全文获取类型
收费全文 | 1174篇 |
免费 | 140篇 |
国内免费 | 120篇 |
专业分类
化学 | 944篇 |
晶体学 | 40篇 |
力学 | 48篇 |
综合类 | 4篇 |
数学 | 145篇 |
物理学 | 253篇 |
出版年
2023年 | 12篇 |
2022年 | 21篇 |
2021年 | 28篇 |
2020年 | 17篇 |
2019年 | 31篇 |
2018年 | 21篇 |
2017年 | 25篇 |
2016年 | 50篇 |
2015年 | 56篇 |
2014年 | 62篇 |
2013年 | 86篇 |
2012年 | 81篇 |
2011年 | 92篇 |
2010年 | 48篇 |
2009年 | 40篇 |
2008年 | 76篇 |
2007年 | 58篇 |
2006年 | 60篇 |
2005年 | 49篇 |
2004年 | 56篇 |
2003年 | 44篇 |
2002年 | 61篇 |
2001年 | 47篇 |
2000年 | 30篇 |
1999年 | 28篇 |
1998年 | 22篇 |
1997年 | 12篇 |
1996年 | 15篇 |
1995年 | 11篇 |
1994年 | 17篇 |
1993年 | 16篇 |
1992年 | 12篇 |
1991年 | 8篇 |
1990年 | 14篇 |
1989年 | 7篇 |
1988年 | 4篇 |
1987年 | 7篇 |
1986年 | 5篇 |
1985年 | 8篇 |
1984年 | 10篇 |
1982年 | 15篇 |
1981年 | 9篇 |
1979年 | 8篇 |
1978年 | 4篇 |
1976年 | 4篇 |
1974年 | 7篇 |
1971年 | 6篇 |
1970年 | 4篇 |
1968年 | 4篇 |
1967年 | 4篇 |
排序方式: 共有1434条查询结果,搜索用时 15 毫秒
941.
Control of the Transition between Ni‐C and Ni‐SIa States by the Redox State of the Proximal FeS Cluster in the Catalytic Cycle of [NiFe] Hydrogenase
下载免费PDF全文
![点击此处可从《Angewandte Chemie (International ed. in English)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Dr. Hulin Tai Dr. Koji Nishikawa Dr. Masayuki Suzuki Prof. Dr. Yoshiki Higuchi Prof. Dr. Shun Hirota 《Angewandte Chemie (International ed. in English)》2014,53(50):13817-13820
[NiFe] hydrogenase catalyzes the reversible cleavage of H2. The electrons produced by the H2 cleavage pass through three Fe–S clusters in [NiFe] hydrogenase to its redox partner. It has been reported that the Ni‐SIa, Ni‐C, and Ni‐R states of [NiFe] hydrogenase are involved in the catalytic cycle, although the mechanism and regulation of the transition between the Ni‐C and Ni‐SIa states remain unrevealed. In this study, the FT‐IR spectra under light irradiation at 138–198 K show that the Ni‐L state of [NiFe] hydrogenase is an intermediate between the transition of the Ni‐C and Ni‐SIa states. The transition of the Ni‐C state to the Ni‐SIa state occurred when the proximal [Fe4S4]p2+/+ cluster was oxidized, but not when it was reduced. These results show that the catalytic cycle of [NiFe] hydrogenase is controlled by the redox state of its [Fe4S4]p2+/+ cluster, which may function as a gate for the electron flow from the NiFe active site to the redox partner. 相似文献
942.
Identification and characterization of the process‐related impurities in fasudil hydrochloride by hyphenated techniques using a quality by design approach
下载免费PDF全文
![点击此处可从《Journal of separation science》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Following the underlying principles of quality by design mentioned in the ICH Q8 guidance, systematic approaches for the control of process‐related impurities have been taken in the manufacturing process of fasudil hydrochloride, a potent Rho‐kinase inhibitor and vasodilator. Three related impurities were found in fasudil hydrochloride lab samples by a newly developed RP‐HPLC with volatile mobile phase gradient elution and UV detection method. The elemental compositions of the impurities were determined by positive ESI high‐resolution TOF‐MS analysis of their [M + H]+ ions and their structures were identified through the elucidation of the product mass spectra obtained by a triple quadrupole mass spectrometer. The key impurity was further verified through synthesis and organic spectroscopy including NMR and IR spectroscopy. The origins of these impurities were located and the effective approaches to eliminate them were proposed based on the redesign of the synthetic conditions. The results obtained are important for quality control in the manufacture of fasudil hydrochloride bulk drug substance and injection. 相似文献
943.
Double Metal Ions Competitively Control the Guest‐Sensing Process: A Facile Approach to Stimuli‐Responsive Supramolecular Gels
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. Qi Lin Bin Sun Qing‐Ping Yang Yong‐Peng Fu Xin Zhu Prof. Tai‐Bao Wei Prof. You‐Ming Zhang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(36):11457-11462
A facile approach to the design of stimuli‐responsive supramolecular gels (SRSGs) termed double‐metal‐ion competitive coordination control is reported. By this means, the fluorescence signals and guest‐selective responsiveness of the SRSGs are controlled by the competitive coordination of two different metal ions with the gelators and the target guest. To demonstrate this approach, a gelator G2 based on multiple self‐assembly driving forces was synthesized. G2 could form Ca2+‐coordinated metallogel CaG with strong aggregation‐induced emission (AIE). Doping of CaG with Cu2+ results in AIE quenching of CaG and formation of Ca2+‐ and Cu2+‐based metallogel CaCuG. CaCuG could fluorescently detect CN? with specific selectivity through the competitive coordination of CN? with the Cu2+ and the coordination of Ca2+ with G2 again. This approach may open up routes to novel stimuli‐responsive supramolecular materials. 相似文献
944.
Improved conditions for periodate/Schiff's base‐based fluorescent staining of glycoproteins with dansylhydrazine in SDS‐PAGE
下载免费PDF全文
![点击此处可从《Electrophoresis》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Xuan Zhou Guo‐Ying Hong Bin‐Bin Huang Yuan‐Meng Duan Jia‐Yi Shen Mao‐Wei Ni Wei‐Tao Cong Li‐Tai Jin 《Electrophoresis》2014,35(10):1439-1447
An improved periodate/Schiff's base based fluorescent stain with dansylhydrazine (DH) for glycoproteins in 1D and 2D SDS‐PAGE was described. Down to 4–8 ng of glycoproteins can be selectively detected within 2 h, which is approximately 16‐fold higher than that of original protocol, but similar to that of Pro‐Q Emerald 488 stain (Invitrogen, Carlsbad, USA). Furthermore, subsequent study of deglycosylation, glycoprotein affinity isolation, and LC‐MS/MS analysis were performed to confirm the specificity of the improved method. As a result, improved DH stain may provide a new choice for selective, economic, MS compatible, and convenient visualization of gel‐separated glycoproteins. 相似文献
945.
Three biflavonoid glycosides, named carinoside B, C and D (1, 2 and 3, respectively), were isolated from the n-BuOH crude extract of the aerial part of Lomatogonium carinthiacum (Wulfen) Rchb (L. carinthiacum). The structures of 1, 2 and 3 were elucidated by spectroscopic methods, including UV, IR, HR-ESI-MS and extensive 1D and 2D NMR techniques. 相似文献
946.
947.
Halogen Bonding to Amplify Luminescence: A Case Study Using a Platinum Cyclometalated Complex
下载免费PDF全文
![点击此处可从《Angewandte Chemie (International ed. in English)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Vasily V. Sivchik Anastasia I. Solomatina Yi‐Ting Chen Prof. Antti J. Karttunen Prof. Sergey P. Tunik Prof. Pi‐Tai Chou Prof. Igor O. Koshevoy 《Angewandte Chemie (International ed. in English)》2015,54(47):14057-14060
The cocrystallization of a weakly luminescent platinum complex [Pt(btpy)(PPh3)Cl] ( 1 ) (Hbtpy=2‐(2benzothienyl)pyridine; emission quantum yield Φem=0.03) with fluorinated bromo‐ and iodoarenes C6F6‐nXn (X=Br, I; n=1, 2) results in the formation of efficient halogen‐bonding (XB) interactions Pt? Cl???X? R. An up to 22‐fold enhancement (Φem=0.65) in the luminescence intensity of the cocrystallized compound is detected, without a substantial change of the emission energy. Based on crystallographic, photophysical, and theoretical investigations, the contribution of the XB donors C6F6‐nXn to the amplification of luminescence intensity is attributed to the enhancement of spin–orbit coupling through the heavy‐atom effect, and simultaneously to the suppression of the nonradiative relaxation pathways by increasing the rigidity of the chromophore center. 相似文献
948.
从极化团簇的随机涨落出发, 利用维纳过程模型, 推导了铁电体中极化长程涨落的弛豫规律以及光强自相关函数所可能的表现形式. 阐述了微观极化团簇的弛豫过程与宏观测量弛豫规律之间的联系. 通过对原有氦氖激光光子关联谱实验装置进行改进, 观测了BaTiO3和0.71Pb(Mg1/3Nb2/3)O3-0.29PbTiO3单晶中极化团簇长程涨落在居里点和立方到四方相变点附近的弛豫过程. 在BaTiO3中发现极化团簇长程涨落在居里点之上4 K存在双弛豫现象, 此现象与其有序无序相变机理相联系. 在Pb(Mg1/3Nb2/3)O3-0.29PbTiO3中发现极化团簇长程涨落在相变点两侧都存在双弛豫现象. 利用推导的理论结果很好地拟合了实验结果并提取了极化团簇长程涨落的弛豫时间. 两种样品中极化团簇长程涨落的弛豫时间都在相变点出现突变, 并呈现临界慢化现象. 相似文献
949.
950.
A novel synthetic route for LiFePO_4/C cathode materials by addition of starch for lithium-ion batteries 总被引:1,自引:0,他引:1
Shao Hua Luo Zi Long Tang Jun Biao Lu Zhong Tai Zhang State Key Laboratory of New Ceramics Fine Processing Department of Materials Science Engineering Tsinghua University Beijing China Graduate School at Shenzhen Tsinghua University Shenzhen China 《中国化学快报》2007,18(2):237-240
LiFePO4/Carbon composite cathode material was prepared using starch as carbon source by spray-pelleting and subsequent pyrolysis in N2. The samples were characterized by XRD, SEM, Raman, and their electrochemical performance was investigated in terms of cycling behavior. There has a special micro-morphology via the process, which is favorable to electrochemical properties. The discharge capacity of the LiFePO4.C composite was 170 mAh g-1, equal to the theoretical specific capacity at 0.1 C rate. At 4 C current density, the specific capacity was about 80 mAh g-1, which can satisfy for transportation applications if having a more flat discharge flat. 相似文献