全文获取类型
收费全文 | 201876篇 |
免费 | 40712篇 |
国内免费 | 28327篇 |
专业分类
化学 | 133125篇 |
晶体学 | 2431篇 |
力学 | 13672篇 |
综合类 | 799篇 |
数学 | 24826篇 |
物理学 | 96062篇 |
出版年
2024年 | 791篇 |
2023年 | 3146篇 |
2022年 | 5008篇 |
2021年 | 5192篇 |
2020年 | 5868篇 |
2019年 | 6185篇 |
2018年 | 5571篇 |
2017年 | 5771篇 |
2016年 | 8151篇 |
2015年 | 8170篇 |
2014年 | 9342篇 |
2013年 | 13180篇 |
2012年 | 15138篇 |
2011年 | 16909篇 |
2010年 | 16420篇 |
2009年 | 16305篇 |
2008年 | 11036篇 |
2007年 | 9957篇 |
2006年 | 9134篇 |
2005年 | 8304篇 |
2004年 | 7595篇 |
2003年 | 6075篇 |
2002年 | 5611篇 |
2001年 | 5467篇 |
2000年 | 4523篇 |
1999年 | 5014篇 |
1998年 | 4318篇 |
1997年 | 4017篇 |
1996年 | 4492篇 |
1995年 | 4448篇 |
1994年 | 4403篇 |
1993年 | 4109篇 |
1992年 | 3666篇 |
1991年 | 3180篇 |
1990年 | 2652篇 |
1989年 | 2510篇 |
1988年 | 2368篇 |
1987年 | 1599篇 |
1986年 | 1631篇 |
1985年 | 1272篇 |
1984年 | 1287篇 |
1983年 | 550篇 |
1982年 | 1063篇 |
1981年 | 858篇 |
1980年 | 850篇 |
1979年 | 578篇 |
1978年 | 564篇 |
1977年 | 662篇 |
1976年 | 1077篇 |
1972年 | 549篇 |
排序方式: 共有10000条查询结果,搜索用时 25 毫秒
991.
Martin A. Bos Bertus Dunnewind Ton van Vliet 《Colloids and surfaces. B, Biointerfaces》2003,31(1-4):95-105
Interfacial rheological properties and their suitability for foam production and stability of two vegetable proteins were studied and compared to β-casein. Proteins used ranged from flexible to rigid/globular in the order of β-casein, gliadin and soy glycinin. Experiments were performed at pH 6.7. Network forming properties were characterised by the surface dilational modulus (determined with the ring trough) and the critical falling film length (Lstill) at which a stagnant protein film will break. Gliadin had the highest dilational modulus, followed by glycinin and β-casein, whereas glycinin formed the strongest film against fracture in the overflowing cylinder. The rate of decrease in the surface tension was studied at the air–water (Wilhelmy plate method) and the oil–water interface (bursting membrane) and the dynamic surface tension during compression and expansion in the caterpillar. Gliadin had the lowest equilibrium interfacial tensions and β-casein the lowest dynamic surface tension during expansion. Hardly any foam could be formed at a concentration of 0.1 g/l by shaking. At a concentration of 1.4 g/l most foam was formed by β-casein, followed by gliadin and glycinin. It seems that in the first place the rate of adsorption is important for foam formation. For the vegetable proteins, adsorption was slow. This resulted in lower foamability, especially for glycinin. 相似文献
992.
993.
Single-crystalline layered lithium manganese oxide nanorods were prepared via a low-temperature molten salt synthesis method. The material was investigated by a variety of techniques, including X-ray powder diffraction (XRD), transmission electron microscopy (TEM), and X-ray photoelectron spectrum (XPS). 相似文献
994.
995.
A photoacoustic (PA) spectrometer with H-type first longitudinal resonant cells for ammonia detection is developed. A new PA cell structure is designed to accelerate the drift velocity of the sample gas near the cell surface, so that the short response time at the flow rate of 100 sccm (standard cubic centimeter per minute) is achieved. The response time of 5 min and detection limit of 0.86 ppbv is reached for ammonia concentration measurement with a Teflon polytetrafluoroethylene (PTFE) cell. Further improvement could be expected when using a brass cell with a high quality Teflon fluorinated ethylene propylene (FEP) coating. 相似文献
996.
g1.IntroductionWeconsiderthefollowingfirstorderquasilinearhyperbolicequationswithinternaIdissipa-tlveterm:U, A(U)U. F(U)=o(1.1)whereUeR2isunknownvectorfunction,A(U)is2X2knownsmoothmatrix,F(U)is2X2knownsmoothvectorfunction.Itiswell-knownthatCauchyproblemoftheequations(l.1)hasbeenwidelystudied(Ll-6J),however,theequations(l.1)withperiedicinitialdatahasbeenhardlystudiedandonesfindthatitiscomplicatedforproblemwithperiodicinitialdata.Becausetheperiodicdis-turbanceLlirectlyinfluencesthebounde… 相似文献
997.
998.
A. Wajid C. Gogol C. Hurd M. Hetzel A. Spina R. Lum M. McDonald R. J. Capik 《Journal of Crystal Growth》1997,170(1-4):237-241
We describe a continuous wave resonant acoustic sensor that has been optimized as a very sensitive in-line monitor for measuring the composition of precursor gases used in MOCVD processes. The precursor/carrier gas mixtures flow through a compact stainless steel acoustic chamber that is isolated from the acoustic transducers by a set of metallic diaphragms. The sensor has been successfully operated at supply line pressures from atmosphere down to 50 Torr with gas flow rates of up to 1600 sccm. The accuracy of the speed of sound measurement for hydrogen gas is better than 0.005%, even in a high noise and low pressure environment. Hydrogen, as well as nitrogen or argon carrier gases, are accommodated within the instrument's 1–5 kHz working frequency range. The instrument's sensitivity and stability are demonstrated with the laboratory data. Measurements of the dynamic response characteristics of the metalorganic bubbler lines at low pressure are also be presented. Application of the cell is general, encompassing any of the metalorganic and hydride materials typically used in MOCVD processes. 相似文献
999.
Summary Campaign results of high-repetition ionospheric soundings, performed at the ionospheric station of Rome using a Digisonde
128P, are presented. We introduce an index derived from run rapid ionograms that can be used to detect oscillations of isodensity
surfaces ofF ionospheric region started by morning solar terminator. 相似文献
1000.