全文获取类型
收费全文 | 38040篇 |
免费 | 5547篇 |
国内免费 | 3780篇 |
专业分类
化学 | 26327篇 |
晶体学 | 369篇 |
力学 | 2312篇 |
综合类 | 250篇 |
数学 | 4369篇 |
物理学 | 13740篇 |
出版年
2024年 | 113篇 |
2023年 | 773篇 |
2022年 | 1257篇 |
2021年 | 1396篇 |
2020年 | 1473篇 |
2019年 | 1354篇 |
2018年 | 1181篇 |
2017年 | 1085篇 |
2016年 | 1649篇 |
2015年 | 1673篇 |
2014年 | 2040篇 |
2013年 | 2640篇 |
2012年 | 3305篇 |
2011年 | 3273篇 |
2010年 | 2212篇 |
2009年 | 2093篇 |
2008年 | 2254篇 |
2007年 | 1999篇 |
2006年 | 1885篇 |
2005年 | 1569篇 |
2004年 | 1328篇 |
2003年 | 1003篇 |
2002年 | 912篇 |
2001年 | 754篇 |
2000年 | 707篇 |
1999年 | 851篇 |
1998年 | 731篇 |
1997年 | 649篇 |
1996年 | 716篇 |
1995年 | 613篇 |
1994年 | 565篇 |
1993年 | 484篇 |
1992年 | 466篇 |
1991年 | 371篇 |
1990年 | 331篇 |
1989年 | 240篇 |
1988年 | 217篇 |
1987年 | 203篇 |
1986年 | 143篇 |
1985年 | 158篇 |
1984年 | 135篇 |
1983年 | 119篇 |
1982年 | 80篇 |
1981年 | 60篇 |
1980年 | 49篇 |
1979年 | 33篇 |
1978年 | 26篇 |
1976年 | 27篇 |
1975年 | 31篇 |
1974年 | 23篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
141.
A simple and sensitive method was conducted for the determination of trace amounts of proteins with benzeneazo-8-acetylamino-1-naphthol-3,6-disulfonic acid sodium salt (azophloxine, AP) using a Rayleigh light-scattering (RLS) technique. At pH 2.60 and in the presence of an emulsifier OP microemulsion, the RLS of AP can be greatly enhanced by proteins, owing to the interaction between AP and protein. The enhanced intensity is proportional to the concentration of proteins. Four proteins, including bovine serum albumin (BSA), human serum albumin (HSA), lysozyme (Lys) and gamma globulin (gamma-G) have been tested. For example, the linear range of BSA was 0 - 0.06 microg mL(-1) with detection limits of 2.38 ng mL(-1). The method was applied to the analysis of protein in human urine and penicillin samples with satisfactory results. The relative standard deviation was in all instances less than 4.0%, and the recovery was in the range of 97.5 - 104%. 相似文献
142.
In the present work, ferrites with compositions of (Ni0.27Zn0.64Cux)Fe1.98O4 (x=0.1, 0.2) were prepared by conventional ceramic methods. The relationship between the microstructure and the temperature dependence of relative initial permeability was investigated. It was found that intergranular pores in the ferrites generate large demagnetizing fields, reducing the temperature dependence of the effective anisotropy field Heff, and decreasing the temperature dependence of the relative initial permeability accordingly. However, intragranular pores pin the movement of domain walls. Compared with the permeability induced by domain wall motion, the permeability that resulted from the spin rotation is more sensitive to temperature. As a result, the relative initial permeability of ferrites becomes more sensitive to temperature with increasing micropores within grains. 相似文献
143.
In the discrete-time Sparre Andersen risk model with investments and dividend payments, the company controls the dividend payments and the proportions of venture investments in order to maximize the cumulative expected discounted dividends prior to ruin. The paper gets the algorithm of the optimal dividend strategy by analyzing a Hamilton-Jacobi-Bellman equation and transforming the value function. Furthermore, the existence of the optimal solution of the transformation function is proved by using compression mapping and fixed point principle. In order to make the calculation easier, this paper also proposes an
innovative random simulation method for the optimal strategy, and proves that the simulation result is the consistent estimate of the real value. Finally, the random simulation method in the Matlab is used for numerical analysis in an example, which shows the innovative simulation method is a very good and helpful method for making dividend payment and investment decisions. 相似文献
144.
145.
从实验上探讨了掺Nd^3+的氟化物玻璃光纤正向双程超荧光基本特性,包括输入-输出特性、输出-带宽特性以及输出-波长(激发)特性。并给出了理论上的拟合公式,实验表明利用氟化物玻璃光纤有望获得性能优异的有应用前景的低相干度集成化光源。 相似文献
146.
负关联噪声驱动下单模激光的定态分析 总被引:2,自引:1,他引:1
研究了负关联的加法和乘法高斯白噪声驱动下单模激光损失模型的定态情况。文中推导了负关联情况下,定态时的激光场幅的几率分布,光强的平均值,光强的协方差以及光强的偏斜率。并和文献〔1,2〕中正关联时的定态分析作了比较,发现了有意义的新现象。 相似文献
147.
148.
149.
150.