全文获取类型
收费全文 | 2981篇 |
免费 | 519篇 |
国内免费 | 467篇 |
专业分类
化学 | 2221篇 |
晶体学 | 46篇 |
力学 | 128篇 |
综合类 | 44篇 |
数学 | 311篇 |
物理学 | 1217篇 |
出版年
2024年 | 10篇 |
2023年 | 76篇 |
2022年 | 136篇 |
2021年 | 139篇 |
2020年 | 175篇 |
2019年 | 163篇 |
2018年 | 151篇 |
2017年 | 150篇 |
2016年 | 176篇 |
2015年 | 187篇 |
2014年 | 180篇 |
2013年 | 229篇 |
2012年 | 238篇 |
2011年 | 272篇 |
2010年 | 198篇 |
2009年 | 191篇 |
2008年 | 193篇 |
2007年 | 140篇 |
2006年 | 129篇 |
2005年 | 92篇 |
2004年 | 84篇 |
2003年 | 93篇 |
2002年 | 74篇 |
2001年 | 70篇 |
2000年 | 51篇 |
1999年 | 57篇 |
1998年 | 62篇 |
1997年 | 42篇 |
1996年 | 39篇 |
1995年 | 30篇 |
1994年 | 25篇 |
1993年 | 21篇 |
1992年 | 15篇 |
1991年 | 15篇 |
1990年 | 8篇 |
1989年 | 5篇 |
1988年 | 5篇 |
1987年 | 11篇 |
1986年 | 13篇 |
1985年 | 3篇 |
1984年 | 2篇 |
1983年 | 3篇 |
1982年 | 7篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1968年 | 1篇 |
1957年 | 1篇 |
1936年 | 3篇 |
排序方式: 共有3967条查询结果,搜索用时 31 毫秒
91.
Shuang Men Yujuan Jin 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2018,92(11):2337-2340
Russian Journal of Physical Chemistry A - We investigate the imidazolium-based zwitterions, 1-butyl-3-methylimidazolium-2-pentafluorophosphate, together with 1-butyl-3-methylimidazolium... 相似文献
92.
Shuang Dong Ziqin Jiang Zhen Liu Ling Chen Qiang Zhang Youli Tian Amir Sohail Muhammad Idrees Khan Hua Xiao Xiaoping Liu Yuxing Wang Honggen Li Hanyu Wu Weiwen Liu Chengxi Cao 《Electrophoresis》2020,41(16-17):1529-1538
As an effective separation tool, free-flow electrophoresis has not been used for purification of low-abundance protein in complex sample matrix. Herein, lysozyme in complex egg white matrix was chosen as the model protein for demonstrating the purification of low-content peptide via an FFE coupled with gel fitration chromatography (GFC). The crude lysozyme in egg while was first separated via free-flow zone electrophoresis (FFZE). After that, the fractions with lysozyme activity were condensed via lyophilization. Thereafter, the condensed fractions were further purified via a GFC of Sephadex G50. In all of the experiments, a special poly(acrylamide- co-acrylic acid) (P(AM-co-AA)) gel electrophoresis and a mass spectrometry were used for identification of lysozyme. The conditions of FFZE were optimized as follows: 130 μL/min sample flow rate, 4.9 mL/min background buffer of 20 mM pH 5.5 Tris-Acetic acid, 350 V, and 14 °C as well as 2 mg/mL protein content of crude sample. It was found that the purified lysozyme had the purity of 80% and high activity as compared with its crude sample with only 1.4% content and undetectable activity. The recoveries in the first and second separative steps were 65% and 82%, respectively, and the total recovery was about 53.3%. The reasons of low recovery might be induced by diffusion of lysozyme out off P(AM-co-AA) gel and co-removing of high-abundance egg ovalbumin. All these results indicated FFE could be used as alternative tool for purification of target solute with low abundance. 相似文献
93.
Dongdong Li Luyao Wang Ernesto Yagüe Linlin Dai Xiumei Zhao Zibo Yang Shuang Zhi Yunhui Hu 《应用有机金属化学》2019,33(10)
An innovative ternary copper(II) complex, [Cu(Cl‐PIP)(Tyr)Cl]n, has been synthesized and characterized using infrared spectroscopy, elemental analysis and single‐crystal X‐ray diffraction analysis. X‐ray crystallography indicates that the Cu atom is five‐coordinated in a square‐pyramidal configuration. The unit forms a one‐dimensional chain along the crystallographic c‐axis. The complex was screened for cytotoxicity against a panel of eight human cancer cell lines, namely MDA‐MB‐231, CAL‐51, K562, HeLa, SGC‐7901, A549, MCF‐7 and SMMC‐7721. The best anticancer activity was obtained with triple‐negative breast cancer CAL‐51 and MDA‐MB‐231 cell lines, with IC50 values in the range 0.035–0.10 μM, and this was better than using carboplatin. The complex inhibits proteasomal chymotrypsin‐like activity, and docking studies reveal its interaction with 20S proteasome. In addition, the complex causes accumulation of ubiquitinated proteins, induces apoptosis and inhibits cell proliferation, indicating its great potential as a novel therapy for triple‐negative breast cancer. 相似文献
94.
Acta Mathematicae Applicatae Sinica, English Series - For the variational inequality with symmetric cone constraints problem, we consider using the inexact modified Newton method to efficiently... 相似文献
95.
96.
Enantioselective Self‐Assembly of Triangular Dy3 Clusters with Single‐Molecule Magnet Behavior
下载免费PDF全文
![点击此处可从《化学:亚洲杂志》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Three pairs of enantiopure chiral triangular Ln3 clusters, [Ln3LRRRRRR/SSSSSS(μ3‐OH)2(H2O)2(SCN)4]?xCH3OH?yH2O ( R ‐Dy3 , Ln=Dy, x=6, y=0; S ‐Dy3 , Ln=Dy, x=6, y=1; R ‐Ho3 , Ln=Ho, x=6, y=1; S ‐Ho3 , Ln=Ho, x=6, y=1; R ‐Er3 , Ln=Er, x=6, y=0; S ‐Er3 , Ln=Er, x=6, y=1), have been successfully synthesized by a rational enantioselective synthetic strategy. The core of triangular Ln3 is bound in the central N6O3 of the macrocyclic ligand, and the coordination spheres of Ln ions are completed by four SCN? anions and two H2O molecules in axial positions of the macrocycle. The circular dichroism (CD) and vibrational circular dichroism (VCD) spectra of the enantiomers demonstrate that the chirality is successfully transferred from the ligands to the resulting Ln3 clusters. Ac susceptibility measurements reveal that single‐molecule magnet behavior occurs for both enantiopure clusters of R ‐Dy3 and S ‐Dy3 . This work is one of the few examples of the successful design of a pair of triangular Dy3 clusters showing simultaneously slow magnetic relaxation and optical activity, and this might open up new opportunities to develop novel multifunctional materials. 相似文献
97.
Jinping Song Hui Li Jianbin Chao Chuan Dong Shaomin Shuang 《Journal of inclusion phenomena and macrocyclic chemistry》2012,72(3-4):389-395
The formation of the inclusion complex of p-sulfonatocalix[6]arene (SCX6) with different forms of vitamin B6 (VB6) was studied by using fluorescence spectroscopy. VB6 can exist in one of three forms (the acidic form, neutral zwitterionic form and basic form) depending on pH. The fluorescence intensities of acidic and basic forms of VB6 remarkably decreased in presence of SCX6. SCX6 preferred to form 1:1 inclusion complexes with acidic and basic forms of VB6 but hardly form inclusion complex with neutral zwitterionic form. According to the nonlinear curve fitting method, the inclusion constant (K) for the formation of inclusion complexes of acidic and basic forms of VB6 with SCX6 were evaluated to be 1.4?×?104 and 9?×?103 L/mol, respectively. The binding affinity of SCX6 towards acidic form is attributed to hydrogen bonds and hydrophobic interaction, furthermore, additional electrostatic interaction also plays a crucial role. The possible inclusion mode was given by 1H NMR technique. 相似文献
98.
99.
Gold‐Catalyzed Tandem Cycloisomerization–Halogenation of Chiral Homopropargyl Sulfonamides
下载免费PDF全文
![点击此处可从《Chemistry (Weinheim an der Bergstrasse, Germany)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Chao Shu Long Li Cang‐Hai Shen Peng‐Peng Ruan Chao‐Yue Liu Prof. Dr. Long‐Wu Ye 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(7):2282-2290
Two new gold‐catalyzed tandem cycloisomerization–halogenation reactions of chiral homopropargyl sulfonamides have been developed. Various enantioenriched 3,3‐diiodopyrrolidin‐2‐ols and 3‐fluoropyrrolidin‐2‐ols were obtained in moderate‐to‐good yields with excellent enantio‐ and diastereoselectivity. 相似文献
100.
Domino Radical Addition/Oxidation Sequence with Photocatalysis: One‐Pot Synthesis of Polysubstituted Furans from α‐Chloro‐Alkyl Ketones and Styrenes
下载免费PDF全文
![点击此处可从《Chemistry (Weinheim an der Bergstrasse, Germany)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Shuang Wang Wen‐Liang Jia Lin Wang Prof. Dr. Qiang Liu Prof. Dr. Li‐Zhu Wu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(39):13794-13798
A new domino reaction has been developed that allows the combination of styrenes and α‐alkyl ketone radicals to afford a wide array of polysubstituted furans in good to excellent yields under mild and simple reaction conditions. The key to success of this novel protocol is the use of photocatalyst fac‐Ir(ppy)3 and oxidant K2S2O8. Mechanistic studies by a radical scavenger and photoluminescence quenching suggest that a radical addition/oxidation pathway is operable. 相似文献