全文获取类型
收费全文 | 527664篇 |
免费 | 7233篇 |
国内免费 | 1470篇 |
专业分类
电工技术 | 9671篇 |
综合类 | 530篇 |
化学工业 | 79264篇 |
金属工艺 | 20012篇 |
机械仪表 | 15233篇 |
建筑科学 | 12718篇 |
矿业工程 | 2271篇 |
能源动力 | 14606篇 |
轻工业 | 47257篇 |
水利工程 | 5223篇 |
石油天然气 | 9336篇 |
武器工业 | 37篇 |
无线电 | 60177篇 |
一般工业技术 | 102092篇 |
冶金工业 | 103958篇 |
原子能技术 | 10592篇 |
自动化技术 | 43390篇 |
出版年
2022年 | 3191篇 |
2021年 | 4953篇 |
2020年 | 3499篇 |
2019年 | 4574篇 |
2018年 | 7847篇 |
2017年 | 7637篇 |
2016年 | 7971篇 |
2015年 | 5595篇 |
2014年 | 9311篇 |
2013年 | 24176篇 |
2012年 | 14728篇 |
2011年 | 20251篇 |
2010年 | 15880篇 |
2009年 | 17783篇 |
2008年 | 18196篇 |
2007年 | 17859篇 |
2006年 | 15568篇 |
2005年 | 14290篇 |
2004年 | 13658篇 |
2003年 | 13475篇 |
2002年 | 12696篇 |
2001年 | 12883篇 |
2000年 | 11918篇 |
1999年 | 12649篇 |
1998年 | 32995篇 |
1997年 | 23003篇 |
1996年 | 17519篇 |
1995年 | 13095篇 |
1994年 | 11337篇 |
1993年 | 11016篇 |
1992年 | 7941篇 |
1991年 | 7445篇 |
1990年 | 7283篇 |
1989年 | 7046篇 |
1988年 | 6490篇 |
1987年 | 5783篇 |
1986年 | 5676篇 |
1985年 | 6285篇 |
1984年 | 5921篇 |
1983年 | 5187篇 |
1982年 | 4916篇 |
1981年 | 4984篇 |
1980年 | 4719篇 |
1979年 | 4632篇 |
1978年 | 4427篇 |
1977年 | 5358篇 |
1976年 | 7005篇 |
1975年 | 3802篇 |
1974年 | 3560篇 |
1973年 | 3672篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
51.
Thin Film Thermoelectric Metal–Organic Framework with High Seebeck Coefficient and Low Thermal Conductivity 下载免费PDF全文
52.
53.
Electrochemical impedance spectroscopy (EIS), anodic polarization and scanning electron microscopy techniques were used to investigate the damage mechanism in the transpassive potential region of AISI ... 相似文献
54.
55.
56.
E. G. Kulapina N. M. Makarova O. I. Kulapina I. A. Utc V. V. Baraguzina 《Petroleum Chemistry》2015,55(10):892-900
Potentiometric sensors with plasticized poly(vinyl chloride) membranes based on β-lactam–tetraalkylammonium ion associates sensitive to penicillin antibiotics are proposed. The physicochemical characteristics (solubility product constants and dissociation constants) of active membrane components and the electrode, transport, and selective properties of the membranes of liquidand solid-contact sensors have been studied. The quantitative characteristics of membrane transport (penetrability, ion flux, and transport rate) have been evaluated. The main charge carriers in the membranes and at the membrane/solution interface have been determined from the membrane transport characteristics. The potentiometric sensors are shown to be applicable to the determination of penicillin antibiotics in biological fluids (blood serum and oral fluid) from patients with urinary tract infection. 相似文献
57.
V. N. Oparin V. I. Vostrikov O. M. Usol’tseva P. A. Tsoi V. N. Semenov 《Journal of Mining Science》2015,51(3):624-633
The authors have developed a procedure and a test bench for studying evolution of various nature physical fields in modeling geomedium fracture by fluids. The test bench performs synchronous recording of macro- and micro-deformation, heat and acoustic emission induced in physical models of geomedium under loading to discontinuity. The experimental procedure has been trialed. The analysis of the synchronized test data allows a conclusion on the existence of time–space relationship between different nature physical fields induced during failure of solids. 相似文献
58.
59.
Quantitative UPLC‐MS/MS analysis of chlorogenic acid derivatives in antioxidant fractionates from dandelion (Taraxacum officinale) root 下载免费PDF全文
Owen Kenny Thomas J. Smyth Chandralal M. Hewage Nigel P. Brunton 《International Journal of Food Science & Technology》2015,50(3):766-773
While qualitative studies have identified chlorogenic acids in antioxidant extracts, particularly ethyl acetate‐derived extracts, of Taraxacum officinale, quantitative analysis of these phenolic compounds remains largely unreported for this species. In this study, bioactivity‐guided fractionation of an antioxidant crude ethyl acetate extract (DPPH = 295.481 ± 0.955 mg TE g?1 extract) from T. officinale root resulted in a number of reverse‐phase fractions that demonstrated high antioxidant activity (DPPH = 1058.733–1312.136 mg TE g?1 extract), stronger than that of the synthetic antioxidant Trolox®. UPLC‐MS/MS screening of these fractions for the presence of selected mono‐ and di‐caffeoylquinic acids revealed large quantities of 1,5‐dicaffeoylquinic acid present in several fractions (853.052–907.324 μg mg?1), respectively. Due to the antioxidant potency and high levels of 1,5‐dicaffeoylquinic acid observed in these fractions, it was concluded that specifically this chlorogenic acid derivative is a major contributor to the antioxidant efficacy of dandelion root. 相似文献
60.
A. A. Babenko V. I. Zhuchkov L. A. Smirnov A. V. Sychev A. A. Akberdin A. S. Kim M. F. Vitushchenko A. A. Dobromilov 《Steel in Translation》2015,45(11):883-886
A technology for slag formation in the ladle–furnace unit is considered; the slag is based on the CaO–SiO2–MgO–Al2O3–B2O3 system. This technology permits both microalloying of the steel with boron (reduced from the oxide phase) and desulfurization of the steel. The resulting boron content in the steel is 0.001–0.008%; the sulfur content in low-alloy steel and pipe steel is low (0.004–0.010%); and the consumption of manganese ferroalloys is reduced to 0.5 kg/t for 08кп steel and 1.4 kg/t for 09Г2C steel. In addition, the proposed technology increases the strength of the rolled steel, without loss in its plasticity; and reduces the environmental impact thanks to the replacement of fluorspar by colemanite. 相似文献