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41.
As in the first part of the present study (Sapar et al., 2002) we use the β-law for velocity of stellar wind and the Sobolev
approximation for radiative transfer. Here we have succeeded to derive general and relatively simple analytical formulae in
elementary functions for saturated P Cygni type line profiles if parameter 2β is arbitrary positive integer (in the first
part we studied the cases 2β ≤ 4). The four terms obtained describe contributions to the line profile due to isotropic and
anisotropic parts of optical thickness in the source function of the light-scattering layer followed by isotropic and anisotropic
parts of multiple scattering. The limits of acceptability of the Sobolev approximation for β-law have been discussed and specified.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
42.
S. Chatterjee 《Journal of Astrophysics and Astronomy》1991,12(4):269-280
We present here rigorous analytical solutions for the Boltzmann-Poisson equation concerning the distribution of stars above
the galactic plane. The number density of stars is considered to follow a behaviour n(m,0) ∼H(m - m0)m−x, wherem is the mass of a star andx an arbitrary exponent greater than 2 and also the velocity dispersion of the stars is assumed to behave as < v2(m)> ∼ m−θ the exponent θ being arbitrary and positive. It is shown that an analytic expression can be found for the gravitational field
Kz, in terms of confluent hypergeometric functions, the limiting trends being Kz∼z for z →0, while Kz
→ constant for z → infinity. We also study the behaviour of < |z(m)|2>,i.e. the dispersion of the distance from the galactic disc for the stars of massm. It is seen that the quantity < |z(m)|2>∼ mt-θ, for m→ t, while it departs significantly from this harmonic oscillator behaviour for stars of lighter masses. It is suggested
that observation of < |z(m)|2> can be used as a probe to findx and hence obtain information about the mass spectrum. 相似文献
43.
A. K. Pandey K. Upadhyay K. Ogura Ram Sagar V. Mohan H. Mito H. C. Bhatt B. C. Bhatt 《Monthly notices of the Royal Astronomical Society》2005,358(4):1290-1308
UBVRI CCD photometry in a wide field around two young open clusters, NGC 663 and 654, has been carried out. Hα and polarimetric observations for the cluster NGC 654 have also been obtained. We use the photometric data to construct colour–colour and colour–magnitude diagrams, from which we can investigate the reddening, age, mass and evolutionary states of the stellar contents of the these clusters. The reddening across the cluster regions is found to be variable. There is evidence for anomalous reddening law in both clusters; however, more infrared and polarimetric data are needed to conclude about the reddening law. Both clusters are situated at about a distance of 2.4 kpc. Star formation in both clusters is found to be a continuous process. In the case of NGC 663, star formation seems to have taken place sequentially, in the sense that formation of low-mass stars precedes the formation of most massive stars. Whereas, in the case of NGC 654, formation of low-mass stars did not cease after the formation of most massive stars in the cluster. 相似文献
44.
Nishant Mittal Joginder Sharma Vivek Tomar Udit Narain 《Planetary and Space Science》2009,57(1):53-57
We have analyzed the data for more than 12900 coronal mass ejections (CMEs) which were obtained by SOHO/LASCO during the period of 1996-2007. The online CME catalogue contains all major CMEs detected by LASCO C2 and C3 coronagraphs. Basically we determine the CME speeds from the linear and quadratic fits to the height-time measurements. It is found that linear (constant speed) fit is preferable for 90% of the CMEs. The distribution of speeds of CMEs in solar cycle 23 is presented along with those obtained by others. As expected, the speeds decrease in the decay phase of the cycle 23. There is an unusual drop in speed in the year 2001 and an abnormal increase in speed in the year 2003 due to the high concentration of CMEs, X-class soft X-ray flares, solar energetic particle (SEP) events and interplanetary shocks observed during October-November period called Halloween events. 相似文献
45.
在该文中,产业区是指从事同一生产过程不同阶段的生产和服务活动的专业化的中小企业组成特色的地方系统.在过去的10年中,我国专业化产业区和意大利式产业区的相似性已经被广泛关注.但是,我国的大量产业区因其非创新性的大批量制造而难以走出"低端道路"的困局,遭受经济危机的冲击.该文重温了意大利产业区模式.以新的视角探讨其核心价值,指出产业社区的文化根基以及持续创新的工业设计是其发展的动力源泉.在危机影响下变化的市场环境中,将大规模定制的生产模式引入产业区研究,并通过对比我国产业区与意大利式产业区,提出以设计为中心、加强技术创新与服务创新的产业区发展战略. 相似文献
46.
As a solid reservoir, a glacier can regulate regional water resources. The annual net mass balance directly reflects the
fluctuation of the glacier and climate variability. Based on 51 years of mass balance observation data, the mass balance of
Tianshan Mountains Urumqi Glacier No. 1 experienced a nine times positive balance fluctuation and nine times negative
balance fluctuation. There were 35 and 16 negative and positive balance years, respectively. From 1996/97 to 2008/09, 12
consecutive negative balance years were observed at Tianshan Mountains Urumqi Glacier No. 1. These results demonstrate
that the Urumqi Glacier No. 1 is experiencing a strong negative balance, and the strongest negative balance, -931
mm w.e. (mm water equivalent), during the observation period occurred in 2008. In addition, the cumulative mass balance
reached 13,709 mm w.e. in 2008. However, in 2009, the mass balance was positive at 63 mm w.e. The equilibrium-line altitude
changes with the fluctuation in the mass balance, and the effective mass balance gradient is 7.4 mm/m. In this paper,
the headwaters of the Urumqi River were analyzed using meteorological data from 1958 to 2009, including the average
seasonal temperature and precipitation. The results showed that the main factor associated with the mass balance variation
of Glacier No. 1 is the fluctuation in the summer air temperature, followed by changes in the precipitation. 相似文献
47.
张赤军 《大地测量与地球动力学》1998,(2)
根据推导的公式计算了由山体质量引起的梯度效应,结果与实测值甚为接近。分析了佘山重力垂直梯度偏小的原因,认为这是由于山体质量分布引起的。最后讨论了垂直梯度偏小对重力值的高度归算和大地水准面的影响。 相似文献
48.
CLIMATICTRENDINDICATEDBYVARIATIONSOFGLACIERSANDLAKESINTHETIANSHANMOUNTAINS¥HuRuji;YangChuande;MaHong;JiangFengqing(XinjiangIn... 相似文献
49.
利用振动工程中的模态分析技术,对桩基系统的振动特性进行研究。根据桩基系统的集中质量参数振动模型,对完整桩和各种缺损桩模型的导纳谱进行了大量的正演计算,按照导纳谱特征与桩基的缺损类型及缺损位置之间的对应关系,编制了相应的判读软件DSP1.0系统,实现了桩基完整性以及缺损桩缺损位置和缺损性质的计算机自动判读。 相似文献
50.
N. J. Lehtinen S. Pohjolainen K. Huttunen-Heikinmaa R. Vainio E. Valtonen A. E. Hillaris 《Solar physics》2008,247(1):151-169
A high-speed, halo-type coronal mass ejection (CME), associated with a GOES M4.6 soft X-ray flare in NOAA AR 0180 at S12W29
and an EIT wave and dimming, occurred on 9 November 2002. A complex radio event was observed during the same period. It included
narrow-band fluctuations and frequency-drifting features in the metric wavelength range, type III burst groups at metric – hectometric
wavelengths, and an interplanetary type II radio burst, which was visible in the dynamic radio spectrum below 14 MHz. To study
the association of the recorded solar energetic particle (SEP) populations with the propagating CME and flaring, we perform
a multi-wavelength analysis using radio spectral and imaging observations combined with white-light, EUV, hard X-ray, and
magnetogram data. Velocity dispersion analysis of the particle distributions (SOHO and Wind
in situ observations) provides estimates for the release times of electrons and protons. Our analysis indicates that proton acceleration
was delayed compared to the electrons. The dynamics of the interplanetary type II burst identify the burst source as a bow
shock created by the fast CME. The type III burst groups, with start times close to the estimated electron-release times,
trace electron beams travelling along open field lines into the interplanetary space. The type III bursts seem to encounter
a steep density gradient as they overtake the type II shock front, resulting in an abrupt change in the frequency drift rate
of the type III burst emission. Our study presents evidence in support of a scenario in which electrons are accelerated low
in the corona behind the CME shock front, while protons are accelerated later, possibly at the CME bow shock high in the corona. 相似文献