全文获取类型
收费全文 | 87525篇 |
免费 | 10880篇 |
国内免费 | 8109篇 |
专业分类
化学 | 42741篇 |
晶体学 | 744篇 |
力学 | 3697篇 |
综合类 | 426篇 |
数学 | 6703篇 |
物理学 | 22179篇 |
综合类 | 30024篇 |
出版年
2024年 | 301篇 |
2023年 | 1566篇 |
2022年 | 2742篇 |
2021年 | 2761篇 |
2020年 | 2819篇 |
2019年 | 2589篇 |
2018年 | 2300篇 |
2017年 | 2283篇 |
2016年 | 3222篇 |
2015年 | 3535篇 |
2014年 | 4385篇 |
2013年 | 5356篇 |
2012年 | 6637篇 |
2011年 | 6827篇 |
2010年 | 4824篇 |
2009年 | 4789篇 |
2008年 | 5353篇 |
2007年 | 4950篇 |
2006年 | 4474篇 |
2005年 | 3945篇 |
2004年 | 2960篇 |
2003年 | 2358篇 |
2002年 | 2289篇 |
2001年 | 1971篇 |
2000年 | 1890篇 |
1999年 | 2522篇 |
1998年 | 2125篇 |
1997年 | 2190篇 |
1996年 | 1984篇 |
1995年 | 1766篇 |
1994年 | 1551篇 |
1993年 | 1274篇 |
1992年 | 1166篇 |
1991年 | 1068篇 |
1990年 | 895篇 |
1989年 | 758篇 |
1988年 | 598篇 |
1987年 | 495篇 |
1986年 | 325篇 |
1985年 | 208篇 |
1984年 | 117篇 |
1983年 | 91篇 |
1982年 | 66篇 |
1981年 | 42篇 |
1980年 | 33篇 |
1979年 | 17篇 |
1977年 | 9篇 |
1976年 | 10篇 |
1975年 | 18篇 |
1957年 | 13篇 |
排序方式: 共有10000条查询结果,搜索用时 78 毫秒
1.
Shilin Jiang Dr. Yalan Liu Dr. Lin Wang Prof. Zhifang Chai Prof. Wei-Qun Shi 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(60):e202201145
The coordination chemistry of f-block elements (lanthanide and actinide) in molten salts has become a resounding topic in view of its great importance to the research and development (R&D) of molten salt reactors and pyroprocessing. In this Review article, a general overview of the coordination chemistry of f-block elements in molten salts is provided including past achievements and recent advances. Particular emphases are placed on the oxidation state, speciation, and solution structure of f-block metal ions in molten salts, as well as their relationships with the salt composition. Furthermore, this review briefly discusses the spectroscopic and theoretical methods that complement each other in revealing the coordination properties. 相似文献
2.
Dr. Zaifa Shi Dr. Yihuang Jiang Dr. Jingxiong Yu Prof. Shanjun Chen Prof. Jun Chen Prof. Zichao Tang Prof. Lansun Zheng 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(8):e202103546
At present, the reactivity of cyclic alkanes is estimated by comparison with acyclic hydrocarbons. Due to the difference in the structure of cycloalkanes and acycloalkanes, the thermodynamic data obtained by analogy are not applicable. In this study, a molecular beam sampling vacuum ultraviolet photoionization time-of-flight mass spectrometer (MB-VUV-PI-TOFMS) was applied to study the low-temperature oxidation of cyclopentane (CPT) at a total pressure range from 1–3 atm and low-temperature range between 500 and 800 K. Low-temperature reaction products including cyclic olefins, cyclic ethers, and highly oxygenated intermediates (e. g., ketohydroperoxide KHP, keto-dihydroperoxide KDHP, olefinic hydroperoxides OHP and ketone structure products) were observed. Further investigation of the oxidation of CPT – electronic structure calculations – were carried out at the UCCSD(T)-F12a/aug-cc-pVDZ//B3LYP/6-31+ G(d,p) level to explore the reactivity of O2 molecules adding sequentially to cyclopentyl radicals. Experimental and theoretical observations showed that the dominant product channel in the reaction of CPT radicals with O2 is HO2 elimination yielding cyclopentene. The pathways of second and third O2 addition – the dissociation of hydroperoxide – were further confirmed. The results of this study will develop the low-temperature oxidation mechanism of CPT, which can be used for future research on accurately simulating the combustion process of CPT. 相似文献
3.
Cellulose - In this research, the production of levoglucosan (LG) and levoglucosenone (LGO) was improved from acid-impregnated cellulose via fast pyrolysis. Thermogravimetric and kinetic analysis... 相似文献
4.
Experimental Mechanics - Temperature gradients significantly affect the material fatigue process. A reliable and robust test procedure is needed for quantifying the effects of temperature gradients... 相似文献
5.
Kobayashi M. Zhang Y. Ishikawa H. Sun J. Oddershede J. Juul Jensen D. Miura H. 《Experimental Mechanics》2021,61(5):817-828
Experimental Mechanics - The internal strain distribution developing during plastic deformation is important for understanding the mechanical properties of polycrystalline materials. Such... 相似文献
6.
专业化众创空间是在众创空间基础上发展起来的服务于产业细分领域、高度专业化、重点服务于实体经济的一种新型创新创业服务载体.北京市作为全国科技创新中心,创新创业高度活跃,专业化众创空间不断探索模式创新和服务创新,在服务高精尖产业发展、加快新旧动能转换、促进科技成果转化、盘活科技创新资源等方面发挥了重要作用.文章通过分析北京市专业化众创空间发展的情况和特点,总结提炼了几种典型发展模式,分析了专业化众创空间对首都经济高质量发展的重要意义,同时针对目前北京市专业化众创空间发展存在的主要问题,提出相关对策建议. 相似文献
7.
Jiang Rui-Yang Xin Jia-Wei Cao Cong 《International Journal of Theoretical Physics》2021,60(8):2836-2855
International Journal of Theoretical Physics - Quantum logic gates are the foundation of circuit-based quantum computation and quantum simulation. Multi-qubit quantum controlled gates are of vital... 相似文献
8.
Li Quanxin Li Zheng He Cheng Sun Huilin Tan Shengheng Zhang Hua 《Journal of Radioanalytical and Nuclear Chemistry》2022,331(5):2105-2115
Journal of Radioanalytical and Nuclear Chemistry - The simplified 8-oxide system (SiO2-B2O3-Na2O-Al2O3-CaO-TiO2-MoO3-La2O3) has been prepared under two types of cooling methods, and analyzed with... 相似文献
9.
Hongjin Wang Tengfei Long Hao Zhang Meng Li Qi Sun Xin Zhai Lixin Sun 《Biomedical chromatography : BMC》2022,36(4):e5301
3,4-Difluorobenzyl(1-ethyl-5-(4-((4-hydroxypiperidin-1-yl)-methyl)thiazol-2-yl)-1H-indol-3-yl)carbamate (NAI59), a small molecule with outstanding therapeutic effectiveness to anti-pulmonary fibrosis, was developed as an autotaxin inhibitor candidate compound. To evaluate the pharmacokinetics and plasma protein binding of NAI59, a UPLC–MS/MS method was developed to quantify NAI59 in plasma and phosphate-buffered saline. The calibration curve linearity ranged from 9.95 to 1990.00 ng/mL in plasma. The accuracy was −6.8 to 5.9%, and the intra- and inter-day precision was within 15%. The matrix effect and recovery, as well as dilution integrity, were within the criteria. The chromatographic and mass spectrometric conditions were also feasible to determine phosphate-buffered saline samples, and it has been proved that this method exhibits good precision and accuracy in the range of 9.95–497.50 ng/mL in phosphate-buffered saline. This study is the first to determine the pharmacokinetics, absolute bioavailability, and plasma protein binding of NAI59 in rats using this established method. Therefore, the pharmacokinetic profiles of NAI59 showed a dose-dependent relationship after oral administration, and the absolute bioavailability in rats was 6.3%. In addition, the results of protein binding showed that the combining capacity of NAI59 with plasma protein attained 90% and increased with the increase in drug concentration. 相似文献
10.