全文获取类型
| 收费全文 | 3183篇 |
| 免费 | 469篇 |
| 国内免费 | 444篇 |
专业分类
| 测绘学 | 135篇 |
| 大气科学 | 931篇 |
| 地球物理 | 521篇 |
| 地质学 | 369篇 |
| 海洋学 | 252篇 |
| 天文学 | 1471篇 |
| 综合类 | 111篇 |
| 自然地理 | 306篇 |
出版年
| 2024年 | 4篇 |
| 2023年 | 34篇 |
| 2022年 | 51篇 |
| 2021年 | 77篇 |
| 2020年 | 64篇 |
| 2019年 | 63篇 |
| 2018年 | 63篇 |
| 2017年 | 61篇 |
| 2016年 | 65篇 |
| 2015年 | 106篇 |
| 2014年 | 128篇 |
| 2013年 | 136篇 |
| 2012年 | 128篇 |
| 2011年 | 140篇 |
| 2010年 | 121篇 |
| 2009年 | 247篇 |
| 2008年 | 223篇 |
| 2007年 | 253篇 |
| 2006年 | 220篇 |
| 2005年 | 223篇 |
| 2004年 | 182篇 |
| 2003年 | 184篇 |
| 2002年 | 185篇 |
| 2001年 | 153篇 |
| 2000年 | 154篇 |
| 1999年 | 144篇 |
| 1998年 | 125篇 |
| 1997年 | 87篇 |
| 1996年 | 78篇 |
| 1995年 | 82篇 |
| 1994年 | 76篇 |
| 1993年 | 52篇 |
| 1992年 | 33篇 |
| 1991年 | 38篇 |
| 1990年 | 21篇 |
| 1989年 | 23篇 |
| 1988年 | 19篇 |
| 1987年 | 16篇 |
| 1986年 | 8篇 |
| 1985年 | 4篇 |
| 1984年 | 7篇 |
| 1983年 | 1篇 |
| 1982年 | 4篇 |
| 1981年 | 4篇 |
| 1980年 | 4篇 |
| 1979年 | 1篇 |
| 1978年 | 2篇 |
| 1977年 | 1篇 |
| 1954年 | 1篇 |
排序方式： 共有4096条查询结果，搜索用时 203 毫秒
31.
32.
Three dimensional numerical simulation of residential building on shrink–swell soils in response to climatic conditions 
下载免费PDF全文
下载免费PDF全文 Shrink–swell soils can cause distresses in buildings, and every year, the economic loss associated with this problem is huge. This paper presents a comprehensive system for simulating the soil–foundation–building system and its response to daily weather conditions. Weather data include rainfall, solar radiation, air temperature, relative humidity, and wind speed, all of which are readily available from a local weather station or the Internet. These data are used to determine simulation flux boundary conditions. Different methods are proposed to simulate different boundary conditions: bare soil, trees, and vegetation. A coupled hydro‐mechanical stress analysis is used to simulate the volume change of shrink–swell soils due to both mechanical stress and water content variations. Coupled hydro‐mechanical stress‐jointed elements are used to simulate the interaction between the soil and the slab, and general shell elements are used to simulate structural behavior. All the models are combined into one finite element program to predict the entire system's behavior. This paper first described the theory for the simulations. A site in Arlington, Texas, is then selected to demonstrate the application of the proposed system. Simulation results are shown, and a comparison between measured and predicted movements for four footings in Arlington, Texas, over a 2‐year period is presented. Finally, a three‐dimensional simulation is made for a virtual residential building on shrink–swell soils to identify the influence of various factors. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
33.
34.
35.
Experiments on ion implantation were performed in order to better characterize diffusion of noble gases in lunar soil.4He+ at 50 keV with 5×1016 ions/cm2 was implanted into lunar simulants and crystal ilmenite.Helium in the samples was released by stepwise heating experiments.Based on the data,we calculated the helium diffusion coefficient and activation energy.Lunar simulants display similar 4He release patterns in curve shape as lunar soil,but release temperatures are a little lower.This is probably a con... 相似文献
36.
The effect of UV-B radiation enhancement at experimental doses of 0.00,0.24,0.48,0.72,0.96,and 1.20 kJ/m 2 on the population dynamics of the rotifer Brachionus urceus feeding on the alga Chlorella sp.was studied under controlled laboratory conditions using clonal culture and life-table techniques.The results show that UV-B radiation treatment significantly shortened the survival time of the rotifer (P <0.05): The longest survival time (336 h) occurred in the control (0.00 kJ/m 2 ) while the shortest (222 h) occurred when exposed to the highest UV-B radiation treatment (1.20 kJ/m 2 ).The fecundity of the rotifer B.urceus was enhanced by the lower UV-B radiation treatment (0.24 and 0.48 kJ/m 2 ) but inhibited by the higher treatments (0.96 and 1.20 kJ/m 2 ).Life expectancy also was obviously affected by UV-B radiation (P <0.05).The highest life expectancy occurred in the control (0.00 kJ/m 2 ),and it became shorter with increasing doses of UV-B radiation.The resutls in the present study indicate that the life expectancy of the rotifer B.urceus can be used as an indicator for UV-B radiation enhancement. 相似文献
37.
The effect of wave-induced radiation stress on storm surge during Typhoon Saomai (2006) 总被引：5，自引：1，他引：4
The effects of wave-induced radiation stress on storm surge were simulated during Typhoon Saomai using a wave-current coupled model based on ROMS (Regional Ocean Modeling System) ocean model and SWAN (Simulating Waves Nearshore) wave model.The results show that radiation stress can cause both set-up and set-down in the storm surge.Wave-induced set-up near the coast can be explained by decreasing significant wave heights as the waves propagate shoreward in an approximately uniform direction;wave-induced set-down far from the coast can be explained by the waves propagating in an approximately uniform direction with increasing significant wave heights.The shoreward radiation stress is the essential reason for the wave-induced set-up along the coast.The occurrence of set-down can be also explained by the divergence of the radiation stress.The maximum wave-induced set-up occurs on the right side of the Typhoon path,whereas the maximum wave induced set-down occurs on the left side. 相似文献
38.
Researches on breaking-induced currents by waves are summarized firstly in this paper. Then, a combined numerical model in orthogonal curvilinear coordinates is presented to simulate wave-induced current in areas with curved boundary or irregular coastline. The proposed wave-induced current model includes a nearshore current module established through orthogonal curvilinear transformation form of shallow water equations and a wave module based on the curvilinear parabolic approximation wave equation. The wave module actually serves as the driving force to provide the current module with required radiation stresses. The Crank-Nicolson finite difference scheme and the alternating directions implicit method are used to solve the wave and current module, respectively. The established surf zone currents model is validated by two numerical experiments about longshore currents and rip currents in basins with rip channel and breakwater. The numerical results are compared with the measured data and published numerical results. 相似文献
39.
40.