全文获取类型
收费全文 | 8955篇 |
免费 | 1653篇 |
国内免费 | 931篇 |
专业分类
化学 | 5955篇 |
晶体学 | 86篇 |
力学 | 730篇 |
综合类 | 66篇 |
数学 | 1136篇 |
物理学 | 3566篇 |
出版年
2024年 | 38篇 |
2023年 | 184篇 |
2022年 | 306篇 |
2021年 | 349篇 |
2020年 | 347篇 |
2019年 | 325篇 |
2018年 | 297篇 |
2017年 | 292篇 |
2016年 | 433篇 |
2015年 | 426篇 |
2014年 | 465篇 |
2013年 | 644篇 |
2012年 | 757篇 |
2011年 | 830篇 |
2010年 | 555篇 |
2009年 | 534篇 |
2008年 | 617篇 |
2007年 | 476篇 |
2006年 | 520篇 |
2005年 | 376篇 |
2004年 | 314篇 |
2003年 | 252篇 |
2002年 | 234篇 |
2001年 | 201篇 |
2000年 | 190篇 |
1999年 | 190篇 |
1998年 | 181篇 |
1997年 | 174篇 |
1996年 | 169篇 |
1995年 | 137篇 |
1994年 | 121篇 |
1993年 | 112篇 |
1992年 | 91篇 |
1991年 | 69篇 |
1990年 | 76篇 |
1989年 | 61篇 |
1988年 | 44篇 |
1987年 | 34篇 |
1986年 | 34篇 |
1985年 | 22篇 |
1984年 | 18篇 |
1983年 | 14篇 |
1982年 | 15篇 |
1981年 | 3篇 |
1980年 | 7篇 |
1979年 | 2篇 |
1975年 | 1篇 |
1957年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
Jian Jiao Min Chen Shengxin Sun Weijie Si Xiaobin Wang Weijie Ding Xincan Fu An Wang Chunlong Yang 《中国化学》2021,(2):323-329
To screen novel antifungal agents targeting the succinate dehydrogenase(SDH),a series of pyrazole-4-carbohydrazides were rationally designed,synthesized,and characterized under the guidance of the structures of succinate dehydrogenase inhibitors(SDHIs).Bioassay results in vitro indicated that most of the target compounds exhibited excellent activity against Rhizoctonia solani(R.solani),Fusarium graminearum(F.graminearum),Botrytis cinerea(B.cinerea)and Colletotrichum capsica(C.cinerea).Compounds 7d,7l,7t and 7x were identified as the most promoting candidates,and their anti-F.graminearum EC50 values were as low as 0.56,0.47,0.46 and 0.49μg/mL,respectively,presenting the similar antifungal activity as that of the commonly used fungicide carbendazim(0.43μg/mL).The 3D-QSAR models were built for a systematic structure-activity relationship profile to explore more potent pyrazole-4-carbohydrazides as novel fungicides.Molecular docking of 7d,7l and 7r with SDH was performed to reveal the binding modes in active pocket and analyze the interactions between the molecules and the SDH protein. 相似文献
72.
The ground state absorption (GSA), photoluminescence (PL) and photoluminescence excitation (PLE) spectra for Er(1.0 at%):YAP and Er(0.5 at%):LSO were measured at room temperature. Based on the GSA spectra, the radiative transition rates and luminescence branch ratios of erbium ions were determined by the Judd-Ofelt (J-O) method. In the range of 1400-1700 nm Er(1.0 at%):YAP has intense absorption at 1509 nm (0.96×10−20 cm2), which is almost two times larger than the peak absorption of Er(0.5 at%):LSO. From the PL and PLE spectra, four intense emission bands around 850 nm (4S3/2→4I13/2), 980 nm (4I11/2→4I15/2), 1230 nm (4S3/2→4I11/2) and 1520 nm (4I13/2→4I15/2) were observed. The stimulated emission cross-sections of the four bands were calculated by the Fuchtbauer-Ladenberg (F-L) equation. The results suggest that Er(1.0 at%):YAP has potential to realize laser oscillation at 858 nm because of the relatively large simulated emission cross-section (1.76×10−20 cm2). The temperature dependences of the PL spectra for the two crystals were also investigated in the range of 290-12 K. The ∼1520 nm emission presents continuous increase with temperature, while the emissions around 850, 1230 and 980 nm firstly increase with temperature, then reach their own largest values at the transition temperatures (about 100 K), and finally decrease with temperature. These results were well interpreted by the temperature dependence of multi-phonon process. 相似文献
73.
Tonghui Yang Xiaolan Liu Yanli Ding Shihua Zhao Naiqiang Yin 《Journal of nanoparticle research》2018,20(8):207
In this work, ZnO nanorod/Cu2O composite nanostructure solar cells were prepared using hydrothermal growth and electrodeposition. The CdS layer was added between ZnO and Cu2O to suppress carrier reverse recombination. Nondestructive interface deposition methods were employed to prepare CdS and Cu2O functional layers. The CdS layers were unconventionally deposited in non-alkaline solution, which can inhibit etching on the ZnO surface, and Cu2O layers were electrodeposited in ZnO-buffered alkaline solution which can also inhibit etching on the ZnO surface. Finally, the performance of solar cells was improved by adding a highly resistive CdS intermediate layer between ZnO and Cu2O layers. This work demonstrated the nondestructive interface approach of chemical solution deposition of functional layers on ZnO and possibilities for further improvements to the performance of Cu2O-based nanostructure solar cells with the addition of an intermediated layer. 相似文献
74.
Ding Yuan Ting Wu Rong-yuan Chen Gui-zhen Zhang 《Journal of Macromolecular Science: Physics》2018,57(5):348-363
The properties of polymer matrix composites are related not only to the chemical composition of the materials but also to the processing equipment used for their preparation which has a direct influence on the microstructure of the composites. In this paper polypropylene (PP)/multi-walled carbon nanotubes (MWCNTs) nanocomposites were prepared by melt blending through a self-developed, eccentric rotor extruder (ERE). The structure and elongational deformation mechanism of an ERE were described in detail. The morphological, rheological, thermal and mechanical properties of the resulting PP/MWCNTs nanocomposites were investigated. Scanning electron microscopy (SEM) and rheological analysis showed that the MWCNTs were well dispersed in the PP matrix. The thermal stability was investigated by thermogravimetric analysis (TGA) and indicated that the addition of MWCNTs could effectively improve the thermal stability of pure PP. The percentage of crystallinity and tensile strength of the composites were improved as a result of the heterogeneous nucleation effect of the MWCNTs in the PP matrix. The research results revealed that the enhancement of the properties of PP/MWCNTs composites could be attributed to a better dispersion of the MWCNTs in the matrix as compared to samples prepared by conventional extrusion. 相似文献
75.
In order to achieve a higher lateral resolution required for ultraprecision measurement of microstructural workpieces, phase-only pupil filtering differential confocal microscopy (PFDCM), a new approach is proposed based on the differential confocal microscopy (DCM), which uses a three-zone phase-only pupil filter with lateral super-resolution capability obtained through optimized design to change the distribution of DCM three-dimensional point spread function, so that the DCM lateral resolution is therefore significantly improved while its axial resolution is slightly improved. Preliminary experimental comparison and analyses indicate that, the lateral and axial resolutions of PFDCM are better than 0.2 μm and 2 nm, respectively, when wavelength of incidence laser beam , numerical aperture of measuring lens NA=0.85, and lateral spot size with a three-zone phase-only pupil filter GT=0.65. It is therefore concluded that PFDCM is a new approach to further improvement of lateral resolution in laser probe measurement systems. 相似文献
76.
采用基于密度泛函理论(DFT)的总体能量平面波超软赝势法,对Mg,Zn,Cd掺杂InN的32原子超原胞体系进行了几何结构优化,从理论上给出了掺杂和非掺杂体系的晶体结构参数,其中非掺杂体系的理论值与实验值符合很好. 计算了掺杂InN晶体的结合能,总体态密度、集居数,差分电荷密度,并对此做了细致的分析. 计算结果表明,相对于Zn和Cd,MgIn在InN中的溶解度会更大,并能提供更多的空穴态,非常有利于InN的p型掺杂.
关键词:
氮化铟
p型掺杂
电子结构
第一性原理 相似文献
77.
Fabrication of concave microlens arrays using controllable dielectrophoretic force in template holes 总被引:1,自引:0,他引:1
This Letter presents a method for fabricating concave microlens arrays of UV-curable polymer by using the dielectrophoresis (DEP) force. The DEP force, generated by a voltage between the patterned conductive template and substrate, acting on the polymer-air interface, can drive the dielectric liquid polymer into the template holes and change the shape of the polymer-air interface. The upper polymer surface of fabricated microlens is super smooth, which can reduce optical noise. The upper surface geometry is measured approximately as parabolic in general, which can lead to a negligible spherical aberration, compared to spherical surfaces. 相似文献
78.
Reiter P Khoo TL Lauritsen T Lister CJ Seweryniak D Sonzogni AA Ahmad I Amzal N Bhattacharyya P Butler PA Carpenter MP Chewter AJ Cizewski JA Davids CN Ding KY Fotiades N Greene JP Greenlees PT Heinz A Henning WF Herzberg R Janssens RV Jones GD Kondev FG Korten W Leino M 《Physical review letters》2000,84(16):3542-3545
The entry distribution in angular momentum and excitation energy for the formation of 254No has been measured after the 208Pb(48Ca,2n) reaction at 215 and 219 MeV. This nucleus is populated up to spin 22Planck's over 2pi and excitation energy greater, similar6 MeV above the yrast line, with the half-maximum points of the energy distributions at approximately 5 MeV for spins between 12Planck's over 2pi and 22Planck's over 2pi. This suggests that the fission barrier is greater, similar5 MeV and that the shell-correction energy persists to high spin. 相似文献
79.
80.
Ding Changgeng Yang Jinlong Cui Xiangyuan Wang Kelin 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,11(1):123-126
Geometrical and electronic structures of C35X fullerenes with , N and Si as substitutional dopants have been studied. Three non-equivalent sites in the D6h structure of C36 have been considered for the substitution. We have found that the dopant has a strong tendency to substitute at sites where
the carbon atom contributes significantly to the frontier orbitals of C36 and has the weakest interaction with its nearest-neighbor atoms. The relative stability of C35Si and C35B (C35N) has been investigated and high chemical reactivity of C35Si has been predicted.
Received 8 July 1999 and Received in final form 4 October 1999 相似文献