全文获取类型
收费全文 | 298770篇 |
免费 | 2720篇 |
国内免费 | 677篇 |
专业分类
化学 | 142120篇 |
晶体学 | 4207篇 |
力学 | 11938篇 |
综合类 | 9篇 |
数学 | 29543篇 |
物理学 | 82855篇 |
无线电 | 31495篇 |
出版年
2019年 | 2513篇 |
2018年 | 3391篇 |
2017年 | 3351篇 |
2016年 | 4821篇 |
2015年 | 2802篇 |
2014年 | 4648篇 |
2013年 | 11290篇 |
2012年 | 8488篇 |
2011年 | 10428篇 |
2010年 | 7628篇 |
2009年 | 7807篇 |
2008年 | 10510篇 |
2007年 | 11009篇 |
2006年 | 10248篇 |
2005年 | 9439篇 |
2004年 | 8752篇 |
2003年 | 7957篇 |
2002年 | 7891篇 |
2001年 | 8488篇 |
2000年 | 6852篇 |
1999年 | 5418篇 |
1998年 | 4949篇 |
1997年 | 4910篇 |
1996年 | 4524篇 |
1995年 | 4249篇 |
1994年 | 4347篇 |
1993年 | 4031篇 |
1992年 | 4448篇 |
1991年 | 4516篇 |
1990年 | 4379篇 |
1989年 | 4159篇 |
1988年 | 4184篇 |
1987年 | 3821篇 |
1986年 | 3616篇 |
1985年 | 4700篇 |
1984年 | 4986篇 |
1983年 | 4170篇 |
1982年 | 4270篇 |
1981年 | 4201篇 |
1980年 | 4144篇 |
1979年 | 4082篇 |
1978年 | 4392篇 |
1977年 | 4310篇 |
1976年 | 4373篇 |
1975年 | 4015篇 |
1974年 | 4093篇 |
1973年 | 4245篇 |
1972年 | 3010篇 |
1971年 | 2501篇 |
1970年 | 2307篇 |
排序方式: 共有10000条查询结果,搜索用时 681 毫秒
21.
Clemens G. Raab Georg Regensburger Jamal Hossein Poor 《Journal of Pure and Applied Algebra》2021,225(5):106564
A formal computation proving a new operator identity from known ones is, in principle, restricted by domains and codomains of linear operators involved, since not any two operators can be added or composed. Algebraically, identities can be modelled by noncommutative polynomials and such a formal computation proves that the polynomial corresponding to the new identity lies in the ideal generated by the polynomials corresponding to the known identities. In order to prove an operator identity, however, just proving membership of the polynomial in the ideal is not enough, since the ring of noncommutative polynomials ignores domains and codomains. We show that it suffices to additionally verify compatibility of this polynomial and of the generators of the ideal with the labelled quiver that encodes which polynomials can be realized as linear operators. Then, for every consistent representation of such a quiver in a linear category, there exists a computation in the category that proves the corresponding instance of the identity. Moreover, by assigning the same label to several edges of the quiver, the algebraic framework developed allows to model different versions of an operator by the same indeterminate in the noncommutative polynomials. 相似文献
22.
Kuz’mina L. G. Navasardyan M. A. Kalle P. Bezzubov S. I. 《Crystallography Reports》2021,66(3):420-423
Crystallography Reports - The crystal and molecular structures of Cl–C6H4–O–C16H33 (I) have been studied, and its differential scanning calorimetry (DSC) study is performed.... 相似文献
23.
24.
Wireless Networks - Orthogonal frequency-division multiplexing with random multiple access (OFDRMA) is discussed for down-link communications, whereby a single base-station transmits information... 相似文献
25.
26.
27.
Smirnova T. D. Zhelobitskaya E. A. Danilina T. G. 《Journal of Analytical Chemistry》2022,77(8):1000-1004
Journal of Analytical Chemistry - Silver nanoparticles modified with Eu3+ ions increase the intensity of the fluorescence signal by a factor of 125 in an analytical system containing doxycycline as... 相似文献
28.
Daulbaev O. Isaenko L. I. Bogdzel’ A. A. Lobanov S. I. Krinitsyn P. G. Milkov V. M. Belushkin A. V. 《Crystallography Reports》2022,67(3):464-469
Crystallography Reports - Two LiInSe2 single crystals, grown under different conditions, have been studied. Characteristics of these crystals for neutron detection have been compared using... 相似文献
29.
Dzhun I. O. Babaitsev G. V. Kozin M. G. Romashkina I. L. Shanova E. I. Chechenin N. G. 《Physics of the Solid State》2021,63(6):825-831
Physics of the Solid State - The external factors which influence the ferromagnetic resonance (FMR) line width in bilayer (ferromagnet/antiferromagnet) exchange-biased systems are studied. The... 相似文献
30.
Young Been Kim Sung Hyeon Jung Dong Su Kim Nishad G. Deshpande Hee Won Suh Hak Hyeon Lee Ji Hoon Choi Ho Seong Lee Hyung Koun Cho 《Advanced functional materials》2021,31(38):2102439
Antimony triselenide (Sb2Se3) nanoflake-based nitrogen dioxide (NO2) sensors exhibit a progressive bifunctional gas-sensing performance, with a rapid alarm for hazardous highly concentrated gases, and an advanced memory-type function for low-concentration (<1 ppm) monitoring repeated under potentially fatal exposure. Rectangular and cuboid shaped Sb2Se3 nanoflakes, comprising van der Waals planes with large surface areas and covalent bond planes with small areas, can rapidly detect a wide range of NO2 gas concentrations from 0.1 to 100 ppm. These Sb2Se3 nanoflakes are found to be suitable for physisorption-based gas sensing owing to their anisotropic quasi-2D crystal structure with extremely enlarged van der Waals planes, where they are humidity-insensitive and consequently exhibit an extremely stable baseline current. The Sb2Se3 nanoflake sensor exhibits a room-temperature/low-voltage operation, which is noticeable owing to its low energy consumption and rapid response even under a NO2 gas flow of only 1 ppm. As a result, the Sb2Se3 nanoflake sensor is suitable for the development of a rapid alarm system. Furthermore, the persistent gas-sensing conductivity of the sensor with a slow decaying current can enable the development of a progressive memory-type sensor that retains the previous signal under irregular gas injection at low concentrations. 相似文献