全文获取类型
收费全文 | 1259篇 |
免费 | 53篇 |
国内免费 | 71篇 |
专业分类
化学 | 531篇 |
晶体学 | 12篇 |
力学 | 24篇 |
综合类 | 2篇 |
数学 | 255篇 |
物理学 | 198篇 |
综合类 | 361篇 |
出版年
2024年 | 2篇 |
2023年 | 16篇 |
2022年 | 40篇 |
2021年 | 32篇 |
2020年 | 37篇 |
2019年 | 41篇 |
2018年 | 41篇 |
2017年 | 45篇 |
2016年 | 44篇 |
2015年 | 40篇 |
2014年 | 61篇 |
2013年 | 86篇 |
2012年 | 77篇 |
2011年 | 79篇 |
2010年 | 62篇 |
2009年 | 55篇 |
2008年 | 81篇 |
2007年 | 59篇 |
2006年 | 68篇 |
2005年 | 44篇 |
2004年 | 45篇 |
2003年 | 33篇 |
2002年 | 22篇 |
2001年 | 28篇 |
2000年 | 27篇 |
1999年 | 25篇 |
1998年 | 18篇 |
1997年 | 11篇 |
1996年 | 16篇 |
1995年 | 25篇 |
1994年 | 23篇 |
1993年 | 11篇 |
1992年 | 10篇 |
1991年 | 19篇 |
1990年 | 10篇 |
1989年 | 10篇 |
1988年 | 9篇 |
1987年 | 5篇 |
1985年 | 6篇 |
1982年 | 2篇 |
1980年 | 2篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1976年 | 3篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1973年 | 3篇 |
1972年 | 1篇 |
1971年 | 1篇 |
1970年 | 1篇 |
排序方式: 共有1383条查询结果,搜索用时 15 毫秒
41.
PPh3‐Catalyzed Ring‐Expansion Reactions of Sulfamate‐Derived Cyclic Imines with Acetylenedicarboxylates
下载免费PDF全文
![点击此处可从《化学:亚洲杂志》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Zhilin Yang Hao Yu Lei Zhang Hang Wei Dr. Yumei Xiao Lanzhen Chen Dr. Hongchao Guo 《化学:亚洲杂志》2014,9(1):313-318
The PPh3‐catalyzed ring‐expansion reaction of sulfamate‐derived cyclic imines with acetylenedicarboxylates has been developed. The reaction works quite efficiently under very mild conditions to afford benzo[g][1,2,3]oxathiazocine‐4,5‐dicarboxylate 2,2‐dioxide derivatives in high yields. 相似文献
42.
Xiaoyan Cui Yujiao Wang Yumei Yan Zilin Meng Runhua Lu Haixiang Gao Canping Pan Xinlin Wei Wenfeng Zhou 《Journal of separation science》2022,45(4):908-918
In this study, a 4-formylphenylboronic acid-modified cross-linked chitosan magnetic nanoparticle (FPBA@CCHS@Fe3O4) was fabricated. The synthesized material was utilized as the magnetic solid-phase extraction adsorbent for the enrichment of six benzoylurea pesticides. In addition to B-N coordination, FPBA@CCHS@Fe3O4 interacts with benzoylureas through hydrogen bonds and π-π stacking interaction on account of rich active groups (amino and hydroxyl) and aromatic rings in structure. Compared to traditional extraction methods, less adsorbent (20 mg) and reduced extraction time (3 min) were achieved. The adsorbent also exhibited good reusability (no less than 10 times). Coupled with a high-performance liquid chromatography–diode array detector, satisfactory recoveries (89.1–103.9%) and an acceptable limit of detection (0.2–0.7 μg/L) were obtained. Under optimized conditions, the established method was successfully applied to the tea infusion samples from six major tea categories with acceptable recoveries ranging from 76.8 to 110%, indicating its application potential for the quantitative detection of pesticides in complex matrices. 相似文献
43.
Thuan Nguyen Ngoc Ngan Nguyen Thi Kuo Ping-Chung Trinh Nguyen Thi Nu Thien Le Trung Mai Dam Sao Tuan Nguyen Ngoc Tan Le Van Thang Tran Dinh 《Chemistry of Natural Compounds》2021,57(6):1104-1106
Chemistry of Natural Compounds - 相似文献
44.
Ghassan Al-Chaar Tuan Hoang Dominick Dowds Kyle Ford Thomas Carlson Charles Marsh 《Journal of Cluster Science》2014,25(2):559-570
This study investigated the emission spectra of select silicon nanoparticles when subjected to various temperature changes. Two sizes of silicon nanoparticles, dispersed in both isopropanol and acetone solvents, were studied. Photoluminescence responses of the samples were measured in an environmental chamber that allowed exposure to temperatures in the range of ?73 to 65 °C (?100 to 150 °F). These silicon nanoparticles exhibited emission dependence on the temperature of their environment. The emission become brighter as the temperature decreased and less intense as the temperature increased. Thus, the response of these silicon nanoparticles in a harsh environment has been qualified. 相似文献
45.
Huynh Phuong Truc Tran Trinh Pham Ngoc Dinh Binh Thanh Nguyen Linh Thi Truc Truong Loan Thi Hong Tran Anh Tuan Ho Dung Manh Van Nguyen Dong 《Journal of Radioanalytical and Nuclear Chemistry》2020,324(2):663-671
Journal of Radioanalytical and Nuclear Chemistry - The aim of this study was to find trace elements that increase risk of breast cancer based on the deviation of the concentration of trace elements... 相似文献
46.
We report design, synthesis and evaluation of a series of naphthalenediimides (NDIs) that are bridged with short peptides. Reminiscent of peptide stapling technologies, the macrocycles are conveniently accessible by a chromogenic nucleophilic aromatic substitution of two bromides in the NDI core with two thiols from cysteine sidechains. The dimension of core‐bridged NDIs matches that of one turn of an α helix. NDI‐stapled peptides exist as two, often separable atropisomers. Introduction of tertiary amine bases in amino‐acid sidechains above the π‐acidic NDI surface affords operational anion‐π catalysts. According to an enolate chemistry benchmark reaction, anion‐π catalysis next to peptides occurs with record chemoselectivity but weak enantioselectivity. Catalytic activity drops with increasing distance of the amine base to the NDI surface, looser homocysteine bridges, mismatched, shortened and elongated α‐helix turns, and acyclic peptide controls. Elongation of isolated turns into short α helices significantly increases activity. This increase is consistent with remote control of anion‐π catalysis from the α‐helix macrodipole. 相似文献
47.
为进行尖晶石LiMn2O4的改性优化,合成了大小为100~400 nm,呈八面体形貌的LiMn2O4尖晶石单晶,并采用XRD、SEMI、CP等方法进行了分析,旨在对该尖晶石单晶的充、放电性能进行表征. 相似文献
48.
采用非培养法和传统培养法相结合,利用Illumina高通量测序技术对江西省九江市彭泽县龙宫洞微生物的16S rDNA和ITS相关区域进行测序及生物信息学分析,通过实时荧光定量PCR(qPCR)对洞穴土壤中细菌和真菌含量进行绝对定量,探究不同季节对洞穴土壤微生物群落结构的影响,同时观察相应可培养微生物分布情况.结果表明:... 相似文献
49.
基于线阵InGaAs光电二极管阵列的光纤光栅传感解调 总被引:1,自引:0,他引:1
采用线阵InGaAs光电二极管阵列和体相位光栅并结合空分复用和波分复用技术,对光纤光栅传感进行解调.设计了基于线阵InGaAs光电二极管阵列和体相位光栅的光纤光栅传感解调系统,通过系统测试和性能分析,该解调系统解调带宽42 nm,信噪比30 dB,波长偏移测量精确度±15 pm,功率测量精确度为±0.3 dB.基于线阵InGaAs光电二极管阵列和体相位光栅的光纤光栅解调系统不但尺寸小,功耗低,而且具有较高的解调速度. 相似文献
50.
该设计解决了低温工程与低温技术等领域所使用的高纯度气体介质换热的要求,具有显著的经济效益和社会效益。其换热器是由四个管壳式热交换器串联组合而成,壳体呈窄矩形,换热管采用U形换热管,四个管壳式热交换器呈方阵置放在低温换热器筒体内。低温换热器采用的材料是0Cr18N i9/304,该种材料的透气性小、耐磨损、抗腐蚀能力强和性能稳定,防止了气体被污染。另外在低温下,考虑了材料的热胀冷缩所产生的应力,使应力能够自行消除,提高了它的密封性能,最终使低温换热器密封性能好,防止了气体被污染,保证了气体的高纯度。 相似文献