全文获取类型
收费全文 | 20668篇 |
免费 | 3587篇 |
国内免费 | 3989篇 |
专业分类
化学 | 16017篇 |
晶体学 | 337篇 |
力学 | 1208篇 |
综合类 | 311篇 |
数学 | 2664篇 |
物理学 | 7707篇 |
出版年
2024年 | 66篇 |
2023年 | 268篇 |
2022年 | 596篇 |
2021年 | 632篇 |
2020年 | 695篇 |
2019年 | 787篇 |
2018年 | 646篇 |
2017年 | 684篇 |
2016年 | 900篇 |
2015年 | 992篇 |
2014年 | 1206篇 |
2013年 | 1555篇 |
2012年 | 1721篇 |
2011年 | 1807篇 |
2010年 | 1537篇 |
2009年 | 1449篇 |
2008年 | 1701篇 |
2007年 | 1505篇 |
2006年 | 1351篇 |
2005年 | 1121篇 |
2004年 | 913篇 |
2003年 | 809篇 |
2002年 | 985篇 |
2001年 | 867篇 |
2000年 | 685篇 |
1999年 | 515篇 |
1998年 | 343篇 |
1997年 | 247篇 |
1996年 | 290篇 |
1995年 | 228篇 |
1994年 | 156篇 |
1993年 | 158篇 |
1992年 | 132篇 |
1991年 | 131篇 |
1990年 | 97篇 |
1989年 | 95篇 |
1988年 | 59篇 |
1987年 | 59篇 |
1986年 | 50篇 |
1985年 | 35篇 |
1984年 | 35篇 |
1983年 | 34篇 |
1982年 | 22篇 |
1981年 | 16篇 |
1980年 | 9篇 |
1979年 | 12篇 |
1978年 | 7篇 |
1972年 | 4篇 |
1971年 | 5篇 |
1936年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
JPC – Journal of Planar Chromatography – Modern TLC - A new high-performance thin-layer chromatographic (HPTLC) method has been developed for the simultaneous estimation of... 相似文献
2.
3.
4.
Single Crystal to Single Crystal (SC‐to‐SC) Transformation from a Nonporous to Porous Metal–Organic Framework and Its Application Potential in Gas Adsorption and Suzuki Coupling Reaction through Postmodification
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)
Dr. Rupam Sen Debraj Saha Dr. Subratanath Koner Dr. Paula Brandão Dr. Zhi Lin 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(15):5962-5971
A new amino‐functionalized strontium–carboxylate‐based metal–organic framework (MOF) has been synthesized that undergoes single crystal to single crystal (SC‐to‐SC) transformation upon desolvation. Both structures have been characterized by single‐crystal X‐ray analysis. The desolvated structure shows an interesting 3D porous structure with pendent ?NH2 groups inside the pore wall, whereas the solvated compound possesses a nonporous structure with DMF molecules on the metal centers. The amino group was postmodified through Schiff base condensation by pyridine‐2‐carboxaldehyde and palladium was anchored on that site. The modified framework has been utilized for the Suzuki cross‐coupling reaction. The compound shows high activity towards the C?C cross‐coupling reaction with good yields and turnover frequencies. Gas adsorption studies showed that the desolvated compound had permanent porosity and was microporous in nature with a BET surface area of 2052 m2 g?1. The material also possesses good CO2 (8 wt %) and H2 (1.87 wt %) adsorption capabilities. 相似文献
5.
Synthesis and Photophysical Properties of a Sc3N@C80‐Corrole Electron Donor–Acceptor Conjugate
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)
Bin Liu Hongyun Fang Prof. Xiaofang Li Wenting Cai Lipiao Bao Marc Rudolf Fabian Plass Prof. Louzhen Fan Prof. Xing Lu Prof. Dirk M. Guldi 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(2):746-752
Embedding endohdedral metallofullerenes (EMFs) into electron donor–acceptor systems is still a challenging task owing to their limited quantities and their still largely unexplored chemical properties. In this study, we have performed a 1,3‐dipolar cycloaddition reaction of a corrole‐based precursor with Sc3N@C80 to regioselectively form a [5,6]‐adduct ( 1 ). The successful attachment of the corrole moiety was confirmed by mass spectrometry. In the electronic ground state, absorption spectra suggest sizeable electronic communications between the electron acceptor and the electron donor. Moreover, the addition pattern occurring at a [5,6]‐bond junction is firmly proven by NMR spectroscopy and electrochemical investigations performed with 1 . In the electronically excited state, which is probed in photophysical assays with 1 , a fast electron‐transfer yields the radical ion pair state consisting of the one‐electron‐reduced Sc3N@C80 and of the one‐electron‐oxidized corrole upon its exclusive photoexcitation. As such, our results shed new light on the practical work utilizing EMFs as building blocks in photovoltaics. 相似文献
6.
针对星模拟器与星敏感器观星的色温不匹配对星敏感器光信号定标精度产生的影响,设计了一种基于LED的多色温多星等单星模拟器,采用该系统模拟特定色温的星光用于星敏感器光信号定标,大幅降低了色温非匹配带来的定标误差。从理论上分析了色温非匹配影响星敏感器光信号的定标精度的机理;根据设计指标确定了星模拟器的设计方案,主要解决了光源的选型、多色温多星等单星模拟器驱动和控制系统、色温星等匹配算法、多色温多星等单星模拟器软件设计四项关键技术问题;对多色温多星等单星模拟器进行了标定和性能测试:0等星4000K和3等星7000 K星光的光谱匹配误差分别为4.87%和7.83%,星等等级分别为0.03和2.93;光源稳定后,多色温多星等单星模拟器的平行光管出口Φ100 mm口径内的照度非均匀度为6.5%,均满足设计指标。 相似文献
7.
Polypyrrole Shell@3D‐Ni Metal Core Structured Electrodes for High‐Performance Supercapacitors
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)
Gao‐Feng Chen Yu‐Zhi Su Pan‐Yong Kuang Zhao‐Qing Liu Dao‐Yi Chen Xu Wu Nan Li Prof. Shi‐Zhang Qiao 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(12):4614-4621
Three‐dimensional (3D) nanometal films serving as current collectors have attracted much interest recently owing to their promising application in high‐performance supercapacitors. In the process of the electrochemical reaction, the 3D structure can provide a short diffusion path for fast ion transport, and the highly conductive nanometal may serve as a backbone for facile electron transfer. In this work, a novel polypyrrole (PPy) shell@3D‐Ni‐core composite is developed to enhance the electrochemical performance of conventional PPy. With the introduction of a Ni metal core, the as‐prepared material exhibits a high specific capacitance (726 F g?1 at a charge/discharge rate of 1 A g?1), good rate capability (a decay of 33 % in Csp with charge/discharge rates increasing from 1 to 20 A g?1), and high cycle stability (only a small decrease of 4.2 % in Csp after 1000 cycles at a scan rate of 100 mV s?1). Furthermore, an aqueous symmetric supercapacitor device is fabricated by using the as‐prepared composite as electrodes; the device demonstrates a high energy density (≈21.2 Wh kg?1) and superior long‐term cycle ability (only 4.4 % and 18.6 % loss in Csp after 2000 and 5000 cycles, respectively). 相似文献
8.
9.
10.
Mathematical Notes - Let $$\mathbb N$$ denote the set of all nonnegative integers, and let $$A\subseteq\mathbb N$$ . Let $$h,n\in\mathbb N$$ , $$h\ge 2$$ and $$r_h(A,n)=\#\{(a_1,\dots,a_h)\in... 相似文献