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491.
492.
This study was conducted to compare lipid and fatty acid composition of cod, haddock and halibut. Three groups of cod (276 g ± 61 g), haddock (538 g ± 83 g) and halibut (3704 g ± 221 g) were maintained with commercial feeds mainly based on fish meal and marine fish oil for 12 weeks prior to sampling. The fatty acid compositions of muscle and liver were determined by GC/FID after derivatization of extracted lipids into fatty acid methyl esters (FAME). Lipids were also fractionated into neutral and polar lipids using Waters silica Sep-Pak?. The phospholipid fraction was further separated by high-performance thin-layer chromatography (HPTLC) and the FAME profile was obtained. Results of the present study showed that cod and haddock were lean fish and their total muscle lipid contents were 0.8% and 0.7%, respectively, with phospholipid constituting 83.6% and 87.5% of the total muscle lipid, respectively. Halibut was a medium-fat fish and its muscle lipid content was 8%, with 84% of the total muscle lipid being neutral lipid. Total liver lipid contents of cod, haddock and halibut were 36.9%, 67.2% and 30.7%, respectively, of which the neutral lipids accounted for the major fraction (88.1%–97.1%). Polyunsaturated fatty acids were the most abundant in cod and haddock muscle neutral lipid. Monounsaturated fatty acid level was the highest in halibut muscle neutral lipid. Fatty acid compositions of phospholipid were relatively constant. In summary, the liver of cod and haddock as lean fish was the main lipid reserve organ, and structural phospholipid is the major lipid form in flesh. However, as a medium-fat fish, halibut stored lipid in both their liver and muscle. 相似文献
493.
对常规探空资料进行加工处理,形成多个单站要素物理特征量,利用郑州辖区7个观测站1990~2000年实况资料,寻找各要素特征量与冰雹天气的关联,选取相关性好的因子,建立冰雹天气单站物理特征量预报方程。经历史回代,方程拟合率均在70%以上。 相似文献
494.
锦葵科(Malvaceae Juss.)翅子树属(Pterospermum Schreb.)主要分布于热带亚洲,该属化石目前只在印度有少量记录。本研究报道了产自云南省景谷县(23°31′N,100°42′E)下中新统三号沟组的翅子树属叶片化石。通过形态学研究鉴定出3个种:双兴翅子树(P.shuangxingii Y.S.Zhao, J.Huang et T. Su sp. nov.),叶片偏小型,顶端截形并具3浅裂,与现今分布于东南亚地区的大花翅子树(P.grandiflorum Craib)形态较为相似;云南翅子树近似种(P.cf.yunnanense H.H.Hsue),叶片偏小型,顶端不分裂;翅子树属一未定种(Pterospermum sp.),叶片中型,叶片顶端具齿。景谷县翅子树属化石的发现证明,早中新世该属就在我国西南地区分化并繁盛至今。综合本研究以及已有证据,翅子树属可能从印度次大陆起源,随后向亚洲东部和东南部的热带地区扩散,最终形成了现今热带亚洲的分布格局。此外,本研究还描述了翅子树属化石叶片上的9种昆虫取食类型,与该属现生种叶片的昆虫取食形态一致,表明该属现今的植食性昆虫取食行为可能在早中新世就已经出现。
相似文献495.
496.
ADCP在长江口悬沙输运观测中的应用 总被引:11,自引:1,他引:11
声学多普勒流速剖面仪 (ADCP)是近年来发展起来的一种用于测量流速的声学仪器 ,同时还可以通过建立回声强度和现场取得水样的回归关系式而获得悬沙浓度的数据。本文利用在长江口两个站位的高频观测数据 ,对现场取得的悬沙作粒度分析 ,在此基础上对枯季长江口地区悬沙输送机制和悬沙粒度对水动力的响应进行了分析和探讨。结果表明 :平均流输运在整个悬沙输送中占主导地位 ,同时潮扩散和垂向扩散作用也是引起两站悬沙输运的重要因子 ;不同层次和不同时刻的悬沙粒度参数的变化 ,既和海 陆转换有关 ,也和潮相变化密切相关。 相似文献
497.
498.
The behavior of a pile group is solved using the finite element method, and the fundamental solution of saturated multilayered soils with anisotropic permeability is obtained by the analytical layer element method. Based on the supposition of no slip occurring at the pile‐soil interface, the governing equations of the interaction between the pile group and the soils due to a point sink are established in the Laplace‐Hankel transformed domain by considering the pile‐soil compatibility condition. Numerical results are presented to study the effect of point sink pumping, the properties of soils, and the geometries of piles on the behavior of the pile group. 相似文献
499.
水平层状导电大地中层状含水层地面核磁共振响应的数值计算技术涉及到导电介质中回线源 磁场的计算以及地下含水层中质子磁矩在线圈中产生感应信号的体积积分. 文中采用直接数 值积分技术,对具有振荡核函数的Hankel变换进行积分,以求取回线源磁场的径向与垂向分 量,计算并研究了回线产生的径向与垂向磁场分量随空间位置的变化规律. 基于磁场空间分 布特点,利用不等间距空间剖分技术计算地面核磁共振的体积积分,模拟了不同模型的地面 核磁共振响应并讨论了其影响因素. 结果表明,结合能对任意层状导电介质中磁场进行稳定 快速计算的直接数值积分技术与不等距空间模型剖分技术,可正确模拟地面核磁共振响应. 导电性是产生地面核磁共振信号相位的先决条件,但影响响应振幅强度与相位的因素还有含 水层的埋深、厚度以及装置大小等. 相似文献
500.
Ai‐Cheng ZHANG Wei‐Biao HSU Christine FLOSS Xian‐Hua LI Qiu‐Li LI Yang LIU Lawrence A. TAYLOR 《Meteoritics & planetary science》2010,45(12):1929-1947
Abstract– Northwest Africa (NWA) 2977 is an olivine‐gabbro lunar meteorite that has a distinctly different petrographic texture from other lunar basalts. We studied this rock with a series of in situ analytical methods. NWA 2977 consists mainly of olivine and pyroxene with minor plagioclase. It shows evidence of intense shock metamorphism, locally as high as shock‐stage S6. Olivine adjacent to a melt vein has been partially transformed into ringwoodite and Al,Ti‐rich chromite grains have partially transformed into their high‐pressure polymorph (possibly CaTi2O4‐structure). Olivine in NWA 2977 contains two types of lithic inclusions. One type is present as Si,Al‐rich melt inclusions that are composed of glass and, in most cases, dendritic pyroxene. The other type is mafic and composed of relatively coarse‐grained augite with accessory chromite, RE‐merrillite, and baddeleyite. Two Si,Al‐rich melt inclusions are heavy rare earth elements (REE) enriched, whereas the mafic inclusion has high REE concentrations and a KREEP‐like pattern. The mafic inclusion could be a relict fragment captured during the ascent of the parent magma of NWA 2977, whereas the Si,Al‐rich inclusions may represent the original NWA 2977 melt. The calculated whole‐rock composition has a KREEP‐like REE pattern, suggesting that NWA 2977 has an affinity to KREEP rocks. Baddeleyite has recorded a young crystallization age of 3123 ± 7 Ma (2σ), which is consistent with results from previous whole‐rock and mineral Sm‐Nd and Rb‐Sr studies. The petrography, mineralogy, trace element geochemistry, and young crystallization age of NWA 2977 support the possibility of pairing between NWA 2977 and the olivine‐gabbro portion of NWA 773. 相似文献