全文获取类型
收费全文 | 2154篇 |
免费 | 192篇 |
国内免费 | 124篇 |
专业分类
化学 | 1150篇 |
晶体学 | 27篇 |
力学 | 89篇 |
综合类 | 8篇 |
数学 | 348篇 |
物理学 | 430篇 |
无线电 | 418篇 |
出版年
2023年 | 41篇 |
2022年 | 70篇 |
2021年 | 85篇 |
2020年 | 86篇 |
2019年 | 87篇 |
2018年 | 83篇 |
2017年 | 75篇 |
2016年 | 141篇 |
2015年 | 94篇 |
2014年 | 111篇 |
2013年 | 146篇 |
2012年 | 124篇 |
2011年 | 139篇 |
2010年 | 101篇 |
2009年 | 95篇 |
2008年 | 94篇 |
2007年 | 94篇 |
2006年 | 87篇 |
2005年 | 81篇 |
2004年 | 60篇 |
2003年 | 46篇 |
2002年 | 33篇 |
2001年 | 27篇 |
2000年 | 39篇 |
1999年 | 31篇 |
1998年 | 21篇 |
1997年 | 15篇 |
1996年 | 29篇 |
1995年 | 34篇 |
1994年 | 22篇 |
1993年 | 20篇 |
1992年 | 19篇 |
1991年 | 28篇 |
1990年 | 13篇 |
1989年 | 7篇 |
1988年 | 9篇 |
1987年 | 7篇 |
1986年 | 9篇 |
1985年 | 18篇 |
1984年 | 6篇 |
1983年 | 16篇 |
1982年 | 11篇 |
1981年 | 19篇 |
1980年 | 13篇 |
1978年 | 15篇 |
1977年 | 11篇 |
1976年 | 11篇 |
1975年 | 6篇 |
1974年 | 6篇 |
1973年 | 13篇 |
排序方式: 共有2470条查询结果,搜索用时 15 毫秒
991.
Anh Quang Dao Le Thi Thanh Nhi Do Mai Nguyen Tran Thanh Tam Toan 《Biomedical chromatography : BMC》2022,36(6):e5364
In this paper, we discuss veterinary medicine and its applications in the food industry as well as the risk to the health of humans and animals caused by these residues. We review how the veterinary residues enter and cause some detrimental effects. We also mention two techniques to determine the residue of veterinary medications that exist in food originating from animals, including classic and advanced techniques. Finally, we discuss the potential of various developed methods and compare them with some traditional techniques. 相似文献
992.
Lulu Wang Minjie Liu Meifen Jiang Li Wan Weijian Li Prof. Dang Cheng Prof. Fener Chen 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(45):e202201420
Diclofenac sodium is a widely used nonsteroidal anti-inflammatory drug (NSAID) as over-the-counter (OTC) medication for the treatment of inflammatory diseases. Herein, the development of an intensified six-step continuous flow synthesis of diclofenac sodium from commercially available aniline and chloroacetic acid is described. A challenging and unprecedented etherification/Smiles rearrangement cascade of 2-chloro-N-phenylacetamide and 2,6-dichlorophenol into hydroxyacetyldiphenylamine operated with the precise control of reaction conditions in continuous flow was realized as the key step in this multistep synthetic chemistry. The undesired amide hydrolysis in Smiles rearrangement was addressed and the extra installation of N-chloroacetyl group in current industrial batch mode was avoided. Diclofenac sodium was obtained in 63 % isolated yield with an average yield of above 90 % for each step in a total residence time of 205 min. 相似文献
993.
Lingna Wang Jianbo Zhang Chunmei Li Wanbin Dang Wei Guo Junjian Xie Fengtao Zhou Qiuyu Zhang 《Macromolecular rapid communications》2024,45(9):2300652
Pyrrole-based polymers ( PBPs ), a type of fascinating functional polymers, play a crucial role in materials science. However, efficient synthetic strategies of PBPs with diverse structures are mainly focused on conjugated polypyrroles and still remain challenging. Herein, an atom and step economy protocol is described to access various 2,4-disubstituted PBPs by in situ formation of pyrrole core structure via copper-catalyzed [3+2] polycycloaddition of dialkynones and diisocyanoacetates. A series of PBPs is prepared with high molecular weight (Mw up to 18 200 Da) and moderate to good yield (up to 87%), which possesses a fluorescent emission located in the green to yellow light region. Blending the PBPs with polyvinyl alcohol, the stretchable composite films exhibit a significant strengthening of the mechanical properties (tensile stress up to 59 MPa, elongation at break >400%) and an unprecedented stress-responsive luminescence enhancement that over fourfold fluorescent emission intensity is maintained upon stretching up to 100%. On the basis of computational studies, the unique photophysical and mechanical properties are attributed to the substitution of carbonyl chromophores on the pyrrole unit. 相似文献
994.
In this paper, generalized random linear mappings are viewed as random field indexed by random parameters. This point of view leads to questions about sample paths properties. We obtain various necessary and sufficient conditions ensuring the existence of nice sample paths of a generalized random linear mapping. We also give illustrative examples and applications. 相似文献
995.
In order to understand the effects of the landfill operation on groundwater flow behavior, 2D horizontal groundwater simulation model was carried out. The model saved the memory of computer and time consumption comparing with 3D groundwater flow model. However, the most difficulty is the assignment of collecting pipe boundary in the study site. Therefore, 2D vertical model was applied to calculate the change of groundwater table above the collecting pipe. This paper paid attention to examine the validation of the assignment of the collecting pipe boundary by applying the results of 2D vertical model. 2D horizontal model was coupled with the recharge model to solve the partial differential equation of groundwater flow. Finite difference method and iterative successive over relaxation were applied. The drainage volume of leachate collection was summed up in the whole landfill site and compared with the average volume of treated waste water. The study demonstrated that the results of 2D vertical model validated and can be applied to 2D horizontal groundwater flow simulation. 相似文献
996.
Luong Dang Ky 《分析论及其应用》2011,27(3):251-264
Let 0 p ≤ 1 and w in the Muckenhoupt class A1. Recently, by using the weighted atomic decomposition and molecular characterization, Lee, Lin and Yang[11] es- tablished that the Riesz transforms Rj, j = 1,2,··· ,n, are bounded on Hwp(Rn). In this note we extend this to the general case of weight w in the Muckenhoupt class A∞ through molec- ular characterization. One difficulty, which has not been taken care in [11], consists in passing from atoms to all functions in Hwp(Rn). Furthermore, the Hwp-boundedness of θ- Calderón-Zygmund operators are also given through molecular characterization and atomic decomposition. 相似文献
997.
Xinghui Liu Lirong Zheng Chenxu Han Hongxiang Zong Guang Yang Shiru Lin Ashwani Kumar Amol R. Jadhav Ngoc Quang Tran Yosep Hwang Jinsun Lee Suresh Vasimalla Zhongfang Chen Seong-Gon Kim Hyoyoung Lee 《Advanced functional materials》2021,31(18):2100547
Single-atom catalysts (SACs) have become the forefront of energy conversion studies, but unfortunately, the origin of their activity and the interpretation of the synchrotron spectrograms of these materials remain ambiguous. Here, systematic density functional theory computations reveal that the edge sites—zigzag and armchair—are responsible for the activity of the graphene-based Co (cobalt) SACs toward hydrogen evolution reaction (HER). Then, edge-rich (E)-Co single atoms (SAs) were rationally synthesized guided by theoretical results. Supervised learning techniques are applied to interpret the measured synchrotron spectrum of E-Co SAs. The obtained local environments of Co SAs, 65.49% of Co-4N-plane, 13.64% in Co-2N-armchair, and 20.86% in Co-2N-zigzag, are consistent with Athena fitting. Remarkably, E-Co SAs show even better HER electrocatalytic performance than commercial Pt/C at high current density. Using the joint effort of theoretical modeling, thorough characterization of the catalysts aided by supervised learning, and catalytic performance evaluations, this study not only uncovers the activity origin of Co SACs for HER but also lays the cornerstone for the rational design and structural analysis of nanocatalysts. 相似文献
998.
Helena H. Chubatsu Nunes Trinh-Don Nguyen Thu-Thuy T. Dang 《Current Opinion in Green and Sustainable Chemistry》2022
Many small-molecule chemicals from plants display extraordinarily complex structures and potent bioactivities with significant pharmacological and industrial implications. While the medicinal and economic relevance of plants' bioactive compounds is widely recognized, their industrial-scale chemical synthesis for distribution and development of new derivatives is hampered by challenges associated with their structural complexity. Extraction from the native plants is usually not viable due to the chemicals' low natural abundance, and the plants’ sub-optimal growing conditions due to climate change and the destruction of natural habitats. All of these challenges ultimately highlight the need to expand the (bio)chemical toolbox with strategies that support continuous discovery and sustainable production of relevant chemicals. This article highlights some of the most recent discoveries of plant-derived biocatalysts and how they pave the way for more sustainable and greener approaches to produce chemicals with unmatched complexity and applications. 相似文献
999.
Power Beacon-Based Wireless Power Transfer in MISO/SISO: An Application in Device-to-Device Networks
Dang Huu-Phuc Le Chi-Bao Do Dinh-Thuan Le Si-Phu Nguyen Hong-Nhu Voznak Miroslav 《Wireless Personal Communications》2020,110(1):381-402
Wireless Personal Communications - This paper considers device-to-device (D2D) together with single input single output and multiple input single output models in transmitting of nearby devices... 相似文献
1000.
Huynh Hiep Xuan Dang Huy Quang Luong Huong Hoang Ong Linh My Thi Duong-Trung Nghia Huynh Toan Phung Pham Van-Huy Pottier Bernard 《Mobile Networks and Applications》2020,25(3):1140-1150
Mobile Networks and Applications - The brown planthopper (BPH) is a crucial pest of rice in tropical zones like the Mekong Delta of Vietnam. It economically causes severe loss to the rice harvest... 相似文献