全文获取类型
收费全文 | 4595篇 |
免费 | 243篇 |
国内免费 | 87篇 |
专业分类
化学 | 3125篇 |
晶体学 | 26篇 |
力学 | 151篇 |
综合类 | 10篇 |
数学 | 556篇 |
物理学 | 1057篇 |
出版年
2023年 | 20篇 |
2022年 | 32篇 |
2021年 | 62篇 |
2020年 | 80篇 |
2019年 | 72篇 |
2018年 | 68篇 |
2017年 | 65篇 |
2016年 | 125篇 |
2015年 | 120篇 |
2014年 | 162篇 |
2013年 | 263篇 |
2012年 | 305篇 |
2011年 | 348篇 |
2010年 | 206篇 |
2009年 | 161篇 |
2008年 | 284篇 |
2007年 | 271篇 |
2006年 | 265篇 |
2005年 | 266篇 |
2004年 | 208篇 |
2003年 | 178篇 |
2002年 | 159篇 |
2001年 | 100篇 |
2000年 | 123篇 |
1999年 | 60篇 |
1998年 | 46篇 |
1997年 | 44篇 |
1996年 | 44篇 |
1995年 | 60篇 |
1994年 | 55篇 |
1993年 | 55篇 |
1992年 | 48篇 |
1991年 | 32篇 |
1990年 | 30篇 |
1989年 | 26篇 |
1988年 | 31篇 |
1987年 | 32篇 |
1986年 | 21篇 |
1985年 | 28篇 |
1984年 | 30篇 |
1982年 | 30篇 |
1981年 | 29篇 |
1980年 | 22篇 |
1979年 | 39篇 |
1978年 | 32篇 |
1977年 | 32篇 |
1976年 | 26篇 |
1975年 | 22篇 |
1974年 | 22篇 |
1973年 | 14篇 |
排序方式: 共有4925条查询结果,搜索用时 15 毫秒
991.
纳米碳管复合凝胶玻璃结构及谱学性能研究 总被引:1,自引:1,他引:0
用物理掺杂工艺将纳米碳管引入二氧化硅凝胶玻璃基质,成功制备了纳米碳管复合凝胶玻璃,采用X射线衍射、透射电子显微镜、紫外-可见吸收光谱、红外光谱、拉曼光谱等测试方法对其结构和谱学性能进行了表征。结果表明,通过优化掺杂工艺能够实现纳米碳管与基质的均匀复合,纳米碳管本身的结构在掺杂过程中并未发生改变。纳米碳管的引入对二氧化硅凝胶玻璃基质的紫外-可见吸收光谱和红外光谱未产生显著影响。 相似文献
992.
Ang Han Wei Chan Aik Hui Ghaffar Mahumm Rybczyński Maciej Wilk Grzegorz Włodarczyk Zbigniew 《The European Physical Journal A - Hadrons and Nuclei》2020,56(4):1-8
The European Physical Journal A - The transverse momentum ($$p_{T}$$) distribution of strange hadrons ($$K_{S}^{0}$$ and $$\varLambda $$) and multi-strange hadrons( $$\varXi $$ and $$\varOmega $$)... 相似文献
993.
采用沉淀-沉积法制备了磁性Fe3O4@SiO2/Bi2 WO6/Ag2O催化材料,利用XRD、SEM和UV-Vis-DRS光谱对其组成、形貌和光吸收特性进行表征.以氙灯模拟可见光,以罗丹明B为模拟污染物对所得催化剂进行性能评价,考察了不同Ag2O复合量对Bi2WO6光催化剂反应活性的影响.结果表明,Fe3O4@SiO2/Bi2WO6/Ag2O的光催化活性明显优于纯Bi2 WO6,当Ag2 O的复合量为0.6;时,催化剂的活性最好.催化剂的活性增强增强机理分析表明,Ag2O的复合有效地降低了Bi2WO6的光生电子-空穴复合率,增加了Bi2WO6的可见光吸收范围.此外,该催化材料可进行磁分离,易于回收重复利用. 相似文献
994.
K. S. Chan 《International Journal of Plasticity》1988,4(4):355-370
The elastic-viscoplastic constitutive equations of Bodner-Partom were applied to modeling creep damage in a high temperature Ni-alloy, B1900 + Hf. Both tertiary creep in bulk materials and creep crack growth in flawed materials were considered. In the latter case, the energy rate line integral C* was used for characterizing the crack driving force, and the rate of crack extension was computed using a local damage formulation that assumed fracture was controlled by cavitation occurring within the crack-tip process zone. The results of this investigation were used to assess the evolution equation for isotropic damage utilized in the Bodner-Partom constitutive equations. 相似文献
995.
Ying Zhou Shuofeng Yuan Kelvin Kai-Wang To Xiaohan Xu Hongyan Li Jian-Piao Cai Cuiting Luo Ivan Fan-Ngai Hung Kwok-Hung Chan Kwok-Yung Yuen Yu-Feng Li Jasper Fuk-Woo Chan Hongzhe Sun 《Chemical science》2022,13(11):3216
The ongoing COVID-19 pandemic caused by SARS-CoV-2 highlights the urgent need to develop sensitive methods for diagnosis and prognosis. To achieve this, multidimensional detection of SARS-CoV-2 related parameters including virus loads, immune response, and inflammation factors is crucial. Herein, by using metal-tagged antibodies as reporting probes, we developed a multiplex metal-detection based assay (MMDA) method as a general multiplex assay strategy for biofluids. This strategy provides extremely high multiplexing capability (theoretically over 100) compared with other reported biofluid assay methods. As a proof-of-concept, MMDA was used for serologic profiling of anti-SARS-CoV-2 antibodies. The MMDA exhibits significantly higher sensitivity and specificity than ELISA for the detection of anti-SARS-CoV-2 antibodies. By integrating the high dimensional data exploration/visualization tool (tSNE) and machine learning algorithms with in-depth analysis of multiplex data, we classified COVID-19 patients into different subgroups based on their distinct antibody landscape. We unbiasedly identified anti-SARS-CoV-2-nucleocapsid IgG and IgA as the most potently induced types of antibodies for COVID-19 diagnosis, and anti-SARS-CoV-2-spike IgA as a biomarker for disease severity stratification. MMDA represents a more accurate method for the diagnosis and disease severity stratification of the ongoing COVID-19 pandemic, as well as for biomarker discovery of other diseases.A MMDA platform is developed by using metal-tagged antibodies as reporting probes combined with machine learning algorithms, as a general strategy for highly multiplexed biofluid assay. 相似文献
996.
997.
以聚氧乙烯和全氟辛基聚氧乙烯醚(FPEOE)为起始原料, 合成了一系列的特种氟表面活性剂及其丙烯酸酯, 用FTIR和1H NMR对其结构进行了表征, 用最大气泡法测定了其表面张力. 以其作为接枝单体, 利用反应挤出接枝的方法制备了系列功能化聚乙烯, 用FTIR确定了接枝共聚物的结构和接枝率; 用DSC、接触角测量仪和XPS对接枝共聚物的热性能、结晶行为和表面性能进行了测试分析. 结果表明, 随着聚氧乙烯分子量的增加, 氟表面活性剂的表面活性降低; 聚乙烯接枝共聚物的结晶温度高于线形低密度聚乙烯, 且具有较好的亲水性. 相似文献
998.
Tang Chak-yin Fan Jianping Tsui Chi-pong Lee Tai-chiu Chad Luen-chow Rao Bin 《Acta Mechanica Solida Sinica》2007,20(1):57-64
Shear damage may occur in the process of metal machining such as blanking and cutting, where localized shear deformation is developed. Experimental findings indicate that microscopic shear damage evolution in aluminium alloy 2024T3 (A1 2024T3) is a multi-stage mechanism, including particle cracking, micro-shear banding, matrix microcracking and coalescence of microcracks. This study is an attempt to use a set of equations to describe the multi-stage shear damage evolution in Al 2024T3. The shear damage variables in terms of multi-couple parameters of a power-law hardening material have been defined. An evolution curve of shearing damage has been calculated from experimental data. The values of the shear damage variable at different stages of damage have also been calculated. By making use of the findings, the relation between the microscopic shear damage evolution and the macroscopic shear response of the material has been discussed. 相似文献
999.
This paper reports the effect of annealing on conduction mechanisms in amorphous silicon films. High field transport is mainly by the Poole-Frenkel mechanism in unannealed films of amorphous silicon. As they are annealed, the conduction meachnism changes from Poole-Frenkel to space charge conduction. The films are fully annealed at 120°C for 15 h and any more annealing for longer periods does not change the I–V characteristics. From the measured values of threshold voltage at which space charge conduction sets in, the density of localized states around the Fermi level is calculated to be about 1017–1018/eV · cm3 which agrees very well with our results from other experimental techniques. 相似文献
1000.
The corrosion behavior and surface morphology of Ni–SiC composite coatings produced by electrodeposition with the aid of magnetic
field were studied. The results of the electrochemical analysis including polarization resistance and potentiodynamic polarization
curves showed that a magnetic field of 0.1 T could significantly improve the corrosion resistance of the composite. The electrochemical
impedance spectra revealed that a passive layer was formed on the surface of the Ni–SiC coating with the magnetic field. The
microstructures of electrodeposited Ni–SiC composite coatings were also examined. More SiC particles were found to be incorporated
into the coating with the presence of magnetic field, which was considered to be one of the reasons for the enhancement of
corrosion resistance as SiC particles were reported to be corrosion inhibitors.
Contribution to special issue “Magnetic field effects in Electrochemistry” 相似文献