全文获取类型
收费全文 | 651篇 |
免费 | 30篇 |
国内免费 | 5篇 |
专业分类
测绘学 | 36篇 |
大气科学 | 48篇 |
地球物理 | 175篇 |
地质学 | 255篇 |
海洋学 | 69篇 |
天文学 | 65篇 |
综合类 | 8篇 |
自然地理 | 30篇 |
出版年
2022年 | 4篇 |
2021年 | 11篇 |
2020年 | 13篇 |
2019年 | 11篇 |
2018年 | 25篇 |
2017年 | 29篇 |
2016年 | 37篇 |
2015年 | 29篇 |
2014年 | 37篇 |
2013年 | 44篇 |
2012年 | 37篇 |
2011年 | 37篇 |
2010年 | 32篇 |
2009年 | 39篇 |
2008年 | 33篇 |
2007年 | 38篇 |
2006年 | 29篇 |
2005年 | 17篇 |
2004年 | 17篇 |
2003年 | 11篇 |
2002年 | 14篇 |
2001年 | 9篇 |
2000年 | 6篇 |
1999年 | 10篇 |
1998年 | 8篇 |
1997年 | 10篇 |
1996年 | 6篇 |
1995年 | 7篇 |
1994年 | 9篇 |
1993年 | 6篇 |
1992年 | 5篇 |
1991年 | 4篇 |
1990年 | 4篇 |
1989年 | 2篇 |
1988年 | 2篇 |
1987年 | 2篇 |
1986年 | 4篇 |
1985年 | 2篇 |
1984年 | 4篇 |
1981年 | 4篇 |
1980年 | 2篇 |
1979年 | 4篇 |
1978年 | 3篇 |
1977年 | 4篇 |
1976年 | 3篇 |
1975年 | 2篇 |
1974年 | 5篇 |
1951年 | 2篇 |
1948年 | 1篇 |
1946年 | 1篇 |
排序方式: 共有686条查询结果,搜索用时 0 毫秒
631.
Lo?c Cahierre 《Journal of Geodesy》1951,25(1):42-56
Conclusion Les travaux de nivellement effectués sur la Gironde ont done permis à l’Institut Géographique National de préciser ses idées
sur des méthodes nouvelles. Il a pu constater, en particulier, qu’une méthode qu’il considère comme une méthode expédiée permet
actuellement d’exécuter des nivellements qui valent ceux du réseau de 1er ordre, effectués par une méthode beaucoup plus longue et plus compliquée.
Ces résultats sont dus pour une part à l’habileté technique des opérateurs. Ils sont dus aussi aussi à la qualité du matériel
utilisé. Les perfectionnements apportés dans la construction des instruments. en particulier la précision des réalisations
mécaniques actuelles, permet de s’affranchir d’un traditionnalisme devenu sans objet, et d’abandonner des modes opératoires,
ingénieux certes et mathématiquement séduisants, qu’on avait imaginés pour pallier l’insuffisance des appareils. Confort dans
les observations, économie de peine pour les opérateurs, gain de temps dans les travaux, augmentation de la précision dans
les mesures, ce sont là des avantages sérieux qui concourent tous à l’amélioration de la qualité des résultats.
相似文献
632.
Sergio Pacca 《Climatic change》2007,84(3-4):281-294
Greenhouse gas (GHG) emissions from hydroelectric dams are often portrayed as nonexistent by the hydropower industry and have
been largely ignored in global comparisons of different sources of electricity. However, the life cycle assessment (LCA) of
any hydroelectric plant shows that GHG emissions occur at different phases of the power plant’s life. This work examines the
role of decommissioning hydroelectric dams in greenhouse gas emissions. Accumulated sediments in reservoirs contain noticeable
levels of carbon, which may be released to the atmosphere upon decommissioning of the dam. The rate of sediment accumulation
and the sediment volume for six of the ten largest United States hydroelectric power plants is surveyed. The amount of sediments
and the respective carbon content at the moment of dam decommissioning (100 years after construction) was estimated. The released
carbon is partitioned into CO2 and CH4 emissions and converted to CO2 equivalent emissions using the global warming potential (GWP) method. The global warming effect (GWE) due to dam decommissioning
is normalized to the total electricity produced over the lifetime of each power plant. The estimated GWE of the power plants
range from 128–380 g of CO2eq./kWh when 11% of the total available sediment organic carbon (SOC) is mineralized and between 35 and 104 g of CO2eq./kWh when 3% of the total SOC is mineralized. Though these values are below emission factors for coal power plants (890 g
of CO2eq./kWh), the amount of greenhouse gases emitted by the sediments upon dam decommissioning is a notable amount that should
not be ignored and must be taken into account when considering construction and relicensing of hydroelectric dams. 相似文献
633.
J. Hansen M. Sato R. Ruedy P. Kharecha A. Lacis R. Miller L. Nazarenko K. Lo G. A. Schmidt G. Russell I. Aleinov S. Bauer E. Baum B. Cairns V. Canuto M. Chandler Y. Cheng A. Cohen A. Del Genio G. Faluvegi E. Fleming A. Friend T. Hall C. Jackman J. Jonas M. Kelley N. Y. Kiang D. Koch G. Labow J. Lerner S. Menon T. Novakov V. Oinas Ja. Perlwitz Ju. Perlwitz D. Rind A. Romanou R. Schmunk D. Shindell P. Stone S. Sun D. Streets N. Tausnev D. Thresher N. Unger M. Yao S. Zhang 《Climate Dynamics》2007,29(7-8):661-696
We carry out climate simulations for 1880–2003 with GISS modelE driven by ten measured or estimated climate forcings. An ensemble
of climate model runs is carried out for each forcing acting individually and for all forcing mechanisms acting together.
We compare side-by-side simulated climate change for each forcing, all forcings, observations, unforced variability among
model ensemble members, and, if available, observed variability. Discrepancies between observations and simulations with all
forcings are due to model deficiencies, inaccurate or incomplete forcings, and imperfect observations. Although there are
notable discrepancies between model and observations, the fidelity is sufficient to encourage use of the model for simulations
of future climate change. By using a fixed well-documented model and accurately defining the 1880–2003 forcings, we aim to
provide a benchmark against which the effect of improvements in the model, climate forcings, and observations can be tested.
Principal model deficiencies include unrealistically weak tropical El Nino-like variability and a poor distribution of sea
ice, with too much sea ice in the Northern Hemisphere and too little in the Southern Hemisphere. Greatest uncertainties in
the forcings are the temporal and spatial variations of anthropogenic aerosols and their indirect effects on clouds.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
634.
635.
Aloysius K. Lo 《Boundary-Layer Meteorology》1979,17(4):465-484
This paper proposes a numerical technique based on the least-square error method for evaluating fluxes and other surface-layer parameters. The special feature of this method is that it requires no a-priori knowledge of either the temperature profile or the roughness length z
0. The accuracy of the method has been tested on both the Kansas and the Wangara experimental data. Results obtained compared favourably with those from direct measurements as well as from other studies using conventional approaches. 相似文献
636.
The level of total hydrocarbon in three chosen sites in Hong Kong was determined over a period of 8 months, September 1977 to April 1978. The range of hydrocarbon content is 3.67 ppb to 11.98 ppb. The level of hydrocarbon in Pacific Ocean is 0.016 ppb. The oil pollution in Hong Kong shoreline waters is 230–750 times higher than deep ocean water, but the level is not yet hazardous. 相似文献
637.
G. Capaldi I. Guerra A. Lo Bascio G. Luongo R. Pece A. Rapolla R. Scarpa E. Del Pezzo M. Martini M. R. Ghiara L. Lirer R. Munno L. La Volpe 《Bulletin of Volcanology》1978,41(3):259-285
On November 4, 1975 in the evening, an eruption took place at Mt. Stromboli. On the following day lava flowed on the Sciara del Fuoco downward to the sea, accompanied by an intense explosive activity at the crater plane. Direct observations on the volcanic activity were carried out since November 6 while a seismic survey was made from Nov. 7 to 12. The total volume of the lava outpoured during this period of activity that lasted 21 days, was estimated to be about 104 m3. This paper reports the results of direct observations, and of the petrological, radioactive disequilibria and seismic activity studies performed for this eruption. The eruption was preceded by an insignificant change of seismic activity, which was monitored by a seismic station located about 2 km East of the crater. A shallow seismicity was strietly related to crater explosions accompanying the eruptive phenomenon. Radioactive disequilibria showed a lack of disequilibrium between228Ra and232Th explainable in terms of a fast rising of magma in the conduit. Chemical analyses of lava samples and deep seismic sounding data indicate a correspondence between the depth (10–15 km) at which crystallization pressure of phenocrysts occurs and a low velocity laver. 相似文献
638.
Aloysius K. Lo 《Boundary-Layer Meteorology》1977,12(2):141-151
A method based on the principle of the Method of Weighted Residuals for evaluating the roughness-length (z
0) and zero-plane displacement (d) is presented. This method not only can minimize errors involved during the calculation process but can also smooth and re-distribute the already minimized error in a most favourable manner via using appropriate weighting functions. With the inclusion of d in addition to z
0, formulae for wind and temperature profiles in the surface layer are presented by:% MathType!MTEF!2!1!+-% feaafeart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4baFfea0dXde9vqpa0lb9% cq0dXdb9IqFHe9FjuP0-iq0dXdbba9pe0lb9hs0dXda91qaq-xfr-x% fj-hmeGabaqaciGacaGaaeqabaWaaeaaeaaakeaacaWGvbGaeyypa0% ZaaSaaaeaacaWG1bWaaSbaaSqaaiaacQcaaeqaaaGcbaGaam4Aaaaa% daWadaqaaiGacYgacaGGUbWaaeWaaeaadaWcaaqaaiaadQhacqGHsi% slcaWGKbaabaGaamOEamaaBaaaleaacaaIWaaabeaaaaaakiaawIca% caGLPaaacqGHRaWkcqaHipqEaiaawUfacaGLDbaaaaa!43FC!\[U = \frac{{u_* }}{k}\left[ {\ln \left( {\frac{{z - d}}{{z_0 }}} \right) + \psi } \right]\]and% MathType!MTEF!2!1!+-% feaafeart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4baFfea0dXde9vqpa0lb9% cq0dXdb9IqFHe9FjuP0-iq0dXdbba9pe0lb9hs0dXda91qaq-xfr-x% fj-hmeGabaqaciGacaGaaeqabaWaaeaaeaaakeaacqaH4oqCcqGHsi% slcqaH4oqCdaWgaaWcbaGaaGimaaqabaGccqGH9aqpcqaH4oqCdaWa% daqaaiGacYgacaGGUbWaaeWaaeaadaWcaaqaaiaadQhacqGHsislca% WGKbaabaGaamOEamaaBaaaleaacaaIWaaabeaaaaaakiaawIcacaGL% PaaacqGHRaWkcqaHipqEdaWgaaWcbaacbmGaa8hvaaqabaaakiaawU% facaGLDbaaaaa!485A!\[\theta - \theta _0 = \theta \left[ {\ln \left( {\frac{{z - d}}{{z_0 }}} \right) + \psi _T } \right]\]where and
T
are the integrated diabetic influence functions' for velocity and temperature profiles respectively.Analytical expressions for both and
T
as functions of wind shear or, implicitly in terms of the Richardson number have been derived.Presented at the 10th Annual Congress of the Canadian Meteorological Society, Quebec City, Canada, May 26–28, 1976. 相似文献
639.
Sergio Castro Jorge Goldfarb Janusz Laskowski 《International Journal of Mineral Processing》1974,1(2):141-149
The rate and extent of the heterogeneous reaction that takes place between dissolved sodium sulphide and synthetic tenorite is studied for a wide range of sodium sulphide to copper oxide ratios. Besides the sulphidization with the formation of a copper-sulphide layer, a substantial oxidation of sulphide ions takes place at the surface of the solid. The extent of both types of reactions is quantitized by combining specific analytical methods.The results are discussed in terms of possible mechanisms and of their implications in the sulphidization process applied in the flotation of oxidized copper ores. 相似文献
640.
Sergio Castro Heriban Soto Jorge Goldfarb Janusz Laskowski 《International Journal of Mineral Processing》1974,1(2):151-161
The rate of consumption of sulphide in the sulphidizing reactions of malachite and chrysocolla has been measured. The oxidation of sulphide ions at the surface of sulphidized chrysocolla was shown to take place. The influence of thiosulphate anions on the xanthate flotation of sulphidized malachite and chrysocolla was investigated and it was shown to depress the flotation of chrysocolla strongly.The result suggest, that the presence of thiosulphate as a product of simultaneous oxidation can be one of the reasons for the more difficult flotation of sulphidized chrysocolla. 相似文献