全文获取类型
收费全文 | 455816篇 |
免费 | 5880篇 |
国内免费 | 1619篇 |
专业分类
电工技术 | 8561篇 |
综合类 | 507篇 |
化学工业 | 69907篇 |
金属工艺 | 19230篇 |
机械仪表 | 13663篇 |
建筑科学 | 11136篇 |
矿业工程 | 1832篇 |
能源动力 | 10821篇 |
轻工业 | 44910篇 |
水利工程 | 4080篇 |
石油天然气 | 6288篇 |
武器工业 | 35篇 |
无线电 | 52432篇 |
一般工业技术 | 84393篇 |
冶金工业 | 90898篇 |
原子能技术 | 9132篇 |
自动化技术 | 35490篇 |
出版年
2021年 | 3469篇 |
2019年 | 3296篇 |
2018年 | 5560篇 |
2017年 | 5385篇 |
2016年 | 5895篇 |
2015年 | 3941篇 |
2014年 | 6697篇 |
2013年 | 19961篇 |
2012年 | 10931篇 |
2011年 | 15159篇 |
2010年 | 12140篇 |
2009年 | 13458篇 |
2008年 | 14274篇 |
2007年 | 14470篇 |
2006年 | 13070篇 |
2005年 | 11760篇 |
2004年 | 11315篇 |
2003年 | 11121篇 |
2002年 | 11195篇 |
2001年 | 11102篇 |
2000年 | 10459篇 |
1999年 | 11007篇 |
1998年 | 27495篇 |
1997年 | 19273篇 |
1996年 | 14941篇 |
1995年 | 11319篇 |
1994年 | 10037篇 |
1993年 | 9755篇 |
1992年 | 7235篇 |
1991年 | 6941篇 |
1990年 | 6770篇 |
1989年 | 6553篇 |
1988年 | 6359篇 |
1987年 | 5477篇 |
1986年 | 5442篇 |
1985年 | 6397篇 |
1984年 | 5890篇 |
1983年 | 5310篇 |
1982年 | 4976篇 |
1981年 | 5065篇 |
1980年 | 4848篇 |
1979年 | 4609篇 |
1978年 | 4641篇 |
1977年 | 5444篇 |
1976年 | 7583篇 |
1975年 | 4027篇 |
1974年 | 3795篇 |
1973年 | 3914篇 |
1972年 | 3255篇 |
1971年 | 2993篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
141.
142.
Marcus Heinze Sandra Starke Marcel Händler Hartmut Komber Marco Drache Norbert Moszner Brigitte Voit Doris Pospiech 《应用聚合物科学杂志》2019,136(48):48256
We demonstrate in this study that the combination of modern inline monitoring methods [here: inline nuclear magnetic resonance (NMR)] with simulations gains more exact and profound kinetic results than previously used methods like linearization without that combination. The 1H-NMR spectroscopic data (more than 100 data points) are used to construct the copolymerization diagram. The reactivity ratios are obtained applying the van Herks nonlinear least square method. The examination of the radical copolymerization of 2-hydroxyethyl methacrylate (HEMA) with (2-{[2-(ethoxycarbonyl)prop-2-en-1-yl]oxy}ethyl) phosphonic acid (ECPPA) as important adhesive monomer used in dentistry yields reactivity ratios of rHEMA = 1.83; rECPPA = 0.42. The copolymerization diagram reflects nonideal, non-azeotropic copolymerization. The sequence distribution of the obtained by Monte Carlo simulation indicates the generation of statistical copolymers. As an important finding, it is demonstrated that the repeating units responsible for etching and adhesion are arranged over the whole polymer chain, which is necessary to achieve proper functionality. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48256. 相似文献
143.
144.
Journal of Computer and Systems Sciences International - A problem of the synthesis of programmed motions of mechanical systems based on the use of time polynomials is considered. The programmed... 相似文献
145.
146.
147.
148.
Joo H. Kang Eujin Um Alexander Diaz Harry Driscoll Melissa J. Rodas Karel Domansky Alexander L. Watters Michael Super Howard A. Stone Donald E. Ingber 《Small (Weinheim an der Bergstrasse, Germany)》2015,11(42):5657-5666
Magnetic nanoparticles have been employed to capture pathogens for many biological applications; however, optimal particle sizes have been determined empirically in specific capturing protocols. Here, a theoretical model that simulates capture of bacteria is described and used to calculate bacterial collision frequencies and magnetophoretic properties for a range of particle sizes. The model predicts that particles with a diameter of 460 nm should produce optimal separation of bacteria in buffer flowing at 1 L h−1. Validating the predictive power of the model, Staphylococcus aureus is separated from buffer and blood flowing through magnetic capture devices using six different sizes of magnetic particles. Experimental magnetic separation in buffer conditions confirms that particles with a diameter closest to the predicted optimal particle size provide the most effective capture. Modeling the capturing process in plasma and blood by introducing empirical constants (ce), which integrate the interfering effects of biological components on the binding kinetics of magnetic beads to bacteria, smaller beads with 50 nm diameters are predicted that exhibit maximum magnetic separation of bacteria from blood and experimentally validated this trend. The predictive power of the model suggests its utility for the future design of magnetic separation for diagnostic and therapeutic applications. 相似文献
149.
150.
The design of a microstrip‐fed annular‐ring slot antenna (ARSA) with circular polarization (CP) radiation is initially studied. To obtain CP radiation with broad 3‐dB axial ratio (AR) bandwidth that can cover the WiMAX 2.3 GHz (2305–2320 MHz, 2345–2360 MHz) and WLAN 2.4 GHz (2400–2480 MHz) bands, a novel technique of extending an inverted L‐shaped slot from the bottom section of the annular‐ring is proposed. To suppress the harmonic modes induced by the CP ARSA, the technique of integrating a defected ground structure into the annular‐ring slot is further introduced. From the measured results, 10‐dB impedance bandwidth and 3‐dB AR bandwidth of 44.86 and 9.68% were achieved by the proposed harmonic suppressed CP ARSA. Furthermore, average gain and radiation efficiency of ~4.7 dBic and 71%, respectively, were also exhibited across the bands of interest. © 2014 Wiley Periodicals, Inc. Int J RF and Microwave CAE 25:337–345, 2015. 相似文献