全文获取类型
收费全文 | 15485篇 |
免费 | 1035篇 |
国内免费 | 888篇 |
专业分类
化学 | 11182篇 |
晶体学 | 145篇 |
力学 | 405篇 |
综合类 | 66篇 |
数学 | 2751篇 |
物理学 | 2859篇 |
出版年
2023年 | 164篇 |
2022年 | 339篇 |
2021年 | 433篇 |
2020年 | 451篇 |
2019年 | 393篇 |
2018年 | 357篇 |
2017年 | 342篇 |
2016年 | 660篇 |
2015年 | 612篇 |
2014年 | 713篇 |
2013年 | 1100篇 |
2012年 | 1223篇 |
2011年 | 1415篇 |
2010年 | 962篇 |
2009年 | 842篇 |
2008年 | 1075篇 |
2007年 | 1072篇 |
2006年 | 919篇 |
2005年 | 786篇 |
2004年 | 680篇 |
2003年 | 470篇 |
2002年 | 431篇 |
2001年 | 224篇 |
2000年 | 176篇 |
1999年 | 183篇 |
1998年 | 107篇 |
1997年 | 116篇 |
1996年 | 117篇 |
1995年 | 103篇 |
1994年 | 79篇 |
1993年 | 70篇 |
1992年 | 66篇 |
1991年 | 46篇 |
1990年 | 50篇 |
1989年 | 35篇 |
1988年 | 32篇 |
1987年 | 43篇 |
1986年 | 33篇 |
1985年 | 57篇 |
1984年 | 62篇 |
1983年 | 35篇 |
1982年 | 34篇 |
1981年 | 31篇 |
1980年 | 19篇 |
1979年 | 24篇 |
1978年 | 28篇 |
1977年 | 20篇 |
1975年 | 18篇 |
1974年 | 18篇 |
1973年 | 19篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
The global formulation of the higher-order Poincaré-Cartan form for Lagrangian field theories in the calculus of variations is re-examined in terms of the theory of lifts of tensor fields on a manifold to its higher-order prolongated jet bundles.Partially supported by CNPq, Brazil, Proc. MA 30.1115/79. 相似文献
102.
The algebraic structure of chiral anomalies is made globally valid on non-trivial bundles by the introduction of a fixed background connection. Some of the techniques used in the study of the anomaly are improved or generalized, including a systematic way of generating towers of descent equations.This work was supported in part by the Director, Office of Energy Research, Office of High Energy and Nuclear Physics, Division of High Energy Physics of the U.S. Department of Energy under contract DE-AC03-76SF00098 and in part by the National Science Foundation under research grant PHY81-18547 相似文献
103.
The dynamics of the femtosecond pulse propagation in a plasma channel is investigated by the pumpprobe longitudinal diffractometry and second harmonic generation frequency-resolved optical gating (SHGFROG) technique. The spatial characteristics, corresponding to the electronic density and the size of the channel, can be observed by the recorded ring pattern, and the spectral and temporal characteristics are recorded by the SHG-FROG traces. The spatiotemporal characteristics will help us to better understand the dynamics of the plasma induced by the femtosecond pulse and the femtosecond pulse propagating in the plasma channel. 相似文献
104.
Briselli E Garreffa G Bianchi L Bianciardi M Macaluso E Abbafati M Grazia Marciani M Maraviglia B 《Magnetic resonance imaging》2006,24(4):393-400
Interest about simultaneous electroencephalography (EEG) and functional magnetic resonance imaging (fMRI) data acquisition has rapidly increased during the last years because of the possibility that the combined method offers to join temporal and spatial resolution, providing in this way a powerful tool to investigate spontaneous and evoked brain activities. However, several intrinsic features of MRI scanning become sources of artifacts on EEG data. Noise sources of a highly predictable nature such as those related to the pulse MRI sequence and those determined by magnetic gradient switching during scanning do not represent a major problem and can be easily removed. On the contrary, the ballistocardiogram (BCG) artifact, a large signal visible on all EEG traces and related to cardiac activity inside the magnetic field, is determined by sources that are not fully stereotyped and causing important limitations in the use of artifact-removing strategies. Recently, it has been proposed to use independent component analysis (ICA) to remove BCG artifact from EEG signals. ICA is a statistical algorithm that allows blind separation of statistically independent sources when the only available information is represented by their linear combination. An important drawback with most ICA algorithms is that they exhibit a stochastic behavior: each run yields slightly different results such that the reliability of the estimated sources is difficult to assess. In this preliminary report, we present a method based on running the FastICA algorithm many times with slightly different initial conditions. Clustering structure in the signal space of the obtained components provides us with a new way to assess the reliability of the estimated sources. 相似文献
105.
随绿色可持续发展观念的深入人心,研究人员致力于寻找天然有机材料应用于功能性电子器件.淀粉以其低廉的价格、丰富的来源和优异的机械性能进入了科研人员的视野.淀粉可由玉米、马铃薯、甘薯和葛根等含淀粉的物质中提取而得,一般不溶于水,在和水加热至一定温度时,则糊化成胶状溶液.本文通过旋涂法将玉米淀粉的胶状溶液旋涂至氧化铟锡玻璃表面,然后在30?C恒温环境中晾干制备成固态胶合状薄膜.以此薄膜作为固态电解质制备了氧化铟锌突触晶体管,并实现了生物神经突触的双脉冲易化、学习记忆能力、高通滤波等可塑性行为的仿真.本研究以玉米淀粉固态胶合薄膜作为电解质大大降低了氧化物薄膜晶体管固态电解质的成本,且该电解质无毒性、来源丰富,将为人工神经网络的开发提供一种可选择的元件. 相似文献
106.
Vladimir Kalashnikov Sergey V. Sergeyev Juan Diego Ania‐Castanón Gunnar Jacobsen Sergei Popov 《Annalen der Physik》2017,529(1-2)
The interplay of such cornerstones of modern nonlinear fiber optics as a nonlinearity, stochasticity and polarization leads to variety of the noise induced instabilities including polarization attraction and escape phenomena harnessing of which is a key to unlocking the fiber optic systems specifications required in high resolution spectroscopy, metrology, biomedicine and telecommunications. Here, by using direct stochastic modeling, the mapping of interplay of the Raman scattering‐based nonlinearity, the random birefringence of a fiber, and the pump‐to‐signal intensity noise transfer has been done in terms of the fiber Raman amplifier parameters, namely polarization mode dispersion, the relative intensity noise of the pump laser, fiber length, and the signal power. The obtained results reveal conditions for emergence of the random birefringence‐induced resonance‐like enhancement of the gain fluctuations (stochastic anti‐resonance) accompanied by pulse broadening and rare events in the form of low power output signals having probability heavily deviated from the Gaussian distribution.
107.
Lifshitz Transitions Induced by Temperature and Surface Doping in Type‐II Weyl Semimetal Candidate Td‐WTe2 (Phys. Status Solidi RRL 12/2017) 下载免费PDF全文
108.
Manuel O. Cáceres 《The European Physical Journal B - Condensed Matter and Complex Systems》2017,90(4):74
The concept of continuous-time random walk is generalized into the quantum approach using a completely positive map. This approach introduces in a phenomenological way the concept of disorder in the transport problem of a quantum open system. If the waiting-time of the continuous-time renewal approach is exponential we recover a semigroup for a dissipative quantum walk. Two models of non-Markovian evolution have been solved considering different types of waiting-time functions. 相似文献
109.
San-jun ZHANG Lotfi BERGUIGA Nicolas HUGO Thibault ROLAND Francoise ARGOUL Juan ELEZGARAY Wen-xueLI He-ping ZENG 《Frontiers of Physics》2009,4(4):469
This article reviews our recent advances in surface plasmon resonance (SPR) based biochips. It includes four issues, which are the preparation and characterization of high quality gold film, the preparation and characterization of self-assembled monolayer (SAM), dynamics of DNA adsorption on SAMs, and SPRbased microscopies. Numerous topics related to SPR, such as, the modeling of SPR by transmission matrix, effective medium theory, applications of SPR in biology, and SPR-based novel microscopies, are discussed. A novel electrochemical technique, which is extremely useful for the preparation and characterization of high quality SAMs, is also discussed. 相似文献
110.
MAWei-Xing HUZhao-Hui ZHOULi-Juan ZHUJi-Zhen LUJuan 《理论物理通讯》2003,40(6):699-701
Based on Glauber Multiple Scattering Theory, high-energy proton elastic scattering on halo-like nucleus ^13C is studied in a single nucleon wave function with low angular momentum configurations. A great agreement with experimental data is obtained and the theoretical prediction clearly shows that 13U has a neutron halo-like structure.Then, the origin and nature of nuclear halo phenomena are explained in terms of nuclear short-range correlations. Our conclnsion shows ttiat the origin of nuclear halo-like phenomena originates from short range nuclear correlation. 相似文献