全文获取类型
收费全文 | 360篇 |
免费 | 55篇 |
国内免费 | 67篇 |
专业分类
测绘学 | 31篇 |
大气科学 | 55篇 |
地球物理 | 58篇 |
地质学 | 92篇 |
海洋学 | 147篇 |
综合类 | 48篇 |
自然地理 | 51篇 |
出版年
2024年 | 2篇 |
2023年 | 8篇 |
2022年 | 13篇 |
2021年 | 13篇 |
2020年 | 12篇 |
2019年 | 14篇 |
2018年 | 5篇 |
2017年 | 12篇 |
2016年 | 9篇 |
2015年 | 8篇 |
2014年 | 26篇 |
2013年 | 16篇 |
2012年 | 14篇 |
2011年 | 12篇 |
2010年 | 33篇 |
2009年 | 13篇 |
2008年 | 18篇 |
2007年 | 32篇 |
2006年 | 24篇 |
2005年 | 23篇 |
2004年 | 17篇 |
2003年 | 22篇 |
2002年 | 13篇 |
2001年 | 13篇 |
2000年 | 16篇 |
1999年 | 16篇 |
1998年 | 13篇 |
1997年 | 11篇 |
1996年 | 4篇 |
1995年 | 18篇 |
1994年 | 6篇 |
1993年 | 9篇 |
1992年 | 6篇 |
1991年 | 4篇 |
1990年 | 3篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1983年 | 1篇 |
排序方式: 共有482条查询结果,搜索用时 296 毫秒
371.
易秀 《地球科学与环境学报》2000,22(4)
总结了硒的来源及在环境介质中的分布特点 ;讨论了硒的形态及影响其生物有效性的因素、硒的生物地球化学循环 ;分析了硒与地方病的关系以及它在生态环境中所起的重要作用 相似文献
372.
文章首先简要叙述探地雷达的工作方法和技术特点,介绍了探地雷达图像的分析处理过程(编辑标记、地形高程改正、距离修正、去除干扰信号和进行数字信号处理等),重点研究了道路路基存在较大空洞和不规则孔洞、地层软弱区、地层松散区、雨水或者地下水入侵路基层、路基产生沉陷、断层或裂缝等主要病害的探地雷达图像特征.文章还列举了两个应用工程实例,并论述了探地雷达在道路路基病害探测中应用的可行性和优越性. 相似文献
373.
一株引起凡纳滨对虾红体病的病原菌--副溶血弧菌的初步研究 总被引:9,自引:0,他引:9
从2001年7月辽宁省盘锦市大洼对虾养殖厂大面积暴发红体病(全身发红,活动减弱,食欲减退,壳变硬,死亡率高)的凡纳滨对虾(Litopenaeus vannamei)肌肉组织中分离到3株优势菌,经回归感染证实其中一株为引发本次凡纳滨对虾红体病的病原菌,编号为0107。对该菌进行了生理生化鉴定和16S rRNA基因序列同源性分析,将其判定为副溶血弧菌(Vibrio parahaemolyticus)。药敏实验结果显示,该菌对头孢哌酮、头孢曲松等多种抗生素敏感,对氨苄西林、青霉素等抗生素不敏感。 相似文献
374.
地下淡水演变与水致疾病 总被引:10,自引:0,他引:10
地下淡水是地球水圈中罕见的自然资源和敏感脆弱的环境要素,地下淡水演变与人类生存息息相关。地下淡水最严重的演变是其中N-浓度的持续增高,浅层地下水成为大陆氮的贮存库。许多环境是水致疾病。水致疾病的分布受水文地球化学分带控制。在氧化带易发生碘缺乏病,在还原带易发生氟中毒病,在富有机质和H2S的潮湿地带易发生克山病。 相似文献
375.
376.
健康已成为人类普遍关注的问题,以人类健康为研究对象的医学地理目前正成为全球性的研究热点,其中疾病地理又是相对成熟的分支和主要的研究方向.空间分析方法的引入,开拓了疾病地理研究的新领域,也成为疾病监测和评估的一个辅助工具,这使得疾病时空研究取得了重大进展.本文在前人研究的基础上,从时空两方面揭示了疾病地理近年来主要的研究动态和特点,并提出了当前疾病地理研究的某些不足,最后展望了今后我国疾病地理的研究任务和方向. 相似文献
377.
An open reading frame (lcn61) of iymphocystis disease virus China (LCDV-cn), probably responsible for encoding putative zinc-finger proteins was amplified and inserted into pET24a (+) vector.Then it expressed in E. coli BL21 (DE3), and His-tag fusion protein of high yield was obtained. It was found that the fusion protein existed in E. coli mainly as inclusion bodies. The bioinformatics analysis indicates that LCN61 is C2H2 type zinc-finger protein containing four C2H2 zinc-finger motifs. This work provides a theory for functional research of lcn61 gene. 相似文献
378.
Acidic oligosaccharide sugar chain (AOSC), a D-mannuronic acid oligosaccharide, derived from brownalgaepolysaccharide, has been completed Phase I clinical trial in China as an anti-Alzheimer's Disease (AD) drug candidate. The identification of AOSC-binding protein(s) in neurons is very important for understanding its action mechanism. To determine the binding protein(s) of AOSC in neurons mediating its anti-AD activities, confocal microscopy, affinity chromatography, and liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis were used. Confocal microscopy analysis shows that AOSC binds to SH-SY5Y cells in concentration-, time-, and temperature-dependent fashions. The AOSC binding proteins were purified by affinity chromatography and identified by LC-MS/MS analysis. The results showed that there are 349 proteins binding AOSC, including clathrin, adaptor protein-2 (AP-2) and amyloid precursor protein (APP). These results suggest that the binding/entrance of AOSC to neurons is probably responsible for anti-AD activities. 相似文献
379.
Detection of stress in tomatoes induced by late blight disease in California, USA, using hyperspectral remote sensing 总被引:4,自引:0,他引:4
Minghua Zhang Zhihao Qin Xue Liu Susan L. Ustin 《International Journal of Applied Earth Observation and Geoinformation》2003,4(4):295-310
Large-scale farming of agricultural crops requires on-time detection of diseases for pest management. Hyperspectral remote sensing data taken from low-altitude flights usually have high spectral and spatial resolutions, which can be very useful in detecting stress in green vegetation. In this study, we used late blight in tomatoes to illustrate the capability of applying hyperspectral remote sensing to monitor crop disease in the field scale and to develop the methodologies for the purpose. A series of field experiments was conducted to collect the canopy spectral reflectance of tomato plants in a diseased tomato field in Salinas Valley of California. The disease severity varied from stage 1 (the light symptom), to stage 4 (the sever damage). The economic damage of the crop caused by the disease is around the disease stage 3. An airborne visible infrared imaging spectrometer (AVIRIS) image with 224 bands within the wavelength range of 0.4–2.5 μm was acquired during the growing season when the field data were collected. The spectral reflectance of the field samples indicated that the near infrared (NIR) region, especially 0.7–1.3 μm, was much more valuable than the visible range to detect crop disease. The difference of spectral reflectance in visible range between health plants and the infected ones at stage 3 was only 1.19%, while the difference in the NIR region was high, 10%. We developed an approach including the minimum noise fraction (MNF) transformation, multi-dimensional visualization, pure pixels endmember selection and spectral angle mapping (SAM) to process the hyperspectral image for identification of diseased tomato plants. The results of MNF transformation indicated that the first 28 eigenimages contain useful information for classification of the pixels and the rest were mainly noise-dominated due to their low eigenvalues that had few signals. Therefore, the 28 signal eigenimages were used to generate a multi-dimensional visualization space for endmember spectra selection and SAM. Classification with the SAM technique of plants’ spectra showed that the late blight diseased tomatoes at stage 3 or above could be separated from the healthy plants while the less infected plants (at stage 1 or 2) were difficult to separate from the healthy plants. The results of the image analysis were consistent with the field spectra. The mapped disease distribution at stage 3 or above from the image showed an accurate conformation of late blight occurrence in the field. This result not only confirmed the capability of hyperspectral remote sensing in detecting crop disease for precision disease management in the real world, but also demonstrated that the spectra-based classification approach is an applicable method to crop disease identification. 相似文献
380.