全文获取类型
收费全文 | 4674篇 |
免费 | 162篇 |
国内免费 | 29篇 |
专业分类
化学 | 2577篇 |
晶体学 | 51篇 |
力学 | 181篇 |
数学 | 1140篇 |
物理学 | 916篇 |
出版年
2023年 | 42篇 |
2022年 | 125篇 |
2021年 | 137篇 |
2020年 | 127篇 |
2019年 | 157篇 |
2018年 | 155篇 |
2017年 | 144篇 |
2016年 | 194篇 |
2015年 | 151篇 |
2014年 | 205篇 |
2013年 | 338篇 |
2012年 | 309篇 |
2011年 | 324篇 |
2010年 | 178篇 |
2009年 | 197篇 |
2008年 | 237篇 |
2007年 | 205篇 |
2006年 | 156篇 |
2005年 | 126篇 |
2004年 | 129篇 |
2003年 | 95篇 |
2002年 | 89篇 |
2001年 | 79篇 |
2000年 | 65篇 |
1999年 | 45篇 |
1998年 | 33篇 |
1997年 | 38篇 |
1996年 | 57篇 |
1995年 | 45篇 |
1994年 | 43篇 |
1993年 | 48篇 |
1992年 | 40篇 |
1991年 | 37篇 |
1990年 | 31篇 |
1989年 | 24篇 |
1988年 | 29篇 |
1987年 | 40篇 |
1986年 | 39篇 |
1985年 | 36篇 |
1984年 | 27篇 |
1983年 | 25篇 |
1982年 | 32篇 |
1981年 | 29篇 |
1980年 | 22篇 |
1979年 | 37篇 |
1978年 | 28篇 |
1977年 | 21篇 |
1976年 | 23篇 |
1975年 | 20篇 |
1974年 | 14篇 |
排序方式: 共有4865条查询结果,搜索用时 15 毫秒
81.
K. D. Duch M. Heel H. Kalinowsky F. Kayser E. Klempt B. May O. Schreiber P. Weidenauer M. Ziegler D. Bailey S. Barlag J. M. Butler U. Gastaldi R. Landua C. Sabev W. Dahme F. Feld-Dahme U. Schaefer W. R. Wodrich J. C. Bizot B. Delcourt J. Jeanjean H. Nguyen E. G. Auld D. A. Axen K. L. Erdman B. Howard R. Howard B. L. White S. Ahmad M. Comyn G. M. Marshall G. Beer L. P. Robertson M. Botlo C. Laa H. Vonach C. Amsler M. Doser J. Riedlberger U. Straumann P. Truöl ASTERIX Collaboration 《Zeitschrift fur Physik C Particles and Fields》1989,45(2):223-234
Antiproton-proton annihilation at rest in a gaseous H2 target at NTP into the final state π+ π? K ± π? (K 0) with an undetectedK 0 or \(\bar K^0 \) has been investigated. We observe theE(1420) resonance in the invariant mass spectrum (K 0)miss K ± π? with massM E =1413±8 MeV/c2 and widthГ E =62 ± 16MeV/c2 and find evidence for the production of thef 1(1285). The absolute branching ratio of \(\bar p\) p → π+ π? E 0,E 0 →K 0 L K ± π ? at (61±6)%P wave annihilation is (3.0±0.9)·10?4 of all annihilations. The observed suppression of theE production fromP wave with respect to theS wave together with some simple selection rules suggest that the quantum numbers of theE(1420) areJ pc=0?+ and not I++. 相似文献
82.
Liu ZQ McCoy BK Wang ST Pindak R Caliebe W Barois P Fernandes P Nguyen HT Hsu CS Wang S Huang CC 《Physical review letters》2007,99(7):077802
Employing resonant x-ray diffraction, we observed unique pitch evolutions in the smectic-C*(alpha) phase in mixtures of two antiferroelectric liquid crystals. Our results show that the pitch in this phase continuously evolves across 4 layers, contradicting a theoretical model that predicts that the smectic-C*(FI2) phase intervenes in the smectic-C*(alpha) phase. The phase sequences we found can be explained by another model that includes one type of long-range interaction among smectic layers. 相似文献
83.
Hopf bifurcation control via a dynamic state-feedback control 总被引:1,自引:0,他引:1
To relocate two Hopf bifurcation points, simultaneously, to any desired locations in n-dimensional nonlinear systems, a novel dynamic state-feedback control law is proposed. Analytical schemes to determine the control gains according to the conditions for the emergence of Hopf bifurcation are derived. To verify the effectiveness of the proposed control law, numerical examples are provided. 相似文献
84.
Cletus A D'Souza Vikramjit Chopra Richard Varhol Yuan-Yun Xie Slavita Bohacec Yongjun Zhao Lisa LC Lee Mikhail Bilenky Elodie Portales-Casamar An He Wyeth W Wasserman Daniel Goldowitz Marco A Marra Robert A Holt Elizabeth M Simpson Steven JM Jones 《BMC neuroscience》2008,9(1):1-14
Background
We have recorded responses from single neurons in murine visual cortex to determine the effectiveness of the input from the two murine cone photoreceptor mechanisms and whether there is any unique selectivity for cone inputs at this higher region of the visual system that would support the possibility of colour vision in mice. Each eye was stimulated by diffuse light, either 370 (strong stimulus for the ultra-violet (UV) cone opsin) or 505 nm (exclusively stimulating the middle wavelength sensitive (M) cone opsin), obtained from light emitting diodes (LEDs) in the presence of a strong adapting light that suppressed the responses of rods.Results
Single cells responded to these diffuse stimuli in all areas of striate cortex. Two types of responsive cells were encountered. One type (135/323 – 42%) had little to no spontaneous activity and responded at either the on and/or the off phase of the light stimulus with a few impulses often of relatively large amplitude. A second type (166/323 – 51%) had spontaneous activity and responded tonically to light stimuli with impulses often of small amplitude. Most of the cells responded similarly to both spectral stimuli. A few (18/323 – 6%) responded strongly or exclusively to one or the other spectral stimulus and rarely in a spectrally opponent manner.Conclusion
Most cells in murine striate cortex receive excitatory inputs from both UV- and M-cones. A small fraction shows either strong selectivity for one or the other cone mechanism and occasionally cone opponent responses. Cells that could underlie chromatic contrast detection are present but extremely rare in murine striate cortex. 相似文献85.
In this work, we propose a scheme to realize a joint remote preparation of an arbitrary three-qubit state using six EPR-type pairs as the shared quantum resource. By determining the right measurement bases for the preparers and right ancilla-assisted unitary transformation/recovery operations for the receiver, our scheme applies to the most general case when all the coefficients of the state to be prepared and the EPR-type pairs are complex. The total success probability is found to be dependent only on the “smaller” coefficients of the EPR-type pairs shared between the receiver and one of the preparers. 相似文献
86.
Morphological and chemical properties of both the surface and interface of poly(vinylidene fluoride)/poly(methyl methacrylate)-co-poly(ethyl acrylate) (PVDF/PMMA-co-PEA) blend films have been investigated before and after the samples were exposed to ultraviolet (UV) irradiation using a xenon arc lamp at 50 °C and 9% relative humidity (RH) for 7 months. Surface and interfacial morphologies were studied by atomic force microscopy (AFM). Chemical composition information was obtained by confocal Raman microscopy, attenuated total reflection-FTIR spectroscopy (ATR-FTIR), X-ray photoelectron spectroscopy (XPS), and contact angle measurements. Results show an enrichment of the PVDF material at the air surface, while the acrylic copolymer enriches the interface. Blends having greater than 50% mass fraction of PVDF show little change in the surface morphology after UV exposure for 7 months. However, for a lower PVDF content, blends exhibit significant degradation of PMMA-co-PEA copolymer and a much rougher surface after UV exposure. Microstructural changes in the PVDF spherulites are also observed after UV degradation. It is found that the surface and interfacial morphologies are correlated with the chemical properties. 相似文献
87.
Nguyen Hoa Hong Joe Sakai Ngo Thu Huong Virginie Brizé 《Journal of magnetism and magnetic materials》2006
Laser-ablated Co-doped In2O3 thin films were fabricated under various growth conditions on R-cut Al2O3 and MgO substrates. All Co:In2O3 films are well-crystallized, single phase, and room temperature ferromagnetic. Co atoms were well substituted for In atoms, and their distribution is greatly uniform over the whole thickness of the films. Films grown at 550 °C showed the largest magnetic moment of about 0.5 μB/Co, while films grown at higher temperatures have magnetic moments of one order smaller. The observed ferromagnetism above room temperature in Co:In2O3 thin films has confirmed that doping few percent of magnetic elements such as Co into In2O3 could result in a promising magnetic material. 相似文献
88.
Ngo Ngoc Ha Nguyen Truong Giang Tran Ngoc Khiem Nguyen Duc Dung Tom Gregorkiewicz 《固体物理学:研究快报》2016,10(11):824-827
Photogenerated carriers in Si–Ge alloy nanocrystals (NCs) prepared by co‐sputtering method were investigated by mean of transient induced absorption. The carrier relaxation features multiple components, with three decay life times of τ ≈ 600 fs, 12 ps, and 15 ns, established for Si0.2Ge0.8 alloy NCs of a mean crystal size of 9 nm and standard deviation of 3 nm. Deep carrier traps, identified at the boundary between the NCs and the SiO2 host with the ionization energy of about 1 eV, are characterized by a long‐range Coulombic potential. These are responsible for rapid depletion of free carrier population within a few picoseconds after the excitation, which explains the low emissivity of the investigated materials, and also sheds light on the generally low luminescence of Si/Ge and Ge NCs. (© 2016 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim) 相似文献
89.
M.D. Stewart Jr. H.Q. Nguyen S.M. Hollen Aijun Yin J.M. Xu J.M. Valles Jr. 《Physica C: Superconductivity and its Applications》2009,469(13):774-777
We have measured the thickness dependence of the superconducting critical temperature, Tc(dBi), in amorphous Bi/Sb films patterned with a regular array of holes as well as nanoscale thickness variations. We find that the mean field Tc is suppressed relative to simultaneously produced unstructured films of the same thickness. Surprisingly, however, the functional form for Tc(dBi), remains unaffected. The role of the thickness variations in suppressing Tc is compared to the role of the holes, through parameterization of the surface, as measured through AFM/SEM and a proximity effect calculation. These results suggest that these two nanoscale modifications suppress Tc about equally and are consistent with Tc being determined on a microscopic length scale. 相似文献
90.
Hong Van Nguyen Duong Thuy Tran Hung Khac Pham 《The European Physical Journal B - Condensed Matter and Complex Systems》2017,90(2):37
Network structure as well as structural and compositional heterogeneities in aluminosilicate (Al2O3-2SiO2) under compression is investigated by analysis and visualization of simulation data. Structural and compositional heterogeneities are clarified through analysis of topology structure and size distribution of TO x -clusters (T = Si, Al; x = 3, 4, 5, 6) as well as OT y -clusters (y = 2, 3, 4). The TO x -cluster can be considered as TO x -grains. It appears that the structure of aluminosilicate is the mixture of TO x -grains with a different short-range order structure and this is the origin of structural heterogeneity. Regarding their composition, the OSi y - and OAl y -clusters can be considered as silica- and alumina-grains respectively, and the structure of aluminosilicate can thus be considered to be formed from silica- and alumina-grains. This results in compositional heterogeneity. Moreover, the degree of polymerization and polyamorphism as well as dynamic heterogeneity is also discussed in detail. 相似文献