全文获取类型
收费全文 | 3832篇 |
免费 | 107篇 |
国内免费 | 16篇 |
专业分类
化学 | 3116篇 |
晶体学 | 31篇 |
力学 | 38篇 |
数学 | 380篇 |
物理学 | 390篇 |
出版年
2023年 | 19篇 |
2022年 | 90篇 |
2021年 | 95篇 |
2020年 | 58篇 |
2019年 | 57篇 |
2018年 | 44篇 |
2017年 | 46篇 |
2016年 | 109篇 |
2015年 | 95篇 |
2014年 | 119篇 |
2013年 | 213篇 |
2012年 | 210篇 |
2011年 | 250篇 |
2010年 | 142篇 |
2009年 | 143篇 |
2008年 | 260篇 |
2007年 | 207篇 |
2006年 | 217篇 |
2005年 | 205篇 |
2004年 | 165篇 |
2003年 | 134篇 |
2002年 | 134篇 |
2001年 | 61篇 |
2000年 | 40篇 |
1999年 | 49篇 |
1998年 | 37篇 |
1997年 | 43篇 |
1996年 | 47篇 |
1995年 | 44篇 |
1994年 | 38篇 |
1993年 | 30篇 |
1992年 | 32篇 |
1991年 | 27篇 |
1989年 | 23篇 |
1988年 | 19篇 |
1987年 | 16篇 |
1986年 | 14篇 |
1985年 | 22篇 |
1984年 | 21篇 |
1983年 | 16篇 |
1982年 | 31篇 |
1981年 | 28篇 |
1980年 | 30篇 |
1979年 | 22篇 |
1978年 | 18篇 |
1977年 | 17篇 |
1975年 | 13篇 |
1956年 | 19篇 |
1955年 | 37篇 |
1954年 | 57篇 |
排序方式: 共有3955条查询结果,搜索用时 62 毫秒
161.
Expedient and Diastereodivergent Assembly of Terpenoid Decalin Subunits having Quaternary Stereocenters through Organocatalytic Robinson Annulation of Nazarov Reagent 下载免费PDF全文
Barbara Berkes Kristóf Ozsváth Laura Molnár Tamás Gáti Tamás Holczbauer György Kardos Tibor Soós 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(50):18101-18106
We report an expedient approach to highly functionalized cis‐ and trans‐decalines that could function as key structural subunits toward the synthesis of various classes of terpenoids. Key to the strategy is an organocatalyzed Robinson annulation reaction of the Nazarov reagent that affords chiral enone building blocks with high enantioselectivities. The quaternary carbon stereogenic center can direct the subsequent reactions and allow the rapid and diastereoconvergent assembly of complex decalines with contiguous stereocenters. 相似文献
162.
163.
Jelena Vasiljević Samira Hadžić Ivan Jerman Lidija Černe Brigita Tomšič Jožef Medved Matjaž Godec Boris Orel Barbara Simončič 《Polymer Degradation and Stability》2013
The aim of this study was to introduce a non-formaldehyde inorganic–organic hybrid sol–gel flame-retardant precursor (SiOP) containing phosphorous, nitrogen, and silicon and to compare its functional properties with those of the conventional formaldehyde-containing organic flame-retardant agent, organophosphonate (OP). SiOP was used at concentrations of 2%, 4%, and 8%, and OP was used at a concentration of 200 g/dm3. Both agents were applied to 100% cotton (CO) woven fabric by the pad-dry-cure method under the appropriate conditions. The presence of the SiOP and OP coatings on the CO fabric was confirmed by scanning electron microscopy, energy dispersive X-ray spectroscopy and Fourier-transform infrared spectroscopy. The results of the vertical tests of flammability and the thermogravimetric analyses showed that the presence of the SiOP coating changed the thermal degradation pathway of the CO fabric and resulted in an increase in the thermo-oxidative stability of the cellulose fibres. The thermo-oxidative stability was enhanced by the addition of higher amount of dry solids. At comparable dry solids contents, OP preserved significantly greater flame retardancy and thermo-oxidative stability than did SiOP. These results indicated that the SiOP precursor could not act as an effective alternative to the OP agent in the flame-retardant protection of CO fabric. 相似文献
164.
165.
Jóźwiak Grzegorz Majer-Dziedzic Barbara Kwiecińska Justyna Waksmundzka-Hajnos Monika 《平面色谱法杂志一现代薄层色谱法》2017,30(2):126-130
JPC – Journal of Planar Chromatography – Modern TLC - Commercially available hop pellets of different origins were extracted by use of ethanol and water, chromatographed on silica... 相似文献
166.
167.
Daria Goldmann Barbara Zdrazil Daniela Digles Gerhard F. Ecker 《Journal of computer-aided molecular design》2017,31(3):319-328
With the public availability of large data sources such as ChEMBLdb and the Open PHACTS Discovery Platform, retrieval of data sets for certain protein targets of interest with consistent assay conditions is no longer a time consuming process. Especially the use of workflow engines such as KNIME or Pipeline Pilot allows complex queries and enables to simultaneously search for several targets. Data can then directly be used as input to various ligand- and structure-based studies. In this contribution, using in-house projects on P-gp inhibition, transporter selectivity, and TRPV1 modulation we outline how the incorporation of linked life science data in the daily execution of projects allowed to expand our approaches from conventional Hansch analysis to complex, integrated multilayer models. 相似文献
168.
169.
Dr. Azusa Kondoh Dipl.‐Chem. Alexander Arlt Barbara Gabor Prof. Alois Fürstner 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(24):7731-7738
The lichen‐derived glycoconjugate gobienine A is structurally more complex than most glycolipids isolated from higher plants by virtue of the all‐cis substituted γ‐lactone substructure embedded into its macrocyclic frame. A concise entry into this very epimerization‐prone and hence challenging structural motif is presented, which relies on an enantioselective cyanohydrin formation, an intramolecular Blaise reaction, a palladium‐catalyzed alkoxycarbonylation, and a diastereoselective hydrogenation of the tetrasubstituted alkene in the resulting butenolide. This strategy, in combination with ring‐closing olefin metathesis for the formation of the macrocyclic perimeter, allowed the proposed structure of gobienine A ( 1 ) to be formed in high overall yield. The recorded spectral data show that the structure originally attributed to gobienine A is incorrect and that it is not the epimerization‐prone ester site on the butanolide ring that is the locus of misassignment; rather, the discrepancy must be more profound. 相似文献
170.