全文获取类型
收费全文 | 2936篇 |
免费 | 810篇 |
国内免费 | 1798篇 |
专业分类
测绘学 | 134篇 |
大气科学 | 7篇 |
地球物理 | 542篇 |
地质学 | 4247篇 |
海洋学 | 457篇 |
天文学 | 2篇 |
综合类 | 110篇 |
自然地理 | 45篇 |
出版年
2024年 | 7篇 |
2023年 | 28篇 |
2022年 | 70篇 |
2021年 | 87篇 |
2020年 | 135篇 |
2019年 | 164篇 |
2018年 | 149篇 |
2017年 | 110篇 |
2016年 | 186篇 |
2015年 | 222篇 |
2014年 | 257篇 |
2013年 | 235篇 |
2012年 | 273篇 |
2011年 | 295篇 |
2010年 | 270篇 |
2009年 | 347篇 |
2008年 | 272篇 |
2007年 | 292篇 |
2006年 | 357篇 |
2005年 | 279篇 |
2004年 | 279篇 |
2003年 | 210篇 |
2002年 | 163篇 |
2001年 | 147篇 |
2000年 | 168篇 |
1999年 | 148篇 |
1998年 | 105篇 |
1997年 | 87篇 |
1996年 | 60篇 |
1995年 | 32篇 |
1994年 | 39篇 |
1993年 | 23篇 |
1992年 | 13篇 |
1991年 | 16篇 |
1990年 | 5篇 |
1989年 | 6篇 |
1988年 | 3篇 |
1987年 | 3篇 |
1986年 | 1篇 |
1978年 | 1篇 |
排序方式: 共有5544条查询结果,搜索用时 234 毫秒
31.
1 .IntroductionThepenetratingbucketandboxfoundationisanewtypeofstructure ,whichhasbeenappliedinmanyengineeringfields .Inviewofthehighconstructioncostandtheformidableconstructibilityofoff shoreplatformswithpiledfoundations ,Baerheimetal.(1 990 )proposedtheconc… 相似文献
32.
Non-Simultaneous Failure of Ice in Front of Multi-Leg Structures 总被引:4,自引:1,他引:4
Because the multi-leg jacket structure is the major type of offshore structures in the Bohai Sea, the study of non-si-multaneous failure of i鏴 on multi-leg structures is important. However, the non-simultaneous failure has not been consid-ered in engineering design until now, obviously resulting in costly design and notable waste. To resolve this problem, this paper, by means of analysis of experimental data, calculates the coefficient of the non-simultaneous failure for the double-pile structure, the square four-leg structure, the single-line multi-pile structure, and the conical structure, respectively, and provides some reference criteria for engineering design. 相似文献
33.
Beach nourishment is an environmentally preferred method of shore protection, but the annual sand requirement may lead to substantial maintenance costs. The shoreline processes, involving the surf zone, beach and dune, are reviewed with the aim of reducing the annual sand requirement of eroding shorelines. It is shown that surf zones with equilibrium profiles, on which the wave energy conversion is evenly distributed across the surf zone, from experience for given conditions indicate least loss of sand. On steep, eroding shorelines it may be difficult to establish an equilibrium profile. For such cases, the use of perched surf zones is recommended, which are supported at the seaward limit by an underwater sill. For reduction of littoral transport, the use of pervious pile groynes is recommended. These are arguably more efficient than impervious groynes. The sand loss from a usually dry beach by raised water levels is shown to be a function of the beach slope and is least when the storm waves at raised water levels do not cut an erosion escarpment. The loss of sand from a dune by infrequent severe storm tides can be prevented with the aid of a built-in membrane. These sand losses are usually large and constitute an uneconomic use of this sand resource. The proposed concepts and measures are linked to existing knowledge, augmented by data from the large wave flume (LWF) in Germany and field data from the North and Baltic Sea coasts. 相似文献
34.
Yang Zhengji Zuo Qihua
Senior Engineer River Harbour Department Nanjing Hydraulic Research Institute Nanjing Engineer River Harbour Department Nanjing Hydraulic Research Institute Nanjing 《中国海洋工程》1991,(2)
The wave forces on 1, 2 and 4 vertical circular piles under the action of several wave trains of the same wave parameters, such as Hs,Tp and Mo, but different wave group factor GF are measured in the laboratory. After comparing these forces, it may be concluded that the mean and significant wave forces are almost of no difference for the wave trains with different GF. When GF is larger, the one-tenth of the wave froce extreme is slightly increased and the maximum wave force is much larger than the ones with smaller GF, to which attention must be paid in engineering practice. 相似文献
35.
某港口堆场地基上部5.0m系吹填而成,地表下18m范围均属软土,经真空预压初级加固后地基承载力仅在80—90kPa,局部区域上部淤泥土层土性指标较差,含水量大于50%,地基承载力不足60kPa。为了使地基达到230kPa的承载要求,设计采用深层搅拌法加固超软弱地基。通过现场成桩工艺试验和检测表明,桩身水泥土强度在90d龄期时大于1.80MPa,单桩承载力标准值大于150kN,以φ600桩径、桩长13.5m、置换率为0.308和φ500桩径、桩长13.5m、置换率为0.267两种方案布置的复合地基承载力标准值均超过了230kPa的设计要求。试验结果表明,深层搅拌法在港口超软弱地基土应用只要施工工艺适当,完全可以使地基承载力提高2—3.5倍以土,从而节省大量的工程投资。 相似文献
36.
37.
38.
39.
基于粉喷桩复合地基沉降计算的探讨 总被引:1,自引:1,他引:0
在对粉喷桩复合地基现有的沉降计算理论分析的基础上,结合粉喷桩的荷载传递规律,提出符合工程实际的沉降计算方法。 相似文献
40.
浅谈测井方法在工程勘察中的应用 总被引:1,自引:0,他引:1
地球物理测井应用于工程勘察中,能够较好地解决用钻探不易解决的问题,如有效判别薄夹层、寻找井旁隐伏断裂破碎带、判断孔内土层稳定性以及测定土层的速度等。其中自然伽马测井曲线在判定含砾粘土夹层及软弱薄粘土夹层等方面具有较高的准确性;声波、井径、自然γ、视电阻率等测井方法可有效查找井旁隐伏断裂破碎带,特别是声波测井曲线异常更为明显;另外跨孔实测剪切波速还可进行地基土加固效果检验。 相似文献