全文获取类型
收费全文 | 1801篇 |
免费 | 23篇 |
国内免费 | 10篇 |
专业分类
化学 | 980篇 |
晶体学 | 11篇 |
力学 | 61篇 |
数学 | 232篇 |
物理学 | 550篇 |
出版年
2020年 | 15篇 |
2018年 | 13篇 |
2016年 | 14篇 |
2015年 | 18篇 |
2014年 | 22篇 |
2013年 | 87篇 |
2012年 | 81篇 |
2011年 | 87篇 |
2010年 | 56篇 |
2009年 | 23篇 |
2008年 | 54篇 |
2007年 | 78篇 |
2006年 | 54篇 |
2005年 | 59篇 |
2004年 | 61篇 |
2003年 | 56篇 |
2002年 | 55篇 |
2001年 | 36篇 |
2000年 | 52篇 |
1999年 | 33篇 |
1998年 | 24篇 |
1997年 | 26篇 |
1996年 | 39篇 |
1995年 | 31篇 |
1994年 | 33篇 |
1993年 | 37篇 |
1992年 | 32篇 |
1991年 | 36篇 |
1990年 | 28篇 |
1989年 | 18篇 |
1988年 | 22篇 |
1987年 | 21篇 |
1986年 | 23篇 |
1985年 | 22篇 |
1984年 | 20篇 |
1983年 | 15篇 |
1982年 | 18篇 |
1981年 | 24篇 |
1980年 | 28篇 |
1979年 | 41篇 |
1978年 | 24篇 |
1977年 | 23篇 |
1976年 | 27篇 |
1975年 | 19篇 |
1974年 | 34篇 |
1973年 | 32篇 |
1972年 | 14篇 |
1971年 | 16篇 |
1970年 | 15篇 |
1969年 | 16篇 |
排序方式: 共有1834条查询结果,搜索用时 953 毫秒
991.
992.
993.
994.
R.C. Fernow S.W. Gray A.D. Krisch H.E. Miettinen J.B. Roberts K.M. Terwilliger W. DeBoer E.F. Parker L.G. Ratner J.R. OFallon 《Physics letters. [Part B]》1974,52(2):243-246
The elastic cross section for proton proton scattering at 6 was measured using a 70% polarized beam and a 75% polarized target at the Argonne ZGS. In the range we obtained small error measurements for the ↑↑, ↓↓ and ↑↓ initial spin states perpendicular to the scattering plane. At P⊥2 = 0.5 we also measured the recoil spin and found that the 5 different cross sections were very unequal. 相似文献
995.
The noise-decoupled nitrogen-15 NMR spectra of ten pyridine N-oxides and two quinoline N-oxides have been obtained at the natural-abundance level by high-resolution NMR spectroscopy. Substituents at the 4-ring position of pyridine N-oxide, capable of resonance interaction with the N-O moiety, give fairly large shifts in the expected directions. Spectra taken in dimethyl sulfoxide solution give 5–20 ppm and 33–55 ppm downfield shifts with respect to the solutions of the same substances in 2,2,2-trifluoroethanol and trifluoroacetic acid. Solvent influences are discussed in terms of hydrogen bonding and protonation of the N-oxide oxygen. Carbon-13 chemical shifts and one-bond carbon-hydrogen coupling constants of some substituted pyridine N-oxides are reported and discussed. 相似文献
996.
Patel AB Allen S Davies MC Roberts CJ Tendler SJ Williams PM 《Journal of the American Chemical Society》2004,126(5):1318-1319
The strength of a multimolecular system depends on the number of interactions that hold it together. Using dynamic force spectroscopy, we show how the kinetic stability of a system decreases as the number of molecular bonds is increased, as predicted by theory. The data raise important considerations for experimental tests of bond strength and, as a paradigm, suggest both routes to and pitfalls in methods for computational simulation of molecular transitions, such as ligand binding and protein folding. 相似文献
997.
We give a pedagogical survey of those aspects of the abstract representation theory of quantum groups which are related to the Tannaka–Krein reconstruction problem. We show that every concrete semisimple tensor *-category with conjugates is equivalent to the category of finite-dimensional nondegenerate *-representations of a discrete algebraic quantum group. Working in the self-dual framework of algebraic quantum groups, we then relate this to earlier results of S. L. Woronowicz and S. Yamagami. We establish the relation between braidings and R-matrices in this context. Our approach emphasizes the role of the natural transformations of the embedding functor. Thanks to the semisimplicity of our categories and the emphasis on representations rather than corepresentations, our proof is more direct and conceptual than previous reconstructions. As a special case, we reprove the classical Tannaka–Krein result for compact groups. It is only here that analytic aspects enter, otherwise we proceed in a purely algebraic way. In particular, the existence of a Haar functional is reduced to a well-known general result concerning discrete multiplier Hopf *-algebras. 相似文献
998.
We investigate group actions on simply-connected (second countable but not necessarily Hausdorff) 1-manifolds and describe an infinite family of closed hyperbolic 3-manifolds whose fundamental groups do not act nontrivially on such 1-manifolds. As a corollary we conclude that these 3-manifolds contain no Reebless foliation. In fact, these arguments extend to actions on oriented -order trees and hence these 3-manifolds contain no transversely oriented essential lamination; in particular, they are non-Haken.
999.
P. Maris A. Raya C. D. Roberts S. M. Schmidt 《The European Physical Journal A - Hadrons and Nuclei》2003,18(2-3):231-235
The gap equation is a cornerstone in understanding dynamical chiral symmetry breaking and may also provide clues to confinement. A symmetry-preserving truncation of its kernel enables proofs of important results and the development of an efficacious phenomenology. We describe a model of the kernel that yields: a momentum-dependent dressed-quark propagator in fair agreement with quenched lattice-QCD results; and chiral limit values,
MeV and
. It is compared with models inferred from studies of the gauge sector.Received: 30 September 2002, Published online: 22 October 2003PACS:
12.38.Aw General properties of QCD (dynamics, confinement, etc.) - 11.30.Rd Chiral symmetries 相似文献
1000.
Smalyuk VA Radha PB Delettrez JA Glebov VY Goncharov VN Meyerhofer DD Regan SP Roberts S Sangster TC Soures JM Stoeckl C Frenje JA Li CK Petrasso RD Séguin FH 《Physical review letters》2003,90(13):135002
The temporal history of the target areal-density near peak compression of direct-drive spherical target implosions has been inferred with 14.7-MeV deuterium-helium-3 D3He proton spectroscopy of the 60-beam, 30-kJ UV OMEGA laser system. The target areal-density grows by a factor of approximately 8 during the time of neutron-production ( approximately 400 ps) before reaching 123+/-16 mg/cm(2) at peak compression in the implosion of a 950-micrometer-diam, 20-micrometer-thick plastic CH capsule filled with 4 atm of D3He fuel. 相似文献