全文获取类型
收费全文 | 1316篇 |
免费 | 560篇 |
国内免费 | 151篇 |
专业分类
测绘学 | 129篇 |
大气科学 | 270篇 |
地球物理 | 275篇 |
地质学 | 727篇 |
海洋学 | 233篇 |
天文学 | 80篇 |
综合类 | 161篇 |
自然地理 | 152篇 |
出版年
2025年 | 3篇 |
2024年 | 46篇 |
2023年 | 47篇 |
2022年 | 74篇 |
2021年 | 76篇 |
2020年 | 59篇 |
2019年 | 63篇 |
2018年 | 74篇 |
2017年 | 79篇 |
2016年 | 56篇 |
2015年 | 82篇 |
2014年 | 75篇 |
2013年 | 68篇 |
2012年 | 72篇 |
2011年 | 77篇 |
2010年 | 77篇 |
2009年 | 78篇 |
2008年 | 62篇 |
2007年 | 58篇 |
2006年 | 58篇 |
2005年 | 51篇 |
2004年 | 58篇 |
2003年 | 56篇 |
2002年 | 71篇 |
2001年 | 89篇 |
2000年 | 49篇 |
1999年 | 63篇 |
1998年 | 36篇 |
1997年 | 34篇 |
1996年 | 38篇 |
1995年 | 36篇 |
1994年 | 37篇 |
1993年 | 24篇 |
1992年 | 20篇 |
1991年 | 14篇 |
1990年 | 21篇 |
1989年 | 12篇 |
1988年 | 12篇 |
1987年 | 11篇 |
1985年 | 5篇 |
1984年 | 1篇 |
1983年 | 2篇 |
1982年 | 2篇 |
1964年 | 1篇 |
排序方式: 共有2027条查询结果,搜索用时 24 毫秒
131.
Advances in the Study on Nutrient Requirements of Grouper(Epinephelus sp. ):a Review 总被引:1,自引:0,他引:1
LUOZhi LIUYongjian MAIKangsen TIANLixia 《中国海洋大学学报(英文版)》2005,4(2):93-98
The paper reviews the recent advances in studying grouper nutrition requirement for the development of cost-effective and environmentally friendly artificial diets. It consists of seven parts: protein and amino acid, lipid and essential fatty acid, carbohydrate, vitamin, mineral, alternative protein source, broodstock and larval nutrition. The review provides some basic information for further investigation of nutrient requirements of groupers. 相似文献
132.
133.
Hu-Chen Liu Jian-Xin You Yi-Zeng Chen Xiao-Jun Fan 《Environmental Earth Sciences》2014,72(10):4179-4189
Nowadays, selection of the suitable disposal site in municipal solid waste (MSW) management has become a challenge task for the municipal authorities, especially in fast-growing areas. Site selection can be viewed as a complicated multi-criteria decision-making (MCDM) problem requiring consideration of multiple alternative solutions and conflicting quantitative and qualitative criteria. In this paper, linguistic variables, which can be expressed as trapezoidal fuzzy numbers, are used to assess the ratings and weights for the selection criteria. The ordered weighted averaging operator is utilized to transform the fuzzy decision matrix into crisp values considering the decision maker’s attitudinal character. For selecting the best site, the extended VIsekriterijumska optimizacija i KOmpromisno Resenje (VIKOR) method is applied to determine the priority ranking of alternatives. As a result, a hierarchy MCDM model based on fuzzy set theory and VIKOR method is proposed to deal with the site selection problems in the MSW management system. An empirical study in Shanghai, China, is provided and comparison with the existing approach is conducted to illustrate the applicability and benefits of the proposed method. 相似文献
134.
S. A. Junejo Qi You Zhou M. A. Talpur Dongqing Wang Jian-long Yang 《Geochemistry International》2014,52(9):794-804
Accurate prediction of solute transport processes in surface water and its underlying bed is an important task not only for proper management of the surface water but also for pollution control in these water bodies. Key issue in this task is an estimation of parameters as diffusion coefficient and velocity for solute transport both in water body and in the underlying bed. This estimation would greatly help us to understand the deposition and release mechanism of solute across the water-bed interface. In this study, a column experiment was conducted in laboratory to estimate the velocity and diffusion coefficient of sodium chloride (NaCl) in water body and underlying sand layer (bed). The column used with a diameter of 30 cm and a height of 100 cm, was filled with sand at the lower half part and water at the upper half part. Total 64 stainless steel electrodes were installed on its surface around. The sodium chloride solution was injected from the top of the column, and electrical resistance between electrodes was monitored for 71 h. Then the dimensionless resistance breakthrough curve was fitted with one dimensional analytic solution for solute transport and the related diffusion coefficient and velocity parameters were estimated. The results show that the NaCl transport velocity was high in the water body but extremely low in the underlying sand layer (bed). The diffusion coefficient estimated in sand layer coincides with those reported well. This indicates that the electrical resistance based solute transport parameter estimation method is not only effective but also has an advantage of multipoints monitoring. This is useful both in mapping solute transport parameter for solute transport process analysis and in providing parameter input for solute transport numerical modeling. 相似文献
135.
针对Noah-MP模型多参数化方案、模拟结果不确定性范围难以确定的特点,选取北疆地区具有代表性的阿勒泰站气象资料作为模型驱动数据,探讨了积雪对多参数化方案的敏感性。在不考虑模型参数和驱动数据不确定性的条件下,设计了集合数为13824的多参数化方案集合模拟试验。选用Natural selection方法对物理过程的敏感性进行分析,并在敏感性分析结果的基础上进一步讨论了模拟结果的不确定性。结果表明:积雪对地表热交换、雨雪分离、土壤温度底层边界条件和第一层积雪或土壤时间方案4个物理过程敏感;在不考虑驱动数据和模型参数不确定性的条件下,多参数化方案集合模拟试验中的不确定性主要来源于敏感物理过程。去除敏感物理过程中能够明显降低模拟性能的参数化方案后,集合模拟结果的不确定性大幅减小。最后,根据分析结果构建了该站雪深和雪水当量模拟的最优参数化方案组合。 相似文献
136.
Sediment transport and overpressure generation are coupled primary through the impact of effective stress on subsidence and compaction. Here, we use mathematical modeling to explore the interactions between groundwater flow and diffusion-controlled sediment transport within alluvial basins. Because of lateral variation in permeability, proximal basin facies will have pore pressure close to hydrostatic levels while distal fine-grained facies can reach near lithostatic levels. Lateral variation in pore pressure leads to differential compaction, which deforms basins in several ways. Differential compaction reduces basin size, bends isochron surfaces across the sand–clay interface, restricts basinward progradation of sand facies, and reduces the amplitude of oscillation in the lateral position of the sand–clay interface especially in the deepest part of the section even when temporal sediment supply are held constant. Overpressure generation was found to be sensitive to change in sediment supply in permeable basins (at least 10−17 m2 in our model). We found that during basin evolution, temporal variations in overpressure and sediment supply fluctuations are not necessarily in phase with each other, especially in tight (low permeability) basins (<10−17 m2 in our model). 相似文献
137.
综合地球化学、高分辨层序地层学理论方法,利用双河露头资料及样品分析测试,采用多元统计方法优选出陆源输入强度相关元素组合Al-K-Ti-Mg-Rb-Cr-Zr、自生沉淀强度相关元素组合Ca-Mn-Ba-Co、有机质吸附及还原强度相关元素组合V-Ni-Mo-U-Cu-Zn作为化学层序地层划分指标体系,将双河露头五峰组划分为LCW四级层序,龙马溪组下段自下而上细分为MCL1-1、MCL1-2、MCL1-3、MCL1-4四级层序。陆源输入强度相关主微量元素组合总量在层序界面附近相对较高,而最大海泛面附近相对较低,具有元素总量减少-增加旋回性变化特征;而自生沉淀强度相关主量元素组合总量和微量元素组合总量、有机质吸附及还原强度相关微量元素组合总量在层序界面附近一般较低,在最大海泛面附近一般较高,具元素总量增多-减少旋回性变化特征。 相似文献
138.
Sensitivity of MM5 and WRF mesoscale model predictions of surface winds in a typhoon to planetary boundary layer parameterizations 总被引:1,自引:1,他引:1
Sea surface winds and coastal winds, which have a significant influence on the ocean environment, are very difficult to predict.
Although most planetary boundary layer (PBL) parameterizations have demonstrated the capability to represent many meteorological
phenomena, little attention has been paid to the precise prediction of winds at the lowest PBL level. In this study, the ability
to simulate sea winds of two widely used mesoscale models, fifth-generation mesoscale model (MM5) and weather research and
forecasting model (WRF), were compared. In addition, PBL sensitivity experiments were performed using Medium-Range Forecasts
(MRF), Eta, Blackadar, Yonsei University (YSU), and Mellor–Yamada–Janjic (MYJ) during Typhoon Ewiniar in 2006 to investigate
the optimal PBL parameterizations for predicting sea winds accurately. The horizontal distributions of winds were analyzed
to discover the spatial features. The time-series analysis of wind speed from five sensitivity experimental cases was compared
by correlation analysis with surface observations. For the verification of sea surface winds, QuikSCAT satellite 10-m daily
mean wind data were used in root-mean-square error (RMSE) and bias error (BE) analysis. The MRF PBL using MM5 produced relatively
smaller wind speeds, whereas YSU and MYJ using WRF produced relatively greater wind speeds. The hourly surface observations
revealed increasingly strong winds after 0300 UTC, July 10, with most of the experiments reproducing observations reliably.
YSU and MYJ using WRF showed the best agreements with observations. However, MRF using MM5 demonstrated underestimated winds.
The conclusions from the correlation analysis and the RMSE and BE analysis were compatible with the above-mentioned results.
However, some shortcomings were identified in the improvements of wind prediction. The data assimilation of topographical
data and asynoptic observations along coast lines and satellite data in sparsely observed ocean areas should make it possible
to improve the accuracy of sea surface wind predictions. 相似文献
139.
Samples were continuously collected from aerosol, fresh snow, and snow pits on Glacier No. 1 at Urumqi River source in eastern Tianshan (天山) Mountains. The deposition processes and the characteristics of mineral dust microparticles from aerosol to fresh snow, and then evolution to the snow pit were determined. Total dust microparticle concentration in the surface snow and aerosol showed a similar temporal variation trend, which was strongly associated with regional and local at-mospheric circulation in the ... 相似文献
140.