全文获取类型
收费全文 | 55632篇 |
免费 | 11863篇 |
国内免费 | 9564篇 |
专业分类
化学 | 38619篇 |
晶体学 | 712篇 |
力学 | 2803篇 |
综合类 | 115篇 |
数学 | 5143篇 |
物理学 | 29667篇 |
出版年
2024年 | 75篇 |
2023年 | 1472篇 |
2022年 | 1712篇 |
2021年 | 1939篇 |
2020年 | 2239篇 |
2019年 | 1575篇 |
2018年 | 2088篇 |
2017年 | 2126篇 |
2016年 | 2490篇 |
2015年 | 2908篇 |
2014年 | 3647篇 |
2013年 | 4417篇 |
2012年 | 5414篇 |
2011年 | 5295篇 |
2010年 | 4214篇 |
2009年 | 4334篇 |
2008年 | 3978篇 |
2007年 | 4357篇 |
2006年 | 4333篇 |
2005年 | 3042篇 |
2004年 | 2554篇 |
2003年 | 1991篇 |
2002年 | 1776篇 |
2001年 | 1755篇 |
2000年 | 1368篇 |
1999年 | 1426篇 |
1998年 | 1068篇 |
1997年 | 838篇 |
1996年 | 576篇 |
1995年 | 492篇 |
1994年 | 344篇 |
1993年 | 220篇 |
1992年 | 199篇 |
1991年 | 186篇 |
1990年 | 149篇 |
1989年 | 144篇 |
1988年 | 117篇 |
1987年 | 27篇 |
1986年 | 21篇 |
1985年 | 41篇 |
1984年 | 17篇 |
1983年 | 11篇 |
1982年 | 14篇 |
1981年 | 21篇 |
1980年 | 9篇 |
1979年 | 12篇 |
1976年 | 7篇 |
1971年 | 12篇 |
1959年 | 1篇 |
1957年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 122 毫秒
1.
以氧化石墨烯(GO)为原料, 利用温和方法制备了3种不同还原程度的部分还原氧化石墨烯pRGO1, pRGO2和pRGO3(pRGO1—3); 利用傅里叶变换红外光谱(FTIR)、 拉曼光谱(Raman)、 X 射线光电子能谱(XPS)、 紫外-可见光谱(UV-Vis)、 透射电子显微镜(TEM)和 EDS能谱对其结构和形貌进行了表征. 细胞实验结果表明, 无激光照射下pRGO1—3本身的细胞毒性较低; 近红外(NIR)激光照射下pRGO1—3通过光热和光毒性双重作用杀伤肿瘤细胞. 实验结果显示了pRGO 在肿瘤光热疗法和光动力疗法领域的应用潜力. 相似文献
2.
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
3.
High Energy Chemistry - Modification of Polyvinylidene fluoride (PVDF) by radiation grafting is a research hotspot in recent years. In this study, the monomer 2-Hydroxyethyl methacrylate (HEMA) was... 相似文献
4.
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
5.
7.
Xiangwen Kong Fang Yu Shengtong Niu Fan Gong Shuang Yang Jinggong Liu Benlong Luo Xinqiang Fang 《中国化学快报》2022,33(6):2997-3002
Copper-catalyzed divergent annulations between α-diketones and alkynyl α-diketones have been achieved, delivering a series of highly functionalized and biologically important cis-hexahydro-2Hcyclopenta[b]furan(HCPF) and 2-hydroxydihydrofuran-3(2H)-one(HDFO) products with high levels of stereoselectivity under identical conditions. The protocol features the use of earth-abundant copper catalyst, mild conditions, shortening synthetic routes in constructing different molecular frameworks, and reduc... 相似文献
8.
Wei Yuting Wang Qihua Liu Wei 《Annals of the Institute of Statistical Mathematics》2021,73(3):535-553
Annals of the Institute of Statistical Mathematics - In this paper, a model averaging approach is developed for the linear regression models with response missing at random. It is shown that the... 相似文献
9.
Safaei Bezgabadi A. Zarandi M. Borhani Bolorizadeh M. A. 《Optical and Quantum Electronics》2021,53(3):1-20
Optical and Quantum Electronics - Classification of hyperspectral image (HSI) is widely used for the study of remotely sensed images. Convolutional Neural Networks (CNNs) are one of the most... 相似文献
10.
We experimentally analyze the heat capacity and thermal expansion of reference solids in a wide temperature range from several Kelvin to melting temperature,and establish a universal double-linear relation between the experimental heat capacity Cp and thermal expansion β,which is different from the previous models.The universal behavior between heat capacity and thermal expansion is important to predict the thermodynamic parameters at constant pressure,and is helpful for understanding the nature of thermal properties in solids. 相似文献