全文获取类型
收费全文 | 1984篇 |
免费 | 456篇 |
国内免费 | 573篇 |
专业分类
测绘学 | 184篇 |
大气科学 | 254篇 |
地球物理 | 597篇 |
地质学 | 1206篇 |
海洋学 | 381篇 |
天文学 | 19篇 |
综合类 | 143篇 |
自然地理 | 229篇 |
出版年
2024年 | 6篇 |
2023年 | 32篇 |
2022年 | 67篇 |
2021年 | 82篇 |
2020年 | 94篇 |
2019年 | 87篇 |
2018年 | 84篇 |
2017年 | 95篇 |
2016年 | 107篇 |
2015年 | 118篇 |
2014年 | 145篇 |
2013年 | 190篇 |
2012年 | 134篇 |
2011年 | 152篇 |
2010年 | 133篇 |
2009年 | 148篇 |
2008年 | 157篇 |
2007年 | 152篇 |
2006年 | 144篇 |
2005年 | 111篇 |
2004年 | 119篇 |
2003年 | 108篇 |
2002年 | 51篇 |
2001年 | 61篇 |
2000年 | 64篇 |
1999年 | 37篇 |
1998年 | 44篇 |
1997年 | 30篇 |
1996年 | 29篇 |
1995年 | 28篇 |
1994年 | 39篇 |
1993年 | 32篇 |
1992年 | 22篇 |
1991年 | 19篇 |
1990年 | 17篇 |
1989年 | 13篇 |
1988年 | 12篇 |
1987年 | 10篇 |
1986年 | 3篇 |
1985年 | 8篇 |
1984年 | 2篇 |
1983年 | 2篇 |
1982年 | 6篇 |
1981年 | 2篇 |
1980年 | 4篇 |
1979年 | 2篇 |
1978年 | 2篇 |
1977年 | 2篇 |
1972年 | 3篇 |
1971年 | 3篇 |
排序方式: 共有3013条查询结果,搜索用时 15 毫秒
81.
82.
拖曳式多参数剖面测量系统水动力与控制性能研究述评 总被引:11,自引:1,他引:11
综述了拖曳式多参数剖面测量系统水动力学研究的最新进展。对拖曳缆绳、拖曳体以及将两者耦合起来所构成的整个系统水动力及控制理论进行述评,分析了各种理论的优缺点从中简要地描述了拖曳式多参数剖面测量系统水动力研究的发展概要。 相似文献
83.
84.
K. Nagendra Prasad S. Triveni T. Schanz Late T. S. Nagaraj 《Marine Georesources & Geotechnology》2007,25(3):181-197
Despite the sophisticated methods employed to obtain high quality samples, they are prone to disturbance, due to stress release, let apart, due to sampling tools and techniques adopted. Critical reappraisal of different methods suggest that any method of sample quality assessment involving strength and deformation parameters would enable easier implementation and correct other engineering parameters for estimated sample disturbance. In this technical paper, sample disturbance index, using merely the slopes of compression paths, (representing mechanical response), in the pre- and post-yield stress regimes under odeometric loading conditions is proposed. This method is based on single oedometer test results on samples of unknown degrees of disturbance during sampling and handling. The unique feature of this approach is that the ideal rigid plastic material behavior is taken as reference. This eliminates the need for any additional experimental data or any calculations from the relationships formulated with any set of assumptions. 相似文献
85.
86.
87.
Solić M Krstulović N Vilibić I Kuspilić G Sestanović S Santić D Ordulj M 《Marine environmental research》2008,65(5):388-404
Month-to-month fluctuations in the abundance of bacteria and heterotrophic nanoflagellates (HNF) and bacterial production, as well as various chemical (nutrients, oxygen) and physical (salinity, temperature) parameters were analysed at a station located in the open middle Adriatic Sea during one decade (1997-2006). Being influenced by both coastal waters and open Adriatic circulation in the surface layer, and by the deep Adriatic water masses in the deep layers (100 m), this station is quite suitable for detecting the environmental changes occurring in the open Adriatic Sea with respect to the circulation of its water masses and their long-term changes and anomalies. Multivariate methods were used to identify seasonal and inter-annual changes of the investigated parameters, associating observed changes to the changes in Adriatic water masses and circulation regimes. The analyses showed that bacterial abundance and production were controlled by different water mass dynamics during 1997-2001 compared to 2002-2006 period, particularly noticeable in different seasonal patterns of biological parameters. The interplay between North Adriatic Dense Water (NAdDW) and Levantine Intermediate Water (LIW) resulted in a change in the available nutrients (NAdDW is poor in orthophosphates), and as a consequence different bacterial abundance and production. A few periods were examined in detail, such as 2004, when LIW inflow was particularly strong and was accompanied by an increase of bacterial and HNF abundances, as well as of bacterial production. 相似文献
88.
Long-term effects of a toxic algal bloom on subtidal soft-sediment macroinvertebrate communities in Wellington Harbour, New Zealand 总被引:2,自引:1,他引:2
Kerstin Krger Jonathan P.A. Gardner Ashley A. Rowden Robert G. Wear 《Estuarine, Coastal and Shelf Science》2006,67(4):589-604
The long-term effects (>1 year) of a naturally occurring toxic plankton bloom (Karenia brevisulcata) on subtidal benthic macroinvertebrate communities were investigated in Wellington Harbour, a semi-enclosed temperate embayment in New Zealand. For 3 years communities were sampled at three different sites in the harbour. Analyses revealed that community recovery following the bloom was site-specific. Multivariate analyses indicated that at one site community composition was approaching recovery 3 years post-bloom. At the second site, a sequential recovery process was indicated, whereas at the third site the community composition oscillated from year to year, but did not show any signs of a sequential recovery process. The nature of the hydrodynamic regime was identified as a major factor influencing the observed recovery processes. Communities exposed to an active hydrodynamic regime were less affected by the bloom and differed little in their composition pre- and post-bloom, as they were naturally in a perpetual state of recovery as indicated by a dominance of r-selected species. The community at the hydrodynamically less active site was more affected by the bloom and exhibited temporal differences in composition consistent with successional models. Complete recovery to a pre-disturbance climax community dominated by K-selected species is likely to take 4–5 years, if not interrupted by other disturbances. Given the increased occurrence of harmful algal blooms worldwide, more monitoring and manipulative studies are needed to further evaluate the effects of such disturbances on macrobenthic communities. 相似文献
89.
90.
Sampling permeability from individual laminae in crossbedded rocks is very well possible by making use of a so-called probe permeameter. The methodology and calculation of permeabilities from the output of this instrument are fairly well-established. However, what is hardly established is a sampling strategy that guarantees adequate representation of permeability contrast between laminae. Especially so, because finer foreset and bottomset are difficult to sample, yet their permeabilities are critical to fluid flow through a crossbed. Therefore we propose to systematically sample laminae. To this end we suggest a sampling strategy that is adapted to the heterogeneity under study, namely to the thickness of the finer foreset. 相似文献