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排序方式: 共有841条查询结果,搜索用时 15 毫秒
31.
32.
Volatile Emissions Triggered by Multiple Herbivore Damage: Beet Armyworm and Whitefly Feeding on Cotton Plants 总被引:5,自引:3,他引:5
Plants are commonly attacked by more than one species of herbivore, potentially causing the induction of multiple, and possibly competing, plant defense systems. In the present paper, we determined the interaction between feeding by the phloem feeder silverleaf whitefly (SWF), Bemisia tabaci Gennadius (B-biotype = B. argentifolii Bellows and Perring), and the leaf-chewing beet armyworm (BAW), Spodoptera exigua Hübner, with regard to the induction of volatile compounds from cotton plants. Compared to undamaged control plants, infestation with SWF did not induce volatile emissions or affect the number and density of pigment glands that store volatile and nonvolatile terpenoid compounds, whereas infestation by BAW strongly induced plant volatile emission. When challenged by the two insect herbivores simultaneously, volatile emission was significantly less than for plants infested with only BAW. Our results suggest that tritrophic level interactions between cotton, BAW, and natural enemies of BAW, that are known to be mediated by plant volatile emissions, may be perturbed by simultaneous infestation by SWF. Possible mechanisms by which the presence of whiteflies may attenuate volatile emissions from caterpillar-damaged cotton plants are discussed. 相似文献
33.
P. Cañizares J. García-Gómez C. Sáez M.A. Rodrigo 《Journal of Applied Electrochemistry》2003,33(10):917-927
The electrochemical oxidation of 4-chlorophenol, 2,4-dichlorophenol and 2,4,6-trichlorophenol aqueous wastes using boron-doped diamond electrodes was studied. This treatment led to complete mineralization of the wastes regardless of the operating conditions. A simple mechanistic model is consistent with the voltammetric and electrolysis results. According to this model, the electrochemical treatment of chlorophenol aqueous wastes involves the anodic and cathodic release of chlorine followed by the formation of non-chlorinated aromatic intermediates. Subsequent cleavage of the aromatic ring gives rise to non-chlorinated carboxylic acids. Chlorine atoms arising from the hydrodehalogenation of the chlorophenols are converted into more oxidized molecules at the anode. These molecules react with unsaturated C4 carboxylic acid to finally yield trichloroacetic acid through a haloform reaction. The non-chlorinated organic acids are ultimately oxidized to carbon dioxide and the trichloroacetic acid into carbon dioxide and volatile organo-chlorinated molecules. Both direct and mediated electrochemical oxidation processes are involved in the electrochemical treatment of chlorophenols. 相似文献
34.
Celeste Fernández Eduardo Lujano Ursula Macias Josseilin Marcano Pablo J. Baricelli Clementina Longo Sergio A. Moya María G. Solórzano Marisol C. Ortega Alvaro J. Pardey 《Catalysis Letters》2004,95(3-4):143-150
Rhodium(I) complexes of the type, cis-[Rh(CO)2(amine)2](PF6) where (amine = 3-picoline, 2-picoline, pyridine, 2,6-lutidina or 3,5-lutidine) dissolved in 80% aqueous amine solutions catalyzed the selective reduction of 4-nitrobenzoic acid to 4-aminobenzoic acid under CO atmosphere. The importance of these catalytic systems is their high chemo selectivity for the aromatic nitro group of the 4-nitrobenzoic acid with respect to the carboxylic group, allowing the production of the desired aromatic amine in high yields. The 4-aminobenzoic acid production depends on the nature of the coordinated amine. The Rh/3,5-lutidine system, the most active catalyst among tested, displays turnover frequencies for 4-aminobenzoic acid production of about 173 moles per mole Rh per day for [Rh] = 1 × 10?4 mol, [4-nitrobenzoic acid] = 3.82 × 10?3mol, 10 mL of 80% aqueous 3,5-lutidine, P(CO) = 0.9 atm at 100 °C. Analyses of kinetic results for the Rh/3,5-lutidine system show a first order dependence on 4-nitrobenzoic acid concentration, a non-linear dependence on CO pressure, a segmented Arrhenius plot and dependence on the nature of the reducing gas agent. These data are discussed in terms of a possible mechanism. 相似文献
35.
P. Cañizares J. Lobato J. García-Gómez M.A. Rodrigo 《Journal of Applied Electrochemistry》2004,34(1):111-117
This paper describes a combined adsorption/electrochemical reaction device for the treatment of acidic aqueous phenol wastes. The system works in batch mode. In each operation cycle there are two stages: (i) treatment of waste, in which the organic matter contained in the waste is removed from the aqueous solution and (ii) activated carbon regeneration, in which adsorbed organics are removed from the system and converted into carbon dioxide. The system leads to successful treatment of these wastes and transforms the organics contained in the waste into carbon dioxide and electrocoagulated solids. The granular activated carbon (GAC) bed of the system achieves rapid removal of the organics, with treatment time shorter than those reported for conventional electrochemical treatments. The regeneration of the GAC is achieved by electrochemical means and efficiencies close to 80% are obtained. The energy consumption of this system is similar to those reported for other electrochemical technologies used to treat aqueous wastes. 相似文献
36.
Olive oil, a major component of the Mediterranean diet, has been associated in some small clinical trials and cross-sectional
studies with a reduction in blood pressure. The objective of this study was to assess the association of olive oil consumption
with the incidence of hypertension in an epidemiologic cohort, the Seguimiento Universidad de Navarra (SUN) study. The SUN
Project is a prospective cohort study whose members are all university graduates. The recruitment and follow-up of participants
is made using mailed questionnaires. Diet was assessed using a semiquantitative food frequency questionnaire previously validated
in Spain, with 136 items. Outcomes of interest were newly diagnosed cases of hypertension, as reported by participants in
the follow-up questionnaires. Logistic regression models were fit to assess the risk of hypertension associated with olive
oil consumption. For the present analysis, we have taken in consideration the first 6,863 participants, with at least 2 yr
of follow-up. After a median follow-up time of 28.5 mon, the cumulative incidence of hypereension was 4.7% in men and 1.7%
in women. A lower risk of hypertension was observed among participants with a higher olive oil consumption at baseline, but
the results were not statistically significant (P=0.13 for the linear trend test in the multivariate model). However, among men, the adjusted odds ratios (OR) (95% confidence
intervals) of hypertension for the second to fifth quintiles of olive oil consumption, compared with the first quintile, were
0.55 (0.28–1.10), 0.75 (0.39–1.43), 0.32 (0.15–0.70), and 0.46 (0.23–0.94), respectively (P=0.02 for linear trend). No association was found between olive oil consumption and the risk of hypertension among women.
In conclusion, in a Mediterranean population, we found olive oil consumption to be associated with a reduced risk of hypertension
only among men. The lack of association observed among women might be attributed to the overall lower incidence of hypertension
found among females and the resulting lower statistical power. 相似文献
37.
Aboitiz N Vila-Perelló M Groves P Asensio JL Andreu D Cañada FJ Jiménez-Barbero J 《Chembiochem : a European journal of chemical biology》2004,5(9):1245-1255
HEV32, a 32-residue, truncated hevein lacking eleven C-terminal amino acids, was synthesized by solid-phase methodology and correctly folded with three cysteine bridge pairs. The affinities of HEV32 for small chitin fragments--in the forms of N,N',N"-triacetylchitotriose ((GlcNAc)3) (millimolar) and N,N',N",N"',N",N"'-hexaacetylchitohexaose ((GlcNAc)6) (micromolar)--as measured by NMR and fluorescence methods, are comparable with those of native hevein. The HEV32 ligand-binding process is enthalpy driven, while entropy opposes binding. The NMR structure of ligand-bound HEV32 in aqueous solution was determined to be highly similar to the NMR structure of ligand-bound hevein. Solvated molecular-dynamics simulations were performed in order to monitor the changes in side-chain conformation of the binding site of HEV32 and hevein upon interaction with ligands. The calculations suggest that the Trp21 side-chain orientation of HEV32 in the free form differs from that in the bound state; this agrees with fluorescence and thermodynamic data. HEV32 provides a simple molecular model for studying protein-carbohydrate interactions and for understanding the physiological relevance of small native hevein domains lacking C-terminal residues. 相似文献
38.
39.
Succinic acid has been pertracted with TOA using free liquid membranes without or with 1‐octanol. The addition of the alcohol led to the increase of up to 2.8–3 times of the acid's initial and final mass flows. At the same time, the influence of 1‐octanol on the transport capacity of the pertraction system was negative, its addition inducing the accumulation of succinic acid into the liquid membrane. A mathematical model describing the acid accumulation inside the liquid membrane has been developed for pertraction systems without and with 1‐octanol and offers good concordance with the experimental data. © 2012 Canadian Society for Chemical Engineering 相似文献