全文获取类型
收费全文 | 3200篇 |
免费 | 475篇 |
国内免费 | 388篇 |
专业分类
化学 | 2479篇 |
晶体学 | 31篇 |
力学 | 183篇 |
综合类 | 43篇 |
数学 | 328篇 |
物理学 | 999篇 |
出版年
2024年 | 13篇 |
2023年 | 65篇 |
2022年 | 100篇 |
2021年 | 122篇 |
2020年 | 144篇 |
2019年 | 136篇 |
2018年 | 99篇 |
2017年 | 105篇 |
2016年 | 145篇 |
2015年 | 135篇 |
2014年 | 186篇 |
2013年 | 229篇 |
2012年 | 249篇 |
2011年 | 305篇 |
2010年 | 205篇 |
2009年 | 162篇 |
2008年 | 181篇 |
2007年 | 172篇 |
2006年 | 158篇 |
2005年 | 140篇 |
2004年 | 118篇 |
2003年 | 96篇 |
2002年 | 98篇 |
2001年 | 83篇 |
2000年 | 77篇 |
1999年 | 84篇 |
1998年 | 76篇 |
1997年 | 52篇 |
1996年 | 56篇 |
1995年 | 41篇 |
1994年 | 44篇 |
1993年 | 30篇 |
1992年 | 39篇 |
1991年 | 16篇 |
1990年 | 25篇 |
1989年 | 13篇 |
1988年 | 9篇 |
1987年 | 5篇 |
1986年 | 10篇 |
1985年 | 8篇 |
1984年 | 14篇 |
1983年 | 9篇 |
1982年 | 3篇 |
1981年 | 3篇 |
1980年 | 1篇 |
1978年 | 1篇 |
1957年 | 1篇 |
排序方式: 共有4063条查询结果,搜索用时 390 毫秒
121.
Dr. Yungen Liu Dr. Chun-Wai Tse Dr. Kar-Yee Lam Dr. Xiao-Yong Chang Dr. Xiangguo Guan Meng-Yao Chao Dr. Jie-Sheng Huang Prof. Dr. Chi-Ming Che 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(46):10828-10833
Ruthenium(II) complexes bearing a tridentate bis(N-heterocyclic carbene) ligand reacted with iminoiodanes (PhI=NR) resulting in the formation of isolable ruthenium(III)–amido intermediates, which underwent cleavage of a C−N bond of the tridentate ligand and formation of an N-substituted imine group. The RuIII–amido intermediates have been characterized by 1H NMR, UV/Vis, ESI-MS, and X-ray crystallography. DFT calculations were performed to provide insight into the reaction mechanism. 相似文献
122.
High‐Level Incorporation of Silver in Gold Nanoclusters: Fluorescence Redshift upon Interaction with Hydrogen Peroxide and Fluorescence Enhancement with Herbicide 下载免费PDF全文
Dr. Guijian Guan Dr. Yongqing Cai Dr. Shuhua Liu Dr. Haidong Yu Dr. Shiqiang Bai Dr. Yuan Cheng Dr. Tao Tang Dr. M. S. Bharathi Prof. Yong‐Wei Zhang Prof. Ming‐Yong Han 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(5):1675-1681
High‐level incorporation of Ag in Au nanoclusters (NCs) is conveniently achieved by controlling the concentration of Ag+ in the synthesis of bovine serum albumin (BSA)‐protected Au NCs, and the resulting structure is determined to be bimetallic Ag28Au10‐BSA NCs through a series of characterizations including energy‐dispersive X‐ray spectroscopy, mass spectroscopy, and X‐ray photoelectron spectroscopy, together with density functional theory simulations. Interestingly, the Ag28Au10 NCs exhibit a significant fluorescence redshift rather than quenching upon interaction with hydrogen peroxide, providing a new approach to the detection of hydrogen peroxide through direct comparison of their fluorescence peaks. Furthermore, the Ag28Au10 NCs are also used for the sensitive and selective detection of herbicide through fluorescence enhancement. The detection limit for herbicide (0.1 nm ) is far below the health value established by the U.S. Environmental Protection Agency; such sensitive detection was not achieved by using AuAg NCs with low‐level incorporation of Ag or by using the individual metal NCs. 相似文献
123.
Zou Fan Zuo Jing Geng Chao Li Feng Huang Guan Liu Jiaying Jiang Jiali Fan Zhihua Li Xinyang 《Journal of Russian Laser Research》2021,42(4):462-467
Journal of Russian Laser Research - Laser aiming is one of the key technologies of laser atmospheric transmission. The beam actually is affected by atmospheric turbulence and mechanical vibration;... 相似文献
124.
125.
Xiao‐Jie Liu Zhen‐Yu Li Zhong‐Feng Li Xiao‐Xia Gao Yu‐Zhi Zhou Hai‐Feng Sun Li‐Zeng Zhang Xiao‐Qing Guo Guan‐Hua Du Xue‐Mei Qin 《Magnetic resonance in chemistry : MRC》2012,50(3):187-192
Chronic unpredictable mild stress (CUMS) is a well‐validated model of depression. In this study, a urinary metabonomics method based on the NMR spectrometry was used to study the metabolic perturbation in CUMS‐induced rat depression model. With pattern recognition analysis, a clear separation of CUMS rats and healthy controls was achieved, and nine endogenous metabolites contributing to the separation were identified. CUMS‐treated rats were characterized by the increase of glycine, pyruvate, glutamine, and asparagines, as well as the decrease of 2‐oxoglutarate, dimethylglycine, citrate, succinate, and acetate. The urinary biochemical changes related to the metabolic disturbance in CUMS induced depression, and the possible correlations with live qi stagnation in traditional Chinese medicine are discussed. The work shows that CUMS is a reliable model for studying depression, and the noninvasive urinary metabolomic method is a valuable tool to investigate the biochemical pertubations in depression as an early diagnostic means. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
126.
Naive Bayes (NB) is one of the most popular classification methods. It is particularly useful when the dimension of the predictor is high and data are generated independently. In the meanwhile, social network data are becoming increasingly accessible, due to the fast development of various social network services and websites. By contrast, data generated by a social network are most likely to be dependent. The dependency is mainly determined by their social network relationships. Then, how to extend the classical NB method to social network data becomes a problem of great interest. To this end, we propose here a network-based naive Bayes (NNB) method, which generalizes the classical NB model to social network data. The key advantage of the NNB method is that it takes the network relationships into consideration. The computational effciency makes the NNB method even feasible in large scale social networks. The statistical properties of the NNB model are theoretically investigated. Simulation studies have been conducted to demonstrate its finite sample performance. A real data example is also analyzed for illustration purpose. 相似文献
127.
Haichao Zhu Meihua Liu Haiyan Li Ting Guan Qi Zhang Yang Chen Yingxiang Liu Rolf R. Hartmann Lina Yin Qingzhong Hu 《中国化学快报》2021,32(7):2327-2332
Exorbitant aldosterone is closely associated with various severe diseases, including congestive heart failure and chronic kidney disease. As aldosterone synthase is the pivotal enzyme in aldosterone biosynthesis, its inhibition constitutes a promising treatment for these diseases. Via a structure-based approach, a series of pyridyl substituted 3,4-dihydrobenzo[f][1,4]oxazepin-5(2H)-ones were designed as inhibitors of aldosterone synthase. Six compounds (5j, 5l, 5m 5w, 5x and 5y) distinguished themselves with potent inhibition (IC50 <100 nmol/L) and high selectivity over homogenous 11β-hydroxylase. As the most promising compound, 5x exhibited an IC50 of 12 nmol/L and an excellent selectivity factor (SF) of 157, which are both superior to those of the reference fadrazole (IC50 = 21 nmol/L, SF = 7). Importantly, 5x showed no inhibition against steroidogenic CYP17, CYP19 and a panel of hepatic CYP enzymes indicating an outstanding safety profile. As it manifested satisfactory pharmacokinetic properties in rats, compound 5x was considered as a drug candidate for further development. 相似文献
128.
129.
Yang Guo Chen Corresponding author Zhang Zhi Guo Li Li Guan Rong Hua 《Liquid crystals》2013,40(12):1441-1447
The planar aligned nematic liquid crystal cell with different anchoring for the two substrates (i.e. a non-symmetric NLC cell) is investigated by an analytical method. We deduce the basic equations and the boundary conditions of the tilt angle θ of the LC director. Expressions for threshold and saturation magnetic field are obtained, and numerical results of these two quantities with variation in anchoring parameters of the two substrates are given. A symmetry breaking parameter Δ is introduced and the relations between Δ and applied field, as well as the two sets of anchoring parameters are discussed in detail. A feasible experimental plan for measurement of anchoring strengths of a series of different substrates is proposed. 相似文献