全文获取类型
收费全文 | 4996篇 |
免费 | 625篇 |
国内免费 | 806篇 |
专业分类
测绘学 | 1439篇 |
大气科学 | 1371篇 |
地球物理 | 764篇 |
地质学 | 658篇 |
海洋学 | 467篇 |
天文学 | 986篇 |
综合类 | 399篇 |
自然地理 | 343篇 |
出版年
2024年 | 22篇 |
2023年 | 57篇 |
2022年 | 90篇 |
2021年 | 147篇 |
2020年 | 150篇 |
2019年 | 174篇 |
2018年 | 123篇 |
2017年 | 167篇 |
2016年 | 196篇 |
2015年 | 240篇 |
2014年 | 259篇 |
2013年 | 308篇 |
2012年 | 283篇 |
2011年 | 321篇 |
2010年 | 247篇 |
2009年 | 364篇 |
2008年 | 328篇 |
2007年 | 376篇 |
2006年 | 326篇 |
2005年 | 294篇 |
2004年 | 245篇 |
2003年 | 216篇 |
2002年 | 201篇 |
2001年 | 171篇 |
2000年 | 120篇 |
1999年 | 122篇 |
1998年 | 164篇 |
1997年 | 116篇 |
1996年 | 108篇 |
1995年 | 96篇 |
1994年 | 83篇 |
1993年 | 67篇 |
1992年 | 49篇 |
1991年 | 42篇 |
1990年 | 36篇 |
1989年 | 35篇 |
1988年 | 26篇 |
1987年 | 17篇 |
1986年 | 11篇 |
1985年 | 4篇 |
1984年 | 9篇 |
1983年 | 1篇 |
1982年 | 3篇 |
1981年 | 2篇 |
1980年 | 5篇 |
1979年 | 1篇 |
1978年 | 2篇 |
1977年 | 1篇 |
1954年 | 2篇 |
排序方式: 共有6427条查询结果,搜索用时 15 毫秒
361.
The remote sensing observational study for infrared radiation of rocks was proceeded during the loading on rocks until failure.
The major instruments used in experiments were transient spectrum apparatus, intelligent spectrum apparatus, infrared radiation
thermometer, infrared spectrum radiometer, and infrared thermal imaging system. The experiments for 26 kinds of rocks were
made. The studies show that infrared radiation temperature of rocks increases along with increasing of stress. The amplitude
of infrared radiation spectrum of rocks also increases along with increasing of stress. The observational results of infrared
thermal imaging of rocks are consistent with infrared radiation temperature. Before formation of major faults for some rocks,
the belt-shape thermal imaging of temperature anomaly displaies in position of future major faults. This study has led the
new technology of remote sensing into rock mechanics and tend to establish a new field in rock mechanics — remote sensing
rock mechanics (or remote sensing rock physics). The application of remote sensing rock mechanics in prediction of earthquake
and rock burst, and in measurement of stress field in rock mass is expected.
The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,14, Supp., 645–652, 1992.
Jin-Shen HAO, Ji-Han LI, Xiao-Hong LIU, Yi-Qiao ZHI, Jin-Kai ZHANG, Yong-Hong Lü, Yi LIU, Yun-Shen YU, He ZHANG, Quan-Quan
JI, Xiao-Fan ZHU and Ning CHEN took part in this work.
This subject is supported by the Chinese Joint Seismological Science Foundation (91006).
Work of Institute of Geophysics, SSB (93A0009). 相似文献
362.
王建民 《紫金山天文台台刊》1999,18(3):271-273
频繁的超新星爆发可用以解释活动星系核与类星体的超高金属丰度。星团中的恒星与吸积盘相互作用导致致密天体中子星和黑洞的形成率很高,这些致密天体与红巨星很容易形成双星系统,而后形成(NS/BH,NS/BH) 双星由于引力辐射最终导致并合而形成伽玛射线爆发。我们估计了伽玛射线爆的爆发频率,发现与观测相符。 相似文献
363.
火烧迹地是全球及区域碳循环和气候变化等研究所需的重要参数之一,卫星遥感技术为快速获取大区域火烧迹地空间分布信息提供了有效手段。中国科学院基于Landsat系列卫星数据研发了首个30 m空间分辨率全球火烧迹地产品GABAM (Global Annual Burned Area Map)。遥感数据产品的精度验证对产品使用具有重要意义,迄今尚未有研究机构对GABAM产品精度进行独立评价和分析。为系统评价GABAM产品精度,利用2010年全球30 m空间分辨率火烧迹地产品(GABAM2010)开展精度验证研究工作,在全球和几个陆地生物群落中估算了产品精度,并探索了全球遥感专题产品精度验证的技术框架。基于分层随机抽样选择80个非重叠的泰森多边形区域TSA (Thiessen Scene Areas),采用误差矩阵和6个精度指标对GABAM2010产品做全面精度评价和分析,以满足火烧迹地产品用户的使用要求。结果表明:在全球范围内,GABAM2010产品的错分率和漏分率分别为24.32%和31.60%,总体精度为97.85%;由于数据质量(如条带、云)等的影响,火烧迹地的范围会被低估,对于较容易发生火灾的生物群落,如热带亚热带草原区域,GABAM2010产品精度较高;在生物群落内部,高密度火烧迹地区域的精度高于低密度火烧迹地区域。 相似文献
364.
365.
本文总结了1987年2月到1989年12月三波段(1.42GHz、2.84GHz和4.0GHz)高时间分辨率同步观测的资料,介绍了各波段尖峰辐射出现的频次、持续时间以及与射电爆发、光学耀斑和X射线爆的统计关系. 相似文献
366.
A.W. Jones R.J. Davis A. Wilkinson G. Giardino S.J. Melhuish H. Asareh R.D. Davies A.N. Lasenby 《Monthly notices of the Royal Astronomical Society》2001,327(2):545-551
We present the joint analysis of two 5-GHz interferometric surveys of the northern sky, taken with different baselines. The two surveys were carried out on the Jodrell Bank 5-GHz interferometer based at Manchester. The Maximum Entropy Method is used to check the consistency of the two surveys and the final two-dimensional maps are used, together with low-frequency full sky surveys, to put constraints on the Galactic spectral index. It is found that synchrotron emission is the dominant process at high Galactic latitudes below 5 GHz. 相似文献
367.
Stefano Casotto 《Celestial Mechanics and Dynamical Astronomy》1993,56(3):397-408
An analysis is presented of the orbital injection errors for the Lageos III satellite mission. Several methods are introduced for the solution of the Inverse Problem in the Theory of Errors. The novelty of the present approach consists in the use of the full geopotential covariance matrix in the error propagation equations. The GEM-T1 covariance matrix is used. It is found that by properly accounting for the correlation among the even zonal harmonic coefficients the acceptable error bounds increase by an order of magnitude with respect to the case when only the variances are used. The most stringent constraint, even when using the full covariance, is on inclination, whose nominal value must be realized within approximately 0.1° for the recovery of the Lense-Thirring precession to be successful at the 3% level (accounting only for injection errors). The associated tolerance in the semimajor axis is about 30 km while that in eccentricity is approximately 0.2. However, if the errors in semimajor axis and eccentricity can be kept to the routinely achievable levels respectively of 10 km and 0.004, then the tolerance in inclination can be relaxed to 0.2°. 相似文献
368.
YU Xuexiang associate professor Ph.D Department of Resource Environment Engineering Anhui University of Science Technology Huainan China. XU Shaoquan GAO Wei LU Weicai 《地球空间信息科学学报》2003,6(4):51-56
A new similar singledifference mathematical model ( SS-DM) and its corresponding algorithm are advanced to solve the deformation of monitoring point directly in single epoch. The method for building the SSDM is introduced in detail, and the main error sources affecting the accuracy of deformation measurement are analyzed briefly, and the basic algorithm and steps of solving the deformation are discussed. In order to validate the correctness and the accuracy of the similar single-difference model, the test with five dual frequency receivers is carried out on a slideway which moved in plane in Feb. 2001. In the test, five sessions are observed. The numerical results of test data show that the advanced model is correct. 相似文献
369.
The 3-hour-interval prediction of ground-level temperature from 00 h out to 45 h in South Korea(38 stations) is performed using the DLM (dynamic linear model) in order to eliminate the systematic error of numerical model forecasts. Numerical model forecasts and observations are used as input values of the DLM. According to the comparison of the DLM forecasts to the KFM (Kalman filter model) forecasts with RMSE and bias, the DLM is useful to improve the accuracy of prediction. 相似文献
370.
V. A. Brumberg 《Celestial Mechanics and Dynamical Astronomy》2003,85(3):269-291
The distinctive feature of the relativistic restricted three-body problem within the c
–5 order of accuracy (2
post-Newtonian approximation) is the presence of the gravitational radiation. To simplify the problem the motion of the massive binary components is assumed to be quasi-circular. In terms of time these orbits have linearly changing radii and quadratically changing phase angles. By substituting this motion into the Newtonian-like equations of motion one gets the quasi-Newtonian restricted quasi-circular three-body problem sufficient to take into account the main indirect perturbations caused by the binary radiation terms. Such problem admits the Lagrange-like quasi-libration solutions and rather simple quasi-circular orbits lying at large distance from the binary. 相似文献