全文获取类型
收费全文 | 987篇 |
免费 | 69篇 |
国内免费 | 18篇 |
专业分类
化学 | 850篇 |
晶体学 | 7篇 |
力学 | 15篇 |
数学 | 64篇 |
物理学 | 138篇 |
出版年
2023年 | 13篇 |
2022年 | 43篇 |
2021年 | 38篇 |
2020年 | 56篇 |
2019年 | 63篇 |
2018年 | 78篇 |
2017年 | 62篇 |
2016年 | 72篇 |
2015年 | 52篇 |
2014年 | 68篇 |
2013年 | 117篇 |
2012年 | 86篇 |
2011年 | 80篇 |
2010年 | 53篇 |
2009年 | 44篇 |
2008年 | 31篇 |
2007年 | 17篇 |
2006年 | 15篇 |
2005年 | 15篇 |
2004年 | 7篇 |
2003年 | 9篇 |
2002年 | 8篇 |
2001年 | 2篇 |
1999年 | 1篇 |
1998年 | 3篇 |
1997年 | 2篇 |
1996年 | 1篇 |
1995年 | 3篇 |
1992年 | 3篇 |
1990年 | 1篇 |
1988年 | 1篇 |
1985年 | 5篇 |
1984年 | 3篇 |
1983年 | 1篇 |
1982年 | 4篇 |
1981年 | 2篇 |
1980年 | 3篇 |
1979年 | 2篇 |
1977年 | 4篇 |
1976年 | 1篇 |
1975年 | 2篇 |
1974年 | 2篇 |
1973年 | 1篇 |
排序方式: 共有1074条查询结果,搜索用时 15 毫秒
971.
Mohammad Dinari Mohamad Mohsen Momeni Zahra Bozorgmehr Shiva Karimi 《Journal of the Iranian Chemical Society》2017,14(3):695-701
Layered double hydroxide (LDH)-based photocatalysts have emerged as a very promising candidate to replace TiO2, owing to their unique layered structure, tunable band gaps, low cost, ease of scale-up, and good photocatalytic activity. Bismuth-doped ZnCr-LDH was studied as photocatalyst in the photodegradation of methylene blue (MB). The structure and morphology of ZnCr-LDH and ZnCrBi-LDH were characterized using a different mode of delegated tools, e.g., FTIR, XRD, UV–Vis, FESEM–EDX, and TEM measurements. FESEM and TEM image of the synthesized LDHs showed that the synthesized LDH is smooth overlapping crystals, and they are approximately in hexagonal form. The material was found to be a good photocatalyst for degradation of methylene blue in visible light, and the results showed that the photocatalytic activity of ZnCrBi-LDH sample is higher than of ZnCr-LDH sample. According to the kinetic data, the reaction rate constant of ZnCrBi-LDH is approximately four times higher than the apparent reaction rate constant of ZnCr-LDH. The catalytic activity was retained even after four methylene blue degradation cycles, indicating that the LDH could be an important addition to the field of wastewater treatment. 相似文献
972.
Somayeh Tajik Hadi Beitollahi Zahra Dourandish Peyman Mohammadzadeh Jahani Iran Sheikhshoaie Mohammad Bagher Askari Parisa Salarizadeh Fariba Garkani Nejad Dokyoon Kim Soo Young Kim Rajender S. Varma Mohammadreza Shokouhimehr 《Electroanalysis》2022,34(7):1065-1091
Non-precious transition metal oxide nanomaterials offer numerous opportunities for various cost-effective electrochemical applications. This review article features the design and advancement of such nanomaterials with unique features applied for the fabrication of electrochemical devices. Also, it discusses various new syntheses of transition metal oxide nanoparticles (TMO NPs) via multiple chemicophysical and biological procedures. Further, the novel appliances of the TMO NPs with varying sizes and morphologies are appraised. The advantages and challenges of a number of investigations on the TMO NPs towards electrochemical applications are addressed with their standpoint of cost-effectiveness, applicability, and the efficiency of the introduced nanostructures for the industrial applications. 相似文献
973.
Direct-dynamics canonical variational transition-state theory (CVT) and quasi-classical trajectory (QCT) calculations have been performed to study the dynamics of the initiation steps in the methanol combustion at high oxygen concentration. The initiation steps in combustion of methanol is hydrogen abstraction from carbon or oxygen in methanol to produce hydroxymethyl radical (CH2OH) or methoxy radical (CH3O), respectively, and hydroperoxyl radical (HO2). A new analytical potential energy function driven from our DFT calculations is constructed to study the dynamics of the title reactions. Reactive cross sections and reaction probabilities at various relative translational energies and initial vibrational and rotational reactant excitation were obtained to calculate the rate constants. The calculated rate constants from CVT and QCT calculations are compared. 相似文献
974.
Nosrat Ollah Mahmoodi Seyedeh Zahra Dalil Heirati Kamel Ekhlasi-Kazaj 《Journal of the Iranian Chemical Society》2012,9(4):521-528
Sodium peroxydisulfate was used as the oxidant for Baeyer?CVilliger oxidation of a variety of cyclic and acyclic ketones at room temperature in the presence of Silica-supported aluminum chloride (silica-AlCl3) as catalyst. The catalyst was prepared by a simple procedure, which exhibited high catalytic activity for the Baeyer?CVilliger oxidation of ketones using environmental friendly sodium peroxydisulfate as oxidizing agent. 相似文献
975.
Zahra Mohammadi Sheng-Xue Xie Edward Peltier Masoumeh Veisi Cory Berkland 《European Polymer Journal》2011,(7):1485-1488
Iron overload is a critical clinical condition that can be controlled by diet and the use of iron-specific chelating agents. An effective oral formulation of an iron chelator should be nontoxic and selective toward iron while maintaining high affinity for iron. In this study, hydrogels containing 2,3 dihydroxybenzoic acid (2,3 DHBA), a portion of the metal chelating domain of enterobactin, were synthesized as a potential non-absorbed chelator for iron in the gastrointestinal tract. A series of polymeric chelators with various hydrogel:DHBA ratios were prepared. The iron-binding properties of the hydrogels were found to depend on the concentration of 2,3 DHBA groups on polymer chains. A 0.005 ratio of PAAm:DHBA was found to have an optimum affinity (log K = 27.01), selectivity, and high binding capacity for Fe(III). 相似文献
976.
Farhad Hosseinzadeh Lotfi Mohsen Rostamy-Malkhalifeh Nazila Aghayi Zahra Ghelej Beigi Kobra Gholami 《Applied Mathematical Modelling》2013,37(1-2):25-33
Scoring rules are an important disputable subject in data envelopment analysis (DEA). Various organizations use voting systems whose main object is to rank alternatives. In these methods, the ranks of alternatives are obtained by their associated weights. The method for determining the ranks of alternatives by their weights is an important issue. This problem has been the subject at hand of some authors. We suggest a three-stage method for the ranking of alternatives. In the first stage, the rank position of each alternative is computed based on the best and worst weights in the optimistic and pessimistic cases, respectively. The vector of weights obtained in the first stage is not a singleton. Hence, to deal with this problem, a secondary goal is used in the second stage. In the third stage of our method, the ranks of the alternatives approach the optimistic or pessimistic case. It is mentionable that the model proposed in the third stage is a multi-criteria decision making (MCDM) model and there are several methods for solving it; we use the weighted sum method in this paper. The model is solved by mixed integer programming. Also, we obtain an interval for the rank of each alternative. We present two models on the basis of the average of ranks in the optimistic and pessimistic cases. The aim of these models is to compute the rank by common weights. 相似文献
977.
Zahra Hassani Mohammad Reza Islami Arman Moradi Moazameh Yazdi Rouh-Alamini 《Phosphorus, sulfur, and silicon and the related elements》2013,188(3):568-577
Stabilized phosphorus ylides were obtained from the three-component reaction between dialkyl acetylenedicarboxylate and sulfur compounds such as pyridine-2-thione, 2-furylmethanethiol, ethanedithioamide, and N-phenyl-1,2,4-triazole-3-thiol in the presence of triphenylphosphine in excellent yields. 相似文献
978.
Mehdi Shafiee Ardestani Ali Jabbari Arabzadeh Zahra Heidari Amirreza Hosseinzadeh Hamidreza Ebrahimi Elham Hashemi Mona Mosayebnia Mohammad Shafiee-Alavidjeh Abbas Alavi Mohammad Hossein Babaei Arman Rahmim Seyed Esmaeil Sadat Ebrahimi Massoud Amanlou 《Journal of Radioanalytical and Nuclear Chemistry》2010,283(2):447-455
DTPA is a very strong metal chelator widely utilized in radiopharmaceutical chemistry for conjugation of chemicals which do not have enough potency for direct metalo-labeling and also to manage toxic radioactive materials such as plutonium, americium, and curium. It is difficult to conjugate DTPA to an amine group in a singular direction and such reactions usually also coincidently produce a mixture of DTPA-bis-amides and DTPA-mono-amide resulting in considerable insufficiencies/difficulties in synthesis and especially yield/separation procedures. In this paper, novel methods for the exclusive synthesis of DTPA-mono-amide have been established which extensively reduce the difficulties otherwise encountered and increase the reaction’s yield considering the green chemistry approaches. This is expected to be of interest to radiopharmaceutical researchers interested in the DTPA (Radio)-metallic-conjugate. Overall, this paper provides a framework to achieve a higher degree of propriety from DTPA as a chelator to conjugate to the chemical compounds. 相似文献
979.
980.
In this paper we first introduce the famous Klein tization approach and taking the negative modes into account densities could be achieved without confronting any paradox. paradox. Afterwards by proposing the Krein quan- , we will show that the expected and exact current 相似文献