全文获取类型
收费全文 | 346篇 |
免费 | 8篇 |
国内免费 | 5篇 |
专业分类
化学 | 215篇 |
晶体学 | 4篇 |
力学 | 11篇 |
数学 | 48篇 |
物理学 | 81篇 |
出版年
2023年 | 3篇 |
2022年 | 11篇 |
2021年 | 16篇 |
2020年 | 16篇 |
2019年 | 7篇 |
2018年 | 8篇 |
2017年 | 9篇 |
2016年 | 12篇 |
2015年 | 3篇 |
2014年 | 9篇 |
2013年 | 9篇 |
2012年 | 26篇 |
2011年 | 18篇 |
2010年 | 17篇 |
2009年 | 7篇 |
2008年 | 12篇 |
2007年 | 9篇 |
2006年 | 19篇 |
2005年 | 16篇 |
2004年 | 13篇 |
2003年 | 17篇 |
2002年 | 12篇 |
2001年 | 6篇 |
2000年 | 3篇 |
1999年 | 5篇 |
1996年 | 4篇 |
1995年 | 4篇 |
1994年 | 4篇 |
1993年 | 2篇 |
1992年 | 4篇 |
1991年 | 1篇 |
1990年 | 2篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1986年 | 5篇 |
1985年 | 3篇 |
1984年 | 1篇 |
1983年 | 5篇 |
1982年 | 6篇 |
1981年 | 7篇 |
1980年 | 5篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1977年 | 2篇 |
1976年 | 4篇 |
1975年 | 5篇 |
1974年 | 2篇 |
1973年 | 1篇 |
1972年 | 2篇 |
1970年 | 2篇 |
排序方式: 共有359条查询结果,搜索用时 15 毫秒
1.
Nguyen Hoa Hong Joe Sakai Ngo Thu Huong Virginie Brizé 《Journal of magnetism and magnetic materials》2006
Laser-ablated Co-doped In2O3 thin films were fabricated under various growth conditions on R-cut Al2O3 and MgO substrates. All Co:In2O3 films are well-crystallized, single phase, and room temperature ferromagnetic. Co atoms were well substituted for In atoms, and their distribution is greatly uniform over the whole thickness of the films. Films grown at 550 °C showed the largest magnetic moment of about 0.5 μB/Co, while films grown at higher temperatures have magnetic moments of one order smaller. The observed ferromagnetism above room temperature in Co:In2O3 thin films has confirmed that doping few percent of magnetic elements such as Co into In2O3 could result in a promising magnetic material. 相似文献
2.
This study reports on the development of an immunochromatographic flow-injection (FI) method for the quantitation of human serum IgG antibodies to Helicobacter pylori. Patients’ sera were injected into the carrier stream of a FI manifold incorporating an H. pylori immuno-adsorbent reactor. The immuno-adsorbent was prepared by covalently linking H. pylori antigens to periodate oxidized Sepharose CL-4B. Any H. pylori antibody present in the serum is bound to the immuno-sorbent. The bound antibody was quantified by injecting into the carrier stream anti-human IgG peroxidase conjugate followed by TMB/H2O2 as the enzyme substrate. The FI system was optimized with respect to antigen loading (1.0 mg/ml gel), bioreactor length (3.0 cm), enzyme conjugate (0.2 mg/ml) and sample loop size (250 μl). One hundred clinical samples were analyzed for their H. pylori antibody concentrations and the results evaluated with respect to their receiver-operator characteristics (ROC). When a cut-off absorbance of between 0.7 and 0.75 was used for positive and negative samples a specificity (>95%), a sensitivity (>90%)and an overall accuracy (>94%) were obtained. 相似文献
3.
Transport of yttrium(III) from nitrate medium through liquid membrane containing tri-n-octyl-phosphine oxide (TOPO) in n-dodecane, supported on a nucleoporous filter, into a strip solution with ethylenediaminetetraacetic acid (EDTA) has been studied. The kinetic dependences of transport were obtained and compared with a model, resulting in calculation of permeability coeffients and initial fluxes of yttrium. The influence of salting-out agent, initial metal and nitric acid concentrations in the feed, and of concentration of carrier in membrane are discussed. 相似文献
4.
Alexander Filosa Heng Wang Wei‐Jian Li Wenjing Zhang Ellie Ngo Jonathan E. Piccolo Hai‐Bo Yang Xiaopeng Li 《中国化学》2019,37(11):1167-1173
Porphyrins have been widely used in the self‐assembly of metallo‐supramolecules. In this study, we introduced 2,2':6,2"‐terpyridine (tpy) into a porphyrin core to synthesize a tetratopic building block with multiple conformers. During the self‐assembly with Zn(II), such a mixture of conformers was able to form a discrete nanoprism with all building blocks in one conformation. Detailed characterizations, including NMR, ESI‐MS and traveling‐wave ion mobility‐mass spectrometry (TWIM‐MS), all supported the formation of the desired assemblies. AFM and TEM further confirmed the dimensions of assembled nanoprisms. Moreover, the photophysical properties of the ligands and complexes were noticeably different depending upon size and metal ion center. 相似文献
5.
A family of homochiral metal carboxylate coordination polymers have been synthesized by treating 2,2'-dihydroxy-1,1'-binaphthalene-6,6'-dicarboxylic acid (H(2)BDA) with metal salts at elevated temperatures. BDA ligands link adjacent metal centers to form 1D coordination polymeric chains using the carboxylate functionality, while the hydroxyl groups of BDA ligands form H-bonds with carboxylate oxygen atoms to link 1D coordination polymeric chains into open frameworks of higher dimensionality. We also present evidence for the important role played by H-bonds in the stabilization of open framework structures which allows for the hierarchical assembly of chiral porous solids. 相似文献
6.
A rapid and sensitive flow-injection method is described for the fluorimetric determination of the proteolytic activity of a number of enzymes. The substrate, fluorescein-labelled bovine serum albumin coupled to a 2-fluoro 1-methylpyridinium salt-activated Fractogel support, is packed in a small reactor (35 × 2 mm i.d.) and inserted into a flow manifold. Under the reaction conditions the amount of fluorescein released from enzymatic cleavage of the substrate is found to be directly proportional to the activity of the proteolytic enzyme. Sample throughput is 30–35 h?1. The calibration range for trypsin is linear up to at least 0.35 μg ml?1. Linear responses were also obtained for otherproteolytic enzymes such as papain, chymotrypsin, ficin and bromelain. 相似文献
7.
James D. Korp Ivan Bernal Nikolaus H. Fischer Charles Leonard Ihl-Young Lee Ngo LeVan 《Journal of heterocyclic chemistry》1982,19(1):181-187
The isolation and structure determination of two new guaianolides, pumilin and its 2,3-epoxide, from Berlandiera pumila and B. texana are reported. The structure of pumilin was determined from nmr and mass spectral data, and from an X-ray single crystal study; the structure of the epoxide was found by comparison of nmr spectra. Pumilin is shown to be a Δ1(10)-cis-guaianolide with a cyclopentenone ring attached to C1 and C5, and an α-methylene-γ-lactone ring trans-fused to C6 and C7. The absolute configuration was inferred from spectral considerations and knowledge of previous structural determinations. The cd spectrum of pumilin exhibits a negative Cotton effect, and the lactone chromophore has left-handed chirality. The cyclo-heptene ring is in the chair configuration, with the lactone a half-chair and the cyclopentenone essentially planar. Crystals are orthorhombic, a = 7.065, b = 13.652, c = 19.586 Å, space group P212121, Z = 4, and the final R value is 3.9%. The crystal structure is strengthened by an O···O hydrogen bond linking the molecules into infinite chains. 相似文献
8.
9.
Dr. Thien H. Ngo Dr. Hülya Berndt Dr. Michael Wilsdorf Prof. Dr. Hans‐Ulrich Reissig 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(45):15155-15165
The dipeptide isostere 5‐aminothiophene carboxylic acid has been combined with L ‐phenylalanine moieties to provide linear and cyclic hybrid oligopeptides. A suitable protecting group strategy and appropriate coupling methods have been developed to guarantee a high degree of enantiopurity of the resulting amides. Cyclic tetraamides have been efficiently obtained by macrocyclization of the linear derivatives. In the case of racemized cyclization precursors, two diastereomeric macrocycles (S,S/R,R and meso) have been isolated. Their crystal structures show clear effects of the stereogenic centers on the ring conformations and molecular packing. 相似文献
10.