全文获取类型
收费全文 | 11549篇 |
免费 | 1776篇 |
国内免费 | 2897篇 |
专业分类
化学 | 4130篇 |
晶体学 | 34篇 |
力学 | 1335篇 |
综合类 | 43篇 |
数学 | 2357篇 |
物理学 | 4737篇 |
综合类 | 3586篇 |
出版年
2023年 | 171篇 |
2022年 | 199篇 |
2021年 | 178篇 |
2020年 | 159篇 |
2019年 | 135篇 |
2018年 | 222篇 |
2017年 | 142篇 |
2016年 | 242篇 |
2015年 | 276篇 |
2014年 | 489篇 |
2013年 | 377篇 |
2012年 | 497篇 |
2011年 | 467篇 |
2010年 | 455篇 |
2009年 | 353篇 |
2008年 | 305篇 |
2007年 | 652篇 |
2006年 | 595篇 |
2005年 | 895篇 |
2004年 | 736篇 |
2003年 | 657篇 |
2002年 | 516篇 |
2001年 | 642篇 |
2000年 | 536篇 |
1999年 | 598篇 |
1998年 | 262篇 |
1997年 | 164篇 |
1996年 | 206篇 |
1995年 | 266篇 |
1994年 | 224篇 |
1993年 | 260篇 |
1992年 | 255篇 |
1991年 | 196篇 |
1990年 | 233篇 |
1989年 | 252篇 |
1988年 | 282篇 |
1987年 | 275篇 |
1986年 | 255篇 |
1985年 | 320篇 |
1984年 | 234篇 |
1983年 | 163篇 |
1982年 | 158篇 |
1981年 | 111篇 |
1975年 | 114篇 |
1959年 | 104篇 |
1958年 | 153篇 |
1957年 | 159篇 |
1956年 | 117篇 |
1955年 | 125篇 |
1954年 | 91篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
用闪光蒸镀法在77K制备了NdxFe1-x(x=0.06-0.80)非晶薄膜,原位测定了其电阻随温度的变化。结果表明:在0.192和ρ(T)∝T。晶化不是在一个固定的温度,而是在一个温度区间发生。 相似文献
52.
本文以开封大学16年来的发展历史说明,抓了基础道德教育是生命面提高办学质量的一个重要生长点,其具体做法包括:1.认真充实《德育大纲》、《校园文化大纲》、社会实践大纲》使其更国符合实际,目的更明确;2.在基础道德教育中要体现出教师的人格车量;3.建立基础道德教育体系并付诸实践;4.抓好观念向行为转化的训练;5.以章治校,增强纪委约束力,向制度和管理要水平,要质量,要素质。 相似文献
53.
In the present study, proteins and glycoproteins of mouse embryos at 2-cell,morula and blastocyst stages were analyzed.The techniques of ~(35)S-Met incorporation,ConA antiserum-precipitating ConA-binding proteins, mini-2D-electrophoresis, fluorography,video densitometer scanning and the computer-lmage system were used for analyses.Results of the investigations indicated that proteins and glycoproteins were synthesized by the embryos in a gradual increase manner from 2-cell to blastocyst. A relatively large amount of glycoproteins was synthesized during the morula and blastocyst stages.Two specific small glycoproteins respectively with molecular weights about 6500 and 9000 and PIs at 5.0 and 6.5 were apparently synthesized in the blastocyst but not in the 2-cell or the morula. 相似文献
54.
I.IntroductionThepcrformanccsofAcousto-optic(AO)dcviccareoftenlimitcdbythepropertiesofAOmcdiawhenitisusedinAOsigna1processingsystems.Thespectrumanalyzersandcorre1ationreceivers,forinstancc,areexpcctcdtoimprovcthereso1utionanddynamicrangcwhilereducingtheproccssorvolume.Rccent1y,ancwclassofmateria1s,themercurousha1ides,promiscstocontributeimportantsolutionstosuchnccdsandisrefincdtopractica1uti1izations.Themecurousha1ideweconsidcrinthispapcrismecurouschloride(Hg,C1,).Thesing1ecrystalofHg,Cl… 相似文献
55.
The electrochemical oxidation of 1, 3-benzenedithiol was investigated in a 0. 100 mol/L tetrabutylammonium perchlorate/acetonitrile electrolyte. The electrochemical techniques used were potential sweep, bulk electrolysis, rotating disc and the potential step method. The combination of the techniques yielded the number of electrons transferred per molecule, the reaction order, the transfer coefficient, the diffusion coefficient and concentration of dithiol anions, the standard heterogeneous rate constant as well as the formal potential and equilibrium constant of the preceeding dissociation reaction. This paper also illustrates the methods for studying the electrode kinetics of reactions which (a) involve a chemical reaction preceeding the electron-transfer process, (b) have insoluble polymer products, and (c) are totally irreversible. 相似文献
56.
LI Zi-jian LIU Ning LIU Zhi-qiang LIU Shu-ying HAN Qi-de ZHANG You-yi . Institute of Vascular Medicine Peking University Third Hospital Key Laboratory of Molecular Cardiovascular Sciences Ministry of Education Beijing P. R. China . Changchun Institute of Applied Chemistry Chinese Academy of Sciences Changchun P. R. China 《高等学校化学研究》2006,22(3):319-323
Introduction Adrenoceptors(ARs),membersofthesuperfami lyofG proteincoupledreceptors,arethemostimpor tantreceptorsinvolvedincardiacregulation[1].ARsin cardiacmuscleincludebothαARsandβARssub types,whileinmostmammalianheart,βARsarethe predominantsubtypes.… 相似文献
57.
Md. Naziruddin Khan A. S. AI-Dwayyan Z. H. Zaidi 《中国物理快报》2006,23(9):2407-2410
Chrysene and 1.2-benzanthracene are successfully doped in a solid wax film and their vibrational spectra in gooo--400cm^-1 are discussed. The harmonic frequencies and relative intensities of both the molecules observed in the film are compared with theoretical values calculated by the density functional theory (DFT) model as well as with the previous experimental data. The effects on spectra due to change of matrix and some additional bands observed in the wax film are also reported. Excellent agreement in the spectral positions and strengths between the experiments and DFT values are found. 相似文献
58.
IntroductionOver the past few years, dimethyl carbonate(DMC) has been proven to be an efficientmethylating,methoxylating, and methoxycarbonylating agent inorganic syntheses, in which DMC is used to replace thetoxic methyl halides, dimethyl sulfate or carb 相似文献
59.
J. MALINEN O. NEVANLINNA V. TURUNEN Z. YUAN 《数学学报(英文版)》2007,23(4):745-748
Let T be a bounded linear operator in a Banach space, with σ(T)={1}. In 1983, Esterle-Berkani' s conjecture was proposed for the decay of differences (I - T) T^n as follows: Eitheror lim inf (n→∞(n+1)||(I-T)T^n||≥1/e or T = I. We prove this claim and discuss some of its consequences. 相似文献
60.
<正> §5.数乘一个数λ与一个函数φ(x)的数乘运算λφ(x)有下列性质1°。如果φ_n(x)是基本列,则λφ_n(x)也是基本列。这个性质能使我们把这种运算推广到任意的广义函数f(x)=[φ_n(x)]上,只要假定 相似文献