全文获取类型
收费全文 | 88595篇 |
免费 | 1238篇 |
国内免费 | 889篇 |
专业分类
测绘学 | 2294篇 |
大气科学 | 6204篇 |
地球物理 | 16224篇 |
地质学 | 34027篇 |
海洋学 | 7782篇 |
天文学 | 19865篇 |
综合类 | 359篇 |
自然地理 | 3967篇 |
出版年
2022年 | 541篇 |
2021年 | 893篇 |
2020年 | 992篇 |
2019年 | 1043篇 |
2018年 | 4215篇 |
2017年 | 3851篇 |
2016年 | 3617篇 |
2015年 | 1447篇 |
2014年 | 2450篇 |
2013年 | 4011篇 |
2012年 | 3277篇 |
2011年 | 5193篇 |
2010年 | 4514篇 |
2009年 | 5429篇 |
2008年 | 4549篇 |
2007年 | 5077篇 |
2006年 | 3081篇 |
2005年 | 2460篇 |
2004年 | 2416篇 |
2003年 | 2324篇 |
2002年 | 2170篇 |
2001年 | 1777篇 |
2000年 | 1670篇 |
1999年 | 1312篇 |
1998年 | 1386篇 |
1997年 | 1279篇 |
1996年 | 1108篇 |
1995年 | 1037篇 |
1994年 | 969篇 |
1993年 | 828篇 |
1992年 | 807篇 |
1991年 | 809篇 |
1990年 | 867篇 |
1989年 | 672篇 |
1988年 | 673篇 |
1987年 | 739篇 |
1986年 | 641篇 |
1985年 | 861篇 |
1984年 | 898篇 |
1983年 | 796篇 |
1982年 | 778篇 |
1981年 | 664篇 |
1980年 | 681篇 |
1979年 | 631篇 |
1978年 | 628篇 |
1977年 | 503篇 |
1976年 | 489篇 |
1975年 | 499篇 |
1974年 | 448篇 |
1973年 | 480篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
891.
The influence of capture stress, salinity and reproductive status on zinc associated with the metallothionein-like (MT-like) proteins in the livers of three marine teleost species was investigated. In striped mullet, Mugil cephalus L., the zinc associated with the MT-like protein, as determined by gel-permeation HPLC, increased significantly from approximately 102 to 1162 nmol zinc bound/g wet wt 7 days following capture in the field, handling, transportation to the laboratory and transfer to holding tanks. Significant increases were also observed following exposure to reduced salinity for 7 days. Smaller increases were observed in cultured red drum, Sciaenops ocellatus, livers following exposure to reduced salinity and physical trauma for 7 days. Finally, there was approximately a 2·5-fold increase in the zinc associated with the MT-like protein in livers of female spotted seatrout, Cynoscion nebulosus, collected during the reproductive season compared to regressed animals. These findings emphasize the need for establishing the natural fluctuations in MT levels as well as the response to common physical environmental variables before measurement of MT can be used reliably as a biochemical indicator of environmental contamination. 相似文献
892.
The wadic project: A comprehensive field evaluation of directional wave instrumentation 总被引:1,自引:0,他引:1
J. Allender T. Audunson S. F. Barstow S. Bjerken H. E. Krogstad P. Steinbakke L. Vartdal L. E. Borgman C. Graham 《Ocean Engineering》1989,16(5-6)
The results of a comprehensive field trial of nearly all commercially available directional wave measurement systems at the Edda field in the North Sea during winter 1985-86 are presented. The results summarize the accuracy of the principal engineering wave parameters from each system and the dependence on sea state. Limiting factors on system performance and operational problems are also included in the assessment. Overall experience has been good with systems utilizing widely different measurement principles returning consistent results. 相似文献
893.
894.
Periods and amplitudes of long-term temperature fluctuations were obtained using the methods of spectral analysis and filtration of secular time series of the air temperature at 13 hydrometeorological stations in the Black Sea region. The prognostic calculations of the long-term air temperature variability are based on the results of processing of time series. The calculations of the air temperature agree with the data of observations. The possibility of the long-term air temperature variability prediction is shown. 相似文献
895.
We describe the methodology and software developed for the numerical analysis of the characteristics of the horizontal and vertical structure of geostrophic currents. We present the results of computation of these characteristics according to the data of the summer survey of the Black Sea carried out as a part of the ComSBlack-92 program. The distinctive features of the space structure of geostrophic currents discovered as a result and the established parameters of their variability may supplement the existing data on the current field in the Black Sea. 相似文献
896.
The high diversity of grain-size parameters of marine and oceanic sediments is determined by hydrodynamical and gravitational processes. Grain-size spectra of the sediments in the World Ocean are represented by two main types. Filtering organisms that passively inherit the proportions of clayey fractions in suspended matter only accelerate the deposition of fine particles, not influencing their distribution at the bottom. 相似文献
897.
Richard N. Hey Gary J. Massoth Robert C. Vrijenhoek Peter A. Rona John Lupton David A. Butterfield 《Marine Geophysical Researches》2006,27(2):137-153
Earth’s fastest present seafloor spreading occurs along the East Pacific Rise near 31°–32° S. Two of the major hydrothermal
plume areas discovered during a 1998 multidisciplinary geophysical/hydrothermal investigation of these mid-ocean ridge axes
were explored during a 1999 Alvin expedition. Both occur in recently eruptive areas where shallow collapse structures mark
the neovolcanic axis. The 31° S vent area occurs in a broad linear zone of collapses and fractures coalescing into an axial
summit trough. The 32° S vent area has been volcanically repaved by a more recent eruption, with non-linear collapses that
have not yet coalesced. Both sites occur in highly inflated areas, near local inflation peaks, which is the best segment-scale
predictor of hydrothermal activity at these superfast spreading rates (150 mm/yr). 相似文献
898.
The results of theoretical studies of fracture lines in the ice floes of the Gulf of Ob as a function of the coefficient of internal sliding are presented in this paper. An estimate of the fractal dimensions of the emerging topological structures and the results of the calculation of stresses in the ice cover of the Gulf of Ob are presented as functions of different directions of external forcing caused by the joint action of winds and currents on the ice. The geographical locations of the zones of possible loads are shown, together with the estimates of the hummock sizes in the zones of the maximal compression of the ice floes in the Gulf of Ob. 相似文献
899.
Daniel S. Scheirer Ken C. Macdonald Donald W. Forsyth Stephen P. Miller Dawn J. Wright Marie-Hélène Cormier Charles M. Weiland 《Marine Geophysical Researches》1996,18(1):1-12
Four large-scale bathymetric maps of the Southern East Pacific Rise and its flanks between 15° S and 19° S display many of the unique features of this superfast spreading environment including abundant seamounts (the Rano Rahi Field), axial discontinuities, discontinuity migration, and abyssal hill variation. Along with a summary of the regional geology, these maps will provide a valuable reference for other sea-going programs on-and off-axis in this area, including the Mantle ELectromagnetic and Tomography (MELT) experiment. 相似文献
900.
cDNA's coding for cytochrome P4501A1 (CYP1A1), phenol UDP-glucuronosyltransferase (UDPGT) and glutathione S-transferase (GST-A) were cloned and sequenced from an expression library prepared from the liver of a 3-methylcholanthrene (3-MC) induced plaice. Plaice CYP1A1 and Phenol UDPGT display a high degree of structural conservation with homologous mammalian isoforms and their mRNAs were shown to be highly induced in liver after 3-MC treatment of fish. Expression of plaice GST-A, which displays closer homology to GSTs from plants and invertebrates than those of mammals, is repressed after 3-MC treatment. 相似文献