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151.
An array of quantum rings with local (ring by ring) modulation of the spin orbit interaction (SOI) can lead to novel effects in spin state transformation of electrons. It is shown that already small (3 x 3, 5 x 5) networks are remarkably versatile from this point of view: Working in a given network geometry, the input current can be directed to any of the output ports, simply by changing the SOI strengths by external gate voltages. Additionally, the same network with different SOI strengths can be completely analogous to the Stern-Gerlach device, exhibiting spatial-spin entanglement. 相似文献
152.
Improved in vitro anti-tumoral activity, intracellular uptake and apoptotic induction of gemcitabine-loaded pegylated unilamellar liposomes 总被引:1,自引:0,他引:1
Celia C Calvagno MG Paolino D Bulotta S Ventura CA Russo D Fresta M 《Journal of nanoscience and nanotechnology》2008,8(4):2102-2113
Anaplastic thyroid carcinoma is one of the most aggressive and lethal solid carcinomas affecting humans. A major limit of the chemotherapeutic agents is represented by their low therapeutic index. In this work, we investigated the possibility of improving the anti-tumoral activity of gemcitabine by using pegylated unilamellar liposomes. Liposomes were made up of 1,2-dipalmitoyl-sn-glycero-3-phospocholine monohydrate/cholesterol/N-(carbonyl-methoxypolyethylene glycol-2000)-1, 2-distearoyl-sn-glycero-3-phosphoethanolamine (6:3:1 molar ratio) and they were prepared with a pH gradient to improve the gemcitabine loading capacity. The anti-tumoral efficacy of the liposomal formulation was tested in vitro on human anaplastic thyroid carcinoma cells (ARO) in culture, comparing the effects with those of the free drug. Gemcitabine-loaded unilamellar liposomes had a mean size approximately 200 nm with a zeta potential approximately -2 mV. The liposomal carrier noticeably improved the anti-tumoral activity of gemcitabine against ARO cells in terms of both dose-dependent cytotoxic effect and of drug exposition effect. Namely, gemcitabine-loaded liposomes showed a cytotoxic effect (58.2% increase of cell mortality at 1 microM with respect to free drug) after 12 h incubation, while the free drug showed a significant activity only after 72 h incubation. Moreover, a significant effect on the cell mortality appeared at 0.1 microM and 100% mortality was detected at a concentration of 1 microM of gemcitabine-loaded liposomes, while the free drug elicited the same effect at a concentration of 100 microM. The improved anti-tumoral activity of gemcitabine determined by the liposomal carrier was due to a greater intracellular uptake. The intracellular gemcitabine levels as a function of time showed a sinusoidal profile with peaks after 2 h, 6 h and 11 h, related to the cellular cycle of ARO. PARP cleavage and DNA fragmentation analysis provided clear evidence of the apoptosis induction in ARO cells by treatment with liposomally entrapped gemcitabine after 72 h incubation. Thus, gemcitabine-loaded liposomes may have a potential therapeutic relevance for the treatment of anaplastic thyroid carcinoma. 相似文献
153.
Alcohol-affected pedestrians are among the highest-risk groups involved in pedestrian casualty crashes. This paper investigates the opportunities to use a modified form of traffic signal operation during high-risk periods and at high-risk locations to reduce alcohol-affected pedestrian crashes and the severity of injuries that might otherwise occur. The 'Dwell-on-Red' treatment involves displaying a red traffic signal to all vehicle directions during periods when no vehicular traffic is detected, so that drivers approach high-risk intersections at a lower speed than if a green signal were displayed. Vehicle speed data were collected before and after treatment activation at both a control and treatment site. Speed data were collected both 30 m prior to and at the intersection stop line. The treatment was associated with a reduction in mean vehicle speeds of 3.9 kph (9%) and 11.0 kph (28%) at 30 m and stop line collection points, respectively, and substantial reductions in the proportion of vehicles travelling at threatening speeds with regard to the severity of pedestrian injury. Other important road safety concerns may also benefit from this form of traffic signal modification, and it is recommended that other areas of application be explored, including the other severe trauma categories typically concentrated around signalised intersections. 相似文献
154.
A completely noncontact temperature system is described for amplification of DNA via the polymerase chain reaction (PCR) in glass microfluidic chips. An infrared (IR)-sensitive pyrometer was calibrated against a thermocouple inserted into a 550-nL PCR chamber and used to monitor the temperature of the glass surface above the PCR chamber during heating and cooling induced by a tungsten lamp and convective air source, respectively. A time lag of less than 1 s was observed between maximum heating rates of the solution and surface, indicating that thermal equilibrium was attained rapidly. Moreover, the time lag was corroborated using a one-dimensional heat-transfer model, which provided insight into the characteristics of the device and environment that caused the time lag. This knowledge will, in turn, allow for future tailoring of the devices to specific applications. To alleviate the need for calibrating the pyrometer with a thermocouple, the on-chip calibration of pyrometer was accomplished by sensing the boiling of two solutions, water and an azeotrope, and comparing the pyrometer output voltage against the known boiling points of these solutions. The "boiling point calibration" was successful as indicated by the subsequent chip-based IR-PCR amplification of a 211-bp fragment of the B. anthracis genome in a chamber reduced beyond the dimensions of a thermocouple. To improve the heating rates, a parabolic gold mirror was positioned above the microfluidic chip, which expedited PCR amplification to 18.8 min for a 30-cycle, three-temperature protocol. 相似文献
155.
A fluorogenic derivative of 1,3-alternate calix[4]arenebis(crown-6) (1) containing a dansyl group in the proton-ionizable side arm has been employed in selective sensing of Tl+ and Cs+ at low concentration levels in MeCN-H2O (1:1) mixed solvent. Optical recognition of these two metal cations by 1 occurs in contrasting modes. On the basis of the results of fluorescence, matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS), and 1H NMR studies, Tl+ and Cs+ react with 1 via formation of 1:1 complexes that differ in coordination arrangement around the metal ion. 相似文献
156.
Vasconcellos LA Blando E Souto AA Oliveira MG Woitchunas GF Hübler R 《Journal of materials science. Materials in medicine》2007,18(8):1659-1663
The use of multi-component femoral implants to replace the femur head and re-establish bone motion has been widespread since
the 70s. Frequently these implants have spherical metallic heads made of, for example, 316-L stainless steel or Cr–Co alloys,
which allow rotational motion towards a polymeric component (UHMWPE). One of the major causes of implant rejection is the
generation of UHMWPE debris on the surface between the implant head and the polymeric component. The gamma ray sterilization
of implants and the periodical X-ray medical control could contribute to premature degradation of the polymeric surface, resulting
in increased wear and shortened lifetime of the implant. In this work we study the degradation degree of the polymeric UHMWPE
component as function of the X-ray dose. The elasto-plastic deformation and recovery were carried out by means of a nanohardness
tester equipment and the polymer degradation was measured using a fast Fourier transform infra-red (FT-IR) equipment. The
results show the compromise among the irradiation doses, the surface oxidation and the mechanical properties of the samples. 相似文献
157.
Lyons RE Lesieur E Kim M Wong DC Huson MG Nairn KM Brownlee AG Pearson RD Elvin CM 《Protein engineering, design & selection : PEDS》2007,20(1):25-32
Resilin is an elastic protein found in specialized regions of the cuticle of insects, which displays unique resilience and fatigue lifetime properties. As is the case with many elastomeric proteins, including elastin, gliadin and spider silks, resilin contains distinct repetitive domains that appear to confer elastic properties to the protein. Recent work within our laboratory has demonstrated that cloning and expression of exon 1 of the Drosophila melanogaster CG15920 gene, encoding a putative resilin-like protein, results in a recombinant protein that can be photochemically crosslinked to form a highly resilient, elastic biomaterial (Rec1 resilin). The current study describes a recursive cloning strategy for generating synthetic genes encoding multiple copies of consensus polypeptides, based on the repetitive domains within resilin-like genes from D. melanogaster and Anopheles gambiae. A simple non-chromatographic purification method that can be applied to these synthetic proteins and Rec1 is also reported. These methods for the design and purification of resilin-like periodic polypeptides will facilitate the future investigation of structural and functional properties of resilin, and the development of novel highly resilient biomaterials. 相似文献
158.
Zaporozhcheno VG Potekhina MV Nemets MG Krasil'shchikov MI Polesskiĭ VA Baĭmurunova GO Osipova EM 《Voprosy pitaniia》2007,76(2):45-49
In article the problem of vocational hygienic training of the food industry workers is presented. Offers on perfection of this work are given. 相似文献
159.
Objective
To examine the influence of US‐based tobacco leaf‐buying companies, Universal Corporation and Alliance One International, on Malawi''s economy and trade policy in 2000–6.Design
Analyses of ethnographic data and tobacco industry documents.Results
Universal Corporation and Alliance One International, through their subsidiary companies Limbe Leaf and Alliance One, respectively, in Malawi, control policy‐making advisory groups and operate a tobacco cartel to influence Malawi''s economic and trade sectors. Limbe Leaf''s corporate secretary and lawyer is a member of several policy‐making committees that advise the Malawi government on tobacco‐related trade policy. The corporate representative''s presence prevents other committee members from taking positions against the tobacco industry and ensures government policy that advances industry interests to obtain low‐cost tobacco. The World Bank and Malawi''s Anti‐corruption Bureau report allegations of collusion between Limbe Leaf and Alliance One over prices at tobacco markets. Allegations of collusion between Limbe Leaf and Alliance One prompted Malawi President Bingu Mutharika in 2006 to warn the companies to end non‐competitive practices or leave the country, but there was no meaningful follow‐up action. Findings from interviews with small‐scale tobacco traders in Malawi suggest that Universal and Alliance One International purchase smuggled raw tobacco from the neighbouring countries, Zambia and Mozambique, undermining growers'' efforts to benefit from tobacco farming in Malawi.Conclusion
These actions restrict competition, depress tobacco prices for Malawi''s farmers and contribute to poverty in Malawi, while keeping the country dependent on tobacco growing.Malawi (fig 11)) is the 13th poorest country in the world.1 In all, 76% of Malawians, survive on less than US$2 (£1.02, €150) per day.1 Malawi derives 65% of its foreign earnings from tobacco, making Malawi the most tobacco‐reliant country in the world.2 Tobacco accounts for 43% of the agricultural gross domestic product,3 13% of the overall gross domestic product4 and 23% of Malawi''s total tax base.4 Out of a total workforce of 5 million people, between 600 000 and 2 million people are employed in Malawi''s tobacco sector.5 Land devoted to tobacco growing in Malawi occupies 122 000 hectares out of 4.6 million hectares under cultivation.6,7 Over 98% of Malawi''s leaf (mostly burley tobacco8,9) is exported to 68 countries,3,5,10 with the European Union (EU; 44% of exports) and US (13% of exports) being the top destinations.11 US‐based leaf‐buying companies Universal Corporation and Alliance One International purchase Malawi''s tobacco and sell it to Philip Morris and British American Tobacco (BAT).Open in a separate windowFigure 1 Malawi is a landlocked country that transports its tobacco overland to ports in Mozambique and South Africa. Smuggling raw tobacco occurs in both directions along Malawi''s borders with Zambia and Mozambique (shaded area).Tobacco Journal International, a tobacco industry trade publication, reported in September 2006 that low and uncertain tobacco prices in Malawi created friction between tobacco farmers and leaf‐ buying companies.12,13 This trade publication, however, did not analyse the role of leaf companies, through their buying practices, in influencing tobacco prices or identify the cigarette manufacturers as the beneficiaries of Malawi''s low and uncertain tobacco prices. Our study goes beyond the Tobacco Journal International report to reveal how leaf companies and manufacturers hide behind explanations of supply and demand to deflect discussion on tobacco sectors and public dialogue on tobacco prices in Malawi from the economic practices of leaf companies and manufacturers to market forces. The purpose of this paper is to show the ways Universal and Alliance One, the main buyers of Malawi''s tobacco, control the local tobacco sector, influence Malawi''s trade policy to ensure access to low‐cost raw tobacco and depress raw tobacco prices, preventing Malawi from benefiting from tobacco growing. 相似文献160.
Size and surface effects on the MRI relaxivity of manganese ferrite nanoparticle contrast agents 总被引:1,自引:0,他引:1
Tromsdorf UI Bigall NC Kaul MG Bruns OT Nikolic MS Mollwitz B Sperling RA Reimer R Hohenberg H Parak WJ Förster S Beisiegel U Adam G Weller H 《Nano letters》2007,7(8):2422-2427
Superparamagnetic MnFe2O4 nanocrystals of different sizes were synthesized in high-boiling ether solvent and transferred into water using three different approaches. First, we applied a ligand exchange in order to form a water soluble polymer shell. Second, the particles were embedded into an amphiphilic polymer shell. Third, the nanoparticles were embedded into large micelles formed by lipids. Although all approaches lead to effective negative contrast enhancement, we observed significant differences concerning the magnitude of this effect. The transverse relaxivity, in particular r2*, is greatly higher for the micellar system compared to the polymer-coated particles using same-sized nanoparticles. We also observed an increase in transverse relaxivities with increasing particle size for the polymer-coated nanocrystals. The results are qualitatively compared with theoretical models describing the dependence of relaxivity on the size of magnetic spheres. 相似文献