全文获取类型
收费全文 | 6433篇 |
免费 | 1078篇 |
国内免费 | 2483篇 |
专业分类
测绘学 | 783篇 |
大气科学 | 435篇 |
地球物理 | 2058篇 |
地质学 | 4370篇 |
海洋学 | 1101篇 |
天文学 | 36篇 |
综合类 | 457篇 |
自然地理 | 754篇 |
出版年
2024年 | 39篇 |
2023年 | 107篇 |
2022年 | 224篇 |
2021年 | 263篇 |
2020年 | 384篇 |
2019年 | 395篇 |
2018年 | 346篇 |
2017年 | 297篇 |
2016年 | 424篇 |
2015年 | 422篇 |
2014年 | 459篇 |
2013年 | 479篇 |
2012年 | 476篇 |
2011年 | 528篇 |
2010年 | 466篇 |
2009年 | 497篇 |
2008年 | 457篇 |
2007年 | 450篇 |
2006年 | 503篇 |
2005年 | 421篇 |
2004年 | 409篇 |
2003年 | 321篇 |
2002年 | 254篇 |
2001年 | 221篇 |
2000年 | 165篇 |
1999年 | 167篇 |
1998年 | 146篇 |
1997年 | 136篇 |
1996年 | 119篇 |
1995年 | 96篇 |
1994年 | 65篇 |
1993年 | 70篇 |
1992年 | 40篇 |
1991年 | 37篇 |
1990年 | 24篇 |
1989年 | 22篇 |
1988年 | 12篇 |
1987年 | 15篇 |
1986年 | 8篇 |
1985年 | 8篇 |
1984年 | 8篇 |
1983年 | 2篇 |
1982年 | 3篇 |
1980年 | 1篇 |
1979年 | 3篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1974年 | 1篇 |
1972年 | 1篇 |
1971年 | 1篇 |
排序方式: 共有9994条查询结果,搜索用时 0 毫秒
1.
Singh et al (2005) examined the potential of the ANN and neuro-fuzzy systems application for the prediction of dynamic constant of rockmass.
However, the model proposed by them has some drawbacks according to fuzzy logic principles. This discussion will focus on
the main fuzzy logic principles which authors and potential readers should take into consideration. 相似文献
2.
3.
4.
This paper presents the findings from an in-depth analysis of the (axial) stiffness data recorded during tension–tension fatigue tests on wire ropes, particularly in relation to how changes in stiffness during testing relate to changes in rope strength. A linear relationship between stiffness and strength is shown to exist and a methodology presented for quantifying residual strength with applied cycles. New lower bound fatigue lines for six-strand rope and spiral strand are presented which are based on a 10% loss of strength. These new lines have the advantage of having been established using a common discard criterion for wire ropes. 相似文献
5.
The longitudinal strength of turret mooring productive/storage tanker is studied.A numeri-cal example has been implemented according to the method presented in this paper to give practical il-lustration.From the results of the numerical example,it is concluded that the turret hole located near theforward of the amidships has small effect on the longitudinal strength of the ship hull.As for design ex-treme value of wave bending moment of storage tanker,statistic method is a more reasonablemethodology,especially with the consideration of the servere environmental conditions.The primary esti-mation of design section modulus of turret storage tanker can be determined by this design bending mo-ment. 相似文献
6.
7.
8.
I. Brandariz P. Castro M. Montes F. Penedo M.E. Sastre de Vicente 《Marine Chemistry》2006,102(3-4):291-299
Acid–base equilibrium constants of triethanolamine (TEA) have been determined by potentiometric titrations with a glass electrode, at 25 °C. Ionic strength was kept constant with only one electrolyte (using one of these salts: NaCl, KCl, MgCl2 or CaCl2), with binary mixtures of MgCl2 and CaCl2, and finally, in a solution with a composition approximately similar to that of natural seawater without sulfate. Equilibrium constants have been expressed in function of ionic strength by means of Pitzer equations and interaction parameters proposed in this theory have been obtained. It has been found that acid–base behaviour of TEA depends greatly on the salt used: basicity of TEA is decreased by CaCl2, while it is increased by the other electrolytes used in this work. 相似文献
9.
10.
- The dynamic response behaviors of upright breakwaters under broken wave impact are analysed based on the mass-damper-spring dynamic system model. The effects of the mass, damping, stiffness, natural period, and impulse duration (or oscillation period) on the translation, rotation, sliding force, overturning moment, and corresponding dynamic amplifying factors are studied. It is concluded that the ampli-ying factors only depend on the ratio of the system natural period to impulse duration (or oscillation period) under a certain damping ratio. Moreover, the equivalent static approach to breakwater design is also discussed. 相似文献