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991.
河外射电源光学对应体的“自行”和岁差常数 总被引:1,自引:0,他引:1
本文用有较长观测间隔的射电源光学对应体的光学观测结果,再次讨论了岁差常数值。由于现用岁差值的不精确,需把这些射电源光学对应体在不同历元的观测结果统一归化到共同参考系统J2000.0,并对它们各自的参考星表都归化到FK5系统,即可得到这些源在FK5系统中的所谓“自行”.由所得“自行”对岁差常数的改正作了估计。本文还分别对44颗源和25颗源作了估算,其相应的岁差改正为-2.67±1.33mas/年和-3.31±1.62mas/年,将这些值和由新技术观测所得结果作了比较,两者之间符合得相当好。 相似文献
992.
S. P. Ellingsen S. S. Shabala S. E. Kurtz 《Monthly notices of the Royal Astronomical Society》2005,357(3):1003-1012
We have used the Australia Telescope Compact Array (ATCA) to make observations of a sample of eight young ultra-compact H ii regions, selected on the basis that they have associated class II methanol maser emission. We have made observations sensitive to both compact and extended structures and find both to be present in most sources. The scale of the extended emission in our sample is in general less than that observed towards samples based on IRAS properties, or large single-dish flux densities. Our observations are consistent with a scenario where extended and compact radio continuum emission co-exists within H ii regions for a significant period of time.
We suggest that these observations are consistent with a model where H ii evolution takes place within hierarchically structured molecular clouds. This model, which is the subject of an upcoming companion paper by Shabala et al., addresses both the association between compact and extended emission and the ultra-compact H ii region lifetime problem. 相似文献
We suggest that these observations are consistent with a model where H ii evolution takes place within hierarchically structured molecular clouds. This model, which is the subject of an upcoming companion paper by Shabala et al., addresses both the association between compact and extended emission and the ultra-compact H ii region lifetime problem. 相似文献
993.
994.
Based on a comprehensive analysis of the October 25, 1994 event, we consider the balance of energetic particles in a type-IV solar radio emission source with a zebra-type fine structure (in a coronal magnetic loop). The zebra pattern is formed through the injection of fast electrons into a trap and the formation of a ring-type nonequilibrium electron distribution function. We estimated the characteristic zebra-pattern lifetime, which is determined by the escape of fast particles from the trap into the loss cone. In addition, we determined the number of fast particles that must be injected into the trap to provide the observed radio brightness temperature in zebra-pattern stripes by analyzing the plasma emission mechanism responsible for the zebra-pattern generation. As a result, we estimated the efficiency of the electron acceleration mechanism in coronal magnetic loops at the post-flare evolutionary phase of an active region. 相似文献
995.
996.
视超光速源的统计分析 总被引:2,自引:0,他引:2
本文收集了视超光速源样本的有关观测数据,在同步加速自康普顿散射机制下导出了各源的多普勒因子,再利用视超光速源的相对论射束模型计算样本源的有关物理量,如射电光度和亮温度,并与它们的观测值作直接的比较,得到较好的相关结果。这些结果支持了活动星系核中具有相对论射束运动的假设。同时我们比较了样本源的射电、光学、X射线的发现它们之间有一定的相关性,说明在不同波段上的辐射机制可能存在某种联系。 相似文献
997.
郑州市区的地下热水来自增温地层,在使用电法勘探确定热水层位和埋深时,用五极纵轴测深法与对称四极测深法相结合,取得了良好的地质效果。 相似文献
998.
弱磁化相对论电子束注入等离子体时,由非共振波粒相互作用激发的束-等离子体不稳定性可以直接放大电磁波,计算结果表明:在偏离共振条件的区域,电磁波仍可在较宽的频率范围被放大,并在每个共振峰下形成平台结构。随着谐波数的增高,增长率峰值逐渐变小,峰宽也变窄。本文还分析了电磁波的增长率随背景参数ω_(pe)/Ω_e及高能电子的入射方向和辐射方向的变化规律,在典型的日冕条件下,此类不稳定性所放大的电磁波的增长率大小、带宽、方向性、偏振及谐波等性质,可以用来解释太阳Ⅲ型射电爆发现象,本文的研究亦可用来解释其他天体等离子体辐射。 相似文献
999.
Rakesh K. Malik Pradeep Gothoskar P. K. Manohran G. Swarup K. Subramanian V. Balasubramanian 《Journal of Astrophysics and Astronomy》1995,16(3-4):393-398
Jupiter flux at 327 MHz was monitored using the Ooty radio telescope from July 12th to July 29th during the collision of comet
Shoemaker-Levi 9 with Jupiter. Flux was found to increase steadily from July 17th to July 26th by ∼ 2–5 Jy, after which it
declined to its pre-event value. The comparison of 327 MHz observations with those at 840 MHz and 2240 MHz indicates that
the enhancement was mainly due to the increased synchrotron emission and the contribution of thermal emission was very small
at metric-decimetric frequencies. The enhancement in radio emission was found to be more at 840 MHz than at 327 or 2240 MHz.
The steepening of the spectrum between 327 and 840 MHz as well as between 2240 and 840 MHz was also noted. 相似文献
1000.
Susanne Aalto 《Astrophysics and Space Science》2005,295(1-2):143-153
The molecular phase of the ISM constitutes the main source of fuel for the activity in starburst and AGNs. The physical conditions and chemical constitution of the molecular gas will change with, and respond to, the evolution of the activity. This paper includes a short discussion of the 12CO/13CO 1–0 line intensity ratio as a diagnostic tool of the molecular gas properties of luminous galaxies – paired with examples of high-resolution studies of how the line ratio varies within galaxies. A possible connection between the OH megamasers and galaxies with unusually high 12CO/13CO 1–0 line intensity ratios are also briefly discussed.The relative intensities of the dense gas tracers HNC, HCN, HCO+ and CN are a result of both chemistry and starburst evolution. The discussion on the interpretation of HNC 1–0 emission includes the importance of ion-neutral chemistry in a luminous starburst region. Finally, simple cartoon ISM models and how they can be applied to LIRGs and ULIRGs, are presented. 相似文献