全文获取类型
收费全文 | 4232篇 |
免费 | 147篇 |
国内免费 | 23篇 |
专业分类
化学 | 2883篇 |
晶体学 | 34篇 |
力学 | 156篇 |
数学 | 404篇 |
物理学 | 925篇 |
出版年
2024年 | 18篇 |
2023年 | 38篇 |
2022年 | 256篇 |
2021年 | 196篇 |
2020年 | 147篇 |
2019年 | 136篇 |
2018年 | 163篇 |
2017年 | 115篇 |
2016年 | 160篇 |
2015年 | 164篇 |
2014年 | 165篇 |
2013年 | 309篇 |
2012年 | 255篇 |
2011年 | 281篇 |
2010年 | 158篇 |
2009年 | 141篇 |
2008年 | 148篇 |
2007年 | 169篇 |
2006年 | 127篇 |
2005年 | 133篇 |
2004年 | 84篇 |
2003年 | 80篇 |
2002年 | 70篇 |
2001年 | 71篇 |
2000年 | 53篇 |
1999年 | 58篇 |
1998年 | 27篇 |
1997年 | 27篇 |
1996年 | 43篇 |
1995年 | 40篇 |
1994年 | 27篇 |
1993年 | 31篇 |
1992年 | 34篇 |
1991年 | 40篇 |
1990年 | 19篇 |
1989年 | 20篇 |
1988年 | 28篇 |
1987年 | 26篇 |
1986年 | 26篇 |
1985年 | 38篇 |
1984年 | 23篇 |
1983年 | 23篇 |
1982年 | 22篇 |
1981年 | 11篇 |
1980年 | 28篇 |
1979年 | 21篇 |
1978年 | 27篇 |
1977年 | 27篇 |
1976年 | 19篇 |
1968年 | 11篇 |
排序方式: 共有4402条查询结果,搜索用时 0 毫秒
51.
52.
Sangeeta Kumari Aundrea Roman Arshad Khan 《Journal of polymer science. Part A, Polymer chemistry》1996,34(14):2975-2980
The experimental UV-vis spectrum of the glycogen-iodine (GI) complex shows certain features remarkably similar to that of the amylopectin-iodine (API) complex [J. Polymer. Chem. 32, 2257 (1994)], suggesting a strong similarity between the API and the GI structures. As in the API complex, a nearly linear polyiodine unit, I4, at an interiodine distance of around 3 Å is expected to exist within the helix of 11 anhydroglucose units (AGUs). There are several other spectral features that suggest the presence of another similar but more loosely bound iodine species with a longer interiodine distance of 3.1 Å. These findings suggest the involvement of two different types of glycogen chains in binding iodine molecules. © 1996 John Wiley & Sons, Inc. 相似文献
53.
Momeen M. Y. Khan 《Crystal Research and Technology》1996,31(5):629-635
The CdI2 material grown under similar thermodynamic conditions exhibits several polytypes (phases). Out of these the basic phases are thermodynamically independent and grow with their minimum free (potential) energy. In the present paper we have calculated the Madelung constants cohesive (potential) and the phase transformation energy for the basic phases viz. 2H → 4 H. 相似文献
54.
Mustapha Muhammad Nasiru Muhammad Umair Evans Frimpong Boateng Fawze Alnadari Kashif-ur Rehman Khan Zhaobin Wang Ji Luo Wenjing Yan Hong Zhuang Ali Majrashi Jianhao Zhang Sameh A. Korma 《Molecules (Basel, Switzerland)》2022,27(3)
Egg white protein (EWP) is susceptible to denaturation and coagulation when exposed to high temperatures, adversely affecting its flavour, thereby influencing consumers’ decisions. Here, we employ high-voltage cold plasma (HVCP) as a novel nonthermal technique to investigate its influence on the EWP’s flavour attributes using E-nose, E-tongue, and headspace gas-chromatography-ion-mobilisation spectrometry (HS-GC-IMS) due to their rapidness and high sensitivity in identifying flavour fingerprints in foods. The EWP was investigated at 0, 60, 120, 180, 240, and 300 s of HVCP treatment time. The results revealed that HVCP significantly influences the odour and taste attributes of the EWP across all treatments, with a more significant influence at 60 and 120 s of HVCP treatment. Principal component analyses of the E-nose and E-tongue clearly distinguish the odour and taste sensors’ responses. The HS-GC-IMS analysis identified 65 volatile compounds across the treatments. The volatile compounds’ concentrations increased as the HVCP treatment time was increased from 0 to 300 s. The significant compounds contributing to EWP characterisation include heptanal, ethylbenzene, ethanol, acetic acid, nonanal, heptacosane, 5-octadecanal, decanal, p-xylene, and octanal. Thus, this study shows that HVCP could be utilised to modify and improve the EWP flavour attributes. 相似文献
55.
Haroon Khan Waqas Alam Khalaf F. Alsharif Michael Aschner Samreen Pervez Luciano Saso 《Molecules (Basel, Switzerland)》2022,27(3)
Cancer is the second most fatal disease worldwide, with colon cancer being the third most prevalent and fatal form of cancer in several Western countries. The risk of acquisition of resistance to chemotherapy remains a significant hurdle in the management of various types of cancer, especially colon cancer. Therefore, it is essential to develop alternative treatment modalities. Naturally occurring alkaloids have been shown to regulate various mechanistic pathways linked to cell proliferation, cell cycle, and metastasis. This review aims to shed light on the potential of alkaloids as anti-colon-cancer chemotherapy agents that can modulate or arrest the cell cycle. Preclinical investigated alkaloids have shown anti-colon cancer activities and inhibition of cancer cell proliferation via cell cycle arrest at different stages, suggesting that alkaloids may have the potential to act as anticancer molecules. 相似文献
56.
The oxidation of transition metals such as manganese and copper by dioxygen (O2) is of great interest to chemists and biochemists for fundamental and practical reasons. In this report, the O2 reactivities of 1:1 and 1:2 mixtures of [(TPP)MnII] (1; TPP: Tetraphenylporphyrin) and [(tmpa)CuI(MeCN)]+ (2; TMPA: Tris(2-pyridylmethyl)amine) in 2-methyltetrahydrofuran (MeTHF) are described. Variable-temperature (−110 °C to room temperature) absorption spectroscopic measurements support that, at low temperature, oxygenation of the (TPP)Mn/Cu mixtures leads to rapid formation of a cupric superoxo intermediate, [(tmpa)CuII(O2•–)]+ (3), independent of the presence of the manganese porphyrin complex (1). Complex 3 subsequently reacts with 1 to form a heterobinuclear μ-peroxo species, [(tmpa)CuII–(O22–)–MnIII(TPP)]+ (4; λmax = 443 nm), which thermally converts to a μ-oxo complex, [(tmpa)CuII–O–MnIII(TPP)]+ (5; λmax = 434 and 466 nm), confirmed by electrospray ionization mass spectrometry and nuclear magnetic resonance spectroscopy. In the 1:2 (TPP)Mn/Cu mixture, 4 is subsequently attacked by a second equivalent of 3, giving a bis-μ-peroxo species, i.e., [(tmpa)CuII−(O22−)−MnIV(TPP)−(O22−)−CuII(tmpa)]2+ (7; λmax = 420 nm and δpyrrolic = −44.90 ppm). The final decomposition product of the (TPP)Mn/Cu/O2 chemistry in MeTHF is [(TPP)MnIII(MeTHF)2]+ (6), whose X-ray structure is also presented and compared to literature analogs. 相似文献
57.
Muhammad Omer Iqbal Muhammad Masood Ahmed Shafia Arshad Usman Javaid Imran Ahmad Khan Majid Manzoor Shumaila Andleeb Romana Riaz Shaukat Hussain Munawar Zahid Manzoor Asma Mumtaz 《Molecules (Basel, Switzerland)》2022,27(3)
Alhagi camelorum (AC) is an old plant with a significant therapeutic value throughout Africa, Asia, and Latin America. The overuse of cisplatin (Cis > 50 mg/m2) is associated with observed nephrotoxicity, ototoxicity, gastrotoxicity, myelosuppression, and allergic reactions. Remedial measures are needed for the protection of nephrotoxicity against cisplatin. Thus, we investigated the nephroprotective effects of AC plant extract to prevent cisplatin-induced nephrotoxicity in albino Wistar rats. The presence of polyphenols, phenolic compounds, tannins, and saponins was revealed during phytochemical investigation, and a significantly intense antioxidant activity was recorded. There were no toxicological symptoms in the treated rats, and no anatomical, physiological, or histological abnormalities were found compared to the control rats. The results of correcting cisplatin-induced nephrotoxicity revealed that the extract has a significant ability to treat kidney damage, with most parameters returning to normal after only three weeks of therapy. It is concluded that co-administration of cisplatin with AC extract showed exceptional nephroprotective effects at a dose of 600 mg/kg for Cis-induced nephrotoxicity. 相似文献
58.
Riju Khandaker M. Kamruzzaman M. Afrose R. Rahman M. Khan M. K. R. Liton M. N. H. Helal M. A. Anam T. K. Rahman M. M. 《Crystallography Reports》2020,65(6):968-979
Crystallography Reports - Transition metals doped FeS2 thin films are promising materials for optoelectronics, energy saving and storage applications. This is a first time report on the... 相似文献
59.
60.
Dysfunction of the blood–brain barrier (BBB) is involved in the pathogenesis of many cerebral diseases. Oxidative stress and inflammation are contributing factors for BBB injury. Piceatannol, a natural ingredient found in various plants, such as grapes, white tea, and passion fruit, plays an important role in antioxidant and anti-inflammatory responses. In this study, we examined the protective effects of piceatannol on lipopolysaccharide (LPS) insult in mouse brain endothelial cell line (bEnd.3) cells and the underlying mechanisms. The results showed that piceatannol mitigated the upregulated expression of adhesion molecules (ICAM-1 and VCAM-1) and iNOS in LPS-treated bEnd.3 cells. Moreover, piceatannol prevented the generation of reactive oxygen species in bEnd.3 cells stimulated with LPS. Mechanism investigations suggested that piceatannol inhibited NF-κB and MAPK activation. Taken together, these observations suggest that piceatannol reduces inflammation and oxidative stress through inactivating the NF-κB and MAPK signaling pathways on cerebral endothelial cells in vitro. 相似文献