首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   128篇
  免费   0篇
  国内免费   9篇
化学   19篇
力学   5篇
数学   23篇
物理学   90篇
  2021年   3篇
  2020年   1篇
  2019年   1篇
  2017年   2篇
  2016年   9篇
  2015年   1篇
  2014年   38篇
  2013年   24篇
  2012年   18篇
  2011年   13篇
  2010年   1篇
  2009年   4篇
  2008年   2篇
  2006年   3篇
  2005年   1篇
  2002年   2篇
  2000年   1篇
  1998年   1篇
  1997年   1篇
  1991年   1篇
  1989年   1篇
  1987年   1篇
  1985年   1篇
  1983年   1篇
  1981年   1篇
  1979年   1篇
  1974年   1篇
  1963年   2篇
  1960年   1篇
排序方式: 共有137条查询结果,搜索用时 421 毫秒
71.
Accelerator-driven systems (ADS) have evoked lot of interest the world over because of their capability to incinerate the MA (minor actinides) and LLFP (long-lived fission products) radiotoxic waste and their ability to utilize thorium as an alternative nuclear fuel. One of the main subsystems of ADS is a high energy (∼1 GeV) and high current (∼30 mA) CW proton Linac. The accelerator for ADS should have high efficiency and reliability and very low beam losses to allow hands-on maintenance. With these criteria, the beam dynamics simulations for a 1 GeV, 30 mA proton Linac has been done. The Linac consists of normal-conducting radio-frequency quadrupole (RFQ), drift tube linac (DTL) and coupled cavity drift tube Linac (CCDTL) structures that accelerate the beam to about 100 MeV followed by superconducting (SC) elliptical cavities, which accelerate the beam from 100 MeV to 1 GeV. The details of the design are presented in this paper.  相似文献   
72.
73.
The synthesis and characterization of nanosized zinc oxide and its nanofluid in a polyvinyl alcohol (PVA) matrix have been done in the present investigation. Crystalline zinc oxide nanoparticles are synthesized using single-step chemical method while the nanofluids are prepared by the dispersion of nanoparticles in PVA solution using an ultrasonicator. The prepared nanoparticles are characterized using X-ray diffraction, SEM?CEDX and UV?Cvisible spectrum. The particle size distribution measurement is carried out by acoustic particle sizer. The ultrasonic velocities are measured in the synthesized nanofluid under different physical conditions using an ultrasonic interferometer. It is found that the degree of crystallinity of nanoparticles depends on the evaporation rate during its synthesis and ultrasonic velocity has non-linear relation with temperature for the present nanofluid.  相似文献   
74.
Spectral analysis of K-shell X-ray emission of magnesium plasma, produced by laser pulses of 45 fs duration, focussed up to an intensity of ~1018 W cm?2, is carried out. The plasma conditions prevalent during the emission of X-ray spectrum were identified by comparing the experimental spectra with the synthetic spectra generated using the spectroscopic code PrismSPECT. It is observed that He-like resonance line emission occurs from the plasma region having sub-critical density, whereas K-α emission arises from the bulk solid heated to a temperature of 10 eV by the impact of hot electrons. K-α line from Be-like ions was used to estimate the hot electron temperature. A power law fit to the electron temperature showed a scaling of I 0.47 with laser intensity.  相似文献   
75.
S P RAM  S K TIWARI  S R MISHRA  H S RAWAT 《Pramana》2014,82(2):419-423
We present here our experimental results on transfer of laser-cooled atom cloud to a quadrupole magnetic trap. We show that by choosing appropriately the ratio of potential energy in magnetic trap to kinetic energy of cloud in molasses, we can obtain the maximum phase-space density in the magnetic trap. These results guide us to choose the value of current to be switched in the quadrupole coils used for magnetic trapping for a given temperature of the cloud after molasses. This study is also useful to set the initial phase-space density of the cloud before evaporative cooling.  相似文献   
76.
The TeV atmospheric Cherenkov telescope with imaging camera (TACTIC) γ-ray telescope has been in operation at Mt. Abu, India since 2001 to study TeV γ-ray emission from celestial sources. During the last 10 years, apart from consistently detecting a steady signal from the Crab Nebula above ~1.2 TeV energy, at a sensitivity level of ~5.0 σ in ~25 h, the telescope has also detected flaring activity from Mrk 421 and Mrk 501 on several occasions. Although we used Crab Nebula data partially, in some of the reported results, primarily for testing the validity of the full data analysis chain, the main aim of this work is to study the long term performance of the TACTIC telescope by using consolidated data collected between 2003 and 2010. The total on-source data, comprising ~402 h, yields an excess of ~(3742±192) γ-ray events with a statistical significance of ~19.9 σ. The off-source data, comprising ~107 h of observation, is found to be consistent with a no-emission hypothesis, as expected. The resulting γ-ray rate for the on-source data is determined to be ~(9.31±0.48) h ?1. A power law fit (dΦ/dE=f 0 E ?Γ ) with f 0 ~ (2.66±0.29) × 10?11 cm?2 s?1 TeV?1 and Γ ~ 2.56±0.10 is found to provide reasonable fit to the inferred differential spectrum within statistical uncertainties. The spectrum matches reasonably well with that obtained by other groups. A brief summary of the improvements in the various subsystems of the telescope carried out recently, which has resulted in a substantial improvement in its detection sensitivity (viz., ~5 σ in an observation period of ~13 h as compared to ~25 h earlier) are also presented in this paper. Encouraged by the detection of strong γ-ray signals from Mrk 501 and Mrk 421 on several occasions, there is considerable scope for the TACTIC telescope to monitor similar TeV γ-ray emission activity from other active galactic nuclei on a long-term basis.  相似文献   
77.
This paper presents the experimental studies on self-breakdown-based single-gap plasma cathode electron (PCE) gun (5–20 kV/50–160 A) in argon, gas atmosphere and its performance evaluation based on particle-in-cell (PIC) simulation code ‘OOPIC-Pro’. The PCE-Gun works in conducting phase (low energy, high current) of pseudospark discharge. It produces intense electron beam, which can propagate more than 200 mm in the drift space region without external magnetic field. The profile of this beam in the drift space region at different breakdown conditions (i.e., gas pressures and applied voltages) has been studied and the experimental results are compared with simulated values. It is demonstrated that ~30% beam current is lost during the propagation possibly due to space charge neutralization and collisions with neutral particles and walls.  相似文献   
78.
The success of carbon capture and storage (CCS) programme relies on the long-term isolation of CO2 from the atmosphere. Therefore, technologies concomitant to physical storage of CO2 such as reliable measurement, monitoring, and verification (MMV) techniques are needed to ensure that the integrity of the storage site is maintained. We propose the use of laser-induced breakdown spectroscopy (LIBS) analytical technique to detect carbon dioxide leaks to aid in the successful application of CCS. LIBS has a real-time monitoring capability and can be reliably used for the elemental and isotopic analysis of solid, liquid, and gas samples. The flexibility of probe design and use of fibre optics make it a suitable technique for real time measurements in harsh conditions and at hard-to-reach places. Proposed monitoring with LIBS includes terrestrial soil samples, water samples from monitoring wells or from different formations, air samples from monitoring wells or suspected leakage areas. This work details the laboratory scale experiments to measure carbon contents in rock, soil, aqueous, and air samples. The potential of the technology for measurements in high pressure high-temperature conditions will also be discussed.  相似文献   
79.
M K SINGH  A K SOMA  V SINGH  R PATHAK 《Pramana》2014,83(3):377-386
This article focusses on the study of clan model parameters and their target dependence in light of void probability scaling for heavy (Ag and Br) and light (C, N and O) groups of targets present in nuclear emulsion detector using 84Kr36 at ~1 A GeV. The variation of scaled rapidity-gap (rap–gap) probability with single moment combination has been studied. We found that experimental points lie approximately on the negative binomial distribution (NBD) curve, indicating a scaling behaviour. The increase in average clan multiplicities ( \(\bar {N}\) ) for interactions with the pseudorapidity interval (Δη) was also observed. The values of \(\bar {N}\) for AgBr targets are larger than those for C/N/O target and also average number of particles per clan ( \(\bar {n}_{\mathrm {c}}\) ) increases with increase in pseudorapidity interval. We further observed that for a particular target, the average number of particles per clan ( \(\bar {n}_{\mathrm {c}}\) ) increases with an increase in the size of projectile nucleus.  相似文献   
80.
Surface plasmons at the metal–dielectric interface have emerged as an important candidate to propagate and localize light at subwavelength scales. By tailoring the geometry and arrangement of metallic nanoarchitectures, propagating and localized surface plasmons can be obtained. In this brief perspective, we discuss: (1) how surface plasmon polaritons (SPPs) and localized surface plasmons (LSPs) can be optically excited in metallic nanoarchitectures by employing a variety of optical microscopy methods; (2) how SPPs and LSPs in plasmonic nanowires can be utilized for subwavelength polarization optics and single-molecule surface-enhanced Raman scattering (SERS) on a photonic chip; and (3) how individual plasmonic nanowire can be optically manipulated using optical trapping methods.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号