全文获取类型
收费全文 | 1427篇 |
免费 | 44篇 |
国内免费 | 11篇 |
专业分类
化学 | 812篇 |
晶体学 | 6篇 |
力学 | 35篇 |
数学 | 249篇 |
物理学 | 247篇 |
无线电 | 133篇 |
出版年
2023年 | 12篇 |
2022年 | 20篇 |
2021年 | 30篇 |
2020年 | 26篇 |
2019年 | 14篇 |
2018年 | 24篇 |
2017年 | 16篇 |
2016年 | 54篇 |
2015年 | 29篇 |
2014年 | 33篇 |
2013年 | 68篇 |
2012年 | 85篇 |
2011年 | 94篇 |
2010年 | 58篇 |
2009年 | 49篇 |
2008年 | 74篇 |
2007年 | 89篇 |
2006年 | 73篇 |
2005年 | 59篇 |
2004年 | 39篇 |
2003年 | 41篇 |
2002年 | 42篇 |
2001年 | 13篇 |
2000年 | 20篇 |
1999年 | 17篇 |
1998年 | 18篇 |
1997年 | 10篇 |
1996年 | 17篇 |
1995年 | 20篇 |
1994年 | 18篇 |
1993年 | 10篇 |
1992年 | 15篇 |
1991年 | 15篇 |
1990年 | 18篇 |
1989年 | 14篇 |
1988年 | 11篇 |
1987年 | 16篇 |
1986年 | 19篇 |
1985年 | 17篇 |
1984年 | 26篇 |
1983年 | 22篇 |
1982年 | 18篇 |
1981年 | 12篇 |
1980年 | 10篇 |
1979年 | 13篇 |
1978年 | 7篇 |
1976年 | 11篇 |
1975年 | 5篇 |
1974年 | 7篇 |
1972年 | 4篇 |
排序方式: 共有1482条查询结果,搜索用时 15 毫秒
151.
152.
Starting from the definitions and the properties of reinforced renewal processes and reinforced Markov renewal processes,
we characterize, via exchangeability and de Finetti’s representation theorem, a prior that consists of a family of Dirichlet
distributions on the space of Markov transition matrices and beta-Stacy processes on distribution functions. Then, we show
that this family is conjugate and give some estimate results.
相似文献
相似文献
153.
154.
Pietro Favia Victor H. Perez-Luna Thomas Boland David G. Castner Buddy D. Ratner 《Plasmas and Polymers》1996,1(4):299-326
Fluoropolymer films have been deposited in the glow and afterglow regions of radio frequency glow discharges fed with C2F6−H2 mixtures. Structure, growth rate, composition, and wettability of the films have been investigated by means of atomic force
microscopy, electron spectroscopy for chemical analysis, secondary ion mass spectrometry, and water contact angle measurements.125I labeled baboon fibrinogen in baboon plasma has been used to study the adsorption of the protein onto the films. Protein
retention, i.e., the binding affinity of the adsorbed protein, has been examined by elution with a sodium dodecyl sulfate
solution. Adsorption and retention of fibrinogen were correlated using multivariate statistical methods with the wettability,
the degree of film fluorination, and the CF
x
(1≤x≤3) group distribution of the coatings. This correlation identified the influence of each variable on the adsorption and retention
of fibrinogen onto these substrates. These variables or surface properties can be easily balanced by properly tuning the experimental
conditions of the glow discharge deposition process. 相似文献
155.
Andrea Cappelli Maurizio Anzini Salvatore Vomero Alessandro Donati Lucia Zetta Raniero Mendichi Mario Casolaro Pietro Lupetti Paolo Salvatici Gianluca Giorgi 《Journal of polymer science. Part A, Polymer chemistry》2005,43(15):3289-3304
The macromolecular and aggregate structures of poly[ethyl 1‐methylene‐3‐(4‐methylphenyl)‐1H‐indene‐2‐carboxylate] (poly‐ BF1 ; a new polymer based on a functionalized benzofulvene moiety showing interesting properties, i.e., thermoreversible polymerization/depolymerization behavior, high solubility in the most common organic solvents, and susceptibility to molecular manipulation) have been investigated with NMR spectroscopy, absorption and emission spectrophotometry, and transmission electron microscopy (TEM). Moreover, the polymerization mechanism has been studied to obtain further information on the polymer structure. The collected evidence is consistent in indicating for poly‐ BF1 a vinyl (1,2) polymer structure stabilized by means of aromatic stacking interactions. Furthermore, TEM studies performed on metal replicas have shown that the polymer is liable to give nanostructured aggregates. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3289–3304, 2005 相似文献
156.
Plasma treatments in Radio Frequency Glow Discharges fed with NH3−H2 mixtures have been performed for modifying polyethylene surfaces. Treatment kinetics and the role of species present in the
glow have been investigated. Actinometric Optical Emission Spectroscopy has been utilized as a plasma diagnostic technique.
Electron Spectroscopy for Chemical Analysis has been utilized for studying surface composition of treated substrates, which
have been examined both astreated and after derivatization of amine-functionalities with 4-trifluoromethylbenzaldehyde vapors.
It has been found that experimental plasma parameters and plasma density of active species can be controlled to achieve selective
grafting of-NH2 among all other nitrogen-containing groups. 相似文献
157.
Abdiaziz A. Farah William J. Pietro 《Journal of polymer science. Part A, Polymer chemistry》2005,43(23):6057-6072
A series of poly(N‐(ω′‐alkylcarbazoly) methacrylates) tris(bipyridine) Ru‐centered bifunctional polymers with good filming, thermal, and solubility properties were synthesized and characterized. Atom transfer radical polymerization (ATRP) of N‐(ω′‐alkylcarbazoly) methacrylates in solution was used, where Ru complexes with one and three initiating sites acted as metalloinitiators with NiBr2(PPh3)2 as a catalyst. ATRP reaction conditions with respect to polymer molecular weights and polydispersity indices (PDI) of the target bifunctional polymers were examined. Electronic absorption and emission spectra of the resultant functional polymers provided evidence of chromophore presence within a single polymeric chain. The thermal properties of all polymers were also investigated by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA), and these analyses have indicated that these polymers possess higher thermal stabilities than poly(methyl methacrylate) (PMMA) obtained via free radical polymerization. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 6057–6072, 2005 相似文献
158.
Pietro De Poi 《Mathematische Nachrichten》2005,278(4):363-378
In this article we study congruences of lines in ?n, and in particular of order one. After giving general results, we obtain a complete classification in the case of ?4 in which the fundamental surface F is in fact a variety, i.e. it is integral, and the congruence is the irreducible set of the trisecant lines of F. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
159.
Determination of cloud liquid water content using the SSM/I 总被引:2,自引:0,他引:2
Alishouse J.C. Snider J.B. Westwater E.R. Swift C.T. Ruf C.S. Snyder S.A. Vongsathorn J. Ferraro R.R. 《Geoscience and Remote Sensing, IEEE Transactions on》1990,28(5):817-822
As part of a calibration/validation effort for the Special Sensor Microwave/Imager (SSM/I), coincident observations of SSM/I brightness temperatures and surface-based observations of cloud liquid water were obtained. These observations were used to validate initial algorithms and to derive an improved algorithm. The initial algorithms were divided into latitudinal-, seasonal-, and surface-type zones. It was found that these initial algorithms, which were of the D-matrix type, did not yield sufficiently accurate results. The surface-based measurements of channels were investigated; however, the 85 V channel was excluded because of excessive noise. It was found that there is no significant correlation between the SSM/I brightness temperatures and the surface-based cloud liquid water determination when the background surface is land or snow. A high correlation was found between brightness temperatures and ground-based measurements over the ocean 相似文献
160.