全文获取类型
收费全文 | 1797篇 |
免费 | 572篇 |
国内免费 | 1604篇 |
专业分类
测绘学 | 50篇 |
大气科学 | 2172篇 |
地球物理 | 267篇 |
地质学 | 332篇 |
海洋学 | 786篇 |
天文学 | 9篇 |
综合类 | 137篇 |
自然地理 | 220篇 |
出版年
2024年 | 28篇 |
2023年 | 62篇 |
2022年 | 96篇 |
2021年 | 117篇 |
2020年 | 150篇 |
2019年 | 146篇 |
2018年 | 122篇 |
2017年 | 130篇 |
2016年 | 124篇 |
2015年 | 119篇 |
2014年 | 164篇 |
2013年 | 201篇 |
2012年 | 182篇 |
2011年 | 180篇 |
2010年 | 166篇 |
2009年 | 170篇 |
2008年 | 173篇 |
2007年 | 206篇 |
2006年 | 196篇 |
2005年 | 176篇 |
2004年 | 133篇 |
2003年 | 134篇 |
2002年 | 118篇 |
2001年 | 110篇 |
2000年 | 104篇 |
1999年 | 75篇 |
1998年 | 67篇 |
1997年 | 66篇 |
1996年 | 50篇 |
1995年 | 50篇 |
1994年 | 47篇 |
1993年 | 26篇 |
1992年 | 25篇 |
1991年 | 17篇 |
1990年 | 7篇 |
1989年 | 11篇 |
1988年 | 6篇 |
1987年 | 2篇 |
1986年 | 2篇 |
1985年 | 6篇 |
1984年 | 3篇 |
1983年 | 3篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1977年 | 1篇 |
排序方式: 共有3973条查询结果,搜索用时 15 毫秒
101.
102.
Gert Finger Reinhold J. Dorn Alan W. Hoffman Hamid Mehrgan Manfred Meyer Alan F. M. Moorwood Joerg Stegmeier 《Experimental Astronomy》2002,14(2):117-127
Three different methods are presented to subtract thermal drifts and low-frequency noise from the signal of infrared array.
The first is dead pixels with open Indium bumps, the second is reference output as implemented on the Hawaii2 multiplexer,
and the third is dark pixels to emulate reference cells having a capacity connected to the gate of the unit cell field-effect
transistor (FET). The third method is the most effective and yields a reduction in readout noise from15.4–9.4 erms. A novel
method will be described to extend this readout technique to the Aladdin 1 K × 1 K InSb array.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
103.
Modelling observed and future runoff from a glacierized tropical catchment (Cordillera Blanca, Perú)
Monthly runoff from the 34.3% glacierized tropical catchment of Llanganuco in the tropical Cordillera Blanca, Perú, is successfully simulated and compared with a measured 44 year time series. In the investigation area, the climate is characterized by all-year round homogenous temperature conditions and a strong variability in air humidity and moisture content of the atmosphere. Thus, contrary to the mid latitudes, the seasonal variation in glacier melt strongly depends on moisture-related variables, rather than on air temperature. The here presented ITGG-2.0-R model aims for these requirements. The lack of moisture-related input data other than precipitation demands for an intermediate calibration step. Net shortwave radiation, the emissivity of the atmosphere and a sublimation/melt ratio are related to precipitation amounts. Runoff is well simulated and correlates with the measured record with r2 = 0.76. Seasonally obtained r2 are only slightly smaller. On a long-term, the cumulative deviation is minor, and the mean annual cycle of runoff is reproduced rather well (r2 = 0.99). Based on four different IPCC climate change scenarios, future runoff is simulated. All runoff scenarios are modelled for the respective steady-state glacier extent. This leads to a reduction in the glacier size and a decreased amount of glacier melt. On the other hand, direct runoff increases due to larger glacier free areas. Consequently, mean annual runoff remains almost unchanged, but the seasonality intensifies considerably with more runoff during the wet and less runoff during the dry season. 相似文献
104.
西安市一次短时强风暴天气过程分析 总被引:1,自引:0,他引:1
1997年7月28日西安市发生一次强风暴天气过程,分析发现这次过程主要受秦岭山脉地形、地面弱冷空气南下和副高增强西进的共同影响而造成;强风暴发生在地面“人”字形辐合线交点处;由多单体雷暴演变成超级单体雷暴,在雷达回波中呈“S”型。秦岭山脉北侧边缘的对流活动是此类天气前期的一个明显征兆。 相似文献
105.
利用现场可编程门阵列(FPGA)的内部资源,在FPGA中实现了高精度时间间隔测量系统的设计。 相似文献
106.
A group of coenocytic marine algae differs from higher plants,whose totipotency depends on an intact cell(or protoplast).Instead,this alga is able to aggregate its extruded protoplasm in sea water and generate new mature individuals.It is thought that lectins play a key role in the aggregation process.We purified a lectin associated with the aggregation of cell organelles in Bryopsis hypnoides.The lectin was ca.27 kDa with a pI between pH 5 and pH 6.The absence of carbohydrate suggested that the lectin was ... 相似文献
107.
Amphioxus, a cephalochordate, is an important model fish for studies in evolution and comparative biology. A successful cell
culture from amphioxus tissues in vitro would help understanding some basic issues. To determine the optimal culture conditions for proliferation of amphioxus cells,
primary cultures were initiated from buccal cirri, tail, gill, gut and metapleural fold of amphioxus Branchiostoma belcheri tsingtauense. The media tested were L-15, F-12, M 199, MEM, DMEM, PRMI 1640 and LDF, each was supplemented with 20% fetal bovine serum.
The optimal conditions include tail tissue cultured in L-15 or F-12 with supplement of 20% FBS and 1.5% NaCl at about 25°C.
Supported by Doctoral Initial Fund of Ludong University (No.43304) 相似文献
108.
The interannual variability of near-coastal eastern North Pacific tropical cyclones is described using a data set of cyclone tracks constructed from U.S. and Mexican oceanic and atmospheric reports for the period 1951-2006. Near-coastal cyclone counts are enumerated monthly, allowing us to distinguish interannual variability during different phases of the May-November tropical cyclone season. In these data more tropical cyclones affect the Pacific coast in May-July, the early months of the tropical cyclone season, during La Niña years, when equatorial Pacific sea surface temperatures are anomalously cool, than during El Niño years. The difference in early season cyclone counts between La Niña and El Niño years was particularly pronounced during the mid-twentieth century epoch when cool equatorial temperatures were enhanced as described by an index of the Pacific Decadal Oscillation. Composite maps from years with high and low near-coastal cyclone counts show that the atmospheric circulation anomalies associated with cool sea surface temperatures in the eastern equatorial Pacific are consistent with preferential steering of tropical cyclones northeastward toward the west coast of Mexico. 相似文献
109.
CLIMATIC ANALYSIS OF IMPACTS OF THE TROPICAL CONVECTION IN WESTERN PACIFIC ON WESTERN PACIFIC SUBTROPICAL HIGH’S SHORT-TERM SCALES DURING BOREAL SUMMER* 下载免费PDF全文
Based on the multi-year average NCEP/NCAR reanalysis data and NOAA's OLR data,the climatic characteristics of the tropical convection in tropical western Pacific and Indian Oceans as well as its relationship with western Pacific subtropical high (WPSH) is shown as follows:on short-term scales,the tropical convection that has significant influence on western Pacific high's latitudinal movement is located in the area of the South China Sea to the Philippines,which is the 2-day precursor prior to WPSH's latitudinal fluctuation,that is,WPSH is shifting to north 2 days after the tropical convection becomes more active,and vice versa.Moreover,the tropical convection has less effect on WPSH's longitudinal movement. 相似文献
110.
雷小途 《热带气象学报(英文版)》2001,7(1):53-62
To have a clearer picture of mechanisms responsible for the deviation of tropical cyclone (to be
simplified as TC hereafter) tracks, the current work assumes the TC as a circular vortex with a radius of R. A
general motion equation of TC is then determined by averaging its horizontal motion equation over the sentire
region of TC. In the meantime, with the moving track of TC assumed as a characteristic arc, the curvature equation
is derived for the track of movement and patterns of its deviation due to TC structure and variation are
discussed. The result shows that the scale, size, maximum wind speed and radius are factors causing the deviation
of TC tracks. In addition, asymmetric structure of TC is also important for the deviation of tracks. The results,
achieved with hypothesis, agree with facts in some cases but disagree with them in others, which are to be
verified with more observations or numerical simulations. 相似文献