全文获取类型
收费全文 | 245087篇 |
免费 | 7347篇 |
国内免费 | 3862篇 |
专业分类
化学 | 139369篇 |
晶体学 | 3613篇 |
力学 | 10113篇 |
综合类 | 142篇 |
数学 | 26272篇 |
物理学 | 76787篇 |
出版年
2022年 | 2374篇 |
2021年 | 2936篇 |
2020年 | 3327篇 |
2019年 | 3597篇 |
2018年 | 4330篇 |
2017年 | 4108篇 |
2016年 | 5809篇 |
2015年 | 3798篇 |
2014年 | 5675篇 |
2013年 | 11547篇 |
2012年 | 9674篇 |
2011年 | 11280篇 |
2010年 | 7921篇 |
2009年 | 7689篇 |
2008年 | 10096篇 |
2007年 | 9921篇 |
2006年 | 9233篇 |
2005年 | 8183篇 |
2004年 | 7116篇 |
2003年 | 6394篇 |
2002年 | 6242篇 |
2001年 | 6505篇 |
2000年 | 5137篇 |
1999年 | 4054篇 |
1998年 | 3512篇 |
1997年 | 3524篇 |
1996年 | 3311篇 |
1995年 | 2744篇 |
1994年 | 2759篇 |
1993年 | 2726篇 |
1992年 | 2872篇 |
1991年 | 2875篇 |
1990年 | 2754篇 |
1989年 | 2680篇 |
1988年 | 2553篇 |
1987年 | 2512篇 |
1986年 | 2460篇 |
1985年 | 3110篇 |
1984年 | 3228篇 |
1983年 | 2603篇 |
1982年 | 2854篇 |
1981年 | 2725篇 |
1980年 | 2510篇 |
1979年 | 2720篇 |
1978年 | 2833篇 |
1977年 | 2856篇 |
1976年 | 2833篇 |
1975年 | 2688篇 |
1974年 | 2665篇 |
1973年 | 2810篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
Development of biocompatible porous supports is a promising strategy in the field of tissue engineering for the repair and regeneration of bone tissues with severe damage. Graphene oxide aerogels (GOAs) are excellent candidates for the manufacture of these systems due to their porosity, ability to imitate bone structure, and mechanical resistance, and according to their surface chemical reactivity, they can facilitate osseointegration, osteogenesis, osteoinduction and osteoconduction. In this review, synthesis of GOAs from the most primary source is described, and recent studies on the use of these functionalized carbonaceous foams as scaffolding for bone tissue regeneration are presented. 相似文献
52.
Elasasy M. E. A. Elnaggar D. H. Hafez N. A. Abdel Azab M. E. Amr A. E. Omran M. M. Mohamed A. M. 《Russian Journal of General Chemistry》2021,91(5):915-925
Russian Journal of General Chemistry - Some new fluoro-heterocyclic compounds containing thiazole and pyridine moities have been synthesized and studied for their antiproliferative activity.... 相似文献
53.
The biodegradability of phtalic acid esters in marine and freshwater environments was characterized by their binding free energy with corresponding degrading enzymes. According to comprehensive biodegradation effects weights, the binding free energy values were converted into dimensionless efficacy coefficient using ratio normalization method. Then, considering comprehensive dual biodegradation effects value and the structural parameters of PAEs in both marine and freshwater environments, a 3D-QSAR pharmacophore model was constructed, five PAE derivatives (DBP−COOH, DBP−CHO, DBP−OH, DINP−NH2, and DINP−NO2) were screened out based on their environmental friendliness, functionality and stability. The prediction of biodegradation effects on five PAE derivatives by biodegradation models in marine and freshwater environment increased by 15.90 %, 15.84 %, 27.21 %, 12.33 %, and 8.32 %, and 21.57 %, 15.21 %, 20.99 %, 15.10 %, and 9.74 %, respectively. By simulating the photodegradation path of the PAE derivative molecular, it was found that DBP−OH can generate .OH and provides free radicals for the photodegradation of microplastics in the environment. 相似文献
54.
55.
Applied Magnetic Resonance - The suggested approach allowed us to derive analytical expressions for modeling the shape of solid-echo signal and its time evolution for a system of three-spin groups... 相似文献
56.
57.
58.
59.
Terahertz(THz) wave emission from argon atom in a two-color laser pulses is studied numerically by solving the one-dimensional(1D) time-dependent Schr ¨odinger equation. The THz spectra we obtained include both discontinuous and continuum ones. By using the special basis functions that we previously proposed, our analysis points out that the discontinuous and continuum parts are contributed by bound–bound and continuum–continuum transition of atomic energy levels. Although the atomic wave function is strongly dressed during the interaction with laser fields, our identification for the discontinuous part of the THz wave shows that the transition between highly excited bound states can still be well described by the field-free basis function in the tunneling ionization regime. 相似文献
60.
Physics of Atomic Nuclei - We have studied the mechanisms influencing production of cumulative pions and protons in the fragmentation of the incident deuterons into cumulative pions and protons... 相似文献