全文获取类型
收费全文 | 8625篇 |
免费 | 1195篇 |
国内免费 | 846篇 |
专业分类
化学 | 4933篇 |
晶体学 | 64篇 |
力学 | 329篇 |
综合类 | 18篇 |
数学 | 723篇 |
物理学 | 2371篇 |
无线电 | 2228篇 |
出版年
2024年 | 39篇 |
2023年 | 267篇 |
2022年 | 322篇 |
2021年 | 379篇 |
2020年 | 386篇 |
2019年 | 348篇 |
2018年 | 288篇 |
2017年 | 290篇 |
2016年 | 407篇 |
2015年 | 427篇 |
2014年 | 486篇 |
2013年 | 593篇 |
2012年 | 726篇 |
2011年 | 765篇 |
2010年 | 529篇 |
2009年 | 537篇 |
2008年 | 530篇 |
2007年 | 482篇 |
2006年 | 462篇 |
2005年 | 412篇 |
2004年 | 246篇 |
2003年 | 236篇 |
2002年 | 208篇 |
2001年 | 154篇 |
2000年 | 143篇 |
1999年 | 172篇 |
1998年 | 127篇 |
1997年 | 110篇 |
1996年 | 106篇 |
1995年 | 93篇 |
1994年 | 78篇 |
1993年 | 61篇 |
1992年 | 74篇 |
1991年 | 46篇 |
1990年 | 33篇 |
1989年 | 31篇 |
1988年 | 21篇 |
1987年 | 12篇 |
1986年 | 8篇 |
1985年 | 11篇 |
1984年 | 7篇 |
1983年 | 4篇 |
1982年 | 6篇 |
1981年 | 2篇 |
1980年 | 1篇 |
1957年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 10 毫秒
91.
Ruohu Zhang Zhuyuan Wang Chunyuan Song Jing Yang Yiping Cui 《Journal of fluorescence》2013,23(3):551-559
A straightforward immunoassay based on surface enhanced fluorescence (SEF) has been demonstrated using a fluorescent immune substrate and antibody functionalized-silver nanoparticles. Unlike the conventional SEF-based immunoassay, which usually uses the dye-labeled antibodies and the metallic nanostructured-substrates, the presented immune system does not need the antibodies to be labeled with dye molecules. Thus, this immunoassay can be easily applied to the detection of a wide range of target antigens, which is of great importance for its practical application. The experimental results show that this immunoassay has a good specificity as well as the capacity of quantitative detection. Basically, the surface density of the immuno-adsorbed silver nanoparticles increases with the increased amount of target antigens, resulting in a fluorescence enhancement up to around 7 fold. The dose-responsive performance of the immunoassay has been investigated and the limit of detection (LOD) is 1 ng/mL. Due to its simple preparation method and the wide range of detectable antigens, this presented immunoassay is expected to be helpful for extending the SEF-based application. 相似文献
92.
The multivariate extension of the Cox model proposed by Wei,Lin and Weissfeld in 1989 has been widely used for analyzing multivariate survival data.Under the model assumption,failure times from an individual are assumed to marginally follow their respective proportional hazards regression relation,leaving the joint distribution completely unspecified.This paper presents a simple approach to efficiency improvement through segmentation of stochastic integrals in the marginal estimating equations and incorporation of the limiting covariance structure.It is shown that when partition of the time interval is done at a suitable rate,the resulting estimator is consistent and asymptotically normal.Through the reproducing kernel Hilbert space arising from the covariance function of the limiting Gaussian process,it is also shown that the proposed estimator is asymptotically optimal within a reasonable class of estimators under marginal specification.Simulations are conducted to assess the finite-sample performance of the proposed method. 相似文献
93.
94.
95.
Y. J. Li D. Y. Dong S. L. Wang Z. P. Wu C. Cui P. G. Li L. H. Li J. H. Xiao W. H. Tang 《Applied Physics A: Materials Science & Processing》2014,115(3):791-795
La0.67Ca0.33MnO3 particle films with an average particle size of ~150 nm were grown on single-crystal silicon substrate using pulsed electron deposition technique and then focused ion beam was introduced to fabricate nanobridge in size of 300 × 900 nm on the particle film. The magneto-transport properties of both samples were studied. For the film, there is only one resistance peak at 182 K in temperature-dependent resistance (R–T) curves, which is far lower than ferromagnetic–paramagnetic transition temperature (T C) of 250 K. When compared to the film, double peaks were observed in both R–T curves and magnetoresistance dependent on temperature (MR–T) curves of the nanobridge, one peak is at 186 K, which is very close to metal–insulator transition temperature (T P) of film, the other one is at 250 K, which is close to the T C of film, and these two peaks caused separately by grain and grain boundary (GB), which demonstrated that the electrical transport behavior of grain was separated from that of GB. 相似文献
96.
97.
利用半导体激光泵浦输出1064 nm波长的全固态连续Nd:YVO4激光器作为泵浦源,采用周期调谐和温度调谐组合调谐技术,对基于掺氧化镁周期性极化铌酸锂晶体(MgO:LiNbO3, PPMgLN)准相位匹配(QPM)的全固态连续波(CW)光学参量振荡器(OPO)宽波段无分立连续调谐输出特性进行研究。实验采用连续工作模式和外腔结构,基于多周期PPMgLN晶体的30.2,30.4和30.6 m周期,在改变晶体的极化周期的基础上,同时在30~100 ℃范围内调节晶体工作温度。实验结果表明:CW PPMgLN OPO的泵浦阈值仅为0.22 W;不同极化周期需要的温度调谐范围不同;信号光在1 559.8~1 597.2 nm近红外波段和闲频光在3 187.3~3 347.3 nm中红外波段连续调谐输出。实现了外腔式全固态CW OPO在信号光和闲频光波段的无分立连续调谐输出。 相似文献
98.
Criteria for strict monotonicity, lower local uniform monotonicity, upper local uniform monotonicity, and uniform monotonicity of Musielak-Orlicz spaces over any σ-finite and complete measure space, endowed with the Amemiya norm are given. The fact that the spaces are considered over arbitrary σ-finite measure space is essential because, as it is shown in Example 3, the Musielak-Orlicz spaces need not be strictly monotone even if their restrictions to the nonatomic part and the purely atomic part are strictly monotone. 相似文献
99.
Haibo Cui Haiyan Yin Jinshun Zhang Changjiang Zhu 《Journal of Differential Equations》2018,264(7):4564-4602
In this paper, we are concerned with the asymptotic behavior of solutions to the system of Euler equations with time-depending damping, in particular, include the constant coefficient damping. We rigorously prove that the solutions time-asymptotically converge to the diffusion wave whose profile is self-similar solution to the corresponding parabolic equation, which justifies Darcy's law. Compared with previous results about Euler equations with constant coefficient damping obtained by Hsiao and Liu (1992) [2], and Nishihara (1996) [9], we obtain a general result when the initial perturbation belongs to the same space, i.e. . Our proof is based on the classical energy method. 相似文献
100.
惯性约束聚变频率转换系统中,大口径薄型KDP晶体的面形质量是影响频率转换效率能否达到设计要求的关键因素之一。针对45放置状态下口径为400 mm400 mm的三倍频KDP晶体,采用ANSYS有限元分析软件,建立了不同夹持方式和具有不同加工误差的KDP晶体模型和夹具模型,分析了加工误差对不同夹持方式下KDP晶体附加面形的影响,给出了不同加工误差和不同夹持情况下,KDP晶体附加面形的P-V值和RMS值。研究结果表明,夹持方式和加工误差是引起KDP晶体附加面形变化的重要因素,正面压条夹持方式即使在晶体和夹具存在加工误差时也可以较好地控制晶体的附加面形。 相似文献