全文获取类型
收费全文 | 86077篇 |
免费 | 6871篇 |
国内免费 | 5491篇 |
专业分类
化学 | 24040篇 |
晶体学 | 1807篇 |
力学 | 3819篇 |
综合类 | 423篇 |
数学 | 24401篇 |
物理学 | 43949篇 |
出版年
2023年 | 236篇 |
2022年 | 229篇 |
2021年 | 409篇 |
2020年 | 775篇 |
2019年 | 1091篇 |
2018年 | 1025篇 |
2017年 | 771篇 |
2016年 | 593篇 |
2015年 | 559篇 |
2014年 | 1358篇 |
2013年 | 2158篇 |
2012年 | 1384篇 |
2011年 | 2042篇 |
2010年 | 2602篇 |
2009年 | 7205篇 |
2008年 | 8348篇 |
2007年 | 6823篇 |
2006年 | 6193篇 |
2005年 | 4330篇 |
2004年 | 4046篇 |
2003年 | 4278篇 |
2002年 | 5437篇 |
2001年 | 3944篇 |
2000年 | 3677篇 |
1999年 | 3477篇 |
1998年 | 2890篇 |
1997年 | 2071篇 |
1996年 | 1828篇 |
1995年 | 2260篇 |
1994年 | 2188篇 |
1993年 | 1645篇 |
1992年 | 1148篇 |
1991年 | 879篇 |
1990年 | 705篇 |
1989年 | 629篇 |
1988年 | 595篇 |
1987年 | 420篇 |
1985年 | 980篇 |
1984年 | 643篇 |
1983年 | 506篇 |
1982年 | 662篇 |
1981年 | 822篇 |
1980年 | 738篇 |
1979年 | 584篇 |
1978年 | 605篇 |
1977年 | 555篇 |
1976年 | 554篇 |
1975年 | 319篇 |
1974年 | 360篇 |
1973年 | 468篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
21.
22.
A milestone in probability theory is the law of the iterated logarithm (LIL), proved by Khinchin and independently by Kolmogorov in the 1920s, which asserts that for iid random variables with mean 0 and variance 1 In this paper we prove that LIL holds for various functionals of random graphs and hypergraphs models. We first prove LIL for the number of copies of a fixed subgraph H. Two harder results concern the number of global objects: perfect matchings and Hamiltonian cycles. The main new ingredient in these results is a large deviation bound, which may be of independent interest. For random k‐uniform hypergraphs, we obtain the Central Limit Theorem and LIL for the number of Hamilton cycles. 相似文献
23.
Diabetes mellitus (DM) is the fastest growing metabolic disorder in the world. Recently, more attention is paid to the study of natural products due to side effects of synthetic drugs. Stevia rebaudiana (Bertoni) is considered an encouraging starting point for the antidiabetic lead development. In the present study, the in vitro α-amylase inhibitory activity of the extracts of S. rebaudiana is investigated. In order to understand the molecular mechanism and future pharmacophore development, in silico study of secondary metabolites isolated from S. rebaudiana was carried out. Results indicated that water extract shows highest α-amylase inhibitory activity as compared to other extracts. Moreover, compound 20 (rebaudioside A) which has been previously reported and isolated from water extract showed the impressive binding profile with α-amylase. Therefore, our study suggests that S. rebaudiana could be used in the development of therapeutic drugs for the treatment of diabetes. 相似文献
24.
The electrochemical behavior of austenitic stainless steel (Type 304) in 3 M sulfuric acid with 3.5% recrystallized sodium chloride at specific concentrations of butan-1-ol was investigated with the aid of potentiodynamic polarization, open circuit measurement and weight loss technique. Butan-1-ol effectively inhibited the steel corrosion with a maximum inhibition efficiency of 78.7% from weight-loss analysis and 80.9% from potentiodynamic polarization test at highest concentration studied. Adsorption of the compound obeyed the Freundlich isotherm. Thermodynamic calculations reveal physiochemical interactions and spontaneous adsorption mechanism. Surface characterizations showed the absence of corrosion products and topographic modifications of the steel. Statistical analysis depicts the overwhelming influence and statistical significance of inhibitor concentration on the inhibition performance. 相似文献
25.
26.
27.
28.
This work presents sufficient conditions for the existence of homoclinic solutions for second order coupled discontinuous systems of differential equations on the real line without the usual growth condition in the literature.The arguments apply the fixed point theory, Green's functions technique, -Carathéodory functions, lower and upper solutions and Schauder's fixed point theorem. 相似文献
29.
30.
在完备的度量空间中,讨论了一类新型的非线性压缩映射ρ(Tx,Ty)≤a(ρ(x,y))ρ(x,Tx)+b(ρ(x,y))ρ(y,Ty)+c(ρ(x,y))ρ(x,y)通过构造迭代序列,指出该映射的不动点的存在性和唯一性,并给出相应的误差估计式,拓展和改进了有关文献的范围. 相似文献