全文获取类型
收费全文 | 637篇 |
免费 | 58篇 |
国内免费 | 57篇 |
专业分类
化学 | 472篇 |
晶体学 | 4篇 |
力学 | 30篇 |
综合类 | 1篇 |
数学 | 36篇 |
物理学 | 209篇 |
出版年
2023年 | 11篇 |
2022年 | 27篇 |
2021年 | 18篇 |
2020年 | 18篇 |
2019年 | 20篇 |
2018年 | 23篇 |
2017年 | 11篇 |
2016年 | 24篇 |
2015年 | 18篇 |
2014年 | 16篇 |
2013年 | 31篇 |
2012年 | 43篇 |
2011年 | 36篇 |
2010年 | 27篇 |
2009年 | 22篇 |
2008年 | 30篇 |
2007年 | 40篇 |
2006年 | 33篇 |
2005年 | 42篇 |
2004年 | 19篇 |
2003年 | 21篇 |
2002年 | 30篇 |
2001年 | 20篇 |
2000年 | 22篇 |
1999年 | 25篇 |
1998年 | 17篇 |
1997年 | 24篇 |
1996年 | 17篇 |
1995年 | 12篇 |
1994年 | 14篇 |
1993年 | 8篇 |
1992年 | 4篇 |
1991年 | 2篇 |
1990年 | 5篇 |
1989年 | 3篇 |
1988年 | 1篇 |
1987年 | 2篇 |
1986年 | 1篇 |
1985年 | 6篇 |
1984年 | 3篇 |
1983年 | 1篇 |
1981年 | 1篇 |
1978年 | 1篇 |
1972年 | 1篇 |
1970年 | 1篇 |
1957年 | 1篇 |
排序方式: 共有752条查询结果,搜索用时 31 毫秒
151.
Pooley[1]发现氧化亚铁硫杆菌(Thiobacillusferroxidans)和氧化硫硫杆菌(Thiobacillusthiooxidans)能在其细胞表面累积银,形成Ag2S,每克干重细胞吸附250mgAg2S.文献[2]也报导了类似的研究结果.一些霉菌也具有吸收金、银等重金属的能力[3].Brierley等[4]研究了用微生物制备回收贵金属的去除剂(MRA),用它能从摄影废液中回收银,每克MRA累积94mgAg;同时指出,贵金属生物吸附也包含金属离子被还原为金属的过程.在微生物吸附还原贵金属前期研究[5-9]的基础上,我们从金、银矿土等不同来源的细菌菌株中,筛选获得一株吸附、还原Ag+… 相似文献
152.
Nanocrystalline tin‐oxide particles were prepared as electrodes on the bases of ITO glass and AT‐cut quartz crystals (sputtered gold), respectively, and characterized for their electrochemical behavior. Experiments suggested that the SnO2 particles could induce an energy barrier to the redox reactions taking place on the electrode surface. When the amount of SnO2 exceeded ca. 10?7 mol cm?2, electrochemical activity demonstrated by the solution redox couples was entirely suppressed. Nevertheless, electrochemical impedance spectroscopic (EIS) measurements suggested that mutual communication between redox couples would still take place on the surface of SnO2. For instance, although the CV curves of Fe(CN)63‐/4‐ were completely blocked, the exchange current of Fe(CN)63‐/4‐ could still flow through the tin‐oxide modified electrode, increasing with its concentration up to 40 mM. The propagation of electrons in the SnO2 film was likely via a hopping mechanism. Electrochemical quartz microbalance (EQCM) measurements, in addition, suggested that a charge‐compensating cation (K+ or H+) uptake reaction may be induced as electrons were pumped to the Sn02 electrode, while, if electrons were removed, that could cause water desorption. Analysis based on the Frumkin adsorption isotherm showed the driving force behind the adsorption of water on SnO2 is about ?2 kcal/mol. Nonetheless, the adsorbed water might face a competitive repulsion from acetonitrile when acetonitrile was used as the electrolyte medium. 相似文献
153.
Hung‐Te Chang Kuo‐Chen Chiang Fung Fuh Wong Chun‐Sheng Huang Yang‐Ming Liao Wen‐Fa Kuo Shaw‐Bing Won Mou‐Yung Yeh 《Heteroatom Chemistry》2007,18(4):438-442
The synthesis of potential fluorescent active 4‐(5‐aryl‐1,3,4‐oxadiazol‐2‐yl)phenylhydrazine derivatives was accomplished in three steps. The key step was the dehydration cyclization of 1,2‐diacylhydrazines to form the 1,3,4‐oxadiazole ring by use of acetic anhydride/perchloric acid mixture as the dehydrating agent. The sydnone moiety served as the masked hydrazines, which could be demasked by HCl for further application. © 2007 Wiley Periodicals, Inc. Heteroatom Chem 18:438–442, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20318 相似文献
154.
推导了振动轮式微机械陀螺的输出信号与输入角速度的幅频、相频关系,讨论了在不同的频率配置和品质因数下陀螺的灵敏度、带宽和零位稳定性。陀螺振动频率应设计在2kHz左右,检测轴自然频率比驱动轴高一个陀螺频带宽度。根据实测陀螺振动品质因数与气压的关系曲线,振动轮式微机械陀螺合适的工作气压是100Pa-1000Pa。 相似文献
155.
纳米ZnO颗粒在阳极Al2 O3模板中的强光致发光研究 总被引:1,自引:0,他引:1
用金属醇盐水解法在阳极Al2O3模板的有序孔洞中生长了纳米量级的ZnO颗粒,并用扫描电子显微镜(SEM)和高分辨电子显微镜(HRTEM)对其形貌进行观察.对纳米ZnO/多孔阳极Al2O3模板组装体的光致发光谱进行测量,将组装体中纳米ZnO颗粒的发光强度与常规方法制备的纳米ZnO颗粒发光强度做了比较,就发光强度提高的原因进行了讨论. 相似文献
156.
在理论上详细描述了一种新型的激光偏振移相干涉测振系统.通过计算机对两路正交干涉光电信号的接收和正弦逼近法数字处理,在1Hz~10KHz宽频带内测量振动台的振幅和初相位,从而实现加速度传感器复合灵敏度的绝对校准.运用琼斯矩阵证明干涉系统中通过偏振片调整可保证两信号的正交性. 相似文献
157.
Zaiguo Gan Junsheng Guo Hongye Liu Lijun Shi Weifan Yang Wantong Mou Tianrui Guo Keming Fang Shuifa Shen Shuanggui Yuan Xueqian Zhang Zhi Qin Ruichang Ma Jiquan Zhong Yixiao Luo Shuhong Wang Dengming Kong Jimin Qiao 《中国科学A辑(英文版)》1997,40(3):323-327
A new transuranium neutron-deficient isotope235Am was produced by 35 MeV proton to bombard the rare radioactive238Pu target. The products were transported and collected by the He-jet system. The Am isotopes were separated and purified by
radiochemistry method and the y-ray, X-ray and y-X(y) coincidence of the samples was measured. The synthesis of235Am was definitely identified. Its measured half-life is (15±5) min.
Project supported by the National Natural Science Foundation of China and the Chinese Academy of Sciences. 相似文献
158.
Chong-Jiang Cao Xi-Zhi Yu Chang-Lin Chen Nan-Ping Xu Yan-Ru Wang Chung-Yuan Mou 《Reaction Kinetics and Catalysis Letters》2004,83(1):85-92
Sulfated zirconia catalysts promoted by gallium or aluminium were prepared and tested for n-butane isomerization. Both elements increase and stabilize the isomerization rate. Characterization results showed that the
promoting mechanism of gallium was different from that of aluminium.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
159.
160.