全文获取类型
收费全文 | 72407篇 |
免费 | 1451篇 |
国内免费 | 1350篇 |
专业分类
测绘学 | 2082篇 |
大气科学 | 5479篇 |
地球物理 | 14906篇 |
地质学 | 25331篇 |
海洋学 | 6382篇 |
天文学 | 16456篇 |
综合类 | 341篇 |
自然地理 | 4231篇 |
出版年
2022年 | 454篇 |
2021年 | 737篇 |
2020年 | 766篇 |
2019年 | 857篇 |
2018年 | 1718篇 |
2017年 | 1636篇 |
2016年 | 2038篇 |
2015年 | 1268篇 |
2014年 | 1971篇 |
2013年 | 3583篇 |
2012年 | 2321篇 |
2011年 | 3107篇 |
2010年 | 2765篇 |
2009年 | 3655篇 |
2008年 | 3157篇 |
2007年 | 3211篇 |
2006年 | 3053篇 |
2005年 | 2242篇 |
2004年 | 2207篇 |
2003年 | 2024篇 |
2002年 | 2008篇 |
2001年 | 1740篇 |
2000年 | 1655篇 |
1999年 | 1421篇 |
1998年 | 1446篇 |
1997年 | 1442篇 |
1996年 | 1172篇 |
1995年 | 1125篇 |
1994年 | 1027篇 |
1993年 | 904篇 |
1992年 | 835篇 |
1991年 | 820篇 |
1990年 | 847篇 |
1989年 | 797篇 |
1988年 | 723篇 |
1987年 | 878篇 |
1986年 | 745篇 |
1985年 | 892篇 |
1984年 | 1099篇 |
1983年 | 950篇 |
1982年 | 929篇 |
1981年 | 834篇 |
1980年 | 800篇 |
1979年 | 738篇 |
1978年 | 749篇 |
1977年 | 676篇 |
1976年 | 618篇 |
1975年 | 617篇 |
1974年 | 592篇 |
1973年 | 645篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
981.
K. A. Shukurov I. I. Mokhov L. M. Shukurova 《Izvestiya Atmospheric and Oceanic Physics》2014,50(3):256-265
Temperature and radiation effects of the 2010 summer fires are estimated on the basis of measurements at the Zvenigorod Scientific Station (ZSS) of the Obukhov Institute of Atmospheric Physics, Russian Academy of Sciences (RAS), in the Moscow region. The surface air temperature during the 2010 summer smoke varied in antiphase with the aerosol mass concentration, and the thermal radiation balance in the surface layer of the atmosphere varied in phase. Under extreme smoke of the surface layer in August 2010, the reduction in surface air temperature at ZSS has been found to reach 4 K with an increase in the downward flux of thermal radiation by an average of 20 W/m2 and a decrease in the difference between upward and downward fluxes of thermal radiation by an average of 24 W/m2. 相似文献
982.
Coastal sand dunes are considered among the most susceptible habitats to recreational use. The aim of this study was to monitor the impact of visitor use on soil and annual plants on long-established trails in the stabilised coastal dunes of the Sharon Park, Israel. The results indicate that:
- 1. The vegetation cover, height and species richness and diversity, as well as soil organic matter content were lower on trails subjected to high visitor use than that on trails under low use. However, soil compaction and moisture on high-use trails were higher than that on low use.
- 2. The rate of change in each of the vegetation properties moving outwards from the centre of the trail towards the undamaged area on its margins and beyond, was higher on trails under high visitor use than on low-use trails.
- 3. The impact of high visitor use is localised and limited to the trail boundaries and their immediate surroundings (6 m axis perpendicular to the trails), while the effect on low-use trails is dispersed over a larger area, apparently because the trail borders are less visually defined to the visitor.
983.
P. A. Klimov G. K. Garipov B. A. Khrenov V. S. Morozenko V. O. Barinova V. V. Bogomolov M. A. Kaznacheeva M. I. Panasyuk K. Yu. Saleev S. I. Svertilov 《Izvestiya Atmospheric and Oceanic Physics》2017,53(9):924-933
In this paper, data obtained by the Vernov satellite are discussed in comparison with the data obtained by Universitetsky–Tatiana-1, 2 satellites. The advanced instrumentation onboard the Vernov satellite improved the capabilities of the data-transmission system, providing an opportunity to acquire more detailed information on transient atmospheric events (TAEs), including a wider range of TAE photon numbers (event brightness) down to lower photon numbers, the opportunity to observe the events in ultraviolet range without the considerable inclusion of red–infrared photons (which indicates the substantial contribution of electric discharges, lightning precursors, at the altitudes of thunderstorm clouds), and the observation of TAE series at a rate of about 10–100 occurrences per second with a period from tens of seconds to several minutes. 相似文献
984.
P. N. Makkaveev A. A. Polukhin A. V. Kostyleva E. A. Protsenko S. V. Stepanova Sh. Kh. Yakubov 《Oceanology》2017,57(1):48-57
During cruise 65 of the R/V Akademik Mstislav Keldysh in the Kara Sea, three transects were executed: one eastwards from the Novaya Zemlya Archipelago and two in the St. Anna and Voronin troughs. It was noted that the continental runoff affected the entire surveyed aquatic area, even at the northern extremity of the Novaya Zemlya Archipelago. The transect along the St. Anna Trough showed the presence of a slope frontal zone overlaid at the surface by a desalinated layer. The Voronin Trough was characterized by sliding of slope waters. The hydrochemical parameters show that the surveys were carried out during a recession of biological activity of the waters and that the peak bloom was over by that time. The hydrochemical structure of waters conformed to early autumn conditions, but before the beginning of intense cooling of surface waters. 相似文献
985.
L. V. Sahakyan G. G. Babayan O. A. Belyaeva K. V. Sarkisyan G. O. Tepanosyan A. K. Saghatelyan 《Water Resources》2018,45(3):388-398
The paper gives the results of hydrochemical studies of the Tartar R.—the largest river in Nagornyi Karabakh Republic (NKR). Water quality was assessed with respect to the ecological standards of the Republic of Armenia in terms of major physicochemical characteristics and the concentrations of seven heavy metals. Water quality in the upper reaches of the Tartar R. was referred to the fifth class (poor quality), which is due to the effect of the dumps of the Sotck Gold Deposit and the pollution by agricultural, livestock, and municipal wastewaters. In the lower reaches of the Tartar R., the processes of dilution and self-purification neutralize the adverse effect of pollution sources on water quality, resulting in the improvement of water quality to the class not lower than medium, which is enough for the normal functioning of aquatic ecosystems, fishery, and irrigation. Thus, the Sarang Reservoir, which regulates the Tartar R. runoff, receives good-quality water. 相似文献
986.
Abstract The complexity of distributed hydrological models has led to improvements in calibration methodologies in recent years. There are various manual, automatic and hybrid methods of calibration. Most use a single objective function to calculate estimation errors. The use of multi-objective calibration improves results, since different aspects of the hydrograph may be considered simultaneously. However, the uncertainty of estimates from a hydrological model can only be taken into account by using a probabilistic approach. This paper presents a calibration method of probabilistic nature, based on the determination of probability functions that best characterize different parameters of the model. The method was applied to the Real-time Interactive Basin Simulator (RIBS) distributed hydrological model using the Manzanares River basin in Spain as a case study. The proposed method allows us to consider the uncertainty in the model estimates by obtaining the probability distributions of flows in the flood hydrograph. Citation Mediero, L., Garrote, L. & Martín-Carrasco, F. J. (2011) Probabilistic calibration of a distributed hydrological model for flood forecasting. Hydrol. Sci. J. 56(7), 1129–1149. 相似文献
987.
David L. Strayer Stuart E. G. Findlay Daniel Miller Heather M. Malcom David T. Fischer Thomas Coote 《Aquatic Sciences - Research Across Boundaries》2012,74(3):597-610
The shore zones of the Hudson River, like those of many developed waterways, are highly varied, containing a mix of seminatural and highly engineered shores. Our goal was to document the biodiversity supported by different kinds of shore zones in the Hudson. We chose six common types of shore zones, three of them ??natural?? (sand, unconsolidated rock, and bedrock), and three of them engineered (riprap, cribbing, and bulkheads). We measured selected physical characteristics (shore zone width, exposure, substrate roughness and grain size, shoreline complexity) of three examples of each of these shore types, and also sampled communities of terrestrial plants, fishes, and aquatic and terrestrial invertebrates. Community composition of most taxa differed across shore types, and frequently differed between wide, sheltered shores and narrow, exposed shores. Alien plant species were especially well represented along engineered shores. Nevertheless, a great deal of variation in biological communities was not explained by our six-class categorization of shore zones or the physical variables that we measured. No single shore type supported the highest values of all kinds of biodiversity, but engineered shore zones (especially cribbing and bulkheads) tended to have less desirable biodiversity characteristics than ??natural?? shore zones. 相似文献
988.
Water Resources - A procedure for assessing the protection of groundwater against pollution is considered. This is a basic procedure for tentative forecast estimates of changes in the... 相似文献
989.
Geomagnetism and Aeronomy - The magnetic fields of a subterranean source observed on the Earth’s surface or from the orbit of a satellite are studied. We analyze the space of all harmonic... 相似文献
990.
The diffusion of an ion in porewaters cannot occur independently of the other ions in solution as a result of Coulombic coupling, as well as from other effects not considered here. Unfortunately, a longstanding disagreement exists about the correct form and meaning of the equations that describe Coulombic coupling in porewaters, i.e., Ben-Yaakov [Am. J. Sci. 281 (1981) 974] vs. Lasaga [Am. J. Sci. 281 (1981) 981]. This paper re-examines this controversy by reformulating the problem starting from fundamental concepts of mass and charge conservation. We show that these antagonistic formulations are both valid and, in fact, equivalent, when the different interpretations of charge balance are resolved. Most of the disagreements between Ben-Yaakov and Lasaga are then shown to result from differing methods of solution, not fundamental disparities in their models. We note, however, that the explanation for the concept of “stationary” gradients of nonreacting ions as given Ben-Yaakov is inaccurate, and such gradients do lead to diffusive fluxes that are counterbalanced by electrochemical migrational fluxes to produce no net flux (excluding advective flux). We further find that the bicarbonate diffusive flux will not balance the diffusional charge flux of sulfate during its reduction if advection is present. This latter imbalance generates compensating fluxes in the other nonreacting ions. We have applied our theory to a simplified case of sulfate reduction in a marine sediment. The results show that nonreacting ions do diffuse and that with normally expected values of porewater advection, the ratio of the bicarbonate to the sulfate flux can be far different than the ideal value of −2. 相似文献