全文获取类型
收费全文 | 148篇 |
免费 | 57篇 |
国内免费 | 49篇 |
专业分类
测绘学 | 10篇 |
大气科学 | 2篇 |
地球物理 | 48篇 |
地质学 | 150篇 |
海洋学 | 24篇 |
天文学 | 2篇 |
综合类 | 10篇 |
自然地理 | 8篇 |
出版年
2023年 | 1篇 |
2022年 | 6篇 |
2021年 | 4篇 |
2020年 | 6篇 |
2019年 | 5篇 |
2018年 | 10篇 |
2017年 | 6篇 |
2016年 | 8篇 |
2015年 | 8篇 |
2014年 | 11篇 |
2013年 | 16篇 |
2012年 | 14篇 |
2011年 | 15篇 |
2010年 | 8篇 |
2009年 | 10篇 |
2008年 | 14篇 |
2007年 | 9篇 |
2006年 | 10篇 |
2005年 | 13篇 |
2004年 | 4篇 |
2003年 | 12篇 |
2002年 | 10篇 |
2001年 | 9篇 |
2000年 | 11篇 |
1999年 | 3篇 |
1998年 | 4篇 |
1997年 | 5篇 |
1996年 | 8篇 |
1995年 | 3篇 |
1994年 | 6篇 |
1992年 | 1篇 |
1991年 | 2篇 |
1986年 | 1篇 |
1984年 | 1篇 |
排序方式: 共有254条查询结果,搜索用时 750 毫秒
91.
1 Introduction T he translationally controlled tum or protein(TC TP) w as firstdescribed as a grow th-related proteinin m ouse E hrilisch ascites tum or cells and ery-throleukem ia cells (Y enofsky etal., 1983). Subse-quently, TC TP w as founded to be present in m anycells (Sanchez etal., 1997; G ross etal., 1989; C hunget al., 2000; V ercoutter-Edouart et al., 2001) exceptthe hum an kidney cell(Sanchez etal.,1997;G achetetal., 1999). H om ologues of TC TP have been reportedfrom sever… 相似文献
92.
采用数理统计的方法,对1991~1992年海湾扇贝控温促熟实验的有关数据进行分析。得到海湾扇贝在青岛地区性腺发育的生物学零度为6.6℃,产卵的有效积温为178.9℃。 相似文献
93.
94.
离子束抛光工艺中驻留时间的分步消去算法 总被引:1,自引:0,他引:1
在离子束抛光工艺中,驻留时间的求解是很关键的。求解驻留时间是利用离子束加工函数和驻留时间的卷积等于镜面去除量的关系,而离子束抛光的过程就是一个执行解卷积的过程。受此启发,采用一种分步消去算法解矩阵的卷积运算。这种新算法占用计算机资源少,运算速度快,同时可以根据预先设定的加工精度算得满足要求的驻留时间函数。对这种新算法进行仿真分析,采用3种不同的消去顺序分步加工,得到了理想的仿真结果,PV值由抛光前的363.721 nm分别减小到6.136 nm、33.347 nm、3.875 nm,抛光后的镜面精度提高了很多。 相似文献
95.
In order to explore the regularity between Wanrendong gold deposit and geophysical electrical characteristics and expand thoughts for Wanrendong gold deposit prospecting, the authors comprehensively investigated the electrical structural characteristics of Wanrendong gold mine area, through the introduction of geological and physical characteristics of Wanrendong gold deposit, as well as the CSAMT (controlled source audio magnetotelluric method) basic theory and the transitivity measurement work. The spatial distribution characteristics of gold deposit-related geologic body, structure, and alteration was identified, and the prospecting geophysical rules of gold deposit were summarized in this paper. The gold deposit was mostly distributed in the geophysical low resistance anomaly areas, or transition areas between high resistance and low resistance. This method proved to be effective and dependable after later borehole certification. These achievements could provide geophysical exploration method of gold-prospecting for Wamrendong gold deposit area or similar areas. 相似文献
96.
97.
Daily outflow frequencies and recession curves were used to identify differences in storage–outflow relationships between two different drainage systems, conventional and controlled drainage. A three‐year (1996–1999) field drainage experiment was carried out on a loamy sand soil in southern Sweden. Plots with an area of 0·2 hectares were drained by conventional subsurface drainage (CD) or by controlled drainage (CWT1 and CWT2). The controlled drainage system allowed the groundwater level in the soil to be varied during the year. It was kept at least 70 cm below the soil surface during the growing season but allowed to rise to a maximum of 20 cm below the soil surface during the rest of the year. Measurements were performed to record precipitation, drain outflow and groundwater levels. Daily values of outflow were divided into 10 categories, based on the size of outflow. Recession curves of hourly measurement of outflow were selected. They behaved like single reservoirs and a linear storage–outflow model was applied. Least squares estimates of the parameters initial outflow, initial storage volume and retention constant were calculated. Controlled drainage had a significant effect on total drain outflow and outflow pattern during the three years of measurement. The total drain outflow was 70% to 90% smaller in CWT than in CD. The analysis revealed that the initial outflows were higher, the retention constant and the temporary storage lower in CWT. The hydrological impacts of the reduction in temporary storage were higher peak flow, shorter lag time and shorter recession time and these effects increased with an increased groundwater level. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
98.
岩土体导热系数在与地热有关的地质基础研究和生产应用中有重要作用。首先介绍了导热系数的概念,然后分析了导热系数的受控因素,最后探讨了导热系数的测定方法。导热系数的受控因素包括地层岩性、孔隙率、含水率、温度以及各向异性。导热系数随地层岩性从大到小排列为海相碳酸盐岩、陆相碎屑岩、火成岩,变质岩导热系数与母岩和变质程度有关;同种岩层的导热系数随沉积过程延续或深度增加而增大;含水率对软弱岩石的导热系数影响较大,导热系数随含水率增大而增大,对孔隙度较大的岩层需进行饱水校正;不同岩性的导热系数随温度的变化较复杂,在应用中需结合实际地层考虑;由于结构面的存在,岩体的导热系数存在各向异性。导热系数的测定方法包括现场测试法、室内测试法、组分类型辨别法以及利用P波速度估算等。利用现场数据求解导热系数时常使用线热源模型和柱热源模型;室内测试法包括稳态测试法和非稳态测试法,分别应用于中低导热系数材料和高导热系数材料;对于组分类型辨别法,平行板式相分布的物体导热系数是各向不等的,热传导方向与平行板平面平行和垂直时分别具有最小和最大总体导热系数;对地下无法直接测量的地质单元,可利用P波速度估算导热系数。要得到准确的导热系数,须基于岩土体的导热系数范围和样品特征选取正确的测定方法。 相似文献
99.
青鳞鱼蛋白复合酶控制水解动力学模型的研究 总被引:1,自引:0,他引:1
在假设复合酶恒温控制水解动力学遵循内切酶限制水解动力学历程的前提下 ,采用实验方法求出了复合酶恒温控制水解动力学模型。结果表明 ,复合酶对青鳞鱼蛋白进行控制水解的动力学模型为 :R =(0 .315 4e0 - 0 .0 186s0 )exp(- 0 .170DH) ,DH =5 .882ln[1+(0 .0 5 36 2e0 /s0 -0 .0 0 32 )t];其酶失活常数Kd=0 .0 5 36min- 1;水解反应能够顺利进行的条件是 :e0 /s0 >c0 ,常数c0 =5 .90× 10 - 2 。验证实验证明 ,根据复合酶恒温控制水解动力学模型得到的理论DH与实际DH基本吻合 ,该动力学模型具有很强的实用价值。 相似文献
100.
The capacity of a gravity structure to counter seismically induced overturning can only be estimated with good accuracy using a dynamic analysis of the rotational (rocking) motion involving large displacement theory. Seismic assessment employing quasi‐static analysis can be overly conservative if the reserve capacity of this type of rocking structure to displace without overturning is not taken into account. It was revealed through dynamic testing on a shaking table that the overturning hazards of ground shaking are best represented by the peak displacement demand (PDD) parameter and that the vulnerability to overturning instability decreases with the increasing size of the object when the aspect ratio is held constant. This finding has important implications on the engineering of structures for countering moderate ground shaking in regions of low and moderate seismicity. Experimental data were validated and supplemented by computer simulations that involved generating artificial accelerograms of designated earthquake scenarios and non‐linear time‐history analyses of the overturning motions. Based on these simulations, fragility curves were constructed for estimating the probability of overturning for given levels of PDD and for different specimen dimensions. An expression was developed for estimating the level of PDD required to overturn rectangular objects of given dimensions for 5% probability of exceedance. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献