全文获取类型
收费全文 | 7181篇 |
免费 | 1781篇 |
国内免费 | 1178篇 |
专业分类
测绘学 | 397篇 |
大气科学 | 979篇 |
地球物理 | 2874篇 |
地质学 | 3425篇 |
海洋学 | 678篇 |
天文学 | 611篇 |
综合类 | 333篇 |
自然地理 | 843篇 |
出版年
2024年 | 40篇 |
2023年 | 98篇 |
2022年 | 213篇 |
2021年 | 276篇 |
2020年 | 276篇 |
2019年 | 418篇 |
2018年 | 444篇 |
2017年 | 509篇 |
2016年 | 577篇 |
2015年 | 598篇 |
2014年 | 632篇 |
2013年 | 682篇 |
2012年 | 538篇 |
2011年 | 533篇 |
2010年 | 532篇 |
2009年 | 391篇 |
2008年 | 419篇 |
2007年 | 330篇 |
2006年 | 274篇 |
2005年 | 264篇 |
2004年 | 238篇 |
2003年 | 267篇 |
2002年 | 347篇 |
2001年 | 295篇 |
2000年 | 236篇 |
1999年 | 147篇 |
1998年 | 80篇 |
1997年 | 83篇 |
1996年 | 60篇 |
1995年 | 68篇 |
1994年 | 58篇 |
1993年 | 49篇 |
1992年 | 32篇 |
1991年 | 26篇 |
1990年 | 15篇 |
1989年 | 19篇 |
1988年 | 13篇 |
1987年 | 7篇 |
1986年 | 4篇 |
1985年 | 12篇 |
1984年 | 4篇 |
1983年 | 8篇 |
1982年 | 6篇 |
1980年 | 3篇 |
1979年 | 4篇 |
1978年 | 4篇 |
1977年 | 2篇 |
1972年 | 1篇 |
1958年 | 2篇 |
1957年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
41.
42.
饶文 《测绘与空间地理信息》2017,40(9)
"天地图·永定"是永定区统一、权威、标准的地理信息公共平台,本文利用"天地图·永定"提供的丰富的数据服务和二次开发接口,开发了永定旅游地图服务网,实现了永定旅游服务和"天地图"的融合,为游客提供便捷、丰富的旅游服务,对永定区的旅游发展起到了一定的推动作用。 相似文献
43.
The ever‐increasing population in cities intensifies environmental pollution that increases the number of asthmatic patients. Other factors that may influence the prevalence of asthma are atmospheric parameters, physiographic elements and personal characteristics. These parameters can be incorporated into a model to monitor and predict the health conditions of asthmatic patients in various contexts. Such a model is the base for any asthma early warning system. This article introduces a novel ubiquitous health system to monitor asthmatic patients. Ubiquitous systems can be effective in monitoring asthmatic patients through the use of intelligent frameworks. They can provide powerful reasoning and prediction engines for analyzing various situations. Our proposed model encapsulates several tools for preprocessing, reasoning and prediction of asthma conditions. In the preprocessing phase, outliers in the atmospheric datasets were detected and missing sensor data were estimated using a Kalman filter, while in the reasoning phase, the required information was inferred from the raw data using some rule‐based inference techniques. The asthmatic conditions of patients were predicted accurately by a Graph‐Based Support Vector Machine in a Context Space (GBSVMCS) which functions anywhere, anytime and with any status. GBSVMCS is an improved version of the common Support Vector Machine algorithm with the addition of unlabeled data and graph‐based rules in a context space. Based on the stored value for a patient's condition and his/her location/time, asthmatic patients can be monitored and appropriate alerts will be given. Our proposed model was assessed in Region 3 of Tehran, Iran for monitoring three different types of asthma: allergic, occupational and seasonal asthma. The input data to our system included air pollution data, the patients’ personal information, patients’ locations, weather data and geographical information for 270 different situations. Our results showed that 90% of the system's predictions were correct. The proposed model also improved the estimation accuracy by 15% in comparison to conventional methods. 相似文献
44.
45.
46.
47.
48.
49.
50.
GPS Solutions - Frequency division multiplexing of GLONASS signals causes inter-frequency bias (IFB) in receiving equipment. IFB significantly increases the difficulties of fixing GLONASS... 相似文献