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181.
Xe-Kr laser induced collisional ionization system and experimental preparation of its initial state: Four-photon resonant excitation 下载免费PDF全文
This paper proposes a novel one-colour Xe-Kr laser induced collisional ionization system. Considering the level scheme of the system, it finds that the initial state of the reaction--the four 4f levels with even J of Xe-can be prepared through method of four-photon resonant excitation by dye laser with wavelength of -440 nm. Absorption of an additional photon (the transfer laser) of the same wavelength will complete the laser induced collisional ionization process. The resonance enhanced ionization spectrum of Xe by four laser photons at -440nm is measured through time-of-flight mass spectrometry, this aims at the preparation of the initial state of the system proposed. The Stark broadening of the measured spectrum is observed and consistent with the previous study. Analysis of the measured resonance ionization spectrum implies the feasibility of -440 nm four-photon resonant excitation of the initial 4f state of the Xe Kr system proposed in this paper, which prepares for a further experiment of laser induced collisional ionization. 相似文献
182.
P. CrozetF. Martin A.J. RossC. Linton M.J. DickA.G. Adam 《Journal of Molecular Spectroscopy》2002,213(1):28-34
We have recorded laser excitation spectra of the CaOCH3 free radical in a laser ablation molecular beam apparatus, at a spectral resolution of about 0.010 cm−1 and a rotational temperature estimated at 15 K. The two spin-orbit components of the A2E-X2A1 000 origin band between 625 and 630 nm have been analyzed. Five main subbands were revealed, with ΔK=+1 and K″=0,±1,±2. There was clear evidence of lambda-doubling in the A2E1/2-X2A1 000 (F′1) K′=+1←K″=0 component. A nonlinear least-squares fitting program based on the model developed by Endo et al. [Y. Endo, S. Saito, and E. Hirota, J. Chem. Phys.81, 122-135 (1984)] fit the experimental data (514 A-X lines, N″≤37) with a root mean square deviation of 0.003 cm−1, using known molecular constants of the ground state. The main vibronic (T0=15 925.1232(5) cm−1), spin-orbit (aζed=66.974 48(51) cm−1), Coriolis (Aζt=5.437 30(24)) cm−1, rotational (A=5.439 97(24) cm−1, B=0.117 884(2) cm−1), and fine structure constants (ε1=−8.208(14)×10−3 cm−1, h1=1.50(12)×10−4 cm−1, εaa=3.58(89)×10−3 cm−1, εbc=3.20(76)×10−3 cm−1) for the excited state have been obtained. 相似文献
183.
184.
P. von Brentano C. Fransen A. Gade A. Lisetskiy N. Pietralla 《The European Physical Journal A - Hadrons and Nuclei》2002,15(1-2):99-103
Due to the recent development of radioactive beam production, various direct reaction studies in reversed kinematics have
been made to investigate the behavior of the N = 20 shell closure in the neutron-rich region. Coulomb excitation, proton inelastic scattering, and fragmentation of unstable
nuclei have been studied with γ-ray detection.
Received: 21 March 2002 / Accepted: 16 May 2002 / Published online: 31 October 2002
RID="a"
ID="a"e-mail: motobaya@rikkyo.ne.jp 相似文献
185.
Taris Thierry Begueret Jean-Baptiste Lapuyade Hervé Deval Yann 《Microelectronics Journal》2006,37(11):1251-1260
After a theoretical and analytical study of the body effect in MOS transistors, this paper offers two useful models of this parasitic phenomenon. Thanks to these models, a design methodology, which takes advantage of the bulk terminal, allows to turn this well-known body-effect drawback into an analog advantage, giving thus an efficient alternative to overcome the design constraints of the CMOS VLSI wireless mass market. To illustrate the approach, four RF building blocks are presented. First, a 0.9 V 10 dB gain LNA, covering a frequency range 1.8-2.4 GHz, thanks to a body-effect common mode feedback, is detailed. Secondly, a body-effect linearity controlled pre-power amplifier is presented exhibiting a 5 dB m input compression point (ICP1) variation under 1.8 V power supply for half the current consumption. Lastly, two mixers based on body-effect mixing are presented, which achieve a 10 dB conversion gain under 1.4 V for a −52 dB LO-to-RF isolation. Well suited for low-power/low-voltage applications, these circuits implemented in a 0.18 μm CMOS VLSI technology are dedicated to multi-standard architectures and system-on-chip implementations. 相似文献
186.
Mohammad A. Adeeb Hung Nguyen Syed K. Islam Mo Zhang 《Analog Integrated Circuits and Signal Processing》2006,47(3):355-363
A low-power low-voltage analog signal processing circuit has been designed, fabricated, and tested. The circuit is capable
of processing an analog sensor current and producing an ASK modulated digital signal with modulating signal frequency proportional
to the sensor current level. An on-chip regulator has been included to stabilize the supply voltage received from an external
RF power source. The circuit can operate with a power supply as low as 1 V and consumes only about 20 μW of power, which is
therefore very suitable for implantable biomedical applications. The whole chip was laid out and fabricated in a 0.35 μm bulk
CMOS technology. Experimental results show good agreement with the simulation results. 相似文献
187.
Statistical channel models based on BER performance are presented for a frequency- and time-selective vehicle-to-vehicle wireless communications link in an expressway environment in Atlanta, Georgia, where both vehicles traveled in the same direction. The models are developed from measurements taken using the direct sequence spread spectrum (DSSS) technique at 2.45GHz. A collection of tapped delay line models, referred to as a “partitioned” model in the paper, is developed to attempt to capture the extremes of BER performance of the recorded channel. Overall and partition models are compared to the recorded channel in terms of the BER statistics obtained when the channels are inserted in a dedicated short range radio (DSRC) standard simulation system. The quality of the match between synthesized and recorded channel BER statistics is analyzed with respect to type of modulation (fixed or adaptive), the frame length, and the length of the interval over which the BER was calculated.
Guillermo Acosta was born in Mexico City, Mexico, in 1962. He is a Ph.D. Candidate and a graduate research assistant in the School of Electrical and Computer Engineering at the Georgia Institute of Technology, in Atlanta, Georgia. He obtained his Bachelor of Engineering with Honors and Master of Engineering, both in Electrical Engineering, from Stevens Institute of Technology, Hoboken, New Jersey, in 1985 and 1987, respectively. He also obtained a Master of Business Administration with Honors from the Instituto Tecnologico Autonomo de Mexico (ITAM), Mexico City, Mexico, in 1996. Mr. Acosta has held technical and managerial positions in the recording, radio, and TV industries and in the Communications Ministry of Mexico. He has been an adjunct instructor in Electrical Engineering in the Instituto Tecnologico y Estudios Superiores de Monterrey Campus Estado de Mexico (ITESM-CEM) and the Universidad Iberoamericana. He is member of the IEEE, INCE, Tau Beta Pi, and Eta Kappa Nu.
Mary Ann Ingram received the B.E.E. and Ph.D. degrees from the Georgia Institute of Technology, in Atlanta, Georgia, in 1983 and 1989, respectively. From 1983 to 1986, she was a Research Engineer with the Georgia Tech Research Institute in Atlanta, performing studies on radar electronic countermeasure (ECM) systems. In 1986, she became a graduate research assistant with the School of Electrical and Computer Engineering at the Georgia Institute of Technology, where in 1989, she became a Faculty Member and is currently Professor. Her early research areas were optical communications and radar systems. In 1997, she established the Smart Antenna Research Laboratory (SARL), which emphasizes the application of multiple antennas to wireless communication systems. The SARL performs system analysis and design, channel measurement, and prototyping, relating to a wide range of wireless applications, including wireless local area network (WLAN) and satellite communications, with focus on the lower layers of communication networks. Dr. Ingram is a Senior Member of the IEEE. 相似文献
188.
Ahmed A. Youssef 《Analog Integrated Circuits and Signal Processing》2006,46(3):193-201
This paper presents the design considerations for the noise optimization of fully integrated tuned low-noise amplifiers (LNA)
based on the four noise parameters and two-port noise theory. Specifically, this paper provides the design guidelines for
a 0.18 μm CMOS tuned LNA. These guidelines give a useful indication to the design tradeoffs associated with noise figure,
power dissipation and gate overdrive voltage for the LNA designed using this technology. As a case study, a 10 GHz LNA has
been designed using 0.18 μm CMOS technology for a wireless LAN application. The amplifier has a 2.4 dB noise figure with a
−13 dBm third-order input intercept point, while drawing 5 mW from a 1.8 V power supply. The results show that the proposed
theoretical contours of constant noise figure which relate the gate overdrive voltage and power dissipation can accurately
predict the noise performance of a 0.18 μm CMOS LNA design
Ahmed A. Youssef received the B.Sc. (Hon.) and M.Sc. degrees both in electrical engineering from Ain Shams University, Cairo, Egypt, in 1998
and 2002, respectively. Since 2003, he has been with the University of Calgary, AB, Canada, where he is currently working
toward the Ph.D. degree in RF integrated circuits and systems.
Mr. Youssef has joined the Wireless Research Center at TRLab, Alberta, Canada as a research associate in 2004. His research
interests include the analog high speed integrated circuit for the wireless LAN applications.
Mr. Youssef is the recipient of the Mobinil Telecommunication Inc. Pre-master Fellowship in 1999. He also received the Young
Scientist award at the Maastricht General Assembly of the International Union of Radio Science in 2002 and an Honorable Mention
at 2003 in the Symposium of the Microelectronics Research & Development in Canada, Montreal. Mr. Youssef received the Gordon
Lewis Hedberg Doctoral Scholarship in 2005. 相似文献
189.
190.
采用射频磁控溅射技术利用循环间歇溅射工艺,在Pt/Ti/SiO2/Si基片上制备出了镧钛酸铅(PLT)薄膜。通过原子力显微镜、X-射线衍射仪分析了循环间歇溅射工艺对薄膜形貌、结构和铁电性能的影响。实验结果表明,相比于连续溅射工艺,循环间歇溅射工艺的基片温度较低,且制得的PLT薄膜晶粒细小、均匀,结构致密。薄膜具有纯钙钛矿型结构,循环次数从1次增加到3次,其(100)和(200)峰衍射强度逐渐增强,结晶性提高,铁电性能逐渐增强,其饱和极化强度由28μC/cm2增大到53μC/cm2,剩余极化强度由5μC/cm2增大到12μC/cm2。循环4次溅射后,薄膜的结晶性和铁电性开始下降。 相似文献