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541.
A. Gjevori J.W. Gerlach D. Manova W. Assmann E. Valcheva S. Mändl 《Surface & coatings technology》2011
By inserting an auxiliary rf plasma source in an experimental setup for depositing TiO2 thin films with a cathodic vacuum arc and high voltage pulses, i.e. metal plasma immersion ion implantation & deposition (MePIIID), it is shown that this auxiliary plasma source can increase the growth rate at low gas flow ratios only but not increase the oxygen/titanium ratio. It can be surmised that the plasma source creates activated oxygen species which are otherwise supplied from collisions of the titanium plasma stream with the background gas at higher pressures. 相似文献
542.
Jiadong Zang Ming Li Derek C. Sinclair Till Frömling Wook Jo Jürgen Rödel 《Journal of the American Ceramic Society》2014,97(9):2825-2831
The dielectric properties of CaZrO3 (CZ) modified 0.94Bi1/2Na1/2TiO3 (BNT)–0.06BaTiO3 (BT) and 0.82(0.94BNT–0.06BT)–0.18(K1/2Na1/2)NbO3 have been investigated by impedance spectroscopy over a wide temperature range. The presence of a highly polarizable phase in addition to a bulk response is revealed by electric modulus (M″) spectra in both systems. The relaxation frequency of the polar phase follows the Vogel–Fulcher law below the Burns temperature which decreases with increasing CZ content. The dc conductivity of the ceramics is dominated by the bulk response which follows the Arrhenius law with an activation energy ranging from 1.4 to 1.7 eV and has an oxygen partial pressure dependence consistent with n‐type semiconductivity. This information is pertinent to on‐going compositional development of relaxor‐based high‐temperature dielectrics. 相似文献
543.
Biosynthesis of Phenylnannolone A,a Multidrug Resistance Reversal Agent from the Halotolerant Myxobacterium Nannocystis pusilla B150 下载免费PDF全文
Dr. Sarah M. Bouhired Dr. Max Crüsemann Dr. Celso Almeida Dr. Tilmann Weber Prof. Dr. Jörn Piel Dr. Till F. Schäberle Prof. Dr. Gabriele M. König 《Chembiochem : a European journal of chemical biology》2014,15(5):757-765
The myxobacterial strain Nannocystis pusilla B150 synthesizes the structurally new polyketides phenylnannolone A–C. Apart from some common volatiles and siderophores, these are the first natural products from the genus Nannocystis. Phenylnannolone A shows inhibitory activity towards the ABCB1 gene product P‐glycoprotein and reverses daunorubicin resistance in cancer cells. To decipher the biochemical reactions leading to the formation of phenylnannolone A, the putative biosynthetic genes were identified (phn1, phn2). Phn2 is a polyketide synthase (PKS) with an NRPS‐like loading module, and its domain order is consistent with the phenylnannolone A structure. The functionality and substrate selectivity of the loading module were determined by means of a γ‐18O4‐ATP pyrophosphate exchange and a phosphopantetheine ejection assay. A specific activation of cinnamic acid by the AMP‐ligase was detected. Phn1 is a putative butyryl‐CoA carboxylase (BCC), providing ethylmalonyl‐CoA for the formation of the ethyl‐substituted part of phenylnannolone A. Phn1 is the first BCC found in biosynthetic genes for an ethyl‐substituted natural compound. Biosynthesis of phenylnannolone A, putatively encoded by phn1 and phn2, thus utilizes the first biosynthetic machinery in which both a BCC and a PKS are involved. 相似文献
544.
Application of hard surface coatings for spindle bearings The demands on modern Machine Tools ascends continuously with the requirements of the production for high quality and short‐time processings. Particularly the increase of the processing‐ and removal times of the last years dues to higher loads of the main spindle bearing. The bearing as a central machine component characterises the performance of the Machine Tool for the cutting process and defines the reliability of the main spindle. The majority of the applicated spindle bearings are ball bearings. A large amount of the spindle fall‐outs is caused by a non adequate or defecitive lubrication and is effected by the tribological properties of the bearing elements. For the reduction of friction and wear nowadays several materials, coatings and lubrication additives are applied. Actual researches focus on the development of hard surface coatings (a‐C:H:W) with a nano structure for the rolling contact of ball bearings to increase their reliability. In this article the test of nano structured hard surface coating systems for the reduction of friction, warming and wear are presented. Thus the coating systems are verificated for the application in spindle bearings by pretesting. According to the evaluation the inner and outer raceway of standard‐hybrid bearings are coated and the adhesion in reference to rotational speed, resistance and wear performance at high acceleration is analysed. Concluding the emergency running properties at dry‐running condition is evaluated to identify the field of application for the coatings. 相似文献
545.
In extracts obtained by liquid-liquid extraction from seven pear (Pyrus communis L.) cultivars, octane-1,3-diol, 5(Z)octene-1,3-diol, methyl 3-hydroxyoctanoate, ethyl 3-hydroxyoctanoate and ethyl 5(Z)-3-hydroxyoctenoate were identified by capillary gas chromatography-mass spectrometry. Evaluation of the absolute configuration
was achieved by multidimensional gas chromatography, using a polar achiral column (DB-Wax) and a chiral main column (2,3-di-O-acetyl-6-O-tert-butyldimethylsilyl-β-cyclodextrin/OV 1701). Comparison of retention times of synthesized optically enriched reference compounds
with those of isolated diols and hydroxy esters revealed (R)-configurations for the 3-hydroxy derivatives, exhibiting enantiomeric excesses greater than 99%. In addition, (2S, 4R)- and (2R, 4R)-2-methyl-4-pentyl-1,3-dioxane as well as (2S, 4R)- and (2R, 4R)-2-methyl-4-(2′(Z)-pentenyl)-1,3-dioxane, products formed by acetaldehyde and octane-1,3-diol or 5(Z)-octene-1,3-diol, respectively, were detected in pear fruits.
Received: 13 February 1997 相似文献
546.
In the USA, the enforcement of state sales of tobacco products to minors laws has had only limited impact upon reducing youth access. The application of consumer protection authorities by state attorneys general to alter the sales and promotion practices of tobacco retailers provides a complementary and highly leveraged strategy to increase compliance with tobacco sales to minors laws. 相似文献
547.
Jacob-Ferreira AL Lacchini R Gerlach RF Passos CJ Barbosa F Tanus-Santos JE 《The Science of the total environment》2011,409(20):4242-4246
Mercury (Hg) exposure is associated with disease conditions, including cardiovascular problems. Although the mechanisms implicated in these complications have not been precisely defined yet, matrix metalloproteinases (MMPs) may be involved. The gene encoding MMP-2 presents genetic polymorphisms which affect the expression and activity level of this enzyme. A common polymorphism of MMP-2 gene is the C−1306T (rs 243865), which is known to disrupt a Sp1-type promoter site (CCACC box), thus leading to lower promoter activity associated with the T allele. This study aimed at examining how this polymorphism affects the circulating MMP-2 levels and its endogenous inhibitor, the tissue inhibitor of metalloproteinase-2 (TIMP-2) in 210 subjects environmentally exposed to Hg. Total blood and plasma Hg concentrations were determined by inductively coupled plasma-mass spectrometry (ICP-MS). MMP-2 and TIMP-2 concentrations were measured in plasma samples by gelatin zymography and ELISA, respectively. Genotypes for the C−1306T polymorphism were determined by Taqman® Allele Discrimination assay. We found a positive association (p = 0.0057) between plasma Hg concentrations and MMP-2/TIMP-2 (an index of net MMP-2 activity). The C−1306T polymorphism modified MMP-2 concentrations (p = 0.0465) and MMP-2/TIMP-2 ratio (p = 0.0060) in subjects exposed to Hg, with higher MMP-2 levels been found in subjects carrying the C allele. These findings suggest a significant interaction between the C−1306T polymorphism and Hg exposure, possibly increasing the risk of developing diseases in subjects with the C allele. 相似文献
548.
Anna S. Schenk Igor Zlotnikov Boaz Pokroy Notburga Gierlinger Admir Masic Paul Zaslansky Andrew N. Fitch Oskar Paris Till H. Metzger Helmut Cölfen Peter Fratzl Barbara Aichmayer 《Advanced functional materials》2012,22(22):4668-4676
Biominerals are complex inorganic‐organic structures that often show excellent mechanical properties. Here a bio‐inspired study of a remarkably simple synthetic system is presented in which only one charged polymer additive (poly(sodium 4‐styrenesulfonate)) is able to induce hierarchical structuring of calcite similar to biominerals. The interaction of the negatively charged polymer with the nucleation and growth of the mineral, in particular via selective adsorption to internal and external (001) facets of the calcite lattice, implies structural features from the micrometer down to the nanometer level. The crystals exhibit a distinct rounded morphology and a controlled orientation. Moreover, the polymer molecules are occluded within the crystals with different concentrations in well‐defined regions. This leads to the induction of a mesoscale structure based on 100 nm sized mineral building blocks with granular substructure and rough surface, as well as small modifications of the crystallographic structure. Such a combination of hierarchically organized structural features has previously only been reported for biogenic calcite, which is typically grown in a complex process involving multiple organic additives. It is also shown that the organic occlusions in the calcite‐PSS hybrid crystals strongly affect the mechanical performance, as known for some biominerals. 相似文献
549.
Stevenson CN MacManus-Spencer LA Luckenbach T Luthy RG Epel D 《Environmental science & technology》2006,40(17):5580-5585
The toxicological effects of perfluoroalkyl acids on the p-glycoprotein (p-gp) cellular efflux transporter were investigated using the marine mussel Mytilus californianus as a model system. Four of the perfluoroalkyl acids studied exhibit chemosensitizing behavior, significantly inhibiting p-gp transporter activity. The inhibitory potency is maximal for the longer chain acids perfluorononanoate (PFNA) and perfluorodecanoate (PFDA), with average IC50 values of 4.8 and 7.1 microM, respectively. Results indicate that PFNA inhibits p-gp by an indirect mechanism, and this inhibition is reversible and accompanied by a rapid loss of PFNA from the tissue. In addition, PFNA induces expression of the p-gp transporter after a 2-h exposure, a stress response that may result in a metabolic cost to the organism. Given that most organisms, including humans, share efflux transporters as a first line of defense against toxicants, the results of this study may have broader implications for the ecotoxicology of perfluoroalkyl acids. 相似文献
550.
Christian Kaiser Torsten Gerlach Kirsten Simon Kristina Florschütz Gotthard Kunze 《The Science of the total environment》2010,408(23):6017-6026
A novel Arxula adeninivorans yeast estrogen screen (nAES) assay has been developed for detection of estrogenic activity in various liquid samples such as wastewater, seawater, brackish water and swine urine. Two bio-components were engineered to co-express the human estrogen receptor α (hERα) and an inducible reporter gene; either the non-conventional phytase gene (phyK, derived from Klebsiella sp. ASR1) or the non-conventional tannase gene (ATAN1, derived from Arxula). Both reporters were put under the control of an Arxula derived glucoamylase (GAA) promoter, which was modified by the insertion of two estrogen-responsive elements (EREs). The Arxula transformation/expression platform Xplor® 2, which lacks resistance markers and E. coli elements, was used to select stable mitotic transformants. They were then analyzed for robustness and suitability as the bio-component for the nAES assay. Two types of the nAES assay based on the reporter proteins phytase and tannase (nAES-P, nAES-T) were used in this work. The nAES-P type is more suitable for the analysis of seawater, brackish water and urine whereas the nAES-T type exhibited higher robustness to NaCl. Both assay types have similar characteristics for the determination of estrogen in sewage and urine samples e.g. 6-25 h assay period with detection and determination limits and EC50 values for 17β-estradiol of 2.8 ng L− 1, 5.9 ng L− 1, 33.2 ng L− 1 (nAES-P) and 3.1 ng L− 1, 6.7 ng L− 1 and 39.4 ng L− 1 (nAES-T). Substrate specificity and analytical measurement range (AMR) for both assay types are also similar. These characteristics show that the nAES assay based on non-conventional salt tolerant yeast is applicable for a high throughput estrogen analysis in the environmental and regulatory control sectors. 相似文献