全文获取类型
收费全文 | 1191篇 |
免费 | 30篇 |
国内免费 | 3篇 |
专业分类
化学 | 872篇 |
晶体学 | 10篇 |
力学 | 9篇 |
数学 | 30篇 |
物理学 | 303篇 |
出版年
2022年 | 4篇 |
2021年 | 13篇 |
2020年 | 12篇 |
2019年 | 17篇 |
2018年 | 12篇 |
2017年 | 6篇 |
2016年 | 20篇 |
2015年 | 15篇 |
2014年 | 19篇 |
2013年 | 57篇 |
2012年 | 55篇 |
2011年 | 91篇 |
2010年 | 43篇 |
2009年 | 51篇 |
2008年 | 69篇 |
2007年 | 73篇 |
2006年 | 63篇 |
2005年 | 59篇 |
2004年 | 58篇 |
2003年 | 51篇 |
2002年 | 42篇 |
2001年 | 32篇 |
2000年 | 27篇 |
1999年 | 16篇 |
1998年 | 16篇 |
1997年 | 9篇 |
1996年 | 16篇 |
1995年 | 12篇 |
1994年 | 20篇 |
1993年 | 9篇 |
1992年 | 20篇 |
1991年 | 12篇 |
1990年 | 16篇 |
1989年 | 9篇 |
1988年 | 15篇 |
1987年 | 13篇 |
1986年 | 10篇 |
1985年 | 24篇 |
1984年 | 13篇 |
1983年 | 4篇 |
1982年 | 8篇 |
1981年 | 14篇 |
1980年 | 11篇 |
1979年 | 16篇 |
1978年 | 4篇 |
1977年 | 5篇 |
1976年 | 7篇 |
1975年 | 7篇 |
1974年 | 6篇 |
1973年 | 9篇 |
排序方式: 共有1224条查询结果,搜索用时 15 毫秒
101.
The dissociative adsorption of cyclopropane on the copper surface was studied using quantum chemical molecular dynamics method with “Colors-Excite” code and density functional theory by Amsterdam Density Functional program (ADF2000). The excited state of cyclopropane was used as adsorbate to simulate the dissociated adsorption under an irradiation energy of ca. 10 eV. One of the C-C bonds in cyclopropane was broken and the two new bonds between cyclopropane and copper surface were formed. The electrons transferred from the copper atoms to cyclopropane with a value of about 0.2e. The shorter distances between the carbons and surface copper atoms showed the existence of strong interaction. Consistently, the results indicated metallacyclopentane was the most possible intermediate species in dissociative adsorption by ADF2000 and “Colors-Excite” method. 相似文献
102.
103.
104.
105.
Megumi Kubo Takashi Kikukawa Seiji Miyauchi Akiteru Seki Masakatsu Kamiya Tomoyasu Aizawa Keiichi Kawano Naoki Kamo Makoto Demura 《Photochemistry and photobiology》2009,85(2):547-555
Halorhodopsin (HR) acts as a light‐driven chloride pump which transports a chloride ion from the extracellular (EC) to the cytoplasmic space during a photocycle reaction that includes some photointermediates initiated by illumination. To understand the chloride uptake mechanisms, we focused on a basic residue Arg123 of HR from Natronomonas pharaonis (NpHR), which is the only basic residue located in the EC half ion channel. By the measurements of the visible absorption spectra in the dark and the light‐induced inward current through the membrane, it was shown that the chloride binding and transport ability of NpHR completely disappeared by the change of arginine to glutamine. From flashphotolysis analysis, the photocycle of R123Q differed from that of wildtype NpHR completely. The response of the R123H mutant depended on pH. These facts imply that the positive charge at position 123 is essential for chloride binding in the ground state and for the chloride uptake under illumination. On the basis of the molecular structures of HR and the anion‐transportable mutants of bacteriorhodopsin, the effects of the positive charge and the conformational change of the Arg123 side chain as well as the chloride‐pumping mechanism are discussed. 相似文献
106.
Hiromitsu Maeda 《Journal of inclusion phenomena and macrocyclic chemistry》2009,64(3-4):193-214
The supramolecular chemistry of acyclic oligopyrrole derivatives mainly reported by the author’s group in the last four years has been summarized in this review. The author has demonstrated the “first step” to construct the new materials and concepts based on the new molecular systems consisting of pyrrole rings, which form the complexes, assemblies, and organized structures, by using noncovalent interactions such as metal coordination, hydrogen bonding, and π–π interaction. Acyclic π-conjugated oligopyrroles have exhibited not only host–guest binding behaviors in solutions but also the formation of, for example, (i) metal coordination polymers to give emissive colloidal spheres, (ii) solid-state assemblies of acyclic π-conjugated anion receptors and their anion complexes, (iii) anion-responsive supramolecular gels from the receptors with aliphatic chains, and (iv) solvent-assisted organized structures like vesicles derived from amphiphilic anion receptors. 相似文献
107.
Taku Hirama Takayuki Umemura Noriyuki Kogure Mariko Kitajima Hiromitsu Takayama 《Tetrahedron letters》2017,58(3):223-226
A new procedure for the asymmetric total synthesis of lythraceous alkaloids with a 4-arylquinolizidine skeleton was developed, which involved an organocatalyzed asymmetric intramolecular aza-Michael addition. 相似文献
108.
A method in which antibodies are produced by using an immunogen heterogeneously conjugated with two or more kinds of haptens having unlike chemical structures against a same carrier protein was offered as an efficient approach for development of antibody to low molecular compounds. To appreciate the potentiality of the approach, 17β-estradiol (E2) and testosterone were selected as model compounds. The I50 values of antiserum developed were 6 and 8 μg L−1 with the detection limits of 0.02 and 0.15 μg L−1 for E2 and testosterone, respectively. Antiserum owned an interesting characteristic that it was possible to independently analyze E2 and testosterone without mutual interference by making proper use of coating antigens. When using β-estradiol 17-hemisuccuinate (EH) conjugated with bovine serum albumin (BSA) as a coating antigen, the enzyme-linked immunosorbent assay (ELISA) was very selective to E2 and some estrogen analogues. Therefore, if testosterone coexisted in the ELISA for E2 detection, it showed no interference with it. From these findings, it was suggested that the verified method was an efficient and rational approach in development of polyclonal antibody to low molecular compounds. 相似文献
109.
Takashi Hashimoto Takuma Nishimura Jong Min Lim Prof. Dr. Dongho Kim Prof. Dr. Hiromitsu Maeda 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(38):11653-11661
Bidipyrrin‐bridged macrocycles, prepared from NiII‐bridged dipyrrin‐based nanorings by intramolecular oxidative biaryl coupling reactions, yielded [2+4]‐type ZnII‐assisted stable twisted‐ring dimers comprising two double helices. These [2+4]‐type metal complexes can be optically resolved by chiral HPLC and exhibit tunable electronic and optical properties as a result of spring‐like motions. The double helices behave as glue to connect two macrocycles and as the screws of hinges to form thermally responsive synchronized spring systems. 相似文献
110.
It was shown that ubiquinone (CoQ10) and ubiquinol (CoQ10H2) produce fluorescence products under alkaline conditions when reacted with 2-cyanoacetamide. The reaction mixture from CoQ10 gave fluorescence with excitation and emission maximum wavelengths at 442 nm and 549 nm, respectively. This reaction was
considered to proceed via Craven’s reaction. Moreover, 2-cyanoacetamide was shown to be a useful reagent for high-performance
liquid chromatography (HPLC) with post-column fluorescence derivatization of CoQ10 and CoQ10H2 in blood. CoQ10 showed a linear response in the range of 0.32–1276 ng, and the detection limit (S/N = 3) was 0.16 ng. Moreover, the sample
pretreatment by deproteinization and extraction of CoQ10 and CoQ10H2 from plasma using 1-propanol with potassium formate was effective for excellent separation of CoQ10 and CoQ10H2 from other fluorescent substances in the blood. This simple and rapid pretreatment was considered to minimize the oxidation
of CoQ10H2. On the other hand, CoQ10 and CoQ10H2 in plasma samples obtained by finger prick were detected, as in venous blood obtained by venipuncture. Our method involving
the simple and rapid collection of plasma by finger prick and sample pretreatment is thought to be applicable for the determination
of CoQ10H2/total CoQ10 ratio as a biomarker of oxidative stress. 相似文献