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981.
982.
该文对1992—2011年的酸雨观测资料中存在的pH测量负偏差进行统计分析。结果显示:除西北地区、青藏高原外的大部分酸雨观测站不同程度地出现pH值测量负偏差,总体上南方地区台站的pH测量负偏差问题较北方地区突出;随着测量仪器的更新换型、观测业务规范化管理水平的提升以及一些针对性技术措施的实施,存在pH测量负偏差问题的观测台站比例从20世纪90年代的40%以上下降为25%,观测资料中受pH测量负偏差影响的数据比例由10%下降到2%。pH负偏差的量值与降水pH值之间存在一定依存关系:降水pH值越低,负偏差问题越严重,pH负偏差的主要量值分布区间为-0.6~0,约占负偏差数据的80%。 相似文献
983.
984.
深海在黑暗、高静水压、低温(黑烟囱等热液系统除外)和寡营养的极端环境下形成了特殊的生境。对深海生物/微生物的研究,不仅可以揭示各种深海生物的生理代谢特性和动态变化规律,而且有助于深海生物资源的开发利用,特别是深海微生物碳循环机制的相关研究可为全球实现碳中和目标提供新的路线图。研究深海生物的首要条件是获得大量保持原位特性的样本,然而传统深海采样手段的局限可能导致深海相关研究结果无法反映深海环境下真实的生命过程,亟需发展满足深海生物原位研究的采样方法和生态监测技术。本文对深海生物研究现状,相关科学问题和原位组学研究进展,以及原位生态监测装备研发和应用进行综述,并对深海原位生物实验室进行了展望。 相似文献
985.
长毛对虾酸性磷酸酶功能基团的研究(Ⅱ) 总被引:1,自引:0,他引:1
用化学修饰剂pCMB、NBS、K试剂修饰长毛对虾Penaeuspenicilla-tusAlcock酸性磷酸酶(ACPase,EC3.1.3.2),在修饰剂作用下,酶活力明显下降,健康虾酶对修饰剂的敏感性(NBS除外)大都稍大于病虾酶。修饰酶的紫外280um吸收光谱以及荧光340um发射光谱的变化,表明酶活力下降的同时酶构象也产生相应的变化。结果表明,酶分子的半胱氨酸残基、色氨酸残基以及门冬氨酸、谷氨酸β或γ验基与酶活力有关,是酶的催化功能基团。 相似文献
986.
R. Errmann R. Neuhuser L. Marschall G. Torres M. Mugrauer W.P. Chen S.C.‐L. Hu C. Briceno R. Chini . Bukowiecki D.P. Dimitrov D. Kjurkchieva E.L.N. Jensen D.H. Cohen Z.‐Y. Wu T. Pribulla M. Vako V. Krushevska J. Budaj Y. Oasa A.K. Pandey M. Fernandez A. Kellerer C. Marka 《Astronomische Nachrichten》2013,334(7):673-681
With an apparent cluster diameter of 1.5° and an age of 4 Myr, Trumpler 37 is an ideal target for photometric monitoring of young stars as well as for the search of planetary transits, eclipsing binaries and other sources of variability. The YETI consortium has monitored Trumpler 37 throughout 2010 and 2011 to obtain a comprehensive view of variable phenomena in this region. In this first paper we present the cluster properties and membership determination as derived from an extensive investigation of the literature. We also compared the coordinate list to some YETI images. For 1872 stars we found literature data. Among them 774 have high probability of being member and 125 a medium probability. Based on infrared data we re‐calculate a cluster extinction of 0.9–1.2 mag. We can confirm the age and distance to be 3–5 Myr and870 pc. Stellar masses are determined from theoretical models and the mass function is fitted with a power‐law index of α = 1.90 (0.1–0.4 M⊙) and α = 1.12 (1–10 M⊙). (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
987.
Although magnetic fields have been discovered in ten massive O‐type stars during the last years, the origin of their magnetic fields remains unknown. Among the magnetic O‐type stars, two stars, HD 36879 and HD 57682, were identified as candidate runaway stars in the past, and θ1 Ori C was reported to move rapidly away from its host cluster. We search for an explanation for the occurrence of magnetic fields in O‐type stars by examining the assumption of their runaway status. We use the currently best available astrometric, spectroscopic, and photometric data to calculate the kinematical status of seven magnetic O‐type stars with previously unknown space velocities. The results of the calculations of space velocities suggest that five out of the seven magnetic O‐type stars can be considered as candidate runaway stars. Only two stars, HD 155806 and HD 164794, with the lowest space velocities, are likely members of Sco OB4 and NGC 6530, respectively. However, the non‐thermal radio emitter HD 164794 is a binary system with colliding winds, for which the detected magnetic field has probably a different origin in comparison to other magnetic O‐type stars (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
988.
利用斯隆数字巡天(SDSS)第8次释放数据(DR8)的恒星光谱数据及2MASS(Two Micro All Sky Survey)近红外点源测光数据研究著名的疏散星团NGC 6791,得到该星团的视向速度与金属丰度分别为Vr=-46.4±0.2 km·s-1和[Fe/H]=0.32±0.11dex.利用星团中红团簇巨星作为理想"标准烛光",结合2MASS近红外点源测光数据计算了该星团的绝对距离模数为(m-M)0=13.02±0.08 mag或4.02±0.15 kpc.与其他研究者给出的结果进行了比较,金属丰度、视向速度及绝对距离模数都符合得比较好.主要结论有3点:(1)NGC 6791是个极度富金属的星团;(2)在SDSS的光谱分辨能力以内,分离出的87颗团星之间不存在明显的金属丰度差异;(3)得到的距离模数对年龄、金属丰度及尘埃消光不敏感,是一种可靠的间接测量. 相似文献
989.
The components of binary stars offer the potential to examine the predictions of stellar‐evolution theory with particularly tight constraints. Those constraints are further tightened when the binary belongs to a cluster whose properties have been well determined independently. 12 Comae presents both advantages, belonging as it does to the Coma Cluster, Melotte 111. The orbit of 12 Comae has an eccentricity of nearly 0.6 and a period of 13 months. By a process of subtraction we separate the spectra of the component stars, derive a precise double‐lined orbit solution, and by modelling the photometry we extract the individual stellar photometric and physical properties, ages and rotation. By fitting theoretical evolutionary tracks to the positions of the stars in the H‐R diagram we confirm their individual masses, and derive a ZAMS of ∼0.65 Gyr, which accords well with measurements published for the cluster itself. We show that the primary of 12 Comae is an evolving giant of spectral type ∼G7 and mass 2.6 M⊙, while its secondary (whose spectrum could be isolated particularly cleanly) is an A3 dwarf which has a mass of 2.05 M⊙ and has commenced its evolution away from the main sequence. There is evidence that both stars are slightly metal‐weak (–0.25 < [Fe/H] < 0.0), well in keeping with analyses of other members of this cluster (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
990.
The stellar spectroscopic data of SDSS-DR8 (The Eighth Data Release of Sloan Digital Sky Survey) and the near-infrared photometric data of 2MASS (Two Micron All Sky Survey) point sources are used to analyze the fundamental parameters of the open cluster NGC 6791. Using the radial velocities of 274 stars in the region of the cluster, we calculate the membership probability for each star with the maximum likelihood method. Based on the stars with high membership probabilities, we have derived the radial velocity and metal abundance of the cluster to be respectively Vr =−46.4±0.2 km·s−1 and [Fe/H]=0.32±0.11dex, in good agreement with the results obtained by other authors on the basis of high-resolution spectroscopy. Using red clump giants in the cluster as “standard candle”, we have derived the absolute distance modulus of the cluster to be (m − M)0 =13.02±0.08mag or 4.02±0.15 kpc in distance, consistent with the values obtained from main-sequence fittings by some authors. And our main conclusions are: (1) NGC 6791 is extremely metal-rich; (2) Within the spectral resolution of SDSS, the discriminated 87 cluster members have no evident difference in matallicity; (3) The obtained distance modulus is insensitive to the age, metallicity and dust distinction, so it is a kind of reliable indirect measurement. 相似文献