全文获取类型
收费全文 | 734篇 |
免费 | 40篇 |
国内免费 | 6篇 |
专业分类
化学 | 597篇 |
晶体学 | 8篇 |
力学 | 6篇 |
数学 | 34篇 |
物理学 | 135篇 |
出版年
2023年 | 6篇 |
2022年 | 3篇 |
2021年 | 11篇 |
2020年 | 9篇 |
2019年 | 23篇 |
2018年 | 11篇 |
2017年 | 6篇 |
2016年 | 20篇 |
2015年 | 12篇 |
2014年 | 19篇 |
2013年 | 36篇 |
2012年 | 42篇 |
2011年 | 42篇 |
2010年 | 19篇 |
2009年 | 20篇 |
2008年 | 43篇 |
2007年 | 47篇 |
2006年 | 47篇 |
2005年 | 43篇 |
2004年 | 35篇 |
2003年 | 39篇 |
2002年 | 24篇 |
2001年 | 17篇 |
2000年 | 12篇 |
1999年 | 10篇 |
1998年 | 13篇 |
1997年 | 10篇 |
1996年 | 15篇 |
1995年 | 6篇 |
1994年 | 13篇 |
1993年 | 9篇 |
1992年 | 14篇 |
1991年 | 3篇 |
1990年 | 3篇 |
1989年 | 3篇 |
1988年 | 8篇 |
1987年 | 9篇 |
1986年 | 6篇 |
1985年 | 6篇 |
1984年 | 10篇 |
1983年 | 7篇 |
1982年 | 5篇 |
1981年 | 10篇 |
1980年 | 5篇 |
1979年 | 5篇 |
1978年 | 4篇 |
1977年 | 4篇 |
1976年 | 3篇 |
1973年 | 3篇 |
1969年 | 3篇 |
排序方式: 共有780条查询结果,搜索用时 46 毫秒
121.
Sumio Kato Takuya Yoshizawa Nobuhiro Kakuta Shinya Akiyama Masataka Ogasawara Takashi Wakabayashi Yuunosuke Nakahara Shinichi Nakata 《Research on Chemical Intermediates》2008,34(8-9):703-708
Apatite-type silicate supported precious metal catalysts were prepared and investigated for their catalytic activity in selective catalytic NO reduction. Single-phase La9.33Si6O26 and La8.33ASi6O25.5 (A=Ca, Sr, Ba) were obtained by a sol-gel method. Pd/La9.33Si6O26 catalyst exhibited high activity for oxidation of C3H6, comparable to Pd/Al2O3 catalyst, although the specific surface area of La9.33Si6O26 was lower than that of Al2O3. In addition, Pt/La9.33Si6O26 catalyst exhibited higher activity for selective catalytic reduction of NO than Pt/Al2O3 catalyst. Substitution of Ba2+ for La3+ of La9.33Si6O26 led to increased catalytic activity at low temperature. 相似文献
122.
123.
Hayasaka T Goto-Inoue N Sugiura Y Zaima N Nakanishi H Ohishi K Nakanishi S Naito T Taguchi R Setou M 《Rapid communications in mass spectrometry : RCM》2008,22(21):3415-3426
We recently developed a matrix-assisted laser desorption/ionization quadrupole ion trap time-of-flight (MALDI-QIT-TOF)-based imaging mass spectrometry (IMS) system. This system enables us to perform structural analyses using tandem mass spectrometry (MS/MS), as well as to visualize phospholipids and peptides in frozen sections. In the retina, phototransduction is regulated by the light-sensitive interaction between visual pigment-coupled receptor proteins, such as rhodopsin, and G proteins, such as transducin. There are some reports that the conformation of rhodopsin is influenced by the composition of phospholipids in the lipid bilayer membrane. However, these results were based on in vitro experiments and have not been analyzed in vivo. In this study, we visualized and identified phospholipids in mouse retinal sections with the MALDI-QIT-TOF-based IMS system. From a spectrum obtained by raster-scanned analysis of the sections, ions with high signal intensities were selected and analyzed by MS/MS. As a result, sixteen ions were identified as being from four diacyl-phosphatidylcholine (PC) species, i.e., PC (16:0/16:0), PC (16:0/18:1), PC (16:0/22:6), and PC (18:0/22:6), with different ion forms. The ion images revealed different distributions on the retinal sections: PC (16:0/18:1) was distributed in the inner nuclear layer and outer plexiform layer, PC (16:0/16:0) in the outer nuclear layer and inner segment, and both PC (16:0/22:6) and PC (18:0/22:6) in the outer segment and pigment epithelium. In conclusion, our in vivo IMS analyses demonstrated a three-zone distribution of PC species on the retinal sections. This approach may be useful for analyzing lipid changes and their contribution to phototransduction in the retina. 相似文献
124.
Yamamoto M Yamada M Nonaka N Fukushima S Yasuda M Seki M 《Journal of the American Chemical Society》2008,130(43):14044-14045
This paper describes a facile technique to pattern reactive microdomains inside polydimethylsiloxane microchannels by utilizing polymer particles as the carrier of functional groups. The air/liquid interface formed in microchannels equipped with microwells exerts lateral force on the particles, trapping particles only inside the wells. We then fix the polymer matrix on the wells by melting the trapped particles to form reactive domains with flexible shapes and high resolution. We employed monodisperse poly(styrene-co-glycidyl methacrylate) microparticles having an epoxy group and patterned various types of microdomains with a resolution of several micrometers. Several tests confirmed the presence of the epoxy group and the flatness of the patterned domain. The presented scheme provides a new way of preparing highly functional microsystems by using simple operations and would be useful for various applications, including local patterning of graft polymers and the site-specific cultivation of cells in a confined space. 相似文献
125.
Prof. Dr. Katsuhiro Isozaki Tomoya Yokoi Ryota Yoshida Dr. Kazuki Ogata Dr. Daisuke Hashizume Dr. Nobuhiro Yasuda Prof. Dr. Koichiro Sadakane Prof. Dr. Hikaru Takaya Prof. Dr. Masaharu Nakamura 《化学:亚洲杂志》2016,11(7):1076-1091
Two (ONO pincer)ruthenium‐complex‐bound norvalines, Boc?[Ru(pydc)(terpy)]Nva?OMe ( 1 ; Boc=tert‐butyloxycarbonyl, terpy=terpyridyl, Nva=norvaline) and Boc?[Ru(pydc)(tBu‐terpy)]Nva?OMe ( 5 ), were successfully synthesized and their molecular structures and absolute configurations were unequivocally determined by single‐crystal X‐ray diffraction. The robustness of the pincer Ru complexes and norvaline scaffolds against acidic/basic, oxidizing, and high‐temperature conditions enabled us to perform selective transformations of the N‐Boc and C?OMe termini into various functional groups, such as alkyl amide, alkyl urea, and polyether groups, without the loss of the Ru center or enantiomeric purity. The resulting dialkylated Ru‐bound norvaline, n‐C11H23CO?l ‐[Ru(pydc)(terpy)]Nva?NH‐n‐C11H23 (l ‐ 4 ) was found to have excellent self‐assembly properties in organic solvents, thereby affording the corresponding supramolecular gels. Ru‐bound norvaline l ‐ 1 exhibited a higher catalytic activity for the oxidation of alcohols by H2O2 than parent complex [Ru(pydc)(terpy)] ( 11 a ). 相似文献
126.
Negatively Charged π‐Electronic Systems by Deprotonation of Hydroxy‐Substituted Dipyrrolyldiketone Boron Complexes 下载免费PDF全文
Boron complexes of meso‐hydroxy‐substituted dipyrrolyldiketones, as the precursors of negatively charged π‐electronic systems, were synthesized via the oxidative introduction of an acetoxy unit at the meso position of dipyrrolyldiketones and subsequent hydrolysis. The anionic site formed upon deprotonation was moderately stabilized by hydrogen‐bond‐donating pyrrole NH, generating non‐complexing anionic species. 相似文献
127.
128.
The unprecedented diastereoselective Mannich reaction of a Z-allylsulfoximine was a key step in the total synthesis of the marine natural products azumamide A and E, and an unnatural analogue. Their relative potency as histone deacetylase inhibitors was evaluated and found to correlate with predicted zinc-binding affinity. [reaction: see text] 相似文献
129.
Hirotsugu Kobayashi Kohtaro Okada Takashi Iwashita Nobuhiro Fusetani 《Tetrahedron》2007,63(29):6748-6754
Three new serinolipid derivatives, shishididemniols C (1), D (2), and E (3), were isolated as antibacterial constituents of a tunicate of the family Didemnidae. Their planar structures were elucidated by interpretation of NMR and MS data, whereas the absolute stereochemistry was determined by chemical conversions. Shishididemniols C (3), D (4), and E (5) exhibited antibacterial activity against the fish pathogenic bacterium Vibrio anguillarum. 相似文献
130.
Gasanov R Aliyeva S Arao S Ismailova A Katsuta N Kitade H Yamada S Kawamori A Mamedov F 《Journal of photochemistry and photobiology. B, Biology》2007,86(2):160-164
Water splitting activity, the multiline EPR signal associated with S(2)-state of the CaMn(4)-cluster and the fast and slow phases of the induction curve of the millisecond delayed chlorophyll fluorescence from photosystem II (PSII) in the pH range of 4.5-8.5 were studied in the thylakoid membranes and purified PSII particles. It has been found that O(2) evolution and the multiline EPR signal were inhibited at acidic (pK approximately 5.3) and alkaline (pK approximately 8.1) pH values, and were maximal at pH 6.0-7.0. Our results indicate that the loss of O(2) evolution and the S(2)-state multiline EPR signal associated with the decrease of the millisecond delayed chlorophyll fluorescence only in alkaline region (pH 7.0-8.5). Possible correlations of the millisecond delayed chlorophyll fluorescence components with the donor side reactions in PSII are discussed. 相似文献