全文获取类型
收费全文 | 1191篇 |
免费 | 16篇 |
国内免费 | 9篇 |
专业分类
化学 | 810篇 |
晶体学 | 12篇 |
力学 | 21篇 |
数学 | 71篇 |
物理学 | 302篇 |
出版年
2020年 | 6篇 |
2019年 | 13篇 |
2018年 | 17篇 |
2017年 | 11篇 |
2016年 | 11篇 |
2015年 | 13篇 |
2014年 | 23篇 |
2013年 | 44篇 |
2012年 | 49篇 |
2011年 | 77篇 |
2010年 | 38篇 |
2009年 | 33篇 |
2008年 | 67篇 |
2007年 | 58篇 |
2006年 | 67篇 |
2005年 | 67篇 |
2004年 | 58篇 |
2003年 | 50篇 |
2002年 | 45篇 |
2001年 | 32篇 |
2000年 | 27篇 |
1999年 | 20篇 |
1998年 | 11篇 |
1997年 | 16篇 |
1996年 | 9篇 |
1995年 | 14篇 |
1994年 | 23篇 |
1993年 | 17篇 |
1992年 | 18篇 |
1991年 | 19篇 |
1990年 | 18篇 |
1989年 | 13篇 |
1988年 | 7篇 |
1987年 | 11篇 |
1986年 | 19篇 |
1985年 | 20篇 |
1984年 | 18篇 |
1983年 | 11篇 |
1982年 | 15篇 |
1981年 | 17篇 |
1980年 | 15篇 |
1979年 | 13篇 |
1978年 | 7篇 |
1977年 | 16篇 |
1976年 | 8篇 |
1975年 | 5篇 |
1974年 | 9篇 |
1973年 | 12篇 |
1972年 | 5篇 |
1967年 | 3篇 |
排序方式: 共有1216条查询结果,搜索用时 15 毫秒
11.
Tetrakis-acridinyl peptide 1 assuming a right-handed helical stacked conformation of the acridinyl units can bind to DNA duplex with a very high affinity of 10(8) (M-bp)(-1) even at a high salt concentration of 0.2 M NaCl, irrespective of the base composition. Peptide 1 gave rise to 1600-times enhancement of its fluorescence upon binding to an AT polymer due to the collapse of this stacked structure, but the fluorescence is not enhanced with a GC polymer, though the binding constants of 1 for both polymers were the same. 相似文献
12.
A. Nakaoka H. Yokoyama M. Fukushima S. Takagi 《Journal of Radioanalytical and Nuclear Chemistry》1980,56(1-2):13-24
A rapid and precise method of determining radiocesium corresponding to 5 mrem/y, the Japan AEC's guideline, was proposed.
The development and practical performance of cesium-selective resin and the determination method was described in this paper.
The resin was prepared by the formation of ammonium molybdophosphate in the structure of Amberlite XAD-7 resin. It took only
3 hours to carry out all the procedures the authors proposed. This value represents 1/10∼1/2 of the time of conventional method.
The concentration of137Cs and134Cs in sea water was determined to be 0.13∼0.16 pCi/1 and less than 7.1·10−2 pCi/1, respectively. 相似文献
13.
14.
15.
Kiyotake Suenaga Tsuyoshi Mutou Takashi Itoh Noboru Takada Masaki Takagi Hideo Kigoshi Kiyoyuki Yamada 《Tetrahedron》2004,60(38):8509-8527
The bioassay-guided fractionation of the cytotoxic constituents of the Japanese sea hare Dollabella auricularia led to the isolation of aurilide (1), a 26-membered cyclodepsipeptide. The gross structure of 1 was established by spectroscopic analysis including 2D NMR techniques. The absolute stereostructure was determined by chiral HPLC analysis of acid hydrolysates of 1 and by the enantioselective synthesis of a degradation product arising from a dihydroxylated fatty acid portion. The enantioselective synthesis of 1 was achieved in 12% overall yield (16 steps) and confirmed the absolute stereostructure of 1. The cytotoxicity of 1 was evaluated using a synthetic sample, which was found to exhibit potent cytotoxicity against HeLa S3 cells with an IC50 of 0.011 μg/mL. Further biological and pharmacological studies of 1 have been carried out by using synthetic 1. 相似文献
16.
We have purified a factor, hematopoietic promoting factor (HPF), from porcine kidney extract (PKE), which exhibits a promoting activity on granulocyte/macrophage (GM) colony and burst-forming-unit-erythroid (BFU-E)-derived colony formation by progenitors from murine bone marrow cells in vitro. The addition of HPF resulted in an enhancement of the GM colonies as well as BFU-E-derived colonies, but did not enhance the colony-forming-unit-erythroid (CFU-E)-derived colony formation. HPF was added to the BFU-E cultures together with cytokines, such as recombinant murine interleukin-3 (IL-3), recombinant murine GM colony-stimulating-factor (GM-CSF) and recombinant human G-CSF, which have all been shown to enhance BFU-E growth. The combination of HPF plus these cytokines resulted in an enhancement of benzidine negative colony formation in comparison to the case of each cytokine alone; however, no increase was found on BFU-E colony formation. HPF is able to enhance the granulopoiesis and erythropoiesis in vitro. And the synergistic activity of HPF is significantly affected by the presence of cytokines in the cultures. 相似文献
17.
Shibuya H Kitamura C Maehara S Nagahata M Winarno H Simanjuntak P Kim HS Wataya Y Ohashi K 《Chemical & pharmaceutical bulletin》2003,51(1):71-74
The microbial transformation of four Cinchona alkaloids (quinine, quinidine, cinchonidine, and cinchonine) by endophytic fungi isolated from Cinchona pubescens was investigated. The endophytic filamentous fungus Xylaria sp. was found to transform the Cinchona alkaloids into their 1-N-oxide derivatives. 相似文献
18.
Konda-Yamada Y Asano K Satou T Monma S Sakayanagi M Satou N Takeda K Harigaya Y 《Chemical & pharmaceutical bulletin》2005,53(5):529-536
Oxopropyl E-(pyrrolidine-2-ylidene)glycinamide (5c) and allyl E-(pyrrolidine-2-ylidene)glycinate (5d) were effectively synthesized from 2,3,5-tri-O-benzyl-4-O-tert-butyldimethylsilyl(TBDMS)-D-arabinal (7) using intramolecular 1,3-dipolar cyclic reaction of azide and olefin as a key reaction. These results proved this cyclic reaction should be applicable for the synthesis of various (pyrrolidine-2-ylidene)glycinate and glycinamide. In addition, the development of a synthetic route for the precursor of an unsaturated cyclic dehydro amino acid involved in azinomycins (carzinophilin) using relating glycinate, methyl E-(pyrrolidine-2-ylidene)glycinate (5a) was described. 相似文献
19.
Itsuki Shindachi Hiroshi Hanaki Ryo Sasai Tetsuya Shichi Tatsuto Yui Katsuhiko Takagi 《Research on Chemical Intermediates》2007,33(1-2):143-153
Diarylethene derivatives (DE) covalently bonded to silanol oxygens of layered silicate surfaces, i.e., magadiite (Mag), were synthesized and investigated for their photochromic behavior. The DE-Mag layered hybrids were found to undergo reversible color change by alternating UV and visible light irradiation. A more highly efficient, reproducible photochromic behavior was realized with DE-Mag than with a corresponding DE-Si possessing silyl substituents on DE in place of the Mag surface. Moreover, the present covalently bonded DE exhibited an improvement over DE hybrids incorporated in layered double hydroxide (LDH) clays, in which the repetitive photochromic behavior decreased during alternating irradiation, due to the accumulation of the photochemically inert parallel isomers of DE. 相似文献
20.
Yan Ouyang Wei Zhang Yue Ma Na Xu Dai-Zheng Liao Kazuyoshi Yoshimura Shi-Ping Yan 《Structural chemistry》2007,18(6):891-898
Two new tetranuclear complexes of macrocyclic oxamide [Cd(CuL)3](NO3)2·2.5H2O 1, [Mn(CuL)3(OH)2](ClO4)2·Mn(H2O)6·4.5H2O 2 (L = 1,4,8,11-tatraazacyclotradecanne-2,3-dione) have been synthesized, structurally characterized and preliminary investigated
by magnetic studies. The structures of the title complexes consist of a tetranuclear units MCu3 (M = Cd, Mn), the packing diagram shows two-dimensional and three-dimensional system through intermolecular weak interactions.
The temperature-dependent magnetic susceptibilities of complex 2 were analyzed by an approximate treatment leading to J = −33 cm−1, gCu = 2.10, gMn = 1.95 indicating antiferromagnetic exchange between Cu(II) and Mn(II) ions. 相似文献