全文获取类型
收费全文 | 13162篇 |
免费 | 367篇 |
国内免费 | 4篇 |
专业分类
化学 | 6737篇 |
晶体学 | 91篇 |
力学 | 306篇 |
数学 | 2998篇 |
物理学 | 3401篇 |
出版年
2021年 | 104篇 |
2020年 | 156篇 |
2019年 | 149篇 |
2018年 | 264篇 |
2017年 | 257篇 |
2016年 | 492篇 |
2015年 | 404篇 |
2014年 | 472篇 |
2013年 | 987篇 |
2012年 | 626篇 |
2011年 | 820篇 |
2010年 | 480篇 |
2009年 | 413篇 |
2008年 | 573篇 |
2007年 | 541篇 |
2006年 | 465篇 |
2005年 | 289篇 |
2004年 | 310篇 |
2003年 | 250篇 |
2002年 | 248篇 |
2001年 | 191篇 |
2000年 | 197篇 |
1999年 | 161篇 |
1998年 | 149篇 |
1997年 | 138篇 |
1996年 | 129篇 |
1995年 | 118篇 |
1994年 | 107篇 |
1993年 | 115篇 |
1992年 | 130篇 |
1991年 | 109篇 |
1990年 | 126篇 |
1989年 | 110篇 |
1988年 | 112篇 |
1987年 | 107篇 |
1986年 | 103篇 |
1985年 | 152篇 |
1984年 | 161篇 |
1983年 | 128篇 |
1982年 | 138篇 |
1981年 | 132篇 |
1980年 | 130篇 |
1979年 | 141篇 |
1978年 | 152篇 |
1977年 | 115篇 |
1976年 | 142篇 |
1975年 | 129篇 |
1974年 | 132篇 |
1973年 | 105篇 |
1972年 | 90篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
Molecular characterization and first report of Cryptosporidium genotypes in human population in the Slovak Republic 下载免费PDF全文
Antónia Petrincová Alexandra Valenčáková Lenka Luptáková František Ondriska Jana Kalinová Monika Halánová Oľga Danišová Pavol Jarčuška 《Electrophoresis》2015,36(23):2925-2930
In our study, we examined 91 fecal samples from five different groups of people containing HIV patients, hemodialysis patients, kidney transplant recipients, immunocompetent humans without clinical signs, and humans with suspected cryptosporidiosis. The purpose of our study was to determine species and genotype composition of representatives of Cryptosporidium spp. using PCR analysis of small subunit ribosomal RNA gene and 60‐kDa glycoprotein gene and examine their phylogenetic relationship. In HIV‐positive/AIDS‐infected group of patients and in hemodialysis patients, no presence of Cryptosporidium species was detected. In two kidney transplant recipients, we detected species/genotypes Cryptosporidium parvum IIaA13G1T1R1 (KT355488) and Cryptosporidium hominis IaA11G2R8 (KT355489) and in two immunocompetent patients with clinical symptoms, we identified Cryptosporidium muris and C. hominis IbA10G2T1 (KT355490). In the group of healthy immunocompetent individuals without clinical signs, we identified species/genotype C. hominis IbA11G2 (KT355491) in one sample. 相似文献
92.
Enantiomeric separation of 1,3‐dimethylamylamine by capillary electrophoresis with indirect UV detection using a dual‐selector system 下载免费PDF全文
The CE method employing an indirect UV detection for the enantioseparation of 1,3‐dimethylamylamine (DMAA), widely used in various preworkout and dietary supplements labeled as a constituent of geranium extract has been developed. The dual‐selector system consisting of negatively charged sulfated α‐CD (1.1% w/v) and sulfated β‐CD (0.2% w/v) in 5 mM phosphate/Tris buffer (pH 3.0) containing the addition of 10 mM benzyltriethylammonium chloride (BTEAC) as the chromophoric additive was used for the enantiomeric separation of DMAA stereoisomers with the LODs in the range of 7.82–9.24 μg/mL. The method was partly validated and applied for the determination of the stereoisomeric composition of DMAA in commercial dietary supplements to verify the potential natural origin of DMAA. 相似文献
93.
The modular software MOLSIM for all‐atom molecular and coarse‐grained simulations is presented with focus on the underlying concepts used. The software possesses four unique features: (1) it is an integrated software for molecular dynamic, Monte Carlo, and Brownian dynamics simulations; (2) simulated objects are constructed in a hierarchical fashion representing atoms, rigid molecules and colloids, flexible chains, hierarchical polymers, and cross‐linked networks; (3) long‐range interactions involving charges, dipoles and/or anisotropic dipole polarizabilities are handled either with the standard Ewald sum, the smooth particle mesh Ewald sum, or the reaction‐field technique; (4) statistical uncertainties are provided for all calculated observables. In addition, MOLSIM supports various statistical ensembles, and several types of simulation cells and boundary conditions are available. Intermolecular interactions comprise tabulated pairwise potentials for speed and uniformity and many‐body interactions involve anisotropic polarizabilities. Intramolecular interactions include bond, angle, and crosslink potentials. A very large set of analyses of static and dynamic properties is provided. The capability of MOLSIM can be extended by user‐providing routines controlling, for example, start conditions, intermolecular potentials, and analyses. An extensive set of case studies in the field of soft matter is presented covering colloids, polymers, and crosslinked networks. © 2015 The Authors. Journal of Computational Chemistry Published by Wiley Periodicals, Inc. 相似文献
94.
95.
96.
π‐Expanded α,β‐Unsaturated Ketones: Synthesis,Optical Properties,and Two‐Photon‐Induced Polymerization 下载免费PDF全文
Rashid Nazir Dr. Florent Bourquard Evaldas Balčiūnas Dr. Sabina Smoleń Dr. David Gray Prof. Dr. Nikolai V. Tkachenko Dr. Maria Farsari Prof. Dr. Daniel T. Gryko 《Chemphyschem》2015,16(3):682-690
A library of π‐expanded α,β‐unsaturated ketones was designed and synthesized. They were prepared by a combination of Wittig reaction, Sonogashira reaction, and aldol condensation. It was further demonstrated that the double aldol condensation can be performed effectively for highly polarized styrene‐ and diphenylacetylene‐derived aldehydes. The strategic placement of two dialkylamino groups at the periphery of D ‐π‐A‐π‐D molecules resulted in dyes with excellent solubility. These ketones absorb light in the region 400–550 nm. Many of them display strong solvatochromism so that the emission ranges from 530–580 nm in toluene to the near‐IR region in benzonitrile. Ketones based on cyclobutanone as central moieties display very high fluorescence quantum yields in nonpolar solvents, which decrease drastically in polar media. Photophysical studies of these new functional dyes revealed that they possess an enhanced two‐photon absorption cross section when compared with simpler ketone derivatives. Due to strong polarization of the resulting dyes, values of two‐photon absorption cross sections on the level of 200–300 GM at 800 nm were achieved, and thanks to that as well as the presence of the keto group, these new two‐photon initiators display excellent performance so that the operating region is 5–75 mW in some cases. 相似文献
97.
98.
Enantioselective comprehensive two‐dimensional gas chromatography. A route to elucidate the authenticity and origin of Rosa damascena Miller essential oils 下载免费PDF全文
Ján Krupčík Roman Gorovenko Ivan Špánik Pat Sandra Daniel W Armstrong 《Journal of separation science》2015,38(19):3397-3403
The analysis of Bulgarian and Turkish Rosa damascena Miller essential oils was performed by flow‐modulated comprehensive two‐dimensional gas chromatography using simultaneous detection of the second column effluent by flame ionization and quadrupole mass spectrometric detection. Enantioselective separations were obtained by running the samples on 2,3‐di‐O‐ethyl‐6‐O‐tert‐butyldimethylsilyl‐β‐cyclodextrin column as the first column and on polyethylene glycol as the second column. The determination of enantiomeric or diastereomeric excess of some terpenoic solutes is a possible route for quality or authenticity control as well as for the elucidation of the country of origin. 相似文献
99.
100.