全文获取类型
收费全文 | 292篇 |
免费 | 11篇 |
国内免费 | 1篇 |
专业分类
化学 | 183篇 |
力学 | 16篇 |
数学 | 14篇 |
物理学 | 91篇 |
出版年
2022年 | 7篇 |
2021年 | 6篇 |
2020年 | 5篇 |
2019年 | 6篇 |
2018年 | 4篇 |
2016年 | 8篇 |
2015年 | 8篇 |
2014年 | 7篇 |
2013年 | 20篇 |
2012年 | 20篇 |
2011年 | 22篇 |
2010年 | 16篇 |
2009年 | 7篇 |
2008年 | 17篇 |
2007年 | 15篇 |
2006年 | 12篇 |
2005年 | 12篇 |
2004年 | 8篇 |
2003年 | 12篇 |
2002年 | 14篇 |
2001年 | 4篇 |
2000年 | 3篇 |
1999年 | 2篇 |
1998年 | 2篇 |
1993年 | 3篇 |
1992年 | 1篇 |
1991年 | 4篇 |
1990年 | 2篇 |
1989年 | 1篇 |
1988年 | 5篇 |
1987年 | 2篇 |
1985年 | 4篇 |
1984年 | 7篇 |
1983年 | 2篇 |
1982年 | 4篇 |
1981年 | 5篇 |
1980年 | 3篇 |
1979年 | 1篇 |
1978年 | 4篇 |
1977年 | 1篇 |
1975年 | 3篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1972年 | 1篇 |
1971年 | 1篇 |
1970年 | 2篇 |
1968年 | 1篇 |
1967年 | 1篇 |
1966年 | 1篇 |
1858年 | 1篇 |
排序方式: 共有304条查询结果,搜索用时 15 毫秒
291.
Boatto G Culeddu N Testa C Neri B Brambilla G Barbosa J Cruz C 《Analytica chimica acta》2007,586(1-2):223-227
In animal production, it is consolidated the synthesis and the illegal use of growth promoters of new generation, able to skip routine screening and confirmatory analysis. In this work it is reported the nuclear magnetic resonance (NMR) and the mass spectrometry identification of a probable new adrenergic drug found in a feed premix. The substance was selectively purified on alpha 1 acid glycoprotein affinity columns; then its structure was first achieved by recording the 13C NMR spectrum that gave the total number of carbons of the molecule, successively sorted by DEPT experiments into quaternary, CH, CH2, and CH3 groups. However, the complete assignments of all resonances were derived from the bi-dimensional analysis and the crucial indications from the 1H-13C reverse experiments. Further characterisation was performed by atmospheric pressure chemical ionisation both in positive and negative ion mode, matching the molecular ion and the fragmentation pattern with those of most recently described new adrenergic agonists. After the loss of a ter-butylic group, the structure shows an internal symmetry along with the presence of Chlorine clusters. The proposed formula of the compound, the 8,8'-diamino-9,9'-dichloro-1-terbutyl-1,1',4,4-tetrahydro-5H,5'H-2,2'-bi-1-benzazepine-5,5'-dione, partially resembles that of Zilpaterol for the presence of a heterocyclic ring; Further work is in progress to characterise the structure-activity relationship. 相似文献
292.
Novel propylmethacrylate-monofunctionalized polyhedral oligomeric silsesquioxanes (POSS-PMA) homopolymers were obtained, in good yield, by free bulk radical polymerizations of the low melting macromer heptaisobutylpentacyclooctasiloxan-1-(yl)propylmethacrylate [(PMA)(i-Bu)7T8], 1, by using different initiator/macromer molar ratios. Their characterization was accomplished by TG, DTG and DSC analyses, Gel permeation chromatography (GPC) and MALDI-TOF mass spectrometry. The results indicate that both macromolecular as well as the thermal properties of the new materials are dependent on the initiator/macromer molar ratio used in the polymerization process. By increasing the amount of initiator, polymers with lowest molecular masses, highest molecular weight distributions (MWD) and lowest thermal stability were obtained. High value of MWD was found for all the samples. The different thermal behavior observed for the sample prepared by using the highest amount of initiator is explained by the formation of polymer branched chain, induced by chain transfer to polymer processes. MALDI-TOF mass spectra resulted diagnostic of the homopolymers compositions displaying a series of peaks corresponding to oligomeric structures present in the polymeric samples. The thermal polymerization of 1 performed without employing catalyst was also investigated. Only low yields (4%) of short oligomers (from dimer to pentamer), bearing degraded POSS cages, were isolated. 相似文献
293.
Gulino A Gupta T Mineo PG van der Boom ME 《Chemical communications (Cambridge, England)》2007,(46):4878-4880
Optical detection of parts-per-million (ppm) levels of NO2 (1-10 ppm) and NO(x) (800-2550 ppm) by a structurally well-defined monolayer consisting of osmium polypyridyl complexes on glass substrates has been demonstrated. 相似文献
294.
Thin silver films were deposited by pulsed laser ablation in a controlled Ar atmosphere and their SERS activity was investigated.
The samples were grown at Ar pressures between 10 and 70 Pa and at different laser pulse numbers. Other deposition parameters
such as laser fluence, target to substrate distance and substrate temperature were kept fixed at 2.0 J/cm2, 35 mm and 297 K. Film morphologies were investigated by scanning and transmission electron microscopies (SEM, TEM). Surface
features range from isolated nearly spherical nanoparticles to larger islands with smoothed edges. Cluster growth is favored
by plume confinement induced by background gas. After landing on the substrate clusters start to aggregate giving rise to
larger structures as long as the deposition goes on. Such a path of film growth allows controlling the surface morphology
as a function of laser pulse number and Ar pressure. These two easy-to-manage process parameters control the number density
and the average size of the as-deposited nanoparticles. We investigated the influence of substrate morphologies on their surface
enhanced Raman scattering properties. Raman measurements were performed after soaking the samples in rhodamine 6G aqueous
solutions over the concentration range between 1.0 × 10−4 and 5.0 × 10−8 M. The sensitivity of the film SERS activity on the surface features is put into evidence. 相似文献
295.
Danuta Kaczmarek Damian Wojcieszak Jaroslaw Domaradzki Eugeniusz Prociow Frank Placido Steffen Lapp Rafal Dylewicz 《Central European Journal of Physics》2011,9(2):349-353
In this work, the influence of Tb-doping on structure, and especially hardness of nanocrystalline TiO2 thin films, has been described. Thin films were formed by a high-energy reactive magnetron sputtering process in a pure oxygen
atmosphere. Undoped TiO2-matrix and TiO2:Tb (2 at. % and 2.6 at. %) thin films, had rutile structure with crystallite sizes below 10 nm. The high-energy process produces
nanocrystalline, homogenous films with a dense and close packed structure, that were confirmed by X-ray diffraction patterns
and micrographs from a scanning electron microscope. Investigation of thin film hardness was performed with the aid of a nanoindentation
technique. Results of measurements have shown that the hardness of all manufactured nanocrystalline films is above 10 GPa.
In the case of undoped TiO2 matrix, the highest hardness value was obtained (14.3 GPa), while doping with terbium results in hardness decreasing down
to 12.7 GPa and 10.8 GPa for TiO2:(2 at. % Tb) and TiO2:(2.6 at. % Tb) thin films, respectively. Incorporation of terbium into TiO2-matrix also allows modification of the elastic properties of the films. 相似文献
296.
A Small‐Molecule Drug Conjugate for the Treatment of Carbonic Anhydrase IX Expressing Tumors 下载免费PDF全文
Nikolaus Krall Francesca Pretto Willy Decurtins Dr. Gonçalo J. L. Bernardes Prof. Claudiu T. Supuran Prof. Dario Neri 《Angewandte Chemie (International ed. in English)》2014,53(16):4231-4235
Antibody–drug conjugates are a very promising class of new anticancer agents, but the use of small‐molecule ligands for the targeted delivery of cytotoxic drugs into solid tumors is less well established. Here, we describe the first small‐molecule drug conjugates for the treatment of carbonic anhydrase IX expressing solid tumors. Using ligand–dye conjugates we demonstrate that such molecules can preferentially accumulate inside antigen‐positive lesions, have fast targeting kinetics and good tumor‐penetrating properties, and are easily accessible by total synthesis. A disulfide‐linked drug conjugate with the maytansinoid DM1 as the cytotoxic payload and a derivative of acetazolamide as the targeting ligand exhibited a potent antitumor effect in SKRC52 renal cell carcinoma in vivo. It was furthermore superior to sunitinib and sorafenib, both small‐molecule standard‐of‐care drugs for the treatment of kidney cancer. 相似文献
297.
298.
Markus Leimbacher Dr. Yixin Zhang Dr. Luca Mannocci Michael Stravs Dr. Tim Geppert Dr. Jörg Scheuermann Prof. Gisbert Schneider Prof. Dario Neri 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(25):7729-7737
Libraries of chemical compounds individually coupled to encoding DNA tags (DNA‐encoded chemical libraries) hold promise to facilitate exceptionally efficient ligand discovery. We constructed a high‐quality DNA‐encoded chemical library comprising 30 000 drug‐like compounds; this was screened in 170 different affinity capture experiments. High‐throughput sequencing allowed the evaluation of 120 million DNA codes for a systematic analysis of selection strategies and statistically robust identification of binding molecules. Selections performed against the tumor‐associated antigen carbonic anhydrase IX (CA IX) and the pro‐inflammatory cytokine interleukin‐2 (IL‐2) yielded potent inhibitors with exquisite target specificity. The binding mode of the revealed pharmacophore against IL‐2 was confirmed by molecular docking. Our findings suggest that DNA‐encoded chemical libraries allow the facile identification of drug‐like ligands principally to any protein of choice, including molecules capable of disrupting high‐affinity protein–protein interactions. 相似文献
299.
Casi G Huguenin-Dezot N Zuberbühler K Scheuermann J Neri D 《Journal of the American Chemical Society》2012,134(13):5887-5892
Aldehyde drugs are gaining increasing research interest, considering that aldehyde dehydrogenases overexpression is characteristic of cancer stem cells. Here, we describe the traceless site-specific coupling of a novel potent drug, containing an aldehyde moiety, to recombinant antibodies, which were engineered to display a cysteine residue at their N-terminus, or a 1,2-aminothiol at their C-terminus. The resulting chemically defined antibody-drug conjugates represent the first example in which a thiazolidine linkage is used for the targeted delivery and release of cytotoxic agents. 相似文献
300.
Albunia AR Gaeta C Neri P Grassi A Milano G 《The journal of physical chemistry. B》2006,110(39):19207-19214
The reorientational dynamics of benzene-d(6) molecules hosted into the cavity of a cavitand-based, self-assembled capsule was investigated by Molecular Dynamics (MD) simulations and temperature-dependent solid-state (2)H NMR spectroscopy. MD simulations were preliminarily performed to assess the motional models of the guest molecules inside the capsules. An in-plane fast reorientation of the benzene guest around the C(6) symmetry axis (B1 motion), characterized by correlation times of the order of picoseconds, was predicted with an activation barrier ( approximately 8 kJ/mol) very similar to that found for neat benzene in the liquid state. An out-of-plane reorientation corresponding to a nutation of the C(6) symmetry axis in a cone angle of 39 degrees (B2 motion, 373 K) with an activation barrier ( approximately 39 kJ/mol) definitely larger than that of liquid benzene was also anticipated. In the temperature range 293-373 K correlation times of the order of a nanosecond have been calculated and a transition from fast to slow regime in the (2)H NMR scale has been predicted between 293 and 173 K. (2)H NMR spectroscopic analysis, carried out in the temperature range 173-373 K on the solid capsules containing the perdeuterated guest (two benzene molecules/capsule), confirmed the occurrence of the B1 and B2 motions found in slow exchange in the (2)H NMR time scale. Line shape simulation of the (2)H NMR spectral lines permitted defining a cone angle value of 39 degrees at 373 K and 35 degrees at 173 K for the nutation axis. The T(1) values measured for the (2)H nuclei of the encapsulated aromatic guest gave correlation times and energetic barrier for the in-plane motion B1 in fine agreement with theoretical calculation. The experimental correlation time for B2 as well as the corresponding energetic barrier are in the same range found for B1. A molecular mechanism for the encapsulated guest accounting for the B1 and B2 motions was also provided. 相似文献