magnetism》2011,24(1-2):705-709
Non-resonant and element specific magnetic X-ray scattering has been used to determine the orientation of Eu and Fe magnetic moments in EuFe2As2 iron pnictide. Experiments have been carried out on single crystal samples at the ESRF. Resonant measurements on magnetic reflections at the Eu L3 absorption edge indicate that the orientation of the Eu moments in the antiferromagnetic phase (T<T N=19 K) lie parallel to the crystallographic a-axis. In addition, non-resonant magnetic X-ray measurements indicate that the Fe moments are aligned along the same direction in the spin density-wave ordered phase (T<T S=190 K). The temperature dependence of the integrated intensities suggests that the Fe magnetic sublattice is barely affected by the onset of Eu ordering at T N. The observation of non-zero resonant intensity on nuclear-forbidden reflections with wavevector corresponding to the Fe magnetic propagation vector at both the Eu L3 and As K absorption edges may be interpreted as the result of the polarization of the Eu 5d and As 4p electronic bands via hybridization with the Fe 3d states. 相似文献
992.
Stockdale CR Shields PM McKenna A Walker GP Dunshea FR Doyle PT 《Journal of dairy science》2011,94(1):262-272
Seventy multiparous Holstein-Friesian cows were fed different amounts of pasture and concentrates, or a total mixed ration (TMR), for 42 d in mid-lactation to test the hypothesis that the concentration of Se in milk would depend on the amount of Se consumed, when the Se is primarily organic in nature, regardless of the diet of the cows. Of the 70 cows, 60 grazed irrigated perennial pasture at daily allowances of either 20 or 40 kg of dry matter (DM)/cow. These cows received 1 of 3 amounts of concentrates, either 1, 3, or 6 kg of DM/cow per day of pellets, and at each level of concentrate feeding, the pellets were formulated to provide 1 of 2 quantities of Se from Se yeast, either about 16 or 32 mg of Se/d. The other 10 cows were included in 2 additional treatments where a TMR diet was supplemented with 1 kg of DM/d of pellets formulated to include 1 of the 2 quantities of supplemental Se. Total Se intakes ranged from 14.5 to 35.9 mg/d, and of this, the Se-enriched pellets provided 93, 91, and 72% of the Se for cows allocated 20 and 40 kg of pasture DM/d or the TMR, respectively. No effects of the amount of Se consumed on any milk production variable, or on somatic cell count, body weight, and body condition score, for either the pasture-fed or TMR-fed cows were found. Milk Se concentrations responded quickly to the commencement of Se supplementation, reaching 89% of steady state levels at d 5. When milk Se concentrations were at steady state (d 12 to 40), each 1 mg of Se eaten increased the Se concentration of milk by 5.0 μg/kg (R2 = 0.97), and this response did not seem to be affected by the diet of the cows or their milk production. The concentration of Se in whole blood was more variable than that in milk, and took much longer to respond to change in Se status, but it was not affected by diet at any time either. For the on-farm production of Se-enriched milk, it is important to be able to predict milk Se concentration from Se input. In our study, type of diet did not affect this relationship. 相似文献
993.
A primary culture technique for rainbow trout (Oncorhynchus mykiss) gill cells was optimized to better represent the intact gill in vivo in response to waterborne toxic metals. Modifications in cell seeding density and culture conditions resulted in a gill epithelial cell culture model, which displayed classic in vivo responses to toxic metals. Metallothionein-A (MTA), metallothionein-B (MTB), zinc transporter-1 (ZnT-1), glutathione-S-transferase (GST), and glucose-6-phosphate-dehydrogenase (G6PD) all showed dose-dependent increases in expression at the mRNA level in response to waterborne zinc. Of these genes, the change in zinc-induced expression relative to the control was greatest for MTA, MTB, and ZnT-1. MT expression was also induced by silver, lead, copper, and cadmium. Cells cultured with freshwater on the apical side maintained the net transepithelial influx of Ca2+ displayed by freshwater trout gills in vivo, and there was an active inward movement of Ca2+. Waterborne zinc applied to the apical compartment reduced the net uptake of Ca2+ by stimulating the efflux component. The use of endogenous metal-responsive gene expression and inhibition of ion transport in the developed cell culture system will facilitate studies of metal-gill interactions and may prove to have future practical applications within biomonitoring of natural waters. 相似文献
994.
Fifteen ruminally cannulated, nonlactating Holstein cows were used to measure the effects of 2 strains of Saccharomyces cerevisiae, fed as active dried yeasts, on ruminal pH and fermentation and enteric methane (CH4) emissions. Nonlactating cows were blocked by total duration (h) that their ruminal pH was below 5.8 during a 6-d pre-experimental period. Within each block, cows were randomly assigned to control (no yeast), yeast strain 1 (Levucell SC), or yeast strain 2 (a novel strain selected for enhanced in vitro fiber degradation), with both strains (Lallemand Animal Nutrition, Montréal, QC, Canada) providing 1 × 1010 cfu/head per day. Cows were fed once daily a total mixed ration consisting of a 50:50 forage to concentrate ratio (dry matter basis). The yeast strains were dosed via the rumen cannula daily at the time of feeding. During the 35-d experiment, ruminal pH was measured continuously for 7 d (d 22 to 28) by using an indwelling system, and CH4 gas was measured for 4 d (d 32 to 35) using the sulfur hexafluoride tracer gas technique (with halters and yokes). Rumen contents were sampled on 2 d (d 22 and 26) at 0, 3, and 6 h after feeding. Dry matter intake, body weight, and apparent total-tract digestibility of nutrients were not affected by yeast feeding. Strain 2 decreased the average daily minimum (5.35 vs. 5.65 or 5.66), mean (5.98 vs. 6.24 or 6.34), and maximum ruminal pH (6.71 vs. 6.86 or 6.86), and prolonged the time that ruminal pH was below 5.8 (7.5 vs. 3.3 or 1.0 h/d) compared with the control or strain 1, respectively. The molar percentage of acetate was lower and that of propionate was greater in the ruminal fluid of cows receiving strain 2 compared with cows receiving no yeast or strain 1. Enteric CH4 production adjusted for intake of dry matter or gross energy, however, did not differ between either yeast strain compared with the control but it tended to be reduced by 10% when strain 2 was compared with strain 1. The study shows that different strains of S. cerevisiae fed as active dried yeasts vary in their ability to modify the rumen fermentative pattern in nonlactating dairy cows. Because strain 2 tended (when compared with strain 1) to lower CH4 emissions but increase the risk of acidosis, it may be prudent to further evaluate this strain in cattle fed high-forage diets, for which the risk of acidosis is low but CH4 emissions are high. 相似文献
995.
996.
Gas chromatographic methods are described for the determination of naturally occurring ethyl carbamate in distilled spirits at levels as low as 5 ppb. Bottled products, such as whisky, gin and brandy, are extracted in the presence of n-propyl carbamate as internal standard and analysed by capillary column gas chromatography with either nitrogen specific or mass spectrometric detection. A shorter extraction procedure is satisfactory when the more sensitive and selective mass spectrometric detection is used. Direct sample injection without extraction may be used for higher alcoholic strength cask and new-make samples. Analysis of 181 blended Scotch whisky samples indicated ethyl carbamate concentrations ranging from 20 to 75 ppb. Concentrations in 48 malt whiskies ranged from 15–100 ppb. Ethyl carbamate was not detected in gin, vodka and rectified neutral alcohol. All concentrations in bottled product fell below the Canadian limit of 150 ppb in distilled spirits. 相似文献
997.
M. P. Brady K. A. Unocic M. J. Lance M. L. Santella Y. Yamamoto L. R. Walker 《Oxidation of Metals》2011,75(5-6):337-357
A family of alumina-forming austenitic (AFA) stainless steels is under development for use in aggressive oxidizing conditions from ~600?C900 °C. These alloys exhibit promising mechanical properties but oxidation resistance in air with water vapor environments is currently limited to ~800 °C due to a transition from external protective alumina scale formation to internal oxidation of aluminum with increasing temperature. The oxidation behavior of a series of AFA alloys was systematically studied as a function of Cr, Si, Al, C, and B additions in an effort to provide a basis to increase the upper-temperature oxidation limit. Oxidation exposures were conducted in air with 10% water vapor environments from 800?C1000 °C, with post oxidation characterization of the 900 °C exposed samples by electron probe microanalysis (EPMA), scanning and transmission electron microscopy, and photo-stimulated luminescence spectroscopy (PSLS). Increased levels of Al, C, and B additions were found to increase the upper-temperature oxidation limit in air with water vapor to between 950 and 1000 °C. These findings are discussed in terms of alloy microstructure and possible gettering of hydrogen from water vapor at second phase carbide and boride precipitates. 相似文献
998.
999.
Gilbert C. Walker Yujie Sun Senli Guo John A. Finlay Maureen E. Callow James A. Callow 《The Journal of Adhesion》2013,89(10-11):1101-1118
The mechanical properties of the adhesive produced by spores of the green, marine, fouling alga Ulva linza are reported. Atomic force microscopy studies were performed and nanoindentation data were analyzed using a model for an asymmetric indenter. Freshly secreted adhesive is characterized by multiple layers. We found that the modulus of the outer ~600-nm thick layer was about 0.2 ± 0.1 MPa, whereas the modulus of the inner layer was about 3 ± 1 MPa. Older adhesive showed the formation of a “crust” of harder material with a yield strength of ~20 MPa at a loading rate of 2.5 × 10?6 N · s?1. Mechanical properties under tension are also described, and extension profiles that showed either constant or nonlinear force changes with tip-sample separation were observed. Models for both kinds of behavior are described. The work of adhesion between poly-dimethylsiloxane (PDMS)-coated AFM tips and the adhesive was determined to be less than 1.5 mJ · m?2. 相似文献
1000.
NN Biswas SJ Ting MC Mattingly JM Bishop NM Cason VP Kenney RC Ruchti WD Shephard WW Neale PA Elcombe MJ Goodrick JC Hill W Kowald WD Walker P Lucas L Voyvodic R Ammar D Coppage R Davis D Day J Gress S Kanekal N Kwak L Herder J Whitmore RA Lewis BY Oh GA Smith W Toothacker 《Canadian Metallurgical Quarterly》1986,33(11):3167-3171