全文获取类型
收费全文 | 520篇 |
免费 | 12篇 |
国内免费 | 1篇 |
专业分类
化学 | 254篇 |
力学 | 11篇 |
数学 | 168篇 |
物理学 | 100篇 |
出版年
2024年 | 1篇 |
2023年 | 10篇 |
2022年 | 5篇 |
2021年 | 10篇 |
2020年 | 8篇 |
2019年 | 15篇 |
2018年 | 11篇 |
2017年 | 15篇 |
2016年 | 27篇 |
2015年 | 12篇 |
2014年 | 16篇 |
2013年 | 39篇 |
2012年 | 37篇 |
2011年 | 41篇 |
2010年 | 28篇 |
2009年 | 36篇 |
2008年 | 41篇 |
2007年 | 30篇 |
2006年 | 22篇 |
2005年 | 25篇 |
2004年 | 13篇 |
2003年 | 18篇 |
2002年 | 12篇 |
2001年 | 10篇 |
2000年 | 2篇 |
1999年 | 4篇 |
1998年 | 1篇 |
1997年 | 3篇 |
1996年 | 1篇 |
1995年 | 4篇 |
1994年 | 2篇 |
1993年 | 3篇 |
1992年 | 3篇 |
1991年 | 4篇 |
1990年 | 1篇 |
1989年 | 2篇 |
1988年 | 2篇 |
1987年 | 2篇 |
1984年 | 1篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1979年 | 2篇 |
1978年 | 1篇 |
1977年 | 2篇 |
1976年 | 2篇 |
1973年 | 2篇 |
1969年 | 1篇 |
1968年 | 2篇 |
1919年 | 2篇 |
排序方式: 共有533条查询结果,搜索用时 15 毫秒
91.
We study the strong convergence of two viscosity iteration processes for pseudo-contractive semigroup and for ?-strongly pseudo-contractive mapping in uniformly convex Banach spaces with uniformly Gâteaux differentiable norm. As special cases, we get strong convergence of two viscosity iteration processes for approximating common fixed points of nonexpansive semigroups in certain Banach spaces. The results presented in this paper extend and generalize previous results. 相似文献
92.
Juntao Li Liam O’Faolain Sebastian A. Schulz Thomas F. Krauss 《Photonics and Nanostructures》2012,10(4):589-593
We have designed slow light photonic crystal waveguides operating in a low loss and constant dispersion window of Δλ = 2 nm around λ = 1565 nm with a group index of ng = 60. We experimentally demonstrate a relatively low propagation loss, of 130 dB/cm, for waveguides up to 800 μm in length. This result is particularly remarkable given that the waveguides were written on an electron-beam lithography tool with a writefield of 100 μm that exhibits stitching errors of typically 10–50 nm. We reduced the impact of these stitching errors by introducing “slow–fast–slow” mode conversion interfaces and show that these interfaces reduce the loss from 320 dB/cm to 130 dB/cm at ng = 60. This significant improvement highlights the importance of the slow–fast–slow method and shows that high performance slow light waveguides can be realised with lengths much longer than the writing field of a given e-beam lithography tool. 相似文献
93.
In this paper we present multi-channel chirp measurements of wide-band sources, using a programmable Fourier-domain optical processor (FDOP) as a near-perfect linear frequency discriminator element followed by a fast photodiode and electrical sampling oscilloscope. The electric field of a 10.7 Gbit/s phase-encoded data source and a directly modulated laser diode are simultaneously interrogated with this measurement system. The constellation diagram of the phase-encoded data source is demonstrated, and a comparison with another phase-sensitive measurement technique is performed. Additionally, an extension to this technique is demonstrated in which the time-resolved chirp of a picosecond-duration mode-locked laser diode with a 260 GHz spectral bandwidth is characterised using the FDOP and a high-bandwidth optical sampling oscilloscope. This measurement ensemble has sufficient temporal resolution to characterise random or repetitive data signals up to 100GBaud. 相似文献
94.
Aggarwal VK Ball LT Carobene S Connelly RL Hesse MJ Partridge BM Roth P Thomas SP Webster MP 《Chemical communications (Cambridge, England)》2012,48(74):9230-9232
The expedient enantioselective synthesis of 5 bisabolane sesquiterpenes has been achieved using a common, one-pot lithiation-borylation reaction of secondary benzylic carbamates and either protodeboronation or oxidation to give the natural products in fewer than 5 steps, with high yield and >94?:?6 er. 相似文献
95.
J.A. Koch N. Izumi L.A. Welser R.C. Mancini S.W. Haan R.W. Lee P.A. Amendt T.W. Barbee Jr. S. Dalhed K. Fujita I.E. Golovkin L. Klein O.L. Landen F.J. Marshall D.D. Meyerhofer H. Nishimura Y. Ochi S. Regan T.C. Sangster V. Smalyuk R. Tommasini 《High Energy Density Physics》2008,4(1-2):1-17
We have measured time-integrated and time-gated electron temperature (Te) and density (Ne) spatial profiles from indirect-drive implosions. In our experiments, we used a multiple-pinhole two-dimensional imaging spectrometer to obtain multispectral X-ray images of the imploded core. Quantitative comparisons between quasi-monochromatic images in different energy bands allowed Te and Ne spatial profiles to be determined using two independent and validated techniques: a multi-objective search and reconstruction analysis, and an analytical analysis. We then compared the results to a simple one-dimensional (1D) mix-free hydrodynamics simulation in order to evaluate the ability of such a model to predict our experiments. Our data show spatial Te profiles that are qualitatively consistent with the predictions of our 1D simulations, but we observe central cores that are 10–25% cooler and emit X-rays as late as 200 ps after peak compression. We infer time-gated spatial Ne profiles that are consistent with our 1D simulations near the times of peak compression, but we find significant disagreement between time-integrated data and 1D simulation predictions at large radii. Careful analysis of the time-gated and time-integrated Te and Ne spatial profiles, together with streaked X-ray emission spectra from core and shell dopants, suggests mixing of shell material into the core is an important process that our 1D hydrodynamics simulations fail to capture, and comparison between image data and a simple analytical model suggests that 2–5 μm of the initial inner shell thickness mixes into the core during the time period of significant X-ray emission. This mix width is consistent with the predictions of a growth-factor analysis that treats instability growth seeded by capsule surface roughness, and points to the need to consider time-dependent mixing effects when interpreting Te and Ne spatial profiles derived from multispectral X-ray image data, particularly at large radii where mixing effects will be most significant. 相似文献
96.
M.N. Mineva M. Hellström M. Bernas J. Gerl H. Grawe M. Pfützner P.H. Regan M. Rejmund D. Rudolph F. Becker C.R. Bingham T. Enqvist B. Fogelberg H. Gausemel H. Geissel J. Genevey M. Górska R. Grzywacz K. Hauschild Z. Janas I. Kojouharov Y. Kopatch A. Korgul W. Korten J. Kurcewicz M. Lewitowicz R. Lucas H. Mach S. Mandal P. Mayet C. Mazzocchi J.A. Pinston Zs. Podolyàk H. Schaffner Ch. Schlegel K. Schmidt K. Sümmerer H.J. Wollersheim 《The European Physical Journal A - Hadrons and Nuclei》2001,11(1):9-13
Rapidity correlations in 800 GeV proton interactions with emulsion nuclei are investigated for different targets and multiplicity
regions. To study the energy dependence, the results have been compared with proton interactions at 200 GeV and 400 GeV. A
common feature of all the interactions is the existence of strong, short-range correlations. However, no dependence of cluster
parameters on primary energy or target mass is found. A marginal increase of correlation strength with multiplicity is observed.
Received: 30 March 2001 / Accepted: 18 September 2001 相似文献
97.
Liam McElroy Mark Nieuwenhuyzen Graham C. Saunders 《Acta Crystallographica. Section C, Structural Chemistry》2001,57(6):678-679
The title molecule, [Mo{P(C6H5)2(C6H4F)}(HNC5H10)(CO)4] or [Mo(C18H14FP)(C5H11N)(CO)4], has irregular octahedral geometry about the Mo atom. The molecules form a complicated hydrogen‐bonded network comprising C—H?O, C—H?F and C—H?π hydrogen bonds and π–π interactions. The C—H?π and π–π interactions form chains containing C—H?π/π–π dimers linked via C—H?π interactions and the chains are linked into a three‐dimensional network via C—H?O and C—H?F hydrogen bonds. 相似文献
98.
99.
R. Wadsworth P. Regan S. M. Mullins G. J. Gyapong D. L. Watson P. J. Nolan M. J. Godfrey I. Jenkins Y. J. He B. J. Varley J. Simpso W. Gelletly 《Zeitschrift für Physik A Hadrons and Nuclei》1989,333(4):411-412
The states in the yrast band of132 Sm have been identified for the first time up to Jπ=16+. The yrast band of130Nd has also been extended from Jπ=16+ to 24+. The energy of the first 2+ state in132Sm indicates that the quadrupole deformation ε2 ~ 0.3 and is still increasing as the neutron number N decreases across the samarium isotopes. The results for130Nd allow the (h2/11)2 proton crossing frequency to be determined as ω=0.325 ± 0.005 MeV/?. This result is compared with cranked shell model predictions. 相似文献
100.