全文获取类型
| 收费全文 | 6065篇 |
| 免费 | 1323篇 |
| 国内免费 | 1754篇 |
专业分类
| 测绘学 | 754篇 |
| 大气科学 | 882篇 |
| 地球物理 | 1354篇 |
| 地质学 | 3497篇 |
| 海洋学 | 967篇 |
| 天文学 | 263篇 |
| 综合类 | 645篇 |
| 自然地理 | 780篇 |
出版年
| 2024年 | 44篇 |
| 2023年 | 132篇 |
| 2022年 | 429篇 |
| 2021年 | 465篇 |
| 2020年 | 389篇 |
| 2019年 | 423篇 |
| 2018年 | 461篇 |
| 2017年 | 405篇 |
| 2016年 | 477篇 |
| 2015年 | 428篇 |
| 2014年 | 457篇 |
| 2013年 | 485篇 |
| 2012年 | 464篇 |
| 2011年 | 445篇 |
| 2010年 | 434篇 |
| 2009年 | 376篇 |
| 2008年 | 331篇 |
| 2007年 | 299篇 |
| 2006年 | 307篇 |
| 2005年 | 217篇 |
| 2004年 | 159篇 |
| 2003年 | 141篇 |
| 2002年 | 125篇 |
| 2001年 | 119篇 |
| 2000年 | 116篇 |
| 1999年 | 165篇 |
| 1998年 | 111篇 |
| 1997年 | 110篇 |
| 1996年 | 90篇 |
| 1995年 | 91篇 |
| 1994年 | 78篇 |
| 1993年 | 73篇 |
| 1992年 | 56篇 |
| 1991年 | 39篇 |
| 1990年 | 33篇 |
| 1989年 | 38篇 |
| 1988年 | 18篇 |
| 1987年 | 18篇 |
| 1986年 | 26篇 |
| 1985年 | 23篇 |
| 1984年 | 6篇 |
| 1983年 | 8篇 |
| 1982年 | 7篇 |
| 1980年 | 7篇 |
| 1979年 | 5篇 |
| 1978年 | 3篇 |
| 1965年 | 2篇 |
| 1958年 | 3篇 |
| 1957年 | 1篇 |
| 1954年 | 2篇 |
排序方式： 共有9142条查询结果，搜索用时 15 毫秒
191.
192.
193.
194.
195.
196.
197.
Based upon 1:200,000 regional gravity and aeromagnetic data, gravity and aeromagnetic slice maps were obtained through fast Fourier transformation (FFT) upward continuation. A comparison between gravity and aeromagnetic slice maps at different depths combined with regional geological data and Magneto-Telluric sounding reveals the deep geological structure of Benxi-Huanren area and provides important information for study of the deep geological evolution process of Benxi-Huanren area. Yanshanian granitic pluton is widely distributed in this area and tends to be continuous toward depth. Significant metallogenic areas, such as Dataigou and Nanfen areas, lie above the buried granitic pluton. The Paleoproterozoic strata distribution area and the Archean strata distribution area have similar characteristics in terms of gravity anomaly. The iron-bearing formation in Anshan area is Archean supracrustal rock which was not engulfed by Archean granite. The thickness of Liaoji paleo-rift can be up to 10 km, whose lower part was intruded by Yanshanian granites. The basement of the Liaoji rift was remelted during granite intrusion in Yanshanian period. 相似文献
198.
2013年1月29日至3月15日在台湾海峡西南部海域进行了OSMAR-S100便携式高频地波雷达与浮标观测海流数据的长周期对比试验,验证了雷达系统在探测海流方面的准确性、可靠性和稳定性.通过实测海流与雷达矢量流的复相关分析,选定3 m层的海流为对比代表层.试验期间实测流速为0.0~120.0 cm/s,雷达海流有效探测区内的矢量流流速、流向的观测误差较小,能够满足实时监测海洋表层流的需要,高精度区流速、流向的均方根误差分别为9.1 cm/s和24.8°,边缘区的均方根误差为13.3~24.8 cm/s和39.4°~39.6°,与国内外达到业务化运行要求的同类产品实际观测精度相当. 相似文献
199.
The culture of Sertoli cells has become an indispensable resource in studying spermatogenesis. A new Sertoli cell line (POSC) that consisted predominantly of fibroblast-like cells was derived from the testis of the olive flounder Paralichthys olivaceus and sub-cultured for 48 passages. Analysis of the mtDNA COI gene partial sequence confirmed that the cell line was from P. olivaceus. Cells were optimally maintained at 25°C in DMEM/F12 medium supplemented with fetal bovine serum, basic fibroblast growth factor, and epidermal growth factor. The growth curve of POSC showed a typical “S” shape. Chromosome analysis revealed that the cell line possessed the normal P. olivaceus diploid karyotype of 2n=48t. POSC expressed dmrt1 but not vasa, which was detected using RT-PCR and sequencing. Immunocytochemistry revealed that the cells exhibited the testicular Sertoli cell marker FasL. Therefore, POSC appeared to consist of testicular Sertoli cells. Bright fluorescent signals were observed after the cells were transfected with pEGFP-N3 plasmid, with the transfection efficiency reaching 10%. This research not only offers an ideal model for further gene expression and regulation studies on P. olivaceus, but also serves as valuable material in studying fish spermatogenesis, Sertoli cell-germ cell interactions, and the mechanism of growth and development of testis. 相似文献
200.
Herbaceous plants are widely distributed on islands and where they exhibit spatial heterogeneity. Accurately identifying the impact factors that drive spatial heterogeneity can reveal typical island biodiversity patterns. Five southern islands in the Miaodao Archipelago, North China were studied herein. The spatial distribution of herbaceous plant diversity on these islands was analyzed, and the impact factors and their degree of impact on spatial heterogeneity were identified using CCA ordination and ANOVA. The results reveal 114 herbaceous plant species, belonging to 94 genera from 34 families in the 50 plots sampled. The total species numbers on different islands were significantly positively correlated with island area, and the average α diversity was correlated with human activities, while the β diversity among islands was more affected by island area than mutual distances. Spatial heterogeneity within islands indicated that the diversities were generally high in areas with higher altitude, slope, total nitrogen, total carbon, and canopy density, and lower moisture content, pH, total phosphorus, total potassium, and aspect. Among the environmental factors, pH, canopy density, total K, total P, moisture content, altitude, and slope had significant gross effects, but only canopy density exhibited a significant net effect. Terrain affected diversity by restricting plantation, plantation in turn influenced soil properties and the two together affected diversity. Therefore, plantation was ultimately the fundamental driving factor for spatial heterogeneity in herbaceous plant diversity on the five islands. 相似文献