全文获取类型
收费全文 | 174205篇 |
免费 | 2430篇 |
国内免费 | 733篇 |
专业分类
化学 | 94166篇 |
晶体学 | 2303篇 |
力学 | 7729篇 |
综合类 | 7篇 |
数学 | 18324篇 |
物理学 | 54839篇 |
出版年
2021年 | 1094篇 |
2020年 | 1174篇 |
2019年 | 1206篇 |
2018年 | 1205篇 |
2017年 | 1232篇 |
2016年 | 2500篇 |
2015年 | 2007篇 |
2014年 | 2628篇 |
2013年 | 7920篇 |
2012年 | 6530篇 |
2011年 | 8242篇 |
2010年 | 5070篇 |
2009年 | 5216篇 |
2008年 | 7561篇 |
2007年 | 7555篇 |
2006年 | 7234篇 |
2005年 | 6770篇 |
2004年 | 6052篇 |
2003年 | 5222篇 |
2002年 | 5096篇 |
2001年 | 6073篇 |
2000年 | 4612篇 |
1999年 | 3519篇 |
1998年 | 2662篇 |
1997年 | 2660篇 |
1996年 | 2629篇 |
1995年 | 2323篇 |
1994年 | 2210篇 |
1993年 | 2055篇 |
1992年 | 2362篇 |
1991年 | 2332篇 |
1990年 | 2049篇 |
1989年 | 2038篇 |
1988年 | 2011篇 |
1987年 | 1935篇 |
1986年 | 1843篇 |
1985年 | 2770篇 |
1984年 | 2759篇 |
1983年 | 2187篇 |
1982年 | 2378篇 |
1981年 | 2274篇 |
1980年 | 2220篇 |
1979年 | 2171篇 |
1978年 | 2244篇 |
1977年 | 2197篇 |
1976年 | 2122篇 |
1975年 | 2117篇 |
1974年 | 2022篇 |
1973年 | 2099篇 |
1972年 | 1188篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
51.
Galkina E. G. Zaspel C. E. Ivanov B. A. Kulagin N. E. Lerman L. M. 《JETP Letters》2019,110(7):481-486
JETP Letters - The motion of domain walls in GdFeCo-type ferrimagnets near the point of compensation of sublattice spins s1 and s2, when the effects of the exchange increase in the limiting wall... 相似文献
52.
Roberto Aravire Ahmed Laghribi Manuel ORyan 《Journal of Pure and Applied Algebra》2019,223(1):439-457
Let F be a field of characteristic 2. In this paper we give a complete computation of the kernel of the homomorphism induced by scalar extension, where is a purely inseparable extension (of any degree), is the cokernel of the Artin–Schreier operator given by: , where is the space of absolute m-differential forms over F and d is the differential operator. Other related results are included. 相似文献
53.
K.M.J. Rocha R.G. Leitão E.G. Oliveira-Barros M.A. Oliveira C.G.L. Canellas M.J. Anjos L.E. Nasciutti R.T. Lopes 《X射线光谱测定》2019,48(5):476-481
Prostate cancer is a highly prevalent disease and ranks second among malignant neoplasms that affect men around the world, behind lung cancer alone. Trace elements are very important and are involved in many cellular processes. The X-ray microfluorescence technique is an advanced tool of high spatial resolution, sensitivity, multielemental analysis, and nondestructiveness for trace element study. This study aimed to investigate the elemental distribution in spheroids obtained through the following human prostate cell lines using synchrotron X-ray microfluorescence: tumor cell line androgen independent (DU145), tumor cell line androgen dependent (LNCaP), and normal cell line (RWPE-1). The measurements were performed with a standard geometry of 45° of incidence, excited by a white beam using a pixel of 25 μm and an acquisition time of 300 ms/pixel at the X-ray fluorescence beamline at the Synchrotron Light National Laboratory (Campinas, Brazil). The synchrotron X-ray microfluorescence results showed differences between groups in all elements analyzed and suggested that further studies should be performed to understand the relationship of these trace elements with the progression and development of the disease. 相似文献
54.
Simen Gjelseth Antonsen Arne Joakim C. Bunkan Tomas Mikoviny Yngve Stenstrøm Armin Wisthaler 《Molecular physics》2020,118(15)
The kinetics of the O3, OH and NO3 radical reactions with diazomethane were studied in smog chamber experiments employing long-path FTIR and PTR-ToF-MS detection. The rate coefficients were determined to be k CH2NN+O3?=?(3.2?±?0.4)?×?10?17 and k CH2NN+OH?=?(1.68?±?0.12)?×?10?10 cm3 molecule?1 s?1 at 295?±?3?K and 1013?±?30 hPa, whereas the CH2NN?+?NO3 reaction was too fast to be determined in the static smog chamber experiments. Formaldehyde was the sole product observed in all the reactions. The experimental results are supported by CCSD(T*)-F12a/aug-cc-pVTZ//M062X/aug-cc-pVTZ calculations showing the reactions to proceed exclusively via addition to the carbon atom. The atmospheric fate of diazomethane is discussed. 相似文献
55.
Claudia Poloni Marc C. A. Stuart Pieter van der Meulen Wiktor Szymanski Ben L. Feringa 《Chemical science》2015,6(12):7311-7318
The external photocontrol over peptide folding, by the incorporation of molecular photoswitches into their structure, provides a powerful tool to study biological processes. However, it is limited so far to switches that exhibit only a rather limited geometrical change upon photoisomerization and that show thermal instability of the photoisomer. Here we describe the use of an overcrowded alkene photoswitch to control a model β-hairpin peptide. This photoresponsive unit undergoes a large conformational change and has two thermally stable isomers which has major influence on the secondary structure and the aggregation of the peptide, permitting the phototriggered formation of amyloid-like fibrils. 相似文献
56.
57.
58.
59.
Leonor Contreras Ignacio Villarroel Camila Torres Roberto Rozas 《Molecules (Basel, Switzerland)》2021,26(6)
Doxorubicin (DOX), a recognized anticancer drug, forms stable associations with carbon nanotubes (CNTs). CNTs when properly functionalized have the ability to anchor directly in cancerous tumors where the release of the drug occurs thanks to the tumor slightly acidic pH. Herein, we study the armchair and zigzag CNTs with Stone–Wales (SW) defects to rank their ability to encapsulate DOX by determining the DOX-CNT binding free energies using the MM/PBSA and MM/GBSA methods implemented in AMBER16. We investigate also the chiral CNTs with haeckelite defects. Each haeckelite defect consists of a pair of square and octagonal rings. The armchair and zigzag CNT with SW defects and chiral nanotubes with haeckelite defects predict DOX-CNT interactions that depend on the length of the nanotube, the number of present defects and nitrogen doping. Chiral nanotubes having two haeckelite defects reveal a clear dependence on the nitrogen content with DOX-CNT interaction forces decreasing in the order 0N > 4N > 8N. These results contribute to a further understanding of drug-nanotube interactions and to the design of new drug delivery systems based on CNTs. 相似文献
60.