全文获取类型
收费全文 | 1104篇 |
免费 | 35篇 |
国内免费 | 8篇 |
专业分类
化学 | 831篇 |
晶体学 | 15篇 |
力学 | 17篇 |
数学 | 75篇 |
物理学 | 209篇 |
出版年
2024年 | 5篇 |
2023年 | 11篇 |
2022年 | 68篇 |
2021年 | 58篇 |
2020年 | 48篇 |
2019年 | 39篇 |
2018年 | 52篇 |
2017年 | 34篇 |
2016年 | 58篇 |
2015年 | 34篇 |
2014年 | 49篇 |
2013年 | 82篇 |
2012年 | 76篇 |
2011年 | 73篇 |
2010年 | 43篇 |
2009年 | 42篇 |
2008年 | 29篇 |
2007年 | 37篇 |
2006年 | 38篇 |
2005年 | 38篇 |
2004年 | 33篇 |
2003年 | 28篇 |
2002年 | 31篇 |
2001年 | 7篇 |
2000年 | 15篇 |
1997年 | 2篇 |
1996年 | 6篇 |
1995年 | 5篇 |
1993年 | 6篇 |
1992年 | 12篇 |
1991年 | 5篇 |
1990年 | 7篇 |
1989年 | 2篇 |
1988年 | 2篇 |
1986年 | 3篇 |
1984年 | 3篇 |
1983年 | 6篇 |
1982年 | 2篇 |
1981年 | 3篇 |
1980年 | 2篇 |
1979年 | 2篇 |
1978年 | 11篇 |
1977年 | 3篇 |
1976年 | 4篇 |
1975年 | 7篇 |
1974年 | 4篇 |
1972年 | 7篇 |
1971年 | 5篇 |
1967年 | 2篇 |
1958年 | 1篇 |
排序方式: 共有1147条查询结果,搜索用时 406 毫秒
81.
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
82.
The dispersion relations and Landau damping of Alfven waves in kinetic and inertial limits are studied in temperature anisotropic Cairns distributed plasma.In the case of kinetic Alfven waves(KAWs),it is found that the real frequency is enhanced when either the electron perpendicular temperature or the non-thermal parameter A increases.For inertial Alfven waves(IAWs),the real frequency is slightly affected by the electron temperature anisotropy and A.Besides the real frequency,the damping rate of KAWs is reduced when the electron perpendicular temperature or A increases.In the case of IAWs,the temperature anisotropy and A either enhance or reduce the damping rate depending upon the perpendicular wavelength.These results may be helpful to understand the dynamics of KAWs and IAWs in space plasmas where the non-Maxwellian distribution of particles are routinely observed. 相似文献
83.
经过数次技术研究和超常创新战略的大发展,生物催化逐渐达到工业化水平,从而受到人们特别的关注.基于酶值,通过生物途径生产高附加值化合物和精细工业化学品成为人们最感兴趣的领域之一.更广泛的众多生物化学路线可由酶催化来实现,其中还有一些酶尚未被人们发现.另一方面,由于非同源底物和某些化学过程所必需的苛刻条件,导致酶催化过程的效率低、稳定性差,因而限制了生物催化的应用.因此,开发具有多催化特征、更高效率和稳定性的绿色催化剂,成为生物催化的重中之重.计算科学、代谢工程、合成生物,以及机器学习路线的运用为新催化剂的工程化提供了新方法.本文重点介绍了合成生物学和代谢工程在催化中的作用,讨论了用于催化的机器学习算法和如何选择一种预测蛋白质-配体相互作用的算法;为了预测键合和催化功能,综述了分子对接的重要性;最后给出了结束语、未来挑战和前景展望. 相似文献
84.
T. Bashir A. Shakoor E. Ahmed N. A. Niaz Shahid Iqbal Muhammad Saeed Akhtar Mohammad Azad Malik 《Polymer Science Series A》2017,59(6):902-908
This research paper comprises of the synthesis of polypyrrole (PPy)-Fe2O3 nanocomposites by employing the in situ chemical oxidative polymerization method. The concentration of the filler material was adjusted between 10–50 wt % of PPy. The synthesized nanocomposites were characterized by using X-ray diffraction (XRD). Magnetic analysis and DC electrical conductivity of the samples were carried out using vibrating sample magnetometer (VSM) and two probe DC conductivity method, point towards magnetically active and electrically conductive samples. The magnetic parameters under applied magnetic field demonstrated that the values of coercivity (H c ), saturation magnetization (M s ) and remanence (M r ) can be tailored by carefully controlling the amount of dopant material into the nanocomposites indicating their suitability for controllable switching devices and microwave absorption applications. The DC electrical conductivity showed an increase up to 20 wt % of filler material and thereafter a decrease in the conductivity of nanocomposites with increase in filler content is observed. Thermogravimetric analysis (TGA) showed an increase in thermal stability with an increase in ferrite content in nanocomposites. 相似文献
85.
Saurabh Bhatia Rashita Makkar Tapan Behl Aayush Sehgal Sukhbir Singh Mahesh Rachamalla Vasudevan Mani Muhammad Shahid Iqbal Simona Gabriela Bungau 《Molecules (Basel, Switzerland)》2022,27(5)
Marine drugs are abundant in number, comprise of a diverse range of structures with corresponding mechanisms of action, and hold promise for the discovery of new and better treatment approaches for the management of several chronic diseases. There are huge reserves of natural marine biological compounds, as 70 percent of the Earth is covered with oceans, indicating a diversity of chemical entities on the planet. The marine ecosystems are a rich source of bioactive products and have been explored for lead drug molecules that have proven to be novel therapeutic targets. Over the last 70 years, many structurally diverse drug products and their secondary metabolites have been isolated from marine sources. The drugs obtained from marine sources have displayed an exceptional potential in the management of a wide array of diseases, ranging from acute to chronic conditions. A beneficial role of marine drugs in human health has been recently proposed. The current review highlights various marine drugs and their compounds and role in the management of chronic diseases such as cancer, diabetes, neurodegenerative diseases, and cardiovascular disorders, which has led to the development of new drug treatment approaches. 相似文献
86.
Yousaf Raffia bintay Bakar Shahzad Abu Mazhar Muhammad Mansoor Muhammad Adil Iqbal Mudassir 《Russian Journal of Applied Chemistry》2022,95(1):37-45
Russian Journal of Applied Chemistry - Owing to high stability, metal oxide-based ceramic thin films are of great interest for photocatalytic oxidation of water. Therefore, the current research is... 相似文献
87.
Sodium bromide efficiently catalyses the regioselective cleavage of oxiranes with chlorotrimethylsilane to the corresponding O-silylated chlorohydrins in excellent yields. 相似文献
88.
Atta-Ur-Rahman Nasim S Baig I Ara Jahan I Sener B Orhan I Choudhary MI 《Chemical & pharmaceutical bulletin》2002,50(8):1100-1102
Four isoflavone glycosides were isolated from the rhizomes of Iris germanica. Compounds 1 and 2 are new, while compounds 3 and 4 are known isoflavone glycosides. These compounds were identified as iriskashmirianin 4'-O-beta-D-glucoside (1), nigricin 4'-O-beta-D-glucoside (2), irilone 4'-O-beta-D-glucoside (3) and iridin (4). Their structures were determined with the help of spectroscopic methods. 相似文献
89.
N-Cinnamoyl-L-proline can be used as a template on which beta-substituted phenylalanine and beta-phenylisoserine residues can be synthesized leading to tripeptide derivatives as structural analogues of HIV protease inhibitors. 相似文献
90.
Synthesis of small cyclic peptides via reverse turn induced ring closing metathesis of tripeptides 总被引:1,自引:0,他引:1
A reverse turn induced (gamma/beta-turn) cyclization of tripeptides 1 can be performed in a ring closing metathesis reaction with Grubbs' catalyst to the corresponding cyclic peptides 2. These cyclic peptides may be useful probes as a conformationally constrained mimic of the bioactive conformation of structurally related HIV protease inhibitors. 相似文献