全文获取类型
收费全文 | 6317篇 |
免费 | 207篇 |
国内免费 | 26篇 |
专业分类
化学 | 4461篇 |
晶体学 | 39篇 |
力学 | 176篇 |
数学 | 964篇 |
物理学 | 910篇 |
出版年
2024年 | 6篇 |
2023年 | 57篇 |
2022年 | 187篇 |
2021年 | 201篇 |
2020年 | 162篇 |
2019年 | 158篇 |
2018年 | 115篇 |
2017年 | 116篇 |
2016年 | 253篇 |
2015年 | 213篇 |
2014年 | 223篇 |
2013年 | 331篇 |
2012年 | 401篇 |
2011年 | 494篇 |
2010年 | 280篇 |
2009年 | 258篇 |
2008年 | 388篇 |
2007年 | 364篇 |
2006年 | 366篇 |
2005年 | 336篇 |
2004年 | 309篇 |
2003年 | 247篇 |
2002年 | 210篇 |
2001年 | 79篇 |
2000年 | 71篇 |
1999年 | 75篇 |
1998年 | 48篇 |
1997年 | 52篇 |
1996年 | 78篇 |
1995年 | 48篇 |
1994年 | 46篇 |
1993年 | 39篇 |
1992年 | 48篇 |
1991年 | 39篇 |
1990年 | 23篇 |
1989年 | 22篇 |
1988年 | 13篇 |
1987年 | 16篇 |
1986年 | 18篇 |
1985年 | 24篇 |
1984年 | 21篇 |
1983年 | 22篇 |
1982年 | 16篇 |
1981年 | 12篇 |
1980年 | 14篇 |
1979年 | 17篇 |
1977年 | 8篇 |
1976年 | 4篇 |
1975年 | 3篇 |
1906年 | 2篇 |
排序方式: 共有6550条查询结果,搜索用时 0 毫秒
11.
Andrea Loi 《Differential Geometry and its Applications》2006,24(3):311-319
In this paper we study the Calabi diastasis function of Hermitian symmetric spaces. This allows us to prove that if a complete Hermitian locally symmetric space (M,g) admits a Kähler immersion into a globally symmetric space (S,G) then it is globally symmetric and the immersion is injective. Moreover, if (S,G) is symmetric of a specified type (Euclidean, noncompact, compact), then (M,g) is of the same type. We also give a characterization of Hermitian globally symmetric spaces in terms of their diastasis function. Finally, we apply our analysis to study the balanced metrics, introduced by Donaldson, in the case of locally Hermitian symmetric spaces. 相似文献
12.
Michelina Soccio Lara Finelli Nadia Lotti Valentina Siracusa Tiberio A. Ezquerra Andrea Munari 《Journal of Polymer Science.Polymer Physics》2007,45(13):1694-1703
Poly(butylene naphthalate) (PBN), poly(diethylene naphthalate) (PDEN), and poly(thiodiethylene naphthalate) (PTDEN) were synthesized and characterized in terms of chemical structure and molecular weight. The polyesters were examined by TGA, DSC, and DMTA. All the polymers showed a good thermal stability, even though depending on chemical structure. At room temperature they appeared as semicrystalline materials; the effect of the introduction along the PBN polymer chain of ether oxygen atoms or sulfur ones was a lowering in the Tg value, a decrement of Tm, and a decrease of the crystallization rate. Changing in chemical structure also affects the main α absorption associated with the glass transition which moves to lower temperature and whose energetic requirements decrease. The results were explained as due to the presence of highly flexible C? S? C or C? O? C bonds in the polymeric chain. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 1694–1703, 2007 相似文献
13.
14.
Michaël Lejeune Andrea Valsesia Martin Kormunda Pascal Colpo François Rossi 《Surface science》2005,583(1):L142
In this work, chemically and topographically nanopatterned surfaces were produced by a top-down processing approach for biosensing devices. The nanopatterning was the result of the combination of plasma polymerisation (pp) of biofunctional materials and colloidal lithography techniques. The morphological and chemical properties induced by the plasma deposition-etching treatment were characterised by optical method combining ellipsometry and Fourier Transform Infrared spectroscopy studies. This method supported by atomic force microscopy measurements, allowed the full optical characterization of each step of the top-down process. The optical characterization of the end-up nanopatterned samples demonstrated that the chosen process is able to produce well-defined nanostructured surfaces with controlled chemical and morphological properties. 相似文献
15.
16.
A line bundle on a complex projective manifold is said to be lef if one of its powers is globally generated and defines a semismall map in the sense of Goresky-MacPherson. As in the case of ample bundles the first Chern class of lef line bundles satisfies the Hard Lefschetz Theorem and the Hodge-Riemann Bilinear Relations. As a consequence, we prove a generalization of the Grauert contractibility criterion: the Hodge Index Theorem for semismall maps, Theorem 2.4.1. For these maps the Decomposition Theorem of Beilinson, Bernstein and Deligne is equivalent to the non-degeneracy of certain intersection forms associated with a stratification. This observation, joint with the Hodge Index Theorem for semismall maps gives a new proof of the Decomposition Theorem for the direct image of the constant sheaf. A new feature uncovered by our proof is that the intersection forms involved are definite. 相似文献
17.
Andrea Hubacher 《Communications in Mathematical Physics》1989,123(3):353-375
We discuss various scattering properties of the classical system ofn repelling particles on the real line. In the integrable case, i.e. if the asymptotic velocities are preserved under the scattering map, the asymptotic phases behave as if the particles collided pairwise. 相似文献
18.
A micro-reactor system with continual spectrophotometric detection has been operated in Sequential Injection lab-on-valve (SI-LOV) mode and applied to enzyme kinetics and inhibition studies, using acetylcholinesterase (AChE) and angiotensin-converting enzyme (ACE) as model systems. With the advantages of automation, real-time kinetic measurement, and thorough mixing, the SI-LOV micro-reactor system allows for the monitoring of initial reaction rates and determination of reactant concentrations in the reaction mixture, both of which are essential for the determination of kinetic constants for enzymes and inhibitors. Enzyme, substrate, and inhibitor are precisely metered by the syringe pump and delivered to a stirred micro-reactor, followed by a reference scan that establishes the baseline for the following reaction rate measurement. Michaelis constants (Km) for AChE and ACE were determined to be 0.16 mM and 0.30 mM, respectively, which are consistent with literature values. The type of inhibition (competitive, uncompetitive, or mixed), the dissociation constants for the inhibitors, and the inhibitor dose-response curves were also determined. 相似文献
19.
The self‐complementary tetrameric propargyl triols 8, 14, 18 , and 21 were synthesized to investigate the duplex formation of self‐complementary, ethynylene‐linked UUAA, AAUU, UAUA, and AUAU analogues with integrated bases and backbone (ONIBs). The linear synthesis is based on repetitive Sonogashira couplings and C‐desilylations (34–72% yield), starting from the monomeric propargyl alcohols 9 and 15 and the iodinated nucleosides 3, 7, 11 , and 13 . Strongly persistent intramolecular H‐bonds from the propargylic OH groups to N(3) of the adenosine units prevent the gg‐type orientation of the ethynyl groups at C(5′). As such, an orientation is required for the formation of cyclic duplexes, this H‐bond prevents the formation of duplexes connected by all four base pairs. However, the central units of the UAUA and AAUU analogues 18 and 14 associate in CDCl3/(D6)DMSO 10 : 1 to form a cyclic duplex characterized by reverse Hoogsteen base pairing. The UUAA tetramer 8 forms a cyclic UU homoduplex, while the AUAU tetramer 21 forms only linear associates. Duplex formation of the O‐silylated UUAA and AAUU tetramers is no longer prevented. The self‐complementary UUAA tetramer 22 forms Watson–Crick‐ and Hoogsteen‐type base‐paired cyclic duplexes more readily than the sequence‐isomeric AAUU tetramer 23 , further illustrating the sequence selectivity of duplex formation. 相似文献
20.
For ν≥0 let cνk be the k-th positive zero of the cylinder functionC v(t)=J v(t)cosα-Y v(t)sinα, 0≤α>π whereJ ν(t) andY ν(t) denote the Bessel functions of the first and the second kind, respectively. We prove thatC v,k 1+H(x) is convex as a function of ν, ifc νk≥x>0 and ν≥0, whereH(x) is specified in Theorem 1.1. 相似文献