全文获取类型
收费全文 | 3500篇 |
免费 | 29篇 |
专业分类
电工技术 | 9篇 |
化学工业 | 153篇 |
金属工艺 | 7篇 |
机械仪表 | 16篇 |
建筑科学 | 30篇 |
矿业工程 | 1篇 |
能源动力 | 14篇 |
轻工业 | 69篇 |
水利工程 | 2篇 |
无线电 | 177篇 |
一般工业技术 | 138篇 |
冶金工业 | 2808篇 |
原子能技术 | 18篇 |
自动化技术 | 87篇 |
出版年
2021年 | 14篇 |
2020年 | 8篇 |
2019年 | 12篇 |
2018年 | 7篇 |
2017年 | 15篇 |
2016年 | 12篇 |
2015年 | 8篇 |
2014年 | 9篇 |
2013年 | 23篇 |
2012年 | 29篇 |
2011年 | 34篇 |
2010年 | 27篇 |
2009年 | 27篇 |
2008年 | 22篇 |
2007年 | 29篇 |
2006年 | 23篇 |
2005年 | 26篇 |
2004年 | 27篇 |
2003年 | 16篇 |
2002年 | 22篇 |
2001年 | 19篇 |
2000年 | 18篇 |
1999年 | 86篇 |
1998年 | 863篇 |
1997年 | 528篇 |
1996年 | 313篇 |
1995年 | 222篇 |
1994年 | 130篇 |
1993年 | 183篇 |
1992年 | 35篇 |
1991年 | 40篇 |
1990年 | 37篇 |
1989年 | 33篇 |
1988年 | 31篇 |
1987年 | 43篇 |
1986年 | 22篇 |
1985年 | 33篇 |
1984年 | 6篇 |
1983年 | 19篇 |
1982年 | 14篇 |
1981年 | 44篇 |
1980年 | 29篇 |
1979年 | 10篇 |
1978年 | 18篇 |
1977年 | 102篇 |
1976年 | 177篇 |
1975年 | 13篇 |
1973年 | 9篇 |
1971年 | 7篇 |
1955年 | 7篇 |
排序方式: 共有3529条查询结果,搜索用时 0 毫秒
991.
Thomas Connolly Richard C. Smith Yenny Hernandez Yurii Gun'ko Jonathan N. Coleman J. David Carey 《Small (Weinheim an der Bergstrasse, Germany)》2009,5(7):826-831
The electron field‐emission (FE) characteristics of functionalized single‐walled carbon‐nanotube (CNT)–polymer composites produced by solution processing are reported. It is shown that excellent electron emission can be obtained by using as little as 0.7% volume fraction of nanotubes in the composite. Furthermore by tailoring the nanotube concentration and type of polymer, improvements in the charge transfer through the composite can be obtained. The synthesis of well‐dispersed randomly oriented nanotube–polymer composites by solution processing allows the development of CNT‐based large area cathodes produced using a scalable technology. The relative insensitivity of the cathode's FE characteristics to the electrical conductivity of the composite is also discussed. 相似文献
992.
Ahmad Al Shami Ahmad Lotfi Simeon Coleman 《Soft Computing - A Fusion of Foundations, Methodologies and Applications》2013,17(12):2349-2364
This article is proposing an alternative approach to develop Intelligent Synthetic Composite Indicators (ISCI). The suggested approach utilizes Fuzzy Proximity Knowledge Mining technique to build the qualitative taxonomy initially, and then Fuzzy c-means is employed to form the new composite indicators. A fully worked application is presented. The application uses Information and Communication Technology real variables to form a new unified ICT index, illustrating the method of construction for ISCI. The weighting and aggregation results obtained were compared against Principal Component Analysis, Factor Analysis and the Geometric mean to weight and aggregate synthetic composite indicators. This study also compares and contrasts two special Fuzzy c-means techniques that is, the Optimal Completion Strategy and the Nearest Prototype Strategy to impute missing values. The results are compared against statistical imputation techniques. The validity and robustness of all techniques are evaluated using Monte Carlo simulation. The results obtained suggest a novel, intelligent and non-biased method of building future composite indicators. 相似文献
993.
994.
995.
Khalid Nawaz Umar Khan Noaman Ul-Haq Peter May Arlene O’Neill Jonathan N. Coleman 《Carbon》2012,50(12):4489-4494
We have covalently functionalized graphene oxide (GO) with octadecylamine (ODA) to form GO–ODA. This material can be dispersed in tetrahydrofuran (THF) and subsequently formed into composites with polymers such as thermoplastic polyurethane (TPU). We have characterized the mechanical properties of composites of GO–ODA in TPU. No increase in stiffness was observed at loading levels below 2.5 vol%. Reinforcement appeared to start sharply at this volume fraction and subsequently increased as a power law with increasing volume fraction. This behavior is typical of percolation and shows that the low-strain stress is not increased until the functionalized graphene flakes form a percolating network. Slightly different behavior is observed for properties related to material failure. The ultimate tensile strength increased linearly with graphene content up to the percolation threshold before subsequently falling off. Similarly the strain at break was constant below the percolation threshold but fell off dramatically above it. This work shows the importance of network formation in the reinforcement of elastomeric materials. 相似文献
996.
We report measurements of the specific heat of helium-4 confined to very uniform 8-micron diameter cylinders and to 0.26-micron diameter Anopore cylinders in the temperature region near the lambda point. The data allow improved tests of the emerging theory of finite size phenomena and cross-over to lower dimensional states. We find generally good agreement with scaling using exponents derived by renormalization methods. We also find reasonable agreement with more detailed numerical calculations of cross-over behavior with explicit inclusion of boundary conditions. However, in the region near the peak, the 8-micron data do not scale well relative to Anopore. We also compare the results with previous work on 1-dimensional systems. 相似文献
997.
PJ Cooper K Awadzi EA Ottesen D Remick TB Nutman 《Canadian Metallurgical Quarterly》1999,179(3):738-742
To investigate the role of eosinophil activation and sequestration in the development and severity of adverse reactions after the treatment of Onchocerca volvulus infection, 40 O. volvulus-infected Ghanaians were randomized to receive placebo or standard- or high-dose ivermectin. Subjects were examined for typical physiologic and clinical events before and up to 48 h after treatment. Plasma samples were tested for interleukin (IL)-5 and eosinophil degranulation products (e.g., eosinophil-derived neurotoxin, EDN). After treatment, peripheral eosinophil counts declined in ivermectin-treated groups (P<.001), whereas circulating levels of IL-5 (P<.01) and EDN (P<.05) increased. Cumulative levels of IL-5 and EDN correlated with reaction scores (P<.01). High-dose ivermectin was associated with more-severe reactions, more-profound eosinopenia, and higher circulating levels of IL-5 and EDN, compared with the standard dose. These results suggest that eosinophil sequestration and activation/degranulation are associated with the initiation and severity of ivermectin-associated adverse reactions. 相似文献
998.
999.
Nichola J. Coleman Samantha P. Lewis Andrew P. Mendham Vivek Trivedi 《Journal of Porous Materials》2010,17(6):747-753
Zirconium umbite, K2ZrSi3O9·H2O, is a microporous framework ion exchanger whose potential as a carrier for Zn2+ ions in antimicrobial formulations has not yet been investigated. Accordingly, batch Zn2+-exchange kinetics of synthetic zirconium umbite (K-UM) and the subsequent antimicrobial action of the zinc-bearing phase
(Zn-UM) against Staphylococcus aureus and Escherichia coli are reported. Nonstoicheiometric over-exchange of Zn2+ for K+ was observed and attributed to hydrolysis and complexation reactions of Zn2+ within the umbite framework. The exchange process, which was described by a simple pseudo-first-order model (k
1 = 2.69 × 10−4 min−1, R
2 = 0.992), did not achieve equilibrium within 120 h at 25 °C, by which time the uptake of zinc was found to be 1.04 mmol g−1. The minimal bactericidal concentrations of Zn-UM for E. coli and S. aureus were found to be >10 g cm3 and <1.0 g cm3, respectively. 相似文献
1000.
Evaluation of a droplet digital polymerase chain reaction format for DNA copy number quantification 总被引:3,自引:0,他引:3
Pinheiro LB Coleman VA Hindson CM Herrmann J Hindson BJ Bhat S Emslie KR 《Analytical chemistry》2012,84(2):1003-1011
Droplet digital polymerase chain reaction (ddPCR) is a new technology that was recently commercialized to enable the precise quantification of target nucleic acids in a sample. ddPCR measures absolute quantities by counting nucleic acid molecules encapsulated in discrete, volumetrically defined, water-in-oil droplet partitions. This novel ddPCR format offers a simple workflow capable of generating highly stable partitioning of DNA molecules. In this study, we assessed key performance parameters of the ddPCR system. A linear ddPCR response to DNA concentration was obtained from 0.16% through to 99.6% saturation in a 20,000 droplet assay corresponding to more than 4 orders of magnitude of target DNA copy number per ddPCR. Analysis of simplex and duplex assays targeting two distinct loci in the Lambda DNA genome using the ddPCR platform agreed, within their expanded uncertainties, with values obtained using a lower density microfluidic chamber based digital PCR (cdPCR). A relative expanded uncertainty under 5% was achieved for copy number concentration using ddPCR. This level of uncertainty is much lower than values typically observed for quantification of specific DNA target sequences using currently commercially available real-time and digital cdPCR technologies. 相似文献