全文获取类型
收费全文 | 2598篇 |
免费 | 86篇 |
国内免费 | 2篇 |
专业分类
化学 | 1824篇 |
晶体学 | 11篇 |
力学 | 28篇 |
数学 | 207篇 |
物理学 | 616篇 |
出版年
2023年 | 19篇 |
2022年 | 12篇 |
2021年 | 32篇 |
2020年 | 33篇 |
2019年 | 28篇 |
2018年 | 17篇 |
2017年 | 18篇 |
2016年 | 67篇 |
2015年 | 81篇 |
2014年 | 69篇 |
2013年 | 126篇 |
2012年 | 145篇 |
2011年 | 148篇 |
2010年 | 112篇 |
2009年 | 98篇 |
2008年 | 140篇 |
2007年 | 114篇 |
2006年 | 99篇 |
2005年 | 101篇 |
2004年 | 82篇 |
2003年 | 69篇 |
2002年 | 60篇 |
2001年 | 43篇 |
2000年 | 62篇 |
1999年 | 40篇 |
1998年 | 51篇 |
1997年 | 36篇 |
1996年 | 45篇 |
1995年 | 31篇 |
1994年 | 38篇 |
1993年 | 45篇 |
1992年 | 30篇 |
1991年 | 20篇 |
1990年 | 19篇 |
1989年 | 17篇 |
1988年 | 20篇 |
1987年 | 21篇 |
1986年 | 19篇 |
1985年 | 28篇 |
1984年 | 36篇 |
1983年 | 17篇 |
1982年 | 25篇 |
1981年 | 16篇 |
1980年 | 29篇 |
1979年 | 21篇 |
1978年 | 22篇 |
1977年 | 35篇 |
1976年 | 15篇 |
1974年 | 23篇 |
1968年 | 13篇 |
排序方式: 共有2686条查询结果,搜索用时 281 毫秒
91.
Michael I. Bruce Michael Schulz Brian W. Skelton Allan H. White 《Journal of Cluster Science》2000,11(1):79-86
Addition of aqueous HCl to Ru5(
3-C=CH2)(-SMe)2(-PPh2)2(CO)10 afforded the structurally characterized carbyne complex Ru5(
3-SMe)(
3-CMe)(-Cl)(-SMe)(-PPh2)2(CO)9, formed by addition of H to the vinylidene ligand; a Cl atom bridges an Ru–Ru bond. 相似文献
92.
93.
Zhenhui Qi Dr. Changzhu Wu Dr. Paula Malo de Molina Han Sun Andrea Schulz Prof. Christian Griesinger Prof. Michael Gradzielski Prof. Rainer Haag Prof. Marion B. Ansorge‐Schumacher Prof. Christoph A. Schalley 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(31):10150-10159
A new and versatile, crown ether appended, chiral supergelator has been designed and synthesized based on the bis‐urea motif. The introduction of a stereogenic center improved its gelation ability significantly relative to its achiral analogue. This low‐molecular‐weight gelator forms supramolecular gels in a variety of organic solvents. It is sensitive to multiple chemical stimuli and the sol–gel phase transitions can be reversibly triggered by host–guest interactions. The gel can be used to trap enzymes and release them on demand by chemical stimuli. It stabilizes the microparticles in Pickering emulsions so that enzyme‐catalyzed organic reactions can take place in the polar phase inside the microparticles, the organic reactants diffusing through the biphasic interface from the surrounding organic phase. Because of the higher interface area between the organic and polar phases, enzyme activity is enhanced in comparison with simple biphasic systems. 相似文献
94.
A. Katrin Krieg 《Analytical and bioanalytical chemistry》2013,405(20):6387-6388
95.
A chemical reaction mechanism was developed for the formation of iron oxide (Fe2O3) from iron pentacarbonyl (Fe(CO)5) in a low‐pressure hydrogen–oxygen flame reactor. In this paper, we describe an extensive approach for the flame‐precursor chemistry and the development of a novel model for the formation of Fe2O3 from the gas phase. The detailed reaction mechanism is reduced for the implementation in two‐dimensional, reacting flow simulations. The comprehensive simulation approach is completed by a model for the formation and growth of the iron oxide nanoparticles. The exhaustive and compact reaction mechanism is validated using experimental data from iron‐atom laser‐induced fluorescence imaging. The particle formation and growth model are verified with new measurements from particle mass spectrometry. 相似文献
96.
Olesya V. Zillich Ute Schweiggert‐Weisz Katrin Hasenkopf Peter Eisner Martina Kerscher 《Biomedical chromatography : BMC》2013,27(11):1444-1451
Permeation of polyphenols through the stratum corneum barrier is a precondition for the protective action of polyphenols against oxidative skin damage. Prior to in vitro skin permeation experiments, we developed a method for the quantification of polyphenols in pig skin, including organic solvent extraction and HPLC analysis. Catechine hydrate, epigallocatechin gallate, trans‐resveratrol, quercetin, rutin and protocatechuic acid were chosen for this study as representatives of phenolics with different lipophilicity and molecular weight. The antioxidative activities of polyphenols as well as their octanol–water partition coefficients at different pH values were determined. Extraction of polyphenols from pig skin was optimized by variation of solvent composition, homogenization intensity and time, as well as partial exclusion of oxygen during extraction. The highest recovery rates could be reached by extraction with the methanol–water mixture (90:10, v/v), containing 0.2 g/L l ‐ascorbic acid, after the cryo‐milling for 4 min. Recoveries of 72% for total phenolics, 96% for quercetin and protocatechuic acid, 90% for rutin and 74% for trans‐resveratrol, were achieved. These extraction parameters will be selected for the polyphenol extraction from pig skin for further in vitro drug permeation studies. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
97.
Mariam Abd El Sater Dr. Mohamed Mellah Dr. Diana Dragoe Emilie Kolodziej Dr. Nada Jaber Dr. Emmanuelle Schulz 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(36):9454-9460
The first immobilization of a pyrene-tagged chromium salen complex through π-π noncovalent interactions on reduced graphene oxide (rGO) is described. A very robust supported catalytic system is obtained to promote asymmetric catalysis in repeated cycles, without loss of activity or enantioselectivity. This specific behavior was demonstrated in two different catalytic reactions (up to ten reuses) promoted by chromium salen complexes, the cyclohexene oxide ring-opening reaction and the hetero-Diels-Alder cycloaddition between various aldehydes and Danishefsky's diene. Furthermore, the chiral chromium salen@rGO has been found to be compatible with a multi-substrate type use, in which the structure of the substrate involved is modified each time the catalyst is reused. 相似文献
98.
Prof. Dr. Axel Schulz Dr. Alexander Villinger 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(6):2032-2038
Pure, solvent‐free Zn(N3)2 was prepared by reaction of diethyl zinc and hydrazoic acid in aprotic solvents. The single‐crystal structure determination, along with the comprehensive characterization of α‐Zn(N3)2 and two metastable polymorphs, could be achieved for the first time. Since these data disagree in large parts with the known, previously reported values, all previous syntheses of Zn(N3)2, and for comparison Zn(N3)2?2.5 H2O and Zn(OH)N3 were reinvestigated, indicating that some of the earlier work has to be revised. 相似文献
99.
Inside Back Cover: Synthesis and Isolation of the Titanium–Scandium Endohedral Fullerenes—Sc2TiC@Ih‐C80, Sc2TiC@D5h‐C80 and Sc2TiC2@Ih‐C80: Metal Size Tuning of the TiIV/TiIII Redox Potentials (Chem. Eur. J. 37/2016) 下载免费PDF全文
100.