全文获取类型
收费全文 | 12662篇 |
免费 | 1633篇 |
国内免费 | 1195篇 |
专业分类
化学 | 6300篇 |
晶体学 | 76篇 |
力学 | 509篇 |
综合类 | 45篇 |
数学 | 1052篇 |
物理学 | 2969篇 |
综合类 | 4539篇 |
出版年
2024年 | 30篇 |
2023年 | 264篇 |
2022年 | 376篇 |
2021年 | 432篇 |
2020年 | 533篇 |
2019年 | 425篇 |
2018年 | 410篇 |
2017年 | 345篇 |
2016年 | 469篇 |
2015年 | 525篇 |
2014年 | 688篇 |
2013年 | 771篇 |
2012年 | 918篇 |
2011年 | 976篇 |
2010年 | 723篇 |
2009年 | 658篇 |
2008年 | 682篇 |
2007年 | 646篇 |
2006年 | 639篇 |
2005年 | 511篇 |
2004年 | 387篇 |
2003年 | 353篇 |
2002年 | 477篇 |
2001年 | 344篇 |
2000年 | 315篇 |
1999年 | 385篇 |
1998年 | 311篇 |
1997年 | 301篇 |
1996年 | 285篇 |
1995年 | 261篇 |
1994年 | 199篇 |
1993年 | 154篇 |
1992年 | 143篇 |
1991年 | 116篇 |
1990年 | 98篇 |
1989年 | 91篇 |
1988年 | 104篇 |
1987年 | 51篇 |
1986年 | 38篇 |
1985年 | 23篇 |
1984年 | 12篇 |
1983年 | 3篇 |
1981年 | 6篇 |
1980年 | 1篇 |
1957年 | 3篇 |
1955年 | 1篇 |
1935年 | 1篇 |
1931年 | 1篇 |
1930年 | 3篇 |
1922年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
941.
HANLu ZHOUMan-li TIANJing KURTRothermel 《武汉大学学报:自然科学英文版》2004,9(6):931-934
A new algorithm called spatially aware routing algorithm with enhanced learning (SAREL) is proposed to guarantee the rationality of route selecting in inter-vehicle communication scenario. Firstly, the traffic model is discussed and set up by using Poisson distribution. Then we analyze the process of traffic evaluation with enhanced learning, and exploit movement estimation to assist state memorization. The improvement of algorithm is provided at last compared with our previous work. Simulation results show that SAREL algorithm could achieve better performance in packet delivery ratio, especially when network connection ratio is average. 相似文献
942.
LITai-quan TIANMao XUJi-sheng 《武汉大学学报:自然科学英文版》2004,9(6):909-912
By analyzing the current distribution of Bow-Tie amerma used in short-pulse ground penetrating radar, the methods of antenna load and driving are presented in this paper to reduce strength of reflective wave both at antenna end and excitation point. The numerical simulation results show the strength oi reflective wave is smaller than -55dB comparing with the driving wave when the methods are adopted. 相似文献
943.
Zhao J Tian S Wang Q Liu X Jiang S Ji X An L Jiang B 《The European physical journal. E, Soft matter》2005,16(1):49-56
The surface topography of thin diblock copolymer films is studied by atomic
force microscopy (AFM). With AFM an island-to-ribbon transition is observed
for symmetric polystyrene-b-poly (4-vinylpyridine) (PS-b-P4VP) on mica with
increasing solution concentration. Our study also demonstrates how the
formation of the pattern strongly depends on the copolymer composition based
on the volume fraction. The substrate and solvent used both have great
effects on the morphology of the thin films. Only by using highly polar
substrate (mica), can we gain regular pattern. The reason why the regular
islands cannot be obtained with symmetric PS-b-P4VP on graphite is also
explained. On mica using nonselective and selective solvents, a rather
regular pattern can be obtained. The difference is only in the solution
concentration for forming regular patterns. 相似文献
944.
Core/shell quantum-dot-photosensitized nano-TiO2 films: fabrication and application to the damage of cells and DNA 总被引:4,自引:0,他引:4
Lu ZX Zhang ZL Zhang MX Xie HY Tian ZQ Chen P Huang H Pang DW 《The journal of physical chemistry. B》2005,109(47):22663-22666
Through the use of monodisperse core/shell quantum dots (QDs) as photosensitizers for the first time, a novel strategy for the fabrication of QD-photosensitized nano-TiO2 films was demonstrated. Core/shell QDs were self-assembled on nano-TiO2 films through carboxyls as anchoring groups to metal oxides. Atomic force microscopy and some other experiments showed the fabrication strategy is successful. Reactive oxygen species detection experiments indicated that such films have photosensitization ability. The results of bactericidal and DNA damage experiments demonstrate that such films have excellent photoactivity. 相似文献
945.
A monolithic silica based strong cation-exchange stationary phase was successfully prepared for capillary electrochromatography. The monolithic silica matrix from a sol-gel process was chemically modified by treatment with 3-mercaptopropyltrimethoxysilane followed by a chemical oxidation procedure to produce the desired function. The strong cation-exchange stationary phase was characterized by its substantial and stable electroosmotic flow (EOF), and it was observed that the EOF value of the prepared column remained almost unchanged at different buffer pH values and slowly decreased with increasing phosphate concentration in the mobile phase. The monolithic silica column with strong cation-exchange stationary phase has been successfully employed in the electrochromatographic separation of beta-blockers and alkaloids extracted from traditional Chinese medicines (TCMs). The column efficiencies for the tested beta-blockers varied from 210,000 to 340,000 plates/m. A peak compression effect was observed for atenolol with the mobile phase having a low phosphate concentration. 相似文献
946.
Tian CS Qian D Wu D He RH Wu YZ Tang WX Yin LF Shi YS Dong GS Jin XF Jiang XM Liu FQ Qian HJ Sun K Wang LM Rossi G Qiu ZQ Shi J 《Physical review letters》2005,94(13):137210
The body-centered-cubic (bcc) phase of Ni, which does not exist in nature, has been achieved as a thin film on GaAs(001) at 170 K via molecular beam epitaxy. The bcc Ni is ferromagnetic with a Curie temperature of 456 K and possesses a magnetic moment of 0.52+/-0.08 micro(B)/atom. The cubic magnetocrystalline anisotropy of bcc Ni is determined to be +4.0x10(5) ergs x cm(-3), as opposed to -5.7x10(4) ergs x cm(-3) for the naturally occurring face-centered-cubic (fcc) Ni. This sharp contrast in the magnetic anisotropy is attributed to the different electronic band structures between bcc Ni and fcc Ni, which are determined using angle-resolved photoemission with synchrotron radiation. 相似文献
947.
Guanghai?GuoEmail author Yuanxing?Gui Jianxiang?Tian 《General Relativity and Gravitation》2005,37(7):1323-1330
The real scalar field equation between the outer black hole horizon and the cosmological horizon is solved in the extreme Reissner-Nordström de Sitter (RNdS) space. We use an accurate approximation, the polynomial approximation, to approximate the tortoise coordinate x(r) in order to get the inverse function r = r(x) and then to solve the wave equation. The case where the two horizons are very close to each other is discussed in detail. We find that the wave function is harmonic only in the very small regions near the horizons, and the amplitude decreases remarkably near the potential peak because of the effect of the potential. Furthermore, it is found that the height of the potential increases as the cosmological constant Λ decreases, and the wave amplitude will decrease more remarkably with less Λ. 相似文献
948.
A data-processing technique is proposed for use with conventional frequency-chirped absorption spectroscopy to ensure accurate mapping of spectral features into time-domain signatures with arbitrarily fast readout chirp rates. This technique recovers the spectrum from a signal that is distorted owing to the fast chirp rate and therefore facilitates fast measurement of the spectral features over a broad spectral range with high resolution. Both numerical simulations and experimental results are presented. 相似文献
949.
In some perfect periodic structures classical motion exhibits deterministic diffusion. For such systems we present the weak localization theory. As a manifestation for the velocity autocorrelation function a universal power law decay is predicted to appear at four Ehrenfest times. This deterministic weak localization is robust against weak quenched disorders, which may be confirmed by coherent backscattering measurements of periodic photonic crystals. 相似文献
950.
Tian XC Ban Y Abe K Abe K Aihara H Arinstein K Asano Y Aulchenko V Aushev T Bakich AM Banerjee S Barberio E Barbero M Bay A Bedny I Bitenc U Bizjak I Blyth S Bondar A Bozek A Bracko M Brodzicka J Browder TE Chang P Chao Y Chen A Chen KF Chen WT Cheon BG Chistov R Choi SK Choi Y Choi YK Chuvikov A Dalseno J Danilov M Dash M Dong LY Drutskoy A Eidelman S Enari Y Fang F Fratina S Gabyshev N Gershon T Gokhroo G Golob B Gorisek A Haba J Hara T Hayasaka K Hayashii H Hazumi M Hokuue T Hoshi Y Hou S 《Physical review letters》2005,95(23):231801
Using 281 fb-1 of data from the Belle experiment recorded at or near the (4S) resonance, we have measured the rates of the "wrong-sign" decays D0 --> K+ pi- pi0 and D0 --> K+ pi- pi+ pi- relative to those of the Cabibbo-favored decays D0 --> K- pi+ pi0 and D0 --> K- pi+ pi+ pi-. These wrong-sign decays proceed via a doubly Cabibbo-suppressed amplitude or via D0-D0 mixing; the latter has not yet been observed. We obtain R(WS)(K pi pi0) = [0.229 +/- 0.015(stat)(+0.013)(-0.009)(syst)]% and R(WS)(K3pi) = [0.320 +/- 0.018(stat)(+0.018)(0.013)(syst)]%. The CP asymmetries are measured to be -0.006 +/- 0.053 and -0.018 +/- 0.044 for the K+ pi- pi0 and K+ pi- pi+ pi- final states, respectively. 相似文献