全文获取类型
收费全文 | 1183篇 |
免费 | 119篇 |
国内免费 | 270篇 |
专业分类
测绘学 | 82篇 |
大气科学 | 121篇 |
地球物理 | 467篇 |
地质学 | 596篇 |
海洋学 | 123篇 |
天文学 | 41篇 |
综合类 | 40篇 |
自然地理 | 102篇 |
出版年
2022年 | 14篇 |
2021年 | 11篇 |
2020年 | 9篇 |
2019年 | 11篇 |
2018年 | 19篇 |
2016年 | 15篇 |
2015年 | 12篇 |
2014年 | 23篇 |
2013年 | 21篇 |
2012年 | 55篇 |
2011年 | 66篇 |
2010年 | 18篇 |
2009年 | 29篇 |
2008年 | 51篇 |
2007年 | 51篇 |
2006年 | 71篇 |
2005年 | 56篇 |
2004年 | 55篇 |
2003年 | 36篇 |
2002年 | 58篇 |
2001年 | 44篇 |
2000年 | 59篇 |
1999年 | 22篇 |
1998年 | 27篇 |
1997年 | 28篇 |
1996年 | 24篇 |
1995年 | 42篇 |
1994年 | 42篇 |
1993年 | 45篇 |
1992年 | 36篇 |
1991年 | 56篇 |
1990年 | 51篇 |
1989年 | 45篇 |
1988年 | 43篇 |
1987年 | 32篇 |
1986年 | 29篇 |
1985年 | 29篇 |
1984年 | 23篇 |
1983年 | 29篇 |
1982年 | 13篇 |
1981年 | 7篇 |
1980年 | 18篇 |
1965年 | 8篇 |
1964年 | 8篇 |
1959年 | 9篇 |
1958年 | 19篇 |
1957年 | 14篇 |
1955年 | 6篇 |
1954年 | 8篇 |
1930年 | 6篇 |
排序方式: 共有1572条查询结果,搜索用时 808 毫秒
861.
地震是破坏性很大的自然灾害,世界上没有一个地方比中国和东亚沿海地区经历过更多的地震。同样的,干旱、洪水以及其它气候灾害也是世界上屡见不鲜的事件。本文提出了将这两种地球物理现象联系起来的理论。 早在80年代初期,便已提出气候变化的决定性的分析模式。该模式与古气候时间序列相符合,并可用于预报,它成功地经受过几年的检验。早先对该模式在地质时标上的核实,在这里我们将之延伸到近代历史。并且根据万有引力常数(G)随时间变化的可能性提出了关于气候变化原因的解释。G的变化意味着构造活动性(如地震)与气候特性(如由模式所表示的全球温度变化)的同步变化。因此,该模式也为地震预报提供了希望。 作者提出了解释在某一时间段内不同地区地震活动性的交替的理论。该理论通过对中国廿世纪发生的里克特震级大于或等于6的许多地震的检验。在小比例尺地形制图精度以及在震中定位的低灵敏度范围内,所获结果是令人鼓舞的 相似文献
863.
864.
Short-termClimaticFluctuationsinNorthAtlanticOscillationandFrequencyofCyclonicDisturbancesoverNorthIndianOceanandNorthwestPac... 相似文献
865.
由于采用了微计算机,可以使早期型号的波长色散 X 射线荧光谱仪廉价地配备上计算机的能力。微计算机比小型计算机的主要优点是价格低,而主要缺点是运算速度较慢。我们已经发现 APPLEⅡPLUS 微计算机能够完成以前一台较大且贵得多的小型计算机所承担的全部任务。由于微计算机用作实验室的计算机见效快、易于维修,程序灵活,所以使它成为一种有吸引力的选择对象。基体效应校正程序 XRF-4已用于微计算机,且得到极好的效果。 相似文献
866.
一、引言美国国家气象中心(NMC)于1980年8月12日开始使用谱模式,结束了舒曼(Shuman)和赫韦曼尔(Hovermale)于1968年提出的、长期以来较受重视的原始方程(PE)模式。这个新的谱模式是1980年由 Sala 提出的。本文并不涉及谱模式本身的详细情况,只对它作简单的描述。 相似文献
867.
Variations in Typhoon Landfalls over China 总被引:1,自引:1,他引:1
Emily A. FOGARTY James B. ELSNER Thomas H. JAGGER Kam-biu LIU Kin-sheun LOUIE 《大气科学进展》2006,23(5):665-677
The interannual variability in typhoon landfalls over China is investigated using historical and modern records. For the purpose of substantiating and elaborating upon the claim of north to south variation in tropical cyclone activity over China, a north-to-south anti-correlation in yearly activity is confirmed in the historical cyclone records. When cyclone activity over the province of Guangdong is high (low), it tends to be low (high) over the province of Fujian. A similar spatial variation is identified in the modern records using a factor analysis model, which delineates typhoon activity over the southern provinces of Guangdong and Hainan from the activity over the northern provinces of Fujian, Taiwan, Zhejiang, Shanghai, Jiangsu, and Shandong. A landfall index of typhoon activity representing the degree to which each year follows this pattern of activity is used to identify correlated climate variables. A useful statistical regression model that includes sea-level pressure differences between Mongolia and western China and sea-surface temperature (SST) over the northwestern Pacific Ocean during the summer explains 26% of the interannual variability of the landfall index. It is suggested that a stronger than normal north-south pressure gradient increases the surface easterly wind flow over northern China: this, coupled with lower SST over the Pacific, favors typhoons taking a more westerly track toward southern China. 相似文献
868.
Daishe WU Baoshan ZHENG Xiuyi TANG Mingshi WANG Jun HU Shehong LI Binbin WANG Robert B. Finkelman 《中国地球化学学报》2006,25(B08):54-54
Three hundred and six coal samples were taken from the main coal mines of twenty-six provinces, autonomous regions, and municipalities of China. The method of Kjeldahl-Gunning Analysis was used to measure the nitrogen contents in the samples. Nitrogen in coals is principally of organic nature. A weak positive correlation between coal rank and nitrogen content is inferred in the study. The distribution of nitrogen in each geological age, coal-cumulating area and province's coals was studied. The contents of nitrogen in Chinese coals show approximately a normal distribution, and 90% of the values range from 0.52% to 1.41%, the average nitrogen content in Chinese coals is designated as the arithmetic mean, 0.98%. 相似文献
869.
John G. Farmer Joanna M. Cloy Margaret C. Graham Angus B. MacKenzie Gordon T. Cook 《中国地球化学学报》2006,25(B08):68-69
Antimony has long been recognized as a non-essential, potentially toxic element. It has recently been suggested, on the basis of measured elemental profiles in peat bogs, that natural levels of Sb in the environment have been overestimated by a factor of 10 and that anthropogenic Sb deposition from the atmosphere has closely followed that of Pb. The implication is that the health effects of environmental Sb may have been seriously underestimated. To examine these propositions, we have compared new data for Sb and Pb in dated cores from four Scottish ombrotrophic peat bogs, Carsegowan Moss, Flanders Moss, Red Moss of Balerno and Turclossie Moss, in southwest, west-central, east-central and northeast Scotland, respectively. Dried peat sections, 1 to 2 cm thick, were subjected to microwave-assisted digestion in nitric/hydrofluoric acid and subsequently analyzed for a range of elements (including Sb, Pb, and the conservative elements Sc, Ti) and Pb isotopic composition by ICP-OES and ICP-MS as appropriate. Three certified reference materials, including NIMT/UOE/FM/001 Peat, were used for quality control purposes. Radiometric dating of upper and lower sections of the cores was carried out using gamma spectrometry for ^21-Pb and accelerator mass spectrometry for ^14C, respectively Some 2000 years ago, in Roman times, both Sb and Pb were clearly elevated in Scottish peat but typically at concentrations below 0.1 mg/kg and 5 mg/kg, respectively, with an average anthropogenic Sb/Pb ratio of-0.01. 相似文献
870.
Baoshan ZHENG Daishe WU Binbin WANG Mingshi WANG Xiaojing LIU Aimin WANG Guisen XIAO Pugao LIU Robert B. Finkelman 《中国地球化学学报》2006,25(B08):79-80
Indoor coal-combustion type fluorosis is the only type of endemic disease that still lacks effective method of prevention and control. By the end of 2000, there had been 33901 thousand peoples living in the indoor coal-combustion-type fluorosis area, including 17695 thousand patients of dental fluorosis, and 1465 thousand patients with skeletal fluorosis. Guizhou is the province that suffers mostly from indoor coal-combustion-type fluorosis. 28.11% of the total population of Guizhou Province, 14489 thousand peoples, including 9910 thousand dental fluorosis patients, are living in indoor coal-combustion-type fluorosis area in Guizhou Province (NSB, 2000). During the period of 1980-1984, the following results were proved by authors : (1) there is no positive relationship between fluorine concentrations in foodstuff and in soils and rocks; (2) absorbed fluorine from indoor combustion formed high fluorine content foodstuffs. Fluorine emitted from combustion was acid-soluble fluorine; and (3) of the two factors that induced fluorosis, 相似文献