全文获取类型
收费全文 | 57399篇 |
免费 | 10208篇 |
国内免费 | 14596篇 |
专业分类
测绘学 | 4293篇 |
大气科学 | 7552篇 |
地球物理 | 10970篇 |
地质学 | 34448篇 |
海洋学 | 7654篇 |
天文学 | 2153篇 |
综合类 | 4171篇 |
自然地理 | 10962篇 |
出版年
2024年 | 133篇 |
2023年 | 597篇 |
2022年 | 1708篇 |
2021年 | 1930篇 |
2020年 | 2029篇 |
2019年 | 2265篇 |
2018年 | 1992篇 |
2017年 | 2189篇 |
2016年 | 2371篇 |
2015年 | 2575篇 |
2014年 | 3272篇 |
2013年 | 3184篇 |
2012年 | 3558篇 |
2011年 | 3760篇 |
2010年 | 3113篇 |
2009年 | 3770篇 |
2008年 | 3735篇 |
2007年 | 4138篇 |
2006年 | 4057篇 |
2005年 | 3604篇 |
2004年 | 3404篇 |
2003年 | 3232篇 |
2002年 | 2787篇 |
2001年 | 2479篇 |
2000年 | 2320篇 |
1999年 | 2150篇 |
1998年 | 1815篇 |
1997年 | 1681篇 |
1996年 | 1481篇 |
1995年 | 1252篇 |
1994年 | 1274篇 |
1993年 | 1053篇 |
1992年 | 826篇 |
1991年 | 588篇 |
1990年 | 496篇 |
1989年 | 415篇 |
1988年 | 294篇 |
1987年 | 198篇 |
1986年 | 128篇 |
1985年 | 84篇 |
1984年 | 36篇 |
1983年 | 31篇 |
1982年 | 31篇 |
1981年 | 20篇 |
1980年 | 23篇 |
1979年 | 30篇 |
1978年 | 36篇 |
1977年 | 24篇 |
1975年 | 4篇 |
1954年 | 17篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
961.
962.
963.
964.
965.
在工作程度高的地区如何筛选矿致磁异常 总被引:1,自引:0,他引:1
分析了在工作程度高的地区进一步筛选矿致磁异常的可能性;提出了在工作程度高的地区筛选矿致磁异常的优先顺序建议。 相似文献
966.
967.
我国西部特殊景观区化探方法研究进展 总被引:5,自引:2,他引:3
西部特殊景观区的化探方法研究一直是中国化探界的一个研究热点和难点.在岩石出露、水系发育地区可以沿用传统的水系沉积物化探方法,但在覆盖景观区,常规化探方法效果并不理想.目前,谢学锦和王学求所提出的深穿透地球化学方法,经过一系列的实验研究,证明其能在覆盖区达到快速有效地圈定战略靶区的作用,具有广泛的应用前景.要做好西部特殊景观区的化探工作,化探科研人员必需采取新方法、新思路,继续系统地开展化探方法技术研究,通过不懈的努力最终找到一套适合中国西部特殊景观区特别是覆盖区的行之有效的化探方法. 相似文献
968.
Studies on rain-runoff process in the peripheral mountainous area of the Sichuan Basin, which is regarded as a key ecological shelter, will contribute to flood control and environmental protection for the Upper Yangtze River Basin. In two typical catchments--the Fujiang River Catchment and the Wujiang River Catchment, rainfall simulations have been conducted to study the rain-runoff processes of yellow soil and limestone soil in three types of land use--forestland, farmland and grassland. Results showed that (1) within the same rainfall process, overland flow occurs first on farmland, then on grassland, and finally on forestland; (2) soil surface coverage has a great impact on the occurrence and amount of overland flow. The runoff amount can increase 2-4 times after the coverage is removed; (3) the infiltration before the occurrence of overland flow will decrease because of higher gravel contents of soil, but it takes no effect on infiltration once overland flow becomes stable; (4) the runoff coefficient of the limestone soil forestland is greater than that of the yellow soil forest land, but less than that of the farmland; (5) three empirical infiltration models, including Horton' model, Kostiakov' model, and modified Kostiakov' model, were compared by using the observed results under rainfall simulation. The results showed that the Kostiakov' model performed better than both the Horton' model and modified Kostiakov model. According to the results of this research, the Kostiakov's model can be used to simulate rainfall infiltration when water erosion is modeled in the peripheral mountainous area of the Sichuan Basin. 相似文献
969.
Geochemical characteristics and source analysis of inflow of mine water in Wang’ershan Gold Mine, Shandong 总被引:1,自引:0,他引:1
QIAN Jianping LI Shuangli and CAO Chao Guilin University of Technology Guilin China 《中国地球化学学报》2008,(1)
Through a systematic observation of water level and temperature, and a comprehensive analysis of the data on major/trace elements, nitrite, hydrogen-oxygen isotopes, the conclusion has been drawn that there are two relatively independent groundwater systems (cool water and hot water), and the geochemical indicators of hot/cool waters are described. The cool water system is relatively enriched in Ca2 , Mg2 and HCO3-. Its TDS is relatively low, about 1400–1800 mg/L. The hot water system is relatively enriched in K , Na , Cl- and SO42-. Its TDS is relatively high, about 2200–2300 mg/L. The cool water system is enriched in Ba, Ga, Cd, and the hot water system is enriched in B, Ti, Cr, Ni, Cu, Mo, Rb, and Cs, relatively. Especially, the contents of Rb and Cs in the hot water system are more than five times as high as those in the cool water system. The NO3- contents of cool water discharged from the gold mine are relatively high, and those of hot water are extremely low. The δD and δ18O values follow an increasing order of surface water>mine cool water>mine hot water. The cool water comes mainly from the lateral supply of phreatic water, while the hot water comes mainly from the vertical supply of deeply circulating structure-fracture water. The ratio of cool water over hot water was estimated to be about 1:1 by a water quality model.. 相似文献
970.
Baode Wang Shuyin Niu Aiqun Sun Huabin Hu Yaming Liu Lijun Guo Shuo Wang 《中国地球化学学报》2008,27(3):235-241
In recent years big strides have been made in the exploration of ores in the central-south segment of the Da Hinggan Ling Range, though some debates still exist on the metallogenesis and sources of ore-forming materials. Pyrite and other sulfides in direct relation to the Pb-Zn-Ag ore deposits were chosen for the He and Ar isotopic analysis of ore-forming fluids, and the first He and Ar isotope data have been obtained from the study region. ^3He/^4He ratios in 14 samples collected from 7 mining districts are 2.17×10^-6-12.52×10^-6, averaging 6.86×10^-6 and their R/Ra ratios are 1.56-9.01 Ra, averaging 4.37 Ra. By projecting the data points onto the ^3He-^4He concentrations diagram, all the points fall near the mantle helium area. The calculated mantle-source helium ratios are within the range of 19.58%-76.96%, with an average of 49.52%. Argon isotopic characteristics are close to those of mantle source, indicating that the ore-forming material was transport upwards via the multi-stage evolution of mantle plume and concentrated as ores in the favorable loci of mantle branch structures. 相似文献