全文获取类型
收费全文 | 7117篇 |
免费 | 380篇 |
国内免费 | 187篇 |
专业分类
化学 | 4323篇 |
晶体学 | 76篇 |
力学 | 298篇 |
综合类 | 25篇 |
数学 | 1049篇 |
物理学 | 1913篇 |
出版年
2023年 | 70篇 |
2022年 | 173篇 |
2021年 | 182篇 |
2020年 | 191篇 |
2019年 | 188篇 |
2018年 | 172篇 |
2017年 | 150篇 |
2016年 | 225篇 |
2015年 | 223篇 |
2014年 | 249篇 |
2013年 | 489篇 |
2012年 | 442篇 |
2011年 | 492篇 |
2010年 | 309篇 |
2009年 | 279篇 |
2008年 | 360篇 |
2007年 | 304篇 |
2006年 | 310篇 |
2005年 | 263篇 |
2004年 | 198篇 |
2003年 | 208篇 |
2002年 | 177篇 |
2001年 | 159篇 |
2000年 | 140篇 |
1999年 | 108篇 |
1998年 | 67篇 |
1997年 | 64篇 |
1996年 | 72篇 |
1995年 | 52篇 |
1994年 | 91篇 |
1993年 | 65篇 |
1992年 | 77篇 |
1991年 | 62篇 |
1990年 | 57篇 |
1989年 | 45篇 |
1988年 | 46篇 |
1987年 | 41篇 |
1986年 | 43篇 |
1985年 | 63篇 |
1984年 | 63篇 |
1983年 | 38篇 |
1982年 | 62篇 |
1981年 | 53篇 |
1980年 | 57篇 |
1979年 | 51篇 |
1978年 | 58篇 |
1977年 | 51篇 |
1976年 | 46篇 |
1975年 | 37篇 |
1973年 | 39篇 |
排序方式: 共有7684条查询结果,搜索用时 15 毫秒
991.
Franklin David Rincón Marcelo Esposito Pedro Henrique Hermes de Araújo Claudia Sayer Galo Antonio Carrillo Le Roux 《大分子反应工程》2013,7(1):24-35
Reaction calorimetry is a very useful tool to monitor exothermic polymerization reactions as it is based on the estimation of the heat generated by the reaction. The objective of this work is to analyze the performance of an unscented Kalman filter (UKF) for online monitoring of batch vinyl acetate emulsion polymerization reactions. Reactions are performed in isoperibolic and isothermal conditions. The UKF is compared to an extended Kalman filter that has a very poor performance. The results show that the UKF is able to provide good estimates for the conversion, for the reactor and jacket temperatures, for the overall heat transfer coefficient between the reaction medium and the jacket, and for the heat loss from the jacket to the surroundings.
992.
993.
Jorge A. León 《Applied Mathematics and Optimization》1993,27(3):313-327
Let (X,l,) be a measure space, letW be a cylindrical Hilbert-Wiener process, and let be an anticipating integrable process-valued function onX. We prove, under natural assumptions on, that there exists a measurable version Yx,x X, of the anticipating integral of(x) such that the integral x Yx(dx) is a version of the anticipating integral of X
(x)(dx). We apply this anticipating Fubini theorem to study solutions of a class of stochastic evolution equations in Hilbert space. 相似文献
994.
针对高瓦斯矿发火区封闭时常发生瓦斯爆炸事故,对影响瓦斯爆炸界限的因素进行实验,探索温度、压力、可燃气体(CO)、惰性气体(N2和CO2)等条件对瓦斯爆炸界限的影响规律。得出常温常压下瓦斯爆炸的体积分数下限为5%,瓦斯爆炸上限为13.5%,以及CO2的惰化效果比N2更好的结论。根据实验数据绘制混合气体的爆炸三角形,并进行新的惰化分区划分,不仅为火区封闭时防治瓦斯爆炸提供新的技术途径,而且能计算出使火区惰化时,所需惰性气体量,可对这些因素进行合理控制,有效地降低瓦斯爆炸危险性。 相似文献
995.
R.-D. Herzberg N. Amzal J.E. Bastin F. Becker P.M.T. Brew P.A. Butler A.J.C. Chewter J.F.C. Cocks O. Dorvaux K. Eskola J. Gerl P.T. Greenlees N.J. Hammond K. Hauschild K. Helariutta F. Heßberger M. Houry A. Hürstel R.D. Humphreys G.D. Jones P.M. Jones R. Julin S. Juutinen H. Kankaanpää H. Kettunen T.L. Khoo W. Korten P. Kuusiniemi Y. Le Coz M. Leino A.P. Leppänen C.J. Lister R. Lucas M. Muikku P. Nieminen R.D. Page T. Page P. Rahkila P. Reiter Ch. Schlegel C. Scholey G. Sletten O. Stezowski Ch. Theisen W.H. Trzaska J. Uusitalo H.J. Wollersheim 《The European Physical Journal A - Hadrons and Nuclei》2002,15(1-2):205-208
In-beam conversion electron spectroscopy experiments have been performed on the transfermium nuclei 253, 254No using the conversion electron spectrometer SACRED in nearly collinear geometry in conjunction with the gas-filled separator
RITU at the University of Jyv?skyl?. The experimental setup is discussed and the spectra are compared to Monte Carlo simulations.
The implications for the ground-state configuration of 253No are discussed.
Received: 21 March 2002 / Accepted: 16 May 2002 / Published online: 31 October 2002
RID="a"
ID="a"e-mail: rdh@ns.ph.liv.ac.uk
RID="b"
ID="b"Present address: GANIL, F-14021 Caen, France.
RID="c"
ID="c"Permanent address: IReS Strasbourg, IN2P3-CNRS, F-67037-Strasbourg, France.
RID="d"
ID="d"Present address: CEA/DIF DCRE/SDE/LDN F-91680 Bruyeres-le-Chatel.
RID="e"
ID="e"Present address: Daresbury Laboratory, Daresbury WA4 4AD, UK.
RID="f"
ID="f"Permanent address: IPN Lyon, IN2P3-CNRS, F-69037 Lyon, France. 相似文献
996.
997.
Ge HM Yan W Guo ZK Luo Q Feng R Zang le Y Shen Y Jiao RH Xu Q Tan RX 《Chemical communications (Cambridge, England)》2011,47(8):2321-2323
Precursor-fed cultivation of endophytic Chaetomium globosum 1C51 afforded nine novel "unnatural" halogenated chaetoglobosins including those with more preferable immunosuppressive activity. 相似文献
998.
Management of domestic wastes often relies on incineration, a process that eliminates large amount of wastes but also produces toxic residues that concentrate heavy metals. Those hazardous secondary wastes require specific treatment. Vitrification is seen as a powerful way to stabilise them. However, concern exists about the long term behaviour of these glass wastes and the potential release of toxic species into the environment. The answers will come with further investigation into the physico-chemical evolution of the vitrified wastes and the mobility of hazardous elements within the matrix with appropriate analytical methods. Laser ablation coupled with inductively coupled mass spectrometry (LA-ICP-MS) is a challenging technique for the chemical analysis of trace elements in solid materials. This paper presents an evaluation of the potential of LA- ICP-MS for macro and microanalysis of trace metals in domestic vitrified wastes with regards to other physical analytical techniques of solids such as scanning electronprobe X-ray energy dispersive spectroscopy (SEM-EDXS). Two typical samples, vitreous and crystallised, are used to compare the analytical performances of the two techniques. SEM-EDXS was used for mineralogical characterisation and chemical analysis of the mineralogical phases. Relative micro-analysis and bulk quantitative analysis of 30 major, minor and trace elements was performed by LA-ICP-MS: precision was between 10 and 20% for most elements and quantitative analysis proved possible with an accuracy of 20% and relative detection limits of 0.1 mg kg(-1). 相似文献
999.
以三苯胺和苯并噻唑盐为原料,设计合成了一种具有红光发射特性的D-π-A型荧光粘度探针N-乙酸乙酯基-2-(4-甲酸甲酯基三苯胺-4'-乙烯基)苯并噻唑六氟磷酸盐(L),运用现代分析测试手段进行了系统地表征。 研究结果表明,探针L的最大发射波长为630 nm,能有效地降低生物背景,提高生物成像的信噪比。 该探针对粘度有很好的荧光响应,其荧光强度比值(I/I0)的对数与粘度的对数呈现很好的线性关系(R2=0.9934)。 此外,探针L对极性的敏感性小,且荧光信号不受生物分子的干扰。 生物学研究结果表明,探针L具有低的细胞毒性,可应用于细胞内微环境粘度的荧光成像。 相似文献
1000.