全文获取类型
收费全文 | 2744篇 |
免费 | 105篇 |
国内免费 | 26篇 |
专业分类
电工技术 | 37篇 |
综合类 | 19篇 |
化学工业 | 526篇 |
金属工艺 | 59篇 |
机械仪表 | 40篇 |
建筑科学 | 74篇 |
矿业工程 | 7篇 |
能源动力 | 63篇 |
轻工业 | 234篇 |
水利工程 | 26篇 |
石油天然气 | 23篇 |
武器工业 | 2篇 |
无线电 | 228篇 |
一般工业技术 | 265篇 |
冶金工业 | 1027篇 |
原子能技术 | 13篇 |
自动化技术 | 232篇 |
出版年
2023年 | 8篇 |
2022年 | 34篇 |
2021年 | 71篇 |
2020年 | 44篇 |
2019年 | 32篇 |
2018年 | 52篇 |
2017年 | 51篇 |
2016年 | 40篇 |
2015年 | 51篇 |
2014年 | 58篇 |
2013年 | 118篇 |
2012年 | 72篇 |
2011年 | 98篇 |
2010年 | 86篇 |
2009年 | 97篇 |
2008年 | 88篇 |
2007年 | 102篇 |
2006年 | 77篇 |
2005年 | 67篇 |
2004年 | 64篇 |
2003年 | 83篇 |
2002年 | 72篇 |
2001年 | 49篇 |
2000年 | 41篇 |
1999年 | 52篇 |
1998年 | 366篇 |
1997年 | 209篇 |
1996年 | 174篇 |
1995年 | 89篇 |
1994年 | 75篇 |
1993年 | 77篇 |
1992年 | 20篇 |
1991年 | 21篇 |
1990年 | 20篇 |
1989年 | 21篇 |
1988年 | 16篇 |
1987年 | 19篇 |
1986年 | 18篇 |
1985年 | 14篇 |
1984年 | 6篇 |
1983年 | 8篇 |
1982年 | 4篇 |
1981年 | 9篇 |
1980年 | 12篇 |
1979年 | 11篇 |
1978年 | 7篇 |
1977年 | 17篇 |
1976年 | 31篇 |
1971年 | 7篇 |
1943年 | 2篇 |
排序方式: 共有2875条查询结果,搜索用时 46 毫秒
1.
Optimization and Engineering - 相似文献
2.
Laís D. Silva Fernanda C. Puosso Viviane O. Soares Oscar Peitl Filho Simone do R.F. Sabino Francisco C. Serbena Murilo C. Crovace Edgar D. Zanotto 《Ceramics International》2021,47(13):18720-18731
Bioactive glasses and glass-ceramics (GCs) effectively regenerate bone tissue, however most GCs show improved mechanical properties. In this work, we developed and tested a rarely studied bioactive glass composition (24.4K2O-26.9CaO-46.1SiO2-2.6P2O5 mol%, identified as 45S5-K) with different particle sizes and heating rates to obtain a sintered GC that combines good fracture strength, low elastic modulus, and bioactivity. We analyzed the influence of the sintering processing conditions in the elastic modulus, Vickers microhardness, density, and crystal phase formation in the GC. The best GC shows improved properties compared with its parent glass. This glass achieves a good densification degree with a two-step viscous flow sintering approach and the resulting GC shows as high bioactivity as that of the standard 45S5 Bioglass®. Furthermore, the GC elastic modulus (56 GPa) is relatively low, minimizing stress shielding. Therefore, we unveiled the glass sintering behavior with concurrent crystallization of this complex bioactive glass composition and developed a potential GC for bone regeneration. 相似文献
3.
Stefano Mariani Antonino Amedeo La Mattina Alessandro Paghi Lucanos Strambini Giuseppe Barillaro 《Advanced functional materials》2021,31(26):2100774
Here, a fluoride-assisted route for the controlled in-situ synthesis of metal nanoparticles (NPs) (i.e., AgNPs, AuNPs) on polydimethylsiloxane (PDMS) is reported. The size and coverage of the NPs on the PDMS surface are modulated with time and over space during the synthetic process, leveraging the improved yield (10×) and faster kinetics (100×) of NP formation in the presence of F− ions, compared to fluoride-free approaches. This enables the maskless preparation of both linear and step gradients and patterns of NPs in 1D and 2D on the PDMS surface. As an application in flexible plasmonics/photonics, continuous and step-wise spatial modulations of the plasmonic features of PDMS slabs with 1D and 2D AgNP gradients on the surface are demonstrated. An excellent spatially resolved tuning of key optical parameters, namely, optical density from zero to 5 and extinction ratio up to 100 dB, is achieved with AgNP gradients prepared in AgF solution for 12 minutes; the performance are comparable to those of commercial dielectric/interference filters. When used as a rejection filter in optical fluorescence microscopy, the AgNP-PDMS slabs are able to reject the excitation laser at 405 nm and retain the green fluorescence of microbeads (100 µm) used as test cases. 相似文献
4.
5.
Maria Grazia Basanisi Gianfranco La Bella Gaia Nobili Rosa Coppola Annita Maria Damato Maria Assunta Cafiero Giovanna La Salandra 《International Journal of Food Science & Technology》2020,55(3):1145-1150
The authenticity and traceability of meat products are issues of primary importance to ensure food safety. Unfortunately, food adulteration (e.g. the addition of inexpensive cuts to minced meat products) and mislabelling (e.g. the inclusion of meat from species other than those declared) happens frequently worldwide. The aim of this study was to apply a droplet digital PCR assay for the detection and quantification (copies μL−1) of the beef, pork, horse, sheep, chicken and turkey in meat products. The analysis conducted on commercial meat showed the presence of traces of DNA from other animal species than those declared. We show that the method is highly sensitive, specific and accurate (accuracy = 100%). This method could be adopted by competent food safety authorities to verify compliance with the labelling of meat products and to ensure quality and safety throughout the meat supply chain, from primary production to consumption. 相似文献
6.
7.
QY Liu AE Schaffner YH Chang K Vaszil JL Barker 《Canadian Metallurgical Quarterly》1997,33(6):848-864
Embryonic rat hippocampal neurons were cultured in a serum-free defined medium (MEM/N3) either directly on poly-D-lysine (PDL) or on a confluent monolayer of postnatal cortical astrocytes, C6 glioma cells, or Rat2 fibroblasts. Neurons on PDL were grown in MEM/N3 or in MEM/N3 conditioned for 24 h by astrocytes or C6 cells. Membrane capacitance (Cm) and gamma-aminobutyric acid (GABA)-, glycine-, kainate-, and N-methyl-D-aspartate (NMDA)-induced currents were quantified using whole-cell patch-clamp recordings. Cm as well as the amplitude and the density of these currents in neurons cultured on astrocytes were significantly greater than those in neurons grown on PDL after 24 and 48 h. C6 cells mimicked astrocytes in promoting Cm and GABA-, glycine-, and NMDA-evoked, but not kainate-evoked, currents. Cm and currents in neurons grown on Rat2 cells were comparable to those in neurons on PDL. Astrocytes maintained in culture for 3 months were noticeably less effective than freshly prepared ones just grown to confluence. Suppression of spontaneous cytoplasmic Ca2+ (Ca[c]2+) elevations in astrocytes by 1,2-bis(2-aminophenoxy) ehane-N, N, N, N-tetraacetic acid acetoxymethyl ester (BAPTA-AM) loaded intracellularly blocked the observed modulatory effects. Medium conditioned by either astrocytes or C6 cells mimicked the effects of direct coculture of neurons on these cells in promoting Cm and amino acid-evoked currents. Inclusion of antagonists at GABA and glutamate receptors in coculture experiments blocked the observed effects. Thus, diffusible substances synthesized and/ or secreted by astrocytes in a Ca(c)2+-dependent manner can regulate neuronal growth and aminoacid receptor function, and these effects may involve neuronal GABA and glutamate receptors. 相似文献
8.
9.
E La Hey J de Vries CT Langerhorst GS Baarsma A Kijlstra 《Canadian Metallurgical Quarterly》1993,116(3):327-340
After reviewing the records of 111 patients with Fuchs' heterochromic iridocyclitis, we studied the therapy and prognosis of secondary glaucoma in 30 of these 111 patients (27%) who had glaucoma or could be considered glaucoma suspects. Maximal medical therapy was unsuccessful in 22 of the 30 patients (73%). Surgical intervention (mostly trabeculectomies, half with 5-fluorouracil) successfully controlled intraocular pressure (< or = 21 mm Hg with or without medication) in 13 of the 18 operated-on patients (72%) after a mean follow-up of 26 months. All successfully operated-on patients retained a visual acuity of 20/80 or better. We had favorable results, possibly because of modern surgical techniques (use of 5-fluorouracil, sodium hyaluronate) or earlier surgical intervention, or both. 相似文献
10.
A simple apparatus for elongational test of molten polymers is presented. Its realiability is demonstrated by means of stress growth in constant stretching rate experiments and relaxation test on a low density polyethylene sample. 相似文献