全文获取类型
收费全文 | 8963篇 |
免费 | 243篇 |
国内免费 | 19篇 |
专业分类
化学 | 6074篇 |
晶体学 | 71篇 |
力学 | 201篇 |
综合类 | 5篇 |
数学 | 1041篇 |
物理学 | 1833篇 |
出版年
2023年 | 65篇 |
2022年 | 248篇 |
2021年 | 252篇 |
2020年 | 209篇 |
2019年 | 229篇 |
2018年 | 225篇 |
2017年 | 156篇 |
2016年 | 338篇 |
2015年 | 274篇 |
2014年 | 339篇 |
2013年 | 560篇 |
2012年 | 607篇 |
2011年 | 683篇 |
2010年 | 463篇 |
2009年 | 471篇 |
2008年 | 591篇 |
2007年 | 514篇 |
2006年 | 444篇 |
2005年 | 369篇 |
2004年 | 330篇 |
2003年 | 250篇 |
2002年 | 227篇 |
2001年 | 149篇 |
2000年 | 135篇 |
1999年 | 88篇 |
1998年 | 78篇 |
1997年 | 76篇 |
1996年 | 68篇 |
1995年 | 57篇 |
1994年 | 66篇 |
1993年 | 71篇 |
1992年 | 73篇 |
1991年 | 39篇 |
1990年 | 35篇 |
1989年 | 29篇 |
1988年 | 28篇 |
1987年 | 26篇 |
1986年 | 27篇 |
1985年 | 27篇 |
1984年 | 30篇 |
1983年 | 28篇 |
1982年 | 23篇 |
1981年 | 27篇 |
1980年 | 26篇 |
1979年 | 24篇 |
1978年 | 26篇 |
1977年 | 14篇 |
1976年 | 14篇 |
1975年 | 13篇 |
1973年 | 11篇 |
排序方式: 共有9225条查询结果,搜索用时 15 毫秒
21.
Jorge F. J. Coelho Ana M. F. P. Silva Anatoliy V. Popov Virgil Percec Mariana V. Abreu Pedro M. O. F. Gonalves M. H. Gil 《Journal of polymer science. Part A, Polymer chemistry》2006,44(9):3001-3008
The synthesis of a block copolymer poly(vinyl chloride)‐b‐poly(n‐butyl acrylate)‐b‐poly(vinyl chloride) is reported. This new material was synthesized by single‐electron‐transfer/degenerative‐chain‐transfer‐mediated living radical polymerization (SET‐DTLRP) in two steps. First, a bifunctional macroinitiator of α,ω‐di(iodo)poly (butyl acrylate) [α,ω‐di(iodo)PBA] was synthesized by SET‐DTLRP in water at 25 °C. The macroinitiator was further reinitiated by SET‐DTLRP, leading to the formation of the desired product. This ABA block copolymer was synthesized with high initiator efficiency. The kinetics of the copolymerization reaction was studied for two PBA macroinitiators with number–average molecular weight of 10 k and 20 k. The relationship between the conversion and the number–average molecular weight was found to be linear. The dynamic mechanical thermal analysis suggests just one phase, indicating that copolymer behaves as a single material with no phase separation. This methodology provides the access to several block copolymers and other complex architectures that result from combinations of thermoplastics (PVC) and elastomers (PBA). From industrial standpoint, this process is attractive, because of easy experimental setup and the environmental friendly reaction medium. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3001–3008, 2006 相似文献
22.
Jorge F. J. Coelho Ana M. F. P. Silva Anatoliy V. Popov Virgil Percec Mariana V. Abreu Pedro M. O. F Gonalves M. H. Gil 《Journal of polymer science. Part A, Polymer chemistry》2006,44(9):2809-2825
Living radical polymerization of n‐butyl acrylate was achieved by single electron transfer/degenerative‐chain transfer mediated living radical polymerization in water catalyzed by sodium dithionate. The plots of number–average molecular weight versus conversion and ln[M]0/[M] versus time are linear, indicating a controlled polymerization. This methodology leads to the preparation of α,ω‐di(iodo) poly (butyl acrylate) (α,ω‐di(iodo)PBA) macroinitiators. The influence of polymerization degree ([monomer]/[initiator]), amount of catalyst, concentration of suspending agents and temperature were studied. The molecular weight distributions were determined using a combination of three detectors (TriSEC): right‐angle light scattering (RALLS), a differential viscometer (DV), and refractive index (RI). The methodology studied in this work represents a possible route to prepare well‐tailored macromolecules made of butyl acrylate in an environmental friendly reaction medium. Moreover, such materials can be subsequently functionalized leading to the formation of different block copolymers of composition ABA. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2809–2825, 2006 相似文献
23.
24.
Marcos F. de Campos Marília Emura Fernando J.G. Landgraf 《Journal of magnetism and magnetic materials》2006
Electrical steels, when submitted to operation, present continuous decrease of their magnetic properties, depending on the carbon content. This effect is attributed to the increase of the size of carbides, a process also known as coarsening or Ostwald Ripening. Loss separation can offer a better understanding of this phenomenon. Experimental results show that all effect of aging is inside the hysteresis loss component, with the excess losses unaffected. The carbon content in electrical steels should be less than 25 ppm to avoid magnetic aging. 相似文献
25.
26.
27.
Song H Hecimovic S Goate A Hsu FF Bao S Vidavsky I Ramanadham S Turk J 《Journal of the American Society for Mass Spectrometry》2004,15(12):1780-1793
Dysregulation of proteolytic processing of the amyloid precursor protein (APP) contributes to the pathogenesis of Alzheimer's Disease, and the Group VIA phospholipase A(2) (iPLA(2)beta) is the dominant PLA(2) enzyme in the central nervous system and is subject to regulatory proteolytic processing. We have identified novel N-terminal variants of iPLA(2)beta and previously unrecognized proteolysis sites in APP constructs with a C-terminal 6-myc tag by automated identification of signature peptides in LC/MS/MS analyses of proteolytic digests. We have developed a Signature-Discovery (SD) program to characterize protein isoforms by identifying signature peptides that arise from proteolytic processing in vivo. This program analyzes MS/MS data from LC analyses of proteolytic digests of protein mixtures that can include incompletely resolved components in biological samples. This reduces requirements for purification and thereby minimizes artifactual modifications during sample processing. A new algorithm to generate the theoretical signature peptide set and to calculate similarity scores between predicted and observed mass spectra has been tested and optimized with model proteins. The program has been applied to the identification of variants of proteins of biological interest, including APP cleavage products and iPLA(2)beta, and such applications demonstrate the utility of this approach. 相似文献
28.
29.
A large number of nanostructures have the potential to be used together with electrophoresis as separation media or separation additive in capillary electrophoresis, micellar electrokinetic chromatography, capillary electrochromatography, and other analytical techniques. Among those structures are nanotubes, nanocavities, nanowires, nanoposts, nanocones, nanospheres, molecular imprints, nanoparachutes (conical monodendrons), and general nanoparticles with random structures. This review is focused only on publications describing experimental works using molecular imprints, nanoposts, and nanospheres that are fabricated and applied for the purpose of separation media in electrophoresis-driven separations. The review follows an approximate chronological order in each section. As shown, the most popular are those resulting from molecular imprinting technologies. These biomimetic receptors are used in a great variety of fields, which includes electrophoresis, micellar electrokinetic chromatography, capillary electrochromatography, and other fields not reviewed in this work. A few examples of these other fields are, e.g., liquid chromatography, membranes, extractor or preconcentration techniques, immunosorbent assays, and sensing devices. The second topic scanned in the present work is the nanostructures that are used as obstacles to replace gels or polymers solutions in electrophoresis. Finally, the nascent field of nanospheres of gold and other materials as separation media is also reviewed. 相似文献
30.
This paper presents a method for the energy analysis of alpha-particles emitted by transuranic elements via a novel technique
using Nuclear Tracks. The method is based on the relationship between the energy deposited in the detection material and the
diameter of the track, that is formed by chemical etching. The method involves CR-39 polycarbonate as the detector material,
one-step chemical etching after irradiation, and a digital image analysis system for automatic reading of the track diameters.
The experimental study included alpha-particles in the energy range 5.1 MeV to 5.8 MeV emitted by239Pu,241Am and244Cm. The quantitative results provide a clear signature to identify each one of the emitters based on a characteristic track
diameter. 相似文献