全文获取类型
收费全文 | 5452篇 |
免费 | 1068篇 |
国内免费 | 1101篇 |
专业分类
测绘学 | 134篇 |
大气科学 | 970篇 |
地球物理 | 1942篇 |
地质学 | 2045篇 |
海洋学 | 824篇 |
天文学 | 679篇 |
综合类 | 426篇 |
自然地理 | 601篇 |
出版年
2024年 | 24篇 |
2023年 | 68篇 |
2022年 | 165篇 |
2021年 | 193篇 |
2020年 | 199篇 |
2019年 | 228篇 |
2018年 | 228篇 |
2017年 | 239篇 |
2016年 | 220篇 |
2015年 | 239篇 |
2014年 | 320篇 |
2013年 | 343篇 |
2012年 | 321篇 |
2011年 | 292篇 |
2010年 | 288篇 |
2009年 | 396篇 |
2008年 | 342篇 |
2007年 | 400篇 |
2006年 | 326篇 |
2005年 | 326篇 |
2004年 | 283篇 |
2003年 | 266篇 |
2002年 | 221篇 |
2001年 | 190篇 |
2000年 | 232篇 |
1999年 | 207篇 |
1998年 | 202篇 |
1997年 | 159篇 |
1996年 | 145篇 |
1995年 | 114篇 |
1994年 | 106篇 |
1993年 | 81篇 |
1992年 | 72篇 |
1991年 | 51篇 |
1990年 | 23篇 |
1989年 | 25篇 |
1988年 | 19篇 |
1987年 | 17篇 |
1986年 | 11篇 |
1985年 | 12篇 |
1984年 | 4篇 |
1983年 | 3篇 |
1982年 | 6篇 |
1981年 | 3篇 |
1979年 | 7篇 |
1978年 | 3篇 |
1954年 | 2篇 |
排序方式: 共有7621条查询结果,搜索用时 15 毫秒
91.
Daoyong ZHANG Xiangliang PAN Shuimu LIAO Chenglin HUANG Jingmei ZHANG 《中国地球化学学报》2006,25(B08):133-133
Low molecular weight organic acids (LMWOAs) are important components of root exudates. They play an important role in immobilizing and remobilizing contaminants in rhizospheric soil. Effects of four LMWOAs on the sorption and desorption behavior of p-chlorophenol by yellow earth was studied in batch mode. The results showed that the previous application of LMWOAs to enhanced adsorption capacity of p-chlorophenol of the soil in the order of maleic acid〉malic acid〉oxalic acid〉citric acid. However, when LMWOAs were applied to soil where p-chlorophenol had been previously adsorbed, substantial p-chlorophenol was desorbed from soil by oxalic acid, whereas citric acid, malic acid and maleic acid didn't desorb as much p-chlorophenol from soil as deionized water. 相似文献
92.
Seismic activity associated with the subducting motion of the Philippine Sea plate beneath the Kanto district, Japan 总被引:1,自引:1,他引:1
Sadaki Hori 《Tectonophysics》2006,417(1-2):85
The Pacific plate and the Philippine Sea plate overlap and subduct underneath the Kanto region, central Japan, causing complex seismic activities in the upper mantle. In this research, we used a map selection tool with a graphic display to create a data set for earthquakes caused by the subducting motion of the Philippine Sea plate that are easily determined. As a result, we determined that there are at least four earthquake groups present in the upper mantle above the Pacific plate. Major seismic activity (Group 1) has been observed throughout the Kanto region and is considered to originate in the uppermost part of mantle in the subducted Philippine Sea plate, judging from the formation of the focal region and comparison with the 3D structure of seismic velocity. The focal mechanism of these earthquakes is characterized by the down-dip compression. A second earthquake layer characterized by down-dip extension (Group 2), below the earthquakes in this group, is also noted. The focal region for those earthquakes is considered to be located at the lower part of the slab mantle, and the Pacific plate located directly below is considered to influence the activity. Earthquakes located at the shallowest part (Group 3) form a few clusters distributed directly above the Group 1 focal region. Judging from the characteristics of later phases in these earthquakes and comparing against the 3D structure of seismic velocity, the focal regions for the earthquakes are considered to be located near the upper surface of the slab. Another earthquake group (Group 4) originates further below Group 2; it is difficult to consider these earthquakes within a single slab. The seismic activities representing the upper area of the Philippine Sea plate are Group 3. This paper proposes a slab geometry model that is substantially different from conventional models by strictly differentiating the groups. 相似文献
93.
94.
95.
96.
LI Zheng-xi 《吉林大学学报(地球科学版)》2006,(Z2)
对低阻油气储层的测井响应特征和储层物性特征进行了研究,并针对研究区域低阻储层的特点,以岩心与测井数据的相关性为依据,提出了适合地区特点的储层参数解释方法。通过应用三水导电模型,提高了低阻储层的测井解释精度。 相似文献
97.
探讨了运用GIS技术对供电台区经营综合评价的实现方法,选取了业务属性和空间属性两个方面评价因子,介绍了从系统软硬件、评价实现过程及显示结果等方面评价过程的具体技术实现。 相似文献
98.
99.
阿克库勒地区卡拉沙依组碎屑岩储层的成分成熟度和结构成熟度均较低.储层的次生溶蚀孔隙所占比例远高了:原生孔隙,次生孔隙是储层的主要储集空间.样品数据统计显示,卡拉沙依组储层属于低孔、低渗储层类型.根据岩石薄片、铸体薄片观察及储层样品的扫描电镜和阴极发光分析结果,本区石炭系储层主要经历的成岩作用有压实(压溶)作用、胶结作用、溶蚀作用和交代作用,其中碳酸盐矿物的沉淀和溶蚀作用是本区卡拉沙依组储层所经历的最重要的成岩作用.成岩作用已达到晚成岩B期,早期方解石交代石英颗粒并发生大量溶蚀,生成大量次生孔隙,晚期方解石没有发生溶蚀. 相似文献
100.
过硫酸铵氧化容量法测定矿石中锰方法的改进 总被引:5,自引:1,他引:5
采用过硫酸铵氧化容量法测定锰时,可在低酸度(0.18mol/LH2SO4、0.29mol/LH3PO4)和大体积(300mL)溶液中氧化Mn2 至Mn7 。所测得的结果十分稳定,回收率为100%。采用管理样分析验证方法,其结果与铋酸钠容量法结果一致。对于w(Mn)=11.36%的试样进行10次分析测定,RSD=0.33%。方法可测定w(Mn)≥0.01%的常见矿种样品。 相似文献