全文获取类型
收费全文 | 87780篇 |
免费 | 17734篇 |
国内免费 | 8248篇 |
专业分类
化学 | 77328篇 |
晶体学 | 943篇 |
力学 | 3674篇 |
综合类 | 528篇 |
数学 | 8389篇 |
物理学 | 22900篇 |
出版年
2024年 | 105篇 |
2023年 | 1103篇 |
2022年 | 1217篇 |
2021年 | 2044篇 |
2020年 | 3215篇 |
2019年 | 4383篇 |
2018年 | 2689篇 |
2017年 | 2339篇 |
2016年 | 5578篇 |
2015年 | 5733篇 |
2014年 | 6274篇 |
2013年 | 7805篇 |
2012年 | 7704篇 |
2011年 | 7139篇 |
2010年 | 6191篇 |
2009年 | 6005篇 |
2008年 | 5804篇 |
2007年 | 4910篇 |
2006年 | 4342篇 |
2005年 | 3978篇 |
2004年 | 3373篇 |
2003年 | 2832篇 |
2002年 | 3395篇 |
2001年 | 2572篇 |
2000年 | 2396篇 |
1999年 | 1588篇 |
1998年 | 1112篇 |
1997年 | 959篇 |
1996年 | 959篇 |
1995年 | 891篇 |
1994年 | 803篇 |
1993年 | 660篇 |
1992年 | 597篇 |
1991年 | 498篇 |
1990年 | 469篇 |
1989年 | 320篇 |
1988年 | 292篇 |
1987年 | 247篇 |
1986年 | 198篇 |
1985年 | 196篇 |
1984年 | 169篇 |
1983年 | 150篇 |
1982年 | 98篇 |
1981年 | 71篇 |
1980年 | 64篇 |
1979年 | 37篇 |
1978年 | 31篇 |
1976年 | 31篇 |
1975年 | 35篇 |
1974年 | 25篇 |
排序方式: 共有10000条查询结果,搜索用时 156 毫秒
1.
Zhang Bing Yang Jie-qin Liu Ying Hu Bin Yang Yang Zhao Li Lu Qiang 《Cellulose (London, England)》2022,29(12):6565-6578
Cellulose - Heating is essential in various biomass pre-treatments and thermal conversion processes. It is of practical significance to study the characteristics of cellulose-lignin and... 相似文献
2.
Nonlinear Dynamics - The perovskite solar cell (PSC) is one of the most promising photovoltaic candidates along with the highly increasing demand for green electricity. One of the main concerns... 相似文献
3.
Lin Yu Wu Yeyu Tan Xuecai Wu Jiawen Huang Kejing Mi Yan Ou Panpan Wei Fucun 《Journal of Solid State Electrochemistry》2022,26(4):959-971
Journal of Solid State Electrochemistry - An ultrasensitive “signal-off–on” electrochemiluminescence (ECL) biosensor is constructed based on f1-TiO2/g-C3N4/PDA for thrombin... 相似文献
4.
Yujie Gao Zhiye Qiu Lei Liu Mengmeng Li Bingjie Xu Dan Yu Dongming Qi Jindan Wu 《Journal of polymer science. Part A, Polymer chemistry》2022,60(15):2191-2212
Refractory wounds have always been an important issue to healthcare systems, whose healing process is always delayed by multiple factors, including bacterial infections, chronic inflammation, and excessive exudates, etc. Employing multifunctional wound dressings is recognized as an effective strategy to deal with refractory wounds, which has yielded promising outcomes in recent years. Among these advanced wound dressings, fibrous dressings have gained growing attention due to their unique merits. Such wound dressings have demonstrated great potential in delivering theranostic agents, such as antibacterial agents, anti-inflammatory drugs, growth factors, and diagnostic probes, etc., for the purposes of accelerating wound healing. This paper reviews the development of multifunctional fibrous dressings and their applications in treating refractory wounds. The construction approaches of novel fibrous dressing with capabilities of antibacterial, anti-inflammation, exudate management and diagnosis were also introduced. Furthermore, the existing problems and challenges are also discussed briefly. 相似文献
5.
Saqib Kamal Arif I. Inamdar Kuan-Ru Chiou Batjargal Sainbileg Muhammad Usman Jenq-Wei Chen Tzuoo-Tsair Luo Michitoshi Hayashi Chen-Hsiung Hung Wen-Feng Liaw Kuang-Lieh Lu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(30):e202103905
The dielectric properties of coordination polymers has been a topic of recent interest, but the role of different functional groups on the dielectric properties of these polymers has not yet been fully addressed. Herein, the effects of electron-donating (R=NH2) and electron-withdrawing (R=NO2) groups on the dielectric behavior of such materials were investigated for two thermally stable and guest-free Zn-based coordination polymers, [Zn(L1)(L2)]n ( 1 ) and [Zn(L1)(L3)]n ( 2 ) [L1=2-(2-pyridyl) benzimidazole (Pbim), L2=5-aminoisophthalate (Aip), and L3=5-nitroisophthalate (Nip)]. The results of dielectric studies of 1 revealed that it possesses a high dielectric constant (κ=65.5 at 1 kHz), while compound 2 displayed an even higher dielectric constant (κ=110.3 at 1 kHz). The electron donating and withdrawing effects of the NH2 and NO2 substituents induce changes in the polarity of the polymers, which is due to the inductive effect from the aryl ring for both NO2 and NH2. Theoretical results from density functional theory (DFT) calculations, which also support the experimental findings, show that both compounds have a distinct electronic behavior with diverse wide bandgaps. The significance of the current work is to provide information about the structure-dielectric property relationships. So, this study promises to pave the way for further research on the effects of different functional groups on coordination polymers on their dielectric properties. 相似文献
6.
Cellulose - In this research, the production of levoglucosan (LG) and levoglucosenone (LGO) was improved from acid-impregnated cellulose via fast pyrolysis. Thermogravimetric and kinetic analysis... 相似文献
7.
Hua Saixiang Zhu Huichao Wang Xiao Wu Mingyuan Wu Qingyun Liu Jiuyi Yang Jianjun Zhang Jianan 《Cellulose (London, England)》2022,29(13):7465-7475
Cellulose - Ultraviolet (UV) protective cotton fabric is a convenient and reliable way to protect human body from sunlight. Herein, a polymerizable UV-absorber,... 相似文献
8.
9.
科学评价大学生科研创新能力对我国科研水平的提高具有重要意义.采用机器学习模型来预测大学生科研能力可以起到良好的效果,提出一种GAXGBoost模型来实现对大学生的科研能力预测.此模型是以Xgboost算法为基础,然后充分利用遗传算法的全局搜索能力自动搜索Xgboost最优超参数,避免了人为经验调参不准确的缺陷,最后采用精英选择策略以此确保每一轮都是最佳的进化结果.通过分析表明,所采用的GAXGBoost模型在大学生科研能力预测的结果中具有很高的精度,将此模型与Logistic Regression、Random Forest、SVM等模型进行对比,GAXGBoost模型的预测精度最高. 相似文献
10.
Liu Jingze Fei Qingguo Wu Shaoqing Tang Zhenhuan Zhang Dahai 《Nonlinear dynamics》2021,106(3):1869-1890
Nonlinear Dynamics - Rolling bearing and squeeze film damper will introduce structural nonlinearity into the dynamic model of aeroengine. Rubbing will occur due to the clearance reduction design of... 相似文献