全文获取类型
收费全文 | 1588篇 |
免费 | 75篇 |
国内免费 | 15篇 |
专业分类
化学 | 950篇 |
晶体学 | 17篇 |
力学 | 35篇 |
数学 | 379篇 |
物理学 | 297篇 |
出版年
2024年 | 3篇 |
2023年 | 13篇 |
2022年 | 32篇 |
2021年 | 44篇 |
2020年 | 33篇 |
2019年 | 46篇 |
2018年 | 48篇 |
2017年 | 53篇 |
2016年 | 67篇 |
2015年 | 45篇 |
2014年 | 102篇 |
2013年 | 153篇 |
2012年 | 119篇 |
2011年 | 99篇 |
2010年 | 85篇 |
2009年 | 65篇 |
2008年 | 97篇 |
2007年 | 80篇 |
2006年 | 81篇 |
2005年 | 53篇 |
2004年 | 62篇 |
2003年 | 49篇 |
2002年 | 41篇 |
2001年 | 19篇 |
2000年 | 19篇 |
1999年 | 19篇 |
1998年 | 7篇 |
1997年 | 6篇 |
1996年 | 9篇 |
1995年 | 9篇 |
1994年 | 8篇 |
1993年 | 9篇 |
1992年 | 10篇 |
1991年 | 7篇 |
1990年 | 5篇 |
1989年 | 11篇 |
1988年 | 8篇 |
1987年 | 7篇 |
1986年 | 3篇 |
1985年 | 7篇 |
1984年 | 7篇 |
1983年 | 5篇 |
1982年 | 15篇 |
1981年 | 1篇 |
1980年 | 7篇 |
1979年 | 4篇 |
1978年 | 3篇 |
1976年 | 1篇 |
1973年 | 1篇 |
1972年 | 1篇 |
排序方式: 共有1678条查询结果,搜索用时 15 毫秒
151.
152.
153.
Madhav S. Mane Ravi S. Balaskar Sandip N. Gavade Pramod N. Pabrekar Murlidhar S. Shingare Dhananjay V. Mane 《中国化学快报》2011,22(9):1039-1042
The regiospecific oxidation of alkyl group of both sterically hindered and unhindered aromatic amine to corresponding carbonyl compound was done in aq. medium by using DDQ. The optimized reaction protocol was found to be most simple, high yielding and novel method for oxidation of alkyl group of aromatic amine in to its carbonyl compound. 相似文献
154.
Said R. Grace Ravi P. Agarwal Martin Bohner Donal O’Regan 《Communications in Nonlinear Science & Numerical Simulation》2009,14(8):3463-3471
We establish some new criteria for the oscillation of second-order nonlinear dynamic equations on a time scale. We study the case of strongly superlinear and the case of strongly sublinear equations subject to various conditions. 相似文献
155.
156.
JPC – Journal of Planar Chromatography – Modern TLC - The normal-phase (NP) and reversed-phase (RP) thin-layer chromatographic separations of aminoglycosides (streptomycin, kanamycin,... 相似文献
157.
K. M. Mathew S. Ravi D. Padmanabhan 《Journal of Radioanalytical and Nuclear Chemistry》2005,265(3):505-506
Summary 4,6-dimethoxy-2-methylsulphonylpyrimidine is a key intermediate for the synthesis of pyrithiobac-sodium, a selective herbicide for cotton plant. 14C labeled pyrithiobac-sodium is required for studying the translocation and metabolism in cotton plants. It was prepared by oxidation of 4,6-dimethoxy-[2-14C]-2-methylmercaptopyrimidine with H5IO6/CrO3 in ethyl acetate at room temperature to give 4,6-dimethoxy-[2-14C]-2-methylsulphonylpyrimidine in high yields. 相似文献
158.
This paper presents a comprehensive review of the work done, during the 1968–2005, in the application of statistical and intelligent techniques to solve the bankruptcy prediction problem faced by banks and firms. The review is categorized by taking the type of technique applied to solve this problem as an important dimension. Accordingly, the papers are grouped in the following families of techniques: (i) statistical techniques, (ii) neural networks, (iii) case-based reasoning, (iv) decision trees, (iv) operational research, (v) evolutionary approaches, (vi) rough set based techniques, (vii) other techniques subsuming fuzzy logic, support vector machine and isotonic separation and (viii) soft computing subsuming seamless hybridization of all the above-mentioned techniques. Of particular significance is that in each paper, the review highlights the source of data sets, financial ratios used, country of origin, time line of study and the comparative performance of techniques in terms of prediction accuracy wherever available. The review also lists some important directions for future research. 相似文献
159.
We obtain via Schauder's fixed point theorem new results for singular second‐order boundary value problems where our non‐linear term f(t,y,z) is allowed to change sign. In particular, our problem may be singular at y=0, t=0 and/or t=1. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
160.
Ravi P. Agarwal Victoria Otero-Espinar Kanishka Perera 《Journal of Mathematical Analysis and Applications》2007,331(2):1263-1274
The aim of this paper is to employ variational techniques and critical point theory to prove some sufficient conditions for the existence of multiple positive solutions to a nonlinear second order dynamic equation with homogeneous Dirichlet boundary conditions. 相似文献