全文获取类型
收费全文 | 2974篇 |
免费 | 71篇 |
国内免费 | 222篇 |
专业分类
化学 | 1002篇 |
晶体学 | 18篇 |
力学 | 17篇 |
综合类 | 7篇 |
数学 | 1868篇 |
物理学 | 355篇 |
出版年
2024年 | 4篇 |
2023年 | 31篇 |
2022年 | 34篇 |
2021年 | 40篇 |
2020年 | 30篇 |
2019年 | 80篇 |
2018年 | 85篇 |
2017年 | 59篇 |
2016年 | 54篇 |
2015年 | 44篇 |
2014年 | 105篇 |
2013年 | 395篇 |
2012年 | 93篇 |
2011年 | 231篇 |
2010年 | 225篇 |
2009年 | 190篇 |
2008年 | 234篇 |
2007年 | 210篇 |
2006年 | 170篇 |
2005年 | 116篇 |
2004年 | 80篇 |
2003年 | 93篇 |
2002年 | 68篇 |
2001年 | 45篇 |
2000年 | 43篇 |
1999年 | 46篇 |
1998年 | 34篇 |
1997年 | 34篇 |
1996年 | 58篇 |
1995年 | 49篇 |
1994年 | 45篇 |
1993年 | 36篇 |
1992年 | 28篇 |
1991年 | 27篇 |
1990年 | 18篇 |
1989年 | 7篇 |
1988年 | 13篇 |
1987年 | 9篇 |
1986年 | 9篇 |
1985年 | 22篇 |
1984年 | 12篇 |
1983年 | 10篇 |
1982年 | 12篇 |
1981年 | 8篇 |
1980年 | 4篇 |
1979年 | 7篇 |
1978年 | 10篇 |
1976年 | 3篇 |
1974年 | 2篇 |
1973年 | 2篇 |
排序方式: 共有3267条查询结果,搜索用时 29 毫秒
1.
Joshua Maglione 《Journal of Pure and Applied Algebra》2021,225(3):106528
Like the lower central series of a nilpotent group, filters generalize the connection between nilpotent groups and graded Lie rings. However, unlike the case with the lower central series, the associated graded Lie ring may share few features with the original group: e.g. the associated Lie ring can be trivial or arbitrarily large. We determine properties of filters such that every isomorphism between groups is induced by an isomorphism between graded Lie rings. 相似文献
2.
Seon Yu Lee Ji Hyun Jeong Bo Na Kim So Jung Park Yang-Chun Park Guk Yeo Lee 《Biomedical chromatography : BMC》2020,34(4):e4774
The aim of this study was to confirm pharmacokinetic screening of multiple components in healthy Korean subjects after oral administration of Samso-eum and perform quantitation of active components in the human plasma. Thirteen potential bioactive components [puerarin (PRR), daidzin, nodakenin, ginsenoside Rb1, 18β-glycyrrhetinic acid (18β-GTA), 6-shogaol, naringin, glycyrrhizin, hesperidin, platycodin D, naringenin, hesperetin, and 6-gingerol] were screened based on literature. The results showed that three analytes (daidzin, naringenin, and hesperetin) were detected in trace amounts. In addition, PRR and 18β-GTA were detected in human plasma after the oral administration of Samso-eum. In this study, a liquid chromatography–electrospray ionization-tandem mass spectrometry method was validated for the simultaneous determination of PRR and 18β-GTA in human plasma. This was the first study to evaluate pharmacokinetics of PRR and 18β-GTA after the usual oral dose of Samso-eum (30 g containing 102.48 mg PRR, 48.18 mg glycyrrhizin) in human subjects. 相似文献
3.
Wei Hu Xiu-Hua Luo Bao-Lin Xiong Guodong Zhou 《Journal of Pure and Applied Algebra》2019,223(3):1014-1039
We generalize the monomorphism category from quiver (with monomial relations) to arbitrary finite dimensional algebras by a homological definition. Given two finite dimension algebras A and B, we use the special monomorphism category to describe some Gorenstein projective bimodules over the tensor product of A and B. If one of the two algebras is Gorenstein, we give a sufficient and necessary condition for being the category of all Gorenstein projective bimodules. In addition, if both A and B are Gorenstein, we can describe the category of all Gorenstein projective bimodules via filtration categories. Similarly, in this case, we get the same result for infinitely generated Gorenstein projective bimodules. 相似文献
4.
5.
Wenhe Yu Prof. Xiaowen Wu Bohao Cheng Dr. Tianyi Tao Dr. Xin Min Dr. Ruiyu Mi Prof. Zhaohui Huang Prof. Minghao Fang Prof. Yangai Liu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(11):e202102787
Silicoaluminophosphate zeolite (SAPO-34) has been attracting increasing attention due to its excellent form selection and controllability in the chemical industry, as well as being one of the best industrial catalysts for methanol-to-olefin (MTO) reaction conversion. However, as a microporous molecular sieve, SAPO-34 easily generates carbon deposition and rapidly becomes inactivated. Therefore, it is necessary to reduce the crystal size of the zeolite or to introduce secondary macropores into the zeolite crystal to form a hierarchical structure in order to improve the catalytic effect. In this review, the synthesis methods of conventional SAPO-34 molecular sieves, hierarchical SAPO-34 molecular sieves and nanosized SAPO-34 molecular sieves are introduced, and the properties of the synthesized SAPO-34 molecular sieves are described, including the phase, morphology, pore structure, acid source, and catalytic performance, in particular with respect to the synthesis of hierarchical SAPO-34 molecular sieves. We hope that the review can provide guidance to the preparation of the SAPO-34 catalysts, and stimulate the future development of high-performance hierarchical SAPO-34 catalysts to meet the growing demands of the material and chemical industries. 相似文献
6.
7.
Dr. Zeyu Liu Dr. Tian Lu Prof. Aihua Yuan Xia Wang Qinxue Chen Dr. Xiufen Yan 《化学:亚洲杂志》2021,16(16):2267-2271
Inspired by recent experimental observation of molecular morphology and theoretical predictions of multiple properties of cyclo[18]carbon, we systematically studied the photophysical and nonlinear optical properties of cyclo[2N]carbons (N=3–15) allotropes through density functional theory. This work unveils the unusual optical properties of the sp-hybridized carbon rings with different sizes. The remarkable size dependence of the optical properties of these systems and their underlying nature are profoundly explored, and the relevance between aromaticity and optical properties are highlighted. The extrapolation curves fitted for energy level of frontier molecular orbitals, maximum absorption wavelength, and (hyper)polarizability of considered carbon rings are presented, which can be used to reliably predict corresponding properties for arbitrarily large carbon rings. The findings in this study will facilitate the exploration of potential application of cyclocarbons in the field of optical materials. 相似文献
8.
9.
《Journal of Pure and Applied Algebra》2022,226(10):107043
We use the machinery of categorified Jones-Wenzl projectors to construct a categorification of a type A Reshetikhin-Turaev invariant of oriented framed tangles where each strand is labelled by an arbitrary finite-dimensional representation. As a special case, we obtain a categorification of the coloured Jones polynomial of links. 相似文献
10.
Khaled Osati Ali Salajegheh Mohammad Mahdavi Kamran Chapi Arash Malekian 《Isotopes in environmental and health studies》2014,50(2):169-183
Karst springs of the Zagros Mountains contribute a significant amount to agricultural and human water demands of western and south-western Iran. For an adequate management of available water resources in semi-arid and arid regions, sufficient hydrological monitoring is needed, and hydro-chemical and isotope hydrological data provide important additional information. About 350 water samples were collected from precipitation, river water, and karst springs of the upper part of the Karkheh River Basin (20,895 km2) located between 33°35′ and 34°55′ North and 46°22′ and 49°10′ East with elevations ranging from 928 to 3563 m above sea level. Sampling was conducted in monthly time resolution from August 2011 to July 2012. All samples were analysed for hydro-chemical parameters (pH, electrical conductivity, and major ions) and stable isotopes (deuterium, oxygen-18). Isotope values of precipitation indicate a local meteoric water line (Zagros MWL δ2H=6.8 δ18O+10.1; R2=0.99) situated between the Mediterranean MWL and Global MWL. Spring and river water isotope values vary between?7.1 and?4.1 ‰, and?38 and?25 ‰ for δ18O and δ2H, respectively, responding to winter snowmelt and evaporation. This work implements stable isotopes and hydro-chemical information of springs and river water to understand hydrological and hydro-geological interrelations in karstic semi-arid areas and helps to improve the current water resources management practices of western Iran. 相似文献