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211.
Evolution of Chinese airport network 总被引:2,自引:0,他引:2
With the rapid development of the economy and the accelerated globalization process, the aviation industry plays a more and more critical role in today’s world, in both developed and developing countries. As the infrastructure of aviation industry, the airport network is one of the most important indicators of economic growth. In this paper, we investigate the evolution of the Chinese airport network (CAN) via complex network theory. It is found that although the topology of CAN has remained steady during the past few years, there are many dynamic switchings inside the network, which have changed the relative importance of airports and airlines. Moreover, we investigate the evolution of traffic flow (passengers and cargoes) on CAN. It is found that the traffic continues to grow in an exponential form and has evident seasonal fluctuations. We also found that cargo traffic and passenger traffic are positively related but the correlations are quite different for different kinds of cities. 相似文献
212.
建立灵敏、可靠的中药材中农药多残留的检测方法对保证中药材的质量和安全十分重要.制备了磁性亲水亲脂平衡萃取材料Fe3 O4@PLS,将其应用于农药多残留的磁性基质固相分散萃取中,并结合高效液相色谱-串联质谱法(HPLC-MS/MS)检测了金银花、菊花和三七块根(干)3种中药材中76种农药残留量.研究通过扫描电子显微镜(S... 相似文献
213.
Abstract Infrared spectroscopy has been a workhorse technique for materials analysis and can result in positively identifying many different types of material. In recent years there have been reports using wavelet analysis and machine learning algorithms to extract features of Fourier transform infrared spectrometry (FTIR). The machine learning algorithms contain back-propagation neural network (BPNN), radial basis function neural network (RBFNN), and support vector machine (SVM). This article reviews the important advances in FTIR analysis employing a continuous wavelet transform (CWT) and machine learning algorithms, especially in the applications of the method for Chinese medicine identification, plant classification, and cancer diagnosis. 相似文献
214.
Let , be independent and identically distributed random variables with values in . We transform (‘prune’) the sequence , of discrete random samples into a sequence , of contiguous random sets by replacing with if . We consider the asymptotic behaviour of as . Applications include path growth in digital search trees and the number of tables in Pitmanʼs Chinese restaurant process if the latter is conditioned on its limit value. 相似文献
215.
Some forecasting models have been developed, each has its own application condition. The grey model is used for small sample forecasting, but until now there is no reasonable explanation for the reason why it is not used for large sample. Therefore, in this paper, matrix perturbation theory is employed to explain the reason. The results of practical numerical examples from previous works demonstrate that the small sample usually has more accuracy than the large sample when establishing grey model in theory. Furthermore, we used the grey model with small samples to analyse the trend of syphilis incidence in China. 相似文献
216.
Yang Bai Xiang Yao Jiandong Wang Jin-Long Wang Si-Cheng Wu Shi-Ping Yang Wei-Shi Li 《Tetrahedron》2019,75(33):4676-4685
Fullerene-based organic solar cells are generally suffering from severe microstructure evolution occurring in their bulk heterojunction active layers and thus are extremely stable. To address it, four polymerizable C70 fullerene derivatives, [6,6]-phenyl-C71-ethyl acrylate (PC71EA), [6,6]-phenyl-C71-propyl acrylate (PC71PrA), [6,6]-phenyl-C71-butyl acrylate (PC71BA), and [6,6]-phenyl-C71-pentyl acrylate (PC71PeA), have been designed, synthesized, and investigated. These fullerene compounds have a molecular structure, shape and size very like the conventional C70 fullerene acceptor, [6,6]-phenyl-C71-butyric acid methyl ester (PC71BM), and have been found no different in their light absorption, redox potentials, and frontier orbital energy levels. Using these fullerene acrylates individually as acceptor and poly(3-hexylthiophene) as donor, organic solar cells have been fabricated and gave optimal efficiencies ranging from 3.32% to 4.16%, comparable to PC71BM-based reference cells (4.06%). Owing to their acrylate functionality, these fullerene derivatives can turn into insoluble upon heating, and thus endow their solar cell devices much better thermostability than PC71BM-based reference cells. The best one, coming from PC71PeA devices, reported an optimal efficiency of 4.16%, and maintained 91.7% efficiency after heat treatment at 150 °C for 35 h. As a sharp contrast, the PC71BM reference cell dropped its optimal efficiency from 4.06% to 0.48% only after 5 h heat treatment. X-ray diffraction, optical and atomic force microscopy, and space-charge-limited current method have been carried out to understand active layer structure, morphology, and charge mobility change during heat treatment. 相似文献
217.
Bing-Jie Zhang Wen-Na Xiao Jing Chen Mei-Fen Bao Johann Schinnerl Qi Wang Xiang-Hai Cai 《Tetrahedron》2019,75(38):130515
Continued interest in Erythrina alkaloids resulted in the isolation of 38 alkaloids including 7 undescribed ones from the leaves of Erythrina arborescens Roxburgh. Among the new compounds, erythrivarines H-I were two dimeric alkaloids, while others were Erythrina alkaloid glucosides. Dimeric Erythrina alkaloids and monomers, turcomanidine and isoboldine, showed medium xanthine oxidase inhibition. 相似文献
218.
Tao Li Ping-Lin Li Xiang-Chao Luo Xu-Li Tang Guo-Qiang Li 《Tetrahedron letters》2019,60(30):1996-1998
Three new dibromopyrrole alkaloids, 9-N-methylcylindradine A (1), 1-N-methylugibohlin (2), nemoechine H (3), together with one known dibromopyrrole alkaloid N-methyldibromoisophakellin (4) were isolated from the South China Sea sponge Agelas nemoechinata. Their structures were elucidated by comprehensive spectroscopic methods including HRESIMS and NMR, and the absolute configuration of compound 1 was further confirmed by comparison of optical rotation. Compound 3 exhibited moderate cytotoxic activity against K562 and L-02 with IC50 values of 6.1 μM and 12.3 μM, respectively. 相似文献
219.
220.
Zong Chang Feng Liu Liang Wang Mengying Deng Chunhua Zhou Qinchao Sun Jun Chu 《中国化学快报》2019,30(10):1856-1882
Taking the advantage of reduced scattering and low autofluorescence background, the NIR fluorescence probes, such as fluorescence proteins, organic molecules and nanoparticles, not only hold the promise of in vivo imaging of biological processes in physiology and pathology with high signal-to-noise ratio, but also for clinical diagnosis. In this review, we provide an overview of the recent progress on NIR probes, focusing on fundamental mechanisms of NIR dyes and nanoparticles, and protein engineering strategies for NIR proteins. 相似文献