全文获取类型
收费全文 | 17117篇 |
免费 | 2695篇 |
国内免费 | 1928篇 |
专业分类
化学 | 12443篇 |
晶体学 | 188篇 |
力学 | 1184篇 |
综合类 | 138篇 |
数学 | 2033篇 |
物理学 | 5754篇 |
出版年
2024年 | 39篇 |
2023年 | 331篇 |
2022年 | 375篇 |
2021年 | 530篇 |
2020年 | 630篇 |
2019年 | 656篇 |
2018年 | 515篇 |
2017年 | 533篇 |
2016年 | 740篇 |
2015年 | 738篇 |
2014年 | 921篇 |
2013年 | 1141篇 |
2012年 | 1528篇 |
2011年 | 1553篇 |
2010年 | 1061篇 |
2009年 | 936篇 |
2008年 | 1086篇 |
2007年 | 977篇 |
2006年 | 980篇 |
2005年 | 796篇 |
2004年 | 602篇 |
2003年 | 549篇 |
2002年 | 546篇 |
2001年 | 459篇 |
2000年 | 347篇 |
1999年 | 363篇 |
1998年 | 297篇 |
1997年 | 271篇 |
1996年 | 301篇 |
1995年 | 236篇 |
1994年 | 205篇 |
1993年 | 162篇 |
1992年 | 171篇 |
1991年 | 176篇 |
1990年 | 130篇 |
1989年 | 128篇 |
1988年 | 82篇 |
1987年 | 72篇 |
1986年 | 85篇 |
1985年 | 62篇 |
1984年 | 56篇 |
1983年 | 44篇 |
1982年 | 32篇 |
1981年 | 31篇 |
1980年 | 29篇 |
1978年 | 24篇 |
1977年 | 25篇 |
1976年 | 23篇 |
1974年 | 20篇 |
1973年 | 26篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
991.
Po‐Chun Chen Yu‐Chien Chiu Zhi‐Wei Zheng Chun‐Hu Cheng Yung‐Hsien Wu 《固体物理学:研究快报》2016,10(12):919-923
We reported the characteristics of p‐type tin‐oxide (SnO) thin film transistors (TFTs) upon illumination with visible light. Our p‐type TFT device using the SnO film as the active channel layer exhibits high sensitivity toward the blue‐light with a high light/dark read current ratio (Ilight/Idark) of 8.2 × 103 at a very low driven voltage of <3 V. Since sensing of blue‐light radiation is very critical to our eyes, the proposed p‐type SnO TFTs with high sensitivity toward the blue‐light show great potential for future blue‐light detection applications.
992.
For the exploration of gas hydrate resources by measuring the dissolved methane concentration in seawater, a continuous-wave cavity ringdown spectroscopy (CW-CRDS) experimental setup was constructed for trace methane detection. A current-modulation method, rather than a cavity-modulation method using an optical switch and a piezoelectric transducer, was employed to realize the cavity excitation and shutoff. Such a current-modulation method enabled the improvement of the experimental setup construction and stability, and the system size and stability are critical for a sensor to be deployed underwater. Ringdown data acquisition and processing were performed, followed by an evaluation of the experimental setup stability and sensitivity. The obtained results demonstrate that great errors are introduced when a large fitting window is selected if the analog-to-digital converter has an insufficient resolution. The ringdown spectrum of methane corresponding to the 2v 3 band R(4) branch was captured, and the methane concentration in lab air was determined to be 2.06 ppm. Further experiments for evaluating the quantitative ability of this CW-CRDS experimental setup are underway from which a high-sensitivity methane sensor that can be combined with a degassing system is expected. 相似文献
993.
Xu X Wu Y Sun B Huang Q Cheng J Steel DG Bracker AS Gammon D Emary C Sham LJ 《Physical review letters》2007,99(9):097401
Quantum computation requires a continuous supply of rapidly initialized qubits for quantum error correction. Here, we demonstrate fast spin state initialization with near unity efficiency in a singly charged quantum dot by optically cooling an electron spin. The electron spin is successfully cooled from 5 to 0.06 K at a magnetic field of 0.88 T applied in Voigt geometry. The spin cooling rate is of order 10(9) s-1, which is set by the spontaneous decay rate of the excited state. 相似文献
994.
In this Letter, we demonstrate that nonadiabatic dynamics of molecular scattering from metal surfaces can be efficiently simulated by semiclassical Gaussian wave packet propagation on a local complex potential. The method relies on the wideband limit decoupling of the nuclear equations of motion on different electronic states. If the continuum diabatic potential surfaces are assumed to be parallel, the number of Gaussian wave packets spawned scales at most linearly with propagation time, allowing efficient propagation of nuclear dynamics. 相似文献
995.
Abelev BI Aggarwal MM Ahammed Z Anderson BD Arkhipkin D Averichev GS Bai Y Balewski J Barannikova O Barnby LS Baudot J Baumgart S Belaga VV Bellingeri-Laurikainen A Bellwied R Benedosso F Betts RR Bhardwaj S Bhasin A Bhati AK Bichsel H Bielcik J Bielcikova J Bland LC Blyth SL Bombara M Bonner BE Botje M Bouchet J Brandin AV Bravar A Burton TP Bystersky M Cadman RV Cai XZ Caines H Calderón de la Barca Sánchez M Callner J Catu O Cebra D Chajecki Z Chaloupka P Chattopadhyay S Chen HF Chen JH 《Physical review letters》2007,99(11):112301
We present first measurements of the phi-meson elliptic flow (v2(pT)) and high-statistics pT distributions for different centralities from radical sNN=200 GeV Au+Au collisions at RHIC. In minimum bias collisions the v2 of the phi meson is consistent with the trend observed for mesons. The ratio of the yields of the Omega to those of the phi as a function of transverse momentum is consistent with a model based on the recombination of thermal s quarks up to pT approximately 4 GeV/c, but disagrees at higher momenta. The nuclear modification factor (R CP) of phi follows the trend observed in the K S 0 mesons rather than in Lambda baryons, supporting baryon-meson scaling. These data are consistent with phi mesons in central Au+Au collisions being created via coalescence of thermalized s quarks and the formation of a hot and dense matter with partonic collectivity at RHIC. 相似文献
996.
Y.-X. Ping B. Zhang Z. Cheng 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,44(1):175-180
The generation of continuous variable entanglement via
atomic coherence in a two-mode three-level cascade atomic system
is discussed according to the entanglement criterion proposed by
Duan et al. [Phys. Rev. Lett. 84, 2722 (2000)].
Atomic coherence between the top and bottom levels is induced with
two photons of a strong external pump field. It shows that
entanglement for the two-mode field in the cavity can be generated
under certain conditions. Moreover, by means of the input-output
theory, we show that the two-mode entanglement could also be
approached at the output. 相似文献
997.
P. Müller‐Buschbaum J. Perlich M. M. Abul Kashem L. Schulz S. V. Roth Y. J. Cheng J. S. Gutmann 《固体物理学:研究快报》2007,1(3):119-121
Nanostructures formed in a titanium dioxide (TiO2)–poly(styrene)‐block‐poly(ethyleneoxide) nanocomposite film on top of fluor‐doped tin oxide (FTO) layers are investigated. The combinatorial approach is based on probing a wedge‐shaped FTO‐gradient with grazing incidence small angle X‐ray scattering (GISAXS) in combination with a moderate micro‐focus X‐ray beam. The characteristic lateral length is given by adjacent nanowire‐shaped TiO2 regions. It decreases from 200 nm on the thick FTO layer to 90 nm on the bare glass surface.
998.
A cesium 6S(1/2) --> 8S(1/2) two-photon-transition (TPT)-stabilized 822.5 nm diode laser is reported for the first time to our knowledge. Allan deviation of 4.4 x 10(-13) (60 s) was achieved, and the possible systematic errors were evaluated as smaller than 2 kHz. We demonstrate that the cesium TPT-stabilized diode laser could be a reliable frequency reference at 822.5 nm wavelength. 相似文献
999.
Fan X Medved M Karczmar GS Yang C Foxley S Arkani S Recant W Zamora MA Abe H Newstead GM 《Magnetic resonance imaging》2007,25(5):593-603
The purpose of this study was to test whether an empirical mathematical model (EMM) of dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) can distinguish between benign and malignant breast lesions. A modified clinical protocol was used to improve the sampling of contrast medium uptake and washout. T(1)-weighted DCE magnetic resonance images were acquired at 1.5 T for 22 patients before and after injection of Gd-DTPA. Contrast medium concentration as a function of time was calculated over a small region of interest containing the most rapidly enhancing pixels. Then the curves were fitted with the EMM, which accurately described contrast agent uptake and washout. Results demonstrate that benign lesions had uptake (P<2.0 x 10(-5)) and washout (P<.01) rates of contrast agent significantly slower than those of malignant lesions. In addition, secondary diagnostic parameters, such as time to peak of enhancement, enhancement slope at the peak and curvature at the peak of enhancement, were derived mathematically from the EMM and expressed in terms of primary parameters. These diagnostic parameters also effectively differentiated benign from malignant lesions (P<.03). Conventional analysis of contrast medium dynamics, using a subjective classification of contrast medium kinetics in lesions as "washout," "plateau" or "persistent" (sensitivity=83%, specificity=50% and diagnostic accuracy=72%), was less effective than the EMM (sensitivity=100%, specificity=83% and diagnostic accuracy=94%) for the separation of benign and malignant lesions. In summary, the present research suggests that the EMM is a promising alternative method for evaluating DCE-MRI data with improved diagnostic accuracy. 相似文献
1000.
Kai‐Hsuan Hsieh Chih‐Ying Hsu I‐Ju Hung Chih‐Ling Yeh Yau‐Hung Chen Chien‐Chung Cheng 《中国化学会会志》2021,68(1):34-38
Liposomes composed of cell‐penetrating peptide derivatives increased transport across the cell membrane. Conjugating rhodamine to a cell‐penetrating peptide increased the toxicity of rhodamine in E. coli and zebrafish embryos. A similar total protein inhibition pattern with different intensities, indicating that the interaction pathways of the rho‐KTTKS‐CONH2 monomer and liposomes were the same. It suggests that the rho‐KTTKS‐CONH2 liposomes showed higher toxicity because better transport across the cell membrane increased the effective concentration inside cells. The staining of zebrafish embryos using rho‐KTTKS‐CONH2 liposomes showed a longer retention time, suggesting that it can penetrate deeper tissues or organs in zebrafish. 相似文献