全文获取类型
收费全文 | 30962篇 |
免费 | 5035篇 |
国内免费 | 4350篇 |
专业分类
化学 | 16362篇 |
晶体学 | 380篇 |
力学 | 1299篇 |
综合类 | 296篇 |
数学 | 2446篇 |
物理学 | 7768篇 |
无线电 | 11796篇 |
出版年
2024年 | 109篇 |
2023年 | 598篇 |
2022年 | 950篇 |
2021年 | 1101篇 |
2020年 | 1059篇 |
2019年 | 1174篇 |
2018年 | 1027篇 |
2017年 | 1068篇 |
2016年 | 1332篇 |
2015年 | 1588篇 |
2014年 | 1836篇 |
2013年 | 2223篇 |
2012年 | 2641篇 |
2011年 | 2559篇 |
2010年 | 1976篇 |
2009年 | 2085篇 |
2008年 | 2234篇 |
2007年 | 2026篇 |
2006年 | 1853篇 |
2005年 | 1626篇 |
2004年 | 1433篇 |
2003年 | 1246篇 |
2002年 | 1439篇 |
2001年 | 1269篇 |
2000年 | 837篇 |
1999年 | 637篇 |
1998年 | 487篇 |
1997年 | 299篇 |
1996年 | 299篇 |
1995年 | 221篇 |
1994年 | 208篇 |
1993年 | 177篇 |
1992年 | 168篇 |
1991年 | 122篇 |
1990年 | 107篇 |
1989年 | 79篇 |
1988年 | 56篇 |
1987年 | 50篇 |
1986年 | 48篇 |
1985年 | 33篇 |
1984年 | 14篇 |
1983年 | 15篇 |
1982年 | 6篇 |
1981年 | 8篇 |
1980年 | 4篇 |
1979年 | 4篇 |
1971年 | 1篇 |
1959年 | 2篇 |
1957年 | 3篇 |
1936年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
991.
Herein we discovered that a Nile Red-based probe with a cinnamoyl unit was highly selective and sensitive to N2H4. Hydrazinolysis by N2H4 would release a hydroxyl substituted Nile Red and result in remarkable fluorescence quench. Importantly, Cys/Hcy would not interrupt the N2H4 recognition. This is because, for this probe, the combination of the π-π conjugate system can stabilize the ethylene union, which results in the nucleophilic addition of the thiol group of Cys/Hcy becomes non-effective. 相似文献
992.
993.
We observed a novel voltage peak in the proximity-induced superconducting gold (Au) nanowire while cooling the sample through the superconducting transition temperature. The voltage peak turned dip during warming. The voltage peak or dip was found to originate respectively from the emergence or vanishing of the proximity-induced superconductivity in the Au nanowire. The amplitude of the voltage signal depends on the temperature scanning rate, and it cannot be detected when the temperature is changed slower than 0.03 K/min. This transient feature suggests the non-equilibrium property of the effect. Ginzburg-Landau model clarified the voltage peak by considering the emergence of Cooper pairs of relatively lower free energy in superconducting W contact and the non-equilibrium diffusion of Cooper pairs and quasiparticles. 相似文献
994.
Gao Jian Ma Na Tian Jianjun Shen Cong Wang Lili Yu Pengfei Chu Yuanyuan Liu Wei Tan Xiaoyao Li Xifei Yin Zhen 《Journal of Solid State Electrochemistry》2018,22(2):519-525
Journal of Solid State Electrochemistry - One-pot strategy to fabricate N, P co-doping carbon was developed based on the functional ionic liquid (IL) as the N, P, and C precursors. The IL featuring... 相似文献
995.
996.
Liang‐Wei Zheng Gwo‐Long Li Mei‐Juan Chen Chia‐Hung Yeh Kuang‐Han Tai Jian‐Sheng Wu 《ETRI Journal》2013,35(3):469-479
This paper proposes an efficient computation‐aware mode decision and search point (SP) allocation algorithm for spatial and quality scalabilities in Scalable Video Coding. In our proposal, a linear model is derived to allocate the computation for macroblocks in enhancement layers by using the rate distortion costs of the base layer. In addition, an adaptive SP decision algorithm is proposed to decide the number of SPs for motion estimation under the constraint of the allocated computation. Experiment results demonstrate that the proposed algorithm allocates the computation resource efficiently and outperforms other works in rate distortion performance under the same computational availability constraint. 相似文献
997.
Huan-Lin Liu Xiang Xue Yong Chen Qiang Fang Sheng Huang 《Photonic Network Communications》2013,26(2-3):95-102
With the growth of multi-granularity multicast applications, there comes into being a huge gap between the bandwidth of a wavelength provided and a multicast traffic required in the wavelength division multiplexing (WDM) networks. The dynamic multicast traffic-grooming is an effective way for WDM networks to improve the wavelength utilization and decrease the traffic blocking probability. A novel switching node architecture with the multicast switching matrix and traffic-grooming fabric is studied in the paper. Then, an efficient dynamic multicast traffic-grooming algorithm is proposed for the architecture. According to the ratio of network available grooming port number to network transceiver number, the proposed algorithm estimates whether the traffic-grooming port is a scarce resource for input traffic and chooses the appropriate grooming strategy. If the traffic-grooming port is scarce, the minimized use grooming port strategy is designed for the coming traffic. On the contrary, the minimized use node transceiver strategy is applied for the coming traffic. Simulation results show that the proposed algorithm can groom traffic efficiently with low blocking probability and high network throughput constraint by limiting number of node transceivers and grooming ports. 相似文献
998.
Two new β-carboline-type alkaloids,dichotomine K(1) and dichotomine L(2),were isolated from the roots of Chinese medicinal plant Stellaria dichotoma L.var.lanceolata Bge.Structures of 1 and 2 were determined on the basis of chemical and spectroscopic means. 相似文献
999.
Controlled release formulation of pesticides is highly desirable for attaining the most effective utilization of the pesticide as well as reducing environmental pollution. Nano-sized controlled release formulations can provide better penetration through cuticle and deliver the active ingredients efficiently to the targeted tissue. In this study, a novel strategy for the preparation of a nanoconjugate derived from kasugamycin with amino-modified silica was developed. The kasugamycin was connected with amino-modified silica matrix by an amide bond, which could avoid the initial burst release effectively and prolong the duration remarkably. The results showed the kasuga-silica can protect kasugamycin against photo-degradation effectively and the release rate of the active ingredient of nanoconjugate was related to the temperature, pH value, and the particle size (52.5–315.4 nm). With reduced particle size as well as increased temperature and acidity, the release of the active ingredient was faster. This amide linkage of kasuga-silica could be degraded by amidase effectively. This nanoconjugate displayed a better and a sustained bactericidal efficacy against E. coli than kasugamycin technical, which makes it a potential candidate as a controlled release conjugate for kasugamycin in the future. 相似文献
1000.