全文获取类型
收费全文 | 3932篇 |
免费 | 162篇 |
国内免费 | 194篇 |
专业分类
化学 | 3528篇 |
晶体学 | 5篇 |
力学 | 236篇 |
综合类 | 13篇 |
数学 | 165篇 |
物理学 | 341篇 |
出版年
2024年 | 2篇 |
2023年 | 67篇 |
2022年 | 83篇 |
2021年 | 65篇 |
2020年 | 105篇 |
2019年 | 91篇 |
2018年 | 66篇 |
2017年 | 114篇 |
2016年 | 81篇 |
2015年 | 100篇 |
2014年 | 104篇 |
2013年 | 150篇 |
2012年 | 186篇 |
2011年 | 183篇 |
2010年 | 157篇 |
2009年 | 184篇 |
2008年 | 142篇 |
2007年 | 191篇 |
2006年 | 223篇 |
2005年 | 254篇 |
2004年 | 199篇 |
2003年 | 170篇 |
2002年 | 126篇 |
2001年 | 93篇 |
2000年 | 98篇 |
1999年 | 122篇 |
1998年 | 130篇 |
1997年 | 108篇 |
1996年 | 88篇 |
1995年 | 63篇 |
1994年 | 63篇 |
1993年 | 37篇 |
1992年 | 33篇 |
1991年 | 34篇 |
1990年 | 33篇 |
1989年 | 25篇 |
1988年 | 40篇 |
1987年 | 28篇 |
1986年 | 37篇 |
1985年 | 63篇 |
1984年 | 35篇 |
1983年 | 23篇 |
1982年 | 31篇 |
1981年 | 21篇 |
1980年 | 15篇 |
1979年 | 18篇 |
1978年 | 3篇 |
1977年 | 2篇 |
1971年 | 1篇 |
1962年 | 1篇 |
排序方式: 共有4288条查询结果,搜索用时 15 毫秒
1.
2.
Triazines are widely used in agriculture around the world as selective pre‐ and post‐emergence herbicides for the control of broad leaf and grassy weeds. With high toxicity and persistence, triazines can contaminate the environment and crops, so the development of rapid and sensitive methods for the determination of different triazines is necessary. Capillary electrophoresis comprises a group of techniques used to separate chemical mixtures. Analytical separation is based on different electrophoretic mobilities. This review focuses on the analysis of triazine herbicides with different modes of capillary electrophoresis, including capillary zone electrophoresis, micellar electrokinetic capillary electrophoresis, capillary electrochromatography and nonaqueous capillary electrophoresis. Determinations of triazines in various matrices such as surface water, groundwater, vegetables, soil and grains are emphasized. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
3.
毛细管气相色谱法测定中药中有机氯农药残留量 总被引:4,自引:0,他引:4
建立了江西省两种中药中有机氯农药残留量的气相色谱分析方法。样品以丙酮提取,在NaCl存在下,以正已烷进行液—液分配,提取液用H2SO4净化,采用DB—1701毛细管柱,GC—ECD检测有机氯农药残留量。最低检测限为1.0×10-3-5.0×10-3mg/kg,添加回收率为85.7%-115.2%,应用于实际样品中有机氯农药残留量的检测,获得了较为满意结果。 相似文献
4.
A time-dependent model corresponding to an Oldroyd-B viscoelastic fluid is considered, the convective terms being disregarded.
Global existence in time is proved in Banach spaces provided the data are small enough, using the implicit function theorem
and a maximum regularity property for a three fields Stokes problem. A finite element discretization in space is then proposed.
Existence of the numerical solution is proved for small data, so as a priori error estimates, using again an implicit function
theorem.
Supported by the Swiss National Science Foundation. Fellowship PBEL2–114311. 相似文献
5.
6.
CLIFFORDMARTINGALESΦ-EQUIVALENCEBETWEENS(f)ANDf¥LONGRULIN;QIANTAO(InstituteofMathematics,AcademiaSinica,Beijing100080,China.)... 相似文献
7.
Henrik Stetkær 《Journal of Functional Analysis》2007,252(1):1-33
We extend results on square integrable representations of a locally compact group to subrepresentations of a representations induced from a character of a closed subgroup. We do so working in the framework of quotient representations of ∗-algebras. 相似文献
8.
S.K. Mahapatra B.K. Dandapat 《Journal of Quantitative Spectroscopy & Radiative Transfer》2006,102(2):277-292
The current study addresses the mathematical modeling aspects of coupled conductive and radiative heat transfer in the presence of absorbing, emitting and isotropic scattering gray medium within two-dimensional square enclosure. A blended method where the concepts of modified differential approximation employed by combining discrete ordinate method and spherical harmonics method, has been developed for modeling the radiative transport equation. The gray participating medium is bounded by isothermal walls of two-dimensional enclosure which are considered to be opaque, diffuse and gray. The effect of various influencing parameters i.e., radiation-conduction parameter, surface emissivity, single scattering albedo and optical thickness has been illustrated. The adaptability of the present method has also been addressed. 相似文献
9.
Haim Gvirtzman Mordeckai Magaritz Eugenia Klein Arie Nadler 《Transport in Porous Media》1987,2(1):83-93
Cold stage Scanning Electron Microscopy (SEM) with a rapid cooling technique makes it possible to investigate the water phase within unsaturated porous media. It is thought that this technique preserves the main features of the micromorphology of the water menisci as it exists in the liquid phase in soils. Saddle-shaped elements, as well as pendular rings of water, were observed with concave and convex curvatures of the water-air interface. The hydraulic conductivity of an unsaturated soil may be inferred from SEM photographs. Observations of isolated water menisci indicate the existence of an immobile water domain. The surface geometry of the water menisci was analyzed quantitatively and surface tension and capillary pressure were determined. 相似文献
10.
Flaked capillary columns with an OV-101/CE-Na{in3}PO{in4} hydrophobic-hydrophilic sorbent have been suggested. This sorbent provides for the analysis of polar and nonpolar substances, including amines and aminoalcohols, in aqueous and organic solvents. The efficiency of new columns was demonstrated for the analysis of 25 organic substances of various classes.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2169–2173, December, 1994.The work was financially supported by the Russian Foundation for Basic Research, Project No. 93-03-4969. 相似文献