全文获取类型
收费全文 | 460篇 |
免费 | 64篇 |
国内免费 | 95篇 |
专业分类
测绘学 | 29篇 |
大气科学 | 79篇 |
地球物理 | 157篇 |
地质学 | 167篇 |
海洋学 | 61篇 |
天文学 | 4篇 |
综合类 | 55篇 |
自然地理 | 67篇 |
出版年
2024年 | 7篇 |
2023年 | 10篇 |
2022年 | 23篇 |
2021年 | 36篇 |
2020年 | 41篇 |
2019年 | 20篇 |
2018年 | 55篇 |
2017年 | 47篇 |
2016年 | 45篇 |
2015年 | 34篇 |
2014年 | 31篇 |
2013年 | 31篇 |
2012年 | 34篇 |
2011年 | 43篇 |
2010年 | 12篇 |
2009年 | 41篇 |
2008年 | 17篇 |
2007年 | 25篇 |
2006年 | 18篇 |
2005年 | 15篇 |
2004年 | 5篇 |
2003年 | 11篇 |
2002年 | 5篇 |
2001年 | 3篇 |
2000年 | 1篇 |
1999年 | 1篇 |
1998年 | 1篇 |
1996年 | 4篇 |
1992年 | 1篇 |
1983年 | 2篇 |
排序方式: 共有619条查询结果,搜索用时 15 毫秒
211.
212.
JCZ-1T超宽频带地震计作为综合观测仪器的拓展应用 总被引:1,自引:1,他引:1
JCZ-1T超宽频带地震计具有全频带覆盖特性,其低频端输出延伸到固体潮汐,提出了获取稳定的低频端数据的观测条件.利用地震计LP通道连续观测数据中的垂直分向数据经过处理获得的重力资料,以及水平分向数据经过处理获得的倾斜资料做了Venedikov调和分析.对印尼8.7级大地震数据进行处理,获得地球自由振荡的功率谱密度.仪器可获取与地震事件密切相关的综合观测数据. 相似文献
213.
Offset geomorphic features and deformed late Quaternary strata indicate active deformation along the Langshan-Seertengshan piedmont fault (LSPF), one of the most active faults in the Hetao fault zone in Inner Mongolia, North China. The widespread occurrence of bedrock fault scarps along the LSPF offers excellent opportunity to examine the faulting history. Using cosmogenic 10Be exposure dating, we measured the exposure ages of the western Langshankou scarp, located in the middle segment of the LSPF. Our data revealed at least two earthquakes that occurred at 22.2±3.3 ka and 7.2±2.4 ka, respectively. These events are consistent with previous paleoseismic trench studies. The regression of the relationship between the age and sampling height along the scarp yield a fault slip rate of 0.10 +0.05/-0.06 mm/yr, which is significantly lower than the average post-late Pleistocene fault slip rate of ~1 mm/yr, as estimated from the offset of the T2 terraces by previous studies. This indicates that the slip of the LSPF may have been accommodated by other fault branches. 相似文献
214.
利用寻乌及邻区2009年以来的地震波形资料,采用Snoke方法反演19次ML2.5以上地震的震源机制,计算89次ML1.5以上地震的视应力。结果显示,寻乌及邻区的走滑型地震占绝对优势,震源机制解P轴优势方向分布在310°~320°和110°~130°之间,倾角绝大多数在40°以内,与该区以NWW-SEE向水平挤压为特征的构造应力场吻合;寻乌震群集中区内8次ML2.5以上地震的震源机制结果一致性较好。寻乌及邻区视应力与震级呈正相关,2017-11-06寻乌ML3.8震群前的差视应力值出现高值波动。 相似文献
215.
Guo Chaonan Sun Chengjun Yang Guipeng Zhang Honghai Chen Yan Yin Xiaofei Jiang Fenghua Huang Yuhuan Niu Jiaohong Ding Haibing 《中国海洋湖沼学报》2020,38(3):606-618
Journal of Oceanology and Limnology - The concentrations of dissolved monosaccharides (MCHO), polysaccharides (PCHO), and total carbohydrates (TCHO) in the seawater samples collected from the north... 相似文献
216.
Zygosaccharomyces rouxii is a salt-tolerant yeast species capable of removing cadmium(Cd) pollutant from aqueous solution. Presently, the physiological characteristics of Z. rouxii under the stress of sodium chloride(NaCl) and Cd are poorly understood. This study investigated the effects of NaCl and Cd on the growth, oxidative stress and antioxidant enzyme activities of Z. rouxii after stress treatment for 24 h. Results showed that NaCl or Cd alone negatively affected the growth of Z. rouxii, but the growth-inhibiting effect of Cd on Z. rouxii was reduced in the presence of NaCl. Flow cytometry assay showed that under Cd stress, NaCl significantly reduced the production of reactive oxygen species(ROS) and cell death of Z. rouxii compared with those in the absence of NaCl. The activities of superoxide dismutase(SOD), catalase(CAT), and peroxidase(POD) of Z. rouxii were significantly enhanced by 2%–6% NaCl, which likely contributed to the high salt tolerance of Z. rouxii. The POD activity was inhibited by 20 mg L-1Cd while the SOD and CAT activities were enhanced by 8 mg L-1 Cd and inhibited by 20 mg L-1 or 50 mg L-1 Cd. The inhibitory effect of high-level Cd on the antioxidant enzyme activities of Z. rouxii was counteracted by the combined use of NaCl, especially at 6%. This probably accounted for the decrease in Cd-induced ROS production and cell death of Z. rouxii after incubation with NaCl and Cd. Our work provided physiological clues as to the use of Z. rouxii as a biosorbent for Cd removal from seawater and liquid highly salty food. 相似文献
217.
文章主要阐述了如何将数值预报产品与天气学预报经验有机的结合起来。天气学着重研究天气系统进入本地区前各方面的动态变化,从中找出它的变化规律,再利用这些规律预测未来如何演变。数值预报从初始场开始,计算它的运动轨迹,着重研究大气环流和天气形势未来变化。虽然它们的研究起点、研究重点不同,但方向一致。把二者有机结合起来,可以形成从过去、现在到未来的一个完整的链条,从而有力的促进了预报质量的提高。 相似文献
218.
Gas to Dust Ratio (GDR) indicates the mass ratio of interstellar gas to dust. It is widely adopted that the GDR in our Galaxy is 100~150. We choose three typical star forming regions to study the GDR: the Orion molecular cloud — a massive star forming region, the Taurus molecular cloud — a low-mass star forming region, and the Polaris molecular cloud — a region with no or very few star formation activities. The mass of gas only takes account of the neutral gas, i.e. only the atomic and molecular hydrogen, because the amount of ionized gas is very small in a molecular cloud. The column density of atomic hydrogen is taken from the high-resolution and high-sensitivity all-sky survey EBHIS (Effelsberg-Bonn HI Survey). The CO J = 1 →0 line is used to trace the molecular hydrogen, since the spectral lines of molecular hydrogen which can be detected are rare. The intensity of CO J = 1 →0 line is taken from the Planck all-sky survey. The mass of dust is traced by the interstellar extinction based on the 2MASS (Two Micron All Sky Survey) photometric database in the direction of anti-Galactic center. Adopting a constant conversion coefficient from the integrated intensity of the CO line to the column density of molecular hydrogen, XCO = 2.0 × 1020 cm?2 · (K · km/s)?1, the gas to dust ratio N(H)/AV is calculated, which is 25, 38, and 55 (in units of 1020 cm?2 · mag?1) for the Orion, Taurus, and Polaris molecular clouds, respectively. These values are significantly higher than the previously obtained average value of the Galaxy. Adopting the WD01 interstellar dust model (when the V-band selective extinction ratio is RV = 3.1), the derived GDRs are 160, 243, and 354 for the Orion, Taurus, and Polaris molecular clouds, respectively, which are apparently higher than 100~150, the commonly accepted GDR of the diffuse interstellar medium. The high N(H)/AV values in the star forming regions may be explained by the growth of dust in the molecular clouds because of either the particle collision or accretion, which can lead to the reduction of extinction efficiency per unit mass in the V band, rather than the increase of the GDR itself. 相似文献
219.
通过邢台地区历史地震烈度资料分析,得到该地区烈度—频率灾害曲线及地震风险。以地震地质资料理论为基础,结合河北省城市活断层探测成果、地壳结构等资料,确定2个设定地震事件。采用复合震源模型,模拟合成强地面运动,并基于强地面运动模拟结果,分析邢台地区地震影响烈度,为今后该地区建筑物抗震设防、避难场所选址、震后救援以及地震保险风险评估提供参考依据。 相似文献
220.
城市绿色空间格局时空演变及其生态系统服务评价的研究进展与展望 总被引:1,自引:1,他引:1
科学合理的城市绿色空间格局是城市可持续发展的物质空间保障,对其时空演变和影响因素进行研究,可揭示城市绿色空间在城市化进程中各要素与演变过程的复杂关系,以确保城市生态系统服务功能的正常发挥。在生态文明建设背景下,城市绿色空间将在多尺度国土空间规划中发挥积极作用,然而城市绿色空间规划与国土空间规划如何衔接却有待商榷。因此,论文在梳理城市绿色空间概念界定和发展历程的基础上,一方面讨论城市绿色空间格局的时空评价、驱动因子、情景模拟及优化策略的研究进展;另一方面总结生态系统服务在城市绿色空间格局评价中的应用进展。通过归纳以上研究内容,提出国土空间规划体系中有关城市绿色空间格局的评价及优化框架,以期为新时代背景下的城市绿色空间规划提供参考。 相似文献