全文获取类型
收费全文 | 1074篇 |
免费 | 27篇 |
国内免费 | 2篇 |
专业分类
化学 | 637篇 |
晶体学 | 7篇 |
力学 | 83篇 |
数学 | 107篇 |
物理学 | 269篇 |
出版年
2022年 | 10篇 |
2021年 | 10篇 |
2020年 | 18篇 |
2019年 | 22篇 |
2018年 | 9篇 |
2017年 | 16篇 |
2016年 | 23篇 |
2015年 | 15篇 |
2014年 | 43篇 |
2013年 | 75篇 |
2012年 | 78篇 |
2011年 | 63篇 |
2010年 | 48篇 |
2009年 | 32篇 |
2008年 | 45篇 |
2007年 | 39篇 |
2006年 | 38篇 |
2005年 | 34篇 |
2004年 | 25篇 |
2003年 | 34篇 |
2002年 | 22篇 |
2001年 | 8篇 |
1999年 | 7篇 |
1998年 | 10篇 |
1997年 | 12篇 |
1996年 | 12篇 |
1995年 | 14篇 |
1994年 | 11篇 |
1992年 | 7篇 |
1991年 | 9篇 |
1990年 | 10篇 |
1989年 | 14篇 |
1988年 | 7篇 |
1987年 | 7篇 |
1986年 | 10篇 |
1985年 | 20篇 |
1984年 | 11篇 |
1983年 | 14篇 |
1982年 | 14篇 |
1981年 | 11篇 |
1980年 | 12篇 |
1979年 | 16篇 |
1978年 | 16篇 |
1977年 | 12篇 |
1976年 | 14篇 |
1974年 | 9篇 |
1973年 | 13篇 |
1945年 | 6篇 |
1941年 | 11篇 |
1936年 | 9篇 |
排序方式: 共有1103条查询结果,搜索用时 15 毫秒
1.
2.
Nagu A. Vasikerappa K. Gidyonu P. Prathap Ch. Venkata Rao M. Rama Rao K. S. David Raju B. 《Research on Chemical Intermediates》2020,46(5):2669-2681
Research on Chemical Intermediates - MgO-supported Ni catalysts were selectively catalysed by the hydrogenation of benzonitrile to benzylamine in continuous flow at atmospheric pressure without any... 相似文献
3.
4.
5.
Rama Moorhy Appa S. Siva Prasad Jangam Lakshmidevi Bandameeda Ramesh Naidu Manchala Narasimhulu Katta Venkateswarlu 《应用有机金属化学》2019,33(10)
An agro waste‐derived, ‘water extract of pomegranate ash’ (WEPA), has been utilized for the first time as a renewable medium for Pd(OAc)2‐catalysed Suzuki–Miyaura cross‐coupling at room temperature. This method offers a simple and sustainable synthesis of biaryls from aryl halides and arylboronic acids under ligand‐ and external base‐free aerobic and ambient conditions. This method has been found effective for both activated and unactivated aryl halides in the production of biaryls with moderate to nearly quantitative yields. The protocol shows high chemoselectivity over identical/similar reactive sites in aryl halides (i.e. selectivity over identical halogens or different halogens of aryl halides). This method exhibits high regioselectivity, i.e. the selective reactivity of a halogen over other identical halogens at different positions on the aromatic nucleus. Therefore, we disclose here a clean, benign, substantial chemo‐ and regioselective and highly economic alternative method for the palladium‐assisted synthesis of biaryls using an agro waste‐derived medium. 相似文献
6.
Dwivedi Jyotsana Gupta Abhishek Verma Shikhar Paliwal Sarvesh Rawat Ajay Kumar Singh 《平面色谱法杂志一现代薄层色谱法》2019,32(2):103-108
JPC – Journal of Planar Chromatography – Modern TLC - A high-performance thin-layer chromatography (HPTLC) method for the simultaneous quantitative determination and validation of... 相似文献
7.
Harsha K. Tripathy S. V. Nair Manju Rama Murthy Bestha Vinay Kiran Sreekanth Dittakavi Ramesh Mullangi 《Biomedical chromatography : BMC》2022,36(8):e5387
In this study, we report the development and validation of an LC–tandem mass spectrometry method for the simultaneous quantitation of bendamustine and copanlisib in mouse plasma as per the US FDA regulatory guidelines. The sample processing involves extraction of bendamustine and copanlisib along with internal standard (IS; warfarin) from 50 μL mouse plasma using a liquid–liquid extraction method. The chromatographic separation of bendamustine, copanlisib and the IS was achieved on an Atlantis dC18 column using an isocratic mobile phase (5 mM ammonium acetate:methanol, 20:80 v/v). Bendamustine, copanlisib and the IS eluted at 0.88, 1.39 and 0.74 min, respectively, with a total run time of 2.5 min. The calibration curve ranged from 3.99–2996 and 4.33–3248 ng/mL for bendamustine and copanlisib, respectively. Inter- and intra-day precision and accuracy, stability in processed samples and upon storage, dilution integrity and incurred sample reanalysis were investigated for both the analytes. The intra- and inter-day precisions were in the ranges of 2.01%–5.05% and 2.74%–6.13% and 1.98%–7.64 and 8.62%–9.04% for bendamustine and copanlisib, respectively. Stability studies showed that both analytes were stable on bench top for 6 h, in auto-sampler for 24 and at −80°C for 30 days. The validated method was successfully applied to a pharmacokinetic study in mice. 相似文献
8.
Frontispiece: New Dual Fluorescent Probe for Simultaneous Biothiol and Phosphate Bioimaging 下载免费PDF全文
9.
An analysis is presented for the calculation of heat transfer due to free convective flow along a vertical plate embedded in a porous medium with an arbitrarily varying surface heat flux. By applying the appropriate coordinate transformations and the Merk series, the governing energy equation is expressed as a set of ordinary differential equations. Numerical solutions are presented for these equations which represent universal functions and several computational examples are provided. 相似文献
10.
K.?Sanjeev RaoEmail author Rajeswari?Seshadri Rama?Govindarajan 《Theoretical and Computational Fluid Dynamics》2004,17(4):233-248
A new minimal composite theory that extends the approach of Govindarajan and Narasimha [1] is proposed here for 2D non-parallel compressible boundary-layer stability subject to 3D disturbances. The mean profiles are obtained from Hortons analysis, which provides a good approximation for a large range of Prandtl numbers at non-zero pressure gradients. In the lowest order, all effects of order lower than O(R-2/3) anywhere in the boundary-layer are included, R being the local boundary-layer Reynolds number; the resulting non-parallel formulation yields a set of four ordinary differential equations, as compared to the five coupled equations of classical parallel flow theory of Mack [2]. The largest effect on stability of flow non-parallelism is found to be due to the wall-normal advection of velocity and temperature disturbance quantities by the mean flow. The present theory shows that the bulk viscosity, invariably included in compressible stability theories, is irrelevant at the lowest order. In comparison with the full [O(R-1)] non-parallel theory, the present theory is marginally better than the parallel flow theory. PACS 03.50.De, 04.20-q, 42.65-k 相似文献