全文获取类型
收费全文 | 18079篇 |
免费 | 1705篇 |
国内免费 | 2178篇 |
专业分类
化学 | 7629篇 |
晶体学 | 144篇 |
力学 | 2340篇 |
综合类 | 201篇 |
数学 | 6112篇 |
物理学 | 5536篇 |
出版年
2024年 | 20篇 |
2023年 | 209篇 |
2022年 | 245篇 |
2021年 | 394篇 |
2020年 | 563篇 |
2019年 | 500篇 |
2018年 | 490篇 |
2017年 | 604篇 |
2016年 | 724篇 |
2015年 | 544篇 |
2014年 | 853篇 |
2013年 | 1742篇 |
2012年 | 964篇 |
2011年 | 1181篇 |
2010年 | 958篇 |
2009年 | 1173篇 |
2008年 | 1202篇 |
2007年 | 1256篇 |
2006年 | 1030篇 |
2005年 | 838篇 |
2004年 | 810篇 |
2003年 | 691篇 |
2002年 | 673篇 |
2001年 | 542篇 |
2000年 | 527篇 |
1999年 | 468篇 |
1998年 | 399篇 |
1997年 | 322篇 |
1996年 | 273篇 |
1995年 | 308篇 |
1994年 | 240篇 |
1993年 | 213篇 |
1992年 | 166篇 |
1991年 | 156篇 |
1990年 | 100篇 |
1989年 | 93篇 |
1988年 | 73篇 |
1987年 | 63篇 |
1986年 | 48篇 |
1985年 | 51篇 |
1984年 | 49篇 |
1983年 | 30篇 |
1982年 | 34篇 |
1981年 | 29篇 |
1980年 | 29篇 |
1979年 | 25篇 |
1978年 | 11篇 |
1977年 | 17篇 |
1976年 | 10篇 |
1973年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
K-g-框架是将算子K引入到g-框架中的一种特殊框架.采用泛函分析中的技巧和方法,研究K-g-框架的稳定性,并得到了四个K-g-框架在扰动情况下稳定的充分条件.此外,结合算子K和框架算子S衍生出K-g-框架的三个等式,并通过引入参数λ建立关于K-g-框架的一些不等式. 相似文献
12.
13.
14.
This study investigated the effects of different treatment of alkaline pH-shifting on milk protein concentrate (MPC), micellar casein concentrate (MCC) and whey protein isolate (WPI) assisted by the same ultrasound conditions, including changes in the physicochemical properties, solubility and foaming capacity. The solubility of milk proteins had a significant increase with gradual enhancement of ultrasound-assisted alkaline pH-shifting (p < 0.05), especially for MCC up to 99.50 %. Also, treatment made a significant decline in the particle size of MPC and MCC, as well as the turbidity of the proteins (p < 0.05). The foaming capacity of MPC, MCC, and WPI was all improved, especially at pH 11, and at this pH, the milk protein also showed the highest surface hydrophobicity. The best foaming capacity at pH 11 was the result of the combined effect of particle size, potential, protein conformation, solubility, and surface hydrophobicity. In conclusion, ultrasound-assisted pH-shifting treatment was found to be effective in improving the physicochemical properties and solubility and foaming capacity of milk proteins, especially MCC, with promising application prospect in food industry. 相似文献
15.
16.
Mossel and Ross raised the question of when a random coloring of a graph can be reconstructed from local information, namely, the colorings (with multiplicity) of balls of given radius. In this article, we are concerned with random 2-colorings of the vertices of the -dimensional hypercube, or equivalently random Boolean functions. In the worst case, balls of diameter are required to reconstruct. However, the situation for random colorings is dramatically different: we show that almost every 2-coloring can be reconstructed from the multiset of colorings of balls of radius 2. Furthermore, we show that for , almost every -coloring can be reconstructed from the multiset of colorings of 1-balls. 相似文献
17.
ZHANG Xinyu TANG Pengpeng ZHAI Guangyao LIN Xiu ZHANG Qiang CHEN Jiesheng WEI Xiao 《高等学校化学研究》2022,38(5):1292-1300
In this study, we have provided a facile solution to synthesize well-aligned titanium dioxide nanorods by using hydrothermal reaction. By calcining the materials under different atmospheres and temperatures, a batch of titanium dioxides with excellent oxygen evolution reaction(OER) catalytic efficiency were obtained. This new structured TiO2 photoanode material yields a high photocurrent density of 5.69 mA/cm2 at 1.23 V vs. reversible hydrogen electrode(RHE) under simulated solar light(100 mW/cm2). Surface photovoltage techniques and other measurements were carried out to confirm that the enhanced photoelectrochemical performances were attributed to the synergistic effect of the phase junction and a certain content of surface states, which accelerate the separation and transmission of the photogenerated charges. This material with phase junction and surface states promises a potential application in the field of photoelectric catalysis under solar light. 相似文献
18.
Dr. Celina Sikorska 《Chemphyschem》2019,20(17):2236-2246
Superhalogens, owing to their large electron affinity (EA, exceeding those of any halogen atom), play an essential role in physical chemistry as well as new material design. They have applications in hydrogen storage and lithium-ion batteries. Owing to the unique geometries and electronic features of magnesium-based clusters, their potential to form a new class of lithium salts has been investigated here theoretically. The idea is assessed by conducting ab initio computations on Li+/MgnF2n+1-2mOm− compounds (n=2, 3; m=0-3) and analyzing their performance as potential Li-ion battery electrolytes. The Mg3F7− cluster, with large electron binding energy (EA of 7.93 eV), has been proven to serve as a building block for lithium salts. It is shown that, apart from high electronic stability, the new superhalogen-based electrolytes exhibit a set of desirable properties, including a large band gap, high electrolyte stability window, easy mobility of the Li+, and favorable insensitivity to water. 相似文献
19.
为明确超声共振频谱分析法(RUS)测定圆柱体试样弹性常数的影响因素, 由此针对各向同性圆柱体开展实验, 观察圆柱体试样测量结果的分散性和稳定性, 且主要研究横纵比和有效模态数量对测量结果的影响, 并与拉伸试验的结果进行比较. 以测量结果标准差、变异系数和95%置信度下均值的区间估计3个指标来衡量结果的稳定性和分散性, 且从模态简并角度对实验结果进行分析. 最终结果表明, 当超声共振频谱分析法的有效模态数量在17左右、试样横纵比接近1时, 测量结果的稳定性和分散性较小. 相似文献
20.