全文获取类型
收费全文 | 82170篇 |
免费 | 10804篇 |
国内免费 | 16323篇 |
专业分类
测绘学 | 8651篇 |
大气科学 | 7997篇 |
地球物理 | 16356篇 |
地质学 | 43704篇 |
海洋学 | 11619篇 |
天文学 | 9045篇 |
综合类 | 3565篇 |
自然地理 | 8360篇 |
出版年
2024年 | 570篇 |
2023年 | 1443篇 |
2022年 | 2943篇 |
2021年 | 3856篇 |
2020年 | 3134篇 |
2019年 | 3640篇 |
2018年 | 3653篇 |
2017年 | 3476篇 |
2016年 | 3803篇 |
2015年 | 3866篇 |
2014年 | 4155篇 |
2013年 | 5558篇 |
2012年 | 5267篇 |
2011年 | 5569篇 |
2010年 | 5296篇 |
2009年 | 5562篇 |
2008年 | 5231篇 |
2007年 | 5085篇 |
2006年 | 4891篇 |
2005年 | 3925篇 |
2004年 | 3192篇 |
2003年 | 2436篇 |
2002年 | 2557篇 |
2001年 | 2186篇 |
2000年 | 1903篇 |
1999年 | 1147篇 |
1998年 | 965篇 |
1997年 | 857篇 |
1996年 | 745篇 |
1995年 | 678篇 |
1994年 | 590篇 |
1993年 | 500篇 |
1992年 | 510篇 |
1991年 | 439篇 |
1990年 | 552篇 |
1989年 | 443篇 |
1988年 | 398篇 |
1987年 | 494篇 |
1986年 | 409篇 |
1985年 | 489篇 |
1984年 | 602篇 |
1983年 | 525篇 |
1982年 | 506篇 |
1981年 | 452篇 |
1980年 | 459篇 |
1979年 | 422篇 |
1978年 | 393篇 |
1977年 | 384篇 |
1974年 | 350篇 |
1973年 | 377篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
81.
东营城区高精度三维地震采集方法研究 总被引:3,自引:0,他引:3
根据东营城区内建筑物较多,环境干扰较大,地下构造复杂,断裂非常发育,目的层埋藏深,资料信噪比较低的特点,以地震老资料和钻井资料为基础,建立地震地质模型,利用射线追踪技术选取合适的观测系统参数。充分利用卫星数字地图,没计了灵活多变的观测系统,采用可控震源与炸药震源配合使用方法,及时对城区内地下面元的覆盖次数、方位角和炮检距的分布进行质量监控,利用现场处理系统对资料进行及时分析,提高了地震资料品质。所获得的东营城区高精度三维地震采集资料显示,其浅中层分辨率和中深层信噪比都有了明显改善,取得了良好的地质效果。 相似文献
82.
Environmental concern for the deep-sea ecosystem is increasing as contaminants, originating from anthropogenic activities, have been detected in deep-sea biota. However, little is known on the xenobiotics metabolising capability of deep-sea fauna. In this study, the deep-sea amphipod Eurythenes gryllus was selected as sentinel species to measure the total oxyradical scavenging capacity (TOSC). Individuals of E. gryllus were sampled at 2000 m depth in the Arctic Ocean. The TOSC assay was measured on the cytosolic fraction and the soluble fraction (3 kDa) of the digestive gland and on the cell-free haemolymph toward peroxyl, hydroxyl and peroxynitrite radicals according to the method of Winston et al. [Free Radical Biology and Medicine 24 (3) (1998) 480] and Regoli and Winston [Toxicology and Applied Pharmacology 156 (1999) 96]. These results provide the first baseline data set for total antioxidant capacity in a deep-sea amphipod. 相似文献
83.
84.
85.
86.
87.
Juvenile coho salmon, Onchorynchus kisutch, were exposed to 95mTc in both saltwater and freshwater to study the biokinetic behavior of this element in an anadromous fish. In freshwater, equilibrium whole-body concentration factors (CF5) ranged from 28 to 32 in two separate experiments, in sharp contrast to an equilibriumCF of < 5 in saltwater. While the uptake kinetics were unimodal in saltwater, in freshwater, biomodal uptake kinetics were observed.Technetium-95m retention was biphasic in freshwater depuration experiments, an initial rapid loss of 21% to 26% of the steady-state activity with an elimination half-life of 3 to 5 days was followed by a slower loss rate, with a whole-body elimination half-life ranging from 23 to 33 days. In saltwater, retention was monophasic with an elimination half-life of 5–16 days. Dramatic decreases in 95mTc body burdens when freshwater-labeled fish are transferred to Tc-labeled saltwater indicate that the changes in physiology accompanying saltwater acclimation lead to the loss of 95mTc. 相似文献
88.
Three data sets of suspensate concentrations, collected under different sampling plans, were analyzed to develop a minimal sampling period, consistent with a predetermined precision. Individual samples collected during any part of a given day were within ±50% of the daily average. In the main channel of the estuary, a monthly sampling scheme closely approximated a weekly pattern; however, seasonal sampling was unsatisfactory. Outside the main channel, weekly, monthly, and seasonal sampling patterns did not differ greatly. Variability in suspensate concentrations must be considered when calculating sediment flux in estuarine and coastal waters. 相似文献
89.
The wadic project: A comprehensive field evaluation of directional wave instrumentation 总被引:1,自引:0,他引:1
J. Allender T. Audunson S. F. Barstow S. Bjerken H. E. Krogstad P. Steinbakke L. Vartdal L. E. Borgman C. Graham 《Ocean Engineering》1989,16(5-6)
The results of a comprehensive field trial of nearly all commercially available directional wave measurement systems at the Edda field in the North Sea during winter 1985-86 are presented. The results summarize the accuracy of the principal engineering wave parameters from each system and the dependence on sea state. Limiting factors on system performance and operational problems are also included in the assessment. Overall experience has been good with systems utilizing widely different measurement principles returning consistent results. 相似文献
90.