全文获取类型
收费全文 | 183762篇 |
免费 | 18768篇 |
国内免费 | 14067篇 |
专业分类
化学 | 100075篇 |
晶体学 | 1987篇 |
力学 | 12608篇 |
综合类 | 886篇 |
数学 | 45070篇 |
物理学 | 55971篇 |
出版年
2024年 | 110篇 |
2023年 | 2103篇 |
2022年 | 2452篇 |
2021年 | 3496篇 |
2020年 | 4434篇 |
2019年 | 4251篇 |
2018年 | 13366篇 |
2017年 | 12948篇 |
2016年 | 10855篇 |
2015年 | 6022篇 |
2014年 | 6776篇 |
2013年 | 8715篇 |
2012年 | 13575篇 |
2011年 | 20372篇 |
2010年 | 12771篇 |
2009年 | 12855篇 |
2008年 | 13890篇 |
2007年 | 15125篇 |
2006年 | 6648篇 |
2005年 | 6664篇 |
2004年 | 5702篇 |
2003年 | 5300篇 |
2002年 | 4093篇 |
2001年 | 2796篇 |
2000年 | 2469篇 |
1999年 | 2364篇 |
1998年 | 2029篇 |
1997年 | 1781篇 |
1996年 | 1783篇 |
1995年 | 1529篇 |
1994年 | 1368篇 |
1993年 | 1126篇 |
1992年 | 992篇 |
1991年 | 880篇 |
1990年 | 729篇 |
1989年 | 592篇 |
1988年 | 461篇 |
1987年 | 409篇 |
1986年 | 398篇 |
1985年 | 325篇 |
1984年 | 236篇 |
1983年 | 194篇 |
1982年 | 168篇 |
1981年 | 118篇 |
1980年 | 113篇 |
1979年 | 73篇 |
1978年 | 70篇 |
1976年 | 42篇 |
1973年 | 43篇 |
1914年 | 45篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
BIT Numerical Mathematics - We present randomized algorithms based on block Krylov subspace methods for estimating the trace and log-determinant of Hermitian positive semi-definite matrices. Using... 相似文献
62.
研究采用有误差的数值计算来获得无误差的准确值具有重要的理论价值和应用价值.这种通过近似的数值方法获得准确结果的计算被称为零误差计算.本文首先指出,只有一致离散集合中的数才能够开展零误差计算,即有非零隔离界的数集,这也是"数"可以进行零误差计算的一个充要条件.以此为基本出发点,本文分析代数数零误差计算的最低理论精度,该精度对应于恢复近似代数数的准确值时必要的误差控制条件,但由于所采用恢复算法的局限性,这一理论精度往往不能保证成功恢复出代数数的准确值.为此,本文给出采用PSLQ (partial-sum-LQ-decomposition)算法进行代数数零误差计算所需的精度控制条件,与基于LLL (Lenstra-Lenstra-Lovász)算法相比,该精度控制条件关于代数数次数的依赖程度由二次降为拟线性,从而可降低相应算法的复杂度.最后探讨零误差计算未来的发展趋势. 相似文献
63.
64.
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
65.
Yi-Tong Xu Tian-Yang Zhang Zheng Li Xiang-Nan Liu Yuan-Cheng Zhu Wei-Wei Zhao Hong-Yuan Chen Jing-Juan Xu 《Electroanalysis》2022,34(6):947-955
Photoelectrochemical (PEC) cytosensors, a combination of the PEC process and the living-cell assay, have emerged as a powerful tool in the analytical and biological science. This mini review provides a brief introduction of this arena and summaries the key steps about the development of PEC cytosensors with representative examples, followed by future prospects based on our own opinions. 相似文献
66.
67.
Li Jun Zheng Dayong Wei Ning Sun Yunfeng Liu Li Yuan Yuan Jiang Qinghua 《Chemistry of Natural Compounds》2022,58(4):650-652
Chemistry of Natural Compounds - A new quassinoid, dehydrobruceantinol B (1), was isolated from the seeds of Brucea javanica, together with two known compounds, bruceantinol (2) and bruceine A (3).... 相似文献
68.
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
69.
Hu Bing Guo Fangsong Li Shanrong Yang Can Lin Wei Zhang Jinshui Hou Yidong Wang Xinchen 《Research on Chemical Intermediates》2022,48(6):2295-2311
Research on Chemical Intermediates - Element doping has demonstrated an effective strategy for enhancing photocatalytic performance of carbon nitride (CN). Herein, we reported that oxygen-doped CN... 相似文献
70.
Cheng Ren Guanghao Ji Xiankai Li Prof. Jing Zhang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(53):e202201442
The direct hydrodimerization of acrylates and acrylonitrile offers a general streamlined access to industrially important intermediates to nylon 6,6. However, a practical catalytic method for this process has thus far underdeveloped owing to the challenges in regioselectivity and environmental compatibility of applied reagents. Here, we report a cobalt-catalyzed tail-to-tail hydrodimerization of activated alkenes driven by a visible-light photoredox catalysis at ambient temperature, which is applicable to both adipates and adiponitrile synthesis from potentially renewable feedstocks. This protocol utilizes half equivalent of hantzsch ester as a recyclable two-electron and two-proton donor with the assistance of catalytic amount of base as a proton shuttle, and has been shown to be highly regioselective and efficient for hydrodimerizing various activated alkenes to 1,4-difunctionalized butane derivatives. 相似文献