全文获取类型
收费全文 | 3107篇 |
免费 | 86篇 |
国内免费 | 13篇 |
专业分类
化学 | 2414篇 |
晶体学 | 47篇 |
力学 | 25篇 |
数学 | 64篇 |
物理学 | 656篇 |
出版年
2021年 | 25篇 |
2020年 | 20篇 |
2019年 | 31篇 |
2018年 | 18篇 |
2017年 | 22篇 |
2016年 | 49篇 |
2015年 | 46篇 |
2014年 | 53篇 |
2013年 | 107篇 |
2012年 | 160篇 |
2011年 | 182篇 |
2010年 | 95篇 |
2009年 | 104篇 |
2008年 | 166篇 |
2007年 | 176篇 |
2006年 | 162篇 |
2005年 | 176篇 |
2004年 | 156篇 |
2003年 | 137篇 |
2002年 | 108篇 |
2001年 | 104篇 |
2000年 | 77篇 |
1999年 | 70篇 |
1998年 | 38篇 |
1997年 | 41篇 |
1996年 | 34篇 |
1995年 | 32篇 |
1994年 | 27篇 |
1993年 | 28篇 |
1992年 | 43篇 |
1991年 | 32篇 |
1990年 | 38篇 |
1989年 | 30篇 |
1988年 | 21篇 |
1987年 | 36篇 |
1986年 | 20篇 |
1985年 | 39篇 |
1984年 | 40篇 |
1983年 | 21篇 |
1982年 | 39篇 |
1981年 | 44篇 |
1980年 | 32篇 |
1979年 | 49篇 |
1978年 | 28篇 |
1977年 | 27篇 |
1976年 | 17篇 |
1975年 | 22篇 |
1974年 | 23篇 |
1973年 | 25篇 |
1972年 | 21篇 |
排序方式: 共有3206条查询结果,搜索用时 15 毫秒
931.
Cyano2Dbase updated: linkage of 234 protein spots to corresponding genes through N-terminal microsequencing. 总被引:8,自引:0,他引:8
The cyanobacterium Synechocystis sp. strain PCC6803 is an interesting model organism for preoteome study because it is a photosynthetic procaryote and its genomic sequence has already been determined at our institute. We thus initiated characterization of this organism from a proteomic viewpoint by exploiting two-dimensional (2-D) gel electrophoresis coupled with N-terminal protein sequencing. In a previous study, we linked 130 protein spots on two dimensional gels with the genes that encoded them. As an extension of the previous study, the number of protein spots linked to their corresponding genes was increased to 227 in this study by separately analyzing cyanobacterial proteins in four different fractions (soluble, insoluble, thylakoid membrane, and secretory protein fractions). The resultant updated 2-D protein-gene linkage database, named Cyano2Dbase, will serve as an indispensable tool in future cyanobacterial proteomic studies. From the data compiled in the Cyano2Dbase, we can extract many items of information concerning translation, posttranslational processing including characteristics of cyanobacterial signal sequences and modification of cyanobacterial proteins. The Cyano2Dbase is available to the public through the World Wide Web (http://www.kazusa.or.jp/tech/sazuka/cyano/pr oteome.html). 相似文献
932.
933.
934.
935.
936.
Ryo Yoshida Hisao Ichijo Toshikatsu Hakuta Tomohiko Yamaguchi 《Macromolecular rapid communications》1995,16(4):305-310
Novel gel systems demonstrating rhythmically pulsatile mechanical motion similar to that of a heartbeat were developed. Self-oscillations of swelling and deswelling for the polymer hydrogels were realized by coupling pH and temperature sensitive hydrogels with a non-linear chemical reaction in the external solution media. The novel gel dynamics exhibiting cyclic and rhythmical oscillations may establish a new concept for functional materials that work under dynamic oscillating states. 相似文献
937.
The effects of protonation on the excited states oftrans-3-styrylpyridine (StP) andtrans-4,4′-dipyridylethylene (DPE) have been studied through measurements of the time-resolved electron paramagnetic resonance (EPR), ultraviolet absorption, and fluorescence spectra in methanol-water mixtures at 77 K. The assignment of the transient EPR signals was carried out with the aid of the stretched poly(vinyl alcohol) films method. From the analysis of these spectra it is concluded that the single protonation appears to have little effect on the zero-field splitting parameters and the anisotropy in the sublevel populating rates of the lowest excited triplet (T1) states of StP and DPE. However, the decay rate constants of the fluorescent states decrease and fluorescence quantum yields increase on single protonation. These experimental results suggest that the single protonation causes a decrease in the intersystem crossing (ISC) rates for the three T1 sublevels. These results are explained in terms of the vibronic mixing between the1nπ* and1ππ* states in the lowest excited singlet state. The assignment of StP to the specified conformer was carried out through the analysis of the anisotropic ISC processes. 相似文献
938.
J.R. Goldman T.D. Ladd F. Yamaguchi Y. Yamamoto 《Applied Physics A: Materials Science & Processing》2000,71(1):11-17
A quantum computer using nuclear spins in a crystal lattice requires a method for addressing individual quantum bits. This identification can be achieved with a spatially varying magnetic field. Spins at different lattice sites can have distinguishable Zeeman frequencies allowing initialization, logic operations, and measurements to be performed through radio frequency (rf) pulse techniques. Here, we present magnet designs that have gradients between 1 and 20 T/7m, which are necessary to realize quantum computation with particular crystals. 相似文献
939.
In image reconstruction for X-ray computed tomography, images reconstructed by filtered backprojection (FBP) include systematic errors because the FBP method does not take into account some of the properties of the actual imaging system such as the divergence of X-ray beam. One solution to this problem is to use algebraic reconstruction methods, such as generalized analytic reconstruction from discrete samples and natural pixel decomposition. However, in the process of reconstruction using these methods, it is necessary to solve the linear algebraic equations which have a large coefficient matrix. In this paper, we propose a method to accelerate the iteration solving these equations by preconditioning the coefficient matrix using a polynomial function. The results of the computer simulations show the effectiveness of the proposed method. 相似文献
940.
Munetaka Ohkouchi Dai Masui Motowo Yamaguchi Takamichi Yamagishi 《Journal of molecular catalysis. A, Chemical》2001,170(1-2):1-16
Silver(I)-diphosphine complex is an effective catalyst for Mukaiyama Aldol reaction in polar solvents. AgPF6-(S)-BINAP cationic chiral complex indicated a good activity and could afford fairly high enantioselectivity in the reaction of aromatic aldehydes and silyl enol ethers. On the other hand, AgOAc-(S)-BINAP system afforded the aldol product of the absolute configuration opposite to that by AgPF6-(S)-BINAP and very high catalytic activity was shown. The structure and equilibrium state of Ag(I)-BINAP complexes in solution were examined to understand the reaction mechanism. In AgPF6 system [Ag((S)-BINAP)2]PF6 (1a), [Ag((S)-BINAP)]PF6 (1b), [Ag2((S)-BINAP)](PF6)2 (1c) and AgPF6 are present in solution. The active species of the aldol reaction in DMF is [Ag((S)-BINAP)]PF6 (1b), which exists as a minor species in solution. For this cationic Ag(I) catalyst, cyclic transition state containing substrate and silyl enol ether is assumed. In AgOAc-(S)-BINAP system, active species is also monomeric AgOAc((S)-BINAP) (2b) species which exists as a major component in solution and strong interaction was observed with a silyl enol ether. The reaction by AgOAc-(S)-BINAP catalyst is concluded to proceed as follows: nucleophile forms a complex with AgOAc-(S)-BINAP species and is activated. This complex attacks aldehydes to afford aldol adduct via acyclic transition state. 相似文献