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951.
提出一种基于异步比较法产生空满标志位,并利用锁存器实现标志位与时钟同步的FIFO,同时还给出了相应的Verilog HDL代码。该方法能提高时钟频率,节约版图面积。 相似文献
952.
Heating and acceleration of electrons in solar impulsive hard X-ray (HXR) flares are studied according to the two-stage acceleration model developed by Zhang for solar 3He-rich events. It is shown that electrostatic H-cyclotron waves can be excited at a parallel phase velocity less than about the electron thermal velocity and thus can significantly heat the electrons (up to 40 MK) through Landau resonance. The preheated electrons with velocities above a threshold are further accelerated to high energies in the flare-acceleration process. The flare-produced electron spectrum is obtained and shown to be thermal at low energies and power law at high energies. In the non-thermal energy range, the spectrum can be double power law if the spectral power index is energy dependent or related. The electron energy spectrum obtained by this study agrees quantitatively with the result derived from the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) HXR observations in the flare of 2002 July 23. The total flux and energy flux of electrons accelerated in the solar flare also agree with the measurements. 相似文献
953.
Traditionally, the mid-Holocene in most parts of China was thought to be warmer with higher precipitation, resulting from a strong Asian summer monsoon. However, some recent researches have proposed a mid-Holocene drought interval of millennial-scale in East Asian monsoon margin areas. Thus whether mid-Holocene was dry or humid remains an open issue. Here, Zhuyeze palaeolake, the terminal lake of the Shiyang River Drainage lying in Asian monsoon marginal areas, was selected for reconstructing the details of climate variations during the Holocene, especially mid-Holocene, on the basis of a sedimentological analysis. Qingtu Lake (QTL) section of 6.92m depth was taken from Zhuyeze palaeolake. Multi-proxy analysis of QTL section, including grain size, carbonate, TOC, C/N and δ13C of organic matter, was used to document regional climatic changes during 9-3 cal ka B.P. The record shows a major environmental change at 9.0-7.8 cal ka B.P., attributed to a climate trend towards warmth and humidity. This event was followed by a typical regional drought event which occurred during 7.8-7.5 cal ka B.P. And a warm and humid climate prevailed from 7.5 to 5.0 cal ka B.P., attributed to the warm/humid Holocene Optimum in this region. After that, the climate gradually became drier. Moreover, comparison of the climate record from this paper with the summer insolation at 30°N indicates that the climate pattern reflecting the Asian monsoon changes was caused by insolation change. 相似文献
954.
�������۲�̨��λ���Ӱ��ķ����о� 总被引:3,自引:3,他引:0
??о??????????????й????????λ???????????,???????????????????????\,3?????????????19????λ?????????????6???λ??????????????????????????????????????????????????????????????λ???????????????????????????λ??????????????????????????????????С???3?????????????????????????????????????????????????????λ???С??1%?????λ??????????????;???λ????1%??????????????????????0.4%????;??λ????1%~10%??????????????????????涨λ????????????????????????????????2.5????? 相似文献
955.
Ji Yang Jie-Long Zhang Zhi-Yong Cai Deng-Rong Lu You-Heng Tan Purple Mountain Observatory Chinese Academy of Sciences Nanjing Key Laboratory of Particle Astrophysics Institute of High-Energy Physics Chinese Academy of Sciences Beijing National Astronomical Observatories Chinese Academy of Sciences Beijing 《中国天文和天体物理学报》2006,6(2):210-216
The distribution of dense molecular gas around the supernova remnant G40.5-0.5 has been investigated by radio spectroscopic observations in the CO (J = 1-0) transition. The molecular gas is found to extend over the entire region of G40.5-0.5. A molecular shell, with a diameter of - 26', coincides with the ionized gas as revealed by the cm-radio observations. This coincidence, along with the velocity discontinuity following the shell, provides direct evidence for interaction between the ionized gas and the dense molecular gas. No clear evidence for cosmic-ray acceleration can be identified from this SNR as previously suggested, due to positional uncertainty in relating the SNR shell defined by CO to the EGRET gamma-ray sources, GRO J1904 06, from the gamma-ray observations. 相似文献
956.
957.
本文分析γ射线脉冲星最近的观测数据,研究各波段辐射位相的一些关联,它们对于揭示γ射线脉冲星的辐射机制可能有重要的意义, 相似文献
958.
An RS CVn star is considered as non-synchronous if its orbital period differs by more than 4% from its photometric period. Of 88 systems examined according to this criterion, 67 are synchronous, 21 are non-synchronous. For the 21 non-synchronous systems, we find their spectral types are most around KO-2 III, that their orbital eccentricities are larger and their chromospheric activity lower than the average level. 相似文献
959.
The limb darkening effect on the measurement of stellar rotation is discussed in this paper. It is shown that this effect plays an important role in the measurement of Ve sin i. In the extreme case with the limb darkening coefficient of 1.0, it may cause a difference up to 17%. As a sequel to paper [1], this work presents the following new explanation for the systematic differences between Slettebak's new and old systems. The main causes of the systematic differences are: (1) The old system made an inadequate twice repeated correction for the limb darkening. (2) Owing to the historical reason, the old system used too large limb darkening coefficients. 相似文献
960.
昆仑山口西Ms8.1地震的地壳变形特征 总被引:33,自引:15,他引:18
利用全球定位系统1991-2001年及震后4期GPS观测数据。获得了2001年11月14日昆仑山口西地震(Ms8.1)的同震和震后形变运动图像,跨破裂带GPS网最近两点测得的最大同震形变为1.9m左右,而震后4个月断层蠕滑引起的变形约为80mm,破裂带两侧震后变形幅度具有非对称性。南侧震后变形基本是北侧的2-3倍。研究结果显示破裂带南盘在震后向偏东方向有明显移动,预示本次地震后能量的重新分配与积累,根据近几十年以来东昆仑断裂带的大地震由西向东扩展的特点,未来地震有向东迁移的可能。 相似文献