全文获取类型
收费全文 | 11526篇 |
免费 | 620篇 |
国内免费 | 205篇 |
专业分类
化学 | 8556篇 |
晶体学 | 66篇 |
力学 | 675篇 |
数学 | 1335篇 |
物理学 | 1719篇 |
出版年
2023年 | 82篇 |
2022年 | 191篇 |
2021年 | 454篇 |
2020年 | 543篇 |
2019年 | 581篇 |
2018年 | 634篇 |
2017年 | 522篇 |
2016年 | 802篇 |
2015年 | 569篇 |
2014年 | 753篇 |
2013年 | 1362篇 |
2012年 | 1004篇 |
2011年 | 883篇 |
2010年 | 610篇 |
2009年 | 560篇 |
2008年 | 566篇 |
2007年 | 448篇 |
2006年 | 312篇 |
2005年 | 265篇 |
2004年 | 204篇 |
2003年 | 178篇 |
2002年 | 132篇 |
2001年 | 48篇 |
2000年 | 40篇 |
1999年 | 36篇 |
1998年 | 38篇 |
1997年 | 32篇 |
1996年 | 34篇 |
1995年 | 24篇 |
1994年 | 30篇 |
1993年 | 25篇 |
1992年 | 23篇 |
1991年 | 21篇 |
1990年 | 22篇 |
1989年 | 24篇 |
1988年 | 21篇 |
1987年 | 25篇 |
1986年 | 11篇 |
1985年 | 29篇 |
1984年 | 30篇 |
1983年 | 15篇 |
1982年 | 28篇 |
1981年 | 11篇 |
1980年 | 19篇 |
1979年 | 14篇 |
1978年 | 15篇 |
1977年 | 13篇 |
1976年 | 11篇 |
1975年 | 13篇 |
1973年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Soltani Rad Mohammad Navid Behrouz Somayeh Mohammad-Javadi Mehdi Zarenezhad Elham 《Molecular diversity》2022,26(5):2503-2521
Molecular Diversity - The preparation, characterization and application of hydroxyapatite silica propyl bis aminoethoxy ethane cuprous complex (HASPBAEECC) as a novel hybrid nano-catalyst for... 相似文献
2.
Walvekar Rashmi Zairin Danial Aminin Khalid Mohammad Mubarak Nabisab Mujawar TCSM Gupta 《Journal of Thermal Analysis and Calorimetry》2022,147(13):7193-7201
Journal of Thermal Analysis and Calorimetry - This study aims to investigate the thermal conductivity, viscosity and thermal degradation of naphthenic-based mineral oil, palm oil methyl ester... 相似文献
3.
Mohammad A. Khalilzadeh Soo Young Kim Ho Won Jang Rafael Luque Rajender S. Varma Richard A. Venditti Mohammadreza Shokouhimehr 《Materials Today Chemistry》2022
The requirement of green and sustainable materials to prepare heterogeneous catalysts has intensified for practical reasons over the past few decades. Carbohydrates are possibly the most plentiful and renewable organic materials in nature with inimitable physiochemical properties, plausible low-cost and large-scale production, and sustainability features could be exploited in the generation of nanostructured heterogeneous catalysts. This review article outlines the organic transformations catalyzed by diverse carbohydrate-based nanostructured catalysts in greener and environmentally friendly processes. Selected examples are highlighted for a variety of organic reactions exploiting the proposed catalysts’ reactivity and reusability, and interactions with the intrinsic nature of the applied carbohydrate supports; advantages and speculated challenges of the introduced catalysts are deliberated as well. 相似文献
4.
5.
Nonlinear Dynamics - The study proposed a feedforward– feedback combined architecture to control a piezoelectric motion system with rate-dependent hysteresis nonlinearities. First, the... 相似文献
6.
Mohammad Javad TAGHIZADEH Maryam Saleh MOHAMMADNIA Masoumeh GHALKHANI Esmail SOHOULI 《高等学校化学研究》2022,38(2):546-551
Azaperone, with anti-anxiety and anti-aggressive activities used in veterinary medicine, is a member of the butyrophenone class. It is ordinarily utilized for a wide range of indications, such as sedation, obstetrics, and anesthesia. In this research, an improved synthetic route is presented for azaperone using a phase-transfer catalyst(PTC). In general, it was synthesized as a dopamine antagonist in four steps. The bis(2-chloroethyl) amine intermediate is easily obtained after the conversion of the alcohol groups into the chloride leaving group using thionyl chloride(95% yields). The alkylation of commercially available 2-amino pyridine in the presence of PTC was then carried out, giving 1-(pyridin-2-yl) piperazine with 75% yield. 1-(Pyridin-2-yl) piperazine was finally alkylated using 4-chloro-1-(4-fluorophenyl) butan-1-one to achieve azaperone with 60% yield. The butyrophenone intermediate was obtained via the Friedel-Crafts reaction of fluorobenzene with 4-chlorobutyryl chloride in the presence of AlCl3. High efficiency, gentle reaction conditions, and fast and simple procedure are the advantages of this method. Also, the electrochemical oxidation behaviour of azaperone was investigated using cyclic and differential pulse voltammetry techniques. Cyclic voltammetric studies indicated an irreversible process for azaperone electro-oxidation with a peak potential of 0.78 V in a phosphate buffer solution(pH=7.0) vs. Ag/AgCl(saturated KCl) electrode. The value of the peak current vs. the azaperone concentration was enhanced linearly in the range of 10―70 μmol/L, and the detection limit was found to be 3.33 μmol/L. 相似文献
7.
Anitha S. Safaei Mohammad Reza Rajeswari S. Pichumani M. 《Journal of Thermal Analysis and Calorimetry》2022,147(12):6941-6957
Journal of Thermal Analysis and Calorimetry - This study focuses on double-tube heat exchanger (DTHE) to numerically examine their thermal performance by considering two types of hybrid nanofluids:... 相似文献
8.
Sateesh K. A. Yaliwal V. S. Soudagar Manzoore Elahi M. Banapurmath N. R. Fayaz H. Safaei Mohammad Reza Elfasakhany Ashraf EL-Seesy Ahmed I. 《Journal of Thermal Analysis and Calorimetry》2022,147(10):5897-5911
Journal of Thermal Analysis and Calorimetry - Various nanofluids (NFs) have been prepared using nanoparticles (NPs) for dual fuel engine application in this present work. In the initial segment of... 相似文献
9.
In this corrigendum, we correct the statement and proof of Lemma 3.2, revise the proofs of Lemma 3.3 and Theorem 3.5, retract Proposition 3.10 and correct several typographical errors. 相似文献
10.
Hamoud Moustafa A. Allan Karam F. Sanad Wafaa A. Saad Ebtissam A. Mahmoud Mamdoh R. 《Journal of Radioanalytical and Nuclear Chemistry》2020,324(2):647-661
Polyacrylonitrile/ferrocyanide composite incorporated with cetrimonium bromide (PFICB) was synthesized and evaluated as a novel bifunctional adsorbent for coremoval of Cs+ and HCrO4?. Results of the reaction time effect showed that adsorption of Cs+ and HCrO4? onto PFICB were rapid processes. The effect of the solution pH in the range 2.5–10 revealed that PFICB had the ability to simultaneously remove Cs+ and HCrO4?. The maximum adsorption capacity of PFICB was found to be 41.79 mg/g for Cs+ and 19.39 mg/g for HCrO4?. These values were compared with those reported in literature using other adsorbents.
相似文献