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441.
442.
Helen M. Johnston Robert Fender Kinwah Wu 《Monthly notices of the Royal Astronomical Society》1999,308(2):415-423
We present new optical and infrared (IR) observations of Cir X-1 taken near apastron. Both sets of spectra show asymmetric emission lines. Archival optical observations show that an asymmetric H α emission line has been in evidence for the past 20 years, although the shape of the line has changed significantly. We present an eccentric ( e ∼0.7–0.9) low-mass binary model, where the system consists of a neutron star orbiting around a (sub)giant companion star of 3–5 M⊙ . We suggest that the broad components of the emission lines arise in a high-velocity, optically thick flow near the neutron star, while the narrow components of the optical and the IR lines arise near the companion star and a heated ejecta shell surrounding the binary respectively. In this model, the velocity of the narrow component reflects the space velocity of the binary; the implied radial velocity (+430 km s−1 after correcting for Galactic rotation) is the highest velocity known for an X-ray binary. 相似文献
443.
江汉平原沔城M1孔的沉积特征与古环境重建 总被引:6,自引:0,他引:6
通过对江汉平原沔城M1孔湖泊沉积物进行沉积特征、粒度、14C年代、孢粉分析,重建了晚冰期以来该地区古环境、古气候演化的过程和序列:晚冰期后期有一扩张期,气候温湿并出现湖泊相沉积;晚冰期末期气候温凉偏干、河流环境;全新世初期(10-8.9kaBP),气候转向温湿;全新世大暖期(8.9-3.5kaBP),总体上气候温暖湿润,其中6.8-4.9kaBP是最宜期,4.9-4.8kaBP和4.4-4.2kaBP为两次降温事件,4.8kaBP积水湖盆开始形成,3.9-3.5kaBP为云梦泽鼎盛期;全新世晚期(3.5-1.7kaBP),气温较大暖期有所下降,其中3.5-2.5kaBP温凉偏湿,2.5-1.7kaBP较为温湿,湖泊较为稳定,1.7kaBP开始,云梦泽萎缩,钻孔所在位置出露水面。 相似文献
444.
445.
446.
广州气温与厄尔尼诺的多尺度相互联系 总被引:3,自引:0,他引:3
通过对广州气温距平和Nino 3、Nino 1+2区SSTA序列做小波变换,研究了广州气温变化与ENSO振荡过程之间的多尺度联系,发现它们都存在着强的十年际振荡。年际尺度的振荡为正相关,十年际风度为负相关。由于SSTA的十年际变率是由强厄尔尼诺事件的韵律产生的,因此;广州气温对强烈厄尔尼诺的响应性质上不同于对普通厄尔尼诺的响应. 相似文献
447.
处理了聊古一井1981 ~1984 年氦的观测资料,发现在两次较近的地震(1981 年宁晋MS5 .8 和1983 年菏泽MS5 .9) 前,氦都有明显的形态相似的异常变化. 相似文献
448.
Muscovite-2M1 shows a major phase transition at about 800°C, which is generally attributed in the literature to the structural dehydroxylation
process, although a number of structural models have been proposed for the dehydroxylated phase, and different transformation
mechanisms have also been put forward. The observed first order transformation involves an increase in the cell volume, and
it is not clear to date how the cell expansion is related to the loss of hydroxyl groups. The phase change has been re-investigated
here by in situ high temperature powder diffraction, both in non-isothermal and isothermal modes, to combine for the first
time the structural and the kinetic interpretation of the transformation. The results unequivocally confirm that the reaction
taking place in the temperature range 700–1000°C is truly a dehydroxylation process, involving the nucleation and growth of
the high temperature dehydroxylated phase, having Al in 5-fold coordination. Structural simulations of the basal peaks of
the powder diffraction patterns indicate that the model originally proposed by Udagawa et al. (1974) for the dehydroxylated
phase correctly describes the high temperature phase. The kinetic analysis of the isothermal data using an Avrami-type model
yields values for the reaction order compatible with a reaction mechanism limited by a monodimensional diffusion step. Apparent
activation energy of the process in vacuum is about 251 kJ/mol. Experiments carried out at temperatures much higher than the
onset temperature of the reaction show that the dehydroxylation reaction overlaps with the reaction of formation of mullite,
the final product in the reaction pathway.
Received: 24 April 1998 / Revised, accepted: 12 October 1998 相似文献
449.
酪蛋白激酶1 (CK1)是一种重要的蛋白激酶家族,其在DNA损伤应答和修复、细胞增殖和凋亡、胚胎发育和稳态等重要的生物学过程中都具有复杂多样的调控作用。为了理解CK1基因家族在双壳贝类中的特征、进化及生物学功能,实验采用比较基因组学及生物信息学的方法对双壳贝类CK1基因家族进行了鉴定分析,通过虾夷扇贝高温应激实验,研究了CK1基因家族在高温应激时的表达规律。结果显示,在虾夷扇贝、栉孔扇贝、长牡蛎与侏儒蛤中均存在CK1α,CK1αlike,CK1δ,CK1γ3,并发现CK1ε,CK1γ1,CK1γ2在双壳贝类中发生了丢失。时空表达分析发现,双壳贝类CK1基因均在胚胎发育早期集中表达,并以多细胞/囊胚期为界呈现出母源/合子特异性表达模式。CK1为关键基因的基因共表达模块显著富集在错配修复、核苷酸剪切修复等相关通路上,暗示了CK1基因在双壳贝类胚胎发育过程中参与调控DNA损伤修复过程,从而维持早期胚胎发育时的基因组稳定性。双壳贝类CK1基因在成体中呈现组织特异的表达模式,主要在鳃和雄性性腺中具有相对较高的表达量。虾夷扇贝受到高温应激后,其鳃中PyCK1α, PyCK1αlike和PyCK1δ... 相似文献
450.
《Limnologica》2017
Atmospheric exchanges largely dominate the heat budget of deep lakes in temperate regions. Heat import and export by through-flows is of much lower entity and has been neglected or simplified in many numerical thermodynamic models of lakes. This is often due either to the unavailability of data for inflows and outflows, or to the difficulties in forecasting the evolution of their discharge and temperature in climate change studies. While disregarding through-flows may seem correct, riverine intrusions can bring warmer water than the deep hypolimnetic one to the lower metalimnion and upper hypolimnion, where sunlight does not penetrate and mixing is poor. For holomictic lakes with significant inflow contributions, this can affect the thermal structure at intermediate depths, hampering any numerical model which neglects through-flows. This study focuses on a relevant basin under such aspect, Lake Maggiore (Northern Italy/Southern Switzerland), which drains the rainiest watershed of the Southern Alps. First, we quantify to what extent a one-dimensional fixed-level model ignoring through-flows is able to predict the observed evolution of the thermal structure of the lake and the improvements resulting from reproducing the main inflows and outflows. Then, we directly discuss the influence of through-flows on the thermodynamic structure of Lake Maggiore. The General Lake Model (GLM) was here adopted, reproducing the 1998–2014 period, spanning years with different meteorological and hydrological features. Results show that a calibrated enclosed-lake model can give satisfactory results only if it employs an unrealistically low light extinction coefficient to allow heating of the deep metalimnion and hypolimnion, whose real warming strongly depends on interflows. 相似文献