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991.
A linear regression analysis of 28 selected tide-gauge stations of the Zhujiang Estuary shows that there has been a tendency of local sea level rise at a rate of 2.028 mm per year. The origin of the variation is significantly attributed to the local tectonic movement of discrepant fault-block. Based on this, four types of relative local sea level changes are classified. According to calculation, half of the fertile land, or 800 km2 of the delta plain will have been submerged by sea water by about 2040. This will yield a significant influence on the economic construction and human activities. 相似文献
992.
按内波假说的观点,讨论了典型板内地震即中国大陆地震的成因机制,认为造成地壳厚度分化的内波运动依靠地壳厚度差异中蕴藏的重力位能,推动地壳物质运动形成各种类型的板内地震。研究了全球地震活动的纬度分布特点以及地震活动与潮汐作用及大陆分布的联系,指出:外动力地质作用强烈的大陆因剥蚀、搬运和沉积以及负载重分布,使大陆地区始终达不到重力均衡,成为地壳运动的活动区,因而陆壳“地震能量发射强度”曲线具有类似于潮汐剪应力纬度分布的两极衰减、南北对称的特性。文中还探讨了深震及和达—贝尼奥夫带的成因,克服了用俯冲板块解释这一现象的困难。 相似文献
993.
Isao Hirota 《山地科学学报》2017,14(6):1058-1064
Bamboos are widely distributed in mainland Southeast Asia and have abundant biomass. They are characterized by prolonged vegetative growth and semelparity. Where bamboos are dominant, their synchronous flowering and death has a major impact on forest vegetation. Although the small-scale dynamics of this process have become clearer in recent years, the history, geographical scale and synchronicity of bamboo flowering over broad areas remains unknown. This study focused on the flowering history of six bamboo species, Bambusa tulda, Cephalostachyum virgatum, Dendrocalamus hamiltonii, Dendrocalamus membranaceus, Indosasa sinica and Oxytenanthera parvifolia, over 40 years across a broad area of northern Laos. We also examined the synchronicity of flowering in D. membranaceus. We visited 49 villages in northern Laos and surveyed knowledgeable inhabitants about bamboo flowering history. The timing, scale and synchronicity of gregarious flowering varied among species. D. hamiltonii and D. membranaceus showed higher flowering synchronicity than other species. All the species except I. sinica had both sporadic and gregarious flowering traits, and showed conspicuous variability in their flowering scale. The flowering bamboo population at two gregarious flowering sites for D. membranaceus was surveyed. While this species had the highest synchronicity in this study, its synchronicity was lower than other species in previous studies worldwide. We found that the gregarious flowering of bamboos in northern Laos over the last 40 years showed lower synchronicity than bamboo flowering reported in other areas of the world. The historical dynamics and scale of bamboo flowering must be further clarified to understand the vegetation composition of this area. 相似文献
994.
Wetland plant communities in the plateau lakes of Yunnan Province, China, have decreased significantly over the past decades. To better understand this degradation, we analyzed the processes and characteristics of changes in wetland plant communities in two of the largest lakes in Yunnan Province, Dianchi and Erhai lakes. We collected records of native and alien plant communities in the two lakes from literature published from the 1950s to current period. We calculated plant community types and their area in some historical periods when related data were reported, and analyzed the relationship between changes in plant communities and water pollution. In Dianchi Lake, 12 community types of native plant communities, covering over 80% of the surface in the 1950s and 1960s, were reduced to four types covering 2.4% by the late 2000s. Alien plant communities started to appear in the lake in the late 1970s, and have since come to cover 4.9% of the lake surface, thereby becoming dominant. In Erhai Lake, 16 community types of native plant communities, covering 47.1% of the lake surface in the late 1970s, declined to 10 community types, covering 9.3% of the surface, by the late 2000s. Alien plant communities appeared in the middle 1980s, and at present cover 0.7% of the surface area. It was indicated that changes in plant communities were significant related to water eutrophication. The area occupied by native and alien plant communities was, respectively, negatively and positively related to the content of nutrients in water. This showed lacustrine pollution played an important role in native plant loss and alien plant invasion in the two plateau lakes. 相似文献
995.
996.
Horizontal starch gel electrophoresis was used to investigate the biochemical genetic structure of Chinese mittencrab Eriocheir sinensis and Hepu mitten crab E. hepuensis. Sixteen putative enzyme-coding loci were examined for forty-nineChinese mitten crabs and thirty-eight Hepu mitten crabs. Nine loci, AAT-1 *, AAT-2 *, G3PDH*, GPI*, IDHP-1 *, IDHP-2 *,MDH-1 *, MDH-2 * and PGM * , are polymorphic in Chinese mitten crab, and seven, AAT-1 *, AAT-2 *, GPI *, IDHP-1 *,MDH-1 *, MDH-2 * and PGM * , are polymorphic in Hepu mitten crab. The proportion of polymorphic loci and the expectedheterozygosity are 0.562 5 and 0.080 3 for Chinese mitten crab, and 0.437 5 and 0.075 4 for Hepu mitten crab. The Nei' s ge-netic distance between two species is 0.002 4. 相似文献
997.
Characteristics and formation causes of Qingdao Cold Water Mass 总被引:2,自引:0,他引:2
In this work,the main characteristics of the Qingdao Cold Water Mass were studied by using“the comparison analysis method”based on 1980 temperature,salinity and dissolved oxygen data on the western South Yellow Sea.The formation cause of the water mass was analyzed based on February of 1959 temperature and salinity data for this area and on some other authors’studies.The results showed that the Qingdao Cold Water Mass has growing and vanishing processes:appears in the last ten days of March;has stable pattern in April;is biggest in its area in May;becomes small in its area in June;vanishes in July.It comes from the northem Shandong Coastal Water and is characterized by low temperature and salinity and high disolved oxygen.The mass is formed under the joint effects of anticyclonic circulation and solar radiation. 相似文献
998.
本文运用构造地质学中有关节理裂隙、层理和断层等构造面的概念,论述了饰面板石材矿床的地质研究与评价方法,并指出岩石的自然块度、自然块度分级及其计算方法是该项研究的重要内容。此外,该文还论述了矿床开采阶段中各种自然构造分离面的合理应用。 相似文献
999.
Geochemical studies of the U, Th, Ra, and40K in surface sediments of the China Sea and adjacent sea areas, the lower reaches of the Huanghe and Changjiang Rivers and
the estuaries of the Zhujiang and Rongjiang Rivers were carried out with a model 8180-4K multichannel Ge(Li)γ spectrometer
in 1981–1985. The mean values of U, Ra, Th,40K are about 2.11 ppm, 7.67×10−13g/g, 11.00 ppm, and 2.33 ppm respectively, in the China Sea, the Okinawa Trough, and the Changjiang and Huanghe River estuaries.
The distribution of the four isotopes is uniform in the above zone.
The contents of U and Th in the sediments of the Zhujiang and Rongjiang Rivers and the Fujian coast are 1–4 times higher than
those of the above zone and are related to the granite and radioactive ore present in the upper reaches of these rivers or
the adjacent mountains.
The distributions of U, Th, Ra, and40K are related to the physico-chemical property, redox state, geological type and grain size of the sediment, and biotic activity.
Contribution No. 1408, Institute of Oceanology, Academia Sinica, Qingdao. 相似文献
1000.
Technique for Controlling Spread of Limnotic Oncomelania 总被引:1,自引:0,他引:1
Schistosomiasis is a parasitic disease mostly found in areas along the Changjiang River of China. The disease is spread solely through an intermediary named oncomelania, so its spread of schistosomiasis can be controlled by properly designing water intakes which prevent oncomelania from entering farming land or residential areas. This paper reports a successful design process and a new oncomelania-free intake device. The design of the new intake is based on a sound research program in which extensive experimental studies were carried out to gain knowledge of oncomelania eco-hydraulic behavior and detailed flow field information through CFD simulation. 相似文献