全文获取类型
收费全文 | 16741篇 |
免费 | 2958篇 |
国内免费 | 2454篇 |
专业分类
化学 | 13120篇 |
晶体学 | 191篇 |
力学 | 887篇 |
综合类 | 154篇 |
数学 | 2099篇 |
物理学 | 5702篇 |
出版年
2024年 | 35篇 |
2023年 | 228篇 |
2022年 | 499篇 |
2021年 | 496篇 |
2020年 | 600篇 |
2019年 | 625篇 |
2018年 | 523篇 |
2017年 | 549篇 |
2016年 | 765篇 |
2015年 | 894篇 |
2014年 | 1019篇 |
2013年 | 1277篇 |
2012年 | 1561篇 |
2011年 | 1578篇 |
2010年 | 1122篇 |
2009年 | 1099篇 |
2008年 | 1227篇 |
2007年 | 1098篇 |
2006年 | 1001篇 |
2005年 | 873篇 |
2004年 | 769篇 |
2003年 | 546篇 |
2002年 | 627篇 |
2001年 | 478篇 |
2000年 | 402篇 |
1999年 | 326篇 |
1998年 | 283篇 |
1997年 | 266篇 |
1996年 | 225篇 |
1995年 | 188篇 |
1994年 | 182篇 |
1993年 | 151篇 |
1992年 | 119篇 |
1991年 | 106篇 |
1990年 | 106篇 |
1989年 | 61篇 |
1988年 | 66篇 |
1987年 | 47篇 |
1986年 | 29篇 |
1985年 | 38篇 |
1984年 | 16篇 |
1983年 | 13篇 |
1982年 | 8篇 |
1981年 | 9篇 |
1980年 | 3篇 |
1979年 | 2篇 |
1977年 | 3篇 |
1936年 | 7篇 |
1935年 | 1篇 |
1916年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Prathibha Kumari Weiwei Liu Cheng-Jie Wang Jun Dai Mei-Xin Wang Qi-Qiong Yang Yu-Hua Deng Zhihui Shao 《中国化学》2020,38(2):151-157
Summary of main observation and conclusion A Pd-catalyzed asymmetric aromative[4+3]-cyclization reaction of amino-trimethylenemethanes(TMM,1d,ip3-oles)with fused 1-azadienes has been developed.This method enables access to the synthetically importance and biologically active benzofuran fused azepines and indeno-azepines in excellent efficiency and stereoselectivity(up to 95%yield,99%ee,>19:1 dr). 相似文献
992.
The chiral phosphoric acid catalyzed asymmetric[3+2]annulation of substituted 2-vinylindoles with azlactones has been established.This reaction represented a practical approach for the synthesis of structurally diverse pyrrolo[1,2-a]indoles with two vicinal stereocenters including one tetrasubstituted stereocenter in good yields and good stereoselectivities under mild conditions. 相似文献
993.
Yanbin Shen Yahao Li Shengjue Deng Guoxiang Pan Qinqin Xiong Xiaokun Ding Yangfan Lu Qi Liu Xinhui Xia Xiuli Wang Jiangping Tu 《中国化学快报》2020,31(3):846-850
High-perfo rmance anodes of sodium ion batteries(SIBs)largely depends on rational architecture design and binder-free smart hybridization.Herein,we report TiC/C core/shell nanowires arrays prepared by a one-step chemical vapor deposition(CVD)method and apply it as the anode of SIBs for the first time.The conductive TiC core is intimately decorated with carbon shell.The as-obtained TiC/C nanowires are homogeneously grown on the substrate and show core/shell heterostructure and porous architecture with high electronic conductivity and reinforced stability.Owing to these merits,the TiC/C electrode displays good rate performance and outstanding cycling performance with a capacity of 135.3 mAh/g at 0.1 A/g and superior capacity retention of 90.14%after 1000 cycles at 2 A/g.The reported strategy would provide a promising way to construct binder-free arrays electrodes for sodium ion storage. 相似文献
994.
995.
所谓凝聚态,一般意义上是指液态和固态,而凝聚态化学,即是在固相和液相中的各种化学过程。在无机材料,特别是无机纳米与多孔材料的合成制备中,凝聚态化学过程贯穿其中,几乎无处不在。在固相材料合成过程中,通过液相中的各种化学反应以获得目标固体材料的所需组分和物相,也许就是无机材料合成中一个最基本的凝聚态化学问题;而多孔如微孔或介孔材料合成中,更涉及伴随组分和物相形成过程中的孔结构形成与调控;进一步,在制备面向实际应用如催化剂和药物载体时,则在以上的各项要求之外,还必须考虑材料的表面活性位、缺陷等关键因素,以及颗粒尺寸、分散性和形貌等几何和物理特性。本文以无机氧化物为对象,讨论了无机材料在凝聚态化学合成过程中的几个侧面,包括纳米颗粒和粉体的化学合成方法,多孔材料的合成和多孔复相结构的合成调控,以及多级孔结构沸石的合成制备与催化性能,以期能加深对材料合成中凝聚态化学过程的认识,并期待以凝聚态化学为指导,进一步推动无机材料特别是纳米多孔材料合成的发展。 相似文献
996.
由活性层和支撑层组成的薄层复合(TFC)聚酰胺(PA)膜,是目前广泛应用于纳滤、反渗透、正渗透和压力延迟渗透过程中的高性能脱盐膜,具有水通量大和截盐率高等优异性能。然而,由于TFC-PA膜存在活性层疏水性强、支撑层孔径大等特点,致使TFC-PA膜在实际使用过程中极易受到膜污染,制约了TFC-PA膜的进一步推广和使用。本文讨论分析了TFC-PA膜的结构特点和表面性质,总结归纳了在不同膜过程中TFC-PA膜污染形成的原因及特点,详细论述了国内外抗污染TFC-PA膜的研究进展。本文重点介绍了活性层抗污染改性和支撑层抗污染改性方法,并对其抗污染机理以及存在的问题进行了阐述与分析,最后对抗污染TFC-PA膜的结构设计与表面改性策略进行了总结及展望。 相似文献
997.
Qi Wan Yan Deng Yaoqing Huang Zhihui Yu Chunli Wang Ke Wang Assoc. Prof. Jibin Dong Prof. Ying Chen 《ChemistryOpen》2020,9(2):176-182
Fifteen novel furoxan-based nitric oxide (NO) releasing hybrids of estradiol derivatives were synthesized and evaluated in vitro anti-proliferative activity in MDA-MB-231, A2780, Hela and HUVEC cell lines. Most of them displayed potent anti-proliferative effects. Among the compounds, 4-bromo-3-((phenylsulfonyl)-1,2,5-oxadiazole 2-oxide)-oxy-propoxy-estradiol ( 11 b ) exhibited the best activity with IC50 values of 3.58–0.0008 μM. Preliminary pharmacological studies showed that 11 b induced apoptosis and hardly affected the cell cycle of MDA-MB-231 cell line. NO-releasing capacity and inhibition of ERK/MAPK pathway signaling might explain the potent antineoplastic activity of these compounds. The preliminary structure-activity relationship (SAR) showed that steroidal scaffolds with a linker in 3-position were favorable moieties to evidently increase the bioactivities of these hybrids. Overall, these results implied that 11 b merited to be further investigated as a promising anti-cancer candidate. 相似文献
998.
Li Yuanchao Xu Guangri Fan Shumin Ma Jingjing Shi Xiaohui Long Zaixin Deng Wenjie Fan Wenxiu Yang Shuting 《Journal of Solid State Electrochemistry》2020,24(4):821-828
Journal of Solid State Electrochemistry - Synthesis method is crucial to the improved electrochemical performances of LiMnPO4 materials with poor electronic and ionic conductivity for large-scale... 相似文献
999.
Ruixue Chen Hai‐Yan Su Deyu Liu Rui Huang Xianguang Meng Xiaoju Cui Zhong‐Qun Tian Dong H. Zhang Dehui Deng 《Angewandte Chemie (International ed. in English)》2020,59(1):154-160
Conversion of carbon monoxide to high value‐added ethylene with high selectivity by traditional syngas conversion process is challenging because of the limitation of Anderson‐Schulz–Flory distribution. Herein we report a direct electrocatalytic process for highly selective ethylene production from CO reduction with water over Cu catalysts at room temperature and ambient pressure. An unprecedented 52.7 % Faradaic efficiency of ethylene formation is achieved through optimization of cathode structure to facilitate CO diffusion at the surface of the electrode and Cu catalysts to enhance the C?C bond coupling. The highly selective ethylene production is almost without other carbon‐based byproducts (e.g. C1–C4 hydrocarbons and CO2) and avoids the drawbacks of the traditional Fischer–Tropsch process that always delivers undesired products. This study provides a new and promising strategy for highly selective production of ethylene from the abundant industrial CO. 相似文献
1000.
Yuebin Lian Wenjuan Yang Chufeng Zhang Hao Sun Zhao Deng Wenjie Xu Li Song Zhongwen Ouyang Zhenxing Wang Jun Guo Yang Peng 《Angewandte Chemie (International ed. in English)》2020,59(1):286-294
Reversible oxygen conversion is important for various green energy technologies. Herein we synthesize a series of bimetallic coordination polymers by varying the Ni/Co ratio and using HITP (HITP=2,3,6,7,10,11‐hexaiminotriphenylene) as the ligand, to interrogate the role of metal centres in modulating the activity of the oxygen reduction reaction (ORR). Co3HITP2 and Ni3HITP2 are compared. Unpaired 3d electrons in Co3HITP2 result in less coplanarity but more radical character. Thus, despite of a reduced crystallinity and conductivity, the best ORR activity, comparable to 20 % Pt/C, is obtained for Co3HITP2, showing the 3d orbital configuration of the metal centre promotes ORR. Experimental and DFT studies show a transition of ORR pathway from four‐electron for Co3HITP2 to two‐electron for Ni3HITP2. Rechargeable zinc–air batteries using Co3HITP2 as the air cathode catalyst demonstrate excellent energy efficiency and stability. 相似文献