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991.
992.
燃煤过程中有害元素转化机理研究进展 总被引:14,自引:0,他引:14
综述了煤中有毒、有害元素经燃烧之后的存在形式与去向,元素在燃烧过程中的热解释放行为及其转化机理;强调煤中无机组分为主要存在许多有毒、爱元素在燃烧过程中会释放出来,然后再分异扩散到各种燃烧产物之中,地民人体廷民危害;指出今后研究不仅限于煤中有毒、有害元素的形成机理,更应侧重对燃烧产物中毒、有害元素的分异与去除方法作进一步的研究与试验,力求使燃煤对环境与人体健康产生的危害降低到最低程度。 相似文献
993.
A. Alberti M. Sacerdoti S. Quartieri G. Vezzalini 《Physics and Chemistry of Minerals》1999,26(3):181-186
The dehydration-rehydration processes and phase transformations of brewsterite (space group P21/m, ideal formula (Sr,Ba)Al2Si6O16·5H2O) were studied by single crystal X-ray diffraction on two samples heated in an evacuated capillary for 24 h at 280°C and
330°C, respectively, and then cooled to room temperature. After the data collection, the capillary of the crystal heated at
280°C was broken, the sample was kept at room conditions for one month, and diffraction data were recollected. Brewsterite
heated in vacuum at 280°C shows a strong decrease of the unit cell volume (about 10%) and the statistical breaking of the
T1-O7-T2 bridge of the 4-ring of the 4254 PBU. T1 cation, in 31% of cases, migrates to a new tetrahedral site, which shares three vertices with the previously occupied
one; the fourth vertex is on the mirror plane, and joins two adjacent layers. T2 cation, in 20% of cases, migrates to a new
site, which is characterized by a 5-fold coordination. This coordination polyhedron shares three vertices with the previously
occupied tetrahedron; the fourth vertex is on the mirror plane, and joins two adjacent layers; the fifth one is unshared.
The formation of these new T-O-T bridges prevents the re-expansion and rehydration of the heated brewsterite; as a consequence,
the crystal brought back to room conditions does not show any noticeable structural difference with respect to that heated
at 280°C. The exchangeable cations, which occupy only one extraframework site in the untreated brewsterite, spread over several
sites. The sample heated at 330°C shows a further decrease in the unit cell volume of about 2% with respect to the sample
heated at 280°C, and an increase in the migration percentage of T1 and T2 cations to the new sites.
Received: 11 November 1997 / Revised, accepted: 26 June 1998 相似文献
994.
Herman Kok 《GeoJournal》1999,49(1):53-62
After the changes of 1989, urban-to-rural migration in Poland and Hungary remained stable compared to rural-to-urban migration.
This was connected to a growing importance of suburbanisation around major Hungarian and Polish cities. Suburban areas around
these cities are attracting increasing numbers of migrants from the major cities. Pollution and higher crime rates, as well
as rising living costs and increasing uncertainties make many people to decide to leave the city for the surrounding countryside.
Not only upper middle-class people move to the suburbs, but also lower status people, for whom life in the big city became
too difficult. Long-distance migration from the cities to the rural areas is declining. Economic problems together with low
employment opportunities prevent people from making such a move. Though the overall level of urban-to-rural migration did
not change too much, this article shows the rapidly increasing importance of suburbanisation.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
995.
Ulrike Sailer-Fliege 《GeoJournal》1999,49(1):7-16
The development of the post-socialist city has already been characterised by substantial restructuring processes. Particular
emphasis should be drawn to the take-off of the tertiary sector and the comprehensive blight phenomena in the previously industrial
areas. The urban housing sector has witnessed increasing housing affordability problems, a marginalisation of communal housing
stock, an increase of segregation and an intensification of the decay in the old housing stock. In all East Central European
states the spatial development processes of industry and services within the cities basically show clear parallels to the
pattern of urban development in continental Europe. In Hungary housing policy, tenure structure and the level of segregation
already show relatively closer similarities to the neoliberal, Anglo–American pattern of development. The other ECE states
show closer similarities to the corporatist welfare states of continental Europe. As far as medium-term urban development
in East Central Europe is concerned, it is to be assumed that – regardless of the specific path of further development – overall
solutions shall not be found for the fundamental problems which are the legacy of the socialist era – the decay of old housing
stock, large scale derelict industrial areas and the extent and deficiencies of high-rise housing estates.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
996.
997.
Qian Jiangchu 《海洋学报(英文版)》1999,(2):257-266
I~D~IONThe numerous research results on the deep-sea manganese nodules show that the most valuable metal elements such as Cu, Ni are mainly concentrated in the manganese minerals, which only take about 15% Of the weight in the total manganese nodules, therefore, many marine scien.tists pay more attention in their research on the manganese minerals rather than the other mineralsin the deep-sea maganeses nodules.There are more than tens of different kinds of manganese mineral phases in the nod… 相似文献
998.
为研究链状裸甲藻所产麻痹性贝类毒素(paralytic shellfish toxins, PST)在翡翠贻贝体内的累积、转化和排出规律,设置试验组和对照组,采用链状裸甲藻和中肋骨条藻投喂翡翠贻贝,开展短期累积(12 h)、长期累积(10 d)和排出(28 d)试验。结果表明:翡翠贻贝具有较强的毒素累积能力,内脏团是PST累积的主要部位, PST含量与产毒藻密度呈显著正相关关系。当链状裸甲藻密度为1.0×106cells/L时,贻贝内脏团PST含量累积2 h已接近食用贝类毒素安全标准,累积8 h超标。当产毒藻密度为5.0×105 cells/L时,贻贝内脏团PST含量累积2 d超标,累积8 d达到峰值(3 590.4±545.7)μg/kg。贻贝对PST具有累积快排出慢的特点,内脏团PST含量在排出16 d达标,排出速率先快后慢。内脏团对PST的累积和排出速率显著高于闭壳肌和其他组织,闭壳肌和其他组织则无显著差异。PST进入贻贝体内后发生了代谢转化,贻贝可能将产毒藻中膝沟藻毒素GTX3转化为GTX2, N-磺酰氨甲酰基膝沟藻毒素C2转化为C1,部分C1转化为脱氨甲酰基膝沟藻毒素2(dc... 相似文献
999.
通过检测航标灯运行时电源的电流变化,结合电流检测、信号调理、单稳态触发等电路的应用,介绍一种航标灯运行状态检测电路的设计原理。 相似文献
1000.
The agricultural regional type and function are the key theoretical issues in agricultural geography research. Gully agriculture in the Loess Plateau is a new regional type of agricultural system with the coupling development of the modern gully human-earth relationship. The study of its functional changes is of great practical significance for food security,rural revitalization and sustainable development of regional agriculture in the region of interest. This paper analyses the multifunctional... 相似文献