全文获取类型
收费全文 | 20064篇 |
免费 | 3660篇 |
国内免费 | 2948篇 |
专业分类
化学 | 14871篇 |
晶体学 | 263篇 |
力学 | 1414篇 |
综合类 | 173篇 |
数学 | 2129篇 |
物理学 | 7822篇 |
出版年
2024年 | 43篇 |
2023年 | 410篇 |
2022年 | 519篇 |
2021年 | 651篇 |
2020年 | 875篇 |
2019年 | 771篇 |
2018年 | 672篇 |
2017年 | 588篇 |
2016年 | 940篇 |
2015年 | 938篇 |
2014年 | 1104篇 |
2013年 | 1394篇 |
2012年 | 1800篇 |
2011年 | 1873篇 |
2010年 | 1300篇 |
2009年 | 1254篇 |
2008年 | 1424篇 |
2007年 | 1242篇 |
2006年 | 1213篇 |
2005年 | 1020篇 |
2004年 | 797篇 |
2003年 | 678篇 |
2002年 | 701篇 |
2001年 | 599篇 |
2000年 | 445篇 |
1999年 | 513篇 |
1998年 | 353篇 |
1997年 | 309篇 |
1996年 | 359篇 |
1995年 | 312篇 |
1994年 | 290篇 |
1993年 | 223篇 |
1992年 | 206篇 |
1991年 | 181篇 |
1990年 | 146篇 |
1989年 | 121篇 |
1988年 | 109篇 |
1987年 | 73篇 |
1986年 | 63篇 |
1985年 | 48篇 |
1984年 | 31篇 |
1983年 | 26篇 |
1982年 | 14篇 |
1981年 | 18篇 |
1980年 | 7篇 |
1979年 | 5篇 |
1977年 | 3篇 |
1957年 | 6篇 |
1955年 | 1篇 |
1936年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
Zheng Yuanzhou Yang Haoran Mazaheri Hossein Aghaei Alireza Mokhtari Namjoo Afrand Masoud 《Journal of Thermal Analysis and Calorimetry》2021,143(2):1425-1438
Journal of Thermal Analysis and Calorimetry - The purpose of this study is to numerically investigate flow field and turbulent heat transfer of hybrid nanofluid, water–DWCNT–TiO2 in a... 相似文献
22.
Hejia Hu Linlin Wu Mei Li Cun Xue Guangcheng Wang Siying Chen Yong Huang Lin Zheng Aimin Wang Yueting Li Zipeng Gong 《Biomedical chromatography : BMC》2020,34(1):e4714
Eucommia ulmoides Oliv. (E. ulmoides) is a valuable and nourishing medicinal herb in China that has been used in the treatment of hypertension. Given the fact that most traditional Chinese medicine is mainly used to treat disease, investigating the pharmacokinetics of traditional Chinese medicines in the pathological state is more useful than that in the normal state. However, the differences in the absorption kinetics of active ingredients of E. ulmoides extract between pathological and physiological conditions have not been reported. Therefore, in this study, the rat intestinal in situ circulatory perfusion model was used to investigate the differences in absorption kinetics of seven active ingredients of E. ulmoides extract in normal and spontaneously hypertensive rats, namely, genipinic acid, protocatechuic acid, neochlorogenic acid, chlorogenic acid, cryptochlorogenic acid, (+)-pinoresinol di-O-β-D -glucopyranoside and (+)-pinoresinol 4′-O-β-D -glucopyranoside. Our results indicate that the pathological state of spontaneous hypertension may change the absorption of active components of E. ulmoides extracts, and these findings may provide a reference for improving the rational use of E. ulmoides in the clinic. 相似文献
23.
Dong Zheng Fu-Quan Wang Yuan-Guang Li Liang-Hong Guo Jing Cheng 《Analytica chimica acta》2004,508(2):225-231
Optimized combination of chemical agents was selected for sensitive electrochemical detection of dissolved ruthenium tris-(2,2′-bipyridine) (Ru-bipy). The detection was based on the chemical amplification mechanism, in which the anodic current of a redox-active analyte was amplified by a sacrificial electron donor in solution. On indium-doped tin oxide (ITO) electrodes, electrochemical reaction of the analyte was reversible, but that of the electron donor was greatly suppressed. Several transition metal complexes, such as ferrocene and tris-(2,2′-bipyridine) complexes of osmium, iron and ruthenium, were evaluated as model analyte. A correlation between the amplified current and the standard potential of the complex was observed, and Ru-bipy generated the largest current. A variety of organic bases, acids and zwitterions were assessed as potential electron donor. Sodium oxalate was found to produce the largest amplification factor. With Ru-bipy as the model analyte and oxalate as the electron donor, the analyte concentration curve was linear up to 50 μM, with a lower detection limit of approximately 50 nM. Preliminary work was presented in which a Ru-bipy derivative was attached to bovine serum albumin and detected electrochemically. Although the combination of Ru-bipy, oxalate and ITO electrode has been used before for electrochemiluminescent detection of Ru-bipy and oxalate, as well as electrochemical detection of oxalate, its utility in amplified voltammetric detection of Ru-bipy as a potential electrochemical label has not been reported previously. 相似文献
24.
25.
26.
27.
本文在一类 Lp位势V(x)下建立了广义Schrodinger算子H=(-Δ)m+V(x)在C∞0(Rn)上的本质自伴性,给出了H的本质谱的分布. 相似文献
28.
Yuxi Zheng 《Communications in Mathematical Physics》1991,135(3):581-594
We show that the weak-L
2 limit of a sequence of solutions of the two dimensional incompressible Euler equation is still a solution, provided that a (strong) concentration set for the reduced defect measure has locally finite one dimensional Hausdorff measure in space and time. 相似文献
29.
30.
meso-Tetra(n-hexyloxycarbonyl)porphyrin was found to be converted into porphine, the mother compound of porphyrins, in a 77% yield when heated in aqueous sulfuric acid at 180 °C over 30 min under an inert atmosphere. The observation demonstrates that the substituted porphyrin serves as a novel and useful precursor for porphine. 相似文献