全文获取类型
收费全文 | 8370篇 |
免费 | 1248篇 |
国内免费 | 1024篇 |
专业分类
化学 | 6324篇 |
晶体学 | 129篇 |
力学 | 415篇 |
综合类 | 65篇 |
数学 | 890篇 |
物理学 | 2819篇 |
出版年
2024年 | 6篇 |
2023年 | 162篇 |
2022年 | 212篇 |
2021年 | 285篇 |
2020年 | 345篇 |
2019年 | 310篇 |
2018年 | 293篇 |
2017年 | 279篇 |
2016年 | 424篇 |
2015年 | 426篇 |
2014年 | 518篇 |
2013年 | 627篇 |
2012年 | 762篇 |
2011年 | 824篇 |
2010年 | 597篇 |
2009年 | 584篇 |
2008年 | 576篇 |
2007年 | 533篇 |
2006年 | 424篇 |
2005年 | 383篇 |
2004年 | 303篇 |
2003年 | 207篇 |
2002年 | 212篇 |
2001年 | 147篇 |
2000年 | 137篇 |
1999年 | 142篇 |
1998年 | 126篇 |
1997年 | 105篇 |
1996年 | 106篇 |
1995年 | 72篇 |
1994年 | 88篇 |
1993年 | 58篇 |
1992年 | 60篇 |
1991年 | 58篇 |
1990年 | 40篇 |
1989年 | 53篇 |
1988年 | 37篇 |
1987年 | 38篇 |
1986年 | 15篇 |
1985年 | 15篇 |
1984年 | 11篇 |
1983年 | 10篇 |
1982年 | 6篇 |
1981年 | 11篇 |
1980年 | 4篇 |
1979年 | 5篇 |
1977年 | 1篇 |
1973年 | 2篇 |
1957年 | 2篇 |
1935年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 625 毫秒
81.
The type-II phase-matched third-harmonic light generation in a -BaB2O4 crystal is studied experimentally. A passively mode-locked Nd: phosphate glass laser is used as a pump source. At a pump pulse peak intensity ofI
10=5×1010W/cm2 a third-harmonic conversion efficiency of a percent is obtained. A theoretical discussion of phase-matched third-harmonic generation in crystals of the symmetry group of -BaB2O4 (trigonal class 3) is given. The effective nonlinear susceptibility eff for type-II phase-matching is determined.On leave from the Shanghai Institute of Optics and Fine Mechanics, Academia Sinica, Shanghai, P.R. China 相似文献
82.
The electronic structures of the laser crystal MgF2:V2+ were obtained with the spinpolarized MS-X
method. The calculated value of 10Dq and the energies of the lowest doublet states were given for the first time. The relations between the laser properties and the electronic structures were discussed. 相似文献
83.
蛋白质—四氯苯醌荷移反应的分光光度研究 总被引:5,自引:0,他引:5
本文用分光光度法研究了蛋白质—四氯苯醌荷移反应。通过对影响反应各因素的研究,确立了以四氯苯醌形成荷移络合物的方法测定蛋白质的最佳条件,测定了最大结合数及反应平衡常数。 相似文献
84.
穿过液膜的自发电势振荡 总被引:2,自引:0,他引:2
An artificial membrane consisting of pricramic acid in nitrobenzene was used as an oil phase imposed between two aqueous phases. The right one contained trimethyl-slearylammonium chloride and aicohol; and the left contained sucrose solution (or H_2O). We found that this system exhibited rhythmic oscillation of electrical potential. The amplitude of the oscillations was between 20—150 mV. The oscillations were observed even when ethyl alcohol was absent in the aqueous of trimethylslearylammonium Chloride, and the increase in amplitude of oscillation with time was found to be less in the presence of sucrose. Some of the expremental results have been explained. 相似文献
85.
以催化极谱法测定了54例白血病患者血清硒含量。结果表明,急淋、急粒患者血清硒含量均低于正常对照组,慢粒及急、慢粒经治疗缓解者血清硒含量与正常对照组间均无显著性差异,提示低硒状态只存在于急性患者,且随病情缓解后血硒水平趋于正常,慢粒与血硒含量没有明显的相关关系。 相似文献
86.
Tasuku Nakajima Takayuki Kurokawa Hidemitsu Furukawa Qiu Ming Yu Yoshimi Tanaka Yoshihito Osada Jian Ping Gong 《高分子科学》1996,(1):1-9
Living tissues work with fantastic functions in soft and wet gel-like state. Thus, hydrogels have attracted much attention as excellent soft & wet materials, suitable for making artificial organs for medical treatments.However, conventional hydrogels are mechanically too weak for practical uses. We have created double network (DN) hydrogels with extremely high mechanical strength in order to overcome this problem. DN gels are interpenetrating network (IPN) hydrogels consisting of rigid polyelectrolyte and soft neutral polymer. Their excellent mechanical properties cannot be explained by the standard fracture theories. In this paper, we discuss about the toughening mechanism of DN gels in accordance with their characteristic behavior, such as large hysteresis and necking phenomenon. We also describe the results on tissue engineering application of DN gels. 相似文献
87.
LiZHANG NaLI FengLinZHAO KeAnLI 《中国化学快报》2004,15(6):671-674
The interaction between heparin and neutral red was investigated by molecular spectroscopic methods. The change of all spectra suggested that positively charged neutral red had interacted with negatively charged heparin. The study of influence factors indicated that electrostatic force and hydrophobic bond might be involved in the interaction. The total binding number per disaccharide unit and intrinsic binding constant were obtained using Scatchard model. 相似文献
88.
89.
Song Hyung Keun Lee Hwaung Choi Jae-Wook Na Byung-ki 《Plasma Chemistry and Plasma Processing》2004,24(1):57-72
Methane conversion using an electric discharge has been studied for many years. Recently, many research groups have developed high-frequency pulsed plasma reaction for methane conversion to higher hydrocarbons and synthesis gas. CO2 reforming of methane to synthesis gas has also attracted considerable interest as a method of utilization of the greenhouse gases, CO2 and CH4, which occupy most of man-made greenhouse gases. In this study, the influence of pulse form of applied voltage on methane and carbon dioxide conversions and product selectivity has been investigated using a cylindrical type DBD reactor. For this purpose, two kinds of power supply were compared, that is, AC power supply which has a high-frequency sinusoidal wave form, and AC pulse power supply which has modified AC pulse wave form. The conversions of methane and carbon dioxide were enhanced using pulsed plasma. The lower pulse width was more profitable economically. 相似文献
90.
本实验开展了醋酸乙烯酯的可逆加成-断裂链转移自由基聚合(RAFT),分别运用偶氮二异丁腈(AIBN)引发和可见光引发两种方式进行了聚合反应,运用核磁共振和凝胶色谱等多种手段对所得聚合物结构进行了表征与分析。通过比较AIBN引发与光引发所获得聚合物端基结构的异同,加深了学生对RAFT聚合方法原理的理解。同时,运用该方法实现了聚合物两端端基结构的高度功能化,深入体会聚合物合成设计概念。本综合实验教学不仅通过对比法加深了学生对实验原理和专业知识的理解,提升了学生创新研究能力,而且训练了学生的实验操作技能、大型仪器使用能力和结果分析能力,提升了综合素质。 相似文献