全文获取类型
收费全文 | 43030篇 |
免费 | 2695篇 |
国内免费 | 3143篇 |
专业分类
测绘学 | 1470篇 |
大气科学 | 4784篇 |
地球物理 | 9408篇 |
地质学 | 16765篇 |
海洋学 | 4119篇 |
天文学 | 8017篇 |
综合类 | 1168篇 |
自然地理 | 3137篇 |
出版年
2022年 | 596篇 |
2021年 | 751篇 |
2020年 | 697篇 |
2019年 | 782篇 |
2018年 | 1239篇 |
2017年 | 1119篇 |
2016年 | 1390篇 |
2015年 | 1037篇 |
2014年 | 1462篇 |
2013年 | 2165篇 |
2012年 | 1455篇 |
2011年 | 1956篇 |
2010年 | 1712篇 |
2009年 | 2197篇 |
2008年 | 1869篇 |
2007年 | 1836篇 |
2006年 | 1672篇 |
2005年 | 1493篇 |
2004年 | 1381篇 |
2003年 | 1334篇 |
2002年 | 1284篇 |
2001年 | 1223篇 |
2000年 | 1165篇 |
1999年 | 1238篇 |
1998年 | 1166篇 |
1997年 | 1137篇 |
1996年 | 994篇 |
1995年 | 858篇 |
1994年 | 800篇 |
1993年 | 699篇 |
1992年 | 627篇 |
1991年 | 557篇 |
1990年 | 532篇 |
1989年 | 490篇 |
1988年 | 404篇 |
1987年 | 455篇 |
1986年 | 382篇 |
1985年 | 445篇 |
1984年 | 480篇 |
1983年 | 457篇 |
1982年 | 440篇 |
1981年 | 389篇 |
1980年 | 381篇 |
1979年 | 341篇 |
1978年 | 345篇 |
1977年 | 310篇 |
1976年 | 309篇 |
1975年 | 302篇 |
1974年 | 264篇 |
1973年 | 278篇 |
排序方式: 共有10000条查询结果,搜索用时 437 毫秒
41.
An updated Lagrangian finite-element formulation has been developed for time-dependent problems of soil consolidation involving finite deformations. Large plastic strains as well as rotations occur in such problems and nominal stress measures are introduced in the formulation to redefine stresses. This leads to corrective terms for equilibrium and yield violations in addition to geometric stiffening terms in the governing integral equations. The soil is considered to be either a linear elastic or an elastoplastic, critical-state material. Some simple numerical examples are studied to validate the formulation, followed by a detailed analysis of the problem of penetration of a pile into soil. The results of this problem are viewed with emphasis on the physical interpretation and practical significance. 相似文献
42.
43.
44.
概略地叙述了西宁地区的泥石流形成条件和形成机理,并将西宁地区泥石流划分为稀性泥石流类及泥石质泥石流种类。在此基础上提出防治泥石流灾害的意见。 相似文献
45.
46.
47.
48.
We have derived the galaxy luminosity function in various regions of the cluster of galaxies Abell 496 from a wide field image
in the I band. A Schechter function fit in the 17≤ IAB ≤22(–19.5≤ MIAB ≤ –14.5) magnitude interval gives a steep power law index, which is somewhat steeper in the outer regions than in the inner
zones. This result agrees with previous findings obtained by several teams on the Coma cluster and can be interpreted as due
to the fact that faint galaxies are accreted by large ones in the central regions.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
49.
The Siberian Solar Radio Telescope: the current state of the instrument,observations, and data 总被引:2,自引:0,他引:2
Grechnev V.V. Lesovoi S.V. Smolkov G. Ya. Krissinel B.B. Zandanov V.G. Altyntsev A.T. Kardapolova N.N. Sergeev R.Y. Uralov A.M. Maksimov V.P. Lubyshev B.I. 《Solar physics》2003,216(1-2):239-272
The Siberian Solar Radio Telescope (SSRT) is one of the world's largest solar radio heliographs. It commenced operation in
1983, and since then has undergone several upgrades. The operating frequency of the SSRT is 5.7 GHz. Since 1992 the instrument
has had the capability to make one-dimensional scans with a high time resolution of 56 ms and an angular resolution of 15 arc sec.
Making one of these scans now takes 14 ms. In 1996 the capability was added to make full, two-dimensional images of the solar
disk. The SSRT is now capable of obtaining images with an angular resolution of 21 arc sec every 2 min. In this paper we describe
the main features and operation of the instrument, particularly emphasizing issues pertaining to the imaging process and factors
limiting data quality. Some of the data processing and analysis techniques are discussed. We present examples of full-disk
solar images of the quiet Sun, recorded near solar activity minimum, and images of specific structures: plages, coronal bright
points, filaments and prominences, and coronal holes. We also present some observations of dynamic phenomena, such as eruptive
prominences and solar flares, which illustrate the high-time-resolution observations that can be done with this instrument.
We compare SSRT observations at 5.7 GHz, including computed `light curves', both morphologically and quantatively, with observations
made in other spectral domains, such as 17 GHz radio images, Hα filtergrams and magnetograms, extreme-ultraviolet and X-ray
observations, and dynamic radio spectra. 相似文献
50.