全文获取类型
收费全文 | 144篇 |
免费 | 4篇 |
专业分类
化学 | 114篇 |
力学 | 5篇 |
数学 | 6篇 |
物理学 | 23篇 |
出版年
2023年 | 1篇 |
2022年 | 2篇 |
2021年 | 6篇 |
2020年 | 4篇 |
2019年 | 2篇 |
2017年 | 1篇 |
2016年 | 1篇 |
2015年 | 5篇 |
2014年 | 1篇 |
2013年 | 9篇 |
2012年 | 5篇 |
2011年 | 19篇 |
2010年 | 7篇 |
2009年 | 6篇 |
2008年 | 11篇 |
2007年 | 15篇 |
2006年 | 11篇 |
2005年 | 3篇 |
2004年 | 5篇 |
2003年 | 7篇 |
2002年 | 5篇 |
2001年 | 1篇 |
2000年 | 2篇 |
1999年 | 1篇 |
1998年 | 2篇 |
1996年 | 1篇 |
1995年 | 2篇 |
1990年 | 2篇 |
1987年 | 1篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1979年 | 2篇 |
1975年 | 2篇 |
1973年 | 1篇 |
1942年 | 1篇 |
1938年 | 1篇 |
排序方式: 共有148条查询结果,搜索用时 0 毫秒
31.
A method for determination of equilibrium constants in heme model systems is proposed, based on successive linear regression applied to spectrophotometric titrations. The method is illustrated for bis(dimethylglyoximate) iron(II) complexes with pyridine and 4-cyanopyridine ligands. 相似文献
32.
We developed a new convenient method for generation of an abasic site at the 3'-terminus of an oligonucleotide. This method uses a 1-deaza-2'-deoxyguanosine residue, which easily undergoes depurination under acidic conditions. The abasic site of the oligonucleotide can be further modified with external functional groups. We report herein the chemical stability of 1-deaza-2'-deoxyguanosine in the oligodeoxynucleotide and the application to the postsynthetic modification of an oligonucleotide by utilizing the chemical property of 1-deaza-2'-deoxyguanosine. [Structure: see text] 相似文献
33.
34.
35.
Yoshinobu Morino Ikumasa Hidaka Yoji Oderaotoshi Mitsuo Komatsu Satoshi Minakata 《Tetrahedron》2006,62(52):12247-12251
A new protocol for the cyclization of N-alkenylamides using chloramine-T and iodine is described. When N-alkenylsulfonamides are treated with chloramine-T and iodine, three- to six-membered N-heterocycles are obtained with complete stereoselectivity. The method is compatible with the cyclization of the allylbenzamide or allylbenzthioamide to afford an oxazoline or thiazoline derivative, respectively. Mechanistic studies indicate that the chloramine-T/I2 system functions as an effective iodonium species. 相似文献
36.
37.
Nobuko Yoshimoto Osamu Shimamura Takuya Nishimura Minato Egashira Maiko Nishioka Masayuki Morita 《Electrochemistry communications》2009,11(2):481-483
A novel polymeric electrolyte based on a self-assembled copolymer moiety has been prepared by a simple method of photo-induced radical polymerization of a mixture consisting of stearylmethacrylate (SMA) and poly(ethylene glycol)-monomethacrylate (PEM) that dissolves LiBF4 as the electrolytic salt. The SMA moiety work as mechanically stable backbone and the PEM unit dissolving the salts serves as ion-conducting path in the polymeric composite. Solid-state NMR measurements indicated that the resulting polymer composite consists of PEM-rich and SMA-rich phases, each of which exists within several nanometers apart. The ionic conductivity of the polymer electrolyte with the composition of PEM/SMA = 7/3 (by mass ratio) was 2.8 × 10?5 S cm?1 at 50 °C, which was significantly higher than that of the polymer electrolyte based on cross-linked PEM copolymer without SMA. 相似文献
38.
Nakajima A Tahara M Yoshimura Y Nakazawa H 《Chemical & pharmaceutical bulletin》2007,55(10):1431-1438
Ketoprofen [(RS)-2-(3-benzoylphenyl)propanoic acid] is widely used for the treatment of inflammatory diseases and musculoskeletal injury. However, there is concern regarding its potential for photosensitization as a side effect. Free radicals and active oxygen species generated from ketoprofen on exposure to ultraviolet (UV) light have been implicated in phototoxicity and photosensitization. In this study, we examined the suppressing ability of some compounds for the free radicals and active oxygen species generated by the photodynamic reaction of ketoprofen, to determine a new resist of photosensitization by ketoprofen. Eight compounds, including six known free radical scavengers were individually mixed with ketoprofen, and the mixtures were exposed to UV. Then, the free radicals and the active oxygen species were determined by the electron spin resonance spectrometry to estimate suppressing and scavenging ability of compounds. The compounds that show promise in suppressing superoxide anion generation from UV-exposed ketoprofen were further evaluated using the on-line photo-irradiated superoxide anion detection system. It was confirmed that quercetin, a flavonoid, strongly suppresses the generation of free radicals and active oxygen species from UV-exposed ketoprofen. The experiments using the experimental formulation of an adhesive skin patch of ketoprofen containing quercetine and the Chemiluminescence analyzer (CLA) indicated that quercetin has high potential for use as an excipient in ketoprofen ointments to suppress phototoxicity and photosensitization by ketoprofen. 相似文献
39.
Hiratani K Kaneyama M Nagawa Y Koyama E Kanesato M 《Journal of the American Chemical Society》2004,126(42):13568-13569
Although there have been a lot of reports on the synthesis and properties of [n]rotaxanes (mainly n = 2), only a few reports on the synthesis of [1]rotaxane has been published by V?gtle's group and others (see ref 5). Generally speaking, [1]rotaxane might be expected to exhibit properties different from other rotaxanes, because the rotor and the axle in the [1]rotaxane is bound covalently and closely. We report on a novel method to make [1]rotaxanes via covalent bond formation from a macrocyclic compound. That is, we first prepared a bicyclic compound from macrocycle and then proceeded to [1]rotaxane by aminolysis. This is the first synthetic example of preparation of [1]rotaxane via covalent bond formation, not utilizing weak interactions such as hydrogen bonding, charge transfer, via metal complexation, etc. This method might provide a powerful and new tool for construction of [1]rotaxane as a new supramolecular system. In addition, we investigated energy transfer from rotor to axle using [1]rotaxane that we prepared. Energy transfer occurred perfectly from the naphthalene ring of the rotor to the anthracene ring of the axle. We found also that only lithium ion among alkali ions can drastically enhance the fluorescence intensity. This finding could be applicable to ion-sensing systems, switching devices, and so on. 相似文献
40.
This paper presents two fast cycle canceling algorithms
for the submodular ow problem. The rst uses an assignment
problem whose optimal solution identies most negative
node-disjoint cycles in an auxiliary network. Canceling these
cycles lexicographically makes it possible to obtain an optimal
submodular ow in O(n
4
h log(nC)) time, which almost matches the
current fastest weakly polynomial time for submodular flow
(where n is the number of
nodes, h is the time for
computing an exchange capacity, and C is the maximum absolute value of arc
costs). The second algorithm generalizes Goldbergs cycle
canceling algorithm for min cost flow to submodular flow to also
get a running time of O(n
4
h log(nC)).. We show how to modify these
algorithms to make them strongly polynomial, with running times
of O(n
6
h log n), which matches the fastest strongly
polynomial time bound for submodular flow. We also show how to
extend both algorithms to solve submodular flow with separable
convex objectives. * An extended abstract of a preliminary version of
part of this paper appeared in [22]. Research supported in part by a Grant-in-Aid of
the Ministry of Education, Science, Sports and Culture of
Japan. Research supported by an NSERC Operating Grant.
Part of this research was done during a sabbatical leave at
Cornell SORIE.§ Research supported in part by a Grant-in-Aid of
the Ministry of Education, Science, Sports and Culture of
Japan. 相似文献