全文获取类型
收费全文 | 73599篇 |
免费 | 3386篇 |
国内免费 | 211篇 |
专业分类
电工技术 | 771篇 |
综合类 | 642篇 |
化学工业 | 11607篇 |
金属工艺 | 1105篇 |
机械仪表 | 1575篇 |
建筑科学 | 1915篇 |
矿业工程 | 459篇 |
能源动力 | 1204篇 |
轻工业 | 8216篇 |
水利工程 | 957篇 |
石油天然气 | 205篇 |
武器工业 | 5篇 |
无线电 | 3194篇 |
一般工业技术 | 8535篇 |
冶金工业 | 26288篇 |
原子能技术 | 300篇 |
自动化技术 | 10218篇 |
出版年
2024年 | 141篇 |
2023年 | 538篇 |
2022年 | 664篇 |
2021年 | 1095篇 |
2020年 | 855篇 |
2019年 | 945篇 |
2018年 | 1907篇 |
2017年 | 2080篇 |
2016年 | 2484篇 |
2015年 | 1890篇 |
2014年 | 1785篇 |
2013年 | 3189篇 |
2012年 | 4140篇 |
2011年 | 4463篇 |
2010年 | 2247篇 |
2009年 | 2207篇 |
2008年 | 2058篇 |
2007年 | 1937篇 |
2006年 | 1465篇 |
2005年 | 4001篇 |
2004年 | 3151篇 |
2003年 | 2621篇 |
2002年 | 1381篇 |
2001年 | 1132篇 |
2000年 | 608篇 |
1999年 | 966篇 |
1998年 | 7788篇 |
1997年 | 4871篇 |
1996年 | 3181篇 |
1995年 | 1837篇 |
1994年 | 1363篇 |
1993年 | 1415篇 |
1992年 | 341篇 |
1991年 | 394篇 |
1990年 | 373篇 |
1989年 | 352篇 |
1988年 | 376篇 |
1987年 | 303篇 |
1986年 | 264篇 |
1985年 | 247篇 |
1984年 | 141篇 |
1983年 | 121篇 |
1982年 | 172篇 |
1981年 | 238篇 |
1980年 | 257篇 |
1979年 | 96篇 |
1978年 | 145篇 |
1977年 | 706篇 |
1976年 | 1522篇 |
1975年 | 132篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
42.
43.
Ugur Gezer Ebru E. Y?rüker Metin Keskin Cemil Burak Kulle Yoganiranjana Dharuman Stefan Holdenrieder 《International journal of molecular sciences》2015,16(12):29654-29662
Circulating nucleic acids (CNAs) are under investigation as a liquid biopsy in cancer as potential non-invasive biomarkers, as stable structure in circulation nucleosomes could be valuable sources for detection of cancer-specific alterations in histone modifications. Our interest is in histone methylation marks with a focus on colorectal cancer, one of the leading cancers respective the incidence and mortality. Our previous work included the analysis of trimethylations of lysine 9 on histone 3 (H3K9me3) and of lysine 20 on histone 4 (H4K20me3) by chromatin immuno- precipitation-related PCR in circulating nucleosomes. Here we asked whether global immunologic measurement of histone marks in circulation could be a suitable approach to show their potential as biomarkers. In addition to H3K9me3 and H4K20me3 we also measured H3K27me3 in plasma samples from CRC patients (n = 63) and cancer free individuals (n = 40) by ELISA-based methylation assays. Our results show that of three marks, the amounts of H3K27me3 (p = 0.04) and H4K20me3 (p < 0.001) were significantly lower in CRC patients than in healthy controls. For H3K9me3 similar amounts were measured in both groups. Areas under the curve (AUC) in receiver operating characteristic (ROC) curves indicating the power of CRC detection were 0.620 for H3K27me3, 0.715 for H4K20me3 and 0.769 for the combination of both markers. In conclusion, findings of this preliminary study reveal the potential of blood-based detection of CRC by quantification of histone methylation marks and the additive effect of the marker combination. 相似文献
44.
Andrea Mariela Araya-Sibaja Valdir Soldi Carlos Eduardo Maduro Campos Simone Gonçalves Cardoso 《Drug development and industrial pharmacy》2015,41(5):851-858
Progesterone is a natural hormone steroid used in humans for several treatments and in livestock for artificial insemination, which exhibits two polymorphic forms at ambient conditions: form 1 and form 2. Form 2 is metastable and more soluble than form 1; however, it is not suitable to use as powder raw material because it transforms into form 1 by the effects of grinding. A polymorphic screening of progesterone based on polymer-induced heteronucleation method was performed as an alternative to prepare the metastable form. Polyvinyl alcohol, hydroxypropyl methylcellulose (HPMC), dextran, gelatin, polyisoprene (PI) and acrylonitrile-butadiene (NBR) copolymer were used. Crystals were prepared from 0.5, 10 and 40?mg/mL solutions in acetone at room temperature by solvent evaporation. The samples were characterized by X-ray powder diffraction, differential scanning calorimetry (DSC), scanning electron microcopy and attenuated total reflectance infrared Fourier transform spectroscopy. Form 1 was nucleated from 40?mg/mL solutions on the six polymers and from 10?mg/mL solutions on PI and NBR. The mixture of form 1 and form 2 was obtained from 10?mg/mL solution on HPMC, dextran and gelatin and from 0.5?mg/mL solution crystallizations. Therefore, the polymeric devices, which crystallized the metastable and more soluble polymorph (2) of progesterone, would be a promissory alternative for the pharmaceutical applications. 相似文献
45.
46.
47.
48.
49.
María Clara Verdi Constanza Melian Patricia Castellano Graciela Vignolo Mariana Blanco Massani 《International Journal of Food Science & Technology》2020,55(1):267-275
The effectiveness of antimicrobial mixtures against Listeria innocua 7, used as a L. monocytogenes surrogate, was investigated in broth and a food system. Synergistic effects were found for nisin (Nis), potassium sorbate (PS), calcium propionate (CP) and sodium lactate (SL), Nis + PS being the most effective binary mixture that exhibited listericidal activity in broth. To assess the effect of adding lactocin AL705 (AL705) to Nis + organic acid salt combinations, tridimensional isobolograms were generated. Sub-MIC combinations of the antimicrobials exerted bactericidal activity against L. innocua 7 after AL705 addition to the binary mixtures. However, when applied on Sardo cheese contaminated with L. innocua 7 (initial inoculum 4.45 ± 0.06 CFU g−1), only Nis + PS + AL705 produced count reductions respect to the control, reaching 3.04 ± 0.35 CFU g−1 counts after 15 days at 15 °C. Ternary combinations containing AL705 showed potential to reduce antimicrobial usages for L. innocua 7 inhibition. 相似文献
50.
Hierarchical micro-nanostructured albite-based glass-ceramic for high dielectric strength insulators
V. Fuertes M.J. Cabrera J. Seores D. Muñoz J.F. Fernández E. Enríquez 《Journal of the European Ceramic Society》2018,38(7):2759-2766
A novel glass-ceramic material based on albite type Na-rich feldspar has been synthesized by conventional ceramic process. High crystallinity, >94%?Vol.% is obtained by fast sintering which allows energy saving processing. Albite is the main crystalline phase and tetragonal SiO2 is a secondary phase. Electrical properties were examined by complex impedance, DC measurements, and dielectric breakdown test. Dielectric characterization shows a non-Debye type dielectric behavior with low dielectric constant, 4.6 at 1?MHz, low dielectric losses, (~10?3 at 1?MHz, and a large dielectric strength, ~60?kV/mm), that it is the largest value reported in ceramic insulators. Those dielectric properties are attained by the low glassy phase content in the samples and their unique micro-nanostructure. All these properties make this novel material a very promising candidate in the market of ceramic electrical insulator, highlighting for high-voltage applications. 相似文献