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991.
一种简化的Helmert方差分量估计算法 总被引:2,自引:0,他引:2
Helmert方法是通过求出两类观测值的单位方差,来修正其先验权,用迭代法最终求得正确的权。本文提出,如果已知两类观测值的单位方差之比,即可定出正确的权,从而使计算简单化。 相似文献
992.
钒的Kβ谱带精细结构的测定及钒的价态分析 总被引:3,自引:2,他引:1
用普通X射线荧光光谱仪测定了钒的氧化物、钒酸盐及含钒混合物中V的Kβ谱线,借助一套有效的谱处理程序,获得了有关Kβ谱线精细结构的谱峰参数,证实了谱线轮廓(Kβ″峰逐渐显著,Kβ5、Kβ″向高能端位移,Kβ5与Kβ1,3的分开趋势,Kβ1,3半峰宽发生变化)及谱峰参数(Kβ5峰能量,Kβ5与Kβ1,3能量差,Kβ5与Kβ1,3及Kβ″与Kβ1,3的强度比,以及Kβ5和Kβ1,3的不对称因子)与V的氧化数变化呈很强的相关性及规律性变化。 相似文献
993.
994.
钻井工程用超硬材料及钻头的发展 总被引:10,自引:0,他引:10
介绍了钻井工程用超硬复合材料(包括PDC、PCBN、陶瓷和金刚石膜)的发展现状及前景;同时也介绍了以这些材料切削具的钻头制造及应用情况;指出金刚石膜合成技术的发展已使金刚石膜制造钻井工程用切削具成为可能。 相似文献
995.
996.
Magnetostratigraphy and palaeoclimatic significance of Late Tertiary aeolian sequences in the Chinese Loess Plateau 总被引:11,自引:0,他引:11
Sun Donghuai An Zhisheng J. Shaw J. Bloemendal & Sun Youbin 《Geophysical Journal International》1998,134(1):207-212
The aeolian Red Clay sequence in the central part of the Chinese Loess Plateau was investigated in an attempt to obtain magnetostratigraphic and palaeoclimatic records. From the results, we deduce that aeolian dust accumulation and the related East Asia palaeomonsoon system began at least 7.6 Myr ago, and that the Tibetan Plateau had reached a significant elevation by that time. The Late Tertiary palaeoclimatic history of the Red Clay as reflected by magnetic susceptibility is reconstructed for the time period 7.6–2.5 Ma. Increases in aeolian dust accumulation for the last 7.6 Myr appear to have a close relation with the uplift processes of the Tibetan Plateau. The remarkable increase of aeolian dust accumulation beginning at 3.2 Ma appears to reflect the influence of an increasing global ice volume on the East Asian monsoon and aeolian dust accumulation. 相似文献
997.
The Jingtieshan deposit occurs in a Precambrian tectonic-stratigraphic terrane within the Northern Qilian Caledonian Orogen,
and is generally considered as a Superior-type iron formation. The deposit is characterized by Fe-Si-Ba and Cu mineralization
and consists of two types of orebodies, an upper jasper-barite-iron deposit and a lower copper sulfide deposit. The iron orebodies
occur as independent stratigraphic layers concordant within a thick argillaceous succession, and exhibit fine-grained textures
and well-developed sedimentary layering. The ores are predominantly composed of specularite and jasper with lesser amounts
of magnetite, hematite, siderite, and barite. The presence of barite, hematite and jasper as major components shows that the
iron ores were precipitated in a relatively oxidized ocean floor environment. The Cu orebody directly underlies the iron ore
and is hosted by chlorite-sericite-quartz phyllite. The Cu mineralization is composed of pyrite and chalcopyrite and is characterized
by stockwork. The disseminated and stockwork Cu mineralization is metamorphosed and concordant with respect to foliation,
indicating pre-fabric development, i.e. pre-metamorphism, and was probably originally formed by reduced fluids reacting at
the base of and within the oxide iron formation. Geochemical data show that the jasper-barite-iron ores, which resemble Superior-type
iron formations, have a high input of hydrothermal-hydrogeneous elements (SiO2, av.=56%; Fe2O3t, av.=30%; Mn, av.=0.45%; BaO, av.=16.7%) with minimal terrigeneous input (<15% combined Al2O3, TiO2, K2O, MgO, etc.). The δ34S of exhalative barite varies from 28 to 34‰, which is very heavy with respect to other Late Proterozoic sulfate-bearing deposits,
except those of circa 600 Ma in which the sulfides range from 8 to 20‰. The sulfur isotope data indicate that the barite was
formed by the mixing of a Ba-rich hydrothermal fluid with sulfate-rich ambient seawater and that the sulfides ores were most
probably derived from the reduction of seawater sulfate during subsurface reaction with ferrous iron-bearing minerals. These
data are consistent with the jasper-barite-iron deposit forming by hydrothermal exhalative and chemical sedimentary processes
on the floor of an ocean basin, and with the Cu mineralization forming by hydrothermal filling and replacement in base of
and within the iron formation.
Received: 19 March 1997 / Accepted: 14 May 1998 相似文献
998.
土壤磁性用于油气勘查的一个研究实例 总被引:1,自引:0,他引:1
廊坊—固安研究区内两条剖面上的已知油藏上方土壤的磁化率、天然剩磁强度、Q值的异常特征不易辨认。对油田上方土壤样品进行交变退磁清洗后,其剩磁的构成具有明显的特殊性,区别于非油藏上方土壤剩磁的构成。利用这一特点,寻找油气藏效果较好。 相似文献
999.
Processes of the deposition and vicissitude of Mu Us Desert, China since 150 ka B.P. 总被引:1,自引:0,他引:1
Li Baosheng Jin Heling Lü Haiyan Zhu Yizhi Dong Guangrong Sun Donghuai Zhang Jiashen Gao Quanzhou Yan Mancun 《中国科学D辑(英文版)》1998,41(3):248-254
“Milanggouwan stratigraphical section” named lately takes down 27 cycles of alternately evolutionary histories of desert depositions
in the Mu Us area with the fluviolacustrine facies and palaeosols since 150 ka B. P. Studies show that the sedimentary form
was induced by the growth and decline and confrontation each other between the winter monsoon and the summer monsoon of East
Asia in the past 150 ka.
Project supported by the National Natural Science Foundation of China (Grant No. 49473192). 相似文献
1000.
1996年包头西6.4级地震震兆特征的特殊性 总被引:4,自引:1,他引:3
1996年包头西6.4级地震是一次十分重要的地震,又是一个非常特殊的地震。集二十多年对强震前主要震兆特征和地震活动图像演化的认识,无论在6.4级地震前看到的,还是震后震例总结的,种种震兆异常基本集中在临河地区,而不是包头地区。 相似文献