全文获取类型
收费全文 | 18313篇 |
免费 | 2725篇 |
国内免费 | 871篇 |
专业分类
化学 | 19888篇 |
晶体学 | 61篇 |
力学 | 395篇 |
综合类 | 16篇 |
数学 | 612篇 |
物理学 | 937篇 |
出版年
2024年 | 20篇 |
2023年 | 272篇 |
2022年 | 532篇 |
2021年 | 684篇 |
2020年 | 1263篇 |
2019年 | 966篇 |
2018年 | 787篇 |
2017年 | 658篇 |
2016年 | 1244篇 |
2015年 | 1099篇 |
2014年 | 1134篇 |
2013年 | 1351篇 |
2012年 | 977篇 |
2011年 | 1102篇 |
2010年 | 952篇 |
2009年 | 1035篇 |
2008年 | 977篇 |
2007年 | 876篇 |
2006年 | 832篇 |
2005年 | 747篇 |
2004年 | 723篇 |
2003年 | 594篇 |
2002年 | 1223篇 |
2001年 | 269篇 |
2000年 | 173篇 |
1999年 | 222篇 |
1998年 | 253篇 |
1997年 | 173篇 |
1996年 | 113篇 |
1995年 | 115篇 |
1994年 | 67篇 |
1993年 | 43篇 |
1992年 | 42篇 |
1991年 | 38篇 |
1990年 | 35篇 |
1989年 | 21篇 |
1988年 | 30篇 |
1987年 | 28篇 |
1986年 | 69篇 |
1985年 | 20篇 |
1984年 | 16篇 |
1983年 | 11篇 |
1982年 | 8篇 |
1981年 | 9篇 |
1980年 | 11篇 |
1979年 | 14篇 |
1978年 | 12篇 |
1977年 | 8篇 |
1972年 | 11篇 |
1966年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
Hideaki Murasugi Dr. Shohei Kumagai Dr. Hiroaki Iguchi Prof. Dr. Masahiro Yamashita Dr. Shinya Takaishi 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(42):9885-9891
Crystal structures of a series of organic–inorganic hybrid gold iodide perovskites, formulated as A2[AuII2][AuIIII4] [A=methylammonium (MA) ( 1 ) and formamidinium (FA) ( 2 )], A′2[I3]1−x[AuII2]x[AuIIII4] [A′=imidazolium (IMD) ( 3 ), guanidinium (GUA) ( 4 ), dimethylammonium (DMA) ( 5 ), pyridinium (PY) ( 6 ), and piperizinium (PIP) ( 7 )], systematically changed depending on the cation size. In addition, triiodide (I3−) ions were partly incorporated into the AuI2− sites of 3 – 7 , whereas they were not incorporated into those of 1 and 2 . Such a difference comes from the size of the organic cation. Optical absorption spectra showed characteristic intervalence charge-transfer bands from AuI to AuIII species, and the optical band gap increased as the size of the cation became larger. 相似文献
32.
Jin Xie Yun-Wei Song Dr. Bo-Quan Li Dr. Hong-Jie Peng Prof. Jia-Qi Huang Prof. Qiang Zhang 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(49):22334-22339
Polysulfide intermediates (PSs), the liquid-phase species of active materials in lithium–sulfur (Li-S) batteries, connect the electrochemical reactions between insulative solid sulfur and lithium sulfide and are key to full exertion of the high-energy-density Li-S system. Herein, the concept of sulfur container additives is proposed for the direct modification on the PSs species. By reversible storage and release of the sulfur species, the container molecule converts small PSs into large organosulfur species. The prototype di(tri)sulfide-polyethylene glycol sulfur container is highly efficient in the reversible PS transformation to multiply affect electrochemical behaviors of sulfur cathodes in terms of liquid-species clustering, reaction kinetics, and solid deposition. The stability and capacity of Li-S cells was thereby enhanced. The sulfur container is a strategy to directly modify PSs, enlightening the precise regulation on Li-S batteries and multi-phase electrochemical systems. 相似文献
33.
34.
35.
36.
37.
In this paper, we will propose algorithms for calculating a minimal ellipsoid circumscribing a polytope defined by a system
of linear inequalities. If we know all vertices of the polytope and its cardinality is not very large, we can solve the problem
in an efficient manner by a number of existent algorithms. However, when the polytope is defined by linear inequalities, these
algorithms may not work since the cardinality of vertices may be huge. Based on a fact that vertices determining an ellipsoid
are only a fraction of these vertices, we propose algorithms which iteratively calculate an ellipsoid which covers a subset
of vertices. Numerical experiment shows that these algorithms perform well for polytopes of dimension up to seven. 相似文献
38.
The drawbacks of our earlier report of preparing fuel cell catalyst arrays by borohydride reduction of inkjet prepared arrays of metal salts are discussed along with the need for inclusion of state-of-the-art metrics in all array screening. An alternative method for screening of hydrogen/air cathode catalysts, direct methanol fuel cell (DMFC) anode catalysts, and catalyst loading studies is provided. State-of-the-art Johnson Matthey catalysts were used in control experiments to demonstrate the utility of the array fuel cell for high throughput screening of fuel cell catalysts in the 3-4 mg/cm2 range. This report lays out hard learned rules for high throughput screening and demonstrates that the array fuel cell can be used for very precise screening of libraries of membrane electrode assembly (MEA) components without the pitfalls discussed in the introduction. 相似文献
39.
Jesús Vázquez 《Tetrahedron letters》2006,47(10):1657-1661
Use of a semicarbazide resin for the solid-phase preparation of peptide ketones and aldehyde led to optimal results in terms of both purity of the final product and overall yield. This resin was prepared without complication by activation of the commercial available aminomethyl polystyrene with CDI at room temperature, followed by treatment with tert-butyl carbazate. Furthermore, the TNBSA colorimetric assay has been adapted for checking the incorporation of the carbonyl moiety onto hydrazine-based resins. 相似文献
40.