全文获取类型
收费全文 | 14569篇 |
免费 | 3313篇 |
国内免费 | 4632篇 |
专业分类
测绘学 | 2756篇 |
大气科学 | 2290篇 |
地球物理 | 3034篇 |
地质学 | 8608篇 |
海洋学 | 2495篇 |
天文学 | 234篇 |
综合类 | 1199篇 |
自然地理 | 1898篇 |
出版年
2024年 | 123篇 |
2023年 | 318篇 |
2022年 | 747篇 |
2021年 | 987篇 |
2020年 | 715篇 |
2019年 | 933篇 |
2018年 | 850篇 |
2017年 | 847篇 |
2016年 | 838篇 |
2015年 | 962篇 |
2014年 | 986篇 |
2013年 | 1113篇 |
2012年 | 1245篇 |
2011年 | 1228篇 |
2010年 | 1161篇 |
2009年 | 1124篇 |
2008年 | 1121篇 |
2007年 | 1079篇 |
2006年 | 963篇 |
2005年 | 907篇 |
2004年 | 729篇 |
2003年 | 518篇 |
2002年 | 682篇 |
2001年 | 587篇 |
2000年 | 472篇 |
1999年 | 301篇 |
1998年 | 157篇 |
1997年 | 136篇 |
1996年 | 99篇 |
1995年 | 105篇 |
1994年 | 88篇 |
1993年 | 50篇 |
1992年 | 65篇 |
1991年 | 44篇 |
1990年 | 44篇 |
1989年 | 25篇 |
1988年 | 32篇 |
1987年 | 26篇 |
1986年 | 15篇 |
1985年 | 11篇 |
1984年 | 17篇 |
1983年 | 7篇 |
1982年 | 9篇 |
1981年 | 7篇 |
1980年 | 6篇 |
1979年 | 9篇 |
1977年 | 3篇 |
1971年 | 3篇 |
1957年 | 5篇 |
1954年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
ECOLOGICAL SERIES OF SOIL ANIMALS IN DARLIDAI MOUNTAIN 总被引:1,自引:0,他引:1
HOUWei-ling FANHong 《中国地理科学(英文版)》2002,12(4):378-382
The ecological series of soil animals under the broad-leaved and pine mixed forest in Darlidai Mountainwas studied. Seven sample plots were selected according to different altitude gradients, which belong to different vegeta-tion types. By investigating and analyzing soil animals in every sample plot it is found that there are 45 groups and 1956individuals, which axe involved in 3 phylums, 7 classes, 16 orders, respectively. The altitude is a key factor which af-fects ecological series of soil animals. Both the groups and individuals of soil animals increase with altitude increasingunder certain conditions, which contrastes with ordinary cases, resulting from special micro-climate in studied area. Thegroups and individuls of soil animals are the most under the broad-leaved and pine forest on the top of the mountain, andthe least under Picea-Abies forest in the foot of the mountain. 相似文献
2.
Heat-shock protein 70 expression in shrimp Fenneropenaeus chinensis during thermal and immune-challenged stress 总被引:4,自引:0,他引:4
Using western immunoblotting, we obtained heat-shock protein 70 (HSP70) induction data and distribution in different tissues from shrimp Fenneropenaeus chinensis during thermal and immune-challenged stresses. This is probably the first report of the effects of various stressors on the expression of HSP70 in shrimp.HSP70 was prominently induced in hepatopancreas and gills, but not in muscle, eyestalk and hemolymph, when the shrimp were exposed to heat shock and Vibrio anguillavium-challenged stresses. Cold shock and WSSV treatment had no significant effects on the levels of HSP70 expression in all tissues examined. HSP70 induction was greatest after 2 h exposure to heat shock stress, which was elevated after acute heat shock exposure of 10℃ above ambient temperature. 相似文献
3.
为了便于大型软件系统的后续开发和用户软件系统的升级,介绍了软件系统在Internet/Intranet上更新功能或数据的原理和方法,并用C#.Net进行了编程实现。 相似文献
4.
本文通过对1980年以来长江上游10次洪涝过程的500hpa环流形势分析,并用车比雪夫多项式对500hpa高度场进行展开,研究了各类洪涝过程的中期演变特征,发现代表不同洪涝过程环流形势变化的不同的车氏系数值都有明显的特征变化,结合欧洲中心中期数值预告96小时500hpa高度场的车氏系数分析,可为洪涝暴雨的中期预报提供一种新的思路。 相似文献
5.
GPS/LEO掩星观测的变分同化技术 总被引:6,自引:0,他引:6
在简单介绍GPS/LEO掩星探测大气的发展历史和科学意义之后,详细阐述了反演的基本原理;分析了标准反演中存在的问题,并说明一维变分同化(1DVAR)在反演方法中的重要性;给出了一维变分同化中价值函数的求解,以及各种同化因子;简单介绍了对当前气象学中普遍使用的四维变分同化(4DVAR);重点讨论了各种同化方法,以及使用各种同化因子的优缺点。最后,通过CHAMP卫星的观测实例分析,验证了GPS数据在数值天气预报(NWP)中的作用,以及相对于标准反演法一维变分对气象要素的改进。 相似文献
6.
The Tamtsag Basin is located in the extreme eastern portion of the Mongolia. The Basin and its counterpart in China (the Hailar Basin) are united a whole basin on the structural setting. In recent years, the Tamtsag Basin attracts more and more attention with the important exploration discovered in the 19th block by SOCO and in Hailar Basin of China. This paper discusses the exploration potential of Tamtsag Basin from the viewpoint of petroleum geology. 相似文献
7.
概略地叙述了西宁地区的泥石流形成条件和形成机理,并将西宁地区泥石流划分为稀性泥石流类及泥石质泥石流种类。在此基础上提出防治泥石流灾害的意见。 相似文献
8.
LI Zhenxing LIN Hong CAO Limin 《中国海洋大学学报(英文版)》2006,5(2):115-118
The present study was undertaken to determine whether high intensity ultrasound could reduce the allergic properties of shrimp allergens. Reducing the allergenic properties of these allergens will be beneficial to allergic individuals. Samples of shrimp protein extract and shrimp muscle were treated by high-intensity ultrasound with water bathing at 0 ℃ or 50 ℃ for different time periods. The treated and untreated samples were then analyzed by SDS-PAGE, Western blots and competitive inhibition ELISA (Ci-ELISA) to determine the shrimp allergenicity. The results show that high-intensity ultrasound has no effect on allergenicity when the extracts were treated at 0℃. However, a significant decrease was observed in the level of the major shrimp allergen, Pen a 1, when the samples were treated at 50 ℃. In the determination of allergenicity with CiELISA, a reduction in IgE binding was also observed. 相似文献
9.
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
10.
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