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131.
《Journal of Natural History》2012,46(27):2483-2514
A faunistic survey of the deep‐sea hyperbenthic copepods in the Sulu Sea, which has a deep basin and is connected via shallow straits with the Pacific and the South China Sea, was carried out in November and December 2002, using beam trawls and a mid‐water trawl. Two new genera and four new species of the primitive calanoid family Arietellidae are described. A new genus Metacalanalis shows intermediate characteristics between those of Metacalanus Cleve, 1901 and Pilarella Alvarez, . Another new genus, Protoparamisophria, is closely related to Paramisophria Scott, 1897, but exhibits more plesiomorphic states in the female genital system and appendages. Two new species of the genera Paraugaptiloides Ohtsuka, Boxshall and Roe, and Sarsarietellus Campaner, 1984 are the second and the third species, respectively, for these genera. This discovery enhances the validity of these rare genera, and sheds light on the geological history of the Sulu Sea and the evolution of the Arietellidae within it. 相似文献
132.
《Journal of Natural History》2012,46(39-40):2585-2591
In the present study, the cloning and sequence analysis of interleukin‐6 (IL‐6) from the giant panda (Ailuropoda melanoleuca) were described. Sequencing revealed that IL‐6 complementary DNA contains a 636 base‐pair open reading frame encoding 211 amino acids. Homology analyses indicated that the identity levels of nucleotide and deduced amino acid sequences of IL‐6 between the giant panda and other species in Carnivora ranged from 90.5% to 85.6% and from 82.9% to 76.5%, respectively. Phylogenetic analyses based on nucleotide and amino acid sequences showed that the harbour seal shared a closer relationship with the giant panda than other carnivores (ursids not included). The functionally important domains and sites that have previously been recognized in other carnivores were all observed in the IL‐6 sequence of the giant panda. These findings suggest that the complementary DNA fragment cloned is indeed the IL‐6 molecule with biological activity and can be used in immunological studies of the giant panda. 相似文献
133.
《Journal of Natural History》2012,46(17):1367-1380
The parasitic wasp Trogus pennator (Ichneumonidae) attacks the larvae of swallowtail butterflies (Papilionidae). Female T. pennator were followed in the field as they searched for larvae of the zebra swallowtail butterfly, Eurytides marcellus (Papilionidae), feeding on Asimina (Annonaceae) in central Florida, USA. Predictions of host‐finding theory and interactions with the host were thus investigated in a natural setting. Wasps seldom flew to plants other than Asimina and apparently recognized the plants by visual cues. Plants were attractive regardless of host presence, as the wasps approached plants lacking E. marcellus feeding damage twice as often as they approached damaged plants. However, wasps approached damaged plants at a rate greater than their frequency in the Asimina population, indicating that they can detect host damage before they approach the plants. After approaching within 0.5?m of plants, wasps tended not to land on plants lacking feeding damage. A comparison of the plants they landed on, however, showed no consistent preferences for damaged plants. The weaker trends in the latter data indicate that the presence of feeding damage was not the sole criterion for landing, although it evidently influenced behaviour. After landing, wasps spent more time searching damaged plants than undamaged plants. Butterflies preferred to oviposit on plants shorter than those searched by T. pennator. Possible adaptive consequences of this phenomenon are discussed. 相似文献
134.
在整个定点着舰过程中,飞机着舰下滑阶段的操纵难度和危险系数都是最高的,如何解决光学导引仿真中模型的准确度和视景特效的逼真度。是定点着舰仿真应用的重中之重。为了解决上述问题,根据光学导引秉统成像原理以及飞机、舰之间的几何关系,实时计算光学下滑道,建立了仿真平台的数学模型,并给出了状态方程。在基于VP平台的视景系统中,采用“立体光面”和动态缩放光晕的方法建立菲涅尔助降灯阵和迎角指示器的模型,保证了模拟着舰过程中飞行员视觉的逼真度。以美F-16飞机模型,进行了多次计算机仿真着舰,试验数据表明:在理想条件下光学导引仿真平台模型正确可信,飞行员着舰质量明显提高,能够起到导引着舰的作用。 相似文献
135.
Accurate modelling of volatility (or risk) is important in finance, particularly as it relates to the modelling and forecasting of value‐at‐risk (VaR) thresholds. As financial applications typically deal with a portfolio of assets and risk, there are several multivariate GARCH models which specify the risk of one asset as depending on its own past as well as the past behaviour of other assets. Multivariate effects, whereby the risk of a given asset depends on the previous risk of any other asset, are termed spillover effects. In this paper we analyse the importance of considering spillover effects when forecasting financial volatility. The forecasting performance of the VARMA‐GARCH model of Ling and McAleer (2003), which includes spillover effects from all assets, the CCC model of Bollerslev (1990), which includes no spillovers, and a new Portfolio Spillover GARCH (PS‐GARCH) model, which accommodates aggregate spillovers parsimoniously and hence avoids the so‐called curse of dimensionality, are compared using a VaR example for a portfolio containing four international stock market indices. The empirical results suggest that spillover effects are statistically significant. However, the VaR threshold forecasts are generally found to be insensitive to the inclusion of spillover effects in any of the multivariate models considered. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
136.
对于正整数n和k,设F(n,k)是闭区间[nk,(n 1)k]内所有正整数的集合,又设a1,a2,…,ak 1.是F(n,k)中适合a1<a2<…<ak 1的k 1个数.证明了:当且仅当ai=nk-i 1(n 1)i-1(i=1,2,…,k 1)时,a1,a2,…,ak 1构成几何数列. 相似文献
137.
戴惠良 《东华大学学报(自然科学版)》2000,26(2)
自准水平激光仪是利用激光作为准直光,广泛应用于地面平整、地面处理和渠道挖掘等方面。自准水平激光仪的激光信号与闭环控制系统的结合,实现地面的水平平整,它是自准水平激光仪的一种动态应用。 相似文献
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140.
针对关闭/废弃矿井分类利用和等级评价,使用Adaboost迭代算法,建立了一个关闭/废弃矿井利用的可能性等级模型,总结得出关闭/废弃矿井分类利用可分为:关闭/废弃矿井生态文明开发,关闭/废弃矿井地下空间开发利用,关闭/废弃矿井遗留媒体资源开发利用,关闭/废弃矿井地下水资源开发利用,关闭/废弃矿井气油水光互补能源开发利用。确立了20项分类指标进行关闭/废弃矿井等级评价,初步构建出国内关闭/废弃矿井资源数据库,提出关闭/废弃矿井智能精准开发科学构想,构建了关闭/废弃矿井绿色资源评价技术体系,推动关闭/废弃矿井精准智能开采以及城市转型发展。 相似文献