全文获取类型
收费全文 | 7223篇 |
免费 | 1133篇 |
国内免费 | 747篇 |
专业分类
化学 | 5340篇 |
晶体学 | 64篇 |
力学 | 342篇 |
综合类 | 15篇 |
数学 | 781篇 |
物理学 | 2561篇 |
出版年
2024年 | 14篇 |
2023年 | 190篇 |
2022年 | 216篇 |
2021年 | 281篇 |
2020年 | 353篇 |
2019年 | 333篇 |
2018年 | 277篇 |
2017年 | 256篇 |
2016年 | 389篇 |
2015年 | 381篇 |
2014年 | 435篇 |
2013年 | 514篇 |
2012年 | 674篇 |
2011年 | 707篇 |
2010年 | 443篇 |
2009年 | 440篇 |
2008年 | 446篇 |
2007年 | 420篇 |
2006年 | 358篇 |
2005年 | 318篇 |
2004年 | 217篇 |
2003年 | 207篇 |
2002年 | 167篇 |
2001年 | 127篇 |
2000年 | 102篇 |
1999年 | 123篇 |
1998年 | 104篇 |
1997年 | 94篇 |
1996年 | 95篇 |
1995年 | 80篇 |
1994年 | 64篇 |
1993年 | 53篇 |
1992年 | 58篇 |
1991年 | 40篇 |
1990年 | 29篇 |
1989年 | 31篇 |
1988年 | 18篇 |
1987年 | 12篇 |
1986年 | 8篇 |
1985年 | 11篇 |
1984年 | 5篇 |
1983年 | 3篇 |
1982年 | 6篇 |
1981年 | 2篇 |
1980年 | 1篇 |
1957年 | 1篇 |
排序方式: 共有9103条查询结果,搜索用时 62 毫秒
991.
1 实验:浮力方向总是竖直向上的 在初中物理浮力的教学中,浮力的方向总是竖直向上的,教材中没有专门的实验直观显示,学生虽能理解浮力的方向是向上的.但理解浮力方向总是竖直向上的就有一定困难. 相似文献
992.
崔文善,闫培生,张金政.木耳高产栽培配方的数学模型及优化研究.数理统计与管理,1997,16(4),8~11.本文采用回归正交设计方法,研究了泡桐木屑栽培木耳的配方组合与产量之间关系,并建立了数学模型。结果表明,以泡桐木屑为主料,各组分的适宜用量,以及它们之间合理组合,可显著提高木耳产量,降低生产成本,并具有较好的稳定性;其配方的优化方案为:泡桐木屑77.6~80.2%,麦夫12.5~14.8%,石灰2.4~2.7%,MgSO41.3%,KH2PO42.6%,糖1.0%。 相似文献
993.
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
994.
A new dual-frequency laser displacement measurement interferometer with nanometer precision has been developed. An eight-pass optical subdivision technology is proposed to improve resolution based on commercial interferometers. A static positioning error measuring method has been used to examine the precision and repeatability of the laser interferometer. An optical resolution of 1.24 nm and an accuracy of nanometer scale have been achieved. 相似文献
995.
By modulating the pump current, we developed a passively Q-switched diode-pumped all-solid-state laser with a repetition rate stabilized up to 10-7. It was experimentally demonstrated that the stability could sustain for an arbitrarily long time. Moreover, the stabilized repetition rates which were synchronized with different modulating frequencies were tuneable in a wide range, by adjusting the period of the pumping cycle only. The output single-pulse energy was also stabilized, which was independent on the pump power after reaching a saturable value. 相似文献
996.
In this paper, using the upper-lower solution method, we investigate the properties of periodic quasisolutions for time-periodic nonquasimonotone reaction-diffusion systems, and present some existence, asymptotic behavior results for two ecological models. 相似文献
997.
998.
弯曲振动对CS2分子1B2(1Σ)态预解离寿命的影响 总被引:1,自引:1,他引:0
在209.5~216nm,采用光解碎片激发(PHOFEX)谱技术,对CS2分子^1B2(^1∑u^+)态预解离寿命进行了考察.测量在超声射流中进行.信号来自解离碎片CS(A^1Ⅱ,υ’=0←X^1∑^+,υ”=0)Q支带头的激光诱导荧光(LIF).预解离寿命是通过对谱带进行拟合来提取的.拟合中假定基态转动布居为Boltzmann分布,寿命加宽的转动谱线为Lorentz线形.通过拟合共获得^1B2(^1∑u^+)态13个跃迁所对应的预解离寿命,其中6个数据是新得到的.结果表明,基态振动角动量量子数l或激发态转动角量子数K(K=l)对预解离寿命有明显的影响.对于激发态的同一振动能级,较大的K对应于较短的预解离寿命.实验中采用可加热的射流喷嘴,用以提高热带激发的强度,以改善对较大转动角量子数K的影响的考察. 相似文献
999.
Jun‐Feng Wu Dong‐Mei Li Li‐Feng Cui Chang‐Fu Zhuang Sai‐Nan Song Tie‐Gang Wang Ji‐Qing Xu Heng‐Qing Jia Ning‐Hai Hu 《应用有机金属化学》2007,21(12):1033-1040
Mo2O2S2(HGly)(Gly)2 1 and K6[Mo2O2S2(nta)2][Mo2O2S2(ntaH)2]·4H2O 2 were synthesized by the reactions of (NH4)2MoS4 and amino acids L (L = glycine, nitrilotriacetic acid) in ethanol–water medium at ambient temperature. The two complexes were characterized by elemental analysis, infrared spectra, UV–visible spectra, TG–DTA and XPS. X‐ray crystallographic structural analyses revealed that compound 1 is a binuclear Mo? S? glycinate complex, a glycinate ligand is coordinated to each molybdenum atom through its amine nitrogen and carboxylato oxygen, respectively, and the third glycinate acts as a bridge through its two carboxylato oxygens linking the two molybdenum atoms. Compound 2 is also a binuclear Mo? S complex with two nitrilotriacetate ligands, each of which is coordinated to a molybdenum atom via its two β‐carboxylato oxygens and a nitrogen atom. Simultaneously, each molybdenum atom in 1 and 2 is chelated to a terminal oxygen and two bridging sulfurs to complete the octahedral configuration. Their catalytic activities in the reduction from C2H2 to C2H4 as well as other binuclear Mo? S? polycarboxylate complexes, a [Fe4S4] single cubane and a chainlike Mo? Fe? S compound were investigated and it was found that 1 exhibited relatively good catalytic activity. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
1000.
自Bridgeman发明套筒活塞高压装置以来,特别是引入金刚石压砧后,高压物理学发展迅速。这种金刚石对顶砧压力盒,简称为DAC,为研究高压下材料的光学性质提供了极大的方便。为进行高压低温研究,目前国内都是将压机浸入液氮中,或向DAC喷浇液氮。这样只能在77K恒温,且必须取出压机后才能加压。 相似文献