全文获取类型
收费全文 | 886篇 |
免费 | 91篇 |
国内免费 | 401篇 |
专业分类
测绘学 | 55篇 |
大气科学 | 30篇 |
地球物理 | 104篇 |
地质学 | 515篇 |
海洋学 | 522篇 |
天文学 | 12篇 |
综合类 | 54篇 |
自然地理 | 86篇 |
出版年
2024年 | 9篇 |
2023年 | 10篇 |
2022年 | 29篇 |
2021年 | 37篇 |
2020年 | 45篇 |
2019年 | 39篇 |
2018年 | 27篇 |
2017年 | 29篇 |
2016年 | 36篇 |
2015年 | 34篇 |
2014年 | 45篇 |
2013年 | 67篇 |
2012年 | 62篇 |
2011年 | 78篇 |
2010年 | 56篇 |
2009年 | 69篇 |
2008年 | 72篇 |
2007年 | 79篇 |
2006年 | 78篇 |
2005年 | 58篇 |
2004年 | 64篇 |
2003年 | 41篇 |
2002年 | 46篇 |
2001年 | 43篇 |
2000年 | 30篇 |
1999年 | 19篇 |
1998年 | 32篇 |
1997年 | 22篇 |
1996年 | 17篇 |
1995年 | 11篇 |
1994年 | 16篇 |
1993年 | 15篇 |
1992年 | 22篇 |
1991年 | 10篇 |
1990年 | 8篇 |
1989年 | 2篇 |
1988年 | 6篇 |
1987年 | 3篇 |
1986年 | 3篇 |
1985年 | 1篇 |
1984年 | 2篇 |
1983年 | 5篇 |
1982年 | 1篇 |
排序方式: 共有1378条查询结果,搜索用时 515 毫秒
141.
Cd Te量子点具有荧光强度高和稳定性好的优点,应用Cd Te量子点荧光猝灭法分析基体复杂的样品,需要有效分离对测定干扰的金属元素和高效富集待测元素。本文以巯基乙酸(TGA)作稳定剂,采用水相合成法制备了巯基乙酸修饰的Cd Te量子点,基于镍离子在p H=10.0硼砂缓冲溶液中对Cd Te量子点的荧光具有较强猝灭作用,建立了一种测定赤泥中痕量镍的荧光光度方法。荧光猝灭反应的最佳实验条件为:Cd Te量子点的浓度3.0×10-4mol/L,反应温度为室温,反应时间10 min,在此条件下镍离子浓度在2.0×10-7~7.8×10-5mol/L范围内与Cd Te量子点的相对荧光强度呈良好的线性关系;方法检出限为1.5×10-7mol/L。本方法针对Fe3+、Co2+、Cu2+等主要基体金属元素允许量低的问题,采用25%的2-羟基-4-仲辛氧基二苯甲酮肟(N530)磺化煤油萃取回收滤液中的Ni2+,镍回收率达到99%以上;赤泥中痕量镍的测定结果与催化光度法相符,加标回收率为98.3%-104.2%。 相似文献
142.
143.
W. M. Davis E. R. Cespedes L. T. Lee J. F. Powell R. A. Goodson 《Environmental Geology》1997,29(3-4):228-237
The Site Characterization and Analysis Penetrometer System (SCAPS) was used to investigate subsurface petroleum contamination
at Aberdeen Proving Ground, Maryland. The SCAPS is a rapid site-screening tool developed by the Tri-Services (U.S. Army, Navy,
and Air Force) to reduce the cost of installation restoration activities. The system, consisting of a geophysical cone penetrometer
fitted with a laser-induced fluorescence petroleum sensor, is capable of simultaneous, real-time delineation of subsurface
stratigraphy and petroleum contamination. Onsite processing of the SCAPS data allows three-dimensional visualization of both
subsurface stratigraphy and petroleum contaminant distribution. The site investigation described herein successfully identified
three distinct areas of subsurface petroleum contamination caused by leaking underground storage tanks containing No. 2 healing
oil. The SCAPS petroleum sensor response was verified by obtaining 20 soil samples and performing onsite and conventional
laboratory analyses for petroleum contaminants. Verification sample results indicate a strong correlation between the SCAPS
fluorescence data and conventional measures of petroleum contamination. This investigation illustrates the capabilities of
the SCAPS for rapid site characterization.
Received: 27 November 1995 · Accepted: 11 December 1995 相似文献
144.
对应用荧光分光光度法测定海洋生物中还原型谷胱甘肽(GSH)含量的方法进行了研究,并测定了分属于鱼、虾、贝、藻的10种海洋生物中谷胱甘肽的含量。利用邻苯二甲醛与GSH反应构成的荧光体系,在激发波长为365nm,发射波长为425nm的条件下,方法的回收率为99.22%~99.69%,变异系数为2.16%。应用此方法测得10种海洋生物中谷胱甘肽的含量为:红笛鲷(Lutjanussanguineus)0.399mg/g,银鲳(Pampusargenteus)0.352mg/g,大海鲢(Megalopscyrinoides)0.561mg/g,尖紫蛤(Sanguinolariaacuta)0.289mg/g,菲律宾蛤仔(Ruditapesphilippinarun)0.287mg/g,墨吉对虾(Penaeusmerguiensis)0.892mg/g,凡纳滨对虾(Litopenaeusvannamei)1.434mg/g,囊藻(Colpomeniasinu-ose)0.221mg/g,石莼(Ulvalactucal)0.727mg/g,马尾藻(Sargassummuticum)0.137mg/g。 相似文献
145.
A.H. Dye 《Estuarine, Coastal and Shelf Science》1983,17(2):207-212
A simple and rapid method for the quantitative extraction of bacteria from high silt/clay-content muds associated with mangrove swamps is described. Mud samples are homogenized in filtered sea water and the supernatant is diluted and stained with Acridine Organge. The stained material is trapped on a 0·45 μm membrane filter and bacteria are counted under a fluorescence microscope. Samples may be pre-fixed in 5% formalin if they cannot be examined immediately. 相似文献
146.
拟定了用铅空心阴极灯为激发光源,氢化物原子荧光光度法测定地球化学样品中微量铅的方法。在2%HCl-0.08%K_3[Fe(CN)_6]-2%KBH_4体系中,铅的测定灵敏度有明显地提高。该方法操作简便、快速、准确,检出限为8.89×10~(-9)g/ml,精密度为4.12%(n=11)。 相似文献
147.
A Laser-induced Fluorescence Instrument for Detecting Tropospheric OH and HO2: Characteristics and Calibration 总被引:1,自引:0,他引:1
148.
Linda K. Ayliffe Michael I. Bird Michael K. Gagan Peter J. Isdale Heather Scott-Gagan Bruce Parker David Griffin Michael Nongkas Malcolm T. McCulloch 《Continental Shelf Research》2004,24(19):2343-2356
A Porites sp. coral growing offshore from the Sepik and Ramu Rivers in equatorial northern Papua New Guinea has yielded an accurate 20-year history (1977–1996) of sea surface temperature (SST), river discharge, and wind-induced mixing of the upper water column. Depressions in average SSTs of about 0.5–1.0 °C (indicated by coral Sr/Ca) and markedly diminished freshwater runoff to the coastal ocean (indicated by coral δ18O, δ13C and UV fluorescence) are evident during the El Niño – Southern Oscillation (ENSO) events of 1982–1983, 1987 and 1991-1993. The perturbations recorded by the coral are in good agreement with changes in instrumental SST and river discharge/precipitation records, which are known to be diagnostic of the response of the Pacific Warm Pool ocean–atmosphere system to El Niño. Consideration of coastal ocean dynamics indicates that the establishment of northwest monsoon winds promotes mixing of near-surface waters to greater depths in the first quarter of most years, making the coral record sensitive to changes in the Asian–Australian monsoon cycle. Sudden cooling of SSTs by 1°C following westerly wind episodes, as indicated by the coral Sr/Ca, is consistent with greater mixing in the upper water column at these times. Furthermore, the coral UV fluorescence and oxygen isotope data indicate minimal contribution of river runoff to surface ocean waters at the beginning of most years, during the time of maximum discharge. This abrupt shift in flood-plume behaviour appears to reflect the duration and magnitude of northwest monsoon winds, which tend to disperse flood plume waters to a greater extent in the water column when wind-mixing is enhanced. Our results suggest that a multi-proxy geochemical approach to the production of long coral records should provide comprehensive reconstructions of tropical paleoclimate processes operating on interannual timescales. 相似文献
149.
随着传感器技术的发展,高光谱数据光谱的波段宽度逐渐变窄,如何从海量的光谱数据中找到最优的光谱波段反演叶绿素含量,成为研究的难点问题。本文在测量华中农业大学狮子山6种主要树种的光谱数据和叶绿素含量的基础上,利用叶绿素指数(CI)和回归方法反演叶绿素含量,并分析了波段宽度对反演叶绿素含量结果的影响,结果发现波段宽度会影响到叶绿素反演的精度,当波段宽度为30nm时,叶绿素含量与"红边"区域(700nm-730nm)和近红外区域(770nm-800nm)叶绿素指标(CI)间的线性关系较好,决定系数可达到77.62%,均方根误差为10.6ug/cm2。 相似文献
150.