全文获取类型
收费全文 | 6121篇 |
免费 | 1021篇 |
国内免费 | 1265篇 |
专业分类
化学 | 5273篇 |
晶体学 | 76篇 |
力学 | 272篇 |
综合类 | 120篇 |
数学 | 743篇 |
物理学 | 1923篇 |
出版年
2024年 | 10篇 |
2023年 | 67篇 |
2022年 | 124篇 |
2021年 | 131篇 |
2020年 | 180篇 |
2019年 | 267篇 |
2018年 | 182篇 |
2017年 | 187篇 |
2016年 | 277篇 |
2015年 | 295篇 |
2014年 | 319篇 |
2013年 | 440篇 |
2012年 | 486篇 |
2011年 | 462篇 |
2010年 | 459篇 |
2009年 | 369篇 |
2008年 | 475篇 |
2007年 | 410篇 |
2006年 | 386篇 |
2005年 | 368篇 |
2004年 | 330篇 |
2003年 | 359篇 |
2002年 | 497篇 |
2001年 | 453篇 |
2000年 | 282篇 |
1999年 | 179篇 |
1998年 | 102篇 |
1997年 | 54篇 |
1996年 | 52篇 |
1995年 | 33篇 |
1994年 | 24篇 |
1993年 | 14篇 |
1992年 | 22篇 |
1991年 | 33篇 |
1990年 | 18篇 |
1989年 | 9篇 |
1988年 | 15篇 |
1987年 | 6篇 |
1986年 | 6篇 |
1985年 | 7篇 |
1984年 | 7篇 |
1983年 | 5篇 |
1982年 | 2篇 |
1981年 | 1篇 |
1975年 | 1篇 |
1936年 | 2篇 |
排序方式: 共有8407条查询结果,搜索用时 31 毫秒
51.
A Novel and Efficient Catalytic System for Aerobic Oxidative Coupling of 2-Naphthol Derivatives 总被引:2,自引:0,他引:2
LiCHEN JingBoLAN ZhiHuaMAO XiaoQiYU RuGangXIE 《中国化学快报》2004,15(8):903-906
The paper reported a novel and efficient aerobic oxidative coupling reaction of 2-naphthol derivatives catalyzed by CuCu (Ⅰ or Ⅱ)N-alkylimidazole complexes in excellent yields. The crystal structure of CuCu(Ⅱ)N-methylimidazole complex to be determined by X-Ray. 相似文献
52.
Zhi‐Yong Huang Jin‐Can Shen Zhi‐Xia Zhuang Xiao‐Ru Wang Frank S. C. Lee 《应用有机金属化学》2004,18(6):255-261
Cinnabar, as one of the most widely used mineral drugs in traditional Chinese medicines, has been proven to have prominent curative effects in clinical use for more than 2000 years. But the safety and toxicity of the drug has been under constant debate in clinic usage. Metallothionein (MT) contains about 30% of cysteine in the molecule, and plays an important detoxification role against heavy metals. In this study, it was used as a biomarker to assess mercurial accumulation in rats fed orally with cinnabar. After feeding rats with cinnabar by gastric gavage at different dosages and at different times, the distribution of heavy metals (including mercury, copper and zinc) and MT was investigated among rat tissues, including liver, kidney, heart, brain, testis and blood. Metals and MT determinations were carried out using inductively coupled plasma mass spectrometry (ICP‐MS) and a modified mercury saturation assay technique respectively. The results indicated that mercury was easily accumulated in the tissues of rats exposed to cinnabar, especially in kidney. For example: at a feeding dosage of 5 g kg?1 (bw) for 4 weeks, the mercury concentrations in kidney were 13, 8.7, 21.6 and 26 times those in liver, testis, brain and heart respectively; and at 2.5 g kg?1 (bw) for 2 weeks, the mercury concentrations in kidney were 21, 2.1, 3 and 21 times those in liver, testis, brain and heart respectively. In addition, mercury in kidney and liver of all cinnabar groups was significantly higher than that of the control group (P < 0.01). A high positive correlation observed between MT concentrations and mercury levels in both liver and kidney (R2 = 0.9299, P < 0.02 for liver; R2 = 0.9923, P < 0.0008 for kidney) indicated that MT could be used as a biomarker for mercury in tissues. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
53.
The terminology ‘ID frequency’(w ID) is proposed after analyzing the 1D active photonic crystal based on the transfer matrix method. The relationship between wID and the structure parameters of the photonic crystal is investigated. 相似文献
54.
两个电磁学演示实验的再设计 总被引:1,自引:0,他引:1
利用简易装置对高中教材中的退磁和自感演示实验进行了再设计,介绍了演示方法,并对实验现象给出了解释。 相似文献
55.
无界区域R1上推广的B-BBM方程的整体吸引子 总被引:4,自引:0,他引:4
本文研究了无界区域R^1上推广的B—BBM方程的长时间动力学行为,证明了该方程整体吸引子的存在性. 相似文献
56.
CunLiuZHOU YuQingZHOU ZhiYongWANG 《中国化学快报》2003,14(4):355-358
The chemoselective addition of aldehydes in aquoues medium was obtained under mild condition using improved Henry reaction. 相似文献
57.
利用2~8 MeV的Naq+、Clq+(q=2,3,4,5)轰击氦原子,对碰撞的直接多重电离过程进行研究.实验采用反冲离子-散射离子飞行时间符合技术,通过反冲离子飞行时间谱区分不同价态反冲离子;利用静电偏转和位置灵敏探测技术区分不同电荷态散射离子;结合CAMAC-PC多参数获取系统得到一定价态散射离子所对应的反冲离子电荷态分布谱;经分析该谱得到直接多重电离截面与直接单电离截面之比R21.讨论了R21随入射离子速度和电荷态的变化关系. 相似文献
58.
59.
60.
Frame Wavelets with Compact Supports for L^2(R^n) 总被引:1,自引:0,他引:1
De Yun YANG King Wei ZHOU Zhu Zhi YUAN 《数学学报(英文版)》2007,23(2):349-356
The construction of frame wavelets with compact supports is a meaningful problem in wavelet analysis. In particular, it is a hard work to construct the frame wavelets with explicit analytic forms. For a given n × n real expansive matrix A, the frame-sets with respect to A are a family of sets in R^n. Based on the frame-sets, a class of high-dimensional frame wavelets with analytic forms are constructed, which can be non-bandlimited, or even compactly supported. As an application, the construction is illustrated by several examples, in which some new frame wavelets with compact supports are constructed. Moreover, since the main result of this paper is about general dilation matrices, in the examples we present a family of frame wavelets associated with some non-integer dilation matrices that is meaningful in computational geometry. 相似文献