全文获取类型
收费全文 | 784篇 |
免费 | 14篇 |
国内免费 | 4篇 |
专业分类
化学 | 594篇 |
晶体学 | 7篇 |
力学 | 6篇 |
数学 | 54篇 |
物理学 | 141篇 |
出版年
2022年 | 17篇 |
2021年 | 11篇 |
2020年 | 10篇 |
2019年 | 10篇 |
2018年 | 6篇 |
2016年 | 11篇 |
2015年 | 7篇 |
2014年 | 17篇 |
2013年 | 47篇 |
2012年 | 34篇 |
2011年 | 32篇 |
2010年 | 14篇 |
2009年 | 20篇 |
2008年 | 27篇 |
2007年 | 36篇 |
2006年 | 24篇 |
2005年 | 37篇 |
2004年 | 21篇 |
2003年 | 35篇 |
2002年 | 31篇 |
2001年 | 12篇 |
2000年 | 17篇 |
1999年 | 17篇 |
1998年 | 6篇 |
1997年 | 10篇 |
1996年 | 11篇 |
1995年 | 6篇 |
1994年 | 12篇 |
1993年 | 8篇 |
1992年 | 14篇 |
1991年 | 6篇 |
1990年 | 12篇 |
1989年 | 7篇 |
1988年 | 14篇 |
1987年 | 11篇 |
1986年 | 7篇 |
1985年 | 19篇 |
1984年 | 26篇 |
1983年 | 7篇 |
1982年 | 8篇 |
1981年 | 12篇 |
1980年 | 11篇 |
1979年 | 20篇 |
1978年 | 17篇 |
1977年 | 7篇 |
1976年 | 7篇 |
1975年 | 7篇 |
1973年 | 12篇 |
1972年 | 5篇 |
1968年 | 5篇 |
排序方式: 共有802条查询结果,搜索用时 9 毫秒
51.
M Imuta H Itani H Ona Y Hamada S Uyeo T Yoshida 《Chemical & pharmaceutical bulletin》1991,39(3):663-671
The synthesis and antibacterial activity of the 1-methylcarbapenems, 2-heteroaromatic-thiomethyl and 2-carbamoyloxymethyl derivatives having a 6-[(R)-1-hydroxyethyl] side chain, are described. The introduction of a methyl substituent at the C-1 position was accomplished by a newly developed procedure using crotyl halides and zinc dust. The 2-hydroxymethyl carbapenems as key intermediates allowed an easy entry into the preparation of title carbapenems. 相似文献
52.
The negative ion mass spectra of chlorine-containing molecules have been measured using a double focusing mass spectrometer with a photographic plate detector. The formulae of the negative ions not previously assigned using an electron multiplier detector have now been assigned. 相似文献
53.
The purpose of the study was to investigate microwave selective heating phenomena and their impact on heterogeneous chemical reactions. We also present a tool which will help microwave chemists to answer to such questions as "My reaction yields 90% after 7 days at reflux; is it possible to obtain the same yield after a few minutes under microwaves?" and to have an approximation of their reactions when conducted under microwaves with different heterogeneous procedures. This model predicting reaction kinetics and yields under microwave heating is based on the Arrhenius equation, in agreement with experimental data and procedures. 相似文献
54.
Wafaa S. Hamama Hamada G. El‐Gohary Mamdouh Soliman Hanfi H. Zoorob 《Journal of heterocyclic chemistry》2012,49(3):543-554
This research work describes the synthesis and biological properties of some novel isolated or fused heterocyclic ring systems with pyrazole, for example; enaminones containing pyrazolone ring photochromic functional unit, 4‐[(4‐chlorophenylamino)methylene]‐3‐methyl‐1‐phenyl‐1H‐pyrazol‐5(4H)‐one (3) and some analogous derivatives 4, 9, and 10, also as pyrazolo[3,4‐b]pyridine, pyrazolo[3,4‐b]quinoline, pyrazolo[3′,4′:4,5]thieno[2,3‐c]pyrazoline and pyrazolo[3,4‐c]pyrazole were synthesized and characterized. Newly synthesized compounds were characterized by IR, 1H NMR, 13C NMR, mass spectral data and quantum mechanical calculations. Selected products were tested for their antibacterial and antitumor agents. 相似文献
55.
Tatsuro Ouchi Hidetake Miyazaki Hidetoshi Arimura Fumitaka Tasaka Atsushi Hamada Yuichi Ohya 《Journal of polymer science. Part A, Polymer chemistry》2002,40(10):1426-1432
Amphiphilic AB‐type diblock copolymers composed of hydrophobic poly(L ‐lactide) (PLA) segments and hydrophilic poly(glycolic acid lysine) [poly(Glc‐Lys)] segments with amino side‐chain groups self‐associated to form PLA‐based polymeric micelles with amino surfaces in an aqueous solution. The average diameter of the loose core–shell polymeric micelles for poly(Glc‐Lys) [number‐average molecular weight (Mn) = 1240]‐b‐PLA (Mn = 7000) obtained by a dimethyl sulfoxide/water dialysis method was estimated to be about 50 nm in water by dynamic light scattering measurements. The size and shape of the obtained polymeric micelles were further observed with transmission electron microscopy and atomic force microscopy. To investigate the possibility of applying the obtained PLA‐based polymeric micelles as bioabsorbable vehicles for hydrophobic drugs, we tested the entrapment of drugs in poly(Glc‐Lys) (Mn = 1240)‐b‐PLA (Mn = 7000) micelles and their release with doxorubicin as a hydrophobic drug. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1426–1432, 2002 相似文献
56.
57.
Chizuko Kabuto Yutaka Higuchi Tomohiro Niimi Fumio Hamada Nobuhiko Iki Naoya Morohashi Sotaro Miyano 《Journal of inclusion phenomena and macrocyclic chemistry》2002,42(1-2):89-98
X-Ray crystal structures of the mono-, di-, and tri(p-tert-butyl)-substituted thiacalix[4]arenes (TC4As; 1, 2, and 3, respectively) have beendetermined. TC4As 1–3 adopt a cone conformation and form dimeric self-inclusion units in such a manner that phenol moieties are inserted into the cavity of each molecule. In all the crystal structures of 1–3, lateralface-to-face interactions exist between the phenol rings that do not bear a tert-butyl substituent, and seemingly, this molecular assembly stabilizes the formation of self-inclusion. TC4As 1 and 2 adopt a cone conformation with C2 symmetry, leading to the formation of rim-to-rim intermolecular hydrogenbonds so as to link the dimeric units up and down. On the other hand, 3 adopts a regular cone conformation with C4 symmetry to form cyclic hydrogen bonds withinthe rim part of TC4A. 相似文献
58.
Tomoshige Morita Takeshi Hamada Koji Ishida 《Fresenius' Journal of Analytical Chemistry》1981,309(5):377-379
Summary The TLC behaviour of Rh(III), Ir(III) and Ir(IV) has been investigated in the two systems consisting of DEAE-cellulose or ECTEOLA-cellulose and 5 M HCl media containing H2O2. These systems, especially in combination with a simple chemical pretreatment of samples (with LiCl, HCl and H2O2), can effectively be applied to the complete separation of mixtures of Rh(III) and Ir(III) or Ir(IV) in a wide range of ratios and amounts (Rh: Ir=1100 to 1001).
Dünnschicht-chromatographische Trennung von Rhodium(III) und Iridium(III, IV) durch Anionenaustausch
Zusammenfassung Das dünnschicht-chromatographische Verhalten von Rh(III), Ir(III) und Ir(IV) wurde in H2O2-haltiger 5 M salzsaurer Lösung auf DEAE-sowie ECTEOLA-Cellulose untersucht. In Kombination mit einer einfachen chemischen Vorbehandlung der Probe (mit LiCl, HCl, H2O2) kann eine wirkungsvolle Trennung von Rh(III) und Ir(III) oder Ir(IV) über einen weiten Konzentrationsbereich erzielt werden (Rh: Ir=1100 bis 1001).相似文献
59.
K. Hamada T. Wada C. Guet 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,23(3):359-368
Stability of highly charged metal clusters in the electric field of an external ion is investigated with the classical liquid
drop model. We study the optimum shape of the cluster which has a local minimum of the total energy, taking account of the
effects of the surface charge polarization on the Coulomb energy and the cluster deformation on the surface energy. We find
that the cluster deformation greatly affects the total energy of the system and that a cluster with a fissility larger than
some critical value 0.7-0.8 can become unstable against deformation. We investigate the local competition between the Coulomb
force and the surface tension at the cluster surface and show that the surface charge polarization which is induced by the
external electric field significantly affects the shape of the cluster and its stability.
Received 5 November 2002 / Received in final form 27 January 2003 Published online 11 March 2003
RID="a"
ID="a"e-mail: hamada@konan-u.ac.jp 相似文献
60.
When binaural sound signals are presented with two loudspeakers, the listener's ears are required to be in the relatively small region which is under control of the system. Misalignment of the head results in inaccurate synthesis of the binaural signals. Consequently, directional information associated with the acoustic signals is inaccurately reproduced. When the two loudspeakers are placed close together, the spatial rate of change of the generated sound field is much smaller than that generated by two loudspeakers spaced apart. Therefore, the performance of such a system is expected to be more robust to misalignment of the listener's head. Robustness of performance is investigated here with respect to head displacement in three translational and three rotational directions. A comparison is given between systems consisting of two loudspeakers either placed close together or spaced apart. The extent of effective control with head displacement and the resulting deterioration in directional information is investigated in the temporal and spectral domain by analyzing synthesized binaural signals. Subjective localization experiments are performed for cases in which notable differences in performance are expected from the previous analysis. It is shown that the system comprising two loudspeakers that are close together is very robust to misalignment of the listener's head. 相似文献