全文获取类型
收费全文 | 12206篇 |
免费 | 2040篇 |
国内免费 | 1582篇 |
专业分类
化学 | 8550篇 |
晶体学 | 225篇 |
力学 | 768篇 |
综合类 | 151篇 |
数学 | 1607篇 |
物理学 | 4527篇 |
出版年
2024年 | 34篇 |
2023年 | 211篇 |
2022年 | 384篇 |
2021年 | 385篇 |
2020年 | 513篇 |
2019年 | 500篇 |
2018年 | 448篇 |
2017年 | 422篇 |
2016年 | 582篇 |
2015年 | 716篇 |
2014年 | 753篇 |
2013年 | 1030篇 |
2012年 | 1158篇 |
2011年 | 1138篇 |
2010年 | 877篇 |
2009年 | 837篇 |
2008年 | 924篇 |
2007年 | 787篇 |
2006年 | 661篇 |
2005年 | 581篇 |
2004年 | 428篇 |
2003年 | 344篇 |
2002年 | 333篇 |
2001年 | 237篇 |
2000年 | 241篇 |
1999年 | 168篇 |
1998年 | 98篇 |
1997年 | 96篇 |
1996年 | 85篇 |
1995年 | 104篇 |
1994年 | 65篇 |
1993年 | 66篇 |
1992年 | 48篇 |
1991年 | 47篇 |
1990年 | 41篇 |
1989年 | 34篇 |
1988年 | 48篇 |
1987年 | 15篇 |
1986年 | 24篇 |
1985年 | 35篇 |
1984年 | 28篇 |
1983年 | 26篇 |
1982年 | 25篇 |
1981年 | 18篇 |
1980年 | 25篇 |
1979年 | 23篇 |
1978年 | 27篇 |
1977年 | 18篇 |
1976年 | 14篇 |
1973年 | 11篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
101.
Both absolute molecular weight and molecular sizes (radius of gyration and hydrodynamic radius) of a vinyl-type polynorbornene eluting from size-exclusion chromatography columns were determined by combined with a static and dynamic laser light scattering detector. The hydrodynamic radius of polymer fraction eluting from size-exclusion chromatography columns was obtained from dynamic laser light scattering measurements at only a single angle of 90° by introducing a correction factor. According to the scaling relationship between molecular sizes and molecular weight and the ratio between radius of gyration and hydrodynamic radius, the vinyl-type polynorbornene took a random coil conformation in 1,2,4-trichlorobenzene at 150 °C. 相似文献
102.
Binil Itty Ipe Anuj Shukla Huachang Lu Bo Zou Heinz Rehage Christof M Niemeyer 《Chemphyschem》2006,7(5):1112-1118
Currently, there is great interest in the development of methods suitable for determining the stoichiometry of biomolecules attached to nanoparticles. We describe the use of the dynamic light-scattering technique (DLS) to determine the stoichiometry of the protein cytochrome P450(BSbeta) attached to CdS and CdSe quantum dots (QDs). The enzyme-conjugated QDs have different diffusion characteristics compared to the QD and enzyme precursors, expressed in their size, scattering intensity as well as zeta-potential values. The significant enhancement of the scattering intensity of QDs observed upon conjugation with the P450(BSbeta) due to the refractive-index increment and the systematic variation in zeta potential resulting from charge neutralization of the anionic QDs by the cationic histidine-tagged P450(BSbeta) have been used for stoichiometry determination. 相似文献
103.
Theoretical possibilities of determining energetic and thermodynamic characteristics of chemical entities in gaseous and condensed (solid and liquid) phases are briefly reviewed. The considerations include quantum chemistry methods which enable evaluation of energetic quantities and statistical thermodynamics dependencies necessary for determining other thermodynamic characteristics. The possible applications of these methods are also discussed in brief. 相似文献
104.
模式识别—人工神经网络在化学中的若干新应用 总被引:2,自引:0,他引:2
本文通过我们应用模式识别-人工神经网络方法预报新化合物、熔盐相图以及复杂化学反应体系的研究,展示应用模式识别-人工神经网络方法与物理化学理论相结合,研究化学现象的可能性和应用价值。 相似文献
105.
Hydrogen peroxide is determined by a chemiluminescence method with a reagent containing 100 μM luminol and 3 μM microperoxidase at pH 10 (carbonate buffer). Microperoxidase is superior to hematin as a catalyst. The method uses an automated flow injection system with a throughput of 2 samples per minute. The log—log calibration plot is linear (slope 1.3) from the detection limit, 3 × 10-9 M up to 10-5 M H2O2. The background emission is low. Impurities in the carrier stream and from some plastics may cause elevated background unless precautions are taken. 相似文献
106.
107.
108.
109.
Lingping Wang Aiguo Kong Bo Chen Hanming Ding Yongkui Shan Mingyuan He 《Journal of molecular catalysis. A, Chemical》2005,230(1-2):143-150
Transition metal copper substituted mesoporous silica (Cu-SBA-15) was synthesized using triblock copolymers surfactant as template agent under acidic condition. The result Cu-SBA-15 was characterized with XRD, ICP-AES, FT-IR and N2 adsorption–desorption measurements, which prove that Cu(II) was mainly incorporated into the framework of Cu-SBA-15. Its catalytic activity was studied for phenol hydroxylation using H2O2 (30%). The substituting element (Cu2+) is incorporated into the framework position forming a new type of active site which raises the phenol conversion to 62.4% and the diphenol (the mixture of catechol (CAT) and hydroquinone (HQ)) selectivity to 97%. The Cu-SBA-15 has very high selectivity for catechol (about 71% selectivity), which is completely different from that of the microporous titanium silicalite zeolites (47.1% phenol conversion and about 50% selectivity to CAT under same reaction conditions). The results obtained indicate that the selective oxidation of phenol with H2O2 by a radical substitution mechanism. 相似文献
110.
Summary The substitution of phosphine in the [RhCl(COD)(phosphine)] complex (1), where phosphine is PPh3 or 1/2 BPS-2 [bis(diphenylphosphinoethyl)tetramethyldisiloxane] and COD is cycloocta-1,5-diene, by 1-hexene is a two-step reversible reaction. All individual rate constants and equilibrium constants were determined spectrophotometrically and associative mechanism occurring via the formation of five-coordinated [RhCl(COD)(phosphine)(1-hexene)] (2) was inferred. The rate-determining step changes from the first- to the second-one as the concentration of 1-hexene increases. An excess of phosphine shifts the equilibrium towards complex (2). 相似文献