全文获取类型
收费全文 | 98482篇 |
免费 | 12426篇 |
国内免费 | 9388篇 |
专业分类
化学 | 51241篇 |
晶体学 | 794篇 |
力学 | 4165篇 |
综合类 | 516篇 |
数学 | 9071篇 |
物理学 | 25591篇 |
无线电 | 28918篇 |
出版年
2024年 | 308篇 |
2023年 | 1980篇 |
2022年 | 2524篇 |
2021年 | 3256篇 |
2020年 | 3158篇 |
2019年 | 3004篇 |
2018年 | 2590篇 |
2017年 | 2576篇 |
2016年 | 3593篇 |
2015年 | 3944篇 |
2014年 | 4759篇 |
2013年 | 6192篇 |
2012年 | 7525篇 |
2011年 | 7697篇 |
2010年 | 5615篇 |
2009年 | 5707篇 |
2008年 | 6163篇 |
2007年 | 5734篇 |
2006年 | 5305篇 |
2005年 | 4704篇 |
2004年 | 3640篇 |
2003年 | 3012篇 |
2002年 | 2798篇 |
2001年 | 2401篇 |
2000年 | 2211篇 |
1999年 | 2271篇 |
1998年 | 1996篇 |
1997年 | 1826篇 |
1996年 | 1842篇 |
1995年 | 1617篇 |
1994年 | 1479篇 |
1993年 | 1293篇 |
1992年 | 1204篇 |
1991年 | 1007篇 |
1990年 | 865篇 |
1989年 | 617篇 |
1988年 | 540篇 |
1987年 | 437篇 |
1986年 | 368篇 |
1985年 | 431篇 |
1984年 | 328篇 |
1983年 | 257篇 |
1982年 | 224篇 |
1981年 | 155篇 |
1980年 | 143篇 |
1979年 | 124篇 |
1978年 | 109篇 |
1976年 | 109篇 |
1975年 | 97篇 |
1974年 | 97篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
Rongzhen Wu Hongyu Chen Dr. Ninghui Chang Yuzhi Xu Prof. Dr. Jiao Jiao Prof. Dr. Hailong Zhang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(6):1166-1195
Bryostatins are a class of naturally occurring macrocyclic lactones with a unique fast developing portfolio of clinical applications, including treatment of AIDS, Alzheimer's disease, and cancer. This comprehensive account summarizes the recent progress (2014–present) in the development of bryostatins, including their total synthesis and biomedical applications. An emphasis is placed on the discussion of bryostatin 1 , the most-studied analogue to date. This review highlights the synthetic and biological challenges of bryostatins and provides an outlook on their future development. 相似文献
72.
Shaobo Cheng Vidushi Sharma Altug S. Poyraz Lijun Wu Xing Li Amy C. Marschilok Esther S. Takeuchi Kenneth J. Takeuchi Marivi Fernndez-Serra Yimei Zhu 《Chemical science》2020,11(19):4991
Tunneled metal oxides such as α-Mn8O16 (hollandite) have proven to be compelling candidates for charge-storage materials in high-density batteries. In particular, the tunnels can support one-dimensional chains of K+ ions (which act as structure-stabilizing dopants) and H2O molecules, as these chains are favored by strong H-bonds and electrostatic interactions. In this work, we examine the role of water molecules in enhancing the stability of K+-doped α-Mn8O16 (cryptomelane). The combined experimental and theoretical analyses show that for high enough concentrations of water and tunnel-ions, H2O displaces K+ ions from their natural binding sites. This displacement becomes energetically favorable due to the formation of K2+ dimers, thereby modifying the stoichiometric charge of the system. These findings have potentially significant technological implications for the consideration of cryptomelane as a Li+/Na+ battery electrode. Our work establishes the functional role of water in altering the energetics and structural properties of cryptomelane, an observation that has frequently been overlooked in previous studies.Water displaces potassium ions and initiates the formation of a homonuclear dimer ion (K2+) in the tunnels of hollandite. 相似文献
73.
74.
Locke Davenport Huyer Serena Mandla Yufeng Wang Scott B. Campbell Bess Yee Christian Euler Benjamin F. Lai A. Dawn Bannerman Dawn S. Y. Lin Miles Montgomery Kayla Nemr Timothy Bender Slava Epelman Radhakrishnan Mahadevan Milica Radisic 《Advanced functional materials》2021,31(6):2003341
Itaconate (ITA) is an emerging powerhouse of innate immunity with therapeutic potential that is limited in its ability to be administered in a soluble form. A library of polyester materials that incorporate ITA into polymer backbones resulting in materials with inherent immunoregulatory behavior is developed. Harnessing hydrolytic degradation release from polyester backbones, ITA polymers result in the mechanism specific immunoregulatory properties on macrophage polarization in vitro. In a functional assay, the polymer-released ITA inhibits bacterial growth on acetate. Translation to an in vivo model of biomaterial associated inflammation, intraperitoneal injection of ITA polymers demonstrate a rapid resolution of inflammation in comparison to a control polymer silicone, demonstrating the value of sustained biomimetic presentation of ITA. 相似文献
75.
Djoumessi E.E. Marsan E. Caloz C. Chaker M. Wu K. 《Microwave and Wireless Components Letters, IEEE》2006,16(11):603-605
A tunable dual-band quadrature hybrid coupler for mobile GSM bands (900 and 1800MHz) is proposed and characterized. The structure is composed of four quarter-wavelength sections at a frequency located between the two operating frequencies and two pairs of open-ended stubs. Frequency tuning is achieved by modifying the electrical length of the open-ended stubs with varactor-diode capacitors. A dual-band tunability of 33% and 10% is obtained for the first and the second bands, respectively 相似文献
76.
77.
Yang Aiying Wang Ziyu Zhang Zhaoyi Chen Zhangyuan Wu Deming 《电子科学学刊(英文版)》2003,20(6):461-466
A 10Gbit/s recirculating system is configured with Chirped Fiber Bragg Grating (CFBG) for the dispersion compensation. For the first time, the transmission distance in the loop reaches 1000km with bit error rate of 10-9. The effect of the group delay ripple of the fiber grating is also investigated in the recirculating systems, and it is shown that the transmission distance is limited to 4 cycles (4×167.1km ) in the loop with the power penalty fluctuation below 1.0dB. Thus the group delay ripple should be reduced to allow for the wavelength drift of±5GHz. At the end of this letter, the principles are given for designing long haul recirculating systems with dispersion compensation CFBG. 相似文献
78.
79.
CO2激光治疗皮肤基底细胞癌14例临床观察 总被引:4,自引:0,他引:4
目的 :探求一种简单 ,安全 ,效果好的基底细胞癌的治疗方法。方法 :对 1 4例基底细胞癌患者在局麻下用CO2 激光行基底细胞癌切除术或切除 +气化术。结果 :患者术中、术后出血少 ,伤口恢复快 ,愈合良好 ,疤痕表浅 ,随访未见复发。结论 :CO2 激光用于治疗基底细胞癌效果良好 ,无明显副作用 ,操作简单值得推广。 相似文献
80.
城域网的建设是今后光纤网络建设的一个热点,根据城域网的特点和系统技术要求选择光纤光缆是网络设计的重要组成部分。本根据城域网的特点和需求,对市场上现有的光纤光缆做了详细的分析和探讨,提出了城域网规划中光纤光缆选择的原则和具体的建议。 相似文献