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971.
辽西建昌盆地九佛堂组珍稀化石层的划分与对比 总被引:1,自引:0,他引:1
为研究热河生物群的鸟类、爬行类和被子植物的早期演化、辐射迁移、生物多样性及其协同进化,笔者在建昌盆地测制了九佛堂组剖面,并系统采集了以珍稀化石为重点的生物化石。结合前人研究成果,将九佛堂组自下而上分为第一段至第三段,其中九佛堂组第一段西店层含鸟类、爬行类和龟类等珍稀化石,尚见介形类化石Cypridea decorosa,C.jianchanensis,Yumenia jianchanensis,Limnocypridea slundensis,L.levigata,L.rara等,表明该层的介形类化石与喀左九佛堂小孤山—烧锅地剖面及朝阳县波罗赤小北山—黄道营子剖面的九佛堂组第一段下部介形类化石组合面貌基本一致,其所在层位亦应相当。 相似文献
972.
沪宁高速公路大雾及气象要素特征分析 总被引:3,自引:0,他引:3
利用2006年6月-2009年5月沪宁高速公路AWM自动气象站资料,研究了不同类型大雾持续时间、能见度变化及其出现过程中风、湿度变化特征。结果表明,有超过50%的大雾会发展成浓雾;大雾持续时间以平流雾最长,辐射雾最短;67.6%的大雾在长时间低能见度之前会出现类似"象鼻"形的突变前兆,这可能与地理环境有关;大雾过程中风向以东风和西风为主,锋面雾有部分为偏南风;平流雾发生时风速较辐射雾和锋面雾大,锋面雾发生时风速较多为静风,结束时风速快速增大;平流雾发生时相对湿度多有突变,而辐射雾、锋面雾的相对湿度以渐变为主。 相似文献
973.
Chemical characteristics of haze during summer and winter in Guangzhou 总被引:33,自引:0,他引:33
Ji-Hua Tan Jing-Chun Duan Duo-Hong Chen Xin-Hua Wang Song-Jun Guo Xin-Hui Bi Guo-Ying Sheng Ke-Bin He Jia-Mo Fu 《Atmospheric Research》2009,94(2):238-245
Airborne particles were collected with a 10-stage MOUDI and a PM10 sampler in Guangzhou, China, during both haze and normal days in the summer of 2002 and 2003, and winter 2002. The characteristics of PAHs, organic carbon, elemental carbon and water-soluble inorganic ions were studied under four periods (summer normal, summer haze, winter normal and winter haze). In this study, secondary pollutants (OC, SO42−, NO3− and NH4+) were the major chemical components and appeared to show a remarkably rapid increase from normal to haze days. The particle mass size distributions were bimodal and dominated by fine particles in haze days. A significantly higher OC/EC ratio was found in haze days (3.2–4.7) compared to normal days (1.8–2.8), indicating secondary organic aerosol formation might be significant during haze days. Correlation analysis between visibility and chemical species showed that the major scattering species were TC (total carbon) and sulfate in normal days and nitrate and TC in haze days, respectively. Simultaneously, correlation analysis between visibility and meteorological factors demonstrated that visibility increased with both temperature and wind speed, while it decreased with relative humidity. Furthermore, the relatively higher value of IcdP/(BghiP + IcdP) and the low value of Cmax, CPI, and BghiP/BeP in winter haze could be due to the growth of motor vehicle usage and energy consumption in winter. 相似文献
974.
用SA雷达产品对京西三次局地暴雨落区形成的精细分析 总被引:6,自引:3,他引:3
利用新一代Doppler雷达各种探测产品,对2006年6月底至7月上旬北京西郊香山、石景山、门头沟一带落区相同的三次局地暴雨和大暴雨过程,进行精细分析和研究.重点分析雷达探测产品对落区在同一地点形成的短时临近影响系统和指示意义.研究表明,发生在北京西郊山前、落区相同的三次局地暴雨和大暴雨,其雷达回波发展和演变形式各不相同.但三次过程强降雨前,近地面平原东南风和边界层偏西风的垂直风廓线结构在地形作用下对暴雨落区形成的影响是一致的:近乎与山脉垂直的平原近地面东南风长时间(6小时左右)维持,增加山前局地近地面温湿条件,并在北京西郊山脉阻挡下,形成山前近地面局地辐合和强迫抬升.山顶附近边界层的偏西风为近地面空气强迫抬升后在边界层的后卷辐散提供了有利条件.研究还显示,落区附近单体风暴、逆风区辐合带、中气旋等中小尺度回波系统的活动和发展,是暴雨落区形成的重要因素. 相似文献
975.
976.
东北黑土区容许土壤流失量研究(英文) 总被引:1,自引:0,他引:1
Soil loss tolerance(T) is the maximum rate of annual soil erosion that is tolerated and still allows a high level of crop productivity to be sustained economically and indefinitely.In the black soil region of Northeast China,an empirically determined,default T value of 200(t/km2?a) is used for designing land restoration strategies for different types of soils.The ob-jective of this study was to provide a methodology to calculate a quantitative T for different black soil species.A field investigation was conducted to determine the typical soil profiles of 21 black soil species in the study area and a quantitative methodology based on a modified soil productivity index model was established to calculate the T values.These values,which varied from 68 t/km2?a to 358 t/km2?a,yielded an average T value of 141 t/km2?a for the 21 soil species.This is 29.5% lower than the current national standard T value.Two significant factors that influenced the T value were soil thickness and vulnerability to erosion.An ac-ceptable reduction rate of soil productivity over a planned time period of 1% is recommended as necessary for maintaining long-term sustainable soil productivity.Compared with the cur-rently used of regional unified standard T value,the proposed method,which determines T using specific soil profile indices,has more practical implications for effective,sustainable management of soil and water conservation. 相似文献
977.
Xu Zhao-yong Duan Yong-kang Wang Bin Hu Yi-li Yang Run-hai Xu Jun Zhao Jin-ming 《地震科学(英文版)》2004,17(1):138-149
By studying the pile-formula and stress-wave methods (e.g., CASE method), the authors propose a new method for testing piles using the single-impact energy and P-S curves. The vibration and wave figures are recorded, and the dynamic and static displacements are measured by different transducers near the top of piles when the pile is impacted by a heavy hammer or micro-rocket. By observing the transformation coefficient of driving energy (total energy), the consumed energy of wave motion and vibration and so on, the vertical bearing capacity for single pile is measured and calculated. Then, using the vibration wave diagram, the dynamic relation curves between the force (P) and the displacement (S) is calculated and the yield points are determined. Using the static-loading test, the dynamic results are checked and the relative constants of dynamic-static P-S curves are determined. Then the subsidence quantity corresponding to the bearing capacity is determined. Moreover, the shaped quality of the pile body can be judged from the formation of P-S curves. 相似文献
978.
分析了2004年12月以来全球7级以上强震和中国5级以上地震的同震效应特征,当震中距较小时,同震应变阶似单纯的阶跃;而当震中距较大时,阶跃具有脉冲的形式,曲线有一个往返变化。初步总结了不同震中距时,竖直摆倾斜记录地震波动的能力。 相似文献
979.
Seasonal changes in the abundance and composition of plant pigments in particulate organic carbon in the lower Mississippi and Pearl Rivers 总被引:1,自引:0,他引:1
Plant pigments in particulate organic carbon were examined in the lower Mississippi and Pearl Rivers (U.S.), along with physical
variables and nutrients to study seasonal changes in the abundance and composition of phytoplankton. Water samples were collected
monthly from September 2001 to August 2003 in the lower Mississippi River (MR; no samples were taken in February 2002) and
from August 2001 to July 2003 in the Pearl River (PR). High concentrations of total suspended solids (TSS), nutrients, and
chlorophylla (chla; dominated by diatoms) were observed in the lower MR. The smaller blackwater PR was characterized by lower nutrients and
chla, higher ultraviolet absorbance, and a phytoplankton biomass dominated by chlorophytes. Chla concentrations in the lower MR was high in summer low-flow periods and also during interims of winter and spring, and did
not couple with physical variables and nutrients, likely due to a combination of in situ production and inputs from reservoirs,
navigation locks and oxbow lakes in the upper MR and Missouri River. Chla concentrations in the PR was only high in summer low-flow periods and were controlled by temperature and concentrations of
chromophoric dissolved organic matter 9CDOM). The high, diatom-dominated phytoplankton biomass in the lower MR was likely
the result of decreasing TSS (increased damming in the watershed) and increasing nutrients (enhanced agricultural runoff)
over the past few decades. Lower phytoplankton biomass (dominated by chlorophytes) in the PR was likely linked with intense
shading by CDOM and lower availability of nutrient inputs. An increase in the relative importance of phytoplankton biomass
in large turbid rivers, such as the MR, could have significant effects on the age and lability of riverine organic matter
entering the ocean, the stoichiometric balance of nutrients delivered to coastal margins, and the sequestration of atmospheric
CO2 in these dynamic regions. 相似文献
980.
Analysis and high-resolution modeling of a dense sea fog event over the Yellow Sea 总被引:12,自引:0,他引:12
Gang Fu Jingtian Guo Shang-Ping Xie Yihong Duan Meigen Zhang 《Atmospheric Research》2006,81(4):293-303
A ubiquitous feature of the Yellow Sea (YS) is the frequent occurrence of the sea fog in spring and summer season. An extremely dense sea fog event was observed around the Shandong Peninsula in the morning of 11 April 2004. This fog patch, with a spatial scale of several hundreds kilometers and lasted about 20 h, reduced the horizontal visibility to be less than 20 m in some locations, and caused a series of traffic collisions and 12 injuries on the coastal stretch of a major highway. In this paper, almost all available observational data, including Geostationary Operational Environmental Satellite (GOES)-9 visible satellite imagery, objectively reanalyzed data of final run analysis (FNL) issued by the National Center for Environmental Prediction (NCEP) and the sounding data of Qingdao and Dalian, as well as the latest 4.4 version of Regional Atmospheric Modeling System (RAMS) model, were employed to investigate this sea fog case. Its evolutionary process and the environmental conditions that led to the fog formation were examined by using GOES-9 visible satellite imagery and sounding observations. In order to better understand the fog formation mechanism, a high-resolution RAMS modeling of 4 km × 4 km was designed. The modeling was initialized and validated by FNL data. A 30-h modeling that started from 18 UTC 10 April 2004 reproduced the main characteristics of this fog event. The simulated lower horizontal visibility area agreed reasonably well with the sea fog region identified from the satellite imagery. Advection cooling effect seemed to play a significant role for the fog formation. 相似文献