全文获取类型
收费全文 | 43042篇 |
免费 | 10960篇 |
国内免费 | 2790篇 |
专业分类
化学 | 46262篇 |
晶体学 | 458篇 |
力学 | 1062篇 |
综合类 | 97篇 |
数学 | 3202篇 |
物理学 | 5711篇 |
出版年
2024年 | 20篇 |
2023年 | 165篇 |
2022年 | 220篇 |
2021年 | 469篇 |
2020年 | 1510篇 |
2019年 | 2849篇 |
2018年 | 1305篇 |
2017年 | 917篇 |
2016年 | 3705篇 |
2015年 | 3889篇 |
2014年 | 3878篇 |
2013年 | 4607篇 |
2012年 | 3695篇 |
2011年 | 2932篇 |
2010年 | 3383篇 |
2009年 | 3368篇 |
2008年 | 2908篇 |
2007年 | 2217篇 |
2006年 | 1847篇 |
2005年 | 1975篇 |
2004年 | 1738篇 |
2003年 | 1613篇 |
2002年 | 2411篇 |
2001年 | 1726篇 |
2000年 | 1502篇 |
1999年 | 562篇 |
1998年 | 225篇 |
1997年 | 168篇 |
1996年 | 131篇 |
1995年 | 119篇 |
1994年 | 95篇 |
1993年 | 94篇 |
1992年 | 68篇 |
1991年 | 73篇 |
1990年 | 42篇 |
1989年 | 34篇 |
1988年 | 32篇 |
1987年 | 25篇 |
1986年 | 20篇 |
1985年 | 30篇 |
1984年 | 28篇 |
1983年 | 21篇 |
1982年 | 16篇 |
1981年 | 17篇 |
1980年 | 18篇 |
1979年 | 18篇 |
1978年 | 14篇 |
1976年 | 15篇 |
1975年 | 11篇 |
1973年 | 11篇 |
排序方式: 共有10000条查询结果,搜索用时 667 毫秒
1.
Yang T. L. Kao C. L. Kuo C. E. Yeh H. C. Li W. J. Li H. T. Chen C. Y. 《Chemistry of Natural Compounds》2022,58(5):825-827
Chemistry of Natural Compounds - A novel bibenzyl derivative, hydrangchinenin (1), was isolated from the stems of Hydrangea chinensis Maxim. (Hydrangeaceae). Its structure was determined on the... 相似文献
2.
Let p ∈ [1, ∞), q ∈ [1, ∞), α∈ R, and s be a non-negative integer. Inspired by the space JNp introduced by John and Nirenberg(1961) and the space B introduced by Bourgain et al.(2015), we introduce a special John-Nirenberg-Campanato space JNcon(p,q,s) over Rn or a given cube of R;with finite side length via congruent subcubes, which are of some amalgam features. The limit space of such spaces as p →∞ is just the Campanato space which coincides with the space BMO(the space of functions with bounded mean oscillations)when α = 0. Moreover, a vanishing subspace of this new space is introduced, and its equivalent characterization is established as well, which is a counterpart of the known characterization for the classical space VMO(the space of functions with vanishing mean oscillations) over Rn or a given cube of Rn with finite side length.Furthermore, some VMO-H1-BMO-type results for this new space are also obtained, which are based on the aforementioned vanishing subspaces and the Hardy-type space defined via congruent cubes in this article. The geometrical properties of both the Euclidean space via its dyadic system and congruent cubes play a key role in the proofs of all these results. 相似文献
3.
Zeng Qing-Wei Wen Zhuo-Yu Fu Jun-Feng Zhou Nan-Run 《International Journal of Theoretical Physics》2021,60(9):3306-3333
International Journal of Theoretical Physics - A new quantum watermark algorithm is presented by combining maximum pixel difference partitioning with the least significant bit substitution... 相似文献
4.
5.
We experimentally analyze the heat capacity and thermal expansion of reference solids in a wide temperature range from several Kelvin to melting temperature,and establish a universal double-linear relation between the experimental heat capacity Cp and thermal expansion β,which is different from the previous models.The universal behavior between heat capacity and thermal expansion is important to predict the thermodynamic parameters at constant pressure,and is helpful for understanding the nature of thermal properties in solids. 相似文献
6.
7.
Chemical versus Electrochemical Synthesis of Carbon Nano‐onion/Polypyrrole Composites for Supercapacitor Electrodes 下载免费PDF全文
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
8.
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
9.
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
10.
Pd0‐Catalyzed Intramolecular α‐Arylation of Sulfones: Domino Reactions in the Synthesis of Functionalized Tetrahydroisoquinolines 下载免费PDF全文
Prof.Dr. Daniel Solé Ferran Pérez‐Janer Dr. Raffaella Mancuso 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(12):4580-4584
A new strategy for the synthesis of tetrahydroisoquinolines based on the Pd0‐catalyzed intramolecular α‐arylation of sulfones is reported. The combination of this Pd‐catalyzed reaction with intermolecular Michael and aza‐Michael reactions allows the development of two‐ and three‐step domino processes to synthesize diversely functionalized scaffolds from readily available starting materials. 相似文献