全文获取类型
收费全文 | 10993篇 |
免费 | 2010篇 |
国内免费 | 2956篇 |
专业分类
测绘学 | 1000篇 |
大气科学 | 2310篇 |
地球物理 | 2552篇 |
地质学 | 5787篇 |
海洋学 | 1496篇 |
天文学 | 348篇 |
综合类 | 979篇 |
自然地理 | 1487篇 |
出版年
2024年 | 53篇 |
2023年 | 212篇 |
2022年 | 447篇 |
2021年 | 575篇 |
2020年 | 415篇 |
2019年 | 553篇 |
2018年 | 618篇 |
2017年 | 546篇 |
2016年 | 650篇 |
2015年 | 566篇 |
2014年 | 652篇 |
2013年 | 635篇 |
2012年 | 702篇 |
2011年 | 764篇 |
2010年 | 722篇 |
2009年 | 668篇 |
2008年 | 571篇 |
2007年 | 652篇 |
2006年 | 549篇 |
2005年 | 523篇 |
2004年 | 437篇 |
2003年 | 368篇 |
2002年 | 530篇 |
2001年 | 440篇 |
2000年 | 421篇 |
1999年 | 450篇 |
1998年 | 282篇 |
1997年 | 297篇 |
1996年 | 248篇 |
1995年 | 261篇 |
1994年 | 216篇 |
1993年 | 212篇 |
1992年 | 150篇 |
1991年 | 122篇 |
1990年 | 92篇 |
1989年 | 74篇 |
1988年 | 66篇 |
1987年 | 55篇 |
1986年 | 33篇 |
1985年 | 23篇 |
1984年 | 21篇 |
1983年 | 13篇 |
1982年 | 20篇 |
1981年 | 9篇 |
1980年 | 12篇 |
1979年 | 6篇 |
1972年 | 2篇 |
1971年 | 3篇 |
1958年 | 15篇 |
1947年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
This paper proposes a multi‐level parallelized substructuring–frontal combined algorithm for the analysis of the problem of thermo/hydraulic/mechanical behaviour of unsaturated soil. Temperature, displacement, pore water pressure and pore air pressure are treated as the primary variables in a non‐linear analysis. Details are given firstly of the substructuring–frontal combined approach. The incorporation of the algorithm in a multi‐level parallel strategy is then discussed. The parallel processing can thus be carried out at different substructural levels. The method thus developed impacts, in a positive way, on both computer storage requirement and execution time. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
12.
Pco2 of air and seawater samples from the East China Sea(ECS) were measured in situ in autumn, 1994,Ocean currents,terrestrial fluviation,biological activities,etc.,Pco2 char-acters in air and seawater were investigated,CO2 flux and its character in the East China Sea are discussed on the basis of the Pco2 profiles of air and seawater,It was clear that the nearshore was the source of CO2;and tht the oulter sea area was the sink of CO2; and that the shelf area of the EXS is a net sink for atmospheric CO2 in autumn. 相似文献
13.
本文给出1993—1994年期间,用云南天文台1米望远镜折轴摄谱仪观测获得类太阳色球活动星。εEri的5个波段高分辨、高信噪比光谱,运用两种不同方法:谱线轮廓塞曼致宽分析和多重线统计分析法成功地测定了εEri的表面磁场强度和磁场的覆盖因子,并对这两种磁场测定方法作了简单的讨论. 相似文献
14.
We have studied the optical historical light curves of two Active Galactic Nuclei (AGNs): OJ287 and 3C345. We find a linear
dependence between the magnitude and the logarithm of the length of the time the objects stay below this magnitude. The relation
may originate from a fractal structure of the light curve.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
15.
在20℃、4℃、-10℃、-20℃四种温度下贮藏马面卵巢,对其中磷脂含量的变化进行了测定,并利用薄层层析分析测定了不同温度下贮存3d后马面卵巢中磷脂各组分的相对百分比。结果表明马面卵巢中磷脂的损失率随贮藏温度的上升而增加;在不同温度下贮藏3d,磷脂各组分的相对百分比都发生了变化;随贮藏温度的升高磷脂酰胆碱的降解速度大大加快,所占的百分比快速下降,而溶血磷脂酰胆碱的比例有不同程度的增加。相对而言,-20℃下贮藏数天,磷脂的含量及组分的变化较小。 相似文献
16.
Hong Lin Zhang Douglas H. Sampson 《Monthly notices of the Royal Astronomical Society》2001,322(3):433-437
Calculations are made of the resonance contribution to electron-impact excitation of H-like 13 C and Li-like 23 Na, 25 Mg, 27 Al and 29 Si to the upper hyperfine levels that produce millimetre (mm) lines of likely astrophysical interest. The resonance contribution is found to be very important for these Li-like ions, considerably more important than for Li-like 57 Fe considered previously. However, resonances are found to be rather unimportant for H-like 13 C. The effect of radiative decay on the resonance contribution is found to be insignificant in all of the present calculations. 相似文献
17.
18.
19.
CLIMATICTRENDINDICATEDBYVARIATIONSOFGLACIERSANDLAKESINTHETIANSHANMOUNTAINS¥HuRuji;YangChuande;MaHong;JiangFengqing(XinjiangIn... 相似文献
20.
This paper presents a numerical model for predicting the dynamic response of rock mass subjected to large‐scale underground explosion. The model is calibrated against data obtained from large‐scale field tests. The Hugoniot equation of state for rock mass is adopted to calculate the pressure as a function of mass density. A piecewise linear Drucker–Prager strength criterion including the strain rate effect is employed to model the rock mass behaviour subjected to blast loading. A double scalar damage model accounting for both the compression and tension damage is introduced to simulate the damage zone around the charge chamber caused by blast loading. The model is incorporated into Autodyn3D through its user subroutines. The numerical model is then used to predict the dynamic response of rock mass, in terms of the peak particle velocity (PPV) and peak particle acceleration (PPA) attenuation laws, the damage zone, the particle velocity time histories and their frequency contents for large‐scale underground explosion tests. The computed results are found in good agreement with the field measured data; hence, the proposed model is proven to be adequate for simulating the dynamic response of rock mass subjected to large‐scale underground explosion. Extended numerical analyses indicate that, apart from the charge loading density, the stress wave intensity is also affected, but to a lesser extent, by the charge weight and the charge chamber geometry for large‐scale underground explosions. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献