全文获取类型
收费全文 | 14383篇 |
免费 | 475篇 |
国内免费 | 52篇 |
专业分类
化学 | 11461篇 |
晶体学 | 84篇 |
力学 | 235篇 |
数学 | 1863篇 |
物理学 | 1267篇 |
出版年
2023年 | 98篇 |
2022年 | 105篇 |
2021年 | 535篇 |
2020年 | 320篇 |
2019年 | 363篇 |
2018年 | 274篇 |
2017年 | 231篇 |
2016年 | 488篇 |
2015年 | 478篇 |
2014年 | 456篇 |
2013年 | 912篇 |
2012年 | 981篇 |
2011年 | 1067篇 |
2010年 | 645篇 |
2009年 | 617篇 |
2008年 | 919篇 |
2007年 | 922篇 |
2006年 | 772篇 |
2005年 | 715篇 |
2004年 | 601篇 |
2003年 | 506篇 |
2002年 | 498篇 |
2001年 | 182篇 |
2000年 | 146篇 |
1999年 | 120篇 |
1998年 | 131篇 |
1997年 | 113篇 |
1996年 | 146篇 |
1995年 | 92篇 |
1994年 | 92篇 |
1993年 | 88篇 |
1992年 | 68篇 |
1991年 | 77篇 |
1990年 | 56篇 |
1989年 | 73篇 |
1988年 | 66篇 |
1987年 | 50篇 |
1986年 | 56篇 |
1985年 | 73篇 |
1984年 | 89篇 |
1983年 | 47篇 |
1982年 | 68篇 |
1981年 | 60篇 |
1980年 | 57篇 |
1979年 | 48篇 |
1978年 | 55篇 |
1977年 | 45篇 |
1976年 | 33篇 |
1975年 | 24篇 |
1963年 | 20篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
de Santana Felipe Silva Gracioso Louise Hase Karolski Bruno dos Passos Galluzzi Baltazar Marcela Mendes Maria Anita do Nascimento Claudio Augusto Oller Perpetuo Elen Aquino 《Applied biochemistry and biotechnology》2019,189(1):103-115
Applied Biochemistry and Biotechnology - The human exposure to bisphenol A (BPA) occurs frequently. Once, this compound was one of the highest volume chemicals produced worldwide and used as a... 相似文献
22.
The versatile behavior of a trihydrazidophosphoradamantane allowing the synthesis of a variety of neutral, mono- or di-cationic water-soluble molecules of potential interest for biphasic catalysis is reported. 相似文献
23.
Maria Kordaki Athanasia Balomenou 《International Journal of Computers for Mathematical Learning》2006,11(1):99-135
This study focuses on the constructions in terms of area and perimeter in equivalent triangles developed by students aged 12–15 years-old, using the tools provided by Cabri-Geometry II [Labore (1990). Cabri-Geometry (software), Université de Grenoble]. Twenty-five students participated in a learning experiment where they were asked to construct: (a) pairs of equivalent triangles “in as many ways as possible” and to study their area and their perimeter using any of the tools provided and (b) “any possible sequence of modifications of an original triangle into other equivalent ones”. As regards the concept of area and in contrast to a paper and pencil environment, Cabri provided students with different and potential opportunities in terms of: (a) means of construction, (b) control, (c) variety of representations and (d) linking representations, by exploiting its capability for continuous modifications. By exploiting these opportunities in the context of the given open tasks, students were helped by the tools provided to develop a broader view of the concept of area than the typical view they would construct in a typical paper and pencil environment. 相似文献
24.
Josep Maria Izquierdo 《TOP》2006,14(2):375-398
The paper introduces a refinement of the notion of population monotonic allocation scheme, called regular population monotonic
allocation scheme (regularpmas). This refinement is based on economic situations in which players may have to select new partners from a set of potential
players and in which there exist certain capacity constraints. A sufficient condition for the existence of a regularpmas is given. For the class of games with regularpmas, we prove that the core coincides with the Davis and Maschler and the Mas-Colell bargaining sets. 相似文献
25.
Antonio Uris Jose Maria Bravo Jaime Llinares Hermelando Estelles 《Applied Acoustics》2004,65(4):421-430
In this paper the influence on sound reduction index of the length and the depth of sound leaks at the perimeter of lightweight partitions was examined. It was shown that the most important decrease on sound reduction index is caused by the first slit between lightweight partition and one of the structural members. When the length of the slit is increased, the decrease on sound reduction index is less significative. Calculated results show the same effects as measured ones. 相似文献
26.
Teresa uczak Radosaw Pankiewicz Bogusawa ska Grzegorz Schroeder Maria Betowska-Brzezinska Bogumil Brzezinski 《Journal of Molecular Structure》2006,800(1-3):140-145
Novel self-assembled monolayers were obtained on silver using 4,7-diazaheptyl-trimethoxy-silane (SiN) and vinyl-trialkoxy-silane (SiVA, where the alkyl group is 3,6,9,12,15,18,21,24,27,30,33,36,39,42,45,48,51,54,57,60-eicozaoxa- hexaheptaconan). It was shown that thus modified metal surface was protected against electrooxidation. A densely packed monolayer remained stable and did not desorb from the Ag electrode on the potential cycling. The structure of SiN and SiVA as well as their complexes with Li+ cations were calculated and visualised by the AM1d and PM5 semi-empirical methods. 相似文献
27.
28.
29.
30.
Alberto Plaza Sonia Piacente Angela Perrone Arafa Hamed Cosimo Pizza Giuseppe Bifulco 《Tetrahedron》2004,60(52):12201-12209
Stemmosides C and D, two novel pregnane glycosides characterized by an unusual C-17 side chain were isolated from the pericarps of Solenostemma argel. In addition, stemmoside D displays an uncommon 14β proton configuration, apparently being the first pregnane isolated from plants known to have a 15 keto, cis CD ring junction. Their structures have been established by ESIMS and NMR experiments. The relative configuration of the molecules was determined using a strategy based on the simulation of 1H, 13C, and J coupling NMR parameters. DFT calculations of 1H and 13C chemical shifts, and of the 1H homonuclear spin–spin coupling constants were performed with the mPW1PW91 functional using the 6-31G(d,p) basis set on the fully optimized geometries of all the possible stereoisomers. 相似文献