全文获取类型
收费全文 | 402篇 |
免费 | 13篇 |
国内免费 | 3篇 |
专业分类
化学 | 302篇 |
晶体学 | 1篇 |
力学 | 6篇 |
数学 | 23篇 |
物理学 | 86篇 |
出版年
2022年 | 2篇 |
2019年 | 6篇 |
2018年 | 2篇 |
2017年 | 3篇 |
2016年 | 8篇 |
2015年 | 6篇 |
2014年 | 15篇 |
2013年 | 19篇 |
2012年 | 11篇 |
2011年 | 16篇 |
2010年 | 12篇 |
2009年 | 12篇 |
2008年 | 26篇 |
2007年 | 26篇 |
2006年 | 25篇 |
2005年 | 29篇 |
2004年 | 23篇 |
2003年 | 23篇 |
2002年 | 17篇 |
2001年 | 7篇 |
2000年 | 11篇 |
1999年 | 5篇 |
1997年 | 9篇 |
1996年 | 7篇 |
1995年 | 5篇 |
1994年 | 5篇 |
1993年 | 3篇 |
1992年 | 3篇 |
1991年 | 3篇 |
1990年 | 4篇 |
1989年 | 4篇 |
1988年 | 4篇 |
1987年 | 5篇 |
1986年 | 3篇 |
1985年 | 4篇 |
1984年 | 2篇 |
1982年 | 3篇 |
1981年 | 11篇 |
1980年 | 4篇 |
1979年 | 4篇 |
1978年 | 2篇 |
1977年 | 5篇 |
1976年 | 5篇 |
1975年 | 2篇 |
1970年 | 1篇 |
1969年 | 1篇 |
1968年 | 3篇 |
1967年 | 2篇 |
1966年 | 1篇 |
1960年 | 1篇 |
排序方式: 共有418条查询结果,搜索用时 15 毫秒
101.
102.
Takeshi Yamanobe Tadashi Komoto Yoshiko Sakaino 《Molecular Crystals and Liquid Crystals》2013,570(1-2):273-282
Abstract Solid state NMR measurements are carried out for polymorphs and inclusion complexes of 4,5-bis(4-methoxyphenyl)-2-(3-nitrophenyl)-1H-imidazole. Observed 13C and 15N chemical shifts are characteristic of each polymorph A, B, C and D. In addition, 15N chemical shift was a good index for understanding hydrogen bond. VT measurements revealed that B transforms to C between 93 and 113°C. From PSTMAS and 1H solid echo measurements for AcOET inclusion complex, host molecules have almost same structure as B and guest molecules have the highest mobility of all inclusion complexes. 相似文献
103.
Tryptophan (Trp), an aromatic amino acid, is a constituent of peptides/proteins and is also a precursor of serotonin, kynurenine derivatives, and nicotinamide adenine dinucleotides. There have been a number of reports on photochemical reactions involving peptides/proteins which contain Trp that showed significant photodegradation, dimerization, and photoionization. The photochemical properties of Trp have not been fully elucidated, and this would provide novel insight into the handling of Trp-containing peptides/proteins. Consequently, we have been trying to evaluate the photochemical properties of Trp, as well as other essential amino acids, focusing on their photosensitivity, photodegradation, and their ability to induce lipid peroxidation. Among all the essential amino acids tested, Trp exhibited the maximal level of superoxide anion generation under 18 h of light exposure (30000 lux). UV spectral analysis of Trp suggested the absorbability of UVA/B light, and exposure of Trp, in both solid and solution states, to UVA/B light resulted in significant photodegradation (t(0.5): 18 h) and gradual color changes. In addition, photoirradiated Trp generated lipoperoxidant, a causative agent of photoirritation, and this might be associated with ROS generation. 相似文献
104.
105.
Revisiting the Bromination of CH Bonds with Molecular Bromine by Using a Photo‐Microflow System 下载免费PDF全文
Dr. Yoshiyuki Manabe Yuriko Kitawaki Masahiro Nagasaki Prof. Koichi Fukase Prof. Hiroshi Matsubara Yoshiko Hino Prof. Takahide Fukuyama Prof. Ilhyong Ryu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(40):12750-12753
The photobromination of C?H bonds by using molecular bromine was reinvestigated under microfluidic conditions. The continuous‐flow method suppressed the production of dibrominated compounds and effectively produced the desired monobrominated products with high selectivity. Rapid bromination of benzylic substrates containing a photoaffinity azide group was achieved without any decomposition. 相似文献
106.
A novel impact three-point bend test method for determining dynamic fracture-initiation toughness 总被引:6,自引:0,他引:6
A novel impact three-point bend test method has been developed for determining the dynamic fracture-initiation toughness,K
Id, over the range of loading rates
. The split-Hopkinson pressure-bar technique is used to measure dynamic loads applied to a bend specimen with a fatigue precrack.
The stress-intensity-factor histories for the bend specimen are evaluated by means of a dynamic finite-element technique and
the standard formula (ASTM E 399-83) based on the measured dynamic loads. The time of crack initiation is determined using
a strain gage mounted near a crack tip. The results for 7075-T6 aluminum alloy and Ti−6A1−2Sn−4Zr−6Mo alloy indicate that
the reliableK
Id data can only be obtained by evaluation procedures which take the inertial effects into account. It is shown that the novel
impact bend test method in conjunction with dynamic finite-element analysis provides an effective means of characterizing
the dynamic fracture-toughness parameterK
Id. 相似文献
107.
Percec V Glodde M Peterca M Rapp A Schnell I Spiess HW Bera TK Miura Y Balagurusamy VS Aqad E Heiney PA 《Chemistry (Weinheim an der Bergstrasse, Germany)》2006,12(24):6298-6314
Semifluorinated first-generation self-assembling dendrons attached via a flexible spacer to electron-donor molecules induce pi-stacking of the donors in the center of a supramolecular helical pyramidal column. These helical pyramidal columns self-organize in various columnar liquid crystal phases that mediate self-processing of large single crystal liquid crystal domains of columns and self-repair their intracolumnar structural defects. In addition, all supramolecular columns exhibit a columnar phase at lower temperatures that maintains the helical pyramidal columnar supramolecular structure and displays higher intracolumnar order than that in the liquid crystals phases. The results described here demonstrate the universality of this concept, the power of the fluorous phase or the fluorophobic effect in self-assembly and the unexpected generality of pyramidal liquid crystals. 相似文献
108.
Yamauchi A Sakashita Y Hirose K Hayashita T Suzuki I 《Chemical communications (Cambridge, England)》2006,(41):4312-4314
Pseudorotaxane formed by reacting beta-cyclodextrin bearing a phenylboronic acid residue with 1-heptyl-4-(4'-dimethylaminostyryl)pyridinium functioned as a novel fluorescent saccharide receptor having unique responses. 相似文献
109.
A method of separating a Slater determinant wave function with a two-center neck structure into spatially localized subsystems is proposed, and it is applied to α + α Margenau–Brink cluster wave functions and antisymmetrized molecular dynamics wave functions of the ground state in 10Be and a negative-parity largely deformed state in 35S. 相似文献
110.
Liquid ionization mass spectrometry is a soft ionization technique used with liquid samples under atmospheric pressure. It facilitates the handling of reagents and the observation of ion–molecule reactions in the ion source. The differentiation of isomers by characteristic fragment ions, for example those resulting from asymmetrical cleavage of a cyclobutane ring, and by molecular adduct ion formation was studied. The samples studied were cyclobutane derivatives, alkyl 4-(3-oxo-3-pIienyl-l-aIkenyl)benzoate dimers, and reagents having two functional groups were used to produce adduct ions to clarify the difference between isomers. The reagents act on a sample molecule at two functional groups to form hydrogen bonds. Some correlations were observed between the structure of the sample and the relative abundances of molecular adduct ions and also fragment ions produced by collisionally activated dissociation. 相似文献