全文获取类型
收费全文 | 55481篇 |
免费 | 9968篇 |
国内免费 | 1918篇 |
专业分类
化学 | 51955篇 |
晶体学 | 499篇 |
力学 | 2021篇 |
综合类 | 32篇 |
数学 | 4847篇 |
物理学 | 8013篇 |
出版年
2021年 | 437篇 |
2020年 | 1518篇 |
2019年 | 2896篇 |
2018年 | 1436篇 |
2017年 | 1054篇 |
2016年 | 3897篇 |
2015年 | 3819篇 |
2014年 | 3907篇 |
2013年 | 4717篇 |
2012年 | 3654篇 |
2011年 | 2889篇 |
2010年 | 3493篇 |
2009年 | 3446篇 |
2008年 | 2995篇 |
2007年 | 2379篇 |
2006年 | 1957篇 |
2005年 | 2076篇 |
2004年 | 1842篇 |
2003年 | 1770篇 |
2002年 | 2519篇 |
2001年 | 1837篇 |
2000年 | 1630篇 |
1999年 | 658篇 |
1998年 | 309篇 |
1997年 | 282篇 |
1996年 | 254篇 |
1993年 | 263篇 |
1992年 | 267篇 |
1991年 | 271篇 |
1990年 | 288篇 |
1989年 | 272篇 |
1987年 | 250篇 |
1985年 | 289篇 |
1984年 | 298篇 |
1983年 | 265篇 |
1982年 | 282篇 |
1980年 | 285篇 |
1979年 | 309篇 |
1978年 | 357篇 |
1977年 | 372篇 |
1976年 | 424篇 |
1975年 | 378篇 |
1974年 | 401篇 |
1973年 | 403篇 |
1972年 | 371篇 |
1971年 | 332篇 |
1970年 | 319篇 |
1969年 | 300篇 |
1968年 | 259篇 |
1967年 | 250篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
1.
Chuprin A. S. Belova S. A. Bugaenko M. G. Vologzhanina A. V. Loktev A. S. Voloshin Ya. Z. Buznik V. M. Dedov A. G. 《Kinetics and Catalysis》2022,63(1):108-116
Kinetics and Catalysis - A new ruthenium(II) cage complex with polar terminal groups in the apical substituents has been synthesized; the molecular design of the complex contributes to the... 相似文献
2.
Moroz Ya. A. Lozinskyy N. S. Lopanov A. N. Chebyshev K. A. 《Russian Journal of General Chemistry》2022,92(1):101-107
Russian Journal of General Chemistry - Tungstophosphatozincates with the Keggin anion structure Kt5[PW11O39Zn(H2O)]?nH2O, Kt = Rb+, Cs+, (CH3)4N+; (C2H5)4N+ were synthesized. Their... 相似文献
3.
4.
For an integer , a graph is -hamiltonian if for any vertex subset with , is hamiltonian, and is -hamiltonian connected if for any vertex subset with , is hamiltonian connected. Thomassen in 1984 conjectured that every 4-connected line graph is hamiltonian (see Thomassen, 1986), and Ku?zel and Xiong in 2004 conjectured that every 4-connected line graph is hamiltonian connected (see Ryjá?ek and Vrána, 2011). In Broersma and Veldman (1987), Broersma and Veldman raised the characterization problem of -hamiltonian line graphs. In Lai and Shao (2013), it is conjectured that for , a line graph is -hamiltonian if and only if is -connected. In this paper we prove the following.(i) For an integer , the line graph of a claw-free graph is -hamiltonian if and only if is -connected.(ii) The line graph of a claw-free graph is 1-hamiltonian connected if and only if is 4-connected. 相似文献
5.
6.
Chemical versus Electrochemical Synthesis of Carbon Nano‐onion/Polypyrrole Composites for Supercapacitor Electrodes
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)
Olena Mykhailiv Monika Imierska Martyna Petelczyc Prof. Dr. Luis Echegoyen Dr. Marta E. Plonska‐Brzezinska 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(15):5783-5793
The development of high‐surface‐area carbon electrodes with a defined pore size distribution and the incorporation of pseudo‐active materials to optimize the overall capacitance and conductivity without destroying the stability are at present important research areas. Composite electrodes of carbon nano‐onions (CNOs) and polypyrrole (Ppy) were fabricated to improve the specific capacitance of a supercapacitor. The carbon nanostructures were uniformly coated with Ppy by chemical polymerization or by electrochemical potentiostatic deposition to form homogenous composites or bilayers. The materials were characterized by transmission‐ and scanning electron microscopy, differential thermogravimetric analyses, FTIR spectroscopy, piezoelectric microgravimetry, and cyclic voltammetry. The composites show higher mechanical and electrochemical stabilities, with high specific capacitances of up to about 800 F g?1 for the CNOs/SDS/Ppy composites (chemical synthesis) and about 1300 F g?1 for the CNOs/Ppy bilayer (electrochemical deposition). 相似文献
7.
Dr. Sabin Llona‐Minguez Dr. Matthieu Desroses Artin Ghassemian Dr. Sylvain A. Jacques Dr. Lars Eriksson Rebecka Isacksson Tobias Koolmeister Dr. Pål Stenmark Dr. Martin Scobie Prof. Thomas Helleday 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(20):7394-7398
A two‐step synthesis of structurally diverse pyrrole‐containing bicyclic systems is reported. ortho‐Nitro‐haloarenes coupled with vinylic N‐methyliminodiacetic acid (MIDA) boronates generate ortho‐vinyl‐nitroarenes, which undergo a “metal‐free” nitrene insertion, resulting in a new pyrrole ring. This novel synthetic approach has a wide substrate tolerance and it is applicable in the preparation of more complex “drug‐like” molecules. Interestingly, an ortho‐nitro‐allylarene derivative furnished a cyclic β‐aminophosphonate motif. 相似文献
8.
Interactions of Pt‐ttpy with G‐Quadruplexes Originating from Promoter Region of the c‐myc Gene Deciphered by NMR and Gel Electrophoresis Analysis
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)
9.
10.
This study describes the development of a simple, enzyme-free, label-free, sensitive, and selective system for detecting adenosine based on the use of Tween 20-stabilized gold nanoparticles (Tween 20-AuNPs) as an efficient fluorescence quencher for boron dipyrromethene-conjugated adenosine 5′-triphosphate (BODIPY-ATP) and as a recognition element for adenosine. BODIPY-ATP can interact with Tween 20-AuNPs through the coordination between the adenine group of BODIPY-ATP and Au atoms on the NP surface, thereby causing the fluorescence quenching of BODIPY-ATP through the nanometal surface energy transfer (NSET) effect. When adenosine attaches to the NP surface, the attached adenosine exhibits additional electrostatic attraction to BODIPY-ATP. As a result, the presence of adenosine enhances the efficiency of AuNPs in fluorescence quenching of BODIPY-ATP. The AuNP-induced fluorescence quenching of BODIPY-ATP progressively increased with an increase in the concentration of adenosine; the detection limit at a signal-to-noise ratio of 3 for adenosine was determined to be 60 nM. The selectivity of the proposed system was more than 1000-fold for adenosine over any adenosine analogs and other nucleotides. The proposed system combined with a phenylboronic acid-containing column was successfully applied to the determination of adenosine in urine. 相似文献