全文获取类型
收费全文 | 4326篇 |
免费 | 199篇 |
国内免费 | 41篇 |
专业分类
化学 | 2862篇 |
晶体学 | 41篇 |
力学 | 139篇 |
数学 | 446篇 |
物理学 | 1078篇 |
出版年
2024年 | 19篇 |
2023年 | 45篇 |
2022年 | 241篇 |
2021年 | 229篇 |
2020年 | 173篇 |
2019年 | 168篇 |
2018年 | 172篇 |
2017年 | 136篇 |
2016年 | 206篇 |
2015年 | 148篇 |
2014年 | 216篇 |
2013年 | 376篇 |
2012年 | 307篇 |
2011年 | 301篇 |
2010年 | 237篇 |
2009年 | 192篇 |
2008年 | 210篇 |
2007年 | 182篇 |
2006年 | 141篇 |
2005年 | 75篇 |
2004年 | 99篇 |
2003年 | 58篇 |
2002年 | 58篇 |
2001年 | 34篇 |
2000年 | 28篇 |
1999年 | 31篇 |
1998年 | 20篇 |
1997年 | 29篇 |
1996年 | 26篇 |
1995年 | 14篇 |
1994年 | 26篇 |
1993年 | 20篇 |
1992年 | 19篇 |
1991年 | 12篇 |
1990年 | 21篇 |
1989年 | 13篇 |
1988年 | 15篇 |
1987年 | 16篇 |
1985年 | 23篇 |
1984年 | 23篇 |
1983年 | 15篇 |
1982年 | 20篇 |
1981年 | 13篇 |
1980年 | 38篇 |
1979年 | 11篇 |
1978年 | 10篇 |
1977年 | 16篇 |
1976年 | 10篇 |
1973年 | 11篇 |
1969年 | 9篇 |
排序方式: 共有4566条查询结果,搜索用时 15 毫秒
71.
Mohd Imran Anis Ahmad Chaudhary Shahzad Ahmed Md. Mottahir Alam Afzal Khan Nasser Zouli Jabir Hakami Hassan Ahmad Rudayni Salah-Ud-Din Khan 《Molecules (Basel, Switzerland)》2022,27(22)
Iron oxide nanoparticle (ION)-based ferro-nanofluids (FNs) have been used for different technological applications owing to their excellent magneto-rheological properties. A comprehensive overview of the current advancement of FNs based on IONs for various engineering applications is unquestionably necessary. Hence, in this review article, various important advanced technological applications of ION-based FNs concerning different engineering fields are critically summarized. The chemical engineering applications are mainly focused on mass transfer processes. Similarly, the electrical and electronics engineering applications are mainly focused on magnetic field sensors, FN-based temperature sensors and tilt sensors, microelectromechanical systems (MEMS) and on-chip components, actuators, and cooling for electronic devices and photovoltaic thermal systems. On the other hand, environmental engineering applications encompass water and air purification. Moreover, mechanical engineering or magneto-rheological applications include dampers and sealings. This review article provides up-to-date information related to the technological advancements and emerging trends in ION-based FN research concerning various engineering fields, as well as discusses the challenges and future perspectives. 相似文献
72.
Muhammad Imran Tousif Mamona Nazir Muhammad Saleem Saba Tauseef Nusrat Shafiq Laiba Hassan Hidayat Hussian Domenico Montesano Daniele Naviglio Gokhan Zengin Ishtiaq Ahmad 《Molecules (Basel, Switzerland)》2022,27(20)
Psidium guajava L. (guava) is a small tree known for its fruit flavor that is cultivated almost around the globe in tropical areas. Its fruit is amazingly rich in antioxidants, vitamin C, potassium, and dietary fiber. In different parts of the world, this plant holds a special place with respect to fruit and nutritional items. Pharmacological research has shown that this plant has more potential than just a fruit source; it also has beneficial effects against a variety of chronic diseases due to its rich nutritional and phytochemical profile. The primary goal of this document is to provide an updated overview of Psidium guajava L. and its bioactive secondary metabolites, as well as their availability for further study, with a focus on the health benefits and potential industrial applications. There have been several studies conducted on Psidium guajava L. in relation to its use in the pharmaceutical industry. However, its clinical efficacy and applications are still debatable. Therefore, in this review a detailed study with respect to phytochemistry of the plant through modern instruments such as GC and LC-MS has been discussed. The biological activities of secondary metabolites isolated from this plant have been extensively discussed. In order to perform long-term clinical trials to learn more about their effectiveness as drugs and applications for various health benefits, a structure activity relationship has been established. Based on the literature, it is concluded that this plant has a wide variety of biopharmaceutical applications. As a whole, this article calls for long-term clinical trials to obtain a greater understanding of how it can be used to treat different diseases. 相似文献
73.
74.
Abdulrab Ahmed M. Alkhanjaf Md Tanwir Athar Zabih Ullah Abdullah Mohammed H. Alsayhab Ahmad Umar Ibrahim Ahmed Shaikh 《Molecules (Basel, Switzerland)》2022,27(23)
Doxorubicin (DOXO) is an antineoplastic drug that is used extensively in managing multiple cancer types. However, DOXO-induced cardiotoxicity is a limiting factor for its widespread use and considerably affects patients’ quality of life. Farnesol (FSN) is a sesquiterpene with antioxidant, anti-inflammatory, and anti-tumor properties. Thus, the current study explored the cardioprotective effect of FSN against DOXO-induced cardiotoxicity. In this study, male Wistar rats were randomly divided into five groups (n = 7) and treated for 14 days. Group I (Control): normal saline, p.o. daily for 14 days; Group II (TOXIC): DOXO 2.4 mg/kg, i.p, thrice weekly for 14 days; Group III: FSN 100 mg/kg, p.o. daily for 14 days + DOXO similar to Group II; Group IV: FSN 200 mg/kg, p.o. daily for 14 days + DOXO similar to Group II; Group V (Standard): nifedipine 10 mg/kg, p.o. daily for 14 days + DOXO similar to Group II. At the end of the study, animals were weighed, blood was collected, and heart-weight was measured. The cardiac tissue was used to estimate biochemical markers and for histopathological studies. The observed results revealed that the FSN-treated group rats showed decrease in heart weight and heart weight/body weight ratio, reversed the oxidative stress, cardiac-specific injury markers, proinflammatory and proapoptotic markers and histopathological aberrations towards normal, and showed cardioprotection. In summary, the FSN reduces cardiac injuries caused by DOXO via its antioxidant, anti-inflammatory, and anti-apoptotic potential. However, more detailed mechanism-based studies are needed to bring this drug into clinical use. 相似文献
75.
Aarif Ali Manzoor Ur Rahman Mir Showkat Ahmad Ganie Saima Mushtaq Sarah I. Bukhari Sultan Alshehri Shahzada Mudasir Rashid Tahir Maqbool Mir Muneeb U. Rehman 《Molecules (Basel, Switzerland)》2022,27(23)
Bovine milk is an important food component in the human diet due to its nutrient-rich metabolites. However, bovine subclinical mastitis alters the composition and quality of milk. In present study, California mastitis testing, somatic cell count, pH, and electrical conductivity were used as confirmatory tests to detect subclinical mastitis. The primary goal was to study metabolome and identify major pathogens in cows with subclinical mastitis. In this study, 29 metabolites were detected in milk using gas chromatography–mass spectrometry. Volatile acidic compounds, such as hexanoic acid, hexadecanoic acid, lauric acid, octanoic acid, n-decanoic acid, tricosanoic acid, tetradecanoic acid, and hypogeic acid were found in milk samples, and these impart good flavor to the milk. Metaboanalyst tool was used for metabolic pathway analysis and principal component estimation. In this study, EC and pH values in milk were significantly increased (p < 0.0001), whereas fat (p < 0.04) and protein (p < 0.0002) significantly decreased in animals with subclinical mastitis in comparison to healthy animals. Staphylococcus aureus was the predominant pathogen found (n = 54), followed by Escherichia coli (n = 30). Furthermore, antibiotic sensitivity revealed that Staphylococcus aureus was more sensitive to gentamicin (79.6%), whereas Escherichia coli showed more sensitivity to doxycycline hydrochloride (80%). 相似文献
76.
Maria Dalla Pozza Ahmad Abdullrahman Christine J. Cardin Gilles Gasser James P. Hall 《Chemical science》2022,13(35):10193
DNA is a strikingly flexible molecule and can form a variety of secondary structures, including the triple helix, which is the subject of this review. The DNA triplex may be formed naturally, during homologous recombination, or can be formed by the introduction of a synthetic triplex forming oligonucleotide (TFO) to a DNA duplex. As the TFO will bind to the duplex with sequence specificity, there is significant interest in developing TFOs with potential therapeutic applications, including using TFOs as a delivery mechanism for compounds able to modify or damage DNA. However, to combine triplexes with functionalised compounds, a full understanding of triplex structure and chemical modification strategies, which may increase triplex stability or in vivo degradation, is essential – these areas will be discussed in this review. Ruthenium polypyridyl complexes, which are able to photooxidise DNA and act as luminescent DNA probes, may serve as a suitable photophysical payload for a TFO system and the developments in this area in the context of DNA triplexes will also be reviewed.Triplex-forming oligonucleotides can target specific DNA sequences by binding in the duplex major groove. Chemical modifications and ligand binding have been explored, for use in a variety of biological applications. 相似文献
77.
Nilofar Mustafa Naveed Iqbal Raja Noshin Ilyas Fozia Abasi Muhammad Sheeraz Ahmad Maria Ehsan Asma Mehak Imran Badshah Jarosaw Prokw 《Molecules (Basel, Switzerland)》2022,27(15)
Agriculture is the backbone of every developing country. Among various crops, wheat (Triticum aestivum L.) belongs to the family Poaceae and is the most important staple food crop of various countries. Different biotic (viruses, bacteria and fungi) and abiotic stresses (water logging, drought and salinity) adversely affect the qualitative and quantitative attributes of wheat. Among these stresses, salinity stress is a very important limiting factor affecting the morphological, physiological, biochemical attributes and grain yield of wheat. This research work was carried out to evaluate the influence of phytosynthesized TiO2 NPs on the germination, physiochemical, and yield attributes of wheat varieties in response to salinity. TiO2 NPs were synthesized using TiO2 salt and a Buddleja asiatica plant extract as a reducing and capping agent. Various concentrations of TiO2 nanoparticles (20, 40, 60 and 80 mg/L) and salt solutions (NaCl) (100 and 150 mM) were used. A total of 20 mg/L and 40 mg/L improve germination attributes, osmotic and water potential, carotenoid, total phenolic, and flavonoid content, soluble sugar and proteins, proline and amino acid content, superoxide dismutase activity, and reduce malondialdhehyde (MDA) content at both levels of salinity. These two concentrations also improved the yield attributes of wheat varieties at both salinity levels. The best results were observed at 40 mg/L of TiO2 NPs at both salinity levels. However, the highest concentrations (60 and 80 mg/L) of TiO2 NPs showed negative effects on germination, physiochemical and yield characteristics and causes stress in both wheat varieties under control irrigation conditions and salinity stress. Therefore, in conclusion, the findings of this research are that the foliar application of TiO2 NPs can help to improve tolerance against salinity stress in plants. 相似文献
78.
79.
Maysa A. Mobasher Marwa T. Hassen Rasha A. Ebiya Norah A. Alturki Ahmad Alzamami Hanaa K. Mohamed Nabil S. Awad Dina Khodeer Bosy A. Abd El-Motelp 《Molecules (Basel, Switzerland)》2023,28(1)
Premature ovarian failure (POF) is described as a loss of oocytes and the absence of folliculogenesis and is considered an adverse effect of chemotherapeutic drugs, which leads to infertility. Subsequently, the existing inquiry was achieved by exploring the potential suspicious influences of lemon peel extract (LPE), and resveratrol (RES) on cyclophosphamide (CPA) induced-POF. The results showed that CPA-induced POF significantly decreased serum estradiol (E2) and progesterone levels, along with a considerable rise in serum luteinizing hormone (LH) and follicle-stimulating hormone (FSH) levels. Moreover, CPA administration to rats significantly increased the serum level of Malondialdehyde (MDA) and significantly lowered the levels of reduced glutathione (GSH) and superoxide dismutase (SOD); in addition, it increased nuclear factor kappa B (NF-κB) levels, tumor necrosis factor-α (TNF-α), as well as cyclooxygenase 2 (COX-2) with the spread expression of inducible nitric oxide synthase (iNOS) mRNA levels and caspase-3 (Casp3) levels in ovarian tissues versus the control rats. However, treatment with LPE and RES suppressed the triggering of NF- κB pathways, evidenced by a considerable reduction in Casp3 & iNOS mRNA expression level and significant ameliorative effects in all evaluated parameters, as confirmed by the histological and immunohistochemical investigation when comparing the model group. In overall findings, both lemon peel extract and resveratrol can mitigate the adverse effects of CPA-induced POF. Most crucially, its combination therapy is a promising pharmacological agent for this disease. 相似文献
80.
Khalid M. Abed Adeeb Hayyan Amal A. M. Elgharbawy Hanee F. Hizaddin Mohd Ali Hashim Hassimi Abu Hasan Mahar Diana Hamid Fathiah M. Zuki Jehad Saleh Ahmad GH Aldaihani 《Molecules (Basel, Switzerland)》2022,27(24)
This study concerns the role of activated carbon (AC) from palm raceme as a support material for the enhancement of lipase-catalyzed reactions in an aqueous solution, with deep eutectic solvent (DES) as a co-solvent. The effects of carbonization temperature, impregnation ratio, and carbonization time on lipase activity were studied. The activities of Amano lipase from Burkholderia cepacia (AML) and lipase from the porcine pancreas (PPL) were used to investigate the optimum conditions for AC preparation. The results showed that AC has more interaction with PPL and effectively provides greater enzymatic activity compared with AML. The optimum treatment conditions of AC samples that yield the highest enzymatic activity were 0.5 (NaOH (g)/palm raceme (g)), 150 min, and a carbonization temperature of 400 °C. DES was prepared from alanine/sodium hydroxide and used with AC for the further enhancement of enzymatic activity. Kinetic studies demonstrated that the activity of PPL was enhanced with the immobilization of AC in a DES medium. 相似文献