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991.
Manon A. Lourenço Mark A. Hughes Khue T. Lai Imran M. Sofi Willy Ludurczak Lewis Wong Russell M. Gwilliam Kevin P. Homewood 《Advanced functional materials》2016,26(12):1986-1994
Silicon underpins microelectronics but lacks the photonic capability needed for next‐generation systems and currently relies on a highly undesirable hybridization of separate discrete devices using direct band gap semiconductors. Rare‐earth (RE) implantation is a promising approach to bestow photonic capability to silicon but is limited to internal RE transition wavelengths. Reported here is the first observation of direct optical transitions from the silicon band edge to internal f‐levels of implanted REs (Ce, Eu, and Yb); this overturns previously held assumptions about the alignment of RE levels to the silicon band gap. The photoluminescence lines are massively redshifted to several technologically useful wavelengths and modeling of their splitting indicates that they must originate from the REs. Eu‐implanted silicon devices display a greatly enhanced electroluminescence efficiency of 8%. Also observed is the first crystal field splitting in Ce luminescence. Mid‐IR silicon photodetectors with specific detectivities comparable to existing state‐of‐the‐art mid‐IR detectors are demonstrated. 相似文献
992.
We report an interferometric method to detect chemical binding at an interface. The interference layer consists of the thin native oxide on silicon, and we utilize nearly opposite phase shifts of light at the oxide/water and oxide/silicon interfaces to achieve near-complete destructive interference. We measure selective binding of thrombin in solution to DNA aptamers covalently bound to the oxide. The technique can be used to detect and quantify surface binding of less than 1 A of material, sensitivity similar to that of surface plasmon resonance imaging or arrayed imaging reflectometry. Results are in quantitative agreement with what is predicted theoretically. The method is very convenient to implement since it utilizes unmodified silicon wafers as substrates and is extremely insensitive to both probe light bandwidth and collimation. 相似文献
993.
Takada M Lewis BJ Boudreau M Al Anid H Bennett LG 《Radiation protection dosimetry》2007,124(4):289-318
Correlations have been developed for implementation into the semi-empirical Predictive Code for Aircrew Radiation Exposure (PCAIRE) to account for effects of extremum conditions of solar modulation and low altitude based on transport code calculations. An improved solar modulation model, as proposed by NASA, has been further adopted to interpolate between the bounding correlations for solar modulation. The conversion ratio of effective dose to ambient dose equivalent, as applied to the PCAIRE calculation (based on measurements) for the legal regulation of aircrew exposure, was re-evaluated in this work to take into consideration new ICRP-92 radiation-weighting factors and different possible irradiation geometries of the source cosmic-radiation field. A computational analysis with Monte Carlo N-Particle eXtended Code was further used to estimate additional aircrew exposure that may result from sporadic solar energetic particle events considering real-time monitoring by the Geosynchronous Operational Environmental Satellite. These predictions were compared with the ambient dose equivalent rates measured on-board an aircraft and to count rate data observed at various ground-level neutron monitors. 相似文献
994.
Doxorubicin eluting beads − 1: Effects of drug loading on bead characteristics and drug distribution
Lewis AL Gonzalez MV Leppard SW Brown JE Stratford PW Phillips GJ Lloyd AW 《Journal of materials science. Materials in medicine》2007,18(9):1691-1699
DC BeadTM is a FDA cleared embolisation device for the treatment of hypervascular tumours and arteriovenous malformations. This product
is currently evaluated in a number of centres in Europe as an embolic device for transarterial chemoembolisation (TACE). The
beads consist of poly(vinyl alcohol) microspheres modified with sulfonic acid groups and are available at different size ranges
varying from 100 to 900 μm in diameter. The beads were shown to actively sequester doxorubicin hydrochloride (dox) from solution
in a time dependent upon the dose of the drug and size of the beads. Drug uptake was by an ion-exchange mechanism, and in
the absence of other ions in solution, the beads could load a maximum of around 40 mg dox/mL hydrated beads, with >99% of
drug being sequestered from the solution. A loading of 25 mg dox/mL beads was recommended as providing a practical therapeutic
dose and optimum handling characteristics. There was a decrease in equilibrium water content of the beads with increasing
dox loading, which resulted in a decrease in the average diameter of the beads and an increase in the compressive modulus.
The deliverability properties, however, were not affected after drug loading. Using a variety of microscopic methods, the
drug was shown to be distributed throughout the bead structure, but concentrated in the outer 20 μm surface layer, a feature
related to the method of synthesis. This study characterises the properties of DC Bead loaded with dox with respect to important
characteristics in embolisation and demonstrates the potential of this drug device combination for the treatment of hypervascular
tumours such as hepatocellular carcinoma. 相似文献
995.
Lewis G Xu J Madigan S Towler MR 《Journal of materials science. Materials in medicine》2007,18(8):1649-1658
This study is a contribution to the growing body of work on the influence of changes in the composition of an acrylic bone cement on various properties of the curing and cured material. The focus is on one commercially-available acrylic bone cement brand, Surgical Simplex P, and three variants of it and a series of properties, namely, setting time, maximum exotherm temperature, activation energy and frequency factor for the polymerization reaction, diffusion coefficient for the uptake of phosphate buffered saline, at 37 degrees C, ultimate compressive strength (UCS), plane-strain fracture toughness, fatigue life (under fully-reversed tension-compression stress), hardness (H) and elastic modulus (both determined using quasi-static nanoindentation), and the variation of the storage and loss moduli with frequency of the applied force in a dynamic nanoindentation test. It was found that (a) a 68% reduction in the volume of the activator, N,N dimethyl-4-toluidine, relative to the total volume of the liquid monomer (the amounts of all the constituents in the powder and of the hydroquinone in the liquid monomer remaining unchanged) led to, for example, a significant decrease in the rate of the polymerization reaction, at 37 degrees C (c') and a significant increase in H; and (b) the elimination of the pre-polymerized poly (methyl methacrylate) beads in the powder (the amounts of all the other powder constituents and those of the liquid monomer remaining unchanged) led to, for example, a significant drop in c' and a significant increase in UCS. Thus, these findings suggest a strategy for optimizing the composition of an acrylic bone cement. 相似文献
996.
Thiocyanate content and lactoperoxidase activity of individual cow's milk of different breeds were determined, and the effects of different lactoperoxidase system (LP-s) activation strategies were compared. Lactoperoxidase activity varied significantly between Friesian and both Ayrshire and Tanzania Short Horn Zebu (TSHZ), but differences between Ayrshire and TSHZ were not significant. There was no significant variation in SCN- content between breeds. The LP-s was activated using three strategies based on SCN-: namely; equal concentrations of SCN- and H2O2 (7:7, 10:10, 15:15 mg/l), excess SCN- concentrations (15:10, 20:10, 25:10 mg SCN-:H2O2/l), and excess H2O2 concentrations (10:15, 10:20, 10:25 mg SCN-:H2O2/l), plus a fourth strategy based on I- (15:15 mg I-:H2O2/l). The keeping quality (KQ) was assessed using pH, titratable acidity, clot on boiling and alcohol stability tests. All activation strategies enhanced the shelf life of milk (typically increasing KQ from around 10 to around 20 h), but it was clear that the effectiveness of the LP-s depends on the type and concentrations of the activators of the system. The LP-s activated using I- as an electron donor was more effective than the LP-s activated using SCN- as an electron donor, increasing the KQ by a further 6-8 h compared with SCN-. 相似文献
997.
998.
Wilkinson C.I. Woodhead J. Frost J.E.F. Roberts J.S. Wilson R. Lewis M.F. 《Photonics Technology Letters, IEEE》1999,11(2):155-157
We report electrical control of the polarization state of a vertical-cavity surface-emitting laser (VCSEL), The VCSEL is subject to strong external optical feedback (up to 6% of emission), with polarization controlled by a liquid-crystal (LC) element, It is found that the contrast ratio of the complete system can be enhanced compared to the contrast ratio of the LC element alone 相似文献
999.
A revision of the Dissociative Experiences Scale, including 3 new items and a more user-friendly item format, was administered to an adult community sample. Both orthogonal and oblique factor rotations of from 1 to 5 factors provide evidence of the hierarchical structure of self-reported dissociative experiences. Reliabilities are presented for a longer and a shorter Dissociation scale, and for subscales labeled Depersonalization, Absorption, and Amnesia. Also provided are the relations of the total scale and its 3 subscales to gender, age, and education, as well as to a broad and diverse set of personality attributes. The frequency of self-reported dissociative experiences was positively related to measures of Neuroticism (particularly Depression) and Imagination, and negatively related to Conscientiousness (particularly Dutifulness), Agreeableness, and to a lesser extent age. The Dissociation scales and subscales were not related to gender, educational level, or intelligence, nor to vocational interests or self-reported skills. Three subtle measures of dissociation are provided. (PsycINFO Database Record (c) 2011 APA, all rights reserved) 相似文献
1000.
Trans-4-hydroxy-2-nonenal (HNE) is a potent cytotoxic and genotoxic compound originating from the peroxidation of n-6 polyunsaturated fatty acids. Its metabolism has been previously studied in the rat (Alary et al. 1995. Chem. Res. Toxicol., 8: 35-39). In addition to major urinary mercapturic derivatives, some polar urinary metabolites were isolated and could correspond to hydroxylated compounds. 4-Hydroxynonenoic acid (HNA), resulting from the oxidation of the HNE carbonyl group, is a medium chain fatty acid and its omega-hydroxylation might be hypothesized. Therefore, the involvement of the CYP 4A family isoenzymes in the metabolism of [3H]HNE has been investigated in vivo using inducer treatments (fibrates) in wild-type or in peroxisome proliferator-activated receptor alpha (PPARalpha)-deficient mice. In wild-type mice, but not in PPARalpha (-/-) mice, fibrate treatments resulted in an increase of two urinary metabolites characterized, after HPLC purifications and mass spectrometry analyses, as the omega-hydroxylated metabolite of HNA, i.e., 4,9-dihydroxy-2-nonenoic acid, and its oxidized form, 4-hydroxy-2-nonene-1,9-dicarboxylic acid. The formation of the latter is correlated accurately to laurate hydroxylase activity studied concurrently in microsomes prepared from the liver of these animals. Basal levels of these two metabolites were measured in urine of normal and PPARalpha-deficient mice. These results are in accord with an implication of the P450 4A family in the extended oxidative metabolism of 4-HNE. 相似文献