全文获取类型
收费全文 | 249117篇 |
免费 | 5555篇 |
国内免费 | 3635篇 |
专业分类
化学 | 119072篇 |
晶体学 | 3297篇 |
力学 | 13354篇 |
综合类 | 307篇 |
数学 | 39707篇 |
物理学 | 82570篇 |
出版年
2020年 | 1520篇 |
2019年 | 1471篇 |
2018年 | 10855篇 |
2017年 | 11754篇 |
2016年 | 6580篇 |
2015年 | 2977篇 |
2014年 | 2716篇 |
2013年 | 6476篇 |
2012年 | 9908篇 |
2011年 | 19732篇 |
2010年 | 11906篇 |
2009年 | 11795篇 |
2008年 | 16845篇 |
2007年 | 20527篇 |
2006年 | 5532篇 |
2005年 | 12474篇 |
2004年 | 8094篇 |
2003年 | 7452篇 |
2002年 | 5250篇 |
2001年 | 4331篇 |
2000年 | 3456篇 |
1999年 | 2648篇 |
1998年 | 2249篇 |
1997年 | 2151篇 |
1996年 | 2077篇 |
1995年 | 2046篇 |
1994年 | 1802篇 |
1993年 | 1703篇 |
1992年 | 1855篇 |
1991年 | 1862篇 |
1990年 | 1781篇 |
1989年 | 1772篇 |
1988年 | 1779篇 |
1987年 | 1764篇 |
1986年 | 1645篇 |
1985年 | 2209篇 |
1984年 | 2349篇 |
1983年 | 1960篇 |
1982年 | 2267篇 |
1981年 | 2089篇 |
1980年 | 2123篇 |
1979年 | 2140篇 |
1978年 | 2259篇 |
1977年 | 2078篇 |
1976年 | 2146篇 |
1975年 | 2081篇 |
1974年 | 1910篇 |
1973年 | 2175篇 |
1972年 | 1304篇 |
1968年 | 1150篇 |
排序方式: 共有10000条查询结果,搜索用时 625 毫秒
1.
Yang T. L. Kao C. L. Kuo C. E. Yeh H. C. Li W. J. Li H. T. Chen C. Y. 《Chemistry of Natural Compounds》2022,58(5):825-827
Chemistry of Natural Compounds - A novel bibenzyl derivative, hydrangchinenin (1), was isolated from the stems of Hydrangea chinensis Maxim. (Hydrangeaceae). Its structure was determined on the... 相似文献
2.
3.
Qianqian Fan Zirui Liu Feng Qiu Prof. Yong Mao Prof. Qingju Liu Prof. Longzhou Zhang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(63):e202202700
The artificially accurate design of nonmetal electrocatalysts’ active site has been a huge challenge because no pure active species with the specific structure could be strictly controlled by traditional synthetic methods. Species with a multiconfiguration in the catalyst hinder identification of the active site and the subsequent comprehension of the reaction mechanism. We have developed a novel electro-assisted molecular assembly strategy to obtain a pure pentagon ring on perfect graphene avoiding other reconstructed structures. More importantly, the active atom was confirmed by the subtle passivation process as the topmost carbon atom. Recognition of the carbon-defect electrocatalysis reaction mechanism was first downsized to the single-atom scale from the experimental perspective. It is expected that this innovative electro-assisted molecular assembly strategy could be extensively applied in the active structure-controlled synthesis of nonmetal electrocatalysts and verification of the exact active atom. 相似文献
4.
5.
Theoretical and Mathematical Physics - Dynamic systems acting on the plane and possessing the Wada property have been observed. There exist only two topological types, symmetric and antisymmetric,... 相似文献
6.
针对公众参与的语言信息多属性群决策问题,研究了考虑参与者满意度的概率语言多属性群决策方法。首先,根据参与者的语言评价信息确定并规范化概率语言决策矩阵。然后,对大群体进行共识分析,由最大化参与者群体的满意度构建线性规划模型,确定参与者群组的权重;构造正、负理想方案的评价向量,构建多目标规划模型,用拉格朗日乘子法求解属性权重;定义各方案的加权贴近度,并以此对方案进行排序和优选。最后,通过新型智慧城市市民获得感评价案例验证了模型的可行性和有效性。 相似文献
7.
8.
Li Y. Shi W. H. Dong L. M. Xu S. X. Huang H. J. Yin J. R. 《Journal of Applied Spectroscopy》2022,89(3):534-541
Journal of Applied Spectroscopy - Sr3B2O6:Dy3+, Eu3+ single-matrix white-light-emitting materials are prepared using the high-temperature solid-state method. The microstructure, emission spectrum,... 相似文献
9.
Ajit Kumar Singh Seulgi Ji Baghendra Singh Chittaranjan Das Heechae Choi Prashanth W. Menezes Arindam Indra 《Materials Today Chemistry》2022
Herein, we report a Mott-Schottky catalyst by entrapping cobalt nanoparticles inside the N-doped graphene shell (Co@NC). The Co@NC delivered excellent oxygen evolution activity with an overpotential of merely 248 mV at a current density of 10 mA cm–2 with promising long-term stability. The importance of Co encapsulated in NC has further been demonstrated by synthesizing Co nanoparticles without NC shell. The synergy between the hexagonal close-packed (hcp) and face-centered cubic (fcc) Co plays a major role to improve the OER activity, whereas the NC shell optimizes the electronic structure, improves the electron conductivity, and offers a large number of active sites in Co@NC. The density functional theory calculations have revealed that the hcp Co has a dominant role in the surface reaction of electrocatalytic oxygen evolution, whereas the fcc phase induces the built-in electric field at the interfaces with N-doped graphene to accelerate the H+ ion transport. 相似文献
10.
Restricted testing conditions were considered recently. For the maximal operator, Hytönen, Li and Sawyer [8] first obtained parental testing condition. Later, they [9] showed that it suffices to restrict testing to doubling cubes. Chen and Lacey [3] gave a similar restricted testing condition. In our paper, we discuss a version of the latter in the multilinear setting.
相似文献