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971.
采用自洽场离子球模型,研究类氢氖基态1s的电离势随等离子体电子温度及电子密度的变化规律,计算得到基态电离势的百分偏移量随等离子体电子密度的变化关系,拟合结果表明两者的对数值满足很好的线性关系.该结果对计算等离子体电离态分布及光谱模拟具有一定意义. 相似文献
972.
This work aims to obtain a wide area differential method for geostationary orbit (GEO) constellation. A comparison between
the dilution of precision (DOP) of four-dimensional (4D) calculation including satellite clock errors and ephemeris errors
and that of three-dimensional (3D) calculation only including ephemeris errors with the inverse positioning theory of GPS
shows the conclusion that all the 3D PDOPs are greatly reduced. Based on this, a basic idea of correcting satellite clock
errors and ephemeris errors apart is put forward, and moreover, a specific method of separation is proposed. Satellite clock
errors are separated in a master station with time synchronization, and all the remaining pseudo-range errors after the satellite
clock errors have been deducted are used to work out ephemeris corrections of all GEO satellites. By a comparative analysis
of user positioning accuracy before and after differential, the wide area differential method is verified to be quite valid
for GEO constellation.
Supported by the National Natural Science Foundation of China (Grant No. 10778715), the National Key Basic Research Development
Program of China (Grant No. 2007CB815502), and the Scientific Research Fund of Hunan Provincial Education Department (Grant
No. 08B039) 相似文献
973.
Tian-chu Li Ping-wei Lin Ming-shou Li Ping Wang Wei-liang Chen Nian-feng Liu Yi-ge Lin 《Frontiers of Physics in China》2009,4(2):155-159
The second laser cooling cesium fountain clock NIM5 at the National Institute of Metrology (NIM) China adopts the (1,1,1)
direct optical molasses ( OM) configuration. NIM5 has been running with a stability of 3×10−15/d and an operation ratio of 99% since 2007. Preliminary evaluations of NIM5 in 2008 showed a typical combined uncertainty
of 3×10−15. The NIM5 clock is operating in parallel with NIM’s first fountain clock NIM4. NIM4 and NIM5 are used to steer the frequency
of the calculated NIM atomic time TA-c(NIM) and the first set of results are promising. We are now at the stage of comparing
the frequency of NIM5 with UTC to support the independent frequency shift evaluations of NIM5 and contribute to the international
atomic time in the near future.
相似文献
974.
In circadian rhythm generation,intercellular signaling factors are shown to play a crucial role in both sustaining intrinsic cellular rhythmicity and acquiring collective behaviours across a population of circadian neurons.However,the physical mechanism behind their role remains to be fully understood.In this paper,we propose an indirectly coupled multicellular model for the synchronization of Drosophila circadian oscillators combining both intracellular and intercellular dynamics.By simulating different experimental conditions,we find that such an indirect coupling way can synchronize both heterogeneous self-sustained circadian neurons and heterogeneous mutational damped circadian neurons.Moreover,they can also be entrained to ambient light-dark(LD) cycles depending on intercellular signaling. 相似文献
975.
Characterization of a velocity-tunable 87Rb cold atomic source with a high-speed imaging technology 下载免费PDF全文
This paper has developed and characterized a method to produce a velocity-tunable 87 Rb cold atomic source for atomic interferometry application.Using a high speed fluorescence imaging technology,it reports that the dynamic process of the atomic source formation is observed and the source performances including the flux and the initial velocity are characterized.A tunable atomic source with the initial velocity of 1.4~2.6 m/s and the atomic source flux of 2 × 10 8 ~ 6 × 10 9 atoms/s has been obtained with the built experimental setup. 相似文献
976.
The electronic structures and magnetic properties of SmCo7 xMx (M=Ti, Si, Zr, Hf, Cu, B, Ag, Ga, Mn) compounds are investigated by using a spin-polarized MS-X.α method. The results show that the long-range ferromagnetic order is determined by a stronger 3d-5d interaction, rather than the traditional RKKY interaction, and the effects of doping element M on 3d-5d coupling are negligible in Sm-Co-based compounds. The nonmagnetic dopant Si atoms have a larger effect on the moments of 2e site although they preferably occupy the Co 3g sites, which results in the stronger uniaxial anisotropy of this compound. Analysis of the formation energies indicates that 5d-element doped compounds are more stable than other dopants, and furthermore, they have a higher Curie temperature above room temperature, which will be in favor of their potential application as high-temperature permanent magnets. 相似文献
977.
A flow injection system was developed for on-line sorbent extraction preconcentration and flame atomic absorption spectrometric
determination of cadmium in natural water samples. The non-charged cadmium complex with diethyl-dithiophosphate (DDPA) was
formed on-line in 0.1 mol L−1 HNO3 and retained on the hydrophobic poly-chlorotrifluoroethylene (PCTFE) sorbent material. The adsorbed complex was eluted with
isobutyl methylketone (IBMK) and injected directly into the nebulizer via a flow compensation unit. All major chemical and
flow parameters affecting the complex formation adsorption and elution as well as interference were studied and optimized.
By processing 2.4 mL of sample, the enhancement factor was 39 and the sampling frequency was 50 h−1. For 30 s preconcentration time the detection limit was 0.3 μg L−1 and the relative standard deviation at 5.0 μg L−1 Cd concentration level was 2.9%. The calibration curve was linear in the range 0.8–40.0 μg L−1. The accuracy of the method was estimated by analyzing a certified reference material NIST-CRM 1643d (Trace elements in water).
Good recoveries were obtained for spiked natural-water and waste-water samples.
Correspondence: Aristidis N. Anthemidis, Laboratory of Analytical Chemistry, Department of Chemistry, Aristotle University,
GR-Thessaloniki 54124, Greece 相似文献
978.
本文提出一种利用磁光阱冷却捕获技术制备低速、连续、单色性好原子束的方法及技术.采用3维磁光阱从背景Rb蒸汽中捕获Rb87原子进行冷却、捕获形成原子云团,利用在纵向方向上结构设计的小孔将冷原子云团推出形成冷原子束,并在原子束行进方向上采用2维光学黏胶对原子束进行准直,采用态制备激光对其进行态制备,全部制备到Rb87原子的基态能级|F=1>上,从而为原子惯性技术(原子干涉仪、原子重力仪、原子加速度计)、原子频标(原子钟)提供低速、连续、单色性好的原子束.文章对于制备技术的实验系统及实验结果进行了详细的阐述. 相似文献
979.
J. Mitroy J. Y. Zhang M. W. J. Bromley K. G. Rollin 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2009,53(1):15-19
The blackbody radiation shift of the Al+ 3s2
1Se
0 ↦ 3s3p 3P○
0 clock transition is evaluated. The polarizabilities of the two states are determined by means of configuration interaction
calculations in conjunction with oscillator strength sum rules. The ground state polarizability was 24.14 ±0.12 a.u. while
the metastable state polarizability was 24.62 ±0.25 a.u. The derived frequency shift at 300 K was Δν= -0.0042 ±0.0032 Hz.
Some auxiliary sum rules are evaluated that allow for the conversion of a finite frequency polarizability difference to a
static polarizability difference. 相似文献
980.
Q. Xu X. M. Hu J. W. Yin 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2009,51(2):267-273
The atomic coherence in a three-level Λ atom is studied, in which each optical transition is driven by a coherent field and
the metastable states are coupled to each other via a microwave field. It’s shown that the atomic coherence crucially depends
on the relative phase delay between the envelopes of the amplitudes of the three coupling fields. In particular, when the
phase delay is adjusted to 0 or π, the maximal atomic coherence arises, while the maximal atomic coherence doesn’t occur once
the phase delay is changed to π/2. The maximal atomic coherence is attributed to the trapping of the population in the lower
sublevels. 相似文献