全文获取类型
收费全文 | 3243篇 |
免费 | 108篇 |
国内免费 | 90篇 |
专业分类
测绘学 | 70篇 |
大气科学 | 402篇 |
地球物理 | 811篇 |
地质学 | 1004篇 |
海洋学 | 647篇 |
天文学 | 299篇 |
综合类 | 46篇 |
自然地理 | 162篇 |
出版年
2023年 | 12篇 |
2022年 | 22篇 |
2021年 | 45篇 |
2020年 | 47篇 |
2019年 | 63篇 |
2018年 | 134篇 |
2017年 | 124篇 |
2016年 | 139篇 |
2015年 | 87篇 |
2014年 | 171篇 |
2013年 | 220篇 |
2012年 | 140篇 |
2011年 | 203篇 |
2010年 | 190篇 |
2009年 | 190篇 |
2008年 | 164篇 |
2007年 | 176篇 |
2006年 | 146篇 |
2005年 | 122篇 |
2004年 | 105篇 |
2003年 | 96篇 |
2002年 | 98篇 |
2001年 | 76篇 |
2000年 | 79篇 |
1999年 | 55篇 |
1998年 | 45篇 |
1997年 | 41篇 |
1996年 | 25篇 |
1995年 | 37篇 |
1994年 | 19篇 |
1993年 | 17篇 |
1992年 | 21篇 |
1991年 | 18篇 |
1990年 | 18篇 |
1989年 | 13篇 |
1988年 | 14篇 |
1987年 | 24篇 |
1986年 | 15篇 |
1985年 | 15篇 |
1984年 | 28篇 |
1983年 | 31篇 |
1982年 | 22篇 |
1981年 | 17篇 |
1980年 | 25篇 |
1979年 | 12篇 |
1978年 | 7篇 |
1977年 | 16篇 |
1975年 | 15篇 |
1974年 | 10篇 |
1973年 | 7篇 |
排序方式: 共有3441条查询结果,搜索用时 187 毫秒
401.
402.
D. Schwan F. Bertoldi S. Cho M. Dobbs R. Guesten N. W. Halverson W. L. Holzapfel E. Kreysa T. M. Lanting A. T. Lee M. Lueker J. Mehl K. Menten D. Muders M. Myers T. Plagge A. Raccanelli P. Schilke P. L. Richards H. Spieler M. White 《New Astronomy Reviews》2003,47(11-12):933
The APEX-SZ experiment is a sky survey designed to discover galaxy clusters via the Sunyaev–Zel’dovich effect at millimeter wavelengths. We describe the components of the instrument, including the 12 m Atacama Pathfinder Experiment telescope, optics, Transition-edge sensor bolometer array and SQUID readout. APEX-SZ will begin observations in 2004. 相似文献
403.
404.
405.
We previously described the genomic structure of the cytochrome P450 1A (CYP1A) gene from the hermaphroditic fish Rivulus marmoratus [Kim, I.-C., Kim, Y.J., Yoon, Y.-D, Kawamura, S., Lee, Y.-S., Lee, J.-S., 2004a. Cloning of cytochrome P450 1A (CYP1A) genes from the hermaphroditic fish Rivulus marmoratus and the Japanese medaka Oryzias latipes. Mar. Environ. Res. 58, 125–129]. To further characterize R. marmoratus CYP1A, we cloned the cDNA sequence of a CYP1A gene from this species and also expressed its recombinant protein in an E. coli system. We exposed R. marmoratus to 4-nonylphenol, and found a small induction of CYP1A mRNA in the treated animals. In this paper, we discuss the characteristics of R. marmoratus CYP1A gene as well as its potential use in a biomonitoring assay. 相似文献
406.
Lee Kimball 《Marine Policy》1981,5(3):287-290
After consultations with the other interested departments and agencies of the United States Government, the Secretary of State has instructed our representative to the UN Law of the Sea Conference to seek to ensure that the negotiations do not end at the present session of the conference, pending a policy review by the United States Government. The interested departments and agencies have begun studies of the serious problems raised by the draft convention, and these will be the subject of a thorough review which will determine our position toward the negotiations.' (Press Release posted at the US Department of State, 2 March 1981). 相似文献
407.
Joseph Hun-wei Lee 《中国海洋湖沼学报》1984,2(1):20-33
Numerical solution of two-dimensional shallow water equations has been achieved by the finite element method. In this work, the governing equations were first converted into different equations suitable for explicit, forward marching, integration in the time domain. A second order Taylor's series expansion was used for the continuity equation and an "upwind" differencing was incorporated in the nonlinear convective terms in the momentum equations.The model was applied to Tolo Harbour in Hong Kong. Velocity vector plots and surface elevations obtained from the calculations are reasonably consistent with the expected tidal response of the systems. 相似文献
408.
The production mechanisms of backscattered electrons and trapped electrons along auroral field lines are examined. The backscattered electrons are produced not only by electron-neutral collisions, but also by electrostatic turbulence predominantly in the ion-cyclotron and ion-acoustic modes. The trapped electrons can only be produced by electron wave turbulence, most likely in the whistler and upper hybrid modes known as the auroral hiss. 相似文献
409.
T. J. Lee 《Geophysical Journal International》1980,60(1):67-75
Summary. The potential function ø for a magnetic body of susceptibility μ in a medium of susceptibility μ* satisfies the integral equation
Here Φ* is the potential function for the region without the heterogeneity and R is the distance from the point of observation to the point on the surface, s , of the body. δΦ /δn is the normal derivative, in the direction of the outward normal. The equation allows for the effects of demagnetization. For numerical purposes the surfaces can be divided into N facets over which δΦ/δ n is a constant. The unknown quantities δΦ/δnj can be found from the system of equations defined by:
The prime on the summation sign denotes that the summation does not include the i th element. The magnetic field in the direction of the unit vector P( P1 , P 2 , P3 ) is given by: 相似文献
Here Φ* is the potential function for the region without the heterogeneity and R is the distance from the point of observation to the point on the surface, s , of the body. δΦ /δn is the normal derivative, in the direction of the outward normal. The equation allows for the effects of demagnetization. For numerical purposes the surfaces can be divided into N facets over which δΦ/δ n is a constant. The unknown quantities δΦ/δn
The prime on the summation sign denotes that the summation does not include the i th element. The magnetic field in the direction of the unit vector P( P
410.
The alignments of the strapdown inertial navigation system (SDINS) utilizing GPS carrier phase rate measurements is introduced. In this paper, a measurement model of GPS carrier phase rate under two antenna configurations is derived in order to be used for the SDINS alignment process. For in-flight alignment, the performance of the proposed SDINS/GPS integration method is analyzed using the covariance analysis and the overall performance is briefly confirmed by the navigation result of a van test. Furthermore, we find that during in-flight alignment the proposed SDINS/GPS integrated system using GPS carrier phase rate measurements can be implemented in real time because the integer ambiguity problem resulting from carrier phase measurements is avoided. 相似文献