全文获取类型
收费全文 | 795篇 |
免费 | 82篇 |
国内免费 | 118篇 |
专业分类
测绘学 | 19篇 |
大气科学 | 151篇 |
地球物理 | 203篇 |
地质学 | 329篇 |
海洋学 | 138篇 |
天文学 | 58篇 |
综合类 | 38篇 |
自然地理 | 59篇 |
出版年
2023年 | 6篇 |
2022年 | 17篇 |
2021年 | 26篇 |
2020年 | 26篇 |
2019年 | 21篇 |
2018年 | 29篇 |
2017年 | 39篇 |
2016年 | 43篇 |
2015年 | 35篇 |
2014年 | 40篇 |
2013年 | 55篇 |
2012年 | 42篇 |
2011年 | 52篇 |
2010年 | 54篇 |
2009年 | 42篇 |
2008年 | 46篇 |
2007年 | 31篇 |
2006年 | 20篇 |
2005年 | 28篇 |
2004年 | 19篇 |
2003年 | 19篇 |
2002年 | 22篇 |
2001年 | 13篇 |
2000年 | 28篇 |
1999年 | 29篇 |
1998年 | 26篇 |
1997年 | 26篇 |
1996年 | 19篇 |
1995年 | 16篇 |
1994年 | 19篇 |
1993年 | 9篇 |
1992年 | 10篇 |
1991年 | 11篇 |
1990年 | 9篇 |
1989年 | 8篇 |
1988年 | 6篇 |
1987年 | 3篇 |
1986年 | 4篇 |
1985年 | 5篇 |
1983年 | 3篇 |
1982年 | 5篇 |
1981年 | 3篇 |
1980年 | 3篇 |
1977年 | 3篇 |
1976年 | 2篇 |
1975年 | 2篇 |
1971年 | 2篇 |
1962年 | 2篇 |
1954年 | 3篇 |
1936年 | 4篇 |
排序方式: 共有995条查询结果,搜索用时 515 毫秒
91.
Climatological features of WRF-simulated tropical cyclones over the western North Pacific 总被引:2,自引:0,他引:2
Dasol Kim Chun-Sil Jin Chang-Hoi Ho Jinwon Kim Joo-Hong Kim 《Climate Dynamics》2015,44(11-12):3223-3235
92.
Distribution of dinoflagellate cysts in Yellow Sea sediments 总被引:1,自引:1,他引:0
To investigate the distribution,abundance,and species composition of dinoflagellate cysts in the Yellow Sea,surface sediment samples were collected at 37 sites,including the Korean dump site.Twenty-one dinoflagellate cyst taxa were identified,with the assemblages dominated mainly by Spiniferites bulloideus,Operculodinium centrocarpum,and cyst of Alexandrium catenella/tamarense type.A high frequency of O.centrocarpum in the Yellow Sea was observed for the first time,and it is likely that this can be attributed to the dynamics of the Yellow Sea Cold Water Mass and the Changjiang(Yangtze) River runoff.Total cyst concentrations ranged from 23 to 48 442 cysts/g dry weight,and high cyst concentrations were recorded adjacent to the dumping site.This result suggests that anthropogenic activities such as ocean dumping stimulate the growth of dinoflagellates in the Yellow Sea,which in turn leads to high levels of dinoflagellate cyst production. 相似文献
93.
商丹断裂带作为扬子板块与华北板块的缝合带,在秦岭造山带中占据重要的地位。对其进行精细的构造研究,是了解扬子板块与华北板块相互作用过程的关键。研究工作在商丹断裂带东段展开,对该带进行了详细的野外观察、显微构造观察、糜棱岩化过程中温度的估算、有限应变测量、差异应力的计算以及糜棱岩化过程中运动学涡度的计算。变形温压条件指示糜棱岩形成于中-高绿片岩相到低角闪岩相变质条件。差异应力计算结果指示商丹带具备大型构造动力特征。涡度分析表明该断裂带的变形以纯剪切作用占据主导作用,但包含有简单剪切的分量,从而证明了扬子板块与华北板块之间具有以碰撞挤压为主的斜向汇聚方式。 相似文献
94.
This study investigates the decrease in the frequency of onset vortex of summer monsoon during recent decades using the National Center for Environmental Prediction–National Center for Atmospheric Research reanalysis (1982–2011) data. Onset vortices are known to occur over the Arabian Sea mini warm pool where the sea surface temperature peaks just before the onset of monsoon. Even though the Arabian Sea mini warm pool intensifies during the recent decades, they are not seen as a regular feature. It is found from the analysis of irrotational and non-divergent wind component at 850 and 200 hPa that during the recent decades, convergent winds dominate at upper levels and divergent winds at lower levels which inhibits convection. Moreover, the cyclonic shear vorticity shows a decrease in the recent decades which tend to reduce the boundary layer moisture convergence and lower tropospheric humidity which is an important component for the initiation of a cyclonic system. The recent decades are characterized by weak convection due to the presence of strong northerlies and descending motion at lower levels in the southeast Arabian Sea. The response of atmospheric circulation to the interdecadal variations in the warm pool and the corresponding decrease in the frequency of onset vortex formation is analyzed in detail. 相似文献
95.
Tai Ho Choo Soo Kwon Chae Hyeon Cheol Yoon Yeon Moon Choo 《Environmental Earth Sciences》2014,71(2):675-683
Discharge is an important factor in river design for water utilization, water control and hydraulic structures; therefore, an accurate estimation of the discharge is required. At present, a rating curve depicting the relationship between a stage and discharge is used to calculate the discharge from river systems. Although the rating curve has an advantage in that it can predict and use the discharge during the flood season in which the measurement is difficult, there is room for improvement as it does not reflect the hydraulic characteristics of rivers. Therefore, in this study, discharge was predicted using the convenient calculation method with empirical mediating variables of the Manning and Chezy equations which were proposed by the author’s previous research as a new methodology for estimating discharge in an open channel. This was proven, based on the data measured in a meandering open channel system in a lab at the Mississippi River in the US and at the Columbia Del Dique Canal, and an accuracy level at a coefficient of 0.8 was demonstrated. Thus, this method, which reflects the hydraulic characteristics and predicts the discharge in a simple manner, is expected to be convenient in practice. 相似文献
96.
A low-complexity time-domain approach for global navigation satellite systems is proposed to detect and identify single-tone, multi-tone, swept continuous wave interference (CWI) and band-limited white Gaussian noise (BLWN). An adaptive notch filter and adaptive cascading filter structure are employed to identify the type of interference signals. The number of the cascading stages is selected by comparing the total power in receiver bandpass, and after, passing the adaptive notch filter. For this reason, the proposed filter structure is more efficient in identifying and mitigating interference signals than the conventional filter structure. In addition, the automatic gain control gain is used to detect the existence of continuous wave interference. The performance of the interference detection and identification method is evaluated for the cases of GPS signal in the presence of single-tone, multi-tone, swept CWI and BLWN. 相似文献
97.
Raymond F. Smith K. Thomas Lorenz Darwin Ho Bruce A. Remington Alex Hamza John Rogers Stephen Pollaine Seokwoo Jeon Yun-Suk Nam J. Kilkenny 《Astrophysics and Space Science》2007,307(1-3):269-272
In recently developed laser-driven shockless compression experiments an ablatively driven shock in a primary target is transformed
into a ramp compression wave in a secondary target via unloading followed by stagnation across an intermediate vacuum gap.
Current limitations on the achievable peak longitudinal stresses are limited by the ability of shaping the temporal profile
of the ramp compression pulse. We report on new techniques using graded density reservoirs for shaping the loading profile
and extending these techniques to high peak pressures. 相似文献
98.
99.
Yu-Li Wang Liang-Cheng Chang Fei Liu Yen-Te Ho Tzu Bin Wang Tian-Chyi Jim Yeh Jui-Pin Tsai 《Ground water》2022,60(4):518-529
Groundwater responses measured from multiple wells at different depths are essential for delineating the aquifer heterogeneity using hydraulic tomography (HT). In general, conducting HT requires many wells because traditional well monitoring is usually partially open at a specific depth interval or is fully penetrating. Accordingly, conducting an HT survey is typically costly and time-consuming. To tackle these issues, a new multi-level monitoring system (MLMS) for the HT survey was developed using the fiber Bragg grating (FBG) technique. This FBG MLMS could collect the depth-discrete groundwater observations from a fully penetrated 2-inch well. Three field campaigns were conducted to validate the capability of the FBG MLMS for HT surveys. The results show that the accuracy and stability of this MLMS are reliable and that FBG MLMS is beneficial for conducting an HT survey. Specifically, compared to the traditional monitoring well in an injection event, this FBG MLMS can concurrently cause an increase in the number of cross-hole tests several times and collect many more head observations than the standard methods, resulting in the observed flow fields efficiently reaching ergodic conditions and effectively improving the accuracy of the estimated hydraulic heterogeneity. Therefore, the FBG MLMS could be an alternative MLMS for efficiently and economically conducting an HT survey. 相似文献