全文获取类型
收费全文 | 345篇 |
免费 | 29篇 |
专业分类
化学 | 296篇 |
晶体学 | 1篇 |
力学 | 4篇 |
数学 | 30篇 |
物理学 | 43篇 |
出版年
2024年 | 1篇 |
2023年 | 2篇 |
2022年 | 6篇 |
2021年 | 6篇 |
2020年 | 10篇 |
2019年 | 6篇 |
2017年 | 2篇 |
2016年 | 26篇 |
2015年 | 17篇 |
2014年 | 20篇 |
2013年 | 25篇 |
2012年 | 22篇 |
2011年 | 24篇 |
2010年 | 23篇 |
2009年 | 8篇 |
2008年 | 30篇 |
2007年 | 18篇 |
2006年 | 17篇 |
2005年 | 15篇 |
2004年 | 14篇 |
2003年 | 5篇 |
2002年 | 5篇 |
2001年 | 4篇 |
2000年 | 2篇 |
1999年 | 5篇 |
1997年 | 1篇 |
1995年 | 1篇 |
1994年 | 3篇 |
1993年 | 6篇 |
1988年 | 1篇 |
1987年 | 2篇 |
1985年 | 3篇 |
1980年 | 2篇 |
1979年 | 1篇 |
1978年 | 2篇 |
1977年 | 8篇 |
1976年 | 2篇 |
1974年 | 2篇 |
1973年 | 2篇 |
1971年 | 1篇 |
1966年 | 4篇 |
1964年 | 1篇 |
1950年 | 1篇 |
1948年 | 4篇 |
1947年 | 6篇 |
1946年 | 3篇 |
1933年 | 2篇 |
1925年 | 1篇 |
1923年 | 1篇 |
1920年 | 1篇 |
排序方式: 共有374条查询结果,搜索用时 15 毫秒
101.
Li[B(OCH2CF3)4]: Synthesis,Characterization and Electrochemical Application as a Conducting Salt for LiSB Batteries 下载免费PDF全文
Dr. Michael Rohde Dr. Philipp Eiden Verena Leppert Dr. Michael Schmidt Dr. Arnd Garsuch Dr. Guenter Semrau Prof. Dr. Ingo Krossing 《Chemphyschem》2015,16(3):666-675
A new Li salt with views to success in electrolytes is synthesized in excellent yields from lithium borohydride with excess 2,2,2‐trifluorethanol (HOTfe) in toluene and at least two equivalents of 1,2‐dimethoxyethane (DME). The salt Li[B(OTfe)4] is obtained in multigram scale without impurities, as long as DME is present during the reaction. It is characterized by heteronuclear magnetic resonance and vibrational spectroscopy (IR and Raman), has high thermal stability (Tdecomposition>271 °C, DSC) and shows long‐term stability in water. The concentration‐dependent electrical conductivity of Li[B(OTfe)4] is measured in water, acetone, EC/DMC, EC/DMC/DME, ethyl acetate and THF at RT In DME (0.8 mol L ?1) it is 3.9 mS cm?1, which is satisfactory for the use in lithium‐sulfur batteries (LiSB). Cyclic voltammetry confirms the electrochemical stability of Li[B(OTfe)4] in a potential range of 0 to 4.8 V vs. Li/Li+. The performance of Li[B(OTfe)4] as conducting salt in a 0.2 mol L ?1 solution in 1:1 wt % DME/DOL is investigated in LiSB test cells. After the 40th cycle, 86 % of the capacity remains, with a coulombic efficiency of around 97 % for each cycle. This indicates a considerable performance improvement for LiSB, if compared to the standard Li[NTf2]/DOL/DME electrolyte system. 相似文献
102.
103.
104.
105.
106.
107.
Verena Gierz Jascha Melomedov Dr. Christoph Förster Christine Deißler Dr. Frank Rominger Prof. Dr. Doris Kunz Prof. Dr. Katja Heinze 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(34):10677-10688
Coupling of uronium salts with in situ generated N‐heterocyclic carbenes provides straightforward access to symmetrical [ 4 ]2+ and unsymmetrical bis‐imidazolium salts [ 6 ]2+ and [ 9 ]2+. As indicated by cyclic and square‐wave voltammetry, [ 6 ]2+ and [ 9 ]2+ can be (irreversibly) reduced by one electron. The initially formed radicals [ 6 ].+ and [ 9 ].+ undergo further reactions, which were probed by EPR spectroscopy and density functional calculations. The final products of the two‐electron reduction are the two carbenes. Upon irradiation with UV light both [ 6 ]2+ and [ 9 ]2+ emit at room temperature in solution but with dramatically different characteristics. The different fluorescence behavior is analyzed by emission spectroscopy and interpreted by using time‐dependent density functional calculations as largely due to different excited‐state dynamics of [ 6 ]2+ and [ 9 ]2+. The geometries of both radicals [ 6 ].+ and [ 9 ].+ and excited states {[ 6 ]2+} * and {[ 9 ]2+}* are substantially different from those of the parent ground‐state molecules. 相似文献
108.
109.
The reduction of bis(2-hydroxyethyl)disulfide (HEDS) by reduced glutathione (GSH) is the most commonly used assay to analyze the presence and properties of enzymatically active glutaredoxins (Grx), a family of central redox proteins in eukaryotes and glutathione-utilizing prokaryotes. Enzymatically active Grx usually prefer glutathionylated disulfide substrates. These are converted via a ping-pong mechanism. Sequential kinetic patterns for the HEDS assay have therefore been puzzling since 1991. Here we established a novel assay and used the model enzyme ScGrx7 from yeast and PfGrx from Plasmodium falciparum to test several possible causes for the sequential kinetics such as pre-enzymatic GSH depletion, simultaneous binding of a glutathionylated substrate and GSH, as well as substrate or product inhibition. Furthermore, we analyzed the non-enzymatic reaction between HEDS and GSH by HPLC and mass spectrometry suggesting that such a reaction is too slow to explain high Grx activities in the assay. The most plausible interpretation of our results is a direct Grx-catalyzed reduction of HEDS. Physiological implications of this alternative mechanism and of the Grx-catalyzed reduction of non-glutathione disulfide substrates are discussed. 相似文献
110.
Beate Beer Birthe Schubert Anne Oberguggenberger Verena Meraner Michael Hubalek Herbert Oberacher 《Analytical and bioanalytical chemistry》2010,398(4):1791-1800
There is substantial evidence that circulating estrogens promote the proliferation of breast cancer. Consequently, adjuvant
hormonal treatment strategies targeting estrogen action have been established. Such hormonal therapies include selective estrogen
receptor modulators, such as tamoxifen, which interfere at the estrogen receptors directly, or non-steroidal aromatase inhibitors,
such as anastrozole and letrozole, which inhibit estrogen synthesis through blocking the aromatase, a key enzyme of estrogen
production. Despite considerable therapeutic success, in several cases, the use of these drugs is limited by side effects
that have been described to significantly impair the adherence of patients to endocrine treatment. However, objective data
concerning patient adherence and its clinical relevance are limited. One promising approach to check patient-reported adherence
is drug monitoring in human plasma. Therefore, a liquid chromatography–tandem mass spectrometry method to determine the plasma
concentrations of tamoxifen, anastrozole, and letrozole has been developed and fully validated according to guidelines for
clinical and forensic toxicology. The validation criteria evaluated were selectivity, linearity, accuracy and precision, limit
of quantification, recovery and matrix effects, sample stability, and carryover. The six-point calibration curves showed linearity
over the range of concentrations from 25 to 500 ng/ml for tamoxifen, 5 to 200 ng/ml for anastrozole, and 10 to 300 ng/ml for
letrozole. The intra- and inter-day precision and accuracies were always better than 15%. The validated procedure was successfully
applied to a clinical study (Patient-Reported Outcomes in Breast Cancer Patients undergoing Endocrine Therapy, PRO-BETh).
A major aim of PRO-BETh study is the comprehensive evaluation of adherence to treatment in pre- and post-menopausal women
with breast cancer. Plasma samples of 310 breast cancer patients undergoing anti-estrogen therapy were analyzed. Eight samples
did not contain a quantifiable amount of drug, strongly indicating non-adherence of the corresponding patients to adjuvant
breast cancer treatment. Furthermore, plasma concentrations at the lower end of the observed plasma level distribution might
represent a hint but not a confirmation for non-adherence in terms of non-daily and irregular intake of the prescribed drug. 相似文献