全文获取类型
收费全文 | 11648篇 |
免费 | 2155篇 |
国内免费 | 1385篇 |
专业分类
化学 | 8026篇 |
晶体学 | 162篇 |
力学 | 834篇 |
综合类 | 117篇 |
数学 | 1263篇 |
物理学 | 4786篇 |
出版年
2024年 | 6篇 |
2023年 | 290篇 |
2022年 | 313篇 |
2021年 | 478篇 |
2020年 | 510篇 |
2019年 | 512篇 |
2018年 | 423篇 |
2017年 | 384篇 |
2016年 | 615篇 |
2015年 | 578篇 |
2014年 | 698篇 |
2013年 | 829篇 |
2012年 | 1088篇 |
2011年 | 1071篇 |
2010年 | 812篇 |
2009年 | 744篇 |
2008年 | 726篇 |
2007年 | 636篇 |
2006年 | 663篇 |
2005年 | 574篇 |
2004年 | 380篇 |
2003年 | 328篇 |
2002年 | 317篇 |
2001年 | 233篇 |
2000年 | 218篇 |
1999年 | 214篇 |
1998年 | 182篇 |
1997年 | 200篇 |
1996年 | 176篇 |
1995年 | 162篇 |
1994年 | 137篇 |
1993年 | 97篇 |
1992年 | 85篇 |
1991年 | 79篇 |
1990年 | 76篇 |
1989年 | 68篇 |
1988年 | 52篇 |
1987年 | 29篇 |
1986年 | 44篇 |
1985年 | 32篇 |
1984年 | 18篇 |
1983年 | 16篇 |
1982年 | 15篇 |
1981年 | 7篇 |
1980年 | 9篇 |
1975年 | 7篇 |
1973年 | 4篇 |
1972年 | 7篇 |
1965年 | 6篇 |
1964年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 531 毫秒
991.
Qiang Wang Guibiao Jin Xuerong Fan Xianfei Zhao Li Cui Ping Wang 《Applied biochemistry and biotechnology》2010,160(8):2486-2497
ε-Poly-l-lysine (ε-PL), a natural biomacromolecule having a broad spectrum of antibacterial activity, was grafted on the wool fiber
via the acyl transfer reaction catalyzed by microbial transglutaminase (mTGase) to develop a new strategy for antibacterial
functionalization of proteinous materials. The effects of the concentrations of ε-PLs and mTGases on the graft yields were
investigated. A coating of ε-PL that almost completely covered the scale profile on the wool surface was visualized by scanning
electron microscopy (SEM) and further demonstrated in terms of Allw?rden’s reaction characteristic of wool. Identifiable differences
in lysine content and color depth among the stained wool samples reveal the changes in the surface composition and polarity
caused by the incorporation of ε-PL onto the wool substrate, respectively. The ratio of bacteriostasis to Escherichia coli of the wool fabric grafting ε-PL reached 96.6 %, indicating an excellent antibacterial effect. The application of ε-PL and
corresponding mTGase-catalyzed grafting reaction would provide a worthwhile reference for antibacterial functionalization
of proteinous materials in various forms. 相似文献
992.
A DNA fragment containing the entire coding sequence of nitrilase gene was amplified from Rhodococcus rhodochrous tg1-A6 with high nitrilase activity using PCR and sequenced. The open reading frame of the nitrilase gene contains 1,101 base
pairs, which encodes a putative polypeptide of 366 amino acid residues. The nitrilase gene was cloned into an expression vector
pET-28a and expressed in an Escherichia coli strain BL21(DE3). The enzymatic activity of nitrilase, which converts various nitriles to the corresponding carboxylic acids,
was detected to reach 24.5 U/ml at 9 h in the recombinant bacteria. 相似文献
993.
Jing-An Zhang Mei Pan Rui Yang Zhi-Gang She Wolfgang Kaim Zhi-Jin Fan Cheng-Yong Su 《Polyhedron》2010
The semirigid tridentate 8-(2-pyridinylmethylthio)quinoline ligand (Q1) is shown to form the structurally characterized transition metal complexes [Cu(Q1)Cl2] (1), [Co(Q1)(NO3)2] (2), [Cd(Q1)(NO3)2] (3), [Cd(Q1)I2] (4). [Cu(Q1)2](BF4)2·(H2O)2 (5), [Cu(Q1)2](ClO4)2·(CH3COCH3)2 (6), [Zn(Q1)2](ClO4)2(H2O)2 (7), [Cd2(Q1)2Br4] (8), [Ag2(Q1)2(ClO4)2] (9), and [Ag2(Q1)2(NO3)2] (10). Four types of structures have been observed: ML-type in complexes 1–4, in which the anions Cl−, NO3− or I− also participate in the coordination; ML2− type in complexes 5–7 without direct coordination of the anions BF4− or ClO4− and with more (Cu2+) or less (Zn2+) distorted bis-fac coordinated Q1; M2L2-type in complex 8, in which two Br− ions act as bridges between two metal ions; and M2(μ-L)2-type in complexes 9 and 10, in which the ligand bridges two anion binding and Ag–Ag bonded ions. Depending on electron configuration and size, different coordination patterns are observed with the bonds from the metal ions to Npyridyl longer or shorter than those to Nquinoline. Typically Q1 acts as a facially coordinating tridentate chelate ligand except for the compounds 9 and 10 with low-coordinate silver(I). Except for 6 and 8, the complexes exhibit distinct constraining effects against both G(+) and G(-) bacteria. Complexes 1, 3, 4, 5, 7 have considerable antifungal activities and complexes 1, 5, 7, and 10 show selective effects to restrain certain botanic bacteria. Electrochemical studies show quasi-reversible reduction behavior for the copper(II) complexes 1, 5 and 6. 相似文献
994.
Five new 0D–2D Cd(II) complexes, [Cd2(Hbimt)2I4] (1), [Cd(bimt)(Hbimt)Br]n (2), [Cd(Hbimt)Cl2(H2O)]n (3), {[Cd(Hbimt)(SO4)(H2O)2]·1.5H2O}n (4) and [Cd(Hbimt)(SCN)2]n (5) (Hbimt = 2-((benzoimidazol-yl)methyl)-1H-tetrazole) have been synthesized by the reactions of Hbimt with suitable cadmium salts. Employment of different anions can influence the coordination modes of the Hbimt ligand, and accordingly result in different structures ranging from 0D to infinite 1D and 2D networks. Complex 1 displays a dimeric structure in which two Cd(II) ions are bridged through two iodine atoms. Complex 2 was caused by deprotonation of the Hbimt ligand, resulting in a 1D helical chain. While in complexes 3 and 4, Hbimt acts as a bidentate bridging ligand which joins two Cd(II) ions, leading to 1D stair-like chains. Complex 5 exhibits a 2D network structure with infinite 1D [Cd2(SCN)2]n chains. The distinct structures of 1, 2, 3, 4 and 5 reveal that the anions and the versatile coordination modes of the ligand play an important role in the structures of the complexes. In addition, the luminescent properties of complexes 1–5 have been investigated in the solid state at room temperature. 相似文献
995.
996.
Chiral and racemic Salen-type Schiff-base ligands (H2L1, H2L2 and H2L3), condensed between D-(+)- and D,L-camphoric diamine (also known as (1R,3S)-1,2,2-trimethylcyclopentane-1,3-diamine) and 2-hydroxybenzaldehyde or 3,5-dibromo-2-hydroxybenzaldehyde with a 1:2 molar ratio, have been synthesized and characterized. A series of new nickel(II), palladium(II) and copper(II) complexes of these chiral and racemic ligands exhibiting different coordination number (4, 5 and 6) have been characterized with the formulae [NiL1]·CH3OH (3), [NiL1]·H2O (4), [NiL2] (5), [PdL2] (6), [Cu2(L2)2(H2O)] (7) and [NiL3(DMF)(H2O)] (8). Different solvent molecules in 3 and 4 (methanol and water molecules) as well as different apical ligands in 7 and 8 (water and DMF molecules) are involved in different O–H···O hydrogen bonding interactions to further stabilize the structures. UV–Vis (UV–Vis), circular dichroism (CD) spectra and thermogravimetric (TG) analyses for the metal complexes have also been carried out. 相似文献
997.
Shuangyin Wang Fan Yang San Ping Jiang Shengli Chen Xin Wang 《Electrochemistry communications》2010,12(11):1646-1649
Polyelectrolytes with various characteristic functional groups as interlinkers to anchor Pt nanoparticles were used to functionalize carbon nanotubes (CNTs) as Pt electrocatalyst support. It was found that polyanions (poly(styrenesulfonic acid) (PSS), and poly(acrylic acid sodium) (PAA)) have a beneficial effect on methanol electrooxidation on Pt nanoparticles supported on carbon nanotubes via modifying their electronic structure through charge transfer from polyanions to Pt sites and supply of oxygen-containing species. The increased electron density around Pt sites by the charge transfer from polyanions would cause partial filling of Pt 5d-bands, resulting in the downshift of d-band center and weaker chemisorption with oxygen-containing species (e.g. COad). The weakened chemisorption of CO on Pt nanoparticles would promote the methanol electrooxidation. On the contrary, polycations would have an opposite effect on the electronic structure and chemisorption properties of Pt nanoparticles. 相似文献
998.
Tianzhi Yu Jing Meng Peng Zhang Yuling Zhao Hui Zhang Duowang Fan Lili Chen Yongqing Qiu 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2010,75(3):1036-1042
Two new coumarin derivatives, 7-(N,N′-diethylamino)-3-(4-hydroxyphenyl)-coumarin and 7-(N,N′-diethylamino)-3-(4-bromophenyl)-coumarin, were synthesized successfully. Their structures were verified by single crystal X-ray crystallography. The UV–vis absorption and fluorescence of the compounds were discussed. The compounds exhibit strong blue emission under ultraviolet light excitation. The molecular structures, the lowest energy transitions and the UV–vis spectra of 7-(N,N′-diethylamino)-3-(4-hydroxyphenyl)-coumarin and 7-(N,N′-diethylamino)-3-(4-bromophenyl)-coumarin have been studied with density functional theory (DFT) and time-dependent density functional theory (TD-DFT) at B3LYP/6-31G(d) level. 相似文献
999.
Quanpeng Chen Shiyun Ai Hai Fan Jun Cai Qiang Ma Xiangbin Zhu Huanshun Yin 《Journal of Solid State Electrochemistry》2010,14(9):1681-1688
A novel and sensitive biosensor was developed for the determination of nitrite. Firstly, multi-walled carbon nanotubes–poly(amidoamine)–chitosan
(MWNT–PAMAM–Chit) nanocomposite along with the incorporation of DNA was used to modify the glassy carbon electrode. Then the
immobilization of Cyt c was accomplished using electrochemical deposition method by consecutive cyclic voltammetry (CV) scanning in a neutral Cyt
c solution. CV behaviors of the modified electrodes showed that the MWNT–PAMAM–Chit nanocomposite is a good platform for the
immobilization of DNA and Cyt c in order, at the same time, an excellent promoter for the electron transfer between Cyt c and the electrode. At high potential, the immobilized Cyt c could be further oxidized into highly reactive Cyt c π-cation by two-step electrochemical oxidation, which could oxidize NO2
− into NO3
− in the solution. Therefore, a nitrite biosensor based on the biocatalytic oxidation of the immobilized Cyt c was fabricated, which showed a fast response to nitrite (less than 5 s). The linear range of 0.2–80 μM and a detection limit
of 0.03 μM was obtained. Finally, the application in food analysis using sausage as testing samples was also investigated. 相似文献
1000.