全文获取类型
收费全文 | 211篇 |
免费 | 9篇 |
国内免费 | 3篇 |
专业分类
化学 | 69篇 |
力学 | 10篇 |
数学 | 6篇 |
物理学 | 138篇 |
出版年
2024年 | 3篇 |
2023年 | 1篇 |
2022年 | 1篇 |
2021年 | 1篇 |
2020年 | 3篇 |
2019年 | 5篇 |
2018年 | 2篇 |
2017年 | 9篇 |
2016年 | 6篇 |
2015年 | 4篇 |
2014年 | 8篇 |
2013年 | 12篇 |
2012年 | 5篇 |
2011年 | 12篇 |
2010年 | 4篇 |
2009年 | 16篇 |
2008年 | 18篇 |
2007年 | 13篇 |
2006年 | 12篇 |
2005年 | 5篇 |
2004年 | 5篇 |
2003年 | 11篇 |
2002年 | 5篇 |
2001年 | 2篇 |
2000年 | 4篇 |
1998年 | 7篇 |
1997年 | 1篇 |
1996年 | 4篇 |
1995年 | 8篇 |
1994年 | 2篇 |
1993年 | 3篇 |
1992年 | 7篇 |
1991年 | 2篇 |
1990年 | 3篇 |
1989年 | 3篇 |
1988年 | 5篇 |
1985年 | 2篇 |
1984年 | 3篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1981年 | 2篇 |
1979年 | 1篇 |
1977年 | 1篇 |
排序方式: 共有223条查询结果,搜索用时 31 毫秒
131.
A laser Doppler velocimeter (LDV) for two-dimensional velocity measurement using a simple optical configuration without any optical modulator is proposed. The structure using polarized beams and the 90° phase shift of the reference beam is used to discriminate the direction of velocity. The analytical relation among beat frequencies and velocity components is derived and the characteristics of the proposed LDV are simulated. The simulation results indicate that the direction of velocity can be discriminated by the proposed LDV as well as the magnitudes of the components of the velocity. 相似文献
132.
A dielectric barrier discharge (DBD) was used as a new atmospheric optical emission detector for the determination of trace nitrogen in pure argon gas in this work. The whole system was composed of an ac ozone generation device for power supply, a six-way valve, a laboratory-built DBD device and a USB2000 charge coupled device (CCD). Trace nitrogen in argon was detected at nitrogen molecular emission line of 337 nm. This method features with several advantages: atmospheric working condition, low power consumption (≤ 12 W), simple and cheap instrumentation, fast response and high sensitivity and accuracy. Under the optimized conditions, the limits of detection can be down to 34 ppb. 相似文献
133.
M. P. Seah 《Surface and interface analysis : SIA》2007,39(4):367-369
This International Standard adds 5 abbreviations and 71 terms, many for glow discharge spectrometry, to the 340 defined terms for surface chemical analysis in ISO 18115:2001. The terms cover words or phrases used in describing the samples, instruments and theoretical concepts involved in surface chemical analysis. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
134.
Charles D. Immanuel Timothy J. Crowley Edward S. Meadows Cajetan F. Cordeiro Francis J. Doyle 《Journal of polymer science. Part A, Polymer chemistry》2003,41(14):2232-2249
This article presents a study on the engineering of multimodal distributions in semibatch emulsion polymerizations with nonionic surfactants. Various methods of producing multimodal distributions are demonstrated, and the sensitivity of the process to the properties of the reagents are analyzed. A test‐bed emulsion polymerization system, equipped with instrumentation to measure particle size distribution (capillary hydrodynamic fractionator) and monomer conversion (densitometer and flow meters), is used for this purpose. The process is monitored and controlled with an industrial distributed control system, which enables the automated operation of the process through sequential or logic controllers operating over lower level proportional integral derivative controllers. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2232–2249, 2003 相似文献
135.
Y. Tai J. Murakami K. Saito M. Ikeyama K. Tajiri M. Watanabe S. Tanemura T. Mizota 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,24(1-3):261-263
Plasma desorption mass spectrometry has been applied to
characterization of dodecanthiol-passivated gold nanoparticles.
An overview of the experimental set-up and mass analyses for the
nanoparticles prepared in different conditions are shown. Mass
distributions were found to shift to higher mass regions with
increasing reaction temperature and reaction period. The results
are consistent with those of transmission electron microscopy
observations, UV-visible absorption spectra and also with a
reported laser desorption mass spectrometry. 相似文献
136.
J. M. Lopez-Higuera 《Fiber and Integrated Optics》2004,23(2):207-229
The recent research and development results of the Photonic Engineering Group in the photonic sensing field are reported. This article includes a sample of contributions in several of the ongoing R&D lines: fiber sensing using Bragg grating technology; gas sensing, high temperature monitoring; optoelectronic instrumentation for laser welding monitoring; fiber active devices; and, finally, on sensing technology using plastic optical fiber. 相似文献
137.
Nark‐Eon Sung Ik‐Jae Lee Kug‐Seong Lee Seong‐Hun Jeong Seen‐Woong Kang Yong‐Bi Shin 《Journal of synchrotron radiation》2015,22(5):1306-1311
A microprobe system has been installed on the nanoprobe/XAFS beamline (BL8C) at PLS‐II, South Korea. Owing to the reproducible switch of the gap of the in‐vacuum undulator (IVU), the intense and brilliant hard X‐ray beam of an IVU can be used in X‐ray fluorescence (XRF) and X‐ray absorption fine‐structure (XAFS) experiments. For high‐spatial‐resolution microprobe experiments a Kirkpatrick–Baez mirror system has been used to focus the millimeter‐sized X‐ray beam to a micrometer‐sized beam. The performance of this system was examined by a combination of micro‐XRF imaging and micro‐XAFS of a beetle wing. These results indicate that the microprobe system of the BL8C can be used to obtain the distributions of trace elements and chemical and structural information of complex materials. 相似文献
138.
139.
A heated horizontal heat transfer tube was installed 14.8 cm above the distributor plate in a square fluid bed measuring 30.5 × 30.5 cm. Four different Geldart B sized particle beds were used (sand of two different distributions, an abrasive and glass beads) and the bed was fluidized with cold air. The tube was instrumented with surface thermocouples around half of the tube circumference and with differential pressure ports that can be used to infer bubble presence. Numerical execution of the transient conduction equation for the tube allowed the local time-varying heat transfer coefficient to be extracted. Data confirm the presence of the stagnant zone on top of the tube associated with low superficial velocities. Auto-correlation of thermocouple data revealed bubble frequencies and the cross-correlation of thermal and pressure events confirmed the relationship between the bubbles and the heat transfer events. In keeping with the notion of a “Packet renewal” heat transfer model, the average heat transfer coefficient was found to vary in sympathy with the root-mean square amplitude of the transient heat transfer coefficient. 相似文献
140.
纳米孔道分析技术是一种基于电化学空间限域效应的单分子检测技术。测量纳米孔道产生的单分子皮安级微弱电流信号对电化学测量仪器的电流分辨、时间分辨和抗噪音能力提出了挑战。Cube纳米孔道电化学测量仪器通过设计频率补偿电路、前置电流放大器测量系统和基于现场可编程逻辑门阵列(FPGA)的高速数字处理电路,实现了便携式超灵敏电化学测量仪器对微弱电流信号的高时间分辨、高电流分辨,以及低噪音的放大、采集和快速处理。稳定性是仪器能够应用于实际单分子测量分析的重要衡量指标之一。该文通过高阻值电阻对该仪器进行稳定性测试,在截止滤波频率为5、10、100 kHz条件下,Cube纳米孔道仪器获取的电流基线的噪音均方根(RMS)值分别比商品化仪器减小了80.0%、87.5%、48.2%,证明Cube纳米孔道仪器抑制噪音能力更强,电流分辨能力更好,仪器测量稳定性更佳。进一步通过统计比较施加电压值的实际值和标准偏差,结果显示该仪器施加电压误差小,其仪器施加电压标准偏差仅为施加电压变化量(10 mV)的0.14%。同时,通过Aerolysin纳米孔道检测Poly(dA)4的实验,对比Cube仪器和商品化仪器在不同施加电压下获取的单分子信号残余电流程度,得到两者误差均小于0.01,结果具有可重复性。因此,Cube纳米孔道仪器具有稳定性好、灵敏度高、便携性强的特点,可应用于纳米孔道单分子分析。 相似文献