全文获取类型
收费全文 | 66733篇 |
免费 | 11564篇 |
国内免费 | 7638篇 |
专业分类
化学 | 46431篇 |
晶体学 | 838篇 |
力学 | 4283篇 |
综合类 | 556篇 |
数学 | 7828篇 |
物理学 | 25999篇 |
出版年
2024年 | 68篇 |
2023年 | 1371篇 |
2022年 | 1463篇 |
2021年 | 1989篇 |
2020年 | 2620篇 |
2019年 | 2599篇 |
2018年 | 2212篇 |
2017年 | 2106篇 |
2016年 | 3145篇 |
2015年 | 3097篇 |
2014年 | 3755篇 |
2013年 | 4889篇 |
2012年 | 6047篇 |
2011年 | 6473篇 |
2010年 | 4382篇 |
2009年 | 4186篇 |
2008年 | 4530篇 |
2007年 | 4221篇 |
2006年 | 3789篇 |
2005年 | 3108篇 |
2004年 | 2436篇 |
2003年 | 2013篇 |
2002年 | 1780篇 |
2001年 | 1414篇 |
2000年 | 1442篇 |
1999年 | 1397篇 |
1998年 | 1157篇 |
1997年 | 1120篇 |
1996年 | 1052篇 |
1995年 | 985篇 |
1994年 | 925篇 |
1993年 | 751篇 |
1992年 | 678篇 |
1991年 | 564篇 |
1990年 | 512篇 |
1989年 | 379篇 |
1988年 | 283篇 |
1987年 | 208篇 |
1986年 | 191篇 |
1985年 | 170篇 |
1984年 | 116篇 |
1983年 | 82篇 |
1982年 | 72篇 |
1981年 | 50篇 |
1980年 | 25篇 |
1979年 | 20篇 |
1977年 | 8篇 |
1976年 | 8篇 |
1975年 | 8篇 |
1957年 | 12篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Journal of Applied Spectroscopy - The concentration of heavy metals in drinking water is an important standard for water quality evaluation and water pipeline corrosion detection. This research... 相似文献
2.
Yin Qingqing Xu Fen Sun Lixian Li Yaying Liao Lumin Wang Tao Guan Yanxun Xia Yongpeng Zhang Chenchen Wei Sheng Zhang Huanzhi Li Bin 《Journal of Thermal Analysis and Calorimetry》2022,147(12):6583-6592
Journal of Thermal Analysis and Calorimetry - Polyethylene glycol (PEG) is widely used as phase change materials (PCMs). However, the leakage and low thermal conductivity issues restrict its... 相似文献
3.
4.
5.
Structural Chemistry - In order to evaluate the electrical response of boron nitride nanocones (BNNCs) to phenol gas, density functional theory (DFT) calculations are employed. The sensitivity and... 相似文献
6.
7.
Baoquan Zhou Daqing Jiang Bingtao Han Tasawar Hayat 《Mathematical Methods in the Applied Sciences》2022,45(1):423-455
Considering the effect of stochasticity including white noise and colored noise, this paper aims to study a hybrid stochastic cholera epidemic model with waning vaccine-induced immunity and nonlinear telegraph perturbations. First, we derive a critical value related to the basic reproduction number of the deterministic model. The key aim of this paper is to generalize the θ-stochastic criterion method proposed by the recent work (Han et al. in Chaos Solit Fract 140:110238, 2020) to eliminate nonlinear telegraph perturbations. Next, via constructing several θ-stochastic Lyapunov functions and using the generalized method, we further prove that the stochastic model have a unique ergodic stationary distribution under . Results show that the prevention and control of cholera epidemic depend on low transmission rate and small telegraph perturbations. Finally, the corresponding numerical simulations are performed to illustrate our analytical results and a practical application on the Somalia cholera outbreak is shown at the end of this paper. 相似文献
8.
Journal of Algebraic Combinatorics - Highly nonlinear functions (bent functions, perfect nonlinear functions, etc.) on finite fields and finite (abelian or nonabelian) groups have been studied in... 相似文献
9.
Acta Mathematicae Applicatae Sinica, English Series - In this paper, we investigate a delayed HIV infection model that considers the homeostatic proliferation of CD4+ T cells. The existence and... 相似文献
10.
Hao Lu Xiaodong Wang Hang Wang Andong Zhang Xinming Zheng Na Yu Zheng Tang Xinjun Xu Yahui Liu Ya-Nan Chen Zhishan Bo 《中国科学:化学(英文版)》2022,65(3):594-601
Three nonfused ring electron acceptors (NFREAs) TTC6,TT-C8T and TT-TC8 were purposefully designed and synthesized.The molecular geometry can be adjusted by the steric hindrance of lateral substituents.According to the DFT calculations,from TTC6 to TT-C8T and TT-TC8,planarity of the molecular backbone is gradually improved,accompanying with the enhancing of intramolecular charge transfer effect.As for TT-TC8,the two phenyl substituents are almost perpendicular to the molecular backbone,which endues the acceptor with good solubility and suppresses it to form over-aggregation.Multidirectional regular molecular orientation and closer molecular stacking are formed in TT-TC8 film.As a result,TT-TC8 based devices afford the highest PCE of 13.13%,which is much higher than that of TTC6 (4.41%) and TT-C8T (10.42%) and among the highest PCE values based on NFREAs. 相似文献