全文获取类型
收费全文 | 1732篇 |
免费 | 86篇 |
国内免费 | 10篇 |
专业分类
化学 | 1400篇 |
晶体学 | 22篇 |
力学 | 13篇 |
数学 | 113篇 |
物理学 | 280篇 |
出版年
2023年 | 15篇 |
2022年 | 16篇 |
2021年 | 26篇 |
2020年 | 35篇 |
2019年 | 40篇 |
2018年 | 20篇 |
2017年 | 17篇 |
2016年 | 47篇 |
2015年 | 34篇 |
2014年 | 52篇 |
2013年 | 85篇 |
2012年 | 134篇 |
2011年 | 119篇 |
2010年 | 76篇 |
2009年 | 53篇 |
2008年 | 130篇 |
2007年 | 100篇 |
2006年 | 108篇 |
2005年 | 119篇 |
2004年 | 110篇 |
2003年 | 88篇 |
2002年 | 64篇 |
2001年 | 21篇 |
2000年 | 18篇 |
1999年 | 11篇 |
1998年 | 10篇 |
1997年 | 20篇 |
1996年 | 17篇 |
1995年 | 15篇 |
1994年 | 6篇 |
1993年 | 14篇 |
1992年 | 9篇 |
1991年 | 8篇 |
1990年 | 8篇 |
1988年 | 7篇 |
1987年 | 9篇 |
1986年 | 6篇 |
1985年 | 14篇 |
1984年 | 19篇 |
1983年 | 9篇 |
1982年 | 13篇 |
1981年 | 18篇 |
1980年 | 15篇 |
1979年 | 15篇 |
1978年 | 10篇 |
1977年 | 14篇 |
1976年 | 9篇 |
1975年 | 4篇 |
1974年 | 4篇 |
1973年 | 8篇 |
排序方式: 共有1828条查询结果,搜索用时 15 毫秒
141.
Junro Yoshino Dr. Akiko Furuta Tetsuya Kambe Hiroaki Itoi Naokazu Kano Prof. Takayuki Kawashima Prof. Yuzuru Ito Dr. Makoto Asashima Prof. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(17):5026-5035
2‐[Bis(pentafluorophenyl)boryl]azobenzenes bearing hydrogen, methoxy, dimethylamino, trifluoromethyl, fluoro, n‐butyl, and tert‐butyldimethylsiloxy groups at the 4′‐position or methoxy and bromo groups at the 4‐position have been synthesized. The 4‐bromo group of the 2‐boryl‐4‐bromoazobenzene derivative was converted to phenyl and diphenylamino groups by palladium‐catalyzed reactions. The absorption and fluorescence properties have been investigated using UV/Vis and fluorescence spectroscopy. The 2‐borylazobenzenes emitted an intense green, yellow, and orange fluorescence, in marked contrast to the usual azobenzene fluorescence. The 4′‐siloxy derivative showed the highest fluorescence quantum yield (0.90) among those reported for azobenzenes to date. The correlation between the substituent and the fluorescence properties was elucidated by studying the effect of the substituent on the relaxation process and from DFT and TD‐DFT calculations. An electron‐donating group at the 4′‐position was found to be important for an intense emission. Application of fluorescent azobenzenes as a fluorescent vital stain for the visualization of living tissues was also investigated by microinjection into Xenopus embryos, suggesting these compounds are nontoxic towards embryos. 相似文献
142.
Hiroaki Aizawa Ken Hatano Hitoshi Saeki Nobuaki Honsho Tetsuo Koyama Koji Matsuoka Daiyo Terunuma 《Tetrahedron letters》2010,51(12):1545-6442
A new compound having a 2,3,4,5-tetraphenylsilole derivative on the center silicon of Dumbbell(1)6Gb3; Silole-Dumbbell(1)6Gb3 (1) was previously reported. It was found that 1 exhibited strongly increased fluorescence both in water and in a 96% acetone/water mixed solvent. The physical behavior of 1 in water and in the 96% acetone/water mixed solvent was investigated, and analyses including fluorescence quantum yields, dynamic-light-scattering (DLS), atomic-force-microscopy (AFM), and fluorescence microscopy were carried out. It was clarified that 1 dynamically formed different types of aggregates in water and in higher acetone concentrations to yield high aggregation-induced emission (AIE) effects due to the formation of micelle-like particles in water and inversion-type micelles in the acetone/water mixed solvent, respectively. 相似文献
143.
Kuniaki Tatsuta Hiroaki Tanaka Hitomi Tsukagoshi Takafumi Kashima Seijiro Hosokawa 《Tetrahedron letters》2010,51(42):5546-5549
The total synthesis of lactonamycin has been achieved. The synthesis includes sequential intramolecular conjugate addition of alcohols to the acetylenic ester, stereoselective glycosylation of the tertiary alcohol, and Michael-Dieckmann type cyclization with the thioester, by which the highly convergent route has been established. 相似文献
144.
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
145.
Ali Izadi-Najafabadi Takeo Yamada Don N. Futaba Hiroaki Hatori Sumio Iijima Kenji Hata 《Electrochemistry communications》2010,12(12):1678-1681
We report the energy and power voltage-dependencies of supercapacitors using single-walled carbon nanotube electrodes. The energy density was dependent on the cell-voltage cubed (up to 4 V: E = 1.43 × V3). The cubic relationship was attributed to the linear increase of the capacitance as a function of voltage, enabled by electrochemical doping. Furthermore, while up to 3.5 V, the maximum power rating of the nanotube electrodes increased as a function of the cell-voltage squared, beyond 3.5 V, a decline in power was observed as a result of depletion of the electrolyte's ions. 相似文献
146.
Ha J Seo HY Shim YS Nam HJ Seog H Ito M Nakagawa H 《Journal of AOAC International》2010,93(6):1905-1911
A sensitive and specific heating block method coupled with ultra-HPLC (u-HPLC) was developed for the analysis of capsaicin in Gochujang and validated by comparing with a conventional HPLC (AOAC Method 995.03). The method validation parameters yielded good results, including linearity, precision, accuracy, and recovery. The u-HPLC separation was performed on a reversed C18 column (50 x 2 mm id, particle size 2 microm), followed by fluorescence detection (excitation 280 nm, emission 325 nm). Methanol was used as the extracting solvent, and the amount of sample taken was approximately 0.2 g; the optimum amount of extraction solvent and extraction time were 15 mL and 1 h, respectively. The recovery of capsaicin in Gochujang was more than 93%, and the LOD and LOQ of the u-HPLC analysis were 0.05 and 0.16 microg/g for capsaicin and 0.05 and 0.16 microg/g for dihydrocapsaicin. The calibration graphs for capsaicin and dihydrocapsaicin were linear from 0.2 to 10.0 microg/mL for u-HPLC. The interday and intraday precisions (RSD values) were < 6.27%. 相似文献
147.
Takenaka S Susuki N Miyamoto H Tanabe E Matsune H Kishida M 《Chemical communications (Cambridge, England)》2010,46(47):8950-8952
Pd cathode catalysts for polymer electrolyte fuel cells have been covered with silica layers a few nanometres thick. The silica-coated Pd catalysts showed high activity and excellent durability for the oxygen reduction under the severe cathode conditions of PEFCs, while Pd catalysts without silica-coating were seriously deactivated under the same conditions. The coverage of Pd metal with silica prevents the diffusion of Pd species out of the silica layers. 相似文献
148.
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
149.
Geometry optimization was performed for the ground states of FeCO, Fe(CO)2, and Fe(CO)3 at various levels of ab initio calculations, and the bond lengths and dissociation energies obtained were in reasonable agreement
with experimental results. The nature of bonding was studied for these molecules using a complete-active-space self-consistent-field
method. From the Mulliken population analysis, it was found that the traditional donation and back donation mechanism is valid
for these molecules, including Fe(CO)3, which has a pyramidal structure.
Received: 27 September 1999 / Accepted: 13 January 2000 / Published online: 19 April 2000 相似文献
150.