全文获取类型
收费全文 | 81942篇 |
免费 | 455篇 |
国内免费 | 390篇 |
专业分类
化学 | 26719篇 |
晶体学 | 800篇 |
力学 | 6921篇 |
数学 | 32626篇 |
物理学 | 15721篇 |
出版年
2023年 | 50篇 |
2022年 | 138篇 |
2021年 | 132篇 |
2020年 | 109篇 |
2019年 | 98篇 |
2018年 | 10469篇 |
2017年 | 10307篇 |
2016年 | 6223篇 |
2015年 | 971篇 |
2014年 | 417篇 |
2013年 | 538篇 |
2012年 | 4003篇 |
2011年 | 10733篇 |
2010年 | 5771篇 |
2009年 | 6156篇 |
2008年 | 6828篇 |
2007年 | 8974篇 |
2006年 | 419篇 |
2005年 | 1515篇 |
2004年 | 1667篇 |
2003年 | 2106篇 |
2002年 | 1108篇 |
2001年 | 288篇 |
2000年 | 331篇 |
1999年 | 193篇 |
1998年 | 220篇 |
1997年 | 173篇 |
1996年 | 246篇 |
1995年 | 158篇 |
1994年 | 111篇 |
1993年 | 126篇 |
1992年 | 79篇 |
1991年 | 89篇 |
1990年 | 77篇 |
1989年 | 87篇 |
1988年 | 87篇 |
1987年 | 96篇 |
1986年 | 80篇 |
1985年 | 85篇 |
1984年 | 80篇 |
1983年 | 55篇 |
1982年 | 62篇 |
1981年 | 64篇 |
1980年 | 73篇 |
1979年 | 63篇 |
1978年 | 51篇 |
1977年 | 46篇 |
1914年 | 45篇 |
1913年 | 43篇 |
1909年 | 42篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
992.
993.
In this paper, a novel multidimensional scaling (MDS) based on information measures method is proposed to analyze financial stock markets. In order to examine the effectiveness of this method, we applied it to the classification of two types of artificial series, the logistic map model and the cubic map model, as well as stock time series. Moreover, the traditional MDS using Euclidean dissimilarity is also provided as a reference for comparisons. The results show that the MDS based on information measures can give us more detailed, exact and clearer information on the classification of simulation series and stock time series than the MDS using Euclidean dissimilarity. In addition, the proposed graphical method may also assist in the construction of multivariate econometric models. 相似文献
994.
995.
996.
997.
998.
Fuzzy identification of cutting acoustic emission with extended subtractive cluster analysis 总被引:1,自引:0,他引:1
This paper presents fuzzy acoustic emission identification in high precision hard turning process based on extended subtractive
cluster analysis combined with the least-square estimation method. The fuzzy identification method provides a simple way to
arrive at a definite conclusion based upon the information obtained with the difficulty in understanding the exact physics
of the machining process. The experimental results prove that the proposed method is efficient and feasible. 相似文献
999.
Petr Kluson Stepan Kment Magdalena Morozova Pavel Dytrych Stanislav Hejda Morwenna Slater Zdenek Hubicka Josef Krysa 《Chemical Papers》2012,66(5):446-460
Chemistry and physics of thin semiconducting layers of various types are subjects of intense research. Especially when nanotechnology
methods such as self-assembly are involved, amazing structural and/or functional properties may appear. Also modern physical
methods using variously organized plasma arrangements are able to produce uniform structures with distinctive functionality.
In this review, based virtually on our own work, discussions on the preparation, structure, morphology, and function of titanium(IV)
oxide nanoscopic thin films are presented. It was shown that structurally and functionally similar titanium(IV) oxide films
can be prepared via completely different preparation techniques. Function tests were arranged as “primary”, covering the assessment
of the light induced charge separation efficiency, and “secondary”, based on photocatalytic surface oxidations. 相似文献
1000.
A short-term aerobic stabilization of digested waste in the final methane phase was studied. The effect of aeration rate on
the reduction of leachate parameters and on the rate of CO2 production and O2 assimilation was investigated. Experimental simulation of aerobic landfill stabilization was carried out using lysimeters.
When testing the effect of aeration rate on the reduction of leachate indices (BOD5, COD, N-NH4+), it was reported that the most significant reduction was obtained at the highest rate of aeration and the smallest reduction
of leachate indices was attained not at the lowest but at medium aeration rates. Both the rate of CO2 production and the O2 assimilation reached their highest values in the lysimeters aerated at a high rate of aeration. The proposed mathematical
model which consists of a system of five differential equations describing CO2 production, O2 assimilation and the changes of organic carbon content in the leachate correspond well with the experimental data. 相似文献