全文获取类型
收费全文 | 7765篇 |
免费 | 1384篇 |
国内免费 | 2684篇 |
专业分类
化学 | 6138篇 |
晶体学 | 371篇 |
力学 | 487篇 |
综合类 | 184篇 |
数学 | 1052篇 |
物理学 | 3601篇 |
出版年
2024年 | 23篇 |
2023年 | 135篇 |
2022年 | 362篇 |
2021年 | 318篇 |
2020年 | 345篇 |
2019年 | 361篇 |
2018年 | 310篇 |
2017年 | 411篇 |
2016年 | 373篇 |
2015年 | 477篇 |
2014年 | 523篇 |
2013年 | 664篇 |
2012年 | 614篇 |
2011年 | 671篇 |
2010年 | 659篇 |
2009年 | 644篇 |
2008年 | 743篇 |
2007年 | 654篇 |
2006年 | 635篇 |
2005年 | 530篇 |
2004年 | 402篇 |
2003年 | 291篇 |
2002年 | 267篇 |
2001年 | 284篇 |
2000年 | 251篇 |
1999年 | 144篇 |
1998年 | 85篇 |
1997年 | 60篇 |
1996年 | 71篇 |
1995年 | 72篇 |
1994年 | 57篇 |
1993年 | 62篇 |
1992年 | 61篇 |
1991年 | 48篇 |
1990年 | 41篇 |
1989年 | 32篇 |
1988年 | 25篇 |
1987年 | 22篇 |
1986年 | 19篇 |
1985年 | 12篇 |
1984年 | 16篇 |
1983年 | 14篇 |
1982年 | 14篇 |
1981年 | 8篇 |
1980年 | 4篇 |
1979年 | 5篇 |
1971年 | 4篇 |
1960年 | 1篇 |
1959年 | 1篇 |
1936年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
Xiaohui Duan Mina Zhang Huan Du Xiu Gu Caihong Bai Liuqiang Zhang Kaixian Chen Kaifeng Hu Yiming Li 《Molecules (Basel, Switzerland)》2022,27(15)
Scrophulariae Radix (SR) is one of the oldest and most frequently used Chinese herbs for oriental medicine in China. Before clinical use, the SR should be processed using different methods after harvest, such as steaming, “sweating”, and traditional fire-drying. In order to investigate the difference in chemical constituents using different processing methods, the two-dimensional (2D) 1H-13C heteronuclear single quantum correlation (1H-13C HSQC)-based metabolomics approach was applied to extensively characterize the difference in the chemical components in the extracts of SR processed using different processing methods. In total, 20 compounds were identified as potential chemical markers that changed significantly with different steaming durations. Seven compounds can be used as potential chemical markers to differentiate processing by sweating, hot-air drying, and steaming for 4 h. These findings could elucidate the change of chemical constituents of the processed SR and provide a guide for the processing. In addition, our protocol may represent a general approach to characterizing chemical compounds of traditional Chinese medicine (TCM) and therefore might be considered as a promising approach to exploring the scientific basis of traditional processing of TCM. 相似文献
12.
Carbamazepine (CBZ), as a typical pharmaceutical and personal care product (PPCP), cannot be efficiently removed by the conventional drinking water and wastewater treatment process. In this work, the CoS2/Fe2+/PMS process was applied for efficient elimination of CBZ. The CBZ removal efficiency of CoS2/Fe2+/PMS was 2.5 times and 23 times higher than that of CoS2/PMS and Fe2+/PMS, respectively. The intensity of DMPO-HO• and DMPO- followed the order of Fe2+/PMS < CoS2/PMS < CoS2/Fe2+/PMS, also suggesting the CoS2/Fe2+/PMS process has the highest oxidation activity. The effects of reaction conditions (e.g., CoS2 dosage, Fe2+ concentration, PMS concentration, initial CBZ concentration, pH, temperature) and water quality parameters (e.g., , , , , , humic acid) on the degradation of CBZ were also studied. Response surface methodology analysis was carried out to obtain the best conditions for the removal of CBZ, which are: Fe2+ = 70 µmol/L, PMS = 240 µmol/L, CoS2 = 0.59 g/L. The sustainability test demonstrated that the repeated use of CoS2 for 8 successive cycles resulted in little function decrease (<10%). These findings suggest that CoS2/Fe2+/PMS may be a promising method for advanced treatment of tailwater from sewage treatment plant. 相似文献
13.
一种超高耐久混凝土——梯度结构混凝土 总被引:2,自引:1,他引:1
分析超高耐久混凝土的研究现状,提出了一种高耐久、低成本的超高耐久混凝土--梯度结构混凝土(Gradient Structural Concrete,简称GSC),采用电量法和氯离子扩散系数法来评价梯度结构混凝土的抗氯离子渗透性能,最后进行梯度结构混凝土的寿命预测与成本分析.结果表明,高性能混凝土(High Performance Concrete,简称HPC)、无细观界面过渡区水泥基复合材料(Meso-interfacial transition zone-free cement-based materials,简称 MIF)和梯度结构混凝土MIF-HPC的6 h导电量和氯离子扩散系数的排列顺序均为:HPC>MIF-HPC>MIF,其抗氯离子渗透性能排列顺序为:MIF>MIF-HPC>HPC.梯度结构混凝土的成本会有所增加,但由于其氯离子渗透性能大幅降低,其使用寿命得到大幅延长,使得其年损耗费用大幅下降. 相似文献
14.
15.
16.
17.
SONG Gang ZHANG Kai CHEN YuanYuan LIU HuiLi WU Chao YU Li XIAO JingHua 《中国科学:物理学 力学 天文学(英文版)》2013,(4):680-684
We successfully investigate an optical bistability phenomenon in a layered structure consisting of Kretschmann configuration involving the Kerr-type nonlinear and the silver film. Pure theoretical approaches are employed to investigate that the surface plasmon could easily be coupled and both the reflection and transmission curves versus the incident intensity forms optical bistability. The transmission curves are greatly influenced by the thickness of the second silver film. These results may be useful for designing novel surface plasmon-based optical devices and will be essential for future classical and quantum information processes. 相似文献
18.
19.
20.