全文获取类型
收费全文 | 831篇 |
免费 | 22篇 |
国内免费 | 8篇 |
专业分类
测绘学 | 18篇 |
大气科学 | 39篇 |
地球物理 | 164篇 |
地质学 | 303篇 |
海洋学 | 63篇 |
天文学 | 203篇 |
综合类 | 2篇 |
自然地理 | 69篇 |
出版年
2021年 | 8篇 |
2020年 | 11篇 |
2019年 | 4篇 |
2018年 | 15篇 |
2017年 | 10篇 |
2016年 | 12篇 |
2015年 | 5篇 |
2014年 | 14篇 |
2013年 | 33篇 |
2012年 | 21篇 |
2011年 | 24篇 |
2010年 | 14篇 |
2009年 | 52篇 |
2008年 | 19篇 |
2007年 | 30篇 |
2006年 | 28篇 |
2005年 | 31篇 |
2004年 | 21篇 |
2003年 | 47篇 |
2002年 | 24篇 |
2001年 | 19篇 |
2000年 | 26篇 |
1999年 | 21篇 |
1998年 | 17篇 |
1997年 | 18篇 |
1996年 | 15篇 |
1995年 | 21篇 |
1994年 | 19篇 |
1993年 | 11篇 |
1992年 | 17篇 |
1991年 | 7篇 |
1990年 | 14篇 |
1989年 | 8篇 |
1988年 | 12篇 |
1987年 | 13篇 |
1986年 | 9篇 |
1985年 | 22篇 |
1984年 | 23篇 |
1983年 | 12篇 |
1982年 | 16篇 |
1981年 | 12篇 |
1980年 | 12篇 |
1979年 | 11篇 |
1978年 | 11篇 |
1977年 | 12篇 |
1976年 | 4篇 |
1975年 | 8篇 |
1974年 | 11篇 |
1973年 | 6篇 |
1926年 | 3篇 |
排序方式: 共有861条查询结果,搜索用时 31 毫秒
131.
An analytical solution for rapid (undrained) expansion of a long cylindrical cavity from initially zero radius is presented. A simple rate-type soil model possessing the salient features of the modified Cambridge critical state model is used. Application of the solution to determination of the stress field surrounding a pile immediately after driving is discussed. 相似文献
132.
R.J. Morris M.J. McCartney A.G. Howard M.H. Arbab-Zavar J.S. Davis 《Marine Chemistry》1984,14(3):259-265
Dissolved inorganic arsenic and phosphate levels present in an enclosed experimental ecosystem have been studied during the course of a natural spring diatom bloom. Whilst phosphate levels dropped rapidly to almost zero as the bloom developed, arsenic levels remained constant even when arsenate levels exceeded the dissolved phosphate. Certain diatom species (Thalassiosira spp., Chaetoceras spp. and Skeletonema costatum) therefore appear to be capable of discriminating, either by uptake or excretion, between phosphate and arsenate. The implications of such findings are discussed. 相似文献
133.
Brian P. Reen David R. Stauffer Kenneth J. Davis Ankur R. Desai 《Boundary-Layer Meteorology》2006,120(2):275-314
The importance of soil moisture inputs and improved model physics in the prediction of the daytime boundary-layer structure during the Southern Great Plains Hydrology Experiment 1997 (SGP97) is investigated using the non-hydrostatic fifth-generation Pennsylvania State University/National Center for Atmospheric Research (PSU/NCAR) Mesoscale Model MM5. This is Part II of a two-part study examining the relationship of surface heterogeneity to observed boundary-layer structure. Part I focuses on observations and utilizes a simple model while Part II uses observations and MM5 modelling. Soil moisture inputs tested include a lookup table based on soil type and season, output from an offline land-surface model (LSM) forced by atmospheric observations, and high-resolution ( 800 m) airborne microwave remotely sensed data. Model physics improvements are investigated by comparing an LSM directly coupled with the MM5 to a simpler force-restore method at the surface. The scale of land surface heterogeneities is compared to the scale of their effects on boundary-layer structure.The use of more detailed soil moisture fields allowed the MM5 to better represent the large-scale (hundreds of km) and small-scale (tens of km) horizontal gradients in surface-layer weather and, to a lesser degree, the atmospheric boundary-layer (ABL) height, which was evaluated against observations measured by differential absorption lidar (DIAL). The benefits of coupling an LSM to the MM5 were not readily evident in this summertime case, with the model having particular difficulty simulating the timing of maximum surface fluxes while underestimating the depth of the mixed layer. 相似文献
134.
Chris Blake Russell J. Jurek Sarah Brough Matthew Colless Warrick Couch Scott Croom Tamara Davis Michael J. Drinkwater Duncan Forbes Karl Glazebrook Barry Madore Chris Martin Kevin Pimbblet Gregory B. Poole Michael Pracy Rob Sharp Todd Small David Woods 《Monthly notices of the Royal Astronomical Society》2009,395(1):240-254
135.
136.
137.
Bao Yang Achim Bruning Jingjing Liu Mary E. Davis Shao Yajun 《Global and Planetary Change》2009,69(1-2):71-78
The climatological signal of δ18O variations preserved in ice cores recovered from Puruogangri ice field in the central Tibetan Plateau (TP) was calibrated with regional meteorological data for the past 50 years. For the period AD 1860–2000, 5-yearly averaged ice core δ18O and a summer temperature reconstruction derived from pollen data from the same ice core were compared. The statistical results provide compelling evidence that Puruogangri ice core δ18O variations represent summer temperature changes for the central TP, and hence regional temperature history during the past 600 years was revealed. A comparison of Puruogangri ice core δ18О with several other temperature reconstructions shows that broad-scale climate anomalies since the Little Ice Age occurred synchronously across the eastern and southern TP, and the Himalayas. Common cold periods were identified in the 15th century, 1625–1645 AD, 1660–1700 AD, 1725–1775 AD, 1795–1830 AD, 1850–1870 AD, 1890–1920 AD, 1940–1950 AD, and 1975–1985 AD. The period 1725–1775 AD was one of the most prolonged cool periods during the past 400 years and corresponded to maximum Little Ice Age glacier advance of monsoonal temperate glaciers of the TP. 相似文献
138.
The kinetics of iodide (I−) and molecular iodine (I2) oxidation by the manganese oxide mineral birnessite (δ-MnO2) was investigated over the pH range 4.5-6.25. I− oxidation to iodate proceeded as a two-step reaction through an I2 intermediate. The rate of the reaction varied with both pH and birnessite concentration, with faster oxidation occurring at lower pH and higher birnessite concentration. The disappearance of I− from solution was first order with respect to I− concentration, pH, and birnessite concentration, such that −d[I−]/dt = k[I−][H+][MnO2], where k, the third order rate constant, is equal to 1.08 ± 0.06 × 107 M−2 h−1. The data are consistent with the formation of an inner sphere I− surface complex as the first step of the reaction, and the adsorption of I− exhibited significant pH dependence. Both I2, and to a lesser extent, sorbed to birnessite. The results indicate that iodine transport in mildly acidic groundwater systems may not be conservative. Because of the higher adsorption of the oxidized I species I2 and , as well as the biophilic nature of I2, redox transformations of iodine must be taken into account when predicting I transport in aquifers and watersheds. 相似文献
139.
140.
N. Lugaz P. Kintner C. M?stl L. K. Jian C. J. Davis C. J. Farrugia 《Solar physics》2012,279(2):497-515
We present a study of coronal mass ejections (CMEs) which impacted one of the STEREO spacecraft between January 2008 and early 2010. We focus our study on 20 CMEs which were observed remotely by the Heliospheric Imagers (HIs) onboard the other STEREO spacecraft up to large heliocentric distances. We compare the predictions of the Fixed-?? and Harmonic Mean (HM) fitting methods, which only differ by the assumed geometry of the CME. It is possible to use these techniques to determine from remote-sensing observations the CME direction of propagation, arrival time and final speed which are compared to in-situ measurements. We find evidence that for large viewing angles, the HM fitting method predicts the CME direction better. However, this may be due to the fact that only wide CMEs can be successfully observed when the CME propagates more than 100° from the observing spacecraft. Overall eight CMEs, originating from behind the limb as seen by one of the STEREO spacecraft can be tracked and their arrival time at the other STEREO spacecraft can be successfully predicted. This includes CMEs, such as the events on 4 December 2009 and 9 April 2010, which were viewed 130° away from their direction of propagation. Therefore, we predict that some Earth-directed CMEs will be observed by the HIs until early 2013, when the separation between Earth and one of the STEREO spacecraft will be similar to the separation of the two STEREO spacecraft in 2009??C?2010. 相似文献