全文获取类型
收费全文 | 983篇 |
免费 | 62篇 |
国内免费 | 6篇 |
专业分类
化学 | 845篇 |
晶体学 | 13篇 |
力学 | 10篇 |
数学 | 54篇 |
物理学 | 129篇 |
出版年
2023年 | 5篇 |
2022年 | 13篇 |
2021年 | 17篇 |
2020年 | 24篇 |
2019年 | 39篇 |
2018年 | 16篇 |
2017年 | 14篇 |
2016年 | 41篇 |
2015年 | 31篇 |
2014年 | 39篇 |
2013年 | 60篇 |
2012年 | 85篇 |
2011年 | 81篇 |
2010年 | 63篇 |
2009年 | 56篇 |
2008年 | 74篇 |
2007年 | 69篇 |
2006年 | 63篇 |
2005年 | 51篇 |
2004年 | 57篇 |
2003年 | 40篇 |
2002年 | 31篇 |
2001年 | 9篇 |
2000年 | 10篇 |
1999年 | 7篇 |
1998年 | 6篇 |
1997年 | 4篇 |
1996年 | 10篇 |
1995年 | 2篇 |
1994年 | 2篇 |
1993年 | 3篇 |
1992年 | 1篇 |
1991年 | 3篇 |
1990年 | 3篇 |
1989年 | 2篇 |
1988年 | 1篇 |
1987年 | 4篇 |
1986年 | 2篇 |
1984年 | 3篇 |
1982年 | 1篇 |
1980年 | 5篇 |
1976年 | 1篇 |
1975年 | 2篇 |
1974年 | 1篇 |
排序方式: 共有1051条查询结果,搜索用时 31 毫秒
991.
992.
Koji Hatanaka Ken-ichiro Yomogihata Hiroshi Ono Kei Nagafuchi Hiroshi Fukumura Michiko Fukushima Tomohiro Hashimoto Saulius Juodkazis Hiroaki Misawa 《Journal of Non》2008,354(52-54):5485-5490
We have generated hard X-rays by front- and back-side femtosecond laser irradiation of PbO-rich glass. The actual Pb content of glasses was corroborated by Pb M-line emission intensities with an uncertainty of less than 20%. The elements K and As at concentrations of a few mol% were detected. X-ray generation by back-side irradiation helped to avoid an air breakdown; however, self-focusing and filamentation limited the achievable light intensity and effectiveness of X-ray generation. Characteristics and mechanisms of X-ray generation from the front- and back-side of glasses are discussed. 相似文献
993.
Splice-quotient singularities were introduced recently and studiedintensively by Neumann and Wahl. For such a singularity we provethat the geometric genus can be recovered from the topologyof the singularity, namely from the Seiberg–Witten invariant(associated with the canonical spinc structure) of the link.This answers positively the conjecture formulated by the firstauthor and Nicolaescu. 相似文献
994.
Shuichi Haraguchi Youichi Tsuchiya Dr. Tomohiro Shiraki Dr. Kouta Sugikawa Kazuki Sada Prof. Seiji Shinkai Prof. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(42):11221-11228
π‐Conjugated polymers can finely tune their electrical and optical properties in response to their conformational changes. We believe that a deeper understanding of their higher‐order structures will stimulate further development of their applications. We had revealed that one helix‐forming natural polysaccharide (SPG) and one polythiophene derivative (PT‐1) formed a stable one‐dimensional complex and in the polythiophene main chain a helical conformation was induced through the dynamic conformational changes. The objective of our present research is to obtain a better mechanistic understanding on the interaction between SPG and polythiophenes. Here we have used particular left‐ and right‐handed helix‐forming polythiophene derivatives (D ‐ and L ‐POWTs, respectively) and studied their influence on the helical motif of the complexes. We observed that SPG interacts with both D ‐ and L ‐POWTs through their dynamic conformational changes and both D ‐ and L ‐POWTs form the right‐handed co‐helical complexes with SPG according to the inherent helical motif of SPG. In addition, it was confirmed that 1) the complexes do not coagulate in aqueous solution, and 2) the exchange in the helical motif can occur only when the polymers experience the denature–renature process. We believe, therefore, that the mechanism of the helical induction of the SPG/POWT complexes is very unique, being different from conventional equilibrium reactions. 相似文献
995.
Wannasiri Worakitkanchanakul Tomohiro Imura Tokuma Fukuoka Tomotake Morita Hideki Sakai Masahiko Abe Ratana Rujiravanit Sumaeth Chavadej Hiroyuki Minamikawa Dai Kitamoto 《Colloids and surfaces. B, Biointerfaces》2009,68(2):207-212
Due to the great importance of new therapeutic routes for morphine in pain treatment, several investigations are under development. In this way, the design of a liquid system for the oral administration of morphine would be of great help, especially in patients with difficulties in swallowing (children and elderly people). The systems studied in this work are kollidon® SR microparticles, a biodegradable polymer classically used as excipient in the design of solid dosage forms, as vehicles for morphine. A detailed investigation of the capabilities of the polymer particles to load this drug at their surface is described. Electrophoretic mobility and optical absorbance determinations were used with this aim. The main factors determining the drug incorporation, after incubation of the microparticles in the morphine solutions, were the adsorption time, the type of electrolyte and its concentration, and the drug concentration. The optimum loading conditions were used to perform morphine release evaluations, finding that the release profiles were biphasic since the drug adsorbed was slowly released during 24 h after an initial burst release phase. 相似文献
996.
Tomohiro Agou 《Journal of organometallic chemistry》2009,694(23):3833-10350
A bis(dimesitylboryl)dibenzoazaborine formed Lewis acid-base type complexes with up to two cyanide ions in stepwise fashion. The complex formation constants for cyanide ion were larger than those for fluoride ion, despite the higher affinity of fluoride ion to boron atoms than that of cyanide ion. 相似文献
997.
Toshiaki Tatsukawa Akitaka Doi Masato Teranaka Hitoshi Takashima Fuminori Goda Seishiro Watanabe Toshitaka Idehara Tomohiro Kanemaki Tunetoyo Namba 《International Journal of Infrared and Millimeter Waves》2005,26(4):591-606
Microwave invasion into living bodies through a millimeter wave catheter irradiation is described. As radiation sources for millimeter wave irradiation tests both Impatt oscillator (IO) and a Gunn oscillator were used. Irradiated samples are cow livers and living rats. A newly designed wave-guide vent antenna (WVA) with an anti-reflecting layer (ARL) is used as a launcher for the irradiation and the reflectance measurements. The correlation between the denaturation of the
tissue and the reflectance from the WVA is studied in detail. 相似文献
998.
Yasunari Monguchi Tomohiro Ichikawa Tsuyoshi Yamada Yoshinari Sawama Hironao Sajiki 《Chemical record (New York, N.Y.)》2019,19(1):3-14
Microwave‐assisted continuous‐flow reactions have attracted significant interest from synthetic organic chemists, especially process chemists from practical points of view, due to a less complicated shift to large‐scale synthesis based on simple and continuous access to products with low energy requirements. In this personal account, we focused on the Suzuki‐Miyaura and Mizoroki‐Heck reactions, both of which are significantly important cross‐coupling reactions for the synthesis of various functional materials. Microwave power is effective for heating. Typical homogeneous palladium catalysts, such as PdCl2(PPh3)2, Pd(PPh3)4, and Pd(OAc)2, as well as heterogeneous palladium catalysts, such as Pd‐film, Pd/Al2O3, Pd/SiO2, and Pd supported on polymers, can be used for these reactions. 相似文献
999.
A polystyrene‐cross‐linking tricyclohexylphosphine (PS‐TCP) was synthesized through radical emulsion polymerization of 4‐tert‐butylstyrene as a monomer and tris(trans‐4‐styrylcyclohexyl)phosphine as a threefold cross‐linker. The PS‐TCP showed enhanced ligand performance compared to the corresponding polystyrene‐triphenylphosphine hybrid PS‐TPP and tricyclohexylphosphine in Pd‐catalyzed Suzuki–Miyaura and Buchwald–Hartwig reactions of aryl chlorides. 相似文献
1000.
Tomohiro Watanabe Tristan Wagner Gangfeng Huang Jrg Kahnt Kenichi Ataka Ulrich Ermler Seigo Shima 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(11):3544-3548
[Fe]‐hydrogenase (Hmd) catalyzes the reversible hydrogenation of methenyl‐tetrahydromethanopterin (methenyl‐H4MPT+) with H2. H4MPT is a C1‐carrier of methanogenic archaea. One bacterial genus, Desulfurobacterium, contains putative genes for the Hmd paralog, termed HmdII, and the HcgA–G proteins. The latter are required for the biosynthesis of the prosthetic group of Hmd, the iron–guanylylpyridinol (FeGP) cofactor. This finding is intriguing because Hmd and HmdII strictly use H4MPT derivatives that are absent in most bacteria. We identified the presence of the FeGP cofactor in D. thermolithotrophum. The bacterial HmdII reconstituted with the FeGP cofactor catalyzed the hydrogenation of derivatives of tetrahydrofolate, the bacterial C1‐carrier, albeit with low enzymatic activities. The crystal structures show how Hmd recognizes tetrahydrofolate derivatives. These findings have an impact on future biotechnology by identifying a bacterial Hmd paralog. 相似文献