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31.
Decoupling of stalagmite-derived Asian summer monsoon records from North Atlantic temperature change during marine oxygen isotope stage 5d 总被引:2,自引:0,他引:2
Houyun Zhou Jianxin Zhao Chuan-Chou Shen Yuexing Feng Huazheng Guan Chen-Feng You 《Quaternary Research》2008,70(2):315-321
The Asian monsoon is an important component of the global climate system. Seasonal variations in wind, rainfall, and temperature associated with the Asian monsoon systems affect a vast expanse of tropical and subtropical Asia. Speleothem-derived summer monsoon variation in East Asia was previously found to be closely associated with millennial-scale change in temperature in the North Atlantic region between 75 and 10 ka. New evidence recovered from East Asia, however, suggests that the teleconnection between summer monsoon in East Asia and temperature change in the North Atlantic region may have significantly reduced during 120 to ~ 110 ka, a period directly after the full last interglaciation and corresponding roughly to marine oxygen isotope stage 5d. This reduction may be due to the low ice volume in the North Hemisphere at that time, which makes the millennial-scale change in temperature in the North Atlantic region less effective in influencing the Asian summer monsoon. This is important for investigating the mechanisms controlling the Asian summer monsoon and the paleoclimatic teleconnection between East Asia and the North Atlantic region, and for predicting monsoon-associated precipitation in East Asia under a global-warming trend. 相似文献
32.
该文首先采用合成分析的方法研究了江淮入梅前后大尺度大气环流的演变特征和西太平洋副热带高压西伸北跳的可能机制。研究结果表明, 江淮入梅前期的最显著的特征是:副热带高压首先在太平洋中部增强北跳, 而后向西扩展导致太平洋副高西部脊 (120°E) 的增强北跳。进一步分析表明, 在太平洋中部副热带高压的增强北跳和西伸之前, 副热带高压南侧ITCZ中对流和孟加拉湾北部的对流活动明显并且都经历了一次增强活跃过程, 这意味着热带ITCZ和孟加拉湾北部对流的异常活跃可能对副热带高压的增强北跳西伸产生影响。全球大气环流模式模拟结果表明, 赤道中太平洋ITCZ中对流异常活跃不仅可导致副热带高压的增强北移, 而且还可导致副热带高压西伸, 与诊断分析结果相一致。 相似文献
33.
基于临近相似性考虑的犯罪热点密度图预测准确性比较——以DP半岛街头抢劫犯罪为例 总被引:2,自引:5,他引:2
在无时空考虑的密度估计算法基础上,分别加入了案件点之间的时间临近相似性、空间临近相似性和时空临近相似性的考虑,利用DP半岛2006~2007年的街头抢劫犯罪数据为基础计算无时空临近相似性、时间临近相似性、空间临近相似性和时空临近相似性4种不同算法所得到的犯罪热点图,并以之预测2008年的街头抢劫。通过Natural breaks(Jenks)分级方法和等比例面积选取两种方式来划定热点区域进行预测并进行PAI指数得分比较,结果表明时空临近相似性的密度估计算方法在犯罪预测的优势比较显著。 相似文献
34.
Chen Fu Dongxiao Wang Lei Yang Yao Luo Fenghua Zhou Tilak Priyadarshana Jinglong Yao 《Ocean Dynamics》2018,68(6):689-699
Based on reanalysis data, we find that the Indian Ocean Dipole (IOD) plays an important role in the variability of wave climate in the equatorial Northern Indian Ocean (NIO). Significant wave height (SWH) in the equatorial NIO, especially over the waters southeast to Sri Lanka, exhibits strong interannual variations. SWH anomalies in the waters southeast to Sri Lanka correlate well with dipole mode index (DMI) during both summer and autumn. Negative SWH anomalies occur over the oceanic area southeast to Sri Lanka during positive IOD events and vary with different types of IOD. During positive prolonged (unseasonable) IOD, the SWH anomalies are the strongest in autumn (summer); while during positive normal IOD, the SWH anomalies are weak in both summer and autumn. Strong easterly wind anomalies over the southeast oceanic area of Sri Lanka during positive IOD events weaken the original equatorial westerly wind stress, which leads to the decrease in wind-sea waves. The longer wave period during positive IOD events further confirms less wind-sea waves. The SWH anomaly pattern during negative IOD events is nearly opposite to that during positive IOD events. 相似文献
35.
河北昌黎台地电阻率EW测道2017年6-8月出现快速下降变化,经检测,观测系统工作正常。通过环境调研和辅助资料对比分析,发现该变化与降雨和粉丝厂干扰有一定关系。采用褶积滤波法去掉降雨干扰,EW测道地电阻率仍为下降趋势,说明该下降变化不能完全用降雨来解释,不排除是地震前异常变化的可能。 相似文献
36.
37.
绿色农业是一种现代生产方式,具有广阔的发展前景。本文研究了绿色农业的含义、布局条件和地域类型,在分析我国绿色农业生产特点的基础上,探讨绿色农业发展对策。 相似文献
38.
回顾了日冕磁的研究历史,介绍了我们首镒提出的日冕磁场的微波诊断方法及其应用的带来的启迪,提出进一步开展日冕磁场及其相关研究的建议。 相似文献
39.
17 samples were collected from aeolian and lacustrine profiles within the environment sensitive zone of the Loess Plateau,
and an experimental method was established which is suitable for pollen extraction from aeolian sediment. A comparative study
of pollen dating was carried out using the accelerator mass spectrometry (AMS)14C dating of known age samples, and then an experiment with the pollen concentrates was performed. The results indicate that
pollen that has been deposited simultaneously with sediment in a stable environment can provide reliable ages. This technique
will provide a way of improving the chronological framework for the Loess Plateau since the late Pleistocene. TheI4c dating was combined with field investigations, and from the geological record within this zone, evidence was extracted of
four major monsoon precipitation changes during the transition from the late Pleistocene to Holocene.
Project supported by the National Natural Science Foundation of China (Grant Nos. 49894170, 49725308), Chinese Academy of
Sciences (Nos. KZ-951-A1-402& KZ-952-S1-419), and State Committee of Science and Technology of China. 相似文献
40.
Xiaoyi Ma Ci Song Chenghu Zhou 《International journal of geographical information science》2016,30(12):2401-2420
In the high-speed urbanization process of China, the urban population has been increasing significantly, leading to a high-density aggregation of population. However, the sharp increase in population density has not produced commensurate improvements in the road networks. On the contrary, the population increase induced a serious evacuation vulnerability, which cities experience during various hazards and catastrophic events. Therefore, research on evacuation vulnerability is important to urban planning. To assess the evacuation vulnerability, the optimal and worst scenarios should be considered because all possible evacuation plans occur between these extremes. However, most previous evacuation vulnerability studies are based on the worst-case scenario, only providing an upper bound of a potential evacuation assessment. To provide a more comprehensive theoretical basis for decision-makers to understand the consequences caused by all possible evacuations, this paper proposes an optimal evacuation vulnerability assessment model that provides the lower bound on potential evacuation difficulties. The model is solved by a stepwise spreading algorithm based on Graph Theory. Subsequently, to evaluate the effectiveness of the model, the study adopts the model to assess the evacuation capability of different road network topologies. A comparison with previous research was performed. The model was demonstrated in an application to the South Luogu Alley of Beijing, China. The significance of this paper is that the combination of our model with previous research may provide a more complete theoretical basis for an evacuation vulnerability assessment. 相似文献