全文获取类型
收费全文 | 35883篇 |
免费 | 5980篇 |
国内免费 | 7963篇 |
专业分类
测绘学 | 3386篇 |
大气科学 | 4500篇 |
地球物理 | 6227篇 |
地质学 | 20568篇 |
海洋学 | 4069篇 |
天文学 | 3369篇 |
综合类 | 2289篇 |
自然地理 | 5418篇 |
出版年
2024年 | 246篇 |
2023年 | 642篇 |
2022年 | 1282篇 |
2021年 | 1485篇 |
2020年 | 1357篇 |
2019年 | 1686篇 |
2018年 | 1196篇 |
2017年 | 1418篇 |
2016年 | 1468篇 |
2015年 | 1623篇 |
2014年 | 2027篇 |
2013年 | 2001篇 |
2012年 | 2118篇 |
2011年 | 2228篇 |
2010年 | 1961篇 |
2009年 | 2473篇 |
2008年 | 2376篇 |
2007年 | 2432篇 |
2006年 | 2394篇 |
2005年 | 2255篇 |
2004年 | 1978篇 |
2003年 | 1880篇 |
2002年 | 1644篇 |
2001年 | 1424篇 |
2000年 | 1460篇 |
1999年 | 1275篇 |
1998年 | 1098篇 |
1997年 | 790篇 |
1996年 | 675篇 |
1995年 | 569篇 |
1994年 | 540篇 |
1993年 | 454篇 |
1992年 | 325篇 |
1991年 | 285篇 |
1990年 | 197篇 |
1989年 | 160篇 |
1988年 | 132篇 |
1987年 | 78篇 |
1986年 | 38篇 |
1985年 | 32篇 |
1984年 | 19篇 |
1983年 | 15篇 |
1982年 | 11篇 |
1981年 | 9篇 |
1980年 | 8篇 |
1979年 | 7篇 |
1978年 | 14篇 |
1977年 | 5篇 |
1976年 | 4篇 |
1954年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
121.
讨论运用PCI 9054(美国PLX公司生产的接口芯片)作为接口芯片的PCI(Peripheral Component Interconnect)板卡的软硬件设计,以实现天线跟踪的两个时间同步中断。利用标准秒信号中断作为系统时钟同步信号,并同步产生时间间隔为20ms(或40、50ms,可选)的中断信号,来处理天线跟踪指令输出。中断信号通过PCI中断口INTA#接入计算机,在驱动中识别不同的中断信号,并在应用程序响应中断处理后,命令ACU(Antenna Control Unit)机,实现射电天文望远镜的同步跟踪。其控制过程分3部分阐述:硬件设计、驱动程序设计、安装及应用;着重讨论了前两者的设计方法及思路。 相似文献
122.
Alon Retter Bing Zhang Lionel Siess Amir Levinson 《Monthly notices of the Royal Astronomical Society》2006,370(3):1573-1580
V838 Mon is the prototype of a new class of objects. Understanding the nature of its multistage outburst and similar systems is challenging. So far, several scenarios have been invoked to explain this group of stars. In this work, the planets-swallowing model for V838 Mon is further investigated, taking into account the findings that the progenitor is most likely a massive B-type star. We find that the super-Eddington luminosity during the eruption can explain the fast rising times of the three peaks in the optical light curve. We used two different methods to estimate the location where the planets were consumed. There is a nice agreement between the values obtained from the luminosities of the peaks and from their rising time-scale. We estimate that the planets were stopped at a typical distance of one solar radius from the centre of the host giant star. The planets-devouring model seems to give a satisfying explanation to the differences in the luminosities and rising times of the three peaks in the optical light curve of V838 Mon. The peaks may be explained by the consumption of three planets or alternatively by three steps in the terminal falling process of a single planet. We argue that only the binary merger and the planets-swallowing models are consistent with the observations of the new type of stars defined by V838 Mon. 相似文献
123.
124.
125.
Wang Yanhui 《水文研究》1992,6(2):241-251
Black locust (Robina pseudoacacia) has become one of the most important shelter species in the loess area of northwest China. This paper summarizes recent research concerning its hydrological influence, including canopy interception, litter absorption capacity, its effect on rainfall kinetic energy, infiltration rates, surface runoff, soil moisture, and evapotranspiration, and its role in soil conservation. Several predictive models are listed. on the basis of existing results, optimum characteristics for an effective plantation are defined, and problems requiring further research are identified. 相似文献
126.
127.
Galileo系统及其在中国的应用 总被引:9,自引:0,他引:9
较详细地介绍了Galileo系统的全面体系结构、频率设计、服务内容及其广泛的应用范围,指出了它与GPS系统相比的优点,并对开发和增强Galileo系统在我国多层次、全方位的应用提出了建议。 相似文献
128.
129.
Is Precipitation the Dominant Controlling Factor of High Inorganic Nitrogen Content in the Changjiang River and Its Mouth? 总被引:1,自引:1,他引:0
沈志良 《中国海洋湖沼学报》2003,21(4):368-376
The main reasons for the high content of inorganic N and its increase by several times in the Changjiang River and its mouth during the last 40 years were analysed in this work. The inorganic N in precipitation in the Changjiang River catchment mainly comes from gaseous loss of fertilizer N, N resulting from the increases of population and livestock, and from high temperature combustions of fossil fuels. N from precipitation is the first N source in the Changjiang River water and the only direct cause of high content of inorganic N in the Changjiang River and its mouth. The lost N in gaseous form and from agriculture non-point sources fertilizer comprised about 60% of annual consumption of fertilizer N in the Changjiang River catchment and were key factors controlling the high content of inorganic N in the Changjiang River mouth. The fate of the N in precipitation and other N sources in the Changjiang River catchment are also discussed in this paper. 相似文献
130.