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991.
Summary A novel multi-timescale analysis method, Empirical Mode Decomposition (EMD), is used to diagnose the variation of the annual
mean temperature data of the global, Northern Hemisphere (NH) and China from 1881 to 2002. The results show that: (1) Temperature
can be completely decomposed into four timescales quasi-periodic oscillations including an ENSO-like mode, a 6–8-year signal,
a 20-year signal and a 60-year signal, as well as a trend. With each contributing ration of the quasi-periodicity discussed,
the trend and the 60-year timescale oscillation of temperature variation are the most prominent. (2) It has been noticed that
whether on century-scale or 60-year scales, the global temperature tends to descend in the coming 20 years. (3) On quasi 60-year
timescale, temperature abrupt changes in China precede those in the global and NH, which provides a denotation for global
climate changes. Signs also show a drop in temperature in China on century scale in the next 20 years. (4) The dominant contribution
of CO2 concentration to global temperature variation is the trend. However, its influence weight on global temperature variation
accounts for no more than 40.19%, smaller than those of the natural climate changes on the rest four timescales. Despite the
increasing trend in atmospheric CO2 concentration, the patterns of 20-year and 60-year oscillation of global temperature are all in falling. Therefore, if CO2 concentration remains constant at present, the CO2 greenhouse effect will be deficient in counterchecking the natural cooling of global climate in the following 20 years. Even
though the CO2 greenhouse effect on global climate change is unsuspicious, it could have been excessively exaggerated. It is high time to
re-consider the trend of global climate changes. 相似文献
992.
Summary The cut-off lows (COLs) during the period from June to August 1998 leading to the record flood in Northeast Asia, especially
in Northeast China, has been investigated in this paper. The results are as follows: the blocking highs benefited significantly
the formation and maintenance of COLs over Northeast China; an obvious frontogenesis zone existed in Northeast China and it
implies that baroclinity played an important role in the initiation of COLs, especially in middle and upper troposphere; the
maxima of the potential vorticity anomaly were located in the upper troposphere, then extended downwards to the middle and
the lower troposphere. The pronounced interaction between systems in upper-middle and low troposphere can be revealed; the
moisture supply was from South China, and even from East China Sea and South China Sea. The strong southerly current transported
very rich moisture to Northeast China. The maximum of the convergence of moisture flux was below 850 hPa. Obvious interaction
between the middle and lower latitude systems was found in the study. Also, the summer monsoon showed significant impacts
on the sustained heavy rainfalls related with the COLs over Northeast China; the upward motion could be caused by the lifting
of the large scale dynamic forcing and there was no obvious releasing of latent heating in the upper-middle troposphere. The
cold dome in the COLs was quite different both from the warm core in tropical cyclone and from the weaker warm core in Meiyu
(Baiu) front low. The calculation of vorticity budget shows that both the horizontal advection term and horizontal divergence
term contributed importantly to the maintenance and the strengthening of positive relative vorticity. Finally, the complex
dynamical characteristics regarding the COLs are discussed and further investigation is proposed. 相似文献
993.
Seasonal Transition Features of Large-Scale Moisture Transport in the Asian-Australian Monsoon Region 总被引:18,自引:0,他引:18
Using NCEP/NCAR reanalysis data for the period of 1957-2001, the climatological seasonal transition features of large-scale vertically integrated moisture transport (VIMT) in the Asian-Australian monsoon region are investigated in this paper. The basic features of the seasonal transition of VIMT from winter to summer are the establishment of the summertime "great moisture river" pattern (named the GMR pattern) and its eastward expansion, associated with a series of climatological events which occurred in some "key periods", which include the occurrence of the notable southerly VIMT over the Indochina Peninsula in mid March, the activity of the low VIMT vortex around Sri Lanka in late April, and the onset of the South China Sea summer monsoon in mid May, among others. However, during the transition from summer to winter, the characteristics are mainly exhibited by the establishment of the easterly VIMT belt located in the tropical area, accompanied by some events occurring in "key periods". Further analyses disclose a great difference between the Indian and East Asian monsoon regions when viewed from the meridional migration of the westerly VIMT during the seasonal change process, according to which the Asian monsoon region can be easily divided into two parts along the western side of the Indochina Peninsula and it may also denote different formation mechanisms between the two regions. 相似文献
994.
Four comparative experiments and some supplementary experiments were conducted to examine the role of meridional wind stress anomalies and heat flux variability in ENSO simulations by using a high-resolution Ocean General Circulation Model (OGCM). The results indicate that changes in the direction and magnitude of meridional wind stress anomalies have little influence on ENSO simulations until meridional wind stress anomalies are unrealistically enlarged by a factor of 5.0. However, evidence of an impact on ENSO simulations due to heat flux variability was found. The simulated Nino-3 index without the effect of heat flux anomalies tended to be around 1.0° lower than the observed, as well as the control run, during the peak months of ENSO events. 相似文献
995.
996.
997.
天津市地震局于2015年通过首都圈预警示范工程项目建设,完成地震预警信息服务网络建设,并选取6所学校安装地震预警信息发布装置,提供地震预警信息示范服务,但由于信息发布装置安装复杂且价格偏高,在一定程度上影响终端设备的普及,制约地震预警信息社会化服务进程。同时,已有终端设备如同黑箱,不利于二次开发应用,存在安全隐患,影响服务质量。因此,天津市地震局积极推进基于NB-IoT技术的地震预警信息发布终端设备研制,实现低成本、低功耗、低延时目标及地震预警信息社会化服务。 相似文献
998.
999.
滇西北红牛—红山铜矿床是义敦—沙鲁里岛弧上与晚白垩纪中酸性侵入体有关的典型的斑岩-矽卡岩-热液型铜矿床。本文通过对其成矿地质背景、矿床地质特征、矿化富集规律及成矿模式、矿床地球物理和地球化学特征的综合研究,建立了红牛—红山铜矿床的"大比例尺地质填图和综合研究+重力+激电和高精度磁测+土壤化探测+工程验证"组合勘查技术方法、"燕山晚期石英二长斑岩+接触带矽卡岩和层间破碎带矽卡岩+重力低异常+高磁异常+高视极化率和低视电阻率异常+Cu-Mo-Pb-Zn-Ag-Au等元素综合异常"组合勘查模型。地质调查研究确定矿床成矿地质体和找矿地质体、矿化类型及其空间分布规律,建立矿床"四位一体"的成矿模式和区域-矿区地质找矿模型。区域中小比例尺的土壤化探测量确定区域找矿靶区,大比例尺土壤化探测量进一步缩小找矿靶区,逼近矿体赋存部位。矿区处于1∶5万土壤测量圈定的Cu-Pb-Zn-Mo-Au-Ag元素综合高异常区,1∶2.5万土壤测量圈出Cu-Pb-Zn-Ag-W元素综合异常面积较大、强度高、浓集中心明显、元素套合好,与矿区铜(铁)矿体赋存区域异常相对应。区域重力低异常区和正磁异常强度高区域是重要的找矿靶区,矿区大比例尺磁异常和激电异常区确定了矿体的空间位置和产状;矿区铜(铁)矿体赋存区为低视电阻率、高视极化率异常区,高精度磁测表现为正负磁异常相伴。矿区地质-地球化学-地球物理综合勘查模型对矿区深边部找矿起到重要的指导作用。 相似文献
1000.
The short-term evolution of spheroidal galaxies has been explored by S. Chandrasekhar et al. and G. S. Sunder et al. In this paper, we study their long-term evolution with Laskar's method of frequency analysis. The main new results are as follows: (1) There exists a unique equilibrium, which is spherically symmetric. This equilibrium has a critical linear stability. (2) Generally speaking, the semi-axes exhibit quasiperiodic or nearly quasi-periodic (in a time scale longer than a Hubble time) oscillations around the radius of the above-mentioned equilibrium, so the equilibrium is practically stable. (3) There are cases in which one of the semi-axes tends fast to zero while the other to some finite value. The limit state is generally planar rather than linear, i.e. it is the symmetric semi-axis that tends to zero. This implies that some disk galaxies may have originated from spheroidal pregalaxy material. 相似文献