全文获取类型
收费全文 | 24466篇 |
免费 | 4449篇 |
国内免费 | 6379篇 |
专业分类
测绘学 | 4356篇 |
大气科学 | 4716篇 |
地球物理 | 6055篇 |
地质学 | 10607篇 |
海洋学 | 3558篇 |
天文学 | 261篇 |
综合类 | 1989篇 |
自然地理 | 3752篇 |
出版年
2024年 | 95篇 |
2023年 | 282篇 |
2022年 | 827篇 |
2021年 | 975篇 |
2020年 | 1161篇 |
2019年 | 1343篇 |
2018年 | 1126篇 |
2017年 | 1284篇 |
2016年 | 1355篇 |
2015年 | 1503篇 |
2014年 | 1604篇 |
2013年 | 1805篇 |
2012年 | 1669篇 |
2011年 | 1717篇 |
2010年 | 1369篇 |
2009年 | 1523篇 |
2008年 | 1606篇 |
2007年 | 1650篇 |
2006年 | 1566篇 |
2005年 | 1387篇 |
2004年 | 1218篇 |
2003年 | 1069篇 |
2002年 | 988篇 |
2001年 | 830篇 |
2000年 | 773篇 |
1999年 | 702篇 |
1998年 | 654篇 |
1997年 | 569篇 |
1996年 | 509篇 |
1995年 | 457篇 |
1994年 | 413篇 |
1993年 | 341篇 |
1992年 | 209篇 |
1991年 | 184篇 |
1990年 | 128篇 |
1989年 | 91篇 |
1988年 | 96篇 |
1987年 | 54篇 |
1986年 | 35篇 |
1985年 | 33篇 |
1984年 | 19篇 |
1982年 | 10篇 |
1981年 | 7篇 |
1980年 | 10篇 |
1979年 | 10篇 |
1978年 | 15篇 |
1977年 | 4篇 |
1976年 | 3篇 |
1973年 | 2篇 |
1954年 | 12篇 |
排序方式: 共有10000条查询结果,搜索用时 78 毫秒
71.
72.
揭示Rankine涡风场模式和Jelesnianski风场模式之间的联系,并设计了一种台风风场分布模式,它的风速分布曲线落在Jelesnianski和Rankine涡两个风场模式的风速分布曲线之间,具有一个既优于Jelesnianski又优于Rankine涡的风速衰减速率,因此它同时克服了Rankine涡模式计算风速偏小和Jelesnianski模式计算风速偏大的缺点,以一种比较合理的变化趋势向远方衰减,成为一个比较切合实际的台风风场分布模式。同时,文中提出的移行台风风场计算方法对宫崎正卫、上野武夫和Jelesnianski模式都有一定的改进。 相似文献
73.
Fayun Liang Mingyi Zhao Chengrui Qin Yajie Jia Zhongwei Wang Guiping Yue 《Marine Georesources & Geotechnology》2020,38(1):114-121
AbstractThe construction of a 100-km road network is planned on a land reclamation area in the Oujiang Estuary in China. The embankment had a height of 4 m and a base width of 60 m. The reclamation area is newly filled by a 3-m dredger fill on a 48-m thick layer of marine clay. Estimation of the settlement of the future road network is difficult. To guide the construction of the road network, a 1/100-scale centrifuge model test was performed with a marine clay sample from the construction site to simulate the layered settlements and evaluate the drainage effect of prefabricated vertical drains in the dredger fill in the following 10 years. The results of the centrifuge modeling test are verified by 10-month in situ monitoring, which shows agreement between the centrifuge modeling test results and the in situ results. The test results indicate that additional time is needed to reinforce the newly added dredger fill by the surcharge preloading method to uplift the elevation of the reclamation area with dredger fill. 相似文献
74.
双斑东方鲀人工繁殖及育苗技术 总被引:5,自引:2,他引:5
本文报道了福建省水产研究所 2 0 0 1年双斑东方人工繁殖及育苗过程与结果 .在春季当海水水温达到 1 6℃以上时 ,用DOM、LRH A3或HCG进行催产 ,混和或单一使用 ,剂量视亲鱼性腺成熟度而定 .受精卵在水温 1 8.0~ 2 2 .4℃、盐度 2 2 .1~2 8.6条件下 ,经 1 1 7~ 1 56h孵化 .用 2 0 5万尾开口仔鱼培育出平均全长为 3 7mm ,平均体重为 1 .3 g的鱼苗 52 .3 5万尾 ,成活率 2 5.5%.此外 ,对亲鱼的暂养、催产、受精卵的孵化、仔鱼的前期培育和后期培育等关键环节进行了探讨 . 相似文献
75.
本文提出了一种地震折射液的虚拟射线理论,根据该理论,只要已知地表层的速度,即可直接由折射波信息提取地震参数,从而可实现折射界面的反演。 文中通过实际介质模型的计算机实验结果,验证了该理论的正确性。 相似文献
76.
77.
The Agulhas Ridge is a prominent topographic feature that parallels the Agulhas-Falkland Fracture Zone (AFFZ). Seismic reflection
and wide angle/refraction data have led to the classification of this feature as a transverse ridge. Changes in spreading
rate and direction associated with ridge jumps, combined with asymmetric spreading within the Agulhas Basin, modified the
stress field across the fracture zone. Moreover, passing the Agulhas Ridge’s location between 80 and 69 Ma, the Bouvet and
Shona Hotspots may have supplied excess material to this part of the AFFZ thus altering the ridge’s structure. The low crustal
velocities and overthickened crust of the northern Agulhas Ridge segment indicate a possible continental affinity that suggests
it may be formed by a small continental sliver, which was severed off the Maurice Ewing Bank during the opening of the South
Atlantic. In early Oligocene times the Agulhas Ridge was tectono-magmatically reactivated, as documented by the presence of
basement highs disturbing and disrupting the sedimentary column in the Cape Basin. We consider the Discovery Hotspot, which
distributes plume material southwards across the AAFZ, as a source for the magmatic material. 相似文献
78.
考虑到平台所在海区台风出现的频次及其诱发之风、浪、潮、流极端海况联合出现的概率特性,本文推导出Poisson—Logistic二元复合极值模式,并以平台甲板标高进行实例计算。新模式增加了概率模型的物理内涵,解决了Logistic模型阈值选取的任意性。对海洋工程极端海况荷载组合预测具有广泛的应用前景。 相似文献
79.
A coupled wave–tide–surge model has been developed in this study in order to investigate the effect of the interactions among tides, storm surges, and wind waves. The coupled model is based on the synchronous dynamic coupling of a third-generation wave model, WAM cycle 4, and the two-dimensional tide–surge model. The surface stress, which is generated by interactions between wind and wave, is calculated by using the WAM model directly based on an analytical approximation of the results using the quasi-linear theory of wave generation. The changes in bottom friction are created by the interactions between waves and currents and calculated by using simplified bottom boundary layer model. In consequence, the combined wave–current-induced bottom velocity and effective bottom drag coefficient were increased in the shallow waters during the strong storm conditions. 相似文献
80.
A coding error in the s-Coordinate Primitive Equation Model (SPEM) has led to misleading statements about the behaviour of the Mellor–Yamada level 2 parameterization of vertical mixing. It has been claimed that the scheme removes static instability only very slowly and preserves statically unstable stratifications for an unrealistic long time. This note corrects this statement by demonstrating that the Mellor–Yamada mixing scheme, if implemented correctly, tends to overestimate rather than underestimate vertical mixing in seasonally ice-covered seas. Similar to other mixing schemes with the same behaviour, this leads to spurious open ocean deep convection, an unrealistic homogenization of the water column, and a significant reduction of sea ice volume. 相似文献