全文获取类型
收费全文 | 2065篇 |
免费 | 260篇 |
国内免费 | 242篇 |
专业分类
化学 | 1433篇 |
晶体学 | 20篇 |
力学 | 90篇 |
综合类 | 4篇 |
数学 | 330篇 |
物理学 | 690篇 |
出版年
2024年 | 7篇 |
2023年 | 48篇 |
2022年 | 75篇 |
2021年 | 90篇 |
2020年 | 101篇 |
2019年 | 73篇 |
2018年 | 64篇 |
2017年 | 68篇 |
2016年 | 96篇 |
2015年 | 91篇 |
2014年 | 96篇 |
2013年 | 142篇 |
2012年 | 164篇 |
2011年 | 172篇 |
2010年 | 92篇 |
2009年 | 113篇 |
2008年 | 125篇 |
2007年 | 119篇 |
2006年 | 92篇 |
2005年 | 94篇 |
2004年 | 54篇 |
2003年 | 42篇 |
2002年 | 40篇 |
2001年 | 44篇 |
2000年 | 46篇 |
1999年 | 37篇 |
1998年 | 26篇 |
1997年 | 27篇 |
1996年 | 42篇 |
1995年 | 35篇 |
1994年 | 34篇 |
1993年 | 29篇 |
1992年 | 24篇 |
1991年 | 33篇 |
1990年 | 25篇 |
1989年 | 14篇 |
1988年 | 15篇 |
1987年 | 13篇 |
1986年 | 11篇 |
1985年 | 10篇 |
1984年 | 11篇 |
1983年 | 4篇 |
1982年 | 8篇 |
1981年 | 5篇 |
1980年 | 4篇 |
1979年 | 5篇 |
1977年 | 2篇 |
1975年 | 2篇 |
1968年 | 1篇 |
1957年 | 1篇 |
排序方式: 共有2567条查询结果,搜索用时 15 毫秒
991.
Yangyang Li Hailiang Pang Dong Wu Zheqi Li Wang Wang Hong Wei Ying Fu Guoyin Yin 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(26):8964-8968
An unprecedented nickel‐catalyzed 1,1‐alkylboration of electronically unbiased alkenes has been developed, providing straightforward access to secondary aliphatic boronic esters from readily available materials under very mild reaction conditions. The regioselectivity of this reaction is governed by a unique pyridyl carboxamide ligated catalyst, rather than the substrates. Moreover, this transformation shows excellent chemo‐ and regio‐selectivity and remarkably good functional‐group tolerance. We also demonstrate that under balloon pressure, ethylene can also be utilized as a substrate. Additionally, competence experiments indicate that selective bond formation is favored at the α‐position of boron and preliminary mechanistic studies indicate that the key step in this three‐component reaction involves a 1,2‐nickel migration. 相似文献
992.
Feng Yu Vincent Tiing Tiong Le Pang Rusen Zhou Xiaoxiang Wang Eric R. Waclawik Kostya Ken Ostrikov Hongxia Wang 《中国化学快报》2019,30(5):1115-1120
Due to the synergistic effect between ZnS and Cu5Sn2S7, the ZnS can enhance electrochemical performance of pristine Cu5Sn2S7. 相似文献
993.
本文基于拓扑优化方法设计并制备了一种宽频吸波复合材料,该吸波复合材料由高强玻璃纤维透波板、电阻损耗型超材料、聚氨酯泡沫和碳纤维反射板组成.仿真及测试结果表明,该吸波复合材料在2–18 GHz频段内的平板反射率均小于-12 dB.并且由于采用高强玻璃纤维及碳纤维复合材料作为面板层,聚氨酯泡沫作为芯材,因此该吸波复合材料不仅在较宽频带内对电磁波具有高的吸收率,同时还具有质量轻、耐高温、耐低温、耐湿热、抗腐蚀等特点,便于实现吸波与力学性能及耐环境性能的兼容,具有一定的工程应用价值. 相似文献
994.
Yi Lu Pingan Yang Yanhong Li Dandan Wen Jiasai Luo Shuhui Wang Fang Wu Liang Fang Yu Pang 《Molecules (Basel, Switzerland)》2021,26(16)
Microwave-absorbing materials have attracted increased research interest in recent years because of their core roles in the fields of electromagnetic (EM) pollution precaution and information security. In this paper, microwave-absorbing material NiFe-layered double hydroxide (NiFe-LDH) was synthesized by a simple co-precipitation method and calcined for the fabrication of NiFe-mixed metal oxide (NiFe-MMO). The phase structure and micromorphology of the NiFe-LDH and NiFe-MMO were analyzed, and their microwave-absorbing properties were investigated with a vector network analyzer in 2–18 GHz. Both NiFe-LDH and NiFe-MMO possessed abundant interfaces and a low dielectric constant, which were beneficial to electromagnetic wave absorption, owing to the synergistic effect of multi-relaxation and impedance matching. The optimum reflection loss (RL) of NiFe-LDH and NiFe-MMO was −58.8 dB and −64.4 dB, respectively, with the thickness of 4.0 mm in the C band. This work demonstrates that LDH-based materials have a potential application in electromagnetic wave absorption. 相似文献
995.
996.
The potential of the B meson and the pseudoscalar meson is constructed up to the next-to-leading order Lagrangian, and then the BK and B_sπ interaction is studied in the unitary coupled-channel approximation. A resonant state with a mass about 5568 MeV and J~P= 0~+is generated dynamically, which can be associated with the X(5568) state announced by the D0 Collaboration recently. The mass and the decay width of this resonant state depend on the regularization scale in the dimensional regularization scheme, or the maximum momentum in the momentum cutoff regularization scheme. The scattering amplitude of the vector B meson and the pseudoscalar meson is calculated, and an axial-vector state with a mass near 5620 MeV and J~P= 1~+is produced. Their partners in the charm sector are also discussed. 相似文献
997.
Hongfu Sun Chengyu Wang Shihong Pang Xiping Li Ying Tao Huajuan Tang Ming Liu 《Journal of Non》2008,354(12-13):1440-1443
Nanometer semiconductor titanium dioxide thin films have excellent properties of photocatalysitic degeneration. The glass coated TiO2 films is called self-cleaning glass. In this paper, chemical vapor deposition (CVD) method is employed to deposit TiO2 films on glass. The effect of spacing between nozzle and glass and the effect of substrate temperature on deposition rate are studied. The crystalline structure at different deposition temperatures is analyzed by XRD and anatase was found. And the microstructure of the TiO2 films is also determined by SEM. It shows that the size of crystal grain increases with the temperature. 相似文献
998.
999.
1000.