全文获取类型
收费全文 | 6526篇 |
免费 | 733篇 |
国内免费 | 797篇 |
专业分类
化学 | 7126篇 |
晶体学 | 20篇 |
力学 | 34篇 |
综合类 | 75篇 |
数学 | 59篇 |
物理学 | 742篇 |
出版年
2024年 | 7篇 |
2023年 | 93篇 |
2022年 | 137篇 |
2021年 | 220篇 |
2020年 | 277篇 |
2019年 | 260篇 |
2018年 | 187篇 |
2017年 | 213篇 |
2016年 | 286篇 |
2015年 | 312篇 |
2014年 | 344篇 |
2013年 | 447篇 |
2012年 | 610篇 |
2011年 | 441篇 |
2010年 | 433篇 |
2009年 | 458篇 |
2008年 | 485篇 |
2007年 | 512篇 |
2006年 | 485篇 |
2005年 | 426篇 |
2004年 | 306篇 |
2003年 | 265篇 |
2002年 | 186篇 |
2001年 | 132篇 |
2000年 | 98篇 |
1999年 | 108篇 |
1998年 | 62篇 |
1997年 | 65篇 |
1996年 | 41篇 |
1995年 | 49篇 |
1994年 | 26篇 |
1993年 | 16篇 |
1992年 | 16篇 |
1991年 | 11篇 |
1990年 | 9篇 |
1989年 | 5篇 |
1988年 | 3篇 |
1987年 | 2篇 |
1986年 | 4篇 |
1985年 | 3篇 |
1984年 | 3篇 |
1983年 | 3篇 |
1980年 | 2篇 |
1979年 | 1篇 |
1978年 | 2篇 |
1973年 | 2篇 |
1969年 | 3篇 |
排序方式: 共有8056条查询结果,搜索用时 171 毫秒
101.
The paper represents a further development of our hydrate hypothesis of simplest living matter origination (SLMO) from inorganic and simplest organic mineral substances. It is supposed that the sources of SLMO are simplest aliphatic hydrocarbons, niters, and phosphates. Thermodynamic calculations demonstrating a principal possibility for simultaneous syntheses of different nitrogen bases, d-ribose, and desoxy-d-ribose from these source substances are presented. The most probable principal mechanism of SLMO and the principal conditions necessary for realization of the proposed chemism of SLMO in the framework of the proposed mechanism are considered. A principal means for testing the hypothesis is proposed. 相似文献
102.
Determination of DNA using sodium 9,10-anthraquinone-2-sulfonate as an in situ photochemical fluorescence probe 总被引:2,自引:0,他引:2
Wen-You Li Xiang-Qun Guo Jin-Gou Xu Qing-Zhi Zhu Yi-Bing Zhao 《Analytica chimica acta》1997,340(1-3):291-296
An in situ photochemical fluorescence probe method for the determination of DNA with sodium 9,10-anthraquinone-2-sulfonate (AQS) as a photochemical fluorescence probe was developed. It was based on the conversion of AQS into an intensively fluorescent product by irradiating with UV radiation. The photochemical reaction is retarded by DNA. The determination can be carried out by measuring the fluorescence intensity at a fixed time. The calibration graph was linear in the range 0–80 ng ml−1 calf thymus (CT) DNA (r = 0.9991), the limit of detection was 3.2 ng ml−1 CT DNA (n = 9). The kinetic behaviour of the photochemical reaction and the effects of experimental conditions were investigated and discussed in detail. The results of absorption spectra and competitive binding experiments suggested the interaction between AQS and DNA to be intercalative. 相似文献
103.
E. A. Belousova V. V. Koval N. I. Rechkunova S. Kh. Degtyarev O. S. Fedorova O. I. Lavrik 《Russian Chemical Bulletin》2005,54(5):1306-1310
The interaction of DNA polymerase Tte from Thermus thermophilus B35 with dUTP analog containing a fluorescein residue bound to C(5) of the base (Flu-dUTP) was studied by fluorescence titration.
The dissociation constants of the enzyme—substrate complexes in the absence and in the presence of a DNA duplex containing
an extended template and bivalent metal ions and the kinetic parameters of polymerization by DNA polymerase Tte in the presence of Flu-dUTP were determined.
__________
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 1268–1272, May, 2005. 相似文献
104.
Fernando Ferreira 《Tetrahedron letters》2004,45(33):6287-6290
Oligonucleotides protected with N-(trimethylsilylethoxycarbonyl) (Teoc) and P-(trimethylsilylethanol) (Tse) groups were synthesized and deprotected by a single ZnBr2 treatment. Teoc group stabilized dA against depurination. This strategy was applied to the synthesis of base-sensitive oligonucleotide prodrugs bearing S-acetyl-2-thioethyl (Sate) phosphotriesters. 相似文献
105.
106.
In the absence of any special luminescence reagent, emission of weak chemiluminescence has been observed during the decomposition of hydrogen peroxide catalyzed by copper(II) in basic aqueous solution. The intensity of the chemiluminescence was greatly enhanced by addition of DNA and was strongly dependent on DNA concentration. Based on these phenomena, a flow-injection chemiluminescence method was established for determination of DNA. The chemiluminescence intensity was linear with DNA concentration in the range 2×10–7–1×10–5 g L–1 and the detection limit was 4.1×10–8 g L–1 (S/N=3). The relative standard deviation was less than 3.0% for 4×10–7 g L–1 DNA (n=11). The proposed method was satisfactorily applied for determination of DNA in synthetic samples. The possible mechanism of the CL reaction is discussed. 相似文献
107.
IDENTIFICATION OF PARTIAL MUTATIONAL SITES IN HUMAN MITOCHONDRIAL DNA IN THE CHINESE AND ITS SIGNIFICANCE 总被引:1,自引:0,他引:1
A simple method for the identification of mutational sites in human mitochondrial DNA (mtDNA) was described. It was based on the human Cambridge sequence as a relative standard sequence and a single base pair substitution in mtDNA as a unique mutational form. The partial mutational sites can be determined using this method which was characterized by combining the restriction mapping with the analysis for the table of human mtDNA potential mutational sites with rapidity and simplicity. In the meanwhile, six mtDNA mutational sites found in Chinese population were identified by means of this method. 相似文献
108.
The complete gene coding for human neutrophilactivating protein-1/interleukin-8 was synthesized using a semi-chemical semi-enzymatic method. The synthetic gene was then overexpressed in Escherichia coli under the temperature-regulated control of the P_RP_L tandem promoters. As determined by SDS-PAGE and densitometry, the overexpressed protein comprised up to 18.5% and 10.9% of the total soluble protein in E. coli cells grown in shake flasks and in batch fermentation, respectively. The recombinant NAP-1/IL-8 was then purified to>95% homogeneity by gel filtration and cation exchange chromatography. The purified protein appeared as a single band on the SDS-PAGE gel and possessed potent chemotactic activity in the concentration of <10 ng/ml, as assayed by the agarose plate method. An early skin reactivity was also observed when the pure NAP-1/IL-8 was injected subcutaneously into the rabbits. The N-terminal 36 amino acid sequence of the recombinant NAP1/IL-8 was determined using the Edman method and was sho 相似文献
109.
Weiping Wang Bo Liao Tianming Wang Wen Zhu 《International journal of quantum chemistry》2006,106(9):1998-2005
A 3D graphical representation of DNA sequences, which has no circuit or degeneracy, is derived for mathematical denotation of DNA sequence. Based on this graphical representation, we propose a new sequence distance measure. We make use of the corresponding similarity matrix to construct a phylogenic tree by virtue of the fuzzy theory. The examination of phylogenic tree belong to eight species illustrates the utility of our approach. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2006 相似文献
110.