全文获取类型
收费全文 | 2503篇 |
免费 | 87篇 |
国内免费 | 8篇 |
专业分类
化学 | 1550篇 |
晶体学 | 25篇 |
力学 | 53篇 |
数学 | 489篇 |
物理学 | 481篇 |
出版年
2023年 | 13篇 |
2022年 | 17篇 |
2021年 | 44篇 |
2020年 | 60篇 |
2019年 | 54篇 |
2018年 | 26篇 |
2017年 | 34篇 |
2016年 | 78篇 |
2015年 | 67篇 |
2014年 | 78篇 |
2013年 | 135篇 |
2012年 | 165篇 |
2011年 | 151篇 |
2010年 | 91篇 |
2009年 | 90篇 |
2008年 | 138篇 |
2007年 | 158篇 |
2006年 | 147篇 |
2005年 | 122篇 |
2004年 | 106篇 |
2003年 | 94篇 |
2002年 | 71篇 |
2001年 | 44篇 |
2000年 | 25篇 |
1999年 | 17篇 |
1998年 | 15篇 |
1997年 | 33篇 |
1996年 | 21篇 |
1995年 | 20篇 |
1994年 | 38篇 |
1993年 | 38篇 |
1992年 | 37篇 |
1991年 | 29篇 |
1989年 | 11篇 |
1988年 | 10篇 |
1987年 | 20篇 |
1986年 | 16篇 |
1985年 | 18篇 |
1984年 | 19篇 |
1983年 | 23篇 |
1982年 | 20篇 |
1981年 | 16篇 |
1980年 | 19篇 |
1979年 | 11篇 |
1978年 | 23篇 |
1977年 | 22篇 |
1976年 | 15篇 |
1975年 | 16篇 |
1974年 | 17篇 |
1972年 | 8篇 |
排序方式: 共有2598条查询结果,搜索用时 15 毫秒
1.
Marcus Carlsson 《Expositiones Mathematicae》2021,39(1):149-157
von Neumann’s inequality in matrix theory refers to the fact that the Frobenius scalar product of two matrices is less than or equal to the scalar product of the respective singular values. Moreover, equality can only happen if the two matrices share a joint set of singular vectors, and this latter part is hard to find in the literature. We extend these facts to the separable Hilbert space setting, and provide a self-contained proof of the “latter part”. 相似文献
2.
Kleandrova Valeria V. Rojas-Vargas Julio A. Scotti Marcus T. Speck-Planche Alejandro 《Molecular diversity》2022,26(5):2523-2534
Molecular Diversity - Hypertension is a medical condition that affects millions of people worldwide. Despite the high efficacy of the current antihypertensive drugs, they are associated with... 相似文献
3.
Diego Fontana de Andrade Louise Jank Vitor Breda Rego Roberto Minozzo Marcus Vinícius Burgel Sfoggia Álvaro Bavaresco Fabiano Barreto 《Biomedical chromatography : BMC》2020,34(9):e4873
Saponins from Quillaja saponaria have been commonly used as immunomodulatory adjuvants in foot-and-mouth disease vaccines (FMDVs). However, due to the lack of consensus over the possible exacerbation of local inflammatory responses in cattle and its economic impacts, their use has been discouraged by Brazilian authorities. A qualitative method intended to determine the presence of saponins from Q. saponaria bark extracts in FMDVs was developed and validated. Instrumental analysis was performed using an liquid chromatography (LC) coupled to a quadrupole–time-of-flight–mass spectrometry (TOF-MS) system. The method was validated according to the International Conference on Harmonization Harmonized Tripartite Guideline Q2 (R1) and Brazilian Ministry of Agriculture, Livestock and Food Supply Analytical Quality Assurance Guidelines. Validation parameters were determined and considered suitable to the established criteria. The validated method has been applied in routine analysis in the National Agricultural Laboratory at Rio Grande do Sul (LANAGRO-RS). All results obtained were in agreement with the vaccine's composition described by the manufacturer. The method is easy and adequate for analysis in routine laboratories. To the best of the authors' knowledge, this is the first report of a method which intends to investigate the presence of saponins from Q. saponaria bark extracts in veterinary vaccines. 相似文献
4.
5.
Kylie B. Manning Alexander G. Shtukenberg Shane M. Nichols Bart Kahr Marcus Weck 《Journal of polymer science. Part A, Polymer chemistry》2015,53(22):2563-2568
N‐(Bis(4‐(2‐ethylhexyloxy)phenyl)(phenyl)‐methyl)methacrylamide was synthesized and polymerized via reversible addition‐fragmentation chain‐transfer (RAFT) polymerization. The chain‐transfer agent (4‐cyano‐4‐(phenylcarbonothioylthio) pentanoic acid (CPADB)), combined with a chiral additive, and a radical initiator yielded polymers with dispersities between 1.2 and 1.4. At low concentrations, the polymers are soluble in hexanes and chloroform while at higher concentrations they swell in these solvents. Characterization of the polymers by wide‐angle X‐ray scattering (WAXS) revealed an interplanar distance of 19.0 Å. The WAXS data combined with polarized optical microscopy support a lamellar crystallization and lyotropic liquid crystalline behavior in hexanes and chloroform. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 2563–2568 相似文献
6.
7.
8.
Daniel Loof Oliver Thüringer Dr. Marco Schowalter Dr. Christoph Mahr Anmona Shabnam Pranti Prof. Dr. Walter Lang Prof. Dr. Andreas Rosenauer Dr. Volkmar Zielasek Dr. Sebastian Kunz Prof. Dr. Marcus Bäumer 《ChemistryOpen》2021,10(7):697-712
Porous networks of Pt nanoparticles interlinked by bifunctional organic ligands have shown high potential as catalysts in micro-machined hydrogen gas sensors. By varying the ligand among p-phenylenediamine, benzidine, 4,4‘‘-diamino-p-terphenyl, 1,5-diaminonaphthalene, and trans-1,4-diaminocyclohexane, new variants of such networks were synthesized. Inter-particle distances within the networks, determined via transmission electron microscopy tomography, varied from 0.8 to 1.4 nm in accordance with the nominal length of the respective ligand. While stable structures with intact and coordinatively bonded diamines were formed with all ligands, aromatic diamines showed superior thermal stability. The networks exhibited mesoporous structures depending on ligand and synthesis strategy and performed well as catalysts in hydrogen gas microsensors. They demonstrate the possibility of deliberately tuning micro- and mesoporosity and thereby transport properties and steric demands by choice of the right ligand also for other applications in heterogeneous catalysis. 相似文献
9.
Prof. Marcus W. Drover Maeve C. Dufour Lindsay A. Lesperance-Nantau Rayni P. Noriega Dr. Kirill Levin Prof. Robert W. Schurko 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(49):11180-11186
Herein, we establish the preparation, characterization, and reactivity of a new diphosphine ligand, 1,2-bis(di(3-dicyclohexylboraneyl)propylphosphino)ethane (P2BCy4), a scaffold that contains four pendant boranes. An entryway into the coordination chemistry of P2BCy4 is established by using nickel, providing the octaboraneyl complex [Ni(P2BCy4)2]—this species contains a boron-rich secondary coordination sphere that reacts readily with Lewis bases. In the case of 4,4′-bipyridine, an air-sensitive coordination polymer is obtained. Characterization of this material by solid-state NMR and EPR spectroscopy reveals the presence of a charge-transfer polymer, which forms as a function of intramolecular Ni→4,4′-bpy electron transfer (ET), providing an array of oxidized nickel sites and reduced 4,4′-bpy radical anion sites. Notably, the related intermolecular reaction between the model fragments [Ni(dnppe)2] (dnppe=1,2-bis(di-n-propylphosphino)ethane) and a bis(boraneyl)-protected 4,4′-bpy, provides no ET. Overall, the P2BCy4 fragment provides a unique opportunity for Lewis base activation, in one case allowing for the facile construction of monomers for incorporation into redox-active macromolecules. 相似文献
10.
Lucas Ueberricke Ioana Ciubotaru Farhad Ghalami Felix Mildner Dr. Frank Rominger Prof. Dr. Marcus Elstner Prof. Dr. Michael Mastalerz 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(50):11634-11642
Five di- and tetracyano-substituted pyrene-fused pyrazaacenes were synthesized and studied as potential electron acceptors in the solid state. Single crystals of all compounds were grown and the crystal packing studied by DFT calculations (transfer integrals and reorganization energies) to get insight into possible use for semiconducting charge transport. 相似文献