全文获取类型
收费全文 | 72655篇 |
免费 | 9137篇 |
国内免费 | 8851篇 |
专业分类
化学 | 31402篇 |
晶体学 | 671篇 |
力学 | 2645篇 |
综合类 | 524篇 |
数学 | 4692篇 |
物理学 | 16378篇 |
综合类 | 34331篇 |
出版年
2024年 | 276篇 |
2023年 | 1138篇 |
2022年 | 2067篇 |
2021年 | 2281篇 |
2020年 | 2299篇 |
2019年 | 2139篇 |
2018年 | 1888篇 |
2017年 | 2082篇 |
2016年 | 2639篇 |
2015年 | 3271篇 |
2014年 | 4211篇 |
2013年 | 5062篇 |
2012年 | 5726篇 |
2011年 | 5979篇 |
2010年 | 4842篇 |
2009年 | 5062篇 |
2008年 | 5383篇 |
2007年 | 4861篇 |
2006年 | 4378篇 |
2005年 | 3585篇 |
2004年 | 2823篇 |
2003年 | 2463篇 |
2002年 | 2809篇 |
2001年 | 2544篇 |
2000年 | 1944篇 |
1999年 | 1646篇 |
1998年 | 1098篇 |
1997年 | 955篇 |
1996年 | 888篇 |
1995年 | 743篇 |
1994年 | 713篇 |
1993年 | 531篇 |
1992年 | 449篇 |
1991年 | 386篇 |
1990年 | 353篇 |
1989年 | 273篇 |
1988年 | 212篇 |
1987年 | 161篇 |
1986年 | 126篇 |
1985年 | 66篇 |
1984年 | 33篇 |
1983年 | 35篇 |
1982年 | 17篇 |
1981年 | 18篇 |
1980年 | 11篇 |
1979年 | 21篇 |
1977年 | 11篇 |
1957年 | 13篇 |
1936年 | 8篇 |
1925年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 8 毫秒
91.
92.
93.
Fengfu Fu Liangjun Xu Wei Ye Yiquan Chen Mingyu Jiang Xueqin Xu 《中国颗粒学报》2006,4(6):323-326
Different-sized aerosols were collected by an Andersen air sampler to observe the detailed morphology of the black carbon (BC) aerosols which were separated chemically from the other accompanying aerosols, using a Scanning Electron Microscope equipped with an Energy Dispersive X-ray Spectrometer (SEM-EDX). The results indicate that most BC aerosols are spherical particles of about 50 nm in diameter and with a homogeneous surface. Results also show that these particles aggregate with other aerosols or with themselves to form larger agglomerates in the micrometer range. The shape of these 50-nm BC spherical particles was found to be very similar to that of BC particles released from petroleum-powered vehicular internal combustion engines. These spherical BC particles were shown to be different from the previously reported fullerenes found using Matrix-Assisted Laser Desorption/Ionization Time-Of-Flight Mass Spectrometry (MALDI-TOF-MS). 相似文献
94.
The relaxed energy and structure of (0 0 1) twist grain boundary (GB) in noble metals Au, Ag and Cu are simulated by the MAEAM. In-boundary translation between two adjacent grains results in a periodic energy variation and the period is a square with the side length LΣ/Σ. The lowest energy appears when the two grains are translated relatively to either corner or center of the periodic square. The relaxed GB energy increases smoothly for low-angle boundaries and levels off for larger-angle boundaries except a cusp appeared at θ = 36.87° (Σ = 5). After relaxation, the symmetry of the GB structure is not changed but the displacement of the atoms parallel to the GB plane decreases with increasing the distance of the atoms from the GB plane. 相似文献
95.
Baoqiang Li Dechang Jia Yu Zhou Qiaoling Hu Wei Cai 《Journal of magnetism and magnetic materials》2006
Chitosan/magnetite nanocomposite was synthesized induced by magnetic field via in situ hybridization in ambient condition. Results of XRD patterns and TEM micrographs indicated that magnetite particles with 10–20 nm were dispersed in chitosan homogeneously. An interesting result is that magnetite nanoparticles were assembled to form chain-like structures under the influence of the external magnetic field, which mimics the magnetite chains inside of magnetotatic bacteria. The saturated magnetization (Ms) of nano-magnetite in chitosan was 50.54 emu/g, which is as high as 54% of bulk magnetite. The remanence (Mr) and coercivity (Hc) were 4 emu/g and14.8 Oe, respectively, which indicated that magnetite nanoparticles were superparamagnetic. The key of route is that a pre-precipitated chitosan hydrogel membrane, used as chemical reactor, which controlled the precipitation of chitosan precipitation and in situ transformation of magnetite from the precursor simultaneously in the magnetic field environment. 相似文献
96.
97.
Characterization of autocatalytic decomposition reactions is important
for the safe handling and storage of energetic materials. Isothermal differential
scanning calorimetry (DSC) has been widely used to detect autocatalytic decomposition
of energetic materials. However, isothermal DSC tests are time consuming and
the choice of experimental temperature is crucial. This paper shows that an
automatic pressure tracking calorimeter (APTAC) can be a reliable and efficient
screening tool for the identification of autocatalytic decomposition behavior
of energetic materials.
Hydroxylamine nitrate (HAN) is an important
member of the hydroxylamine family. High concentrations of HAN are used as
liquid propellants, and low concentrations of HAN are used primarily in the
nuclear industry for decontamination of equipment. Because of its instability
and autocatalytic decomposition behavior, HAN has been involved in several
incidents. 相似文献
98.
In-plane single domain and vortex magnetization configurations of the magnetic dot in the hybrid superconductor–ferromagnet system are considered. Single domain configuration energy shift due to the presence of superconductor is calculated. The change of the phase curve of the ferromagnetic dot magnetization due to the repulsion of the magnetic field by the superconductor is obtained. Up to the two-fold decrease of the ferromagnetic dot critical radius due to the presence of the superconductor is predicted. 相似文献
99.
利用关于乘积分布密度的相对熵和相对熵率的概念,建立了相依连续型随机变量序列关于参考微分熵的一类强偏差定理,证明中给出了将Laplace变换应用于微分熵强偏差定理的研究的一种途径. 相似文献
100.
The magnetic property in neodymium gallium garnet (NdGaG) is studied by the quantum theory. The ground configuration split states are calculated taking into account the spin–orbit interaction and crystal field effect. Taking account of the Nd–Nd exchange interaction, a good agreement between experimental and theoretical values can be obtained for the variation of the magnetic moment with the external magnetic field under “extreme” conditions (low temperature and high magnetic field). Moreover, the temperature dependence of magnetic moment and the magnetic susceptibility χ is also discussed. Above 30 K, the magnetization (M) shows a linear field (He) dependence. 相似文献