全文获取类型
收费全文 | 628篇 |
免费 | 9篇 |
国内免费 | 3篇 |
专业分类
化学 | 364篇 |
晶体学 | 7篇 |
力学 | 8篇 |
数学 | 99篇 |
物理学 | 162篇 |
出版年
2023年 | 6篇 |
2022年 | 10篇 |
2021年 | 13篇 |
2020年 | 9篇 |
2019年 | 10篇 |
2018年 | 5篇 |
2017年 | 5篇 |
2016年 | 10篇 |
2015年 | 13篇 |
2014年 | 7篇 |
2013年 | 20篇 |
2012年 | 39篇 |
2011年 | 32篇 |
2010年 | 13篇 |
2009年 | 25篇 |
2008年 | 24篇 |
2007年 | 37篇 |
2006年 | 28篇 |
2005年 | 32篇 |
2004年 | 30篇 |
2003年 | 25篇 |
2002年 | 16篇 |
2001年 | 10篇 |
2000年 | 11篇 |
1999年 | 3篇 |
1998年 | 10篇 |
1997年 | 6篇 |
1996年 | 15篇 |
1995年 | 11篇 |
1994年 | 10篇 |
1993年 | 7篇 |
1992年 | 9篇 |
1991年 | 10篇 |
1990年 | 10篇 |
1989年 | 5篇 |
1988年 | 7篇 |
1986年 | 7篇 |
1985年 | 8篇 |
1984年 | 5篇 |
1983年 | 5篇 |
1982年 | 6篇 |
1981年 | 8篇 |
1980年 | 8篇 |
1978年 | 4篇 |
1977年 | 5篇 |
1974年 | 6篇 |
1973年 | 3篇 |
1966年 | 3篇 |
1934年 | 6篇 |
1887年 | 2篇 |
排序方式: 共有640条查询结果,搜索用时 15 毫秒
31.
Recent advances in the field of catalysis for 1,3-diene polymerization and in the interpretation of the polymerization mechanism are examined. Catalysts prepared from methylaluminoxanes and soluble transition metal compounds are in general more active than the analogous systems prepared from AlR3. With some catalysts, however, (e.g. lanthanide systems) a high activity is obtained only when transition metal compounds containing preformed metal-carbon bonds are used. Methylaluminoxanes affect also the stereospecificity of the polymerization. Active and stereospecific systems are obtained from monocyclopentadienyl derivatives of Ti and aluminoxanes. Recent views on the factors that determine stereospecificity are examined. Schemes are presented for the formation of iso- or syndiotactic polymers, with 1,2, cis-1,4 or trans-1,4 structure, from various dienes. 相似文献
32.
Ercole Gattiglia Antonio Turturro Davide Ricci Annalisa Bonfiglio 《Macromolecular rapid communications》1995,16(12):919-925
The orientation of the microdomains at the free surface of solvent-cast films of a polystyrene-block-polybutadiene-block-polystyrene triblock copolymer with cyclindrical morphology was studied by coupling transmission electron and scanning force microscopies (SFM-TEM). It was found that the cylinders of polystyrene, which are assembled in grains randomly oriented in the bulk, tend to reorient with the main axis perpendicular to the surface. SFM investigation indicates that the hexagonal symmetry of the cylinders is also maintained at the free surface which is characterized by protrusions and corrugation with size and characteristic distances closely related to the cylindrical morphology visible in the bulk. Good quantitative agreement between TEM and SFM measurements is observed. 相似文献
33.
Federica Sodano Elena Gazzano Roberta Fruttero Loretta Lazzarato 《Molecules (Basel, Switzerland)》2022,27(7)
Nitric oxide is a ubiquitous signaling radical that influences critical body functions. Its importance in the cardiovascular system and the innate immune response to bacterial and viral infections has been extensively investigated. The overproduction of NO is an early component of viral infections, including those affecting the respiratory tract. The production of high levels of NO is due to the overexpression of NO biosynthesis by inducible NO synthase (iNOS), which is involved in viral clearance. The development of NO-based antiviral therapies, particularly gaseous NO inhalation and NO-donors, has proven to be an excellent antiviral therapeutic strategy. The aim of this review is to systematically examine the multiple research studies that have been carried out to elucidate the role of NO in viral infections and to comprehensively describe the NO-based antiviral strategies that have been developed thus far. Particular attention has been paid to the potential mechanisms of NO and its clinical use in the prevention and therapy of COVID-19. 相似文献
34.
J. Mispelter A. Croisy P. Jacquignon A. Ricci C. Rossi F. Schiaffela 《Tetrahedron》1977,33(18):2383-2387
The synthesis from 3-thiochromanone of indole and quinoline derivatives is reported. The structures of the compounds obtained, which are analogs of carcinogenic nitrogen polycycles, were determined by means of mass spectrometry and high resolution NMR spectrometry. In the latter case, Nuclear Overhauser Enhancements (NOE) allow the unequivocal determination of structures. Furthermore, direct (or“through space”) 1H-1H couplings are reported and related to the NOE. 相似文献
35.
Alyssa B. Sanders Jacob T. Zangaro Nakoa K. Webber Ryan P. Calhoun Elizabeth A. Richards Samuel L. Ricci Hannah M. Work Daniel D. Yang Kaitlyn R. Casey Joseph C. Iovine Gabriela Baker Taylor V. Douglas Sierra B. Dutko Thomas J. Fasano Sarah A. Lofland Ashley A. Rajan Mihaela A. Vasile Benjamin R. Carone Nathaniel V. Nucci 《Molecules (Basel, Switzerland)》2022,27(5)
Despite considerable advances in recent years, challenges in delivery and storage of biological drugs persist and may delay or prohibit their clinical application. Though nanoparticle-based approaches for small molecule drug encapsulation are mature, encapsulation of proteins remains problematic due to destabilization of the protein. Reverse micelles composed of decylmonoacyl glycerol (10MAG) and lauryldimethylamino-N-oxide (LDAO) in low-viscosity alkanes have been shown to preserve the structure and stability of a wide range of biological macromolecules. Here, we present a first step on developing this system as a future platform for storage and delivery of biological drugs by replacing the non-biocompatible alkane solvent with solvents currently used in small molecule delivery systems. Using a novel screening approach, we performed a comprehensive evaluation of the 10MAG/LDAO system using two preparation methods across seven biocompatible solvents with analysis of toxicity and encapsulation efficiency for each solvent. By using an inexpensive hydrophilic small molecule to test a wide range of conditions, we identify optimal solvent properties for further development. We validate the predictions from this screen with preliminary protein encapsulation tests. The insight provided lays the foundation for further development of this system toward long-term room-temperature storage of biologics or toward water-in-oil-in-water biologic delivery systems. 相似文献
36.
We introduce suitable exponential operators and use the multi-dimensional polynomials considered by Hermite and subsequently
studied by P. Appell and J. Kampé de Fériet, H. W. Gould and A. T. Hopper, and G. Dattoli et al. in order to obtain explicit
solutions of classical boundary-value problems with periodic data.
Translated from Sovremennaya Matematika i Ee Prilozheniya (Contemporary Mathematics and Its Applications), Vol. 51, Differential
Equations and Their Applications, 2008. 相似文献
37.
A. Jullien X. Chen A. Ricci J.-P. Rousseau R. Lopez-Martens L. P. Ramirez D. Papadopoulos A. Pellegrina F. Druon P. Georges 《Applied physics. B, Lasers and optics》2011,102(4):769-774
A 80???J, 6?fs, CEP-stable high-contrast injector is demonstrated. The device relies on standard pulse post-compression in hollow-core fiber followed by a temporal filter based on cross-polarized wave generation. Pulses with a Gaussian spectrum over 350?nm, centered at 750?nm, are generated. Temporal measurements show that the contrast of the few-cycle pulses is enhanced on a femtosecond and picosecond time scale. The carrier-envelope phase stability is preserved (0.3?rad RMS). These performances make the system an ideal seed laser for high-power, high-contrast OPCPA systems. 相似文献
38.
39.
Lombardi F Tafuri F Ricci F Miletto Granozio F Barone A Testa G Sarnelli E Kirtley JR Tsuei CC 《Physical review letters》2002,89(20):207001
We have measured the angular dependence of the Josephson critical current density (J(C)) in c-axis tilt biepitaxial grain boundary YBa(2)Cu(3)O(7-delta) junctions. We observe for the first time intrinsic d-wave pairing symmetry effects manifested as an oscillatory dependence of J(C) on angle. This intrinsic effect is evident even though spontaneous currents, possibly induced by faceting or barrier impurities, are observed in the grain boundaries. 相似文献
40.
Paolo Emilio Ricci 《Rendiconti del Circolo Matematico di Palermo》1992,41(2):185-196
A representation formula in terms of Lucas polynomials of the second kind in several variables (see formula (4.3)), for the
sum rulesJ
s
(i)
introduced by K.M. Case [1] and studied by J.S. Dehesa et al. [2]–[3] in order to obtain informations about the zeros’ distribution
of eigenfunctions of a class of ordinary polynomial differential operator, is derived.
Lavoro eseguito nell’ambito del G.N.I.M. del C.N.R. 相似文献