全文获取类型
收费全文 | 2409篇 |
免费 | 512篇 |
国内免费 | 328篇 |
专业分类
化学 | 1201篇 |
晶体学 | 44篇 |
力学 | 443篇 |
综合类 | 38篇 |
数学 | 171篇 |
物理学 | 1352篇 |
出版年
2024年 | 11篇 |
2023年 | 36篇 |
2022年 | 117篇 |
2021年 | 116篇 |
2020年 | 157篇 |
2019年 | 100篇 |
2018年 | 93篇 |
2017年 | 123篇 |
2016年 | 162篇 |
2015年 | 129篇 |
2014年 | 160篇 |
2013年 | 211篇 |
2012年 | 148篇 |
2011年 | 178篇 |
2010年 | 129篇 |
2009年 | 131篇 |
2008年 | 109篇 |
2007年 | 127篇 |
2006年 | 131篇 |
2005年 | 102篇 |
2004年 | 87篇 |
2003年 | 104篇 |
2002年 | 88篇 |
2001年 | 60篇 |
2000年 | 64篇 |
1999年 | 58篇 |
1998年 | 47篇 |
1997年 | 41篇 |
1996年 | 41篇 |
1995年 | 30篇 |
1994年 | 20篇 |
1993年 | 28篇 |
1992年 | 21篇 |
1991年 | 13篇 |
1990年 | 10篇 |
1989年 | 8篇 |
1988年 | 12篇 |
1987年 | 3篇 |
1986年 | 4篇 |
1985年 | 12篇 |
1984年 | 5篇 |
1982年 | 4篇 |
1981年 | 2篇 |
1980年 | 3篇 |
1979年 | 5篇 |
1978年 | 1篇 |
1975年 | 1篇 |
1971年 | 1篇 |
1957年 | 4篇 |
1936年 | 1篇 |
排序方式: 共有3249条查询结果,搜索用时 375 毫秒
161.
162.
White organic light-emitting device was achieved through an incorporation of yellow YAG nanophosphors into blue polyfluorene emitting layer: electrode/YAG@polyfluorene/hole-transport/injection layers/ITO glass. The brightness of the proposed device (230 cd/m2 at 30 V) was enhanced by a factor of about two in comparison with that of phosphor-free reference device. It is attributed to the increased local electric field caused by bumps of nanophophors on the emitting layer. With increase of voltage, the blue-green emission decreased whereas the yellow emission increased. It is due to the effective energy transfer from the blue-green to the yellow bands. 相似文献
163.
Zahra Moulana Mousa Ghaemi Soudabeh Qasemi Khadijeh Ghassemi Mohammad R. Hasanjani Roushan 《高分子科学杂志,A辑:纯化学与应用化学》2017,54(1):30-39
There are many different strategies to decrease the incidence of infection of medical device and food related containers. One way to prevent infection is by modifying the polymers used in making the devices and containers. Incorporation of antimicrobial agents in the bulk material or in formulations of medical devices production has been considered a viable alternative for systemic application of antibiotics. In this article, preparation of a series of triazole containing polymers, poly(triazole-amide-imide)s (PTAI)s and poly(triazole-amide) (PTA)s, and their monomers are reported. These polymers were readily soluble in a variety of organic solvents, showed significant thermal properties and also viscosities in the range of 0.55–0.66 dL/g. They have been tested against a range of Gram-positive and Gram-negative pathogens. The results indicated that these novel polymers containing triazole moiety in their repeating units can effectively control Gram-positive and negative pathogens and their physic-chemical properties besides their antibacterial characteristics make them unique candidate for using in the manufacturing of the medical devices. 相似文献
164.
Timothy H. Click Aibing Liu George A. Kaminski 《Journal of computational chemistry》2011,32(3):513-524
We have simulated pure liquid butane, methanol, and hydrated alanine polypeptide with the Monte Carlo technique using three kinds of random number generators (RNG's)—the standard Linear Congruential Generator (LCG), a modification of the LCG with additional randomization used in the BOSS software, and the “Mersenne Twister” generator by Matsumoto and Nishimura. While using the latter two RNG's leads to reasonably similar physical features, the LCG produces significant different results. For the pure fluids, a noticeable expansion occurs. Using the original LCG on butane yields, a molecular volume of 171.4 Å3 per molecule compared to about 163.6–163.9 Å3 for the other two generators, a deviation of about 5%. For methanol, the LCG produces an average volume of 86.3 Å3 per molecule, which is about 24% higher than the 68.8–70.2 Å3 obtained with the RNG's in BOSS and the generator by Matsumoto and Nishimura. In case of the hydrated tridecaalanine peptide, the volume and energy tend to be noticeably greater with the LCG than with the BOSS (modified LCG) RNG's. For the simulated hydrated extended conformation of tridecaalanine, the difference in volume reached about 87%. The uniformity and periodicity of the generators do not seem to play the crucial role in these phenomena. We conclude that, it is important to test a RNG's by modeling a system such as the pure liquid methanol with a well‐established force field before routinely employing it in Monte Carlo simulations. © 2010 Wiley Periodicals, Inc. J Comput Chem, 2011 相似文献
165.
Energy spectrum of multi-radiation of X-rays in a low energy Mather-type plasma focus device
下载免费PDF全文
![点击此处可从《中国物理 B》网站下载免费的PDF全文](/ch/ext_images/free.gif)
The multi-radiation of X-rays was investigated with special attention to their energy spectrum in a Mather-type plasma focus device (operated with argon gas). The analysis is based on the effect of anomalous resistances. To study the energy spectrum, a four-channel diode X-ray spectrometer was used along with a special set of filters. The filters were suitable for detection of medium range X-rays as well as hard X-rays with energy exceeding 30 keV. The results indicate that the anomalous resistivity effect during the post pinch phase may cause multi-radiation of X-rays with a total duration of 300 ± 50 ns. The significant contribution of Cu-Kα was due to the medium range X-rays, nonetheless, hard X-rays with energies greater than 15 keV also participate in the process. The total emitted X-ray energy in the forms of Cu-K and Cu-K/3 was around 0.14 ± 0.02 (J/Sr) and 0.04 ±0.01 (J/Sr), respectively. The total energy of the emitted hard X-ray (〉 15 keV) was around 0.12± 0.02 (J/Sr). 相似文献
166.
Naoyoshi Komatsu Keiko Masumoto Hidemitsu Aoki Chiharu Kimura Takashi Sugino 《Applied Surface Science》2010,256(6):1803-8310
Synthesis of Si-added aluminum oxide (AlSiO) films is attempted as an insulating film with both a wide bandgap and a high dielectric constant. Electrical characteristics of AlSiO films are investigated. Leakage current of the AlO film is suppressed by Si addition and is minimized with Si composition ratio of 12%. Capacitance versus voltage (C-V) measurements are carried out for Au/AlSiO/Si MIS structure. Both flat band shift and hysteresis of the C-V characteristics are suppressed by Si addition. A low leakage current is demonstrated for Au/AlSiO/n-SiC MIS structure. 相似文献
167.
Zhihui Yi Luca Giacomo Bettini Gaia Tomasello Prajwal Kumar Paolo Piseri Irina Valitova Paolo Milani Francesca Soavi Fabio Cicoira 《Journal of Polymer Science.Polymer Physics》2017,55(1):96-103
Planar organic electrochemical transistors (OECTs) using PEDOT:PSS as the channel material and nanostructured carbon (nsC) as the gate electrode material and poly(sodium 4‐styrenesulfonate (PSSNa) gel as the electrolyte were fabricated on flexible polyethylene terephthalate (Mylar®) substrates. The nsC was deposited at room‐temperature by supersonic cluster beam deposition (SCBD). Interestingly, the OECT acts as a hybrid supercapacitor (to give a device that we indicate as transcap). The energy storage ability of transcaps has been studied with two cell configurations: one featuring PEDOT:PSS as the positive electrode and nsC as the negative electrode and another configuration with reversed electrode polarity. Potentiostatic charge/discharge studies show that both supercapacitors show good performance in terms of voltage retention, in particular, when PEDOT:PSS is used as the positive electrode. Galvanostatic charge–discharge characteristics show typical symmetric triangular shape, indicating a nearly ideal capacitive behavior with a high columbic efficiency (close to 100%). © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017 , 55, 96–103 相似文献
168.
We propose a two-color scheme of atom waveguides and one-dimensional (1D) optical lattices using evanescent wave fields of different transverse modes around an optical micro/nano-fiber. The atom guide potential can be produced when the optical fiber carries a red-detuned light with TE01 mode and a blue-detuned light with HEll mode, and the 1D optical lattice potential can be produced when the red-detuned light is transformed to the superposition of the TE01 mode and HE11 mode. The two trapping potentials can be transformed to each other for accurately controlling mode transformation for the red-detuned light. This might provide a new approach to realize flexible transition between the guiding and trapping states of atoms. 相似文献
169.
The production and transportation of fluorescent light produced in wavelength-shifting fibers (WSFs) coupled to YAP scintillation crystal is simulated using the GEANT4 codes.An advantage of the wavelength-shifting fiber readout technique over a direct readout with a position-sensitive photo-sensor is the reduced requirement for position sensitive photomultiplier tube photocathode area.With this gamma-ray detector,the gamma camera is small and flexible and has larger effective field of view and low cost.Simulation results show that a) a mean 12 of photons per 59.5 keV gamma ray interaction is produced in the WSF located nearest to the incident gamma ray,and a spatial resolution of 3.6 mm FWHM is obtained,b)a mean 27 of photons per 140 keV gamma ray interaction is produced and a spatial resolution of 3.1 mm FWHM is obtained.Results demonstrate the feasibility of this concept of a compact gamma-ray detector based on wavelength-shifting fibers readout.However,since the very low photoelectron levels,it is very important to use a photon counting device with good single photo-electron response to readout the WSFs. 相似文献
170.