全文获取类型
收费全文 | 379973篇 |
免费 | 8318篇 |
国内免费 | 6289篇 |
专业分类
化学 | 193532篇 |
晶体学 | 5026篇 |
力学 | 20491篇 |
综合类 | 380篇 |
数学 | 66101篇 |
物理学 | 109050篇 |
出版年
2021年 | 3474篇 |
2020年 | 3909篇 |
2019年 | 4188篇 |
2018年 | 14933篇 |
2017年 | 14720篇 |
2016年 | 12477篇 |
2015年 | 5453篇 |
2014年 | 6982篇 |
2013年 | 13609篇 |
2012年 | 15767篇 |
2011年 | 24072篇 |
2010年 | 15727篇 |
2009年 | 15914篇 |
2008年 | 18904篇 |
2007年 | 20776篇 |
2006年 | 11881篇 |
2005年 | 11833篇 |
2004年 | 10903篇 |
2003年 | 10274篇 |
2002年 | 9386篇 |
2001年 | 9129篇 |
2000年 | 7074篇 |
1999年 | 5237篇 |
1998年 | 4595篇 |
1997年 | 4309篇 |
1996年 | 4336篇 |
1995年 | 3686篇 |
1994年 | 3827篇 |
1993年 | 3636篇 |
1992年 | 3795篇 |
1991年 | 3909篇 |
1990年 | 3696篇 |
1989年 | 3529篇 |
1988年 | 3370篇 |
1987年 | 3282篇 |
1986年 | 3288篇 |
1985年 | 4114篇 |
1984年 | 4125篇 |
1983年 | 3484篇 |
1982年 | 3716篇 |
1981年 | 3436篇 |
1980年 | 3183篇 |
1979年 | 3467篇 |
1978年 | 3681篇 |
1977年 | 3685篇 |
1976年 | 3809篇 |
1975年 | 3477篇 |
1974年 | 3588篇 |
1973年 | 3645篇 |
1972年 | 2934篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
91.
92.
5‐Methylene‐2‐oxazolidinone (1) and 5‐methylene‐1,3‐thiazolidine‐2‐thione (4) react with various isocyanates to give the corresponding urethanes 3 and 5 in high yields in the presence of palladium(0) or palladium(II) catalyst under mild reaction conditions. A mechanism is proposed. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
93.
Maria G. Semenova Larisa E. Belyakova Anna S. Antipova Yu. N. Polikarpov Lida Klouda Anna Markovic Michael M. Il'in 《Colloids and surfaces. B, Biointerfaces》2003,31(1-4):47-54
We report on the effect of commercially important polysaccharides (maltodextrins with variable dextrose equivalent (Paselli SA-2, MD-6 and MD-10) on the surface activity at the air–water interface of small-molecule surfactants (sms), possessing different hydrophobic–lipophilic balance ((SSL (Na+), the main component is a sodium salt of stearol–lactoyl lactic acid, and PGE (080), polyglycerol ester of C18 fatty acid), and widely used in food products. A marked change of the surface activity of sms was found in the presence of maltodextrins by tensiometry. The combined data of laser multiangle light scattering and mixing calorimetry have suggested that this result is governed by specific complex formation between maltodextrins and sms in aqueous medium. Measurements have been made of the molar mass, the second virial coefficient and the enthalpy of intermolecular interactions in aqueous solutions. The implication of a degree of polymerization of maltodextrins in this phenomenon was shown. The interrelation between the molecular parameters of the formed complexes and their surface activity at the air–water interface has been revealed and discussed. 相似文献
94.
95.
V. L. Tsymbalenko 《JETP Letters》2003,78(8):493-496
The kinetics of formation of an anomalous phase from a solution with a small 3He impurity was studied in the temperature range 0.2–0.7 K up to a supersaturation of ~30 mbar. The phase diagram was determined for normal and anomalous growths. It is found that, in the presence of impurities, the formation of a fast-growing state is retarded. This experimental fact indicates that the dissipative processes in fluids have an appreciable effect on the phase formation kinetics. The retardation is, possibly, caused by the direct interaction of an impurity with the crystal surface. 相似文献
96.
Makarov V. L. Khlobystov V. V. Kashpur E. F. Mikhal'chuk B. R. 《Ukrainian Mathematical Journal》2003,55(6):942-955
We construct an integral Newton-type interpolation polynomial with a continual set of nodes. This interpolant is unique and preserves an operator polynomial of the corresponding degree. 相似文献
97.
Z. J. Yu L. J. Liu R. X. Zhuo 《Journal of polymer science. Part A, Polymer chemistry》2003,41(1):13-21
The ring‐opening polymerization of ε‐caprolactone (ε‐CL), initiated by carboxylic acids such as benzoic acid and chlorinated acetic acids under microwave irradiation, was investigated; with this method, no metal catalyst was necessary. The product was characterized as poly(ε‐caprolactone) (PCL) by 1H NMR spectroscopy, Fourier transform infrared spectroscopy, ultraviolet spectroscopy, and gel permeation chromatography. The polymerization was significantly improved under microwave irradiation. The weight‐average molecular weight (Mw) of PCL reached 44,800 g/mol, with a polydispersity index [weight‐average molecular weight/number‐average molecular weight (Mw/Mn)] of 1.6, when a mixture of ε‐CL and benzoic acid (25/1 molar ratio) was irradiated at 680 W for 240 min, whereas PCL with Mw = 12,100 and Mw/Mn = 4.2 was obtained from the same mixture by a conventional heating method at 210 °C for 240 min. A degradation of the resultant PCL was observed during microwave polymerization with chlorinated acetic acids as initiators, and this induced a decrease in Mw of PCL. However, the degradation was hindered by benzoic acid at low concentrations. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 13–21, 2003 相似文献
98.
P L Melgarejo M Ternero I Gracia 《International journal of environmental analytical chemistry》1986,24(4):283-295
A study of the atmospheric pollution by suspended particulate lead in the city of Seville, Spain, was carried out during the period between March 1983 and February 1984. The results obtained from seven sampling stations allowed us to study the site to site variations; there are two locations with average annual concentrations higher than 2 micrograms X m-3. In one station, the meteorological and traffic effects and relationship with other traffic-related pollutants, were investigated. The regression analyses performed on the average monthly data have shown an inverse correlation with wind speed and temperature and a direct correlation with carbon monoxide and smoke concentrations, but no significant correlation was found with the lead deposition levels. 相似文献
99.
100.
I. L. Bataronov A. M. Roshchupkin 《Journal of Applied Mechanics and Technical Physics》1991,32(2):259-265
Translated from Zhurnal Prikladnoi Mekhaniki i Tekhnicheskoi Fiziki, No. 2, pp. 127–134, March–April, 1991. 相似文献