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921.
The Gulf of Nicoya, an estuary on the Pacific coast of Central America, contains a large population of the portunid crab Callinectes arcuatus. Results of a 12 month survey indicated that spawning activity occurs throughout the year, but with a distinct peak during the five-month dry season (December-April). Mature females were most prevalent in the upper regions of the gulf during the rainy season and appeared to migrate to the lower gulf to spawn during the dry season. Patterns of spawning and apparent migration differed from those reported in an earlier study of C. arcuatus along the Pacific coast of Mexico. 相似文献
922.
基于昌吉地区7个气象站1961-2020年降水量资料,计算昌吉地区作物生长季标准化降水指数(SPI-7)。运用趋势分析法、M-K突变检验法和小波分析法探究了昌吉地区作物生长季SPI-7指数的年际和年代变化特征;在此基础上分析了作物生长季干旱的站次比和干旱强度的年际变化,并结合该区实际发生的旱灾对SPI进行了验证。结果表明:1961—2020年昌吉地区作物生长季标准化降水指数以0.08/10 a的速率呈微弱的正趋势(变湿),在年代变化趋势中呈现出变干-变湿-变干的变化波动, 1981年标准化降水指数由低到高突变;干旱强度呈增加趋势,干旱发生的区域面积有轻微减少的趋势;干旱强度在全区范围内主要为轻旱和中旱等级,并表现为全域性干旱和区域性干旱;空间分布上看干旱率最高区域在东部地区,轻旱主要集中在东部,中旱、重旱和特旱集中在西部地区,干旱强度大的区域大致分布在西部地区;在周期性变化方面,SPI指数存在着6年、9年、16年周期震荡;历史旱灾与SPI指数干旱评价结果吻合率较高,SPI指数在昌吉地区作物生长季的干旱监测与分析中具有较好的实用性。 相似文献
923.
IMPACTS OF CLIMATE CHANGE ON CROPPING SYSTEM AND ITS IMPLICATION FOR AGRICULTURE IN CHINA 总被引:1,自引:0,他引:1
Wang Futang 《Acta Meteorologica Sinica》1997,11(4):407-415
Based on the analyses on amplitudes of historical variation of temperature and precipitation inthe past 500 years and latest 100 years,according to the regional climate change scenarios forChina estimated by composite GCM,the potential impacts of climate change on cropping systemsin China in future are simulated and assessed using the cropping system model developmentspecially for the Chinese cropping patterns.It is shown that under the projected future climatechange by 2050 the most parts of the present double cropping area would be replaced by thedifferent triple cropping patterns while the current double cropping area would shift towards thecentral part of the present single cropping area.More explicitly,the northern boundary of triplecropping area would shift from its current border at the Changjing River to the Huanghe River,ashift of more than 5 degrees of latitude.And the shift of multiple cropping areas leads to asignificant decrease of single cropping area.Furthermore,considering the changes mentioned above in combination with the likely negativebalance of precipitation and evapotranspiration and,therefore,increase of moisture stress(i.e.less water availability),as well as the possible increase of heat stress disaster and decrease of LGS(length of growing season),the potential implication of climate change for agriculture in China arealso analyzed roughly in this paper.As a result,however,it is still very difficult to reach a specific conclusion that the futureclimate change will he favorable or unfavorable to farm in China because of the complicated Chinesefarming patterns,the complex-various social and economic environment of agriculturaldevelopment and,especially,a great scientific uncertainties in the investigation/prediction ofclimate change. 相似文献
924.
该文以长江三峡地区6个站1961-1994年10月-1月的逐日降水量来确定该地区发生区域性强降水的雨日,用同期的历史天气图分析产生区域性强降水的原因,影响系统和环流形势2,归纳出长江三峡地区产生区域性强降水的6类环流型,并进行逐日反查,概括出两类环流型产生区域性强降水的预报指标。 相似文献
925.
通过对 196 3- 1999年间广西非汛期 (10月至次年 3月 )暴雨天气过程这一异常天气事件的时间分布及其主要影响系统的分析得出 :广西非汛期异常暴雨天气事件的发生是中、低纬天气系统相互作用在广西地区的反映。关注这一特征 ,对提高广西非汛期异常暴雨天气的预报水平具有参考作用。 相似文献
926.
南极气候变化的季节特征 总被引:1,自引:3,他引:1
利用1962-1993年南极16站地面至30hPa10个标准层上月平均温度,南极臭氧总量以及2800MHZ太阳通量资料,采用最大熵功率变方法,研究了各季中月南极诸高度气候的线性趋势变化,熵谱特征及其可能原因。 相似文献
927.
928.
Seasonal transition of summer rainy season over indochina and adjacent monsoon region 总被引:8,自引:0,他引:8
Jun Matsumoto 《大气科学进展》1997,14(2):231-245
The mean onset and withdrawal of summer rainy season over the Indochina Peninsula were investigated using 5-day averaged rainfall data (1975-87). The mean seasonal transition process during onset and retreat phases in Indochina, India and the South China Sea is also examined using 5-day mean OLR (1975-87) and 850 hPa wind (1980-88) date. It was found that the onset of summer rainy season begins earlier in the inland region of Indochina (Thailand) in late April to early May than in the coastal region along the Bay of Bengal. This early onset of rainy sea-son is due to pre-monsoon rain under the mid-latitude westerly wind regime. The full summer monsoon circulation begins to establish in mid-May, causing active convective activity both over the west coast of Indochina and the cen-tral South China Sea. In case of withdrawal, the earliest retreat of summer rainy season is found in the central northern part of Indochina in late September. The wind field, on the other hand, already changes to easterlies in the northern South China Sea in early September. This easterly wind system covers the eastern part of Indochina where post-monsoon rain is still active. In late October, the wind field turns to winter time situation, but post monsoon rain still continues in the southern part of the Indochina Peninsula until late November 相似文献
929.
930.
5-羟色胺刺激长牡蛎排放精卵在四倍体诱导中的应用 总被引:4,自引:0,他引:4
本文报道了用 5 羟色胺催产出的长牡蛎精、卵 ,人工授精后诱导四倍体的实验结果 .结果表明 :在 2 6℃水温条件下 ,受精后 7min ,用 0 .5mg/dm3细胞松弛素B处理2 5min ,获得长牡蛎的胚胎四倍体 ,其诱导率为 1 6.7%,D形幼虫孵化率为 2 7.0 %;诱导效果优于采用常规解剖法 .注射 5 羟色胺刺激长牡蛎亲贝排放精、卵的有效浓度分别为 1× 1 0 -6 ~ 1× 1 0 -2 mol/dm3和 1× 1 0 -5 ~ 1× 1 0 -3mol/dm3. 相似文献