全文获取类型
收费全文 | 423篇 |
免费 | 6篇 |
专业分类
化学 | 258篇 |
晶体学 | 2篇 |
力学 | 10篇 |
数学 | 12篇 |
物理学 | 81篇 |
无线电 | 66篇 |
出版年
2024年 | 4篇 |
2023年 | 6篇 |
2022年 | 12篇 |
2021年 | 19篇 |
2020年 | 16篇 |
2019年 | 16篇 |
2018年 | 13篇 |
2017年 | 7篇 |
2016年 | 14篇 |
2015年 | 8篇 |
2014年 | 15篇 |
2013年 | 29篇 |
2012年 | 35篇 |
2011年 | 27篇 |
2010年 | 21篇 |
2009年 | 13篇 |
2008年 | 22篇 |
2007年 | 23篇 |
2006年 | 20篇 |
2005年 | 16篇 |
2004年 | 15篇 |
2003年 | 6篇 |
2002年 | 4篇 |
2001年 | 2篇 |
1997年 | 3篇 |
1996年 | 3篇 |
1995年 | 4篇 |
1994年 | 4篇 |
1993年 | 2篇 |
1992年 | 2篇 |
1990年 | 2篇 |
1989年 | 2篇 |
1988年 | 2篇 |
1987年 | 2篇 |
1985年 | 2篇 |
1984年 | 2篇 |
1983年 | 2篇 |
1981年 | 2篇 |
1979年 | 4篇 |
1978年 | 5篇 |
1977年 | 4篇 |
1976年 | 1篇 |
1975年 | 2篇 |
1974年 | 2篇 |
1973年 | 2篇 |
1972年 | 1篇 |
1967年 | 1篇 |
1948年 | 1篇 |
1943年 | 2篇 |
1941年 | 1篇 |
排序方式: 共有429条查询结果,搜索用时 15 毫秒
201.
202.
Prolinamides derived from l-proline and N,N-dialkyl 2-aminocamphor-10-sufonamides have been synthesized and used as organocatalysts in the direct intermolecular aldol reaction. Reactions of several aromatic aldehydes with cyclohexanone, cyclopentanone, 4-oxa and 4-sulfa-cyclohexanones and acetone are investigated employing 1a as an organocatalyst. Very high to excellent selectivities are obtained in these direct aldol reactions. 相似文献
203.
Bhim Bali Prasad Mahavir Prasad Tiwari Rashmi Madhuri Piyush Sindhu Sharma 《Analytica chimica acta》2010,662(1):14-661
A simple polymerization strategy is reported in this work which allows molecularly imprinted polymeric fiber (monolith) fabrication for direct use in sensing devices. This is advantageous for achieving higher degree of enrichment of target analyte (folic acid) from the complex matrices of real samples, without any surface fouling, cross-reactivity, and non-specific (false-positive) contributions. In order to measure serum folic acid at ultratrace level to detect spina bifida, a neural tube defect in mother, and other acute cases of proteomic diseases, the hyphenation between molecularly imprinted micro-solid phase extraction fiber and a complementary molecularly imprinted polymer-carbon composite fiber sensor has been found quite efficient. The primitive diagnosis of many chronic diseases is feasible by estimating folic acid as biomarker, with the detection limit as low as 0.0036 ng mL−1 (relative standard deviation = 0.13%, signal/noise = 3) in human blood serum. 相似文献
204.
This paper presents a solution for optimal business continuity, with storage architecture for enterprise applications, which will ensure zero data loss and quick recovery. The solution makes use of Internet protocol storage area network (IPSAN), which is used for data management without burdening the application server, as well as mix of synchronous and semi-synchronous replication techniques to replicate data to remote disaster recovery site. We have presented the detailed design of both synchronous and semi-synchronous with case study of using open source database postgres to prove our point for optimal business continuity. The theoretical presentation is also given for the same. 相似文献
205.
Efficient Implementations for AES Encryption and Decryption 总被引:1,自引:0,他引:1
Rashmi Ramesh Rachh P. V. Ananda Mohan B. S. Anami 《Circuits, Systems, and Signal Processing》2012,31(5):1765-1785
This paper proposes two efficient architectures for hardware implementation of the Advanced Encryption Standard (AES) algorithm. The composite field arithmetic for implementing SubBytes (S-box) and InvSubBytes (Inverse S-box) transformations investigated by several authors is used as the basis for deriving the proposed architectures. The first architecture for encryption is based on optimized S-box followed by bit-wise implementation of MixColumns and AddRoundKey and optimized Inverse S-box followed by bit-wise implementation of InvMixColumns and AddMixRoundKey for decryption. The proposed S-box and Inverse S-box used in this architecture are designed as a cascade of three blocks. In the second proposed architecture, the block III of the proposed S-box is combined with the MixColumns and AddRoundKey transformations forming an integrated unit for encryption. An integrated unit for decryption combining the block III of the proposed InvSubBytes with InvMixColumns and AddMixRoundKey is formed on similar lines. The delays of the proposed architectures for VLSI implementation are found to be the shortest compared to the state-of-the-art implementations of AES operating in non-feedback mode. Iterative and fully unrolled sub-pipelined designs including key schedule are implemented using FPGA and ASIC. The proposed designs are efficient in terms of Kgates/Giga-bits per second ratio compared with few recent state-of-the-art ASIC (0.18-μm CMOS standard cell) based designs and throughput per area (TPA) for FPGA implementations. 相似文献
206.
V Chandrasekhar S Das R Yadav S Hossain R Parihar G Subramaniam P Sen 《Inorganic chemistry》2012,51(16):8664-8666
A new water-soluble, multisite-coordinating ligand LH(7) was prepared by the condensation of tris(hydroxymethyl)aminomethane with 2,6-diformyl-p-cresol. LH(7) is a selective chemosensor for Cu(2+), under physiological conditions, with visual detection limits of 20 ppm (ambient light conditions) and 4 ppm (UV light conditions). LH(7) can also be used in biological cell lines for the detection of Cu(2+). 相似文献
207.
208.
Mukherjee P Roy M Mandal BP Choudhury S Tewari R Tyagi AK Kale SP 《Journal of colloid and interface science》2012,367(1):148-152
Green synthesis of gold nanospheres with uniform diameter and triangular nanoprisms with optically flat surface was carried out using a non-pathogenic bio-control agent Trichoderma asperellum for reduction of HAuCl(4). Kinetics of the reaction was monitored by UV-Vis absorption spectroscopy. No additional capping/complexing agent was used for stabilizing the gold nanoparticles. Evolution of morphology from pseudospherical nanoparticles to triangular nanoprisms was studied by transmission electron microscopy (TEM). It revealed that three or more pseudospheres fused to form nanoprisms of different shapes and sizes. Slow rate of reduction of HAuCl(4) by constituents of cell-free fungal extract was instrumental in producing such exotic morphologies. Isolation of gold nanotriangles from the reacting masses was achieved by differential centrifugation. 相似文献
209.
Direct transfer of micro-molded electrodes for enhanced mass transport and water management in PEMFC
Ashvini B. Deshmukh Vinayak S. Kale Vishal M. Dhavale K. Sreekumar K. Vijayamohanan Manjusha V. Shelke 《Electrochemistry communications》2010,12(11):1638-1641
Soft lithography technique is used to micropattern the electrodes on the electrolyte membrane of polymer electrolyte fuel cell (PEMFC) in order to alleviate the issues due to poor water management and inadequate reactant distribution in the fuel cell environment. Membrane electrode assembly with the micropatterned electrode has shown an increase in power density at a higher temperature as well as at a higher relative humidity when compared to a flat electrode. Consistency in cell performance is observed in the case of micropatterned electrodes. 相似文献
210.
The present work describes a new, simple, and easy method for the generation of stable molecularly imprinted sites in polymeric film, combining self-assembled monolayer and Layer-by-layer approaches through thermal cross-linking of the layered structures, onto the surface of silver electrode. Modified silver electrodes demonstrate enantiodifferentiation and sensitive (detection limits 0.0060 ng mL(-1) for L- and 0.0062 for D-thyroxine) determination of d- and l-thyroxine with the help of differential pulse anodic stripping voltammetric technique. The binding kinetics of thyroxine was explored using anodic stripping cyclic voltammetry and chronocoulometry. The sensor was also validated for D- and L-thyroxine determinations in biological and pharmaceutical samples. 相似文献