全文获取类型
收费全文 | 64719篇 |
免费 | 6337篇 |
国内免费 | 5779篇 |
专业分类
化学 | 30074篇 |
晶体学 | 704篇 |
力学 | 6276篇 |
综合类 | 671篇 |
数学 | 12073篇 |
物理学 | 27037篇 |
出版年
2024年 | 110篇 |
2023年 | 657篇 |
2022年 | 1608篇 |
2021年 | 1538篇 |
2020年 | 1797篇 |
2019年 | 1705篇 |
2018年 | 1532篇 |
2017年 | 1771篇 |
2016年 | 2106篇 |
2015年 | 1729篇 |
2014年 | 2584篇 |
2013年 | 4626篇 |
2012年 | 3016篇 |
2011年 | 3170篇 |
2010年 | 2591篇 |
2009年 | 3722篇 |
2008年 | 3998篇 |
2007年 | 4444篇 |
2006年 | 3779篇 |
2005年 | 3051篇 |
2004年 | 2646篇 |
2003年 | 2841篇 |
2002年 | 3104篇 |
2001年 | 2447篇 |
2000年 | 2334篇 |
1999年 | 1960篇 |
1998年 | 1901篇 |
1997年 | 1170篇 |
1996年 | 1112篇 |
1995年 | 969篇 |
1994年 | 1002篇 |
1993年 | 734篇 |
1992年 | 787篇 |
1991年 | 534篇 |
1990年 | 495篇 |
1989年 | 397篇 |
1988年 | 351篇 |
1987年 | 318篇 |
1986年 | 291篇 |
1985年 | 258篇 |
1984年 | 258篇 |
1983年 | 148篇 |
1982年 | 221篇 |
1981年 | 189篇 |
1980年 | 133篇 |
1979年 | 162篇 |
1978年 | 135篇 |
1977年 | 122篇 |
1976年 | 76篇 |
1973年 | 62篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Nikolai G. Khlebtsov Lev A. Dykman 《Journal of Quantitative Spectroscopy & Radiative Transfer》2010,111(1):1-2047
Nanoparticle plasmonics is a rapidly emerging research field that deals with the fabrication and optical characterization of noble metal nanoparticles of various size, shape, structure, and tunable plasmon resonances over VIS-NIR spectral band. The recent simultaneous advances in synthesis, characterization, electromagnetic simulation, and surface functionalization of plasmonic nanoparticles by biospecific molecular probes have led to a perfect publication storm in discoveries and potential biomedical applications of plasmon-resonant nanoparticle bioconjugates. Here, we present an overview of these topics. First, we discus basic wet-chemical routes to fabricate conjugates of gold, silver, or composite particles with controllable size, shape, structure and with surface functionalization by biospecific molecules. Second, we consider the single-particle dipole and multipole optics and coupled plasmonic nanoparticle arrays. Finally, we discus application of plasmonic bioconjugates to such fields as homogeneous and solid-phase assays, biomedical sensing and imaging, biodistribution and toxicity aspects, drug delivery and plasmonic photothermal therapy. 相似文献
992.
Sergey V. Ivanov Oleg G. Buzykin 《Journal of Quantitative Spectroscopy & Radiative Transfer》2010,111(15):2341-2353
Accuracies of classical, semiclassical and quantum methods are comprehensively examined in calculations of impact line widths of C2H2 molecules perturbed by Ar and He. The field of comparative study covers both infrared absorption and Raman scattering lines of acetylene having rotational quantum number J=0-30 at temperatures 173 and 296 K. Calculations have been made by fully classical method and by three basic least approximate semiclassical methods, namely, Neilsen-Gordon (NG) method, peaking approximation (PA) and Smith-Giraud-Cooper (SGC) method. Most accurate ab initio potential energy surfaces (PES) of Yang et al. (1996) [21] and Mozsynski et al. (1995) [22] have been applied to model C2H2-Ar and C2H2-He interactions. The comparison has been made also with available experimental data and with the results of rigorous fully quantum-mechanical calculations within close coupling and coupled states approaches in identical conditions. Semiclassical methods are proved to be not so much accurate as it is generally believed since all they gave in the cases considered seriously underestimated results. The fundamental issue of the adequacy of simplified trajectories in collision broadening calculations is finally reasonably solved. In cases of C2H2-Ar and C2H2-He systems the use of the “exact” isotropic trajectories (i.e. driven only by the isotropic part of PES) is the main reason of failing of NG, PA and SGC methods. Thus the neglecting of back-influence of the RT exchange on the classical path is a principal defect of semiclassical methods. Finally, the application of simplified trajectories is recognized as inadequate and risky in broadening calculations for molecules having relatively small rotational constants when accurate ab initio PES are applied. 相似文献
993.
A direct and unifying scheme for disclosure of periodic wave solutions of both nonlinear differential and difference equations is presented. The scheme is based on Hirota's bilinear form and certain Riemann theta function formulae. The relations between the periodic wave solutions and soliton solutions are rigorously established. 相似文献
994.
D. Laux H. Blasco J.Y. Ferrandis G. Hugon G. Despaux A. Leydier D. Mornet 《Ultrasonics》2010,50(8):741-743
Duchenne muscular dystrophy (DMD) is caused by the absence of dystrophin, the protein that plays a key mechanical role in maintaining muscle membrane integrity. One of the major consequences of dystrophin deficiency is the degeneration of muscle fibres, with a progressive loss in muscle strength. The objective of this research was to find an ultrasonic parameter sensitive to DMD, which could give relevant information related to microstructure if compared to traditional investigations such as morphometrical analysis. This “in vitro” study focused on the Mdx mouse model and investigated the potential differences between wild-type and dystrophin-deficient mice diaphragms. Using a 50 MHz ultrasonic sensor built in our group, we recorded an increase in ultrasonic wave attenuation in the dystrophin-deficient samples in comparison with normal muscles. A correlation between attenuation, mouse age and the percentage of non-muscular proportion in muscle was observed. As Mdx mouse is the best animal model for DMD and reproduces the degenerative pattern observed in human DMD muscles, this approach could be a powerful tool for in vitro DMD investigation and, more generally, for the characterisation of muscle properties. 相似文献
995.
基于微波奇偶模理论、叠加原理和阻抗匹配理论分析设计了3-dB功率分配器的结构参数,使用高频电磁场仿真软件HFSS进行结构仿真和参数优化,得到了最优结果:输入端口1的反射损耗RL=-41.42dB;1和4端口的隔离度Iso=-44.86dB;输出端口2、3的功分度为-3.02 dB和-3.01 dB;输入驻波比VSWR=1.017。 相似文献
996.
We report a novel post‐growth microwave treatment approach to selectively modify the surface morphologies of gold (Au) films coated on the polystyrene (PS) bead substrates for effectively improving the surface‐enhanced Raman scattering (SERS) effect on the analytes. The discrete dipole approximation (DDA) model was introduced to evaluate the enhancement effects by calculating the localized electromagnetic field distribution and extinction efficiency based on the sizes of the trenches and voids, and the surface roughness of the modified Au–PS bead substrates. The SERS performance of microwave‐modified Au–PS substrates on rhodamine 6G (Rh 6G) and saliva yields at least 10‐fold improvements in SERS intensities compared to the as‐grown substrates, which is also in agreement with theoretical predictions by DDA modeling. This work demonstrates both experimentally and theoretically the efficacy of the microwave heating treatment on modifying the Au–PS bead substrates for the realization of high SERS performance in biomedical applications. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
997.
Xiaoqi Fu Fengli Bei Xin Wang Xujie Yang Lude Lu 《Journal of Raman spectroscopy : JRS》2010,41(4):370-373
Graphite oxide (GO) was successfully silylated by 3‐mercaptopropyltrimethoxysilane. The surface‐enhanced Raman scattering spectrum of the silylated GO sheets sandwiched between colloidal silver nanoparticles and silver piece is presented. The Raman signal shows a 104 enhancement compared to that of bulk GO. The large Raman enhancement is most likely a result of electromagnetic (EM) coupling between the colloidal silver nanoparticles (localized surface plasmon) and the silver piece (surface plasmon polariton), creating large localized EM fields at their interface, where the silylated GO sheets reside in this sandwich architecture. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
998.
D. O. Soares-Pinto I. S. Oliveira M. S. Reis 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,62(3):337-340
In this work we report Monte Carlo simulations of a 2D
Ising model, in which the statistics of the Metropolis algorithm
is replaced by the nonextensive one. We compute the magnetization
and show that phase transitions are present for q ≠ 1. A
q - phase diagram (critical temperature vs. the entropic
parameter q) is built and exhibits some interesting features,
such as phases which are governed by the value of the entropic
index q. It is shown that such phases favors some energy levels
of magnetization states. It is also shown that the contribution
of the Tsallis cutoff is capital to the existence of phase
transitions. 相似文献
999.
1000.
K. Morawetz C. Olbrich S. Gemming 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,62(3):311-317
The coverage of vicinal, stepped surfaces with molecules is simulated with
the help of a two-dimensional Ising model including local distortions and
an Ehrlich-Schwoebel barrier term at the steps. An effective two-spin model is capable
to describe the main properties of this distorted Ising model. It is employed
to analyze the behavior of the system close to the critical points.
Within a well-defined regime of bonding strengths and Ehrlich-Schwoebel barriers we
find a reduction of coverage (magnetization) at low temperatures due to the
presence of the surface step. This results in a second, low-temperature
transition besides the standard Ising order-disorder transition.
The additional transition is characterized by a divergence of the
susceptibility as a finite-size effect. Due to the
surface step the mean-field specific heat diverges with a power law. 相似文献