全文获取类型
收费全文 | 62756篇 |
免费 | 5678篇 |
国内免费 | 4024篇 |
专业分类
化学 | 7827篇 |
晶体学 | 100篇 |
力学 | 4962篇 |
综合类 | 492篇 |
数学 | 10645篇 |
物理学 | 12401篇 |
综合类 | 36031篇 |
出版年
2024年 | 263篇 |
2023年 | 789篇 |
2022年 | 1474篇 |
2021年 | 1626篇 |
2020年 | 1738篇 |
2019年 | 1480篇 |
2018年 | 1446篇 |
2017年 | 1829篇 |
2016年 | 2142篇 |
2015年 | 2126篇 |
2014年 | 3281篇 |
2013年 | 3736篇 |
2012年 | 3733篇 |
2011年 | 4032篇 |
2010年 | 3148篇 |
2009年 | 3727篇 |
2008年 | 3399篇 |
2007年 | 4134篇 |
2006年 | 3599篇 |
2005年 | 3252篇 |
2004年 | 2884篇 |
2003年 | 2519篇 |
2002年 | 2266篇 |
2001年 | 1822篇 |
2000年 | 1706篇 |
1999年 | 1516篇 |
1998年 | 1237篇 |
1997年 | 1087篇 |
1996年 | 926篇 |
1995年 | 819篇 |
1994年 | 744篇 |
1993年 | 644篇 |
1992年 | 574篇 |
1991年 | 495篇 |
1990年 | 472篇 |
1989年 | 331篇 |
1988年 | 313篇 |
1987年 | 249篇 |
1986年 | 168篇 |
1985年 | 150篇 |
1984年 | 134篇 |
1983年 | 72篇 |
1982年 | 97篇 |
1981年 | 61篇 |
1980年 | 29篇 |
1979年 | 37篇 |
1978年 | 29篇 |
1977年 | 28篇 |
1976年 | 15篇 |
1973年 | 22篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
It is proved that the variety of relevant disjunction lattices has the finite embeddability property. It follows that Avron's relevance logic RMI min has a strong form of the finite model property, so it has a solvable deducibility problem. This strengthens Avron's result that RMI min is decidable. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
32.
33.
中国证券市场股指波动的条件异方差特性分析 总被引:6,自引:0,他引:6
股指的波动具有持续性、集聚性 ,如何进行判别 ?本文用 Garch模型理论探讨沪深股指的这种条件异方差特征 ,进一步分析波动是否影响股指未来变化 ,以及股市对利好、利空的消息是否存在不对称的反映。同时 ,比较不同类型的股指的共性及差异 ,并对上述现象作了解释和说明。 相似文献
34.
沈有根 《中国科学A辑(英文版)》2002,45(3):400-408
Using the membrane model which is based on brick wall model, we calculated the free energy and entropy of Garfinkle-Horne dilatonic black hole due to arbitrary spin fields. The result shows that the entropy of scalar field and the entropy of Fermionic field have similar formulas. There is only a coefficient between them. 相似文献
35.
Cosmic dust and our origins 总被引:1,自引:0,他引:1
J Mayo Greenberg 《Surface science》2002,500(1-3):793-822
The small solid particles in the space between the stars provide the surfaces for the production of many simple and complex molecules. Processes involving the effects of ultraviolet irradiation of the thin (hundredth micron) mantles are shown to produce a wide range of molecules and ions also seen in comets. Some of the more complex ones inferred from laboratory experiments are expected to play an important role in the origin of life. An outline of the chemical evolution of interstellar dust as observed and as studied in the laboratory is presented. Observations of comets are shown to provide substantial evidence for their being fluffy aggregates of interstellar dust as it was in the protosolar nebula, i.e. the interstellar cloud which collapsed to form the solar system. The theory that comets may have brought the progenitors of life to the earth is summarized. 相似文献
36.
37.
38.
基于GM(1,1)模型的某高校招生人数预测 总被引:1,自引:0,他引:1
分析了近年来我国高校招生人数的变化趋势,并利用GM(1,1)模型对某高校2008年的招生人数进行了预测.从而为高校招生人数决策提供了依据。 相似文献
39.
周跃进 《安徽理工大学学报(自然科学版)》2008,28(4)
对多个处理且试验结果为多档次的临床试验,构建了其概率罐子模型。研究了模型中每个处理试验结果发生的概率。利用极大似然估计方法得到其估计量,并获得此估计量具有渐近正态性。 相似文献
40.
The usual tool for modelling bond ratings migration is a discrete, time‐homogeneous Markov chain. Such model assumes that all bonds are homogeneous with respect to their movement behaviour among rating categories and that the movement behaviour does not change over time. However, among recognized sources of heterogeneity in ratings migration is age of a bond (time elapsed since issuance). It has been observed that young bonds have a lower propensity to change ratings, and thus to default, than more seasoned bonds. The aim of this paper is to introduce a continuous, time‐non‐homogeneous model for bond ratings migration, which also incorporates a simple form of population heterogeneity. The specific form of heterogeneity postulated by the proposed model appears to be suitable for modelling the effect of age of a bond on its propensity to change ratings. This model, called a mover–stayer model, is an extension of a Markov chain. This paper derives the maximum likelihood estimators for the parameters of a continuous time mover–stayer model based on a sample of independent continuously monitored histories of the process, and develops the likelihood ratio statistic for discriminating between the Markov chain and the mover–stayer model. The methods are illustrated using a sample of rating histories of young corporate issuers. For these issuers the default probabilities predicted by the Markov chain and mover–stayer models are different. In particular for 1–4 years old bonds the mover–stayer model estimates substantially lower default probabilities from rating C than a Markov chain. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献