全文获取类型
收费全文 | 39441篇 |
免费 | 641篇 |
国内免费 | 274篇 |
专业分类
测绘学 | 772篇 |
大气科学 | 2614篇 |
地球物理 | 7772篇 |
地质学 | 14310篇 |
海洋学 | 3595篇 |
天文学 | 8766篇 |
综合类 | 90篇 |
自然地理 | 2437篇 |
出版年
2022年 | 260篇 |
2021年 | 450篇 |
2020年 | 507篇 |
2019年 | 586篇 |
2018年 | 1028篇 |
2017年 | 1028篇 |
2016年 | 1095篇 |
2015年 | 592篇 |
2014年 | 1073篇 |
2013年 | 1891篇 |
2012年 | 1204篇 |
2011年 | 1668篇 |
2010年 | 1465篇 |
2009年 | 1826篇 |
2008年 | 1664篇 |
2007年 | 1712篇 |
2006年 | 1570篇 |
2005年 | 1083篇 |
2004年 | 1093篇 |
2003年 | 1133篇 |
2002年 | 1013篇 |
2001年 | 882篇 |
2000年 | 805篇 |
1999年 | 735篇 |
1998年 | 722篇 |
1997年 | 731篇 |
1996年 | 605篇 |
1995年 | 580篇 |
1994年 | 516篇 |
1993年 | 462篇 |
1992年 | 416篇 |
1991年 | 426篇 |
1990年 | 446篇 |
1989年 | 396篇 |
1988年 | 374篇 |
1987年 | 408篇 |
1986年 | 421篇 |
1985年 | 516篇 |
1984年 | 554篇 |
1983年 | 550篇 |
1982年 | 502篇 |
1981年 | 457篇 |
1980年 | 436篇 |
1979年 | 414篇 |
1978年 | 381篇 |
1977年 | 387篇 |
1976年 | 349篇 |
1975年 | 355篇 |
1974年 | 340篇 |
1973年 | 373篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
841.
Indian Ocean humpback dolphins Sousa plumbea inhabit nearshore waters from South Africa to eastern India. Humpback dolphins are vulnerable to conservation threats due to their naturally small population sizes and use of nearshore habitats, where human activities are highest. We investigated the abundance and residency of this species inhabiting Mossel Bay, South Africa, using photographic mark-recapture. Data were collected during 81 surveys in Mossel Bay between 2011 and 2013. Open population modelling using the POPAN parameterisation produced a ‘super-population’ estimate of 125 individuals (95% CI: 61–260) and within-year estimates of between 33 and 86 individuals (2011: 71 [95% CI: 30–168]; 2012: 33 [15–73], 32 [15–70]; 2013: 46 [20–108]). Although less appropriate, closed capture models were also run for comparison with previous studies in the region and generated similar, but slightly smaller, population estimates within each year. We compared our catalogue with opportunistic data collected from East London, Plettenberg Bay, De Hoop and Gansbaai. The only catalogue matches attained were between Plettenberg Bay (n = 44 identified) and Mossel Bay (n = 67 identified), separated by 140?km. Population exchange was moderate, with nine individuals resighted in multiple years between these two areas. This study supports previous findings of long-range movements for this species and provides a baseline from which to assess future impacts on the population. 相似文献
842.
843.
I. B. Konovalov E. V. Berezin M. Beekmann 《Izvestiya Atmospheric and Oceanic Physics》2016,52(3):263-270
It has been shown by numerical simulation that the rate of formation of secondary organic aerosols (SOAs) in smoke plumes caused by vegetation and peat fires under real conditions can significantly depend on the aerosol optical thickness (AOT). The AOT determines the photodissociation rate and hydroxyl radical concentration, which in turn determines the rate of SOA generation as a result of oxidation of semivolatile organic compounds. Quantitative analysis has been carried out for the situation that took place in European Russia during the 2010 Russian wildfires. The state-of-the-art 3D chemical transport model is used in this study; the simulations are optimized and validated using the data of monitoring of the particulate matter in the Moscow region and Finland. The findings indicate that it is important to allow for this effect in studies focused on the analysis and prediction of air pollution due to wildfires, as well as climate and weather studies, whose results may depend on the assumptions about the content and properties of atmospheric carbon-containing aerosol. 相似文献
844.
A short survey prepared by the Russian Commission on Atmospheric Radiation contains the most significant results of work in the field of atmospheric-radiation studies performed in 2011–2014. It is part of the Russian National Report on Meteorology and Atmospheric Sciences prepared for the International Association on Meteorology and Atmospheric Sciences (IAMAS)1. During this period, the Russian Commission on Atmospheric Radiation, jointly with the concerned departments and organizations, organized two International Symposiums on Radiation and Dynamics (ISARD-2011 and ISARD-2013). At these conferences, the central problems in modern atmospheric physics were discussed: radiative transfer (RT) and atmospheric optics; greenhouse gases, clouds, and aerosols; remote methods of measurements; and new measurement data. This survey presents six directions covering the whole spectrum of investigations performed in the field of atmospheric radiation. 相似文献
845.
A. I. Kopylov A. F. Sazhin E. A. Zabotkina A. V. Romanenko N. D. Romanova P. R. Makarevich M. P. Wenger 《Oceanology》2016,56(6):789-798
The paper considers the concentrations and functional characteristics of viruses, bacteria, and heterotrophic nanoflagellates determined for the first time in the Laptev Sea in August-September, 2014. The abundance of bacteria, viruses, and heterotrophic nanoflagellates varied from 110.1 × 103 to 828.4 × 103 cells/mL, from 384.2 × 103 to 2932.8 × 103 particles/mL, and from 108 to 651 cells/mL, respectively. The daily bacterioplankton production varied from 4.2 × 103 to 381.7 × 103 cells/mL, with an average of 117.6 × 103 cells/mL. Electron transmission microscopy has for the first time shown that the frequency of visibly infected bacterial cells varied from 0.2 to 2.0% (0.8% on average) of NB. The average virus-induced mortality of bacteria was 6.3% of bacterioplankton production, with variations ranging from 1.4 to 16.9%. Grazing on bacteria by heterotrophic nanoflagellates contributed more to bacteria mortality than virus-induced bacterial lysis. By grazing on bacteria, heterotrophic nanoflagellates consumed large quantities of viruses located on the surface and inside bacterial cells. 相似文献
846.
Zavialov P. O. Zavialov I. B. Izhitskiy A. S. Izhitskaya E. S. Konovalov B. V. Krementskiy V. V. Nemirovskaya I. A. Chasovnikov V. K. 《Oceanology》2022,62(2):162-170
Oceanology - The paper presents the results of an analysis of the main pollutants (heavy metals, pesticides, detergents, hydrocarbons) in water, suspended particulate matter, and bottom sediments,... 相似文献
847.
Abstract During the GARP Atlantic Tropical Experiment (GA TE) in the summer of 1974, identical tethersonde packages were flown to heights of 1,000 m from two ships with a crosswind separation of approximately 4 km. The differences in the profiles and fixed level time series from the two packages are a measure of spatial variability in the tropical marine boundary layer. Correlation analysis indicate a cellular pattern in the large‐scale wind field. Similar analyses of the temperature and humidity fields give quite different results. 相似文献
848.
M. Marengo M. Karovska D.D. Sasselov C. Papaliolios J.T. Armstrong T.E. Nordgren 《Astrophysics and Space Science》2003,286(1-2):185-190
We present a new method to compute wavelength- and phase-dependent limb darkening corrections for classical Cepheids. These
corrections are derived from hydrodynamic simulations and radiative transfer modeling with a full set of atomic and molecular
opacities. Comparison with hydrostatic models having the same stellar parameters show a larger limb darkening for most phases
in our models, and temporal variations related to the hydrodynamics of the stellar pulsation. Weassess the implications of
our results with respect to the geometric Baade-Wesselink method, which uses interferometric measurements of Cepheid angular
diameters to determine their distances and radii. The relevance of the hydrodynamic effects predicted by our model on the
limb darkening of pulsating Cepheids is finally discussed in terms of the predicted capabilities of the VLTI.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
849.
Stephen E Haggerty 《Geochimica et cosmochimica acta》1973,37(4):857-867
Electron microprobe analyses of the spinel mineral group, ilmenite and rutile have been carried out on part of the Luna 20 soil sample. The spinel group shows an almost continuous trend from MgAl8O4 to FeCr2O4 and a discontinuous trend from FeCr2O4 to Fe2TiO4. Well defined non-linear relationships exist within the spinel group for Fe-Mg substitution, for divalent () versus trivalent (), and for divalent versus . For Cr-Al substitution the relationship is linear and is negative for Mg-rich spinel and positive for Fe-Ti rich spinel. In general a combination of aluminous-rich chromite and ulvöspinel in the Luna 16 samples, combined with the chromian-pleonaste in Apollo 14 define comparable major compositional trends to those observed in Luna 20. Ilmenite is present in trace amounts. It is exsolved from pleonaste and pyroxene, is present in subsolidusreduced ulvöspinel and has undergone reequilibration to produce oriented intergrowths of chromite + rutile. Primary ilmenite is among the most magnesian-rieh (6 wt.% MgO) yet found in the lunar samples. The high MgO, inferred high Cr2O3 concentrations and the iron content of rutile (2.5 wt.% FeO) suggest crystallization at high temperatures and pressures for some components of the Luna 20 soil. 相似文献
850.
Postnikov A. V. Postnikova O. V. Iz”yurova E. S. Poshibaev V. V. Kuznetsov A. S. Iz”yuraov A. D. Kozionov A. E. 《Lithology and Mineral Resources》2019,54(1):27-37
Lithology and Mineral Resources - Main regularities in the manifestation of epigenetic processes in Lower Vendian terrigenous rocks of the Nepa–Botuoba anteclise are established. Evolution of... 相似文献