全文获取类型
收费全文 | 4105篇 |
免费 | 702篇 |
国内免费 | 367篇 |
专业分类
化学 | 2733篇 |
晶体学 | 54篇 |
力学 | 295篇 |
综合类 | 17篇 |
数学 | 429篇 |
物理学 | 1646篇 |
出版年
2024年 | 10篇 |
2023年 | 110篇 |
2022年 | 128篇 |
2021年 | 167篇 |
2020年 | 160篇 |
2019年 | 160篇 |
2018年 | 155篇 |
2017年 | 123篇 |
2016年 | 216篇 |
2015年 | 194篇 |
2014年 | 228篇 |
2013年 | 304篇 |
2012年 | 395篇 |
2011年 | 396篇 |
2010年 | 267篇 |
2009年 | 221篇 |
2008年 | 246篇 |
2007年 | 242篇 |
2006年 | 227篇 |
2005年 | 181篇 |
2004年 | 136篇 |
2003年 | 113篇 |
2002年 | 86篇 |
2001年 | 76篇 |
2000年 | 86篇 |
1999年 | 72篇 |
1998年 | 66篇 |
1997年 | 59篇 |
1996年 | 58篇 |
1995年 | 55篇 |
1994年 | 36篇 |
1993年 | 43篇 |
1992年 | 42篇 |
1991年 | 25篇 |
1990年 | 22篇 |
1989年 | 16篇 |
1988年 | 14篇 |
1987年 | 7篇 |
1986年 | 6篇 |
1985年 | 11篇 |
1984年 | 2篇 |
1983年 | 6篇 |
1981年 | 2篇 |
1980年 | 2篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1957年 | 1篇 |
排序方式: 共有5174条查询结果,搜索用时 15 毫秒
161.
162.
Dr. Dongpeng Yan Dr. Dejan‐Krešimir Bučar Dr. Amit Delori Bhavnita Patel Dr. Gareth O. Lloyd Prof. William Jones Prof. Xue Duan 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(25):8213-8219
Multi‐component organic nanocrystals that are comprised of two or more supramolecular building blocks can be used to extend the design and assembly scope of solid molecular materials. Herein, we report the use of ultrasonication to prepare halogen‐bonded stilbene‐based nano‐cocrystals that exhibit different photoemission properties, including one‐ and two‐phonon emission and fluorescence lifetimes, relative to those of macrodimensional crystals. The structural transformation from nano‐cocrystals into nanocrystals upon heating results in a luminescence red‐shift from greenish blue to yellow. The temperature‐dependent ratiometric luminescence may allow such nano‐cocrystals to be used as fluorescent sensors and thermosensitive materials. 相似文献
163.
Ben Liu Yuanyuan Cao Yingying Duan Prof. Shunai Che 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(48):16382-16388
Chirality is widely found in nature and is expressed hierarchically in many organic–inorganic hybrid materials. Optical activity (OA) is the most fundamental attribute of these chiral materials. In this study, we found that the OA of impeller‐like chiral DNA–silica assemblies (CDSAs) was inverted with the addition of water. The state of DNA under dry and wet conditions, and the dual chirality of chiral DNA layers and twisted helical arrays of opposite handedness in CDSAs were considered to exert predominant effects on the OAs. The circular dichroism (CD) responses for the dry CDSAs were mostly attributed to the chiral arrangement of DNA layers, whereas the opposite CD responses for the wet CDSAs primarily originated from twisted helical arrays of DNA molecules. The observed CD signals were a super‐position of the two opposing OA responses. The increase in the longitudinal relation of DNA molecules due to the recovery of a double‐helical structure of DNA in the presence of water was considered to be the reason for the increase in intensity of the CD signals that originated from the twisted helical array, which led to the inversion of OA of the CDSAs. The inversion of the plasmon‐resonance‐based OAs for the chiral‐arranged achiral Ag nanoparticles (NPs) located in the channels of the CDSAs in dry and wet states further confirmed the dual chirality of DNA packing. Such research on DNA assemblies and metal NPs with dual, opposite chirality assists in the understanding of DNA hierarchical chirality in living systems and the creation of macroscopic ordered helical materials and biosensors. 相似文献
164.
为实现对循环水水质的远程监测,设计并开发了一种基于嵌入式技术的热力站远程水质监测系统的监测终端。监测终端由水质传感器、GPRS模块、通信转换模块及嵌入式开发板组成。嵌入式开发板以ARM11系列的Tiny6410为硬件基础,并嵌入WinCE系统作为软件平台,同时加入SQLite数据库以实现将水质传感器采集到的氯离子、PH值、溶解氧等参数的本地存储、查询及图表显示。最后监测终端通过GPRS模块与数据中心建立无线连接,接收数据中心的配置命令,并将现场测得数据发送到远端数据中心。调试结果表明:远程监测终端实现了循环水水质远程监测的功能要求,对于实现水质自动化监测具有一定的理论意义和实用价值。 相似文献
165.
Pseudo almost periodic dynamics of delay Nicholson's blowflies model with a linear harvesting term 下载免费PDF全文
In this paper, we investigate a class of delay Nicholson's blowflies model with a linear harvesting term, new criteria for the existence and convergence dynamics of positive pseudo almost periodic solutions are established by using the fixed point method and the properties of pseudo almost periodic function, together with constructing suitable Lyapunov functionals. The obtained results extend previously known results, and they also partially answer an open problem proposed by L. Berezansky et al. Finally, an example with simulation is presented to demonstrate the effectiveness of theoretical results. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
166.
An asymmetric 1,6-addition of diphenylphosphine to (4-aryl-1,3-butadienylidene)bis(phosphonates) catalyzed by a PCP pincer–Pd complex has been developed for the synthesis of chiral allylic phosphines with up to 91% ee under mild conditions. 相似文献
167.
Long Tang Liang Bai Yaping Duan Wei Xia Wenwen Dong Dongsheng Li 《无机化学与普通化学杂志》2014,640(11):2268-2273
Three ZnII and CdII complexes with Y‐shaped dicarboxylate ligands, namely [Zn(L1)(2,2′‐bpy)2(H2O)] · 2H2O ( 1 ), [Zn(L1)(bpp)(H2O)] ( 2 ), and [Cd(L1)(H2O)] · H2O ( 3 ) [H2L1 = N‐phenyliminodiacetic acid, 2,2′‐bpy = 2,2′‐bipyridine, bpp = 1,3‐bis(4‐pyridyl)propane] were synthesized and characterized by elemental analysis, IR spectroscopy single‐crystal X‐ray diffraction, and thermogravimetric analyses. Compound 1 shows an hydrogen‐bonded 2D network, whereas compound 2 is an infinite 1D wavy chain structure, though O–H ··· O hydrogen‐bonded to form a 2D network. Compound 3 displays a 2D uninodal 3‐connected Shubnikov plane net with the point symbol of (4.82). Moreover, the solid‐state such as thermal stabilities and fluorescence properties of 1 – 3 were also investigated. 相似文献
168.
169.
Development of a solid‐phase microextraction fiber by the chemical binding of graphene oxide on a silver‐coated stainless‐steel wire with an ionic liquid as the crosslinking agent 下载免费PDF全文
Min Sun Juanjuan Feng Yanan Bu Huimin Duan Xiaojiao Wang Chuannan Luo 《Journal of separation science》2014,37(24):3691-3698
Graphene oxide was bonded onto a silver‐coated stainless‐steel wire using an ionic liquid as the crosslinking agent by a layer‐by‐layer strategy. The novel solid‐phase microextraction fiber was characterized by scanning electron microscopy, energy‐dispersive X‐ray spectroscopy and Raman microscopy. A multilayer graphene oxide layer was closely coated onto the supporting substrate. The thickness of the coating was about 4 μm. Coupled with gas chromatography, the fiber was evaluated using five polycyclic aromatic hydrocarbons (fluorene, anthracene, fluoranthene, 1,2‐benzophenanthrene, and benzo(a)pyrene) as model analytes in direct‐immersion mode. The main conditions (extraction time, extraction temperature, ionic strength, and desorption time) were optimized by a factor‐by‐factor optimization. The as‐established method exhibited a wide linearity range (0.5–200 μg/L) and low limits of determination (0.05–0.10 μg/L). It was applied to analyze environmental water samples of rain and river water. Three kinds of the model analytes were quantified and the recoveries of samples spiked at 10 μg/L were in the range of 92.3–120 and 93.8–115%, respectively. The obtained results indicated the fiber was efficient for solid‐phase microextraction analysis. 相似文献
170.
Synthesis and Characterization of Aminoporphyrin‐End‐Functionalized Poly(N‐isopropylacrylamide) with Photodynamic and Thermoresponsive Effects 下载免费PDF全文
Yang Yang Yanhui Li Nannan Qiu Guihua Cui Prof. Toshifumi Satoh Prof. Qian Duan 《化学:亚洲杂志》2014,9(5):1379-1387
The novel aminoporphyrin‐end‐functionalized poly(N‐isopropylacrylamide) (PNIPAM) polymer H2N‐TPP‐PNIPAM (TPP=5,10,15,20‐tetraphenyl‐21H,23H‐porphyrin) behaves as a multifunctional platform that displays a photodynamic effect, thermosensitivity, and fluorescence properties. The polymer was designed by using an asymmetrical aminoporphyrin (i.e., H2N‐TPP‐Cl) as the initiator for the atom‐transfer radical polymerization of N‐isopropylacrylamide (NIPAM). The polydispersity index (PDI) obtained by gel‐permeation chromatography indicated that the molecular‐weight distribution was narrow (1.09<PDI<1.27). The lower critical solution temperatures of H2N‐TPP‐PNIPAM showed a decreasing trend as the molecular weight was increased as a result of the incorporation of the porphyrin group at the end of the chain. The fluorescence spectra revealed the luminescent properties of the materials. The results of confocal laser scanning microscopy showed that the polymer could enter the cytoplasm through endocytosis. In addition, the multifunctional platform exhibited low toxicity against normal cells (L929) and cancer cells (Hela) and enhanced photodynamic activity towards HeLa cells, without significant necrocytosis towards L929 cells; as a result this material may be useful in the future for practical photodynamic therapy. 相似文献