全文获取类型
收费全文 | 24407篇 |
免费 | 2819篇 |
国内免费 | 2407篇 |
专业分类
化学 | 12316篇 |
晶体学 | 147篇 |
力学 | 952篇 |
综合类 | 169篇 |
数学 | 2009篇 |
物理学 | 5704篇 |
综合类 | 8336篇 |
出版年
2024年 | 93篇 |
2023年 | 394篇 |
2022年 | 671篇 |
2021年 | 726篇 |
2020年 | 729篇 |
2019年 | 673篇 |
2018年 | 541篇 |
2017年 | 549篇 |
2016年 | 835篇 |
2015年 | 943篇 |
2014年 | 1148篇 |
2013年 | 1418篇 |
2012年 | 1656篇 |
2011年 | 1828篇 |
2010年 | 1269篇 |
2009年 | 1250篇 |
2008年 | 1432篇 |
2007年 | 1252篇 |
2006年 | 1132篇 |
2005年 | 1049篇 |
2004年 | 877篇 |
2003年 | 870篇 |
2002年 | 1064篇 |
2001年 | 941篇 |
2000年 | 643篇 |
1999年 | 816篇 |
1998年 | 628篇 |
1997年 | 529篇 |
1996年 | 510篇 |
1995年 | 486篇 |
1994年 | 430篇 |
1993年 | 387篇 |
1992年 | 325篇 |
1991年 | 331篇 |
1990年 | 264篇 |
1989年 | 257篇 |
1988年 | 193篇 |
1987年 | 143篇 |
1986年 | 93篇 |
1985年 | 65篇 |
1984年 | 24篇 |
1983年 | 17篇 |
1982年 | 19篇 |
1981年 | 13篇 |
1980年 | 9篇 |
1963年 | 7篇 |
1959年 | 12篇 |
1958年 | 11篇 |
1957年 | 16篇 |
1956年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
22.
浅析二阶齐次线性变系数微分方程的一个可积类型 总被引:1,自引:0,他引:1
姬志飞 《应用数学与计算数学学报》2006,20(1):125-128
本文讨论了二阶齐次线性变系数微分方程的特殊形式,给出了这种微分方程的一个可积类型. 相似文献
23.
Cai Xiaochun 《Annals of Differential Equations》2006,22(1):1-6
In this paper, we apply a critical point theorem and obtain the condition for the existence of three solutions to two-point boundary value problem of a second order nonlinear difference equation. 相似文献
24.
论联省自治的原动力 总被引:3,自引:0,他引:3
张继才 《上饶师范学院学报》2002,22(1):82-85
联省自治的产生是资产阶级联省自治派和地方军阀产生合力的结果。但是,联省自治思潮与运动一开始就将斗争锋芒直指北洋军阀专制主义中央集权和地方军阀的地方割据。资产阶级联省自治派是联省自治思潮的鼓吹者、联省自治团体的组织者、联省自治运动的直接发动者,因而是运动的原动力,地方军阀则是附合者,而且是别有用心的。 相似文献
25.
This study examined how selected U.S. and Asian mathematics curricula are designed to facilitate students' understanding of the arithmetic average. There is a consistency regarding the learning goals among these curriculum series, but the focuses are different between the Asian series and the U.S. reform series. The Asian series and the U.S. commercial series focus the arithmetic average more on conceptual and procedural understanding of the concept as a computational algorithm than on understanding the concept as a representative of a data set; however, the two U.S. reform series focus the concept more on the latter. Because of the different focuses, the Asian and the U.S. curriculum series treat the concept differently. In the Asian series, the concept is first introduced in the context of “equal‐sharing” or “per‐unit‐quantity,” and the averaging formula is formally introduced at a very early stage. In the U.S. reform series, the concept is discussed as a measure of central tendency, and after students have some intuitive ideas of the statistical aspect of the concept, the averaging algorithm is briefly introduced. 相似文献
26.
离子交换富集-导数火焰原子吸收法测定自来水中Cu,Fe和Zn 总被引:7,自引:0,他引:7
本文研究了用 2 0 1× 7阳离子交换树脂对自来水中的微量元素进行交换富集 ,采用微量脉冲进样 导数火焰原子吸收法测定富集后溶液中的Cu ,Fe和Zn ,该方法灵敏度分别为 0 2 9,0 5 9和 0 0 6 μg·L- 1 ,精密度分别为 4 2 8% ,1 95 %和 2 2 8% ,检测限分别为 1 2 8,5 85和 0 6 8μg·L- 1 ,回收率分别为 91 13% ,10 1 34%和99 84 % ,本方法大大减少了需样量 ,简便快速 ,灵敏度高。 相似文献
27.
Based on the Collins formula and irradiance moments definition, the propagation of the kurtosis parameter of super-Gaussian beams through a spherically aberrated lens is studied. Detailed numerical results are given. It is shown that, as compared with aberration-free super-Gaussian beams, the profile of spherically aberrated super-Gaussian beams can be leptokurtic, mesokurtic or platykurtic, depending on the aberration and propagation distance. The results for the spherically aberrated Gaussian beams can be dealt with as a special case treated in this paper. Finally, the advantage of our method is pointed out. 相似文献
28.
Summary Some estimators of maximum likelihood type are constructed for estimating functionals of one-dimensional Gibbs states. We also show that those estimators are strongly consistent, asymptotically normal and asymptotically efficient. 相似文献
29.
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
30.