全文获取类型
收费全文 | 4354篇 |
免费 | 763篇 |
国内免费 | 620篇 |
专业分类
化学 | 2525篇 |
晶体学 | 39篇 |
力学 | 150篇 |
综合类 | 31篇 |
数学 | 405篇 |
物理学 | 1305篇 |
无线电 | 1282篇 |
出版年
2024年 | 30篇 |
2023年 | 142篇 |
2022年 | 184篇 |
2021年 | 205篇 |
2020年 | 208篇 |
2019年 | 209篇 |
2018年 | 175篇 |
2017年 | 163篇 |
2016年 | 221篇 |
2015年 | 266篇 |
2014年 | 270篇 |
2013年 | 325篇 |
2012年 | 392篇 |
2011年 | 399篇 |
2010年 | 296篇 |
2009年 | 281篇 |
2008年 | 290篇 |
2007年 | 242篇 |
2006年 | 238篇 |
2005年 | 192篇 |
2004年 | 126篇 |
2003年 | 89篇 |
2002年 | 99篇 |
2001年 | 60篇 |
2000年 | 63篇 |
1999年 | 83篇 |
1998年 | 53篇 |
1997年 | 63篇 |
1996年 | 70篇 |
1995年 | 69篇 |
1994年 | 56篇 |
1993年 | 41篇 |
1992年 | 32篇 |
1991年 | 33篇 |
1990年 | 17篇 |
1989年 | 15篇 |
1988年 | 13篇 |
1987年 | 3篇 |
1986年 | 6篇 |
1985年 | 6篇 |
1984年 | 4篇 |
1983年 | 2篇 |
1982年 | 1篇 |
1980年 | 1篇 |
1965年 | 3篇 |
1936年 | 1篇 |
排序方式: 共有5737条查询结果,搜索用时 15 毫秒
1.
Dr. Yong-Sheng Wei Dr. Liming Sun Miao Wang Dr. Jinhua Hong Dr. Lianli Zou Hongwen Liu Dr. Yu Wang Dr. Mei Zhang Dr. Zheng Liu Prof. Yinwei Li Prof. Satoshi Horike Prof. Kazu Suenaga Prof. Qiang Xu 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(37):16147-16156
Understanding the thermal aggregation behavior of metal atoms is important for the synthesis of supported metal clusters. Here, derived from a metal–organic framework encapsulating a trinuclear FeIII2FeII complex (denoted as Fe3) within the channels, a well-defined nitrogen-doped carbon layer is fabricated as an ideal support for stabilizing the generated iron nanoclusters. Atomic replacement of FeII by other metal(II) ions (e.g., ZnII/CoII) via synthesizing isostructural trinuclear-complex precursors (Fe2Zn/Fe2Co), namely the “heteroatom modulator approach”, is inhibiting the aggregation of Fe atoms toward nanoclusters with formation of a stable iron dimer in an optimal metal–nitrogen moiety, clearly identified by direct transmission electron microscopy and X-ray absorption fine structure analysis. The supported iron dimer, serving as cooperative metal–metal site, acts as efficient oxygen evolution catalyst. Our findings offer an atomic insight to guide the future design of ultrasmall metal clusters bearing outstanding catalytic capabilities. 相似文献
2.
Xinghua Li Yuqin Yang Junjie Miao Zhendong Yin Yijing Zhai Hongmei Shi Zengning Li 《Electrophoresis》2020,41(18-19):1584-1591
In the present research, field-amplified sample injection–CZE (FASI–CZE) coupled with a diode array detector was established to determine trace level sulfa antibiotic. Sulfathiazole, sulfadiazine, sulfamethazine, sulfadimethoxine, sulfamethoxazole, and sulfisoxazole were selected as analytes for the experiments. The background electrolyte solution consisted of 70.0 mmol/L borax and 60.0 mmol/L boric acid (including 10% methanol, pH 9.1). The plug was 2.5 mmol/L borax, which was injected into the capillary at a pressure of 0.5 psi for 5 s. Then the sample was injected into the capillary at an injection voltage of –10 kV for 20 s. The electrophoretic separation was carried out under a voltage of +19 kV. The capillary temperature was maintained at 20˚C throughout the analysis, and six sulfonamides were completely separated within 35 min. Compared with pressure injection-CZE, the sensitivity of FASI-CZE was increased by 6.25–10.0 times, and the LODs were reduced from 0.2–0.5 to 0.02–0.05 μg/mL. The method was applied to the determination of sulfonamides in river water and particulate matter samples. The recoveries were 78.59–106.59%. The intraday and interday precisions were 2.89–7.35% and 2.77–7.09%, respectively. This provides a simpler and faster method for the analysis of sulfa antibiotic residues in environmental samples. 相似文献
3.
Lan-Lan Zhang Dr. Wen-Ke Miao Dr. Li-Jun Ren Yu-Kun Yan Dr. Yue Lin Prof. Wei Wang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(58):13396-13401
Organic polymers and inorganic clusters belong to two different disciplines and have completely different properties and structures. When a cluster is attached to the backbone of a polymer as a pendant, the resultant hybrid polymers (polyclusters) exhibit unique behaviours totally different from those of conventional polymers owing to the nanoscale size of the cluster and its particular interactions. Herein, the aggregation of a poly(polyoxometalate)—a polynorbornene backbone with inorganic polyoxometalate cluster pendants—upon addition of a non-solvent to its dilute solution is reported. A three-dimensional network of tangled and snake-like nanothreads was observed. Direct visualisation of individual nanoscale clusters enabled identification of single chains within the nanothreads. These observations suggest that during the process of aggregation, the hybrid polymer forms curved or extended chains as a consequence of an armouring effect in which the collapsed cluster pendants wrap around the backbone. The collapse occurs because they become less soluble in the solvent/non-solvent mixture. The extended chains then become entwined and form nanoropes consisting of multiple chains wound around each other. This study provides a deeper understanding of the nature of polyclusters and should also prove useful for their future development and application. 相似文献
4.
表面贴装工艺流程的关键工序之一就是焊膏印刷,其工艺控制的好坏直接影响着装配的线路板的质量。通过对印刷工艺参数的分析,利用试验设计的方法来找出关键工艺参数,并加以优化设定,从而为控制工序参数奠定基础。 相似文献
5.
6.
7.
Nakagami信道是一种适应性较强的信道模型,MQAM(M-ary quadrature amplitude modulation)是一种频谱利用率较高的调制方式。在存在多径影响的无线通信环境中,最大比合并(maximum ratio combining)方式的分集接收是克服衰落的有效方法。本文利用适用范围更广的Nakagami信道模型,在多径衰落的情况下对最大比合并分集接收的MQAM系统误符号率性能作了分析。仿真结果对分析实际信道下具体系统的性能具有一定的参考价值。 相似文献
8.
林苗 《电气电子教学学报》2002,24(1):43-45
阐述了我校使用“面向21世纪”电工学课程系列教材的实践与探索过程,以及对我校电工学教学所产生的转折性影响和积极的导向作用,最后对教材提出了几点建议。 相似文献
9.
10.