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101.
Angela Sester Katrin Stüer-Patowsky Prof. Dr. Wolf Hiller Dr. Florian Kloss Prof. Dr. Stephan Lütz Prof. Dr. Markus Nett 《Chembiochem : a European journal of chemical biology》2020,21(16):2268-2273
Enzyme promiscuity has important implications in the field of biocatalysis. In some cases, structural analogues of simple metabolic building blocks can be processed through entire pathways to give natural product derivatives that are not readily accessible by chemical means. In this study, we explored the plasticity of the aurachin biosynthesis pathway with regard to using fluoro- and chloroanthranilic acids, which are not abundant in the bacterial producers of these quinolone antibiotics. The incorporation rates of the tested precursor molecules disclosed a regiopreference for halogen substitution as well as steric limitations of enzymatic substrate tolerance. Three previously undescribed fluorinated aurachin derivatives were produced in preparative amounts by fermentation and structurally characterized. Furthermore, their antibacterial activities were evaluated in comparison to their natural congener aurachin D. 相似文献
102.
Duochun Sun Stephan Senz Dietrich Hesse 《Journal of the American Ceramic Society》2003,86(6):1049-1051
Thin-film solid-state reactions in the system MgO–Nb2 O5 are experimentally investigated. MgO (001) substrates are subjected to Nb-O vapor at different temperatures in high vacuum. Thin films containing the phases Mg4 Nb2 O9 and MgNb2 O6 are formed by a vapor–solid reaction between the Nb-O vapor and the substrate. The crystallographic orientations of these phases are studied by X-ray diffractometry including pole figure analysis. Mg4 Nb2 O9 grows (11.4)-, (11.6)-, and (11.9)-oriented, whereas MgNb2 O6 grows with a preferential (241) orientation. The crystallographic relationships and their origins are discussed. 相似文献
103.
Experiments on transition and flow boiling heat transfer with refrigerant R114 inside a horizontal tube were performed at bubble flow, critical heat flux and in the transition region between bubble flow and film boiling at mass fluxes between 1200 and 4000 kg/m2 s and in the pressure range between 5 and 15 bar. In comparison with pool boiling bubble flow heat transfer depends essentially on the mass flow rates and on the vapor quality. The critical heat flux depends less on the temperature difference than in pool boiling heat transfer and exhibits a maximal and a minimal value as a function of the pressure. The critical heat flux increases with mass flow rate as already shown by Collier. In the region of transition boiling the heat flux over the difference between wall and saturation temperature approaches a horizontal curve. Therefore in this region an evaporator may always be operated under stable conditions and burn out does not occur. 相似文献
104.
In this paper, a novel cooling strategy for high performance cutting is presented. A metalworking fluid, composed of water and polyhydric alcohols is applied at temperatures below 0 °C, but above the temperatures used for cryogenic cutting. This cooling strategy is applied when rough turning Ti-6Al-4V. An analysis of temperatures, forces, tool wear and chip formation is carried out. The results are compared with those obtained using emulsion, CO2, LN2, and dry turning. It can be shown that when tempering the sub-zero metalworking fluid down to ?30° C, tool temperatures as well as tool wear are reduced, and favourable chips are produced. 相似文献
105.
The layered Li[Li0.07Ni0.1Co0.6Mn0.23]O2 materials were synthesized by sol-gel method with glycine or citric acid as chelating agent. The prepared materials were characterized by means of XRD, SEM and Raman spectroscopy. Li/Li[Li0.07Ni0.1Co0.6Mn0.23]O2 cells were assembled and subjected to charge-discharge studies at different C rates, viz 0.2, 1, 2 and 4 C. Although the samples showed less discharge capacity at 4 C rate the fade in capacity per cycle is lesser than that of capacity fade at 0.2 C rate. The citric acid assisted sample is found to be superior in terms of discharge capacity, capacity retention rate and also in thermal stability to that of sample prepared with glycine as chelating agent. 相似文献
106.
Stephan Bose-O'Reilly Gustav Drasch Saulo Rodrigues-Filho Beate Lettmeier Alexandra Maydl Uwe Siebert 《The Science of the total environment》2010,408(4):713-1000
Small scale miners use mercury to extract gold from ore in many countries. An environmental and health assessment was performed in Indonesia in two regions, Galangan in Central Kalimantan and Talawaan in Northern Sulawesi. The environmental assessment showed severe mercury contamination of the sediments, and increased mercury levels in local fish. For the health investigation 281 volunteers were recruited and examined by a standardized questionnaire, a neurological examination and neuro-psychological tests. A medical score was used consisting of significant factors of mercury intoxication. Mercury exposed workers showed typical symptoms of mercury intoxication, such as movement disorders (ataxia, tremor, dysdiadochokinesia, etc.). Blood, urine and hair samples were taken from any participant and analyzed for mercury. The mercury concentration in the biomonitors was high, partly extreme high in the working population, increased in the population living in the same habitat and low in the control group. By a standard protocol which includes a combination of threshold values of mercury in the biomonitors and a medical sum score the diagnosis of chronic mercury intoxication was made for highly burdened workers (amalgam smelters) in 55% in Sulawesi and in 62% in Kalimantan. Less exposed mineral processors and the general population in the mining areas were also intoxicated to a high percentage. 相似文献
107.
Microbiological, epidemiological, and food safety aspects of Enterobacter sakazakii 总被引:11,自引:0,他引:11
Enterobacter sakazakii is considered to be an opportunistic pathogen and has been implicated in foodborne diseases causing meningitis or enteritis, especially in neonates and infants. The U.S FoodNet 2002 survey rate of invasive infections with this organism in infants under 1 year of age was 1 per 100,000 infants. Severity of the disease is a matter of concern. In a recent study on the occurrence of E. sakazakii in production environments from food (milk powder, chocolate, cereal, potato, and pasta) factories and households, this organism was isolated with varying frequency from nearly all environments examined, strongly indicating that it is widespread. Stationary phase E. sakazakii cells are remarkably resistant to osmotic and drying stresses compared with other species of the Enterobacteriacae. In this article, we review the literature on this organism with special respect to the information relevant for food safety. 相似文献
108.
Electrolyzed water and its application in the food industry 总被引:6,自引:0,他引:6
Electrolyzed water (EW) is gaining popularity as a sanitizer in the food industries of many countries. By electrolysis, a dilute sodium chloride solution dissociates into acidic electrolyzed water (AEW), which has a pH of 2 to 3, an oxidation-reduction potential of >1,100 mV, and an active chlorine content of 10 to 90 ppm, and basic electrolyzed water (BEW), which has a pH of 10 to 13 and an oxidation-reduction potential of -800 to -900 mV. Vegetative cells of various bacteria in suspension were generally reduced by > 6.0 log CFU/ml when AEW was used. However, AEW is a less effective bactericide on utensils, surfaces, and food products because of factors such as surface type and the presence of organic matter. Reductions of bacteria on surfaces and utensils or vegetables and fruits mainly ranged from about 2.0 to 6.0 or 1.0 to 3.5 orders of magnitude, respectively. Higher reductions were obtained for tomatoes. For chicken carcasses, pork, and fish, reductions ranged from about 0.8 to 3.0, 1.0 to 1.8, and 0.4 to 2.8 orders of magnitude, respectively. Considerable reductions were achieved with AEW on eggs. On some food commodities, treatment with BEW followed by AEW produced higher reductions than did treatment with AEW only. EW technology deserves consideration when discussing industrial sanitization of equipment and decontamination of food products. Nevertheless, decontamination treatments for food products always should be considered part of an integral food safety system. Such treatments cannot replace strict adherence to good manufacturing and hygiene practices. 相似文献
109.
Crespo JF Retzek M Foetisch K Sierra-Maestro E Cid-Sanchez AB Pascual CY Conti A Feliu A Rodriguez J Vieths S Scheurer S 《Molecular nutrition & food research》2006,50(3):282-290
Oranges are clinically relevant allergenic foods. To date, orange allergens have not been characterized in detail. The study is aimed at analyzing the sensitization profile in orange-sensitized subjects with and without clinical allergy, and to identify orange allergens. Fifty-six sensitized subjects with self-reported reactions to orange were grouped into reactors (anaphylaxis or multiple episodes of immediate reactions and/or positive challenge tests) and non-reactors (negative open food challenge tests). Allergens were characterized by IgE immunoblotting, N-terminal sequencing, IgE-inhibition assays, and mediator release assays were performed to determine the allergenic potency of orange profilin. Of 56 subjects, 23 were classified as orange allergic showing mainly an oral allergy syndrome. Of 23 subjects classified as orange allergic, 22 were sensitized to profilin, Cit s 2. In patients with mono-sensitization to profilin in vitro histamine releases up to 75% from basophils were induced using orange extract and purified plant profilins. Of the allergic patients 78% were sensitized to germin-like protein, Cit s 1. Both allergens showed retained IgE reactivity in heat-processed orange juice. Interestingly, subjects with and without clinical allergy showed a comparable sensitization profile. Profilin and germin-like proteins are major orange allergens. The potential clinical relevance of orange profilin was indicated by its strong capacity to release histamine from basophils. However, a predominant sensitization to both allergens in subjects without symptoms also indicates a high frequency of clinically insignificant sensitization. 相似文献
110.
Kaufmann M Zweifel C Blanco M Blanco JE Blanco J Beutin L Stephan R 《Journal of food protection》2006,69(2):260-266
Fecal samples from 630 slaughtered finisher pigs were examined by PCR to assess the shedding of Escherichia coli O157 (rfbE) and Shiga toxin-producing E. coli (STEC, stx). The proportion of positive samples was 7.5% for rfbE and 22% for stx. By colony hybridization, 31 E. coli O157 and 45 STEC strains were isolated, and these strains were further characterized by phenotypic and genotypic traits. Among E. coli O157 strains, 30 were sorbitol positive, 30 had an H type other than H7, and none harbored stx genes. Intimin (eae), enterohemolysin (ehxA), EAST1 (astA), and porcine A/E-associated protein (paa) were present in 10, 3, 26, and 6% of strains. Among them, one eae-gamma1-positive O157:H7 strain testing positive for ehxA and astA and two eae-alpha1-positive O157:H45 strains were classified as enteropathogenic E. coli (EPEC). The O157:H45 EPEC harbored the EAF plasmid and the bfpA gene, factors characteristic for typical EPEC. The isolated STEC strains (43 sorbitol positive) belonged to 11 O:H serotypes, including three previously reported in human STEC causing hemolytic uremic syndrome (O9:H-, O26:H-, and O103:H2). All but one strain harbored stx2e. The eae and ehxA genes, which are strongly correlated with human disease, were present in only one O103:H2 strain positive for stx1 and paa, whereas the astA gene was found more frequently (14 strains). High prevalence of STEC was found among finisher pigs, but according to the virulence factors the majority of these strains seem to be of low virulence. 相似文献