全文获取类型
收费全文 | 5113篇 |
免费 | 255篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 52篇 |
综合类 | 26篇 |
化学工业 | 1254篇 |
金属工艺 | 149篇 |
机械仪表 | 99篇 |
建筑科学 | 171篇 |
矿业工程 | 22篇 |
能源动力 | 63篇 |
轻工业 | 749篇 |
水利工程 | 54篇 |
石油天然气 | 10篇 |
无线电 | 257篇 |
一般工业技术 | 819篇 |
冶金工业 | 1098篇 |
原子能技术 | 13篇 |
自动化技术 | 534篇 |
出版年
2023年 | 51篇 |
2022年 | 201篇 |
2021年 | 242篇 |
2020年 | 94篇 |
2019年 | 102篇 |
2018年 | 129篇 |
2017年 | 142篇 |
2016年 | 184篇 |
2015年 | 157篇 |
2014年 | 161篇 |
2013年 | 254篇 |
2012年 | 259篇 |
2011年 | 279篇 |
2010年 | 186篇 |
2009年 | 185篇 |
2008年 | 223篇 |
2007年 | 152篇 |
2006年 | 148篇 |
2005年 | 113篇 |
2004年 | 90篇 |
2003年 | 84篇 |
2002年 | 79篇 |
2001年 | 65篇 |
2000年 | 36篇 |
1999年 | 62篇 |
1998年 | 355篇 |
1997年 | 187篇 |
1996年 | 155篇 |
1995年 | 86篇 |
1994年 | 89篇 |
1993年 | 77篇 |
1992年 | 17篇 |
1991年 | 32篇 |
1990年 | 18篇 |
1989年 | 46篇 |
1988年 | 18篇 |
1987年 | 31篇 |
1986年 | 20篇 |
1985年 | 34篇 |
1984年 | 26篇 |
1983年 | 28篇 |
1982年 | 32篇 |
1981年 | 19篇 |
1980年 | 21篇 |
1979年 | 23篇 |
1977年 | 29篇 |
1976年 | 72篇 |
1919年 | 18篇 |
1911年 | 16篇 |
1910年 | 23篇 |
排序方式: 共有5370条查询结果,搜索用时 15 毫秒
51.
Significant differences exist between the quality characteristics of meat obtained from 27 sheep, Angora and Boer goat carcases, when compared. Sheep meat showed greater drip loss than goat meat and was more juicy than that of Angora and Boer goat meat. In general, Angora goat meat was found to be more juicy than Boer goat meat. Drip loss increased significantly with increased animal age. Meat of younger animals (no permanent incisors) was more juicy (initial and sustained) than that of older animals (7–8 permanent incisors). This was irrespective of whether it was obtained from sheep, Angora or Boer goats and was confirmed by the expressible moisture measurements. Higher drip, evaporation and total cooking loss were reported when carcases had increased fat content. With increasing fatness of carcases, the juiciness of the cooked cuts decreased and the expressible moisture content of the meat increased. 相似文献
52.
The quality characteristics of 27 Angora goats, Boer goats and sheep carcases were compared. Significant differences exist between the quality characteristics of sheep meat and Angora or Boer goat meat. Sheep meat has a more intense aroma, it is more tender, contains less fibrous tissue residue and the species flavour is more pronounced (typical) than that of Angora and Boer goat meat. In general, goat meat was found to be significantly different to sheep meat, the Angora to a lesser extent, however, than the Boer goat. This study confirms the fact that the meat of younger animals is more tender, contains less fibrous tissue residue and the species flavour is less typical than that of older animals. This was irrespective of whether it was obtained from sheep, Angora or Boer goat. With increasing fatness of carcases, the tenderness and species flavour of the cooked cuts increased significantly. 相似文献
53.
N. Nordell A. Schöner K. Rottner P. O. Å. Persson Q. Wahab L. Hultman M. K. Linnarsson E. Olsson 《Journal of Electronic Materials》1998,27(7):833-837
Implantation of B has been performed into an epitaxially grown layer of 6H SiC, at two different B concentrations, 2×1016 cm−3 and 2×1018 cm−3. Subsequently, an epitaxial layer was regrown on the B implanted layer. The samples were investigated by transmission electron
microscopy (TEM) and secondary ion mass spectrometry (SIMS). In the highly B-doped layers plate-like defects were found, associated
with large strain fields, and an increased B concentration. These defects were stable at the originally implanted region during
regrowth and at anneal temperatures up to 1700°C. In the samples implanted with the lower B concentration, no crystal defects
could be detected by TEM. No threading dislocations or other defects were observed in the regrown epitaxial layer, which shows
the possibility to grow a layer with high crystalline quality on B implanted 6H SiC. By SIMS, it was found that B piles up
at the interface to the regrown layer, which could be explained by enhanced diffusion from an increased concentration of point
defects created by implantation damage in the region. B is also spread out into the original crystal and in the regrown layer
at a concentration of below 2×1016 cm−3, with a diffusion constant estimated to 1.3×10−12 cm2s−1. This diffusion is most probably not driven by implantation damage, but by intrinsic defects in the grown crystal. Our investigation
shows that the combination of implantation and subsequent regrowth techniques could be used in SiC for building advanced device
structures, with the crystal quality in the regrown layer not being deteriorated by crystal defects in the implanted region.
A device process using B implantation and subsequent regrowth could on the other hand be limited by the diffusion of B. 相似文献
54.
Denis Schütz Marco Deluca Werner Krauss Antonio Feteira Tim Jackson Klaus Reichmann 《Advanced functional materials》2012,22(11):2285-2294
Bismuth sodium titanate (BNT)‐derived materials have seen a flurry of research interest in recent years because of the existence of extended strain under applied electric fields, surpassing that of lead zirconate titanate (PZT), the most commonly used piezoelectric. The underlying physical and chemical mechanisms responsible for such extraordinary strain levels in BNT are still poorly understood, as is the nature of the successive phase transitions. A comprehensive explanation is proposed here, combining the short‐range chemical and structural sensitivity of in situ Raman spectroscopy (under an applied electric field and temperature) with macroscopic electrical measurements. The results presented clarify the causes for the extended strain, as well as the peculiar temperature‐dependent properties encountered in this system. The underlying cause is determined to be mediated by the complex‐like bonding of the octahedra at the center of the perovskite: a loss of hybridization of the 6s2 bismuth lone pair interacting with the oxygen p‐orbitals occurs, which triggers both the field‐induced phase transition and the loss of macroscopic ferroelectric order at the depolarization temperature. 相似文献
55.
Aleksandra Panajotovi Nikola Sekulovi Aleksandra Cvetkovi Daniela Milovi 《International Journal of Communication Systems》2020,33(14)
In this paper, the closed‐form expressions for outage probability, channel capacity, and average symbol error probability are derived for amplify‐and‐forward multihop relay network. Based on approximation of multihop relay by dual‐hop relay systems, the analytical expressions are obtained for the case when maximal ratio combining technique is employed at each relay while destination node uses selection combining technique. The impact of system and channel parameters on the system performances is investigated, and numerical results are graphically presented. The derived analytical expressions are verified by numerical simulation. 相似文献
56.
The design and first measuring results of an ultra-low power 12 bit successive-approximation ADC for autonomous multi-sensor systems are presented. The comparator and the DAC are optmised for low power consumption. The power consumption is 0.52 μW from a 1.2 V supply with a sample clock of 3.125 kHz and 0.85 μW at 6.25 kHz. This gives 136 pJ per conversion or 66 fJ per conversion step. As per authors’ knowledge, 66 fJ per conversion step is the best reported so far.The ADC was realised in the NXP CMOS 0.14 μm technology; the area was 0.35 mm2. Only four metal layers were used in order to allow 3D integration of the sensors. 相似文献
57.
Memristive valence change memory (VCM) cells show a strong non-linearity in the switching kinetics which is induced by a temperature increase. In this respect, thermal crosstalk can be observed in highly integrated crossbar arrays which may impact the resistance state of adjacent devices. Additionally, due to the thermal capacitance, a VCM cell can remain thermally active after a pulse and thus influence the temperature conditions for a possible subsequent pulse. By using a finite element model of a crossbar array, it is shown that spatio-temporal thermal correlations can occur and are capable of affecting the resistive state of adjacent cells. This new functional behavior can potentially be used for future neuromorphic computing applications. 相似文献
58.
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
59.
C. Schönbauer Dipl.-Ing. 《e & i Elektrotechnik und Informationstechnik》2003,120(10):304-306
The new law for the support of electricity produced by renewable sources in Austria (Ökostromgesetz) which came into force with the beginning of 2003, shows its impacts already after the first months. Investments into wind power have increased considerably. These will be accompanied by activities for electricity production by biomass and biogas. The 4%-target quota will probably be reached earlier than the 2008 target period of the law. 相似文献
60.
Vittoria Bruni Daniela De Canditiis Domenico Vitulano 《Signal, Image and Video Processing》2014,8(7):1199-1209
This paper presents SUVEHP (speed up of video enhancement based on human perception), a human perception-based model oriented to reduce the computational time of digital video restoration. In particular, two specific hypothesis tests able to classify degraded frame regions are proposed. Classification is performed in agreement with regions visual significance in order to enable or inhibit motion compensated enhancement. The level of the proposed hypothesis tests is theoretically assessed. Moreover, extensive experimental results on video sequences affected by additive Gaussian noise show that SUVEHP speeds up some standard motion compensated denoisers up to 60%, preserving or even slightly increasing both the objective and subjective visual quality of the restored sequences. 相似文献