全文获取类型
收费全文 | 119298篇 |
免费 | 20571篇 |
国内免费 | 23851篇 |
专业分类
化学 | 87382篇 |
晶体学 | 2538篇 |
力学 | 7716篇 |
综合类 | 2454篇 |
数学 | 16289篇 |
物理学 | 47341篇 |
出版年
2024年 | 353篇 |
2023年 | 1862篇 |
2022年 | 3976篇 |
2021年 | 4099篇 |
2020年 | 4458篇 |
2019年 | 4448篇 |
2018年 | 3848篇 |
2017年 | 4188篇 |
2016年 | 5154篇 |
2015年 | 5765篇 |
2014年 | 6867篇 |
2013年 | 9063篇 |
2012年 | 9893篇 |
2011年 | 10343篇 |
2010年 | 8198篇 |
2009年 | 8209篇 |
2008年 | 9301篇 |
2007年 | 8116篇 |
2006年 | 7574篇 |
2005年 | 6839篇 |
2004年 | 5328篇 |
2003年 | 4381篇 |
2002年 | 4573篇 |
2001年 | 4118篇 |
2000年 | 3770篇 |
1999年 | 2840篇 |
1998年 | 1981篇 |
1997年 | 1640篇 |
1996年 | 1730篇 |
1995年 | 1494篇 |
1994年 | 1407篇 |
1993年 | 1180篇 |
1992年 | 1083篇 |
1991年 | 908篇 |
1990年 | 819篇 |
1989年 | 751篇 |
1988年 | 581篇 |
1987年 | 453篇 |
1986年 | 416篇 |
1985年 | 304篇 |
1984年 | 277篇 |
1983年 | 227篇 |
1982年 | 190篇 |
1981年 | 160篇 |
1980年 | 119篇 |
1979年 | 80篇 |
1978年 | 48篇 |
1976年 | 40篇 |
1975年 | 31篇 |
1974年 | 29篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
1 INTRODUCTION Carbon nanotubes have many potential applica- tions due to their unique structures and properties[1~4]. Physicists have been studying their electrical, me- chanical and other properties since their discove- ries[5, 6]. Recently, chemists are interested in carbon nanotubes because their properties can be altered by chemical functionalization[7~14], and these functiona- lized nanotubes can undergo further chemical trea- tment. So the potential application range of such na- … 相似文献
22.
Kunyu Guo 《Journal of Functional Analysis》2004,213(2):380-411
This paper mainly concerns defect operators and defect functions of Hardy submodules, Bergman submodules over the unit ball, and Hardy submodules over the polydisk. The defect operator (function) carries key information about operator theory (function theory) and structure of analytic submodules. The problem when a submodule has finite defect is attacked for both Hardy submodules and Bergman submodules. Our interest will be in submodules generated by polynomials. The reason for choosing such submodules is to understand the interaction of operator theory, function theory and algebraic geometry. 相似文献
23.
24.
激光等离子体探针及应用研究 总被引:6,自引:1,他引:5
本文介绍用阴影、纹影相干涉方法确定等离子体折射系数变化的原理。分析了等离子体中的非线性效应和对光探测系统的基本要求。并简要叙述了实验上采用的后向喇曼探测束,给出了等离子体干涉、纹影和阴影的测量结果。 相似文献
25.
26.
27.
In the present paper, some new almost fixed point theorems and fixed point theorems for lower semicontinuous type multivalued mappings are obtained in metrizable H-spaces. 相似文献
28.
A new electroactive polynuclear inorganic compound of rare earth metal, gadolinium hexacyanoferrate (GdHCF), was prepared and characterized using the techniques of FTIR spectroscopy, thermogravimetric analysis (TG), UV-Vis spectrometry, X-ray photoelectron spectroscopy (XPS), ICP atomic emission spectroscopy, and EDX. The results of ICP atomic emission spectroscopy, EDX, and TGA indicated that the prepared GdHCF sample had a stoichiometry of NaGdFe(CN)6·12H2O (when GdHCF was prepared in NaCl solution). The FTIR spectrum of GdHCF showed that there were two types of water molecules in the structure of GdHCF: one was the interstitial water (5 H2O), which resulted from the association of water due to H-bonding, and the other was water coordinated with Gd (7 H2O). The results obtained using XPS showed that the oxidation state of Fe and Gd in the GdHCF sample was +2 and +3, respectively. GdHCF was immobilized on the surface of spectroscopically pure graphite (SG) electrode forming the GdHCF/SG electrode, and the solid-state electrochemistry of the resultant electrode was studied using cyclic voltammetry. The cyclic voltammetric results indicated that the GdHCF/SG electrode exhibited a pair of well-defined and stable redox peaks with the formal potential of E0′=(197±3) mV. The effects of the concentration of the supporting electrolyte on the electrochemical characteristics of GdHCF were studied, and the results showed that the value of E0′ increased linearly with the activity of the cationic ion of the supporting electrolyte (lgaNa+), with a slope of 54.1 mV, which may become a novel method for determining the activity of Na+ in solution. Further experimental results indicated that GdHCF had electrocatalytic activities toward the oxidation of dopamine (DA) and ascorbic acid (AA), and the electrocatalytic current increased linearly with the concentration of DA (or AA) in the range of 1.0–10.0 mmol·L?1 (for DA) or 0.5–20.0 mmol·L?1 (for AA). 相似文献
29.
线性泛函方程解的振动性的新结果 总被引:1,自引:0,他引:1
本文研究高阶泛函方程x(g(t))=P(t)x(t)+Q1(t)x(g2(t))+…+Qk(t)x(gk+1(t))解的振动性,得到了一些新的振动条件.改进和推广了已有结果. 相似文献
30.
研究了Fe(acac)3-Al(i-Bu)3-8-羟基喹啉(acac=乙酰丙酮)催化体系催化丙烯酸丁酯(BA)聚合,考察了聚合规律,用凝胶渗透色谱研究了聚合物分子量和分子量分布.动力学研究表明聚合反应对单体浓度呈一级关系,表观活化能为13.9kJ/mol. 相似文献