全文获取类型
收费全文 | 457244篇 |
免费 | 5709篇 |
国内免费 | 1531篇 |
专业分类
化学 | 243089篇 |
晶体学 | 6916篇 |
力学 | 19685篇 |
综合类 | 10篇 |
数学 | 55840篇 |
物理学 | 138944篇 |
出版年
2020年 | 3180篇 |
2019年 | 3332篇 |
2018年 | 4582篇 |
2017年 | 4664篇 |
2016年 | 7001篇 |
2015年 | 5045篇 |
2014年 | 7195篇 |
2013年 | 20412篇 |
2012年 | 15779篇 |
2011年 | 18991篇 |
2010年 | 12489篇 |
2009年 | 12472篇 |
2008年 | 17364篇 |
2007年 | 17410篇 |
2006年 | 16785篇 |
2005年 | 17433篇 |
2004年 | 15944篇 |
2003年 | 13470篇 |
2002年 | 12164篇 |
2001年 | 13715篇 |
2000年 | 10531篇 |
1999年 | 8288篇 |
1998年 | 6788篇 |
1997年 | 6519篇 |
1996年 | 6473篇 |
1995年 | 5946篇 |
1994年 | 5706篇 |
1993年 | 5497篇 |
1992年 | 6178篇 |
1991年 | 5977篇 |
1990年 | 5707篇 |
1989年 | 5510篇 |
1988年 | 5729篇 |
1987年 | 5447篇 |
1986年 | 5215篇 |
1985年 | 7369篇 |
1984年 | 7514篇 |
1983年 | 6267篇 |
1982年 | 6681篇 |
1981年 | 6550篇 |
1980年 | 6327篇 |
1979年 | 6545篇 |
1978年 | 6640篇 |
1977年 | 6532篇 |
1976年 | 6490篇 |
1975年 | 6343篇 |
1974年 | 6189篇 |
1973年 | 6496篇 |
1972年 | 3969篇 |
1971年 | 3030篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
32.
33.
We summarize the results of our recent work on Bäcklund transformations (BTs), particularly focusing on the relation between BTs and infinitesimal symmetries. We present a BT for an associated Degasperis–Procesi (aDP) equation and its superposition principle and investigate the solutions generated by applying this BT. Following our general methodology, we use the superposition principle of the BT to generate the infinitesimal symmetries of the aDP equation. 相似文献
34.
35.
An approach of dynamic mesh adaptation for simulating 3‐dimensional unsteady moving‐immersed‐boundary flows
下载免费PDF全文
![点击此处可从《国际流体数值方法杂志》网站下载免费的PDF全文](/ch/ext_images/free.gif)
In this paper, we present an approach of dynamic mesh adaptation for simulating complex 3‐dimensional incompressible moving‐boundary flows by immersed boundary methods. Tetrahedral meshes are adapted by a hierarchical refining/coarsening algorithm. Regular refinement is accomplished by dividing 1 tetrahedron into 8 subcells, and irregular refinement is only for eliminating the hanging points. Merging the 8 subcells obtained by regular refinement, the mesh is coarsened. With hierarchical refining/coarsening, mesh adaptivity can be achieved by adjusting the mesh only 1 time for each adaptation period. The level difference between 2 neighboring cells never exceeds 1, and the geometrical quality of mesh does not degrade as the level of adaptive mesh increases. A predictor‐corrector scheme is introduced to eliminate the phase lag between adapted mesh and unsteady solution. The error caused by each solution transferring from the old mesh to the new adapted one is small because most of the nodes on the 2 meshes are coincident. An immersed boundary method named local domain‐free discretization is employed to solve the flow equations. Several numerical experiments have been conducted for 3‐dimensional incompressible moving‐boundary flows. By using the present approach, the number of mesh nodes is reduced greatly while the accuracy of solution can be preserved. 相似文献
36.
37.
Synthesis,spectral investigation and development of tetrahedral copper(II) complexes as artificial metallonucleases and antimalarial agents
下载免费PDF全文
![点击此处可从《应用有机金属化学》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Seven new copper(II) complexes of type [Cu(A)(L)]?H2O (A = sparfloxacin, ciprofloxacin, levofloxacin, gatifloxacin, pefloxacin, ofloxacin, norfloxacin; L = 5‐[(3‐chlorophenyl)diazenyl]‐4‐hydroxy‐1,3‐thiazole‐2(3H)‐thione) were synthesized and characterized using elemental and thermogravimetric analyses, and electronic, electron paramagnetic resonance (EPR), Fourier transform infrared and liquid chromatography–mass spectroscopies. Tetrahedral geometry around copper is assigned in all complexes using EPR and electronic spectral analyses. All complexes were investigated for their interaction with herring sperm DNA utilizing absorption titration (Kb = 1.27–3.13 × 105 M?1) and hydrodynamic volume measurement studies. The studies suggest the classical intercalative mode of DNA binding. The cleavage reaction on pUC19 DNA was monitored by agarose gel electrophoresis. The results indicate that the Cu(II) complexes can more effectively promote the cleavage of plasmid DNA. The superoxide dismutase mimic activity of the complexes was evaluated by nitroblue tetrazolium assay, and the complexes catalysed the dismutation of superoxide at pH = 7.8 with IC50 values in the range 0.597–0.900 μM. The complexes were screened for their in vitro antibacterial activity against five pathogenic bacteria. All the complexes are good cytotoxic agents and show LC50 values ranging from 5.559 to 11.912 µg ml?1. All newly synthesized Cu(II) complexes were also evaluated for their in vitro antimalarial activity against Plasmodium falciparum strain (IC50 = 0.62–2.0 µg ml?1). Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
38.
39.
40.