全文获取类型
收费全文 | 34581篇 |
免费 | 7218篇 |
国内免费 | 8303篇 |
专业分类
测绘学 | 2422篇 |
大气科学 | 6898篇 |
地球物理 | 9950篇 |
地质学 | 16930篇 |
海洋学 | 4652篇 |
天文学 | 1833篇 |
综合类 | 3203篇 |
自然地理 | 4214篇 |
出版年
2024年 | 161篇 |
2023年 | 529篇 |
2022年 | 1404篇 |
2021年 | 1714篇 |
2020年 | 1409篇 |
2019年 | 1700篇 |
2018年 | 1903篇 |
2017年 | 1853篇 |
2016年 | 2105篇 |
2015年 | 1926篇 |
2014年 | 2203篇 |
2013年 | 2472篇 |
2012年 | 2196篇 |
2011年 | 2237篇 |
2010年 | 2306篇 |
2009年 | 2077篇 |
2008年 | 1957篇 |
2007年 | 1906篇 |
2006年 | 1490篇 |
2005年 | 1384篇 |
2004年 | 1057篇 |
2003年 | 1064篇 |
2002年 | 1042篇 |
2001年 | 1038篇 |
2000年 | 1093篇 |
1999年 | 1391篇 |
1998年 | 1153篇 |
1997年 | 1124篇 |
1996年 | 1059篇 |
1995年 | 919篇 |
1994年 | 805篇 |
1993年 | 711篇 |
1992年 | 577篇 |
1991年 | 412篇 |
1990年 | 317篇 |
1989年 | 291篇 |
1988年 | 264篇 |
1987年 | 146篇 |
1986年 | 149篇 |
1985年 | 95篇 |
1984年 | 74篇 |
1983年 | 77篇 |
1982年 | 67篇 |
1981年 | 54篇 |
1980年 | 47篇 |
1979年 | 42篇 |
1978年 | 18篇 |
1977年 | 12篇 |
1975年 | 12篇 |
1958年 | 26篇 |
排序方式: 共有10000条查询结果,搜索用时 390 毫秒
981.
编 制 《中国 北 方岩 溶充 水 煤矿 区矿 床 水文 地质 图 集》的目 的主 要 是为 了合 理 开发 煤炭 资 源和 利用 煤 系 基 盘中奥 陶 统 灰岩 地 下 水 ;图 中 内 容应 力 求 充 分反 映 矿 区 不同 充 水 类 型的 充 水 特 征、充 水程 度 、水质 好 坏 及 可利 用 的 水 量 ,为 矿山 综 合防 治水 和 排供 结合 宏 观决 策提 供 所需 的水 文 地质 依据 。 相似文献
982.
983.
为详细了解崇明越江通道南港隧道段地层情况 ,设计要求提供长江水域静探资料。简介了我院水域静力触探设备的研制和应用情况 相似文献
984.
基于小波变换的图像压缩方法能在高压缩比的前提下保持好的重建图像质量,它的多分辨率特性与人类视觉系统非常相近,小波变换的编码技术被广泛地应用于遥感影像的压缩中。介绍了小波理论的相关知识,着重对嵌入零树小波、等级树分割、小波数据的形态学表示算法等方法进行了详细的论述,并对图像编码技术的发展方向进行了展望。 相似文献
985.
陈培善 《地震学报(英文版)》2004,17(2):251-253
Illustration
All the data in this catalog are chosen from the Preliminary Seismological Report of Chinese Seismic Stations (abbreviated to Monthly Report). The catalog includes the events of M≥4.7 in and near China and M≥6 all over the world. The Monthly Report is monthly compiled by the Ninth Section of Institute of Geophysics, China Earthquake Administration (CEA). 相似文献
986.
Estimation of Site Effects in Beijing City 总被引:6,自引:0,他引:6
— For the realistic modeling of the seismic ground motion in lateral heterogeneous anelastic media, the database of 3-D geophysical structures for Beijing City has been built up to model the seismic ground motion in the City, caused by the 1976 Tangshan and the 1998 Zhangbei earthquakes. The hybrid method, which combines the modal summation and the finite-difference algorithms, is used in the simulation. The modeling of the seismic ground motion, for both the Tangshan and the Zhangbei earthquakes, shows that the thick Quaternary sedimentary cover amplifies the peak values and increases the duration of the seismic ground motion in the northwestern part of the City. Therefore the thickness of the Quaternary sediments in Beijing City is the key factor controling the local ground effects. Four zones are defined on the base of the different thickness of the Quaternary sediments. The response spectra for each zone are computed, indicating that peak spectral values as high as 0.1 g are compatible with past seismicity and can be well exceeded if an event similar to the 1697 Sanhe-Pinggu occurs. 相似文献
987.
Hu Yi-li Xu Jun Duan Yong-kong Xu Zhao-yong Yang Run-hai Zhao Jin-ming 《地震学报(英文版)》2004,17(6):725-734
A new method of detecting the vertical bearing capacity for single-pile with high strain is discussed in this paper. A heavy
hammer or a small type of rocket is used to strike the pile top and the detectors are used to record vibration graphs. An
expression of higher degree of strain (deformation force) is introduced. It is testified theoretically that the displacement,
velocity and acceleration cannot be obtained by simple integral acceleration and differential velocity when long displacement
and high strain exist, namely when the pile phase generates a whole slip relative to the soil body. That is to say that there
are non-linear relations between them. It is educed accordingly that the force P and displacement S are calculated from the amplitude of wave train and (dynamic) P-S curve is drew so as to determine the yield points. Further, a method of determining the vertical bearing capacity for single-pile
is discussed. A static load test is utilized to check the result of dynamic test and determine the correlative constants of
dynamic-static P(Q)-S curve.
Foundation item: Key projects of the tenth Five-year Plan of Yunnan Province (documented Yunnan district [2002]54-02-02) and Geophysical
Society of Yunnan Province. 相似文献
988.
Problem on development control of marine source bed hold in Chinese petroleum industry progression. The Hongshuizhuang Formation,Tieling Formation and Xiamaling Formation in the Middle and Upper Proterozoic are important hydrocarbon source beds in northern North China, and investigation of their sedimentary environments and the controls has great significance for petroleum exploration in North China. Based on sedimentology (sequence stratigraphy), palaeoecology, sedimentary geochemistry, and sedimentary palaeogeography, their development pattern is discussed. All these studies indicate that the development controls of the hydrocarbon source beds include a favorite palaeogeographic location, exceeding propagation of biomes in low and middle latitudes, anoxic environments, enrichment of phosphorus element and the adsorption of clay minerals during the preservation of organic matter in the marine carbonates. 相似文献
989.
Estimation of annual actual evapotranspiration from nonsaturated land surfaces with conventional meteorological data 总被引:1,自引:0,他引:1
QIU Xinfa ZENG Yan MIAO Qilong & YU Qiang . Department of Geography Nanjing Institute of Meteorology Nanjing China . Institute of Geographic Sciences Natural Resources Research Chinese Academy of Sciences Beijing China 《中国科学D辑(英文版)》2004,47(3)
Land surface evapotranspiration is an important component both in earth surface heat and water bal-ance, on whose budgets weather and climate depend, to a great extent, for their changes are responsible for the formation and variation of vegetation features on the globe. Besides, the evapotranspiration is an im-portant topic of short-term flood forecasting and the estimation of runoff from mountainous sides. As a result, the problem as to the evapotranspiration has been one of the concerns in … 相似文献
990.
GE Heping SUN Yan LU Xiancai ZHU Wenbin GUO Jichun LIU Deliang & Chi-yuen Wang . Department of Earth Sciences Nanjing University State Key Laboratory of Mineral Deposit Nanjing China . Department of Earth Space Sciences University of Science Technology of China Hefei China . Department of Geology Geophysics University of California Berkeley CA USA 《中国科学D辑(英文版)》2004,47(3)
In the 1990s of the 20th century, we participated in the research of the stress field in fissure tectonics of scientific deep bore cores for the Deep Observation and Sampling of the Earths Continental Crust (DOSECC for short). Spherical and enriched ul-tra-micro granular textures (nm size), which enriches Nb element (Wang & Sun, 1990; Sun & Wang, 1993)[1,2], were found during the observation of ul-tra-micro slipping lamellae of ductile and brittle oc-curring in Late Mesozoic granites us… 相似文献