全文获取类型
收费全文 | 66篇 |
免费 | 1篇 |
国内免费 | 1篇 |
专业分类
测绘学 | 7篇 |
大气科学 | 3篇 |
地球物理 | 4篇 |
地质学 | 17篇 |
海洋学 | 6篇 |
天文学 | 21篇 |
综合类 | 1篇 |
自然地理 | 9篇 |
出版年
2019年 | 1篇 |
2018年 | 1篇 |
2017年 | 1篇 |
2016年 | 1篇 |
2014年 | 3篇 |
2013年 | 2篇 |
2012年 | 2篇 |
2011年 | 5篇 |
2010年 | 2篇 |
2009年 | 6篇 |
2007年 | 3篇 |
2006年 | 2篇 |
2005年 | 1篇 |
2004年 | 4篇 |
2003年 | 2篇 |
2002年 | 2篇 |
2001年 | 1篇 |
1997年 | 1篇 |
1996年 | 2篇 |
1995年 | 2篇 |
1993年 | 2篇 |
1992年 | 2篇 |
1988年 | 5篇 |
1987年 | 1篇 |
1986年 | 4篇 |
1985年 | 1篇 |
1983年 | 1篇 |
1981年 | 3篇 |
1980年 | 2篇 |
1972年 | 1篇 |
1970年 | 1篇 |
1959年 | 1篇 |
排序方式: 共有68条查询结果,搜索用时 15 毫秒
1.
Irvine WM Friberg P Hjalmarson A Ishikawa S Kaifu N Kawaguchi K Madden SC Matthews HE Ohishi M Saito S Suzuki H Thaddeus P Turner BE Yamamoto S Ziurys LM 《The Astrophysical journal》1988,334(2):L107-L111
We report the astronomical identification of the cyanomethyl radical, CH2CN, the heaviest nonlinear molecular radical to be identified in interstellar clouds. The complex fine and hyperfine structures of the lowest rotational transitions at about 20.12 and 40.24 GHz are resolved in TMC-1, where the abundance appears to be about 5 x 10(-9) relative to that of H2. This is significantly greater than the observed abundance of CH3CN (methyl cyanide) in TMC-1. In Sgr B2 the hyperfine structure is blended in the higher frequency transitions at 40, 80, and 100 GHz, although the spin-rotation doubling is clearly evident. Preliminary searches in other sources indicate that the distribution of CH2CN is similar to that for such carbon chain species as HC3N or C4H. 相似文献
2.
Qingmin Meng Chris Cieszewski Marguerite Madden 《ISPRS Journal of Photogrammetry and Remote Sensing》2009,64(1):27-36
Large area forest inventory is important for understanding and managing forest resources and ecosystems. Remote sensing, the Global Positioning System (GPS), and geographic information systems (GIS) provide new opportunities for forest inventory. This paper develops a new systematic geostatistical approach for predicting forest parameters, using integrated Landsat 7 Enhanced Thematic Mapper Plus (ETM+) images, GPS, and GIS. Forest parameters, such as basal area, height, health conditions, biomass, or carbon, can be incorporated as a response variable, and the geostatistical approach can be used to predict parameter values for uninventoried points. Using basal area as the response and Landsat ETM+ images of pine stands in Georgia as auxiliary data, this approach includes univariate kriging (ordinary kriging and universal kriging) and multivariable kriging (co-kriging and regression kriging). The combination of bands 4, 3, and 2, as well as the combination of bands 5, 4, and 3, normalized difference vegetation index (NDVI), and principal components (PCs) were used in this study with co-kriging and regression kriging. Validation based on 200 randomly sampling points withheld field inventory was computed to evaluate the kriging performance and demonstrated that band combination 543 performed better than band combination 432, NDVI, and PCs. Regression kriging resulted in the smallest errors and the highest R-squared indicating the best geostatistical method for spatial predictions of pine basal area. 相似文献
3.
Megan Elwood Madden Shannon Ulrich Phillip Szymcek Scott McCallum Tommy Phelps 《Marine and Petroleum Geology》2009
In order for methane to be economically produced from the seafloor, prediction and detection of massive hydrate deposits will be necessary. In many cases, hydrate samples recovered from seafloor sediments appear as veins or nodules, suggesting that there are strong geologic controls on where hydrate is likely to accumulate. Experiments have been conducted examining massive hydrate accumulation from methane gas bubbles within natural and synthetic sediments in a large volume pressure vessel through temperature and pressure data, as well as visual observations. Observations of hydrate growth suggest that accumulation of gas bubbles within void spaces and at sediment interfaces likely results in the formation of massive hydrate deposits. Methane hydrate was first observed as a thin film forming at the gas/water interface of methane bubbles trapped within sediment void spaces. As bubbles accumulated, massive hydrate growth occurred. These experiments suggest that in systems containing free methane gas, bubble pathways and accumulation points likely control the location and habit of massive hydrate deposits. 相似文献
4.
Summary Comparisons between observed and modelled values of surface temperature, surface precipitation and 500 hPa height for the current climate were made for the southeast United States. Daily values and analyses pertinent to impact assessment, were emphasized. For the model, the time-independent 10-year series of values developed by the Geophysical Fluid Dynamics Laboratory general circulation model were used. Observations were drawn from records for various stations and decades within the model grid-cell. Cumulative frequency distributions of temperature indicated both more clustering close to the mean and greater extremes for the model. The model reproduced the seasonal cycle of day-to-day temperature variability, but introduced a phase shift of about four months. One result was an apparent overabundance of hot spells in the model results. For precipitation the model indicated twice as many raindays as were observed, about the same number of days when precipitation exceeded 5 mm, and fewer days with amounts exceeding 10 mm, effectively decreasing the probability of heavy precipitation while enhancing annual totals. In winter the model appeared to represent the results from an aggregation of stations within the grid-cell, but in summer it was closer to individual station results. The model reproduced the seasonal cycle in the height and standard deviation of the 500 hPa surface, with a damped amplitude in both cases.With 9 Figures 相似文献
5.
6.
7.
Shabir Ahmad M. I. Bhat Christopher Madden B. S. Bali 《Arabian Journal of Geosciences》2014,7(6):2225-2235
There are plenty of faults that show evidence that they are active. Most of the valley’s floor is occupied by unconsolidated Karewa deposits, in particular on the south–southwest of the Kashmir Valley. In such situations, geomorphic data can reveal the location of active faults. Accordingly, we tried to identify geomorphic indices in SW of the Kashmir Valley (Veshav, Rambiara, and Romushi drainage basins), which revealed the area to be potentially tectonically active. This active faulting was further substantiated by drainage anomalies and field investigations, which provides evidence for an emergent out-of-sequence NE-dipping active reverse fault (identified first time on ground) named the Balapur Fault (BF). The BF can be traced over at least 40 km along the southwest side of the Kashmir Valley. The existence of the active Balapur Fault and of two other inferred faults north of the Panjal Thrust or Murree Thrust presents a picture of a more complex strain-partitioning regime in the Kashmir Himalayas than is usually visualized. 相似文献
8.
The RHESSI Spectrometer 总被引:2,自引:0,他引:2
Smith D.M. Lin R.P. Turin P. Curtis D.W. Primbsch J.H. Campbell R.D. Abiad R. Schroeder P. Cork C.P. Hull E.L. Landis D.A. Madden N.W. Malone D. Pehl R.H. Raudorf T. Sangsingkeow P. Boyle R. Banks I.S. Shirey K. Schwartz Richard 《Solar physics》2002,210(1-2):33-60
RHESSI observes solar photons over three orders of magnitude in energy (3 keV to 17 MeV) with a single instrument: a set of
nine cryogenically cooled coaxial germanium detectors. With their extremely high energy resolution, RHESSI can resolve the
line shape of every known solar gamma-ray line except the neutron capture line at 2.223 MeV. High resolution also allows clean
separation of thermal and non-thermal hard X-rays and the accurate measurement of even extremely steep power-law spectra.
Detector segmentation, fast signal processing, and two sets of movable attenuators allow RHESSI to make high-quality spectra
and images of flares across seven orders of magnitude in intensity. Here we describe the configuration and operation of the
RHESSI spectrometer, show early results on in-flight performance, and discuss the principles of spectroscopic data analysis
used by the RHESSI software. 相似文献
9.
Madden P.G.A. Madden J.D.W. Anquetil P.A. Vandesteeg N.A. Hunter I.W. 《Oceanic Engineering, IEEE Journal of》2004,29(3):696-705
Materials used in many branches of engineering are of low molecular weight and not flexible. As we develop more sophisticated engineering devices one can look to nature for inspiration and advocate the use of high molecular weight flexible materials. Conducting polymer actuators will soon be used in applications where traditional low molecular weight actuator systems are incapable of mimicking the functionality provided by nature's muscle. To incorporate conducting polymer actuators into engineering systems it is of high importance to not only model and predict the behavior of these actuators but also understand the connection of material properties to performance. In this paper, the importance of fundamental actuation mechanisms and the fundamental material properties of conducting polymer muscles such as ionic diffusion rate, electrochemical operating window, strain to charge ratio, ratio of charge carried by positive versus negative ions, and salt draining are discussed and their effect on performance is demonstrated. The relevance of engineered geometry to the performance of conducting polymer muscles is also shown. Our understanding of what limits the performance of existing conducting polymers actuators provides directions for the improvement of the next generation of conducting polymer actuators. 相似文献
10.
Suzanne C. Madden 《Astrophysics and Space Science》2002,281(1-2):247-252
The properties of the low metallicity environments of dwarf galaxies are studied through dust observations in conjunction
with the FIR fine-structure cooling lines. There is a striking enhancement of the I[CII]/I(CO) in dwarf galaxies that is explained
by the decreased attenuation of the UV light in molecular clouds. An important consequence is that a significant mass of the
molecular gas mass inventory can be missed through CO observations alone. Modeling the infrared spectral energy distribution
into submillimeter wavelengths in dwarf galaxies reveals the presence of very cold (∼ 8K) dust,which accounts for a large
fraction of the dust mass, until now missed by models using IRAS observations alone. In spite of the striking defficiency
of the mid-infrared aromatic band carriers, cooling in the photodissociation regions, via [CII] line emission is a very efficient
process.
This revised version was published online in September 2006 with corrections to the Cover Date. 相似文献