全文获取类型
收费全文 | 35685篇 |
免费 | 430篇 |
国内免费 | 327篇 |
专业分类
测绘学 | 1372篇 |
大气科学 | 2921篇 |
地球物理 | 7025篇 |
地质学 | 12715篇 |
海洋学 | 2619篇 |
天文学 | 8097篇 |
综合类 | 174篇 |
自然地理 | 1519篇 |
出版年
2021年 | 352篇 |
2020年 | 365篇 |
2019年 | 395篇 |
2018年 | 926篇 |
2017年 | 903篇 |
2016年 | 1196篇 |
2015年 | 697篇 |
2014年 | 1114篇 |
2013年 | 1888篇 |
2012年 | 1109篇 |
2011年 | 1406篇 |
2010年 | 1209篇 |
2009年 | 1557篇 |
2008年 | 1311篇 |
2007年 | 1248篇 |
2006年 | 1256篇 |
2005年 | 1037篇 |
2004年 | 908篇 |
2003年 | 911篇 |
2002年 | 916篇 |
2001年 | 832篇 |
2000年 | 798篇 |
1999年 | 721篇 |
1998年 | 674篇 |
1997年 | 681篇 |
1996年 | 606篇 |
1995年 | 588篇 |
1994年 | 565篇 |
1993年 | 456篇 |
1992年 | 413篇 |
1991年 | 438篇 |
1990年 | 443篇 |
1989年 | 416篇 |
1988年 | 382篇 |
1987年 | 455篇 |
1986年 | 377篇 |
1985年 | 483篇 |
1984年 | 517篇 |
1983年 | 510篇 |
1982年 | 476篇 |
1981年 | 391篇 |
1980年 | 391篇 |
1979年 | 334篇 |
1978年 | 355篇 |
1977年 | 321篇 |
1976年 | 282篇 |
1975年 | 288篇 |
1974年 | 321篇 |
1973年 | 340篇 |
1972年 | 212篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
71.
Time series of temperature, humidity and horizontal wind speed are presented from data collected at two tower sites during the 1968 Barbados Experiment. Marked and periodic fluctuations on the convective scale are evident in the traces. It is postulated that these fluctuations are due to moderate cumulus convection. Estimates show that departures in temperature and humidity at the surface must be due to downward mixing from near or above the convective cloud base. Such cloud layer-subcloud layer mixing must change the thermodynamic character of the subcloud layer. This in turn suggests that cloud convection may play an important part in governing the transport of energy across the air-sea interface. 相似文献
72.
73.
Erika Böhm-Vitense 《Astrophysics and Space Science》1969,4(2):233-239
For the case of isotropic coherent scattering plus absorption a simple expression is given (Equation 12) to compute the mean intensity of the radiationJ
v
(as a function of optical depth
v
) if the scattering coefficient
v
, the absorption coefficientK
v
and the Planck functionB
v are given as a function of depth. In general the accuracy of this approximation is of the order of a few percent.A fairly simple temperature-correction procedure for the case when scattering is important is described. 相似文献
74.
A method is presented to quantify the inelastic seismic resistance of reinforced concrete stack-like structures by non-linear earthquake analysis. The deformed configuration of stack is idealized as an assemblage of beam elements and actual stress–strain relationships of concrete and reinforcing steel are used to evaluate element matrices. Repeated non-linear analyses are performed by gradually increasing the intensity of acceleration time histories to a level where collapse of the stack is observed in primary stresses. The set of time histories thus obtained are then used to define the ultimate intensity of ground motion that the stack can sustain if inelastic deformations are permitted. A procedure is presented to quantify the difference between inelastic seismic resistance and elastic seismic resistance in terms of displacement ductility capacity factors. For seismic design using available inelastic resistance, values of curvature ductility factor demand for the cross-sections of stacks are also presented. © 1997 by John Wiley & Sons, Ltd. 相似文献
75.
Y. Ohashi T. Kawabe Y. Shigeta Y. Hirano H. Kusaka H. Fudeyasu K. Fukao 《Theoretical and Applied Climatology》2009,95(3-4):279-289
We estimated wet-bulb globe temperature (WBGT) using measured meteorological data to understand the bioclimates of human living spaces during the summer season. Our research focused on commercial and residential areas of Okayama City, Japan (population ~700,000). The commercial spaces (CO) mainly consisted of multi-story office buildings, whereas the residential spaces (RE) consisted of one- or two-story residential buildings. On a fine day with southeast winds, the spatially averaged WBGT measured in the CO was higher than that in the RE. The difference was statistically significant and would have caused noticeable discomfort and a high risk of heat disorder for occupants of the CO over the long term. For instance, at 1900 Japan Standard Time (JST), the maximum difference in the WBGT between the CO and RE sites was 2.0°C (23.5°C for the CO and 21.5°C for the RE). From 1800 to 1900 JST, the wet-bulb temperature in the CO was still 1.5–2.0°C higher than that in the RE, even though both areas had the same dry-bulb temperature. This indicates that the CO retained greater amounts of water vapor for longer periods compared to the RE. The wet-bulb temperature in the CO increased rapidly at most observation points when the southeast sea breeze arrived. In contrast, in the RE, the wet-bulb temperature decreased until evening. This difference was caused by moist air transported from a river about 1 km upwind from the CO. The moist air forced an increase in the WBGT and elevated the risk of heat disorder in the CO. The spatially averaged globe temperature of the CO at 1500 JST was 6.2°C lower than that at the RE, causing the WBGT of the CO to decrease. The results suggest that the higher WBGT in the CO was caused by higher wet-bulb temperatures. On a day with southwest winds, the CO and RE showed no difference in WBGT because the river was not included in the upwind source area. 相似文献
76.
Climatic effects on plankton and productivity on the Faroe Shelf 总被引:1,自引:0,他引:1
Hansen Bogi; Eliasen Solva K.; Gaard Eilif; Larsen Karin M.H. 《ICES Journal of Marine Science》2005,62(7):1224-1232
77.
A series of high temperature experiments was undertaken to study partitioning of several highly siderophile elements (HSE; Ru, Rh, Pd, Re, Os, Ir, Pt and Au) between Cr-rich spinel, olivine, pyroxene and silicate melt. Runs were carried out on a Hawaiian ankaramite, a synthetic eucrite basalt, and a DiAn eutectic melt, at one bar, 19 kbar, and 20 kbar, respectively, in the temperature range of 1200 to 1300°C, at oxygen fugacities between the nickel-nickel oxide (NNO) and hematite-magnetite (HM) oxygen buffers. High oxygen fugacities were used to suppress the formation of HSE-rich “nuggets” in the silicate melts. The resulting oxide and silicate crystals (<100 μm) were analyzed using both SIMS and LA-ICP-MS, with a spatial resolution of 15 to 50 μm. Rhenium, Au and Pd were all found to be incompatible in Cr-rich spinel (DResp/melt = 0.0012-0.21, DAusp/melt = 0.076, DPdsp/melt = 0.14), whereas Rh, Ru and Ir were all found to be highly compatible (DRhsp/melt = 41-530, DRusp/melt = 76-1143, DIrsp/melt = 5-22000). Rhenium, Pd, Au and Ru were all found to be incompatible in olivine (DReoliv/melt = 0.017-0.073, DPdoliv/melt = 0.12, DAuoliv/melt = 0.12, DRuoliv/melt = 0.23), Re is incompatible in orthopyroxene and clinopyroxene (DReopx/melt = 0.013, DRecpx/melt = 0.18-0.21), and Pt is compatible in clinopyroxene (DPtcpx/melt = 1.5). The results are compared to and combined with previous work on HSE partitioning among spinel-structured oxides, and applied to some natural magmatic suites to demonstrate consistency. 相似文献
78.
A.N. Antipov Yu.M. Semenov N.K. Elizbarashvili O.Ya. Sayadian R.M. Mamedov 《Geography and Natural Resources》2009,30(3):286-293
We have developed the planning documents for model territories of a different dimension: the landscape program of Adzharia (Georgia), the landscape structure plan for the Lake Sevan watershed basin (Armenia), and the landscape plan for the Shirvan National Park (Azerbaijan). Variants of the solution of regional natural-ecological problems are proposed, and the measures for implementation of the target concepts are substantiated. 相似文献
79.
K. S. Ganzei 《Geography and Natural Resources》2014,35(2):181-187
A comparative analysis is made of the landscape-forming factors, and their role in the formation of the spatial structure of landscapes in the Kuril and Hawaiian Islands is determined. The research has been done on the basis of landscape mapping at a scale of 1:200 000. A correlative study was made of the different genetic varieties of geosystems: classical landscapes, catenary and nuclear. In spite of the dissimilar character of manifestation of landscape-forming processes, there occur largely identical formation principles for the spatial structure of landscapes. 相似文献
80.