全文获取类型
收费全文 | 26008篇 |
免费 | 4634篇 |
国内免费 | 4248篇 |
专业分类
化学 | 20823篇 |
晶体学 | 448篇 |
力学 | 1363篇 |
综合类 | 362篇 |
数学 | 3063篇 |
物理学 | 8831篇 |
出版年
2024年 | 45篇 |
2023年 | 448篇 |
2022年 | 845篇 |
2021年 | 940篇 |
2020年 | 1064篇 |
2019年 | 1134篇 |
2018年 | 911篇 |
2017年 | 880篇 |
2016年 | 1264篇 |
2015年 | 1446篇 |
2014年 | 1687篇 |
2013年 | 2081篇 |
2012年 | 2429篇 |
2011年 | 2485篇 |
2010年 | 1854篇 |
2009年 | 1824篇 |
2008年 | 2019篇 |
2007年 | 1789篇 |
2006年 | 1626篇 |
2005年 | 1346篇 |
2004年 | 1180篇 |
2003年 | 855篇 |
2002年 | 929篇 |
2001年 | 720篇 |
2000年 | 561篇 |
1999年 | 422篇 |
1998年 | 359篇 |
1997年 | 283篇 |
1996年 | 238篇 |
1995年 | 168篇 |
1994年 | 166篇 |
1993年 | 146篇 |
1992年 | 123篇 |
1991年 | 95篇 |
1990年 | 104篇 |
1989年 | 67篇 |
1988年 | 62篇 |
1987年 | 47篇 |
1986年 | 51篇 |
1985年 | 43篇 |
1984年 | 23篇 |
1983年 | 23篇 |
1982年 | 13篇 |
1981年 | 10篇 |
1980年 | 12篇 |
1978年 | 8篇 |
1977年 | 5篇 |
1976年 | 6篇 |
1974年 | 4篇 |
1936年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 218 毫秒
931.
932.
933.
934.
Yuhua Xue Jun Liu Hao Chen Ruigang Wang Dingqiang Li Jia Qu Liming Dai 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2012,124(48):12300-12300
935.
Bhaskar Garg Shiou-Ling Lei Shou-Ching Liu Tanuja Bisht Jen-Yu Liu Yong-Chien Ling 《Analytica chimica acta》2012
The time-of-flight secondary ion mass spectrometry (TOF-SIMS) has emerged as a powerful tool for the unswerving detection of biomolecules, in particular, proteins and peptides. To date, there is very little information available on the direct determination of trimethyl/triethyl amines using TOF-SIMS. One major hurdle in this regard is an ultrahigh vacuum system, usually needed in TOF-SIMS, which hampers its usability to trimethyl/triethyl amines owing to their high evaporation rate. We designed an efficient and sensitive protocol for rapid identification and sensitive determination of tertiaryalkyl amines using TOF-SIMS. The amines were derivatized by reaction with 1,4-butane sultone and sulphuric acid sequentially to afford the corresponding sulphonic acidic ionic liquids (ILs). The TOF-SIMS analysis of these task-specific ILs (TSILs) was carried out in both positive and negative polarity. The positive ion mass spectra of TSILs showed sharp fragmented peaks for tertiaryalkyl amines at typical level and up to 10 ppm. The possible mechanism for different fragmentation pathways in positive polarity was discussed. 相似文献
936.
937.
Shuyang Liu Miao Tian Dr. Xiubin Bu Dr. Hua Tian Prof. Xiaobo Yang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(28):7738-7744
Photoactive two-dimensional covalent organic frameworks (2D-COFs) have become promising heterogenous photocatalysts in visible-light-driven organic transformations. Herein, a visible-light-driven selective aerobic oxidation of various small organic molecules by using 2D-COFs as the photocatalyst was developed. In this protocol, due to the remarkable photocatalytic capability of hydrazone-based 2D-COF-1 on molecular oxygen activation, a wide range of amides, quinolones, heterocyclic compounds, and sulfoxides were obtained with high efficiency and excellent functional group tolerance under very mild reaction conditions. Furthermore, benefiting from the inherent advantage of heterogenous photocatalysis, prominent sustainability and easy photocatalyst recyclability, a drug molecule (modafinil) and an oxidized mustard gas simulant (2-chloroethyl ethyl sulfoxide) were selectively and easily obtained in scale-up reactions. Mechanistic investigations were conducted using radical quenching experiments and in situ ESR spectroscopy, all corroborating the proposed role of 2D-COF-1 in photocatalytic cycle. 相似文献
938.
Huiyun Wu Xin Li Shen Sheng Zhisong Huang Shuhai Huang Siqing Zhao Hua Wang Zhenhai Sun Xiegu Xu Rui Xiao 《Optik》2013
Model of an optical system with coherent laser array source and the piston phase optimized by the stochastic parallel gradient descent algorithm is established. With this model, theory of beam propagation through the optical system in turbulent atmosphere is analyzed, and the analytical formulas of the beam average intensity along the propagation path are derived. Strehl ratio of the received beam induced by intensity disorderly distribution and power efficiency of the received beam are introduced to evaluate performance of the optical system. Under the H-V 5/7 atmospheric turbulent model, performance of an optical system with determinate parameters was calculated, and the influences of the propagation distance and the laser wavelength were numerically analyzed, respectively. 相似文献
939.
940.