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971.
大珠母贝人工苗工厂化分组标粗;室内养殖54d,贝苗平均壳高从入池时6.61mm增长至13.08mm,最大为14.25mm,平均成活率31.9%,最高达49.8%。试验结果初步表明:1.大珠母贝岸上室内工厂化养殖不但可行,而且也将是解决当前海上养成困境的一条出路;2.发现自然海区中也存在饥饿死亡现象及死亡潜伏期,反映出海上养殖高死亡率的复杂性;3.人工配合饲料的应用显著提高了贝苗的增长率和成活率,显示出广阔的商业价值。 相似文献
972.
辽东早元古宙拗拉槽中的铅锌矿床,可划分为层状矿床和脉状矿床两大类。本文论述了后一种类型的典型代表——东胜式铅锌矿床的控矿因素和矿床特征。依据大量地质事实,作者认为:东胜式铅锌矿床的控矿构造是与基底花岗岩活动密切相关的中生代半地堑系;矿质来源于地壳深部液态矿源层;中生代岩浆活动是矿液上升的热动力。综合这三大因素,建立了东胜式矿床的成矿模式。由此,期望对进一步找矿能有一定的指导意义。 相似文献
973.
974.
作者通过对红花沟金矿各主要岩石类型及金矿石稀土元素丰度的分析测定,探讨了本区的稀土地球化学特征。研究表明:太古代变质岩、元古代花岗岩、中生代花岗岩及花岗斑岩、流纹岩和凝灰岩、第三纪玄武岩及金矿石的稀土配分曲线均为右倾斜型,即富轻稀土,都有十分相似的 Ce 负异常。变质岩、元古代花岗岩和玄武岩显示Eu 正异常,其它岩石和矿石显示 Eu 负异常。牛营子岩体显示较强的 Eu 负异常,且稀土总量明显高于元古代花岗岩。元古代的花岗岩源岩可能为石榴石角闪岩。金矿与斜长角闪岩关系最为密切,斜长角闪岩可能是形成金矿的矿源层。 相似文献
975.
976.
In this work, we shall confine ourselves to solve analytically the integrals called
,
for the two components of albedo radiation pressure on an Earth’s satellite. When the Earth’s albedo is variable, as far as
we know, this case has not been dealt with analytically. We shall solve these two integrals when the satellite’ horizon is
illuminated and when the sun lies on the equator. This approach will facilitate the evaluation of the mentioned two equations.
We will also compare our results with previous works obtained numerically. 相似文献
977.
978.
Jose-Manuel Ferrándiz Maria-Eugenia Sansaturio Joseph R. Pojman 《Celestial Mechanics and Dynamical Astronomy》1992,53(4):347-363
The set of canonical redundant variables previously introduced by the first author is derived from Cartesian coordinates in a simplified form which allows the reduction of the Kepler problem to four harmonic oscillators with unit frequency. The coordinates are defined to be the direction cosines of the position of the particle along with the inverse of its distance. True anomaly is the new independent variable. The behavior of this new transformation is studied when applied to the numerical integrations of the main problem in satellite theory. In particular, computation time and accuracy of orbits in the new variables are compared with those in K-S and Cartesian variables. It is noteworthy that for high eccentricities the new variables require the least computation time for comparable accuracy, regardless of the integration scheme. 相似文献
979.
V. Kudielka 《Celestial Mechanics and Dynamical Astronomy》1994,60(4):455-470
An analytic model for third-body perturbations and for the second zonal harmonic of the central body's gravitational field is presented. A simplified version of this model applied to the Earth-Moon-Sun system indicates the existence of high-altitude and highly-inclined orbits with their apsides in the equator plane, for which the apsidal as well as the nodal motion ceases. For special positions of the node, secular changes of eccentricity and inclination disappear too (balanced orbits). For an ascending node at vernal equinox, the inclination of balanced orbits is 94.56°, for a node at autumnal equinox 85.44°, independent of the eccentricity of the orbit. For a node perpendicular to the equinox, there exist circular balanced orbits at 90° inclination. By slightly adjusting the initial inclination as suggested by the simplified model, orbits can be found — calculated by the full model or by different methods — that show only minor variations in eccentricity, inclination, argument of perigee, and longitude of the ascending node for 105 revolutions and more. Orbits near the unstable equilibria at 94.56° and 85.44° inclination show very long periodic librations and oscillations between retrogade and prograde motion.Retired from IBM Vienna Software Development Laboratory. 相似文献
980.
H. J. Walker 《Astrophysics and Space Science》1994,217(1-2):139-140
The IRAS Low Resolution Spectrometer (LRS) covered the spectral region from 7µm to 23µm, and an Atlas was produced containing 5425 spectra. Most of the spectra were associated with evolved stars, including over 3000 spectra from the dust shells around O-rich stars. When Artificial Intelligence techniques were applied to the dataset, a new classification was derived. A scheme with 77 classes, grouped into 9 metaclasses, resulted, and for those types of spectra which were well represented in the initial dataset (i.e. the evolved stars) a very subtle classification was derived, often using line shapes, relative line strengths, or the presence of additional weak features. 相似文献