全文获取类型
收费全文 | 720篇 |
免费 | 128篇 |
国内免费 | 60篇 |
专业分类
化学 | 236篇 |
晶体学 | 1篇 |
力学 | 19篇 |
综合类 | 1篇 |
数学 | 33篇 |
物理学 | 618篇 |
出版年
2023年 | 9篇 |
2022年 | 8篇 |
2021年 | 13篇 |
2020年 | 5篇 |
2019年 | 9篇 |
2018年 | 9篇 |
2017年 | 14篇 |
2016年 | 17篇 |
2015年 | 14篇 |
2014年 | 54篇 |
2013年 | 33篇 |
2012年 | 48篇 |
2011年 | 58篇 |
2010年 | 37篇 |
2009年 | 64篇 |
2008年 | 55篇 |
2007年 | 65篇 |
2006年 | 78篇 |
2005年 | 63篇 |
2004年 | 40篇 |
2003年 | 30篇 |
2002年 | 23篇 |
2001年 | 30篇 |
2000年 | 23篇 |
1999年 | 15篇 |
1998年 | 12篇 |
1997年 | 9篇 |
1996年 | 10篇 |
1995年 | 8篇 |
1994年 | 7篇 |
1993年 | 5篇 |
1992年 | 4篇 |
1991年 | 10篇 |
1990年 | 4篇 |
1989年 | 4篇 |
1988年 | 1篇 |
1987年 | 2篇 |
1986年 | 1篇 |
1985年 | 2篇 |
1984年 | 3篇 |
1983年 | 1篇 |
1982年 | 3篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1977年 | 1篇 |
1976年 | 2篇 |
1975年 | 1篇 |
1971年 | 1篇 |
排序方式: 共有908条查询结果,搜索用时 568 毫秒
1.
Piezoelectric cat-eye modulating retro-reflector (MRR) is the core component of an acousto-optic retro-identification system. The influence of the optical parameters (link distance l, lens focal length f and the detector diameter r) to the cat-eye effect was analyzed theoretically and experimentally. A piezoelectric cat-eye retro-identification (PCERI) system was built, and an information transmission ratio of 2 kHz was achieved which can satisfy an access control system. 相似文献
2.
Teslime Erşan Didem Giray Dilgin Elif Kumrulu Umur Kumrulu Yusuf Dilgin 《Electroanalysis》2023,35(4):e202200295
This work describes the sensitive voltammetric determination of favipiravir (FAV) based on its reduction for the first time with a low-cost and disposable pencil graphite electrode (PGE). In addition, the determination of FAV was also performed based on its oxidation. Differential pulse (DP) voltammograms recorded in 0.5 M H2SO4 for the reduction of FAV show that peak currents increase linearly in the range of 1.0 to 600.0 μM with a limit of detection of 0.35 μM. The acceptable recovery values (98.9–106.0 %) obtained from a pharmaceutical tablet, real human urine, and artificial blood serum samples spiked with FAV confirm the high accuracy of the proposed method. 相似文献
3.
Dr. Aline Varella Rodrigues Bruno Seiki Domingos Onishi Prof. Dr. Sidney José Lima Ribeiro 《Chemphyschem》2023,24(21):e202300134
This research endeavors to overcome the significant challenge of developing materials that simultaneously possess photostability and photosensitivity to UV-visible irradiation. Sulfurized nanorod (NR)-like ZnO/Zn(OH)2 and hierarchical flower-like γ-Zn(OH)2/ϵ-Zn(OH)2 were identified from XRD diffraction patterns and Raman vibrational modes. The sulfurized material, observed by FEG-SEM and TEM, showed diameters ranging from 10 and 40 nm and lengths exceeding 200 nm. The S2− ions intercalated Zn2+, modulating NRs to dumbbell-like microrods. SAED and HRTEM illustrated the atomic structure in (101) crystal plane. Its direct band gap of 3.0 eV was attributed to the oxygen vacancies, which also contribute to the deep-level emissions at 422 and 485 nm. BET indicated specific surface area of 4.4 m2 g−1 and pore size as mesoporosity, which are higher compared to the non-sulfurized analogue. These findings were consistent with the observed photocurrent, photostability and photoluminescence (PL), further supporting the suitability of sulfurized NR-like ZnO/Zn(OH)2 as a promising candidate for Luminescent solar concentrators (LSC)-photovoltaic (PV) system. 相似文献
4.
Liver regeneration has been studied for decades; however, its regulation remains unclear. In this study, we report a dynamic tracing of protein synthesis in rat regenerating liver with a new proteomic technique, 35S in vivo labeling analysis for dynamic proteomics (SiLAD). Conventional proteomic techniques typically measure protein alteration in accumulated amounts. The SiLAD technique specifically detects protein synthesis velocity instead of accumulated amounts of protein through 35S pulse labeling of newly synthesized proteins, providing a direct way for analyzing protein synthesis variations. Consequently, protein synthesis within short as 30 min was visualized and protein regulations in the first 8 h of regenerating liver were dynamically traced. Further, the 3.5–5 h post partial hepatectomy (PHx) was shown to be an important regulatory turning point by acute regulation of many proteins in the initiation of liver regeneration. 相似文献
5.
The use of liquid fuels such as kerosene is of interest for the Pulse Detonation Engine (PDE). In this context, a representative
gaseous mixture of the lighter products resulting from the decomposition of a kerosene of type JP-10 was studied. The detonability
limits of simple components (hydrogen, ethylene, propylene) and mixtures of these components were tested in a 50 mm diameter
and 2.5 m long detonation tube. This dimension is compatible with the applications of the aircraft industry and more particularly
the PDE. The influences of the nitrogen dilution, geometry of the DDT device (Schelkin spiral), ignition energy and initial
pressure were investigated.
This paper was based on work that was presented at the 19th International Colloquium on the Dynamics of Explosions and Reactive
Systems, Hakone, Japan, July 27 - August 1, 2003.
Communicated by J.E. Shepherd 相似文献
6.
7.
Pulse diagnosis is an important part of Chinese medicine and has played an important role in the development of Chinese medical science. However, the pulse is traditionally determined by cutting it off, which leads to a lack of objective standard pulse identification methods and affects their accuracy and feasibility. This research has studied and discussed the processing and identification of four kinds of pulse: normal pulse, wiry pulse, smooth pulse, and thready pulse. Four frequency-domain characteristics of the pulse wave and six kinds of wavelet scale energy characteristic information were extracted, and a three-layer BP (backprocessing) neural network was established. The LM (Levenberg–Marquard) algorithm and a genetic algorithm were used to improve the BP neural network, to train on and predict experimental samples, and to obtain classification accuracies of 90% and 95% respectively. Moreover, improved BP neural network based on a genetic algorithm has shown highly superior performance in terms of convergence speed and low error rate. 相似文献
8.
9.
A diode laser-pumped acoustic-optic Q-switched Nd:YAG master-oscillator power amplifier laser is presented. The laser is quasi continuously pumped at 1.1 kHz with a pulse width of 172 μs, and the ultrasonic frequency of the AO Q-switcher is set at a higher value (53 kHz). The master oscillator is designed as a thermally near-unstable-resonator, which presents an average output power of 48 W with a beam quality value of M2 = 1.41 and a Q-switching pulse duration of 121 ns. The maximum average power of the MOPA system is 654 W, and the beam quality is M2 = 6. 相似文献
10.
A. Ul-Hamid H. DafallaA. Quddus H. SaricimenL.M. Al-Hadhrami 《Applied Surface Science》2011,257(22):9251-9259
The surface of carbon steel was modified by electrochemical deposition of Ni in a standard Watt's bath using dc and pulse plating electrodeposition. The aim was to compare the microstructure and surface mechanical properties of the deposit obtained by both techniques. Materials characterization was conducted using field emission scanning electron microscope fitted with scanning transmission electron detector, atomic force microscope and X-ray diffractometer. Nanoindentation hardness, elastic modulus, adhesion, coefficients of friction and wear rates were determined for both dc and pulse electrodeposits. Experimental results indicate that pulse electrodeposition produced finer Ni grains compared to dc plating. Size of Ni grains increased with deposition. Both dc and pulse deposition resulted in grain growth in preferred (2 0 0) orientation. However, presence of Ni (1 1 1) grains increased in deposits produced by pulse deposition. Pulse plated Ni exhibited higher hardness, creep and coefficient of friction and lower modulus of elasticity compared to dc plated Ni. 相似文献