全文获取类型
收费全文 | 692篇 |
免费 | 22篇 |
国内免费 | 11篇 |
专业分类
化学 | 524篇 |
晶体学 | 3篇 |
力学 | 3篇 |
数学 | 140篇 |
物理学 | 55篇 |
出版年
2023年 | 5篇 |
2022年 | 25篇 |
2021年 | 23篇 |
2020年 | 15篇 |
2019年 | 17篇 |
2018年 | 11篇 |
2017年 | 19篇 |
2016年 | 28篇 |
2015年 | 15篇 |
2014年 | 25篇 |
2013年 | 55篇 |
2012年 | 37篇 |
2011年 | 61篇 |
2010年 | 40篇 |
2009年 | 27篇 |
2008年 | 46篇 |
2007年 | 39篇 |
2006年 | 40篇 |
2005年 | 25篇 |
2004年 | 23篇 |
2003年 | 24篇 |
2002年 | 21篇 |
2001年 | 10篇 |
2000年 | 10篇 |
1999年 | 14篇 |
1998年 | 9篇 |
1997年 | 7篇 |
1996年 | 3篇 |
1995年 | 2篇 |
1994年 | 6篇 |
1993年 | 2篇 |
1992年 | 6篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1989年 | 3篇 |
1986年 | 1篇 |
1984年 | 1篇 |
1982年 | 4篇 |
1980年 | 6篇 |
1979年 | 3篇 |
1978年 | 2篇 |
1977年 | 2篇 |
1976年 | 1篇 |
1973年 | 1篇 |
1972年 | 2篇 |
1970年 | 1篇 |
1966年 | 1篇 |
1965年 | 1篇 |
1937年 | 2篇 |
1931年 | 1篇 |
排序方式: 共有725条查询结果,搜索用时 15 毫秒
31.
Leite Irena Andrianov Victor Zelencova-Gopejenko Diana Loza Einars Kazhoka-Lapsa Iveta Domracheva Ilona Stojak Marta Chlopicki Stefan Kalvins Ivars 《Chemistry of Heterocyclic Compounds》2021,57(12):1235-1235
Chemistry of Heterocyclic Compounds - 相似文献
32.
Bishnu P. Biswal Sreeramulu Valligatla Mingchao Wang Tanmay Banerjee Nabil A. Saad Bala Murali Krishna Mariserla Naisa Chandrasekhar Daniel Becker Matthew Addicoat Irena Senkovska Reinhard Berger D. Narayana Rao Stefan Kaskel Xinliang Feng 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(21):6970-6974
Covalent organic frameworks (COFs) have garnered immense scientific interest among porous materials because of their structural tunability and diverse properties. However, the response of such materials toward laser‐induced nonlinear optical (NLO) applications is hardly understood and demands prompt attention. Three novel regioregular porphyrin (Por)‐based porous COFs—Por‐COF‐HH and its dual metalated congeners Por‐COF‐ZnCu and Por‐COF‐ZnNi—have been prepared and present excellent NLO properties. Notably, intensity‐dependent NLO switching behavior was observed for these Por‐COFs, which is highly desirable for optical switching and optical limiting devices. Moreover, the efficient π‐conjugation and charge‐transfer transition in ZnCu‐Por‐COF enabled a high nonlinear absorption coefficient (β=4470 cm/GW) and figure of merit (FOM=σ1/σo, 3565) value compared to other state‐of‐the‐art materials, including molecular porphyrins (β≈100–400 cm/GW), metal–organic frameworks (MOFs; β≈0.3–0.5 cm/GW), and graphene (β=900 cm/GW). 相似文献
33.
A combination of "black box" and "calendar-time" methods for the determination of calibration intervals of an analytical
measuring instrument is discussed. Since the methods require information on the distributions of the calibration parameters,
such information is described for an atomic absorption spectrophotometer, as an example. The hypotheses on the normal distribution
of the calibration parameters are tested using the ω2-criterion and accepted at 0.90–0.95 levels of confidence. Corresponding control charts are designed for indication of warning
and action limits of the calibration parameters, and diagnoses of outliers in further calibrations. Control charts indicate
also when the calibration should be done according to the full program of the equipment manufacturer.
Received: 15 April 2000 / Accepted: 24 July 2000 相似文献
34.
Dr. Yaoyu Liang Dr. Irena Efremenko Dr. Yael Diskin-Posner Dr. Liat Avram Prof. Dr. David Milstein 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2024,136(21):e202401702
Bond activation and catalysis using s-block metals are of great significance. Herein, a series of calcium pincer complexes with deprotonated side arms have been prepared using pyridine-based PNP and PNN ligands. The complexes were characterized by NMR and X-ray crystal diffraction. Utilizing the obtained calcium complexes, unprecedented N2O activation by metal-ligand cooperation (MLC) involving dearomatization-aromatization of the pyridine ligand was achieved, generating aromatized calcium diazotate complexes as products. Additionally, the dearomatized calcium complexes were able to activate the N−H bond as well as reversibly activate H2, offering an opportunity for the catalytic hydrogenation of various unsaturated molecules. DFT calculations were applied to analyze the electronic structures of the synthesized complexes and explore possible reaction mechanisms. This study is an important complement to the area of MLC and main-group metal chemistry. 相似文献
35.
ABSTRACTHere we report on the synthesis and mesomorphic properties of a series of imino-linked dimeric molecules. In order to improve our understanding of the structure–NTB phase correlations, we have studied the impact of geometric and electronic factors arising from varying mesogenic units, different spacer lengths and from the ratio (n/m) between the lengths of terminal chains (n) and spacer (m). From the perspective of the molecular geometry, the results show that the stability of the NTB phase results from increasing effective molecular bending and with the broadening of the mesogenic unit, in particular near the spacer, and that the n/m ratio plays a substantial role in conjunction with the specific mesogenic unit. A computational study of the electronic properties shows that a broadening of the mesogenic core in the vicinity of the spacer is associated with an increased anisotropy of the electrostatic potential distribution. Within a given series of materials our study suggests that the incidence of the NTB phase and its thermal stability are governed by the synergy of specific geometrical factors and the anisotropy of the electrostatic potential distribution of the mesogenic core. 相似文献
36.
Enhancement of the Efficacy of Photodynamic Inactivation of Candida albicans with the Use of Biogenic Gold Nanoparticles 下载免费PDF全文
Irena Maliszewska Barbara Lisiak Katarzyna Popko Katarzyna Matczyszyn 《Photochemistry and photobiology》2017,93(4):1081-1090
This study reports on successful photodynamic inactivation of planktonic and biofilm cells of Candida albicans using Rose Bengal (RB) in combination with biogenic gold nanoparticles synthesized by the cell‐free filtrate of Penicillium funiculosum BL1 strain. Monodispersed colloidal gold nanoparticles coated with proteins were characterized by a number of techniques including SEM–EDS, TEM, UV–Vis absorption and fluorescence spectroscopy, as well as Fourier transform infrared spectroscopy to be 24 ± 3 nm spheres. A Xe lamp (output power of 20mW, delivering intensity of 53 mW cm?2) was used as a light source to study the effects of RB alone, the gold nanoparticles alone and the RB‐gold nanoparticle mixture on the viability of C. albicans cells. The most effective reduction in the number of planktonic cells was found after 30 min of Xe lamp light irradiation (95.4 J cm?2) and was 4.89 log10 that is 99.99% kill for the mixture of RB with gold nanoparticles compared with 2.19 log10 or 99.37% for RB alone. The biofilm cells were more resistant to photodynamic inactivation, and the highest effective reduction in the number of cells was found after 30 min of irradiation in the presence of the RB–gold nanoparticles mixture and was 1.53 log10, that is 97.04% kill compared with 0.6 log10 or 74.73% for RB. The probable mechanism of enhancement of RB‐mediated photodynamic fungicidal efficacy against C. albicans in the presence of biogenic gold nanoparticles is discussed leading to the conclusion that this process may have a multifaceted character. 相似文献
37.
38.
Truemper configurations (thetas, pyramids, prisms, and wheels) have played an important role in the study of complex hereditary graph classes (eg, the class of perfect graphs and the class of even-hole-free graphs), appearing both as excluded configurations, and as configurations around which graphs can be decomposed. In this paper, we study the structure of graphs that contain (as induced subgraphs) no Truemper configurations other than (possibly) universal wheels and twin wheels. We also study several subclasses of this class. We use our structural results to analyze the complexity of the recognition, maximum weight clique, maximum weight stable set, and optimal vertex coloring problems for these classes. Furthermore, we obtain polynomial -bounding functions for these classes. 相似文献
39.
John Cagnol Irena Lasiecka Catherine Lebiedzik Richard Marchand 《Comptes Rendus Mathematique》2006,342(9):711-716
This note is concerned with the non-linear shallow shell model introduced in 1966 by W.T. Koiter, and later studied by M. Bernadou and J.T. Oden. We show the uniqueness of the solution to the dynamical model and that this solution is continuous with respect to the initial data. To cite this article: J. Cagnol et al., C. R. Acad. Sci. Paris, Ser. I 342 (2006). 相似文献
40.
Irena Penev 《Journal of Graph Theory》2016,81(3):213-235
A graph G is perfect if for all induced subgraphs H of G, . A graph G is Berge if neither G nor its complement contains an induced odd cycle of length at least five. The Strong Perfect Graph Theorem [9] states that a graph is perfect if and only if it is Berge. The Strong Perfect Graph Theorem was obtained as a consequence of a decomposition theorem for Berge graphs [M. Chudnovsky, Berge trigraphs and their applications, PhD thesis, Princeton University, 2003; M. Chudnovsky, N. Robertson, P. Seymour, and R. Thomas, The strong perfect graph theorem, Ann Math 164 (2006), 51–229.], and one of the decompositions in this decomposition theorem was the “balanced skew‐partition.” A clique‐coloring of a graph G is an assignment of colors to the vertices of G in such a way that no inclusion‐wise maximal clique of G of size at least two is monochromatic, and the clique‐chromatic number of G, denoted by , is the smallest number of colors needed to clique‐color G. There exist graphs of arbitrarily large clique‐chromatic number, but it is not known whether the clique‐chromatic number of perfect graphs is bounded. In this article, we prove that every perfect graph that does not admit a balanced skew‐partition is 2‐clique colorable. The main tool used in the proof is a decomposition theorem for “tame Berge trigraphs” due to Chudnovsky et al. ( http://arxiv.org/abs/1308.6444 ). 相似文献