全文获取类型
收费全文 | 893篇 |
免费 | 34篇 |
国内免费 | 4篇 |
专业分类
化学 | 687篇 |
晶体学 | 17篇 |
力学 | 16篇 |
数学 | 54篇 |
物理学 | 157篇 |
出版年
2023年 | 3篇 |
2022年 | 3篇 |
2021年 | 4篇 |
2020年 | 17篇 |
2019年 | 13篇 |
2018年 | 8篇 |
2016年 | 14篇 |
2015年 | 21篇 |
2014年 | 20篇 |
2013年 | 56篇 |
2012年 | 43篇 |
2011年 | 46篇 |
2010年 | 23篇 |
2009年 | 32篇 |
2008年 | 74篇 |
2007年 | 56篇 |
2006年 | 74篇 |
2005年 | 69篇 |
2004年 | 46篇 |
2003年 | 34篇 |
2002年 | 47篇 |
2001年 | 16篇 |
2000年 | 17篇 |
1999年 | 7篇 |
1998年 | 5篇 |
1997年 | 9篇 |
1996年 | 9篇 |
1995年 | 11篇 |
1994年 | 10篇 |
1993年 | 10篇 |
1992年 | 10篇 |
1991年 | 4篇 |
1990年 | 3篇 |
1989年 | 8篇 |
1988年 | 8篇 |
1987年 | 3篇 |
1985年 | 13篇 |
1984年 | 13篇 |
1983年 | 7篇 |
1982年 | 10篇 |
1981年 | 5篇 |
1980年 | 3篇 |
1979年 | 5篇 |
1978年 | 7篇 |
1977年 | 7篇 |
1976年 | 4篇 |
1975年 | 4篇 |
1974年 | 4篇 |
1973年 | 6篇 |
1932年 | 2篇 |
排序方式: 共有931条查询结果,搜索用时 15 毫秒
41.
Yusuke Yoshimura Ryuichiro Hibi Akiho Nakata Moeka Togashi Shoujiro Ogawa Takayuki Ishige Mamoru Satoh Fumio Nomura Tatsuya Higashi 《Biomedical chromatography : BMC》2019,33(7)
A liquid chromatography/electrospray ionization–tandem mass spectrometry‐based method was developed for the identification of the conjugation positions of the monoglucuronides of 25‐hydroxyvitamin D3 [25(OH)D3] and 24,25‐dihydroxyvitamin D3 [24,25(OH)2D3] in human urine. The method employed derivatization with 4‐(4‐dimethylaminophenyl)‐1,2,4‐triazoline‐3,5‐dione to convert the glucuronides into fragmentable derivatives, which provided useful product ions for identifying the conjugation positions during the MS/MS. The derivatization also enhanced the assay sensitivity and specificity for urine sample analysis. The positional isomeric monoglucuronides, 25(OH)D3‐3‐ and ‐25‐glucuronides, or 24,25(OH)2D3‐3‐, ‐24‐ and ‐25‐glucuronides, were completely separated from each other under the optimized LC conditions. Using this method, the conjugation positions were successfully determined to be the C3 and C24 positions for the glucuronidated 25(OH)D3 and 24,25(OH)2D3, respectively. The 3‐glucuronide was not present for 24,25(OH)2D3, unlike 25(OH)D3, thus we found that selective glucuronidation occurs at the C24‐hydroxy group for 24,25(OH)2D3. 相似文献
42.
Yusuke Kawashima Mamoru Satoh Tatsuya Saito Takashi Matsui Fumio Nomura Hiroyuki Matsumoto Yoshio Kodera 《Biomedical chromatography : BMC》2013,27(6):691-694
We report a cyclic sample pooling technique devised in two‐dimensional liquid chromatography–electrospray ionization mass spectrometry (LC‐ESI‐MS) shotgun proteomics that renders deeper proteome coverage; we combined low pH reversed‐phase (RP) LC in trifluoroacetic acid in the first dimension, followed by cyclic sample pooling of the eluate and low‐pH RP‐LC in formic acid in the second dimension. The new protocol has a significantly higher resolving power suitable for LC‐ESI‐MS/MS shotgun proteomics. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
43.
Prof. Jun Ishihara Fuma Usui Tomohiro Kurose Tomohiro Baba Yasunori Kawaguchi Yuki Watanabe Prof. Susumi Hatakeyama 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(6):1543-1552
The upper fragment of spirolides A and B, which are marine phycotoxins that exhibit strong antagonistic activities on nicotinic acetylcholine receptors, was constructed. The functionalized cyclohexene in spirolides was stereoselectively synthesized from the bicyclic lactone, which could be readily accessed by the Lewis acid template-catalyzed asymmetric Diels–Alder reaction of the pentadienol and methyl acrylate. 相似文献
44.
45.
Dr. Tatsuya Nishimaru Dr. Kohei Eto Dr. Keita Komine Prof. Dr. Jun Ishihara Prof. Dr. Susumi Hatakeyama 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(33):7927-7934
The first total synthesis of lajollamycin B, a structurally novel nitro-tetraene spiro-β-lactone/γ-lactone antibiotic, is described. The convergent synthesis involves the construction of the C8′–C11′ nitrodienylstannane and its coupling with the segment prepared from the C1′–C7′ ω-iodoheptadienoic acid and the right-hand heterocyclic fragment, which has been utilized for our previous syntheses of oxazolomycin A. The revision of the geometry of the terminal Δ10′, 11′-double bond from E to Z is also described for the structure of natural lajollamycin B. 相似文献
46.
47.
Hyoe Hatakeyama Ayako Hirogaki Hiroshi Matsumura Tatsuko Hatakeyama 《Journal of Thermal Analysis and Calorimetry》2013,114(3):1075-1082
Sodium ligninosulfonate (LS)-based polyurethane (PU) foams were prepared using three kinds of ethylene glycols, diethylene glycol, triethylene glycol or polyethylene glycol. Two kinds of industrial NaLS, acid-based and alkaline-based NaLS, were mixed with various ratios, and foaming reactions were controlled. Mixing, cream, and rise time were used as an index of foaming reaction. Mixing time was defined as the time interval from adding isocyanate to detection of evolved heat under stirring, cream time as the time interval from termination of stirring to starting of foaming, and rise time as the time interval from starting to completion of foaming. The above reaction time increased with increasing amount of acid base NaLS content in polyols. Apparent density, compression strength and compression modulus of PU foams linearly increased with reaction time. Thermal decomposition temperature was measured by thermogravimetry and glass transition temperature by differential scanning calorimetry. Glass transition temperature can be controlled in a temperature range from 310 to 390 K by changing the mixing rate of two kinds of LS and molecular mass of ethylene glycols. It was found that mechanical and thermal properties of PU foams are controllable through the foaming reaction rate using two kinds of industrial lignin. 相似文献
48.
Using p,p'-dimethoxydiphenyldiazomethane (DMDM) as initiator, the polymerization of methyl methacrylate (MMA) in benzene or in bulk was carried out. The initial rate of polymerization, Rp, was found to be expressed by the following equation: Rp = k[DMDM]0.53 [MMA]0.84 The polymerization was confirmed to proceed by a radical mechanism. The over-all activation energy for the polymerization in benzene was calculated as 19.3 kcal/mole. The rate of thermal decomposition of DMDM was also measured in benzene and the rate equation was obtained as follows: kd (sec?1) = 1.0 × 1015 exp (?29.1 kcal/RT) (for 50-80°C) Explanations of these observations are discussed in connection with those of the preceding papers. 相似文献
49.
Several polyurethanes based on bis-(p-oxymethylphenyl) terephthalate (BOPT) were synthesized and studied with respect to some of their thermal properties. BOPT exhibits a mesomorphic phase at 252–264°C. Polymerization was carried out by equimolar reaction with hexamethyl-ene diisocyanate (HDI), 4,4-dicyclohexylmethane diisocyanate (H12MDI) α,α'-diisocyanate-1,3-dimethylcyclohexane (H6 XDI), 4,4′-diphenylmeth-ane diisocyanate (MDI), 2,4-tolylene diisocyanate (TDI), and phenylene diisocyanate (PDI). It became clear that polyurethanes obtained from BOPT with HDI, H12MDI, H6XDI, and TDI have mesomorphic phases at 243–291, 214–250, 172–229, and 180–234°C, respectively, as determined by DSC and polarized microscopy, and that all polyurethanes are crystalline as evidenced by x-ray diffraction. 相似文献
50.