全文获取类型
收费全文 | 1435篇 |
免费 | 51篇 |
国内免费 | 5篇 |
专业分类
化学 | 940篇 |
晶体学 | 16篇 |
力学 | 36篇 |
数学 | 182篇 |
物理学 | 317篇 |
出版年
2023年 | 35篇 |
2022年 | 31篇 |
2021年 | 49篇 |
2020年 | 45篇 |
2019年 | 45篇 |
2018年 | 42篇 |
2017年 | 20篇 |
2016年 | 44篇 |
2015年 | 46篇 |
2014年 | 42篇 |
2013年 | 76篇 |
2012年 | 74篇 |
2011年 | 119篇 |
2010年 | 44篇 |
2009年 | 53篇 |
2008年 | 76篇 |
2007年 | 69篇 |
2006年 | 57篇 |
2005年 | 50篇 |
2004年 | 55篇 |
2003年 | 27篇 |
2002年 | 29篇 |
2001年 | 18篇 |
2000年 | 20篇 |
1999年 | 9篇 |
1998年 | 13篇 |
1997年 | 16篇 |
1996年 | 13篇 |
1995年 | 9篇 |
1994年 | 10篇 |
1993年 | 21篇 |
1992年 | 7篇 |
1991年 | 13篇 |
1990年 | 10篇 |
1989年 | 5篇 |
1988年 | 11篇 |
1987年 | 12篇 |
1986年 | 8篇 |
1985年 | 10篇 |
1984年 | 14篇 |
1983年 | 14篇 |
1982年 | 9篇 |
1981年 | 9篇 |
1980年 | 8篇 |
1979年 | 9篇 |
1978年 | 11篇 |
1977年 | 8篇 |
1976年 | 9篇 |
1974年 | 5篇 |
1973年 | 6篇 |
排序方式: 共有1491条查询结果,搜索用时 46 毫秒
91.
Sheridan B Martin DS Power JR Barrett SD Smith CI Lucas CA Nichols RJ Weightman P 《Physical review letters》2000,85(21):4618-4621
Introducing reflection anisotropy spectroscopy (RAS) as a new probe for solid-liquid interfaces, we present results for the Au(110)/electrolyte interface which serves as a model system. We demonstrate that RAS is sensitive to surface phase transitions, step morphology, and electronic surface states. Using an empirical approach, the RA spectra are reproduced and features are identified which reflect the known character of the bias voltage driven (2x1) to (1x1) phase transition. RAS is established as an experimental technique to probe the electronic structure of solid-liquid interfaces in real time to study a wide range of interface properties. 相似文献
92.
Ji-Won Moon Lucas W. Yeary Adam J. Rondinone Claudia J. Rawn Melanie J. Kirkham Yul Roh Lonnie J. Love Tommy J. Phelps 《Journal of magnetism and magnetic materials》2007
The magnetic susceptibility (κRT) and saturation magnetization (MS) of microbially synthesized magnetites were systematically examined. Transition metal (Cr, Mn, Co, Ni and Zn)- and lanthanide (Nd, Gd, Tb, Ho and Er)-substituted magnetites were microbially synthesized by the incubation of transition metal (TM)- and lanthanide (L)-mixed magnetite precursors with either thermophilic (TOR-39) or psychrotolerant (PV-4) metal-reducing bacteria (MRB). Zinc incorporated congruently into both the precursor and substituted magnetite, while Ni and Er predominantly did not. Microbially synthesized Mn- and Zn-substituted magnetites had higher κRT than pure biomagnetite depending on bacterial species and they exhibited a maximum κRT at 0.2 cationic mole fraction (CMF). Other TMs’ substitution linearly decreased the κRT with increasing substitution amount. Based on the MS values of TM- and L-substituted magnetite at 0.1 and 0.02 CMF, respectively, Zn (90.7 emu/g for TOR-39 and 93.2 emu/g for PV-4)- and Mn (88.3 emu/g by PV-4)-substituted magnetite exhibited higher MS than standard chemical magnetite (84.7 emu/g) or pure biomagnetite without metal substitution (76.6 emu/g for TOR-39 and 80.3 emu/g for PV-4). Lanthanides tended to decrease MS, with Gd- and Ho-substituted magnetites having the highest magnetization. The higher magnetization of microbially synthesized TM-substituted magnetites by the psychrotroph, PV-4 may be explained by the magnetite formation taking place at low temperatures slowing mechanics, which may alter the magnetic properties compared to the thermophile, through suppression of the random distribution of substituted cations. 相似文献
93.
The manganite La0.67Sr0.33MnO3 (LSMO) layers are deposited on single crystal MgO(0 0 1) substrates using a magnetron dc sputtering. The crystalline perfection of the layers, both the as-prepared and the annealed, are characterized by X-ray diffraction technique, rocking curve measurements, Rutherford backscattering spectroscopy (RBS) and transmission electron microscopy (TEM). TEM analyses give evidence of the epitaxial growth of the annealed LSMO with a nanocrystalline surface layer. The temperature dependence of resistance in the 77-340 K range is measured by a standard four-probe technique. While the as-prepared film does not show any transition from paramagnetic to ferromagnetic state, the film annealed in oxygen shows steep R(T) dependence with a peak at 330 K and maximal slope (dR/dT) at 290 K where the maximal sensitivity is 3% K−1. 相似文献
94.
95.
J.E. Bailey G.A. Chandler G.A. Rochau Y. Maron S.A. Slutz G.S. Dunham I. Golovkin P.W. Lake R.W. Lemke J.M. Lucas J.J. MacFarlane T.A. Mehlhorn T.C. Moore D.G. Schroen E. Stambulchik K. Youngblood 《High Energy Density Physics》2005,1(1):21-30
A dynamic hohlraum is created when an annular z-pinch plasma implodes onto a cylindrical 0.014 g/cc 6-mm-diameter CH2 foam. The impact launches a radiating shock that propagates toward the axis at 350 μm/ns. The radiation trapped by the tungsten z-pinch plasma forms a 200 eV hohlraum that provides X-rays for indirect drive inertial confinement fusion capsule implosion experiments. We are developing the ability to diagnose the hohlraum interior using emission and absorption spectroscopy of Si atoms added as a tracer to the central portion of the foam. Time- and space-resolved Si spectra are recorded with an elliptical crystal spectrometer viewing the cylindrical hohlraum end-on. A rectangular aperture at the end of the hohlraum restricts the field of view so that the 1D spectrometer resolution corresponds approximately to the hohlraum radial direction. This enables distinguishing between spectra from the unshocked radiation-heated foam and from the shocked foam. Typical spectral lines observed include the Si Lyα with its He-like satellites and the He-like resonance sequence including Heα, Heβ, and Heγ, along with some of their associated Li-like satellites. Work is in progress to infer the hohlraum conditions using collisional–radiative modeling that accounts for the radiation environment and includes both opacity effects and detailed Stark broadening calculations. These 6-mm-scale radiation-heated plasmas might eventually also prove suitable for testing Stark broadening line profile calculations or for opacity measurements. 相似文献
96.
In this paper, a new fouling measurement method is presented as a pragmatic approach to determine a mixed liquor's fouling propensity. The MBR-VFM (VITO Fouling Measurement) uses a specific measurement protocol consisting of alternating filtration and physical cleaning steps, which enables the calculation of both the reversible and the irreversible fouling resistances. The MBR-VFM principle, set-up and measurement protocol are described as well as the evaluation of the fouling measurement method. Finally, the MBR-VFM was validated by comparing the fouling propensity measured on-line by the MBR-VFM in a lab-scale MBR with the fouling of the MBR membranes themselves. Our experiments indicated that the MBR-VFM can accurately measure fouling and that it can even be detected earlier than can be seen from the on-line filtration data of the lab-scale system itself. Furthermore, the differences measured in reversible and irreversible fouling seemed to be related to the observed impact of physical and chemical cleaning respectively. Therefore, the application of the MBR-VFM as an on-line sensor in an advanced control system, enabling the deployment of the measured fouling data for the control of membrane cleaning, seems feasible and will be tested in the near future. 相似文献
97.
The goal of this paper is to prove some general vector-valued perturbed equilibrium principles and some existence results of vector equilibrium points for bifunctions satisfying a new natural notion of lower semi-continuity. We obtain these results by going through a new concept of approximative equilibrium point. 相似文献
98.
M. Dolores Petit Dominguez M. Teresa Sevilla Escribano Jose M. Pinilla Macias Lucas Hernandez Hernandez 《Microchemical Journal》1990,42(3)
A sensitive method for the determination of microamounts of cobalt by ion-exchanger spectrophotometry has been developed. The chromogenic agent, Nitroso-R-Salt (NRS), was loaded on an anionic-exchange resin (Amberlite CG-400). The absorbance of the NRS-cobalt complex on the chelating resin was measured at 508 nm. The best conditions for the preconcentration of cobalt on the resin before the spectrophotometric determination were a pH value of 6, temperature of 80 °C, and heating times of 45 or 90 min for 50 and 400 ml of sample, respectively. The detection limits were 27 ng/ml (50-ml samples) and 1.8 ng/ml (400-ml samples). Interference by other metals was investigated. The method is useful for determination of cobalt in natural waters. 相似文献
99.
100.
Lucas Montero De Espinosa Juan C. Ronda Marina Galià Virginia Cádiz Michael A.R. Meier 《Journal of polymer science. Part A, Polymer chemistry》2009,47(21):5760-5771
The acyclic diene metathesis (ADMET) polymerization of a phosphorus‐containing α,ω‐diene prepared from a plant oil derived building block is reported. Different ruthenium based metathesis catalysts and conditions were tested to optimize the ADMET polymerization of this monomer. Undecylenyl undecenoate was used as fully renewable comonomer to obtain polyesters with different phosphorus contents and to increase the renewable content of the final polymers. Copolymerization caused marked variations in the molecular weights leading to polyesters from 6 to 38 KDa. The effect of the ADMET polymerization temperature in the thermal properties of the copolymers was studied and their thermal degradation and flame retardant properties were evaluated. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5760–5771, 2009 相似文献