全文获取类型
收费全文 | 69936篇 |
免费 | 9848篇 |
国内免费 | 7407篇 |
专业分类
化学 | 36837篇 |
晶体学 | 543篇 |
力学 | 3402篇 |
综合类 | 399篇 |
数学 | 6066篇 |
物理学 | 19379篇 |
无线电 | 20565篇 |
出版年
2024年 | 147篇 |
2023年 | 1601篇 |
2022年 | 1701篇 |
2021年 | 2453篇 |
2020年 | 2555篇 |
2019年 | 2233篇 |
2018年 | 1950篇 |
2017年 | 1889篇 |
2016年 | 2732篇 |
2015年 | 2873篇 |
2014年 | 3525篇 |
2013年 | 4527篇 |
2012年 | 5656篇 |
2011年 | 5686篇 |
2010年 | 4061篇 |
2009年 | 4079篇 |
2008年 | 4448篇 |
2007年 | 3954篇 |
2006年 | 3894篇 |
2005年 | 3406篇 |
2004年 | 2587篇 |
2003年 | 2153篇 |
2002年 | 1966篇 |
2001年 | 1710篇 |
2000年 | 1563篇 |
1999年 | 1749篇 |
1998年 | 1477篇 |
1997年 | 1322篇 |
1996年 | 1423篇 |
1995年 | 1228篇 |
1994年 | 1116篇 |
1993年 | 932篇 |
1992年 | 863篇 |
1991年 | 672篇 |
1990年 | 570篇 |
1989年 | 420篇 |
1988年 | 375篇 |
1987年 | 306篇 |
1986年 | 231篇 |
1985年 | 229篇 |
1984年 | 189篇 |
1983年 | 158篇 |
1982年 | 112篇 |
1981年 | 85篇 |
1980年 | 67篇 |
1979年 | 39篇 |
1978年 | 30篇 |
1976年 | 31篇 |
1975年 | 36篇 |
1974年 | 26篇 |
排序方式: 共有10000条查询结果,搜索用时 734 毫秒
21.
22.
Wireless Networks - In such mobile platforms as ships and aircraft, the detection and reconnaissance devices are near to the communication facilities. When working at the same time, they will... 相似文献
23.
24.
Nonlinear Dynamics - Epilepsy is the second largest neurological disease which seriously threatens human life and health. The one important reason of inducing epileptic seizures is ischemic stroke... 相似文献
25.
Rongrong Li Hongjie Peng Qingping Wu Xuejun Zhou Jiang He Hangjia Shen Minghui Yang Chilin Li 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(29):12227-12236
Herein, we propose the construction of a sandwich-structured host filled with continuous 2D catalysis–conduction interfaces. This MoN-C-MoN trilayer architecture causes the strong conformal adsorption of S/Li2Sx and its high-efficiency conversion on the two-sided nitride polar surfaces, which are supplied with high-flux electron transfer from the buried carbon interlayer. The 3D self-assembly of these 2D sandwich structures further reinforces the interconnection of conductive and catalytic networks. The maximized exposure of adsorptive/catalytic planes endows the MoN-C@S electrode with excellent cycling stability and high rate performance even under high S loading and low host surface area. The high conductivity of this trilayer texture does not compromise the capacity retention after the S content is increased. Such a job-synergistic mode between catalytic and conductive functions guarantees the homogeneous deposition of S/Li2Sx, and avoids thick and devitalized accumulation (electrode passivation) even after high-rate and long-term cycling. 相似文献
26.
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
27.
28.
29.
30.
Within the framework of the effective-mass approximation and the dipole approximation, considering the three-dimensional confinement of the electron and hole and the strong built-in electric field(BEF) in strained wurtzite Zn O/Mg0:25Zn0:75O quantum dots(QDs), the optical properties of ionized donor-bound excitons(D+, X)are investigated theoretically using a variational method. The computations are performed in the case of finite band offset. Numerical results indicate that the optical properties of(D+, X) complexes sensitively depend on the donor position, the QD size and the BEF. The binding energy of(D+, X) complexes is larger when the donor is located in the vicinity of the left interface of the QDs, and it decreases with increasing QD size. The oscillator strength reduces with an increase in the dot height and increases with an increase in the dot radius. Furthermore, when the QD size decreases, the absorption peak intensity shows a marked increment, and the absorption coefficient peak has a blueshift. The strong BEF causes a redshift of the absorption coefficient peak and causes the absorption peak intensity to decrease remarkably. The physical reasons for these relationships have been analyzed in depth. 相似文献