全文获取类型
收费全文 | 12588篇 |
免费 | 1800篇 |
国内免费 | 1523篇 |
专业分类
化学 | 8521篇 |
晶体学 | 155篇 |
力学 | 930篇 |
综合类 | 108篇 |
数学 | 1549篇 |
物理学 | 4648篇 |
出版年
2023年 | 184篇 |
2022年 | 195篇 |
2021年 | 290篇 |
2020年 | 416篇 |
2019年 | 382篇 |
2018年 | 332篇 |
2017年 | 310篇 |
2016年 | 483篇 |
2015年 | 478篇 |
2014年 | 624篇 |
2013年 | 862篇 |
2012年 | 958篇 |
2011年 | 1048篇 |
2010年 | 712篇 |
2009年 | 776篇 |
2008年 | 812篇 |
2007年 | 779篇 |
2006年 | 725篇 |
2005年 | 667篇 |
2004年 | 516篇 |
2003年 | 411篇 |
2002年 | 343篇 |
2001年 | 322篇 |
2000年 | 288篇 |
1999年 | 338篇 |
1998年 | 338篇 |
1997年 | 271篇 |
1996年 | 276篇 |
1995年 | 245篇 |
1994年 | 250篇 |
1993年 | 165篇 |
1992年 | 157篇 |
1991年 | 136篇 |
1990年 | 145篇 |
1989年 | 86篇 |
1988年 | 81篇 |
1987年 | 92篇 |
1986年 | 86篇 |
1985年 | 74篇 |
1984年 | 48篇 |
1983年 | 33篇 |
1982年 | 35篇 |
1981年 | 26篇 |
1980年 | 20篇 |
1979年 | 16篇 |
1978年 | 14篇 |
1977年 | 8篇 |
1976年 | 8篇 |
1973年 | 10篇 |
1970年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 192 毫秒
61.
Wei Yao Zhoufeng Shen Yi Yu Guanghong Ding 《Mathematical Methods in the Applied Sciences》2020,43(4):1555-1564
Acupuncture, a physiotherapy, has been widely accepted all around the world. This study focuses on the influence of membrane structures and explains the acupuncture sensations from the aspect of mechanical properties. By mathematical modeling and numerical simulation, the scientific meaning of the acupuncture depth is investigated and phenomena and theory of acupuncture are discussed. The simulation results show that (a) the fascial structure is the main contributor to the force on the needle, the axial force will gradually increase before piercing the fascial, and suddenly decrease after piercing the fascial; (b) there is an inverse relationship between the needle radius and the maximum radial stress, which indicates that the needle should not be too sharp to cause local stress concentration and piece the fascia layer; and (c) the simulation results of comprehensively considering the static friction and sliding friction is identical with the experiment results. This study proposes a preliminary study of mechanical effects of acupuncture manipulation, clarifies key factors affecting the stress on the needle, and explains the objective requirement of acupuncture depth to effective treatment. 相似文献
62.
Dr. Yukun Zhu Chunxiao Lv Zhuocheng Yin Prof. Jun Ren Prof. Xianfeng Yang Prof. Chung-Li Dong Prof. Hongwei Liu Dr. Rongsheng Cai Yu-Cheng Huang Prof. Wolfgang Theis Prof. Shaohua Shen Prof. Dongjiang Yang 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(2):878-883
Red phosphorus is a promising photocatalyst with wide visible-light absorption up to 700 nm, but the fast charge recombination limits its photocatalytic hydrogen evolution reaction (HER) activity. Now, [001]-oriented Hittorf's phosphorus (HP) nanorods were successfully grown on polymeric carbon nitride (PCN) by a chemical vapor deposition strategy. Compared with the bare PCN and HP, the optimized PCN@HP hybrid exhibited a significantly enhanced photocatalytic activity, with HER rates reaching 33.2 and 17.5 μmol h−1 from pure water under simulated solar light and visible light irradiation, respectively. It was theoretically and experimentally indicated that the strong electronic coupling between PCN and [001]-oriented HP nanorods gave rise to the enhanced visible light absorption and the greatly accelerated photoinduced electron–hole separation and transfer, which benefited the photocatalytic HER performance. 相似文献
63.
High-power fiber-to-fiber coupling is extensively used in fiber laser applications,and its performance is determined by coupling efficiency.We demonstrate a novel method for alignment and monitoring efficiency by detecting backscattering power at the fiber end cap.The relationship between alignment error and backscattering power is determined by simulations and experiments.Through this method,a state-of-the-art kW-level fiberto-fiber optic switch is developed(transmission efficiency>97%).It performs well for longer than 60 min.To the best of our knowledge,it is the first time to establish the mathematical model based on this method.Our results can provide guidance in high-power fiber-to-fiber coupling. 相似文献
64.
Shujue Xu Shen Zhang Yang Yu Shengrui Zhang Prof. Minjie Li 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(67):e202201968
Two-dimensional (2D) Au(I)-thiolate assemblies are a special type of material that can balance high structural stability and rich surface functionality, which shows promising prospects in both fundamental research and applications. Co-assembly of multiple ligands is a facile way to further enrich the surface properties and functions, and expand their application potentials. In this work, taking 3-mercaptopropionic acid (MPA), cysteine (Cys) and 1-thioglycerol (TGO) as example ligands, we studied in detail the possibility to co-assemble them into one nanosheet. Although the three ligands have significantly different controllability and pathways when self-assembling individually with Au(I), they can still be effectively co-assembled by reacting with HAuCl4 together to obtain three-ligand nanosheets with good colloidal stability. The key points for successful co-assembly are also revealed by comparing single- and three-ligand self-assembly processes, laying a solid foundation for co-assembly of even more ligands. The easy but powerful strategy for 2D materials with closely-packed and multiple tunable surface functional groups addresses the surface engineering problem for 2D materials and paves the way for their wider applications in sensing and biomaterials. 相似文献
65.
Ping Lv Xin Shen Zhiliyu Cui Bo Li Qiangqiang Xu Zhuo Yu Weijie Lu Haonan Shao Yan Ge Zhenhui Qi 《Journal of polymer science. Part A, Polymer chemistry》2021,59(23):3001-3008
Fiber-reinforced-concrete (FRC) mechanism refers short discrete fibers that are uniformly distributed and randomly oriented, which offers an effective way to improve the mechanical performance of concrete. In the design of supramolecular polymers, an analogous concept of FRC appears to have been considered very rarely-although fibrous structure has been frequently observed/generated during the supramolecular polymerization. In this work, we apply the alkane thermosets, octadecane (C18H38) and tetracosane (C24H50), taking the role of “concrete”, and the low-molecular-weight monomer with long alkyl chains as the essential “fiber” component, to fabricate the “fiber reinforced supramolecular polymer”. Very much like FRC mechanism in material science, the resulting fiber reinforced supramolecular polymer thus exhibit unusually high mechanical strength and stiffness, which is unprecedented in the conventional supramolecular strategy. 相似文献
66.
Nitrogen-containing flame retardants have been extensively applied due to their low toxicity and smoke-suppression properties; however, their poor charring ability restricts their applications. Herein, a representative nitrogen-containing flame retardant, polyheptanazine, was investigated. Two novel, cost-effective phosphorus-doped polyheptazine (PCN) and cobalt-anchored PCN (Co@PCN) flame retardants were synthesized via a thermal condensation method. The X-ray photoelectron spectroscopy (XPS) results indicated effective doping of P into triazine. Then, flame-retardant particles were introduced into thermoplastic polyurethane (TPU) using a melt-blending approach. The introduction of 3 wt% PCN and Co@PCN could remarkably suppress peak heat release rate (pHRR) (48.5% and 40.0%), peak smoke production rate (pSPR) (25.5% and 21.8%), and increasing residues (10.18 wt%→17.04 wt% and 14.08 wt%). Improvements in charring stability and flame retardancy were ascribed to the formation of P–N bonds and P=N bonds in triazine rings, which promoted the retention of P in the condensed phase, which produced additional high-quality residues. 相似文献
67.
Journal of Visualization - Convolutional neural networks (CNNs) have achieved breakthrough performance in image recognition and classification. However, it is still a challenge for CNNs to classify... 相似文献
68.
Cheng Jiang Lisha Zhao Chuanwei Xin Yu Dong Jie Shen Zhongni Xia Dan Shou Gonghua Li 《Biomedical chromatography : BMC》2022,36(2):e5255
The allergic reaction (AR) of Chinese herbal injection (CHI) has become one of the most noticeable focuses of public health in China. However, it still remains a considerable controversy as to whether low-molecular-weight components in CHI have potential sensitization. In this study, the relationship between AR and low-molecular-weight component profile of Shenmai injection was explored by an interdisciplinary technology integrating real-world evidence and ultra-performance liquid chromatography–quadrupole time-of-flight mass spectroscopy (UPLC–Q-TOF-MS). The AR information of hospitalized patients was obtained by comprehensively analyzing real-world evidence from January 2015 to June 2019 at two Chinese hospitals. The UPLC–Q-TOF-MS was exploited to systematically investigate the low-molecular-weight component profile with 50–1500 m/z mass range, and 3725 MS1 peaks were detected. The optimized partial least squares discriminant analysis model was established to map the influence of low-molecular-weight components on AR. The results of this study showed that high levels of organic acids administered intravenously might be a potential risk factor for inducing AR. By using this method, Shenmai injection with high AR risk could be recognized precisely with 100% accuracy before clinical use. 相似文献
69.
Xiao Yuanxiang Shen Guokang Zheng Weishi Fu Jiajia Fu Feiya Hu Xinyue Jin Ziyi Liu Xiangdong 《Cellulose (London, England)》2022,29(2):1003-1015
Cellulose - We report here a simple and effective method applying a combination of chitosan (Cs) and Cu(II) ion to fabricate antibacterial cotton fabric with a remarkable durability against... 相似文献
70.
Optical Review - We propose a spatial mode compensation method using progressive phase conjugation (PPC) to establish a dynamic control technology for mode distribution in multi-mode fiber (MMF).... 相似文献