全文获取类型
收费全文 | 569篇 |
免费 | 42篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 7篇 |
化学工业 | 153篇 |
金属工艺 | 4篇 |
建筑科学 | 27篇 |
矿业工程 | 1篇 |
能源动力 | 16篇 |
轻工业 | 116篇 |
水利工程 | 3篇 |
石油天然气 | 4篇 |
无线电 | 45篇 |
一般工业技术 | 75篇 |
冶金工业 | 88篇 |
原子能技术 | 4篇 |
自动化技术 | 69篇 |
出版年
2024年 | 1篇 |
2023年 | 3篇 |
2022年 | 30篇 |
2021年 | 32篇 |
2020年 | 10篇 |
2019年 | 11篇 |
2018年 | 17篇 |
2017年 | 20篇 |
2016年 | 20篇 |
2015年 | 21篇 |
2014年 | 27篇 |
2013年 | 34篇 |
2012年 | 38篇 |
2011年 | 33篇 |
2010年 | 32篇 |
2009年 | 26篇 |
2008年 | 39篇 |
2007年 | 22篇 |
2006年 | 24篇 |
2005年 | 22篇 |
2004年 | 15篇 |
2003年 | 16篇 |
2002年 | 12篇 |
2001年 | 12篇 |
2000年 | 5篇 |
1999年 | 5篇 |
1998年 | 13篇 |
1997年 | 11篇 |
1996年 | 10篇 |
1995年 | 5篇 |
1994年 | 4篇 |
1993年 | 13篇 |
1992年 | 5篇 |
1991年 | 1篇 |
1990年 | 4篇 |
1989年 | 3篇 |
1988年 | 3篇 |
1986年 | 1篇 |
1985年 | 4篇 |
1984年 | 2篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1972年 | 1篇 |
1971年 | 1篇 |
排序方式: 共有612条查询结果,搜索用时 15 毫秒
31.
据iSuppli公司,在第二季度10大智能手机厂商中,增长最快的厂商大多采用了Android操作系统,这表明谷歌的Android系统势头增强.
Droid手机专业厂商HTC,第二季度智能手机出货量比第一季度大增63.1%,增长率居业内之首. 相似文献
32.
Pauline Kang Kathleen Watt Tina Chau Jenny Zhu Bruce J.W. Evans Helen Swarbrick 《Contact lens & anterior eye》2018,41(6):501-506
Purpose
To investigate the effects of short-term orthokeratology (OK) on accommodation and binocular visual function in young adults.Methods
Twenty-four myopes (18 to 38 years) were fitted with OK lenses in both eyes. Best corrected distance visual acuity (VA), subjective and objective refractions, corneal topography and a series of binocular vision tests were measured at baseline (BL) before lens wear and then repeated after 28 nights of OK. Data from 15 subjects who demonstrated successful OK lens fit are reported.Results
Corneal flattening and hyperopic shifts in spherical equivalent refractive error (all p?<?0.001) after 28 nights of OK indicated myopic correction. Improvement in best corrected distance VA was measured after OK (right eye p?=?0.021; left eye p?=?0.014). Although there was no significant change in mean distance and near phorias and stereoacuity scores after OK compared to BL, there was a significant reduction in standard deviation (SD) and range of data (distance p?=?0.01; near p?=?0.02; stereoacuity p?<?0.001). While there appeared to be an improvement in distance accommodative facility after OK, this failed to reach statistical significance (p?=?0.053). Furthermore, there was no change in AC/A gradients with ±1 D and ±2 D lenses after OK compared to BL.Conclusions
Binocular vision remained unchanged after OK, although variability of phoria and stereoacuity measures reduced. This suggests that OK improves or maintains accommodative and binocular vision function in young adult myopes who achieve good vision with OK. Myopes with phorias outside normal ranges and/or poor distance accommodative facility may benefit most with OK, in binocular and accommodative function. 相似文献33.
Aquilanti L Garofalo C Osimani A Silvestri G Vignaroli C Clementi F 《Journal of food protection》2007,70(3):557-565
The transfer via the food chain from animals to humans of microbes that are resistant to antimicrobial agents is of increasing concern. To determine the contributions of nonpathogenic microflora to the occurrence and spread of antibiotic resistance (AR) genes in the food chain, 123 lactic acid bacteria were isolated from 29 samples of raw and processed pork and chicken meat products that had previously tested positive for one or more AR genes that encode clinically relevant ARs: tet(M), tet(O), tet(K), erm(A), erm(B), erm(C), aac (6')-Ie aph (2")-Ia, mecA, and blaZ. All of the isolates were initially tested for their AR gene profiles by PCR. The 59 isolates carrying a tet, erm, or blaZ gene were taken through molecular identification, analyzed by determination of the MIC, and subjected to genetic fingerprinting. Lactococcus garvieae was the predominant species (28 isolates), followed by Lactobacillus plantarum (11 isolates) and L. salivarius (6 isolates), whereas Lactococcus lactis subsp. lactis, Lactobacillus johnsonii, L. reuteri, L. crispatus, and L. brevis were identified at lower frequencies. The tet(M) and erm(B) genes were the most frequently detected. Assessment of multiple resistances in 18 tet positive (tet+) isolates revealed that tet(M) plus erm(B) and tet(K) plus erm(B) were the most frequent AR gene patterns. Partial sequencing of the tet(M) open reading frame of three selected strains showed high sequence similarities (> 99%) with tet(M) genes previously found in human pathogens (Listeria monocytogenes and Neisseria meningitidis). Southern hybridization with plasmid profiles revealed these strains contained tet(M)-carrying plasmids. 相似文献
34.
Effect of montmorillonite clay addition on the morphological and physical properties of Jatropha curcas L. and Glycine max L. protein concentrate films 下载免费PDF全文
Alex Osorio‐Ruiz Javier Solorza‐Feria Bor‐Sen Chiou Delilah F. Wood Tina G. Williams Roberto J. Avena‐Bustillos Alma‐Leticia Martínez‐Ayala 《应用聚合物科学杂志》2017,134(7)
Protein concentrates from jatropha (JPC) and soy seeds (SPC) were obtained by solubilization and acid precipitation of proteins. JPC and SPC films were prepared by the casting method, using two different montmorillonite (MMT) clay concentrations and plasticized with glycerol. Film properties were evaluated by scanning electron microscopy, transmission electron microscopy, X‐ray diffraction (XRD), Fourier transform infrared spectroscopy, thermogravimetric analysis, tensile properties, water retention, and water vapor transmission rate (WVRT). Typical tactoid microcomposite structures were found to be heterogeneously dispersed in the films containing MMT. A small XRD peak was found in films with MMT. Slight improvements in thermal stability and tensile strength were observed in the films with MMT. Reductions in water retention and WVRT were obtained when MMT was added into the films. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44459. 相似文献
35.
Tina M. Briere Marcel H. F. Sluiter Vijay Kumar Yoshiyuki Kawazoe 《Bulletin of Materials Science》2003,26(1):115-116
The geometries of several Mn clusters in the size range Mn13-Mn{on23} are studied via the generalized gradient approximation to density functional theory. For the 13-and 19-atom clusters, the
icosahedral structures are found to be most stable, while for the 15-atom cluster, the bcc structure is more favoured. The
clusters show ferrimagnetic spin configurations. 相似文献
36.
Daniela Drescher Ingrid Zeise Heike Traub Peter Guttmann Stephan Seifert Tina Büchner Norbert Jakubowski Gerd Schneider Janina Kneipp 《Advanced functional materials》2014,24(24):3765-3775
By adding a gold core to silica nanoparticles (BrightSilica), silica‐like nanoparticles are generated that, unlike unmodified silica nanoparticles, provide three types of complementary information to investigate the silica nano‐biointeraction inside eukaryotic cells in situ. Firstly, organic molecules in proximity of and penetrating into the silica shell in live cells are monitored by surface‐enhanced Raman scattering (SERS). The SERS data show interaction of the hybrid silica particles with tyrosine, cysteine and phenylalanine side chains of adsorbed proteins. Composition of the biomolecular corona of BrightSilica nanoparticles differs in fibroblast and macrophage cells. Secondly, quantification of the BrightSilica nanoparticles using laser ablation inductively coupled plasma mass spectrometry (LA‐ICP‐MS) micromapping indicates a different interaction of silica nanoparticles compared to gold nanoparticles under the same experimental conditions. Thirdly, the metal cores allow the investigation of particle distribution and interaction in the cellular ultrastructure by cryo nanoscale X‐ray tomography (cryo‐XT). In 3D reconstructions the assumption is confirmed that BrightSilica nanoparticles enter cells by an endocytotic mechanism. The high SERS intensities are explained by the beneficial plasmonic properties due to agglomeration of BrightSilica. The results have implications for the development of multi‐modal qualitative and quantitative characterization in comparative nanotoxicology and bionanotechnology. 相似文献
37.
Farah Perveen Mughal Ann Christina Bergmann Ha Uyen Buu Huynh Sarah Hyllekvist Jrgensen Inaam Mansha Meliha Kesmez Patrick Mark Schürch Alexandre Pierre Andr Theocharides Paul Robert Hansen Tina Friis Morten Orebo Holmstrm Evaldas Ciplys Rimantas Slibinskas Peter Hjrup Gunnar Houen Nicole Hartwig Trier 《International journal of molecular sciences》2022,23(12)
Myeloproliferative Neoplasms (MPNs) constitute a group of rare blood cancers that are characterized by mutations in bone marrow stem cells leading to the overproduction of erythrocytes, leukocytes, and thrombocytes. Mutations in calreticulin (CRT) genes may initiate MPNs, causing a novel variable polybasic stretch terminating in a common C-terminal sequence in the frameshifted CRT (CRTfs) proteins. Peptide antibodies to the mutated C-terminal are important reagents for research in the molecular mechanisms of MPNs and for the development of new diagnostic assays and therapies. In this study, eight peptide antibodies targeting the C-terminal of CRTfs were produced and characterised by modified enzyme-linked immunosorbent assays using resin-bound peptides. The antibodies reacted to two epitopes: CREACLQGWTE for SSI-HYB 385-01, 385-02, 385-03, 385-04, 385-07, 385-08, and 385-09 and CLQGWT for SSI-HYB 385-06. For the majority of antibodies, the residues Cys1, Trp9, and Glu11 were essential for reactivity. SSI-HYB 385-06, with the highest affinity, recognised recombinant CRTfs produced in yeast and the MARIMO cell line expressing CRTfs when examined in Western immunoblotting. Moreover, SSI-HYB 385-06 occasionally reacted to CRTfs from MPN patients when analysed by flow cytometry. The characterized antibodies may be used to understand the role of CRTfs in the pathogenesis of MPNs and to design and develop new diagnostic assays and therapeutic targets. 相似文献
38.
Clausnitzer T Limpert J Zöllner K Zellmer H Fuchs HJ Kley EB Tünnermann A Jupé M Ristau D 《Applied optics》2003,42(34):6934-6938
We report on highly efficient transmission gratings in fused silica with a grating period of 800 nm generated by electron-beam lithography. At a wavelength of 1060 nm, 95% diffraction efficiency is achieved under Littrow conditions. The damage threshold, extremely enhanced compared with conventional gold-coated diffraction gratings, makes these gratings the key elements in high average power (>100 W) femtosecond fiber chirped-pulse amplification systems. 相似文献
39.
Zinc supplementation induces regulatory T cells by inhibition of Sirt‐1 deacetylase in mixed lymphocyte cultures 下载免费PDF全文
40.
Moser DP Fredrickson JK Geist DR Arntzen EV Peacock AD Li SM Spadoni T McKinley JP 《Environmental science & technology》2003,37(22):5127-5134
Biogeochemical processes within riverbed hyporheic zones (HZ) can potentially impact the fate and transport of contaminants. We evaluated a modified freeze core technique for the collection of intact cobble-bed samples from the Columbia River HZ along a stretch of the Hanford Reach in Washington State and investigated microbiological and geochemical parameters of corresponding frozen and unfrozen samples. During three sampling periods (March, May, and November 2000), relatively high numbers of viable aerobic heterotrophic bacteria were recovered from both unfrozen (10(6)-10(7) cfu/g) and frozen samples (10(5)-10(6) cfu/g). Relatively large populations of sulfate-, nitrate-, and iron-reducing bacteria were present, and significant concentrations of acid-volatile sulfide were measured in some samples, indicating that anoxic regions exist within this zone. Cr(VI), a priority groundwater pollutant on adjacent U.S. Department of Energy lands, was probably removed from solution in HZ samples by a combination of microbial activity and chemical reduction, presumably via products of anaerobic microbial metabolism. These results suggest that biogeochemical processes in the Columbia River HZ may contribute to the natural attenuation of Cr(VI). Although freezing modestly diminished recovery of viable bacteria, freeze core techniques proved reliable for the collection of intact hyporheic sediments. 相似文献