全文获取类型
收费全文 | 32450篇 |
免费 | 4400篇 |
国内免费 | 3815篇 |
专业分类
化学 | 23470篇 |
晶体学 | 462篇 |
力学 | 1611篇 |
综合类 | 298篇 |
数学 | 4204篇 |
物理学 | 10620篇 |
出版年
2024年 | 56篇 |
2023年 | 513篇 |
2022年 | 576篇 |
2021年 | 886篇 |
2020年 | 1095篇 |
2019年 | 1086篇 |
2018年 | 952篇 |
2017年 | 915篇 |
2016年 | 1324篇 |
2015年 | 1326篇 |
2014年 | 1563篇 |
2013年 | 2203篇 |
2012年 | 2669篇 |
2011年 | 2898篇 |
2010年 | 2059篇 |
2009年 | 2039篇 |
2008年 | 2248篇 |
2007年 | 2032篇 |
2006年 | 1812篇 |
2005年 | 1593篇 |
2004年 | 1238篇 |
2003年 | 1033篇 |
2002年 | 1053篇 |
2001年 | 887篇 |
2000年 | 725篇 |
1999年 | 664篇 |
1998年 | 553篇 |
1997年 | 480篇 |
1996年 | 493篇 |
1995年 | 414篇 |
1994年 | 402篇 |
1993年 | 371篇 |
1992年 | 344篇 |
1991年 | 302篇 |
1990年 | 256篇 |
1989年 | 199篇 |
1988年 | 176篇 |
1987年 | 137篇 |
1986年 | 153篇 |
1985年 | 162篇 |
1984年 | 111篇 |
1983年 | 73篇 |
1982年 | 80篇 |
1981年 | 54篇 |
1980年 | 54篇 |
1979年 | 59篇 |
1978年 | 41篇 |
1976年 | 38篇 |
1974年 | 43篇 |
1973年 | 49篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
11.
Yanxia Xu Yanbing Lv Ruili Wu Huaibin Shen Huawei Yang Han Zhang Jinjie Li Lin Song Li 《Particle & Particle Systems Characterization》2020,37(3):1900441
Indium phosphide (InP) quantum dots (QDs) are ideal substitutes for widely used cadmium-based QDs and have great application prospects in biological fields due to their environmentally benign properties and human safety. However, the synthesis of InP core/shell QDs with biocompatibility, high quantum yield (QY), uniform particle size, and high stability is still a challenging subject. Herein, high quality (QY up to 72%) thick shell InP/GaP/ZnS core/shell QDs (12.8 ± 1.4 nm) are synthesized using multiple injections of shell precursor and extension of shell growth time, with GaP serving as the intermediate layer and 1-octanethiol acting as the new S source. The thick shell InP/GaP/ZnS core/shell QDs still keep high QY and photostability after transfer into water. InP/GaP/ZnS core/shell QDs as fluorescence labels to establish QD-based fluorescence-linked immunosorbent assay (QD-FLISA) for quantitative detection of C-reactive protein (CRP), and a calibration curve is established between fluorescence intensity and CRP concentrations (range: 1–800 ng mL−1, correlation coefficient: R2 = 0.9992). The limit of detection is 2.9 ng mL−1, which increases twofold compared to previously reported cadmium-free QD-based immunoassays. Thus, InP/GaP/ZnS core/shell QDs as a great promise fluorescence labeling material, provide a new route for cadmium-free sensitive and specific immunoassays in biomedical fields. 相似文献
12.
Analysis and pharmacokinetic study of polyphyllin H in beagle dog plasma after oral administration of Rhizoma Paridis Extracts by LC‐MS/MS 下载免费PDF全文
13.
以六水氯化镁和六次甲基四胺为原料,采用水热法合成四方体MgO,考察其对有机染料甲基橙和亚甲基蓝的吸附行为.通过TGA-DTA、SEM、XRD、N2-sorption和FT-IR等手段表征样品.结果表明,原料浓度、温度和表面活性剂对四方体MgO结构的形成影响较小,而反应时间的延长有助于有序结构的组装.温度170℃、时间24h、MgCl2·6H2O与C6H12N4浓度比为1∶2和表面活性剂PVP是制备四方体MgO的最佳条件.在溶液浓度10mg · L-1的单一吸附实验过程中,四方体MgO对甲基橙和亚甲基蓝的去除率分别为91.3;和22.3;,吸附过程均为单层吸附且符合Langmuir等温吸附模型和伪二级吸附动力学方程.在溶液浓度40 mg·L-1、甲基橙和亚甲基蓝浓度比3∶1的混合溶液吸附过程中,四方体MgO对甲基橙和亚甲基蓝的去除率分别为80.1;和97.9;. 相似文献
14.
15.
16.
Jie Lu Ju-Kang Wu Yao Jiang Dr. Peng Tan Lin Zhang Yu Lei Prof. Xiao-Qin Liu Prof. Lin-Bing Sun 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(16):6490-6496
Hierarchically porous metal–organic frameworks (HP-MOFs) are promising in various applications. Most reported HP-MOFs are prepared based on the generation of mesopores in microporous frameworks, and the formed mesopores are connected by microporous channels, limiting the accessibility of mesopores for bulky molecules. A hierarchical structure is formed by constructing microporous MOFs in uninterrupted mesoporous tunnels. Using the confined space in as-prepared mesoporous silica, highly dispersed metal precursors for MOFs are coated on the internal surface of mesoporous tunnels. Ligand vapor-induced crystallization is employed to enable quantitative formation of MOFs in situ, in which sublimated ligands diffuse into mesoporous tunnels and react with metal precursors. The obtained hierarchically porous composites exhibit record-high adsorption capacity for the bulky molecule trypsin. The thermal and storage stability of trypsin is improved upon immobilization on the composites. 相似文献
17.
18.
Single Crystal to Single Crystal (SC‐to‐SC) Transformation from a Nonporous to Porous Metal–Organic Framework and Its Application Potential in Gas Adsorption and Suzuki Coupling Reaction through Postmodification 下载免费PDF全文
Dr. Rupam Sen Debraj Saha Dr. Subratanath Koner Dr. Paula Brandão Dr. Zhi Lin 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(15):5962-5971
A new amino‐functionalized strontium–carboxylate‐based metal–organic framework (MOF) has been synthesized that undergoes single crystal to single crystal (SC‐to‐SC) transformation upon desolvation. Both structures have been characterized by single‐crystal X‐ray analysis. The desolvated structure shows an interesting 3D porous structure with pendent ?NH2 groups inside the pore wall, whereas the solvated compound possesses a nonporous structure with DMF molecules on the metal centers. The amino group was postmodified through Schiff base condensation by pyridine‐2‐carboxaldehyde and palladium was anchored on that site. The modified framework has been utilized for the Suzuki cross‐coupling reaction. The compound shows high activity towards the C?C cross‐coupling reaction with good yields and turnover frequencies. Gas adsorption studies showed that the desolvated compound had permanent porosity and was microporous in nature with a BET surface area of 2052 m2 g?1. The material also possesses good CO2 (8 wt %) and H2 (1.87 wt %) adsorption capabilities. 相似文献
19.
20.
A self-propelled object coupled with an enzyme reaction between urease and urea was investigated at the air/aqueous interface. A plastic object that was fixed to a urease-immobilized filter paper was used as a self-propelled object, termed a urease motor, placed on an aqueous urea solution. The driving force of the urease motor is the difference in the surface tension around the object. Oscillatory motion or no motion was triggered depending on the initial pH of the urea solution. Both the frequency and maximum speed of the oscillatory motion varied depending on the initial pH of the water phase. The mechanisms underlying the oscillatory motion and no motion were discussed in relation to the bell-shaped enzyme activity of urease in the enzyme reaction and the surface tension around the urease motor. 相似文献