全文获取类型
收费全文 | 280855篇 |
免费 | 3478篇 |
国内免费 | 1306篇 |
专业分类
电工技术 | 4821篇 |
综合类 | 523篇 |
化学工业 | 41026篇 |
金属工艺 | 11149篇 |
机械仪表 | 8469篇 |
建筑科学 | 6512篇 |
矿业工程 | 1585篇 |
能源动力 | 7090篇 |
轻工业 | 22936篇 |
水利工程 | 3068篇 |
石油天然气 | 5789篇 |
武器工业 | 43篇 |
无线电 | 33738篇 |
一般工业技术 | 56854篇 |
冶金工业 | 50933篇 |
原子能技术 | 7522篇 |
自动化技术 | 23581篇 |
出版年
2021年 | 2296篇 |
2019年 | 2163篇 |
2018年 | 3680篇 |
2017年 | 3772篇 |
2016年 | 4030篇 |
2015年 | 2578篇 |
2014年 | 4526篇 |
2013年 | 12216篇 |
2012年 | 7296篇 |
2011年 | 9945篇 |
2010年 | 7717篇 |
2009年 | 8931篇 |
2008年 | 9262篇 |
2007年 | 9288篇 |
2006年 | 7892篇 |
2005年 | 7337篇 |
2004年 | 7263篇 |
2003年 | 7049篇 |
2002年 | 6769篇 |
2001年 | 6865篇 |
2000年 | 6499篇 |
1999年 | 6792篇 |
1998年 | 16325篇 |
1997年 | 11598篇 |
1996年 | 8942篇 |
1995年 | 6864篇 |
1994年 | 6028篇 |
1993年 | 6065篇 |
1992年 | 4406篇 |
1991年 | 4184篇 |
1990年 | 4083篇 |
1989年 | 4065篇 |
1988年 | 3753篇 |
1987年 | 3392篇 |
1986年 | 3395篇 |
1985年 | 3742篇 |
1984年 | 3460篇 |
1983年 | 3218篇 |
1982年 | 3026篇 |
1981年 | 3040篇 |
1980年 | 3030篇 |
1979年 | 2829篇 |
1978年 | 2872篇 |
1977年 | 3141篇 |
1976年 | 4096篇 |
1975年 | 2416篇 |
1974年 | 2379篇 |
1973年 | 2396篇 |
1972年 | 2018篇 |
1971年 | 1781篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
Kooij Julian F. P. Flohr Fabian Pool Ewoud A. I. Gavrila Dariu M. 《International Journal of Computer Vision》2019,127(3):239-262
International Journal of Computer Vision - Anticipating future situations from streaming sensor data is a key perception challenge for mobile robotics and automated vehicles. We address the problem... 相似文献
42.
Kazantsev Yu. N. Kraftmakher G. A. Mal’tsev V. P. 《Journal of Communications Technology and Electronics》2019,64(6):550-554
Journal of Communications Technology and Electronics - Approximate formulas for calculating the coefficient of reflection from an artificial magnetic conductor (AMC) based on a capacitive lattice... 相似文献
43.
Wei LingNan Wang ZhenHua Zhang ZhiDong Liu Chieh-Wen Gao Xuan P. A. 《Nano Research》2020,13(5):1332-1338
Nano Research - We report the composition and back-gate voltage tuned transport properties of ternary compound Bi2(Te1−xSex)3 nanowires synthesized by chemical vapor deposition (CVD). It is... 相似文献
44.
Dr. Lina Liang Tong-You Wade Wei Pei-Yu Wu Wouter Herrebout Ming-Daw Tsai Prof. Stéphane P. Vincent 《Chembiochem : a European journal of chemical biology》2020,21(20):2982-2990
d -Glycero-d -manno-heptose-1β,7-bisphosphate (HBP) and d -glycero-d -manno-heptose-1β-phosphate (H1P) are bacterial metabolites that were recently shown to stimulate inflammatory responses in host cells through the activation of the TIFA-dependent NF-κB pathway. To better understand structure-based activity in relation to this process, a family of nonhydrolyzable phosphonate analogues of HBP and H1P was synthesized. The inflammation modulation by which these molecules induce the TIFA-NF-κB signal axis was evaluated in vivo at a low-nanomolar concentration (6 nM) and compared to that of the natural metabolites. Our data showed that three phosphonate analogues had similar stimulatory activity to HBP, whereas two phosphonates antagonized HBP-induced TIFA-NF-κB signaling. These results open new horizons for the design of pro-inflammatory and innate immune modulators that could be used as vaccine adjuvant. 相似文献
45.
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
46.
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
47.
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
48.
49.
50.
Lecture capture with real‐time rearrangement of visual elements: impact on student performance 下载免费PDF全文
The primary goal of this study is to create and test a lecture‐capture system that can rearrange visual elements while recording is still taking place, in such a way that student performance can be positively influenced. The system we have devised is capable of integrating and rearranging multimedia sources, including learning content, the instructor and students' images, into lecture videos that are embedded in a website for students to review after school. The present study employed a two‐group experimental design, with 153 participants (145 females and 8 males) making up an experimental group in which lecture courses were recorded using the new lecture‐capture system, and 149 participants (140 females and 9 males) forming a control group whose lectures were recorded by traditional means. All participants were in the freshman college and studying Introduction to Computer and Information Science in one of six classes, and were randomly assigned to one of the two groups. The participants' midterm examination and final examination scores were collected as indicators of their academic performance, with their mathematics entrance scores used as a pre‐test. The findings obtained from analysis of covariance (ANCOVA) suggest that appropriate rearrangement of visual elements in lecture videos can significantly impact students' learning performance. 相似文献