全文获取类型
收费全文 | 18957篇 |
免费 | 3363篇 |
国内免费 | 2218篇 |
专业分类
化学 | 13670篇 |
晶体学 | 187篇 |
力学 | 1093篇 |
综合类 | 127篇 |
数学 | 1935篇 |
物理学 | 7526篇 |
出版年
2024年 | 78篇 |
2023年 | 431篇 |
2022年 | 686篇 |
2021年 | 736篇 |
2020年 | 780篇 |
2019年 | 784篇 |
2018年 | 700篇 |
2017年 | 620篇 |
2016年 | 955篇 |
2015年 | 937篇 |
2014年 | 1100篇 |
2013年 | 1380篇 |
2012年 | 1698篇 |
2011年 | 1592篇 |
2010年 | 1130篇 |
2009年 | 1048篇 |
2008年 | 1164篇 |
2007年 | 1086篇 |
2006年 | 996篇 |
2005年 | 895篇 |
2004年 | 647篇 |
2003年 | 543篇 |
2002年 | 532篇 |
2001年 | 414篇 |
2000年 | 375篇 |
1999年 | 447篇 |
1998年 | 379篇 |
1997年 | 353篇 |
1996年 | 338篇 |
1995年 | 283篇 |
1994年 | 239篇 |
1993年 | 203篇 |
1992年 | 165篇 |
1991年 | 141篇 |
1990年 | 160篇 |
1989年 | 116篇 |
1988年 | 79篇 |
1987年 | 55篇 |
1986年 | 66篇 |
1985年 | 60篇 |
1984年 | 31篇 |
1983年 | 30篇 |
1982年 | 30篇 |
1981年 | 19篇 |
1980年 | 10篇 |
1979年 | 3篇 |
1977年 | 3篇 |
1942年 | 2篇 |
1930年 | 2篇 |
1916年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
Qiu Hong WU He Xiang WANG Kun GAO State Key Laboratory of Applied Organic Chemistry College of Chemistry Chemical Engineering Lanzhou University Lanzhou 《中国化学快报》2006,17(2)
Many Ligularia species have long been used as traditional folk medicine for theirantibiotic, antiphlogistic and antitussive activities1, and were found to be an importantsource of eremophilane. In the course of our search for bioactive sesquiterpenoids, w… 相似文献
62.
Let X be a metric space, B the σ-algebra of Borel subsets of X, and μ a probability measure on (X,B). In this note, for a measure-preserving map T (respectively a measure-preserving semi-flow φ) on (X,B,μ), we prove that if suppμ=X, and T (respectively φ) is weak-mixing, then T (respectively φ) has sensitive dependence. 相似文献
63.
Bing-sheng He Zhen-hua Yang Xiao-ming Yuan 《Journal of Mathematical Analysis and Applications》2004,300(2):139-374
Proximal point algorithms (PPA) are attractive methods for monotone variational inequalities. The approximate versions of PPA are more applicable in practice. A modified approximate proximal point algorithm (APPA) presented by Solodov and Svaiter [Math. Programming, Ser. B 88 (2000) 371–389] relaxes the inexactness criterion significantly. This paper presents an extended version of Solodov–Svaiter's APPA. Building the direction from current iterate to the new iterate obtained by Solodov–Svaiter's APPA, the proposed method improves the profit at each iteration by choosing the optimal step length along this direction. In addition, the inexactness restriction is relaxed further. Numerical example indicates the improvement of the proposed method. 相似文献
64.
Zhimin He 《Journal of Mathematical Analysis and Applications》2004,296(1):97-109
In this paper, by means of a new twin fixed-point theorem in a cone, the existence of at least two positive solutions of m-point boundary value problem for second order dynamic equations on time scales is considered. 相似文献
65.
66.
67.
Qingfa Wang Li Wang Yaquan Wang Fei He Zhenhua Li Zhentao Mi 《Reaction Kinetics and Catalysis Letters》2004,81(2):297-304
Deactivated palladium catalysts in the hydrogenation of anthraquinione were regenerated with ethanol, nitric acid, hydrogen
peroxide, boiling water and steam, respectively. The deactivated and regenerated catalysts were characterized by XPS, ICP,
TG, FTIR, TPD, XRD, etc., and studied in the hydrogenation of anthraquinone. The results showed that the main cause of catalyst deactivation is the
coverage of the active component by deposits. The treatments by hydrogen peroxide and boiling water can effectively regenerate
the deactivated catalysts.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
68.
Shui Cao ZHENG Huo Nan LIN Di He HU 《数学学报(英文版)》2005,21(5):1137-1148
In this paper, we investigate the Hausdorff measure for level sets of N-parameter Rd-valued stable processes, and develop a means of seeking the exact Hausdorff measure function for level sets of N-parameter Rd-valued stable processes. We show that the exact Hausdorff measure function of level sets of N-parameter Rd-valued symmetric stable processes of index α is Ф(r) = r^N-d/α (log log l/r)d/α when Nα 〉 d. In addition, we obtain a sharp lower bound for the Hausdorff measure of level sets of general (N, d, α) strictly stable processes. 相似文献
69.
70.
高斯光束计算平板波导自由传输区远场分布及其修正 总被引:2,自引:2,他引:0
对近轴近似条件下求解亥姆霍兹方程得到的高斯光束显式传播公式做了分析,同时,基于基尔霍夫衍射理论,在菲涅耳近似的条件下给出了相应的高斯光束在远场的传播公式,在此基础上,对近轴近似条件做出了定量分析,给出了这个近似条件引入的误差,提出了一种计算高斯光束远场分布的修正方法,并采用有限差分-光束传播方法(FD-BPM)来检验各种方法的准确性。把这种修正方法应用到平面光集成波导器件,如阵列波导光栅(AWG)、蚀刻衍射光栅(EDG)等器件的设计和模拟中,可以大大降低工作的复杂性,同时可以得到精确的结果。 相似文献