全文获取类型
收费全文 | 9510篇 |
免费 | 358篇 |
国内免费 | 22篇 |
专业分类
化学 | 6980篇 |
晶体学 | 59篇 |
力学 | 203篇 |
数学 | 1187篇 |
物理学 | 1461篇 |
出版年
2023年 | 73篇 |
2022年 | 159篇 |
2021年 | 318篇 |
2020年 | 233篇 |
2019年 | 205篇 |
2018年 | 209篇 |
2017年 | 211篇 |
2016年 | 382篇 |
2015年 | 335篇 |
2014年 | 352篇 |
2013年 | 612篇 |
2012年 | 694篇 |
2011年 | 771篇 |
2010年 | 504篇 |
2009年 | 413篇 |
2008年 | 618篇 |
2007年 | 590篇 |
2006年 | 476篇 |
2005年 | 623篇 |
2004年 | 511篇 |
2003年 | 373篇 |
2002年 | 246篇 |
2001年 | 110篇 |
2000年 | 94篇 |
1999年 | 79篇 |
1998年 | 49篇 |
1997年 | 60篇 |
1996年 | 59篇 |
1995年 | 52篇 |
1994年 | 46篇 |
1993年 | 34篇 |
1992年 | 30篇 |
1991年 | 35篇 |
1990年 | 27篇 |
1989年 | 19篇 |
1988年 | 11篇 |
1987年 | 19篇 |
1986年 | 19篇 |
1985年 | 33篇 |
1984年 | 30篇 |
1983年 | 19篇 |
1982年 | 16篇 |
1981年 | 16篇 |
1980年 | 17篇 |
1979年 | 15篇 |
1978年 | 13篇 |
1977年 | 7篇 |
1976年 | 11篇 |
1975年 | 9篇 |
1973年 | 10篇 |
排序方式: 共有9890条查询结果,搜索用时 15 毫秒
1.
2.
3.
4.
5.
6.
Functional Carbazole Liquid‐Crystal Block Codendrimers with Optical and Electronic Properties
下载免费PDF全文
![点击此处可从《Chemistry (Weinheim an der Bergstrasse, Germany)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Ismael Gracia Beatriz Feringán Prof. José Luis Serrano Dr. Roberto Termine Dr. Attilio Golemme Dr. Ana Omenat Prof. Joaquín Barberá 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(3):1359-1369
The synthesis and characterisation of a family of block codendrimers consisting of highly versatile mesogenic and carbazole‐containing 2,2‐bis(hydroxymethyl)propionic acid (bis‐MPA) dendrons are reported. The liquid‐crystal behaviour was investigated by means of differential scanning calorimetry, polarised‐light optical microscopy and X‐ray diffraction. Depending on the chemical structure of the constituent dendrons, the codendrimers show lamellar or columnar mesophases. On the basis of the experimental results, models both at the molecular level and in the mesophase are proposed. The physical properties of the block codendrimers derived from the presence of the carbazole moiety in their structure were investigated: photoluminescence in solution and in the mesophase, electrochemical behaviour and hole transport. Electrodeposition of carbazole dendrons afforded a globular supramolecular conformation in which the mesogenic molecular side plays a key role. 相似文献
7.
Single Crystal to Single Crystal (SC‐to‐SC) Transformation from a Nonporous to Porous Metal–Organic Framework and Its Application Potential in Gas Adsorption and Suzuki Coupling Reaction through Postmodification
下载免费PDF全文
![点击此处可从《Chemistry (Weinheim an der Bergstrasse, Germany)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Dr. Rupam Sen Debraj Saha Dr. Subratanath Koner Dr. Paula Brandão Dr. Zhi Lin 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(15):5962-5971
A new amino‐functionalized strontium–carboxylate‐based metal–organic framework (MOF) has been synthesized that undergoes single crystal to single crystal (SC‐to‐SC) transformation upon desolvation. Both structures have been characterized by single‐crystal X‐ray analysis. The desolvated structure shows an interesting 3D porous structure with pendent ?NH2 groups inside the pore wall, whereas the solvated compound possesses a nonporous structure with DMF molecules on the metal centers. The amino group was postmodified through Schiff base condensation by pyridine‐2‐carboxaldehyde and palladium was anchored on that site. The modified framework has been utilized for the Suzuki cross‐coupling reaction. The compound shows high activity towards the C?C cross‐coupling reaction with good yields and turnover frequencies. Gas adsorption studies showed that the desolvated compound had permanent porosity and was microporous in nature with a BET surface area of 2052 m2 g?1. The material also possesses good CO2 (8 wt %) and H2 (1.87 wt %) adsorption capabilities. 相似文献
8.
Condeixa Lucas Dias Silva Pierry Moah Diego Farias Brenda Leiras Adriana 《Central European Journal of Operations Research》2022,30(3):921-940
Central European Journal of Operations Research - Societal awareness and legislation changes concerning sustainability have affected how organizations generate value for stakeholders, as well as... 相似文献
9.
João Marcos G. Barbosa Milenna K. Fernandes Rodrigues Lurian C. David Taynara C. e Silva Danielly A. Fortuna Lima Naiara Z. Pereira Emmanuel B. D'Alessandro Anselmo E. de Oliveira Paulo H. Jorge da Cunha Maria Clorinda S. Fioravanti Nelson R. Antoniosi Filho 《Biomedical chromatography : BMC》2020,34(11):e4935
An innovative volatolomic approach employs the detection of biomarkers present in cerumen (earwax) to identify cattle intoxication by Stryphnodendron rotundifolium Mart., Fabaceae (popularly known as barbatimão). S. rotundifolium is a poisonous plant with the toxic compound undefined and widely distributed throughout the Brazilian territory. Cerumen samples from cattle of two local Brazilian breeds (‘Curraleiro Pé-Duro’ and ‘Pantaneiro’) were collected during an experimental intoxication protocol and analyzed using headspace (HS)/GC–MS followed by multivariate analysis (genetic algorithm for a partial least squares, cluster analysis, and classification and regression trees). A total of 106 volatile organic metabolites were identified in the cerumen samples of bovines. The intoxication by S. rotundifolium influenced the cerumen volatolomic profile of the bovines throughout the intoxication protocol. In this way, it was possible to detect biomarkers for cattle intoxication. Among the biomarkers, 2-octyldecanol and 9-tetradecen-1-ol were able to discriminate all samples between intoxicated and nonintoxicated bovines. The cattle intoxication diagnosis by S. rotundifolium was accomplished by applying the cerumen analysis using HS/GC–MS, in an easy, accurate, and noninvasive way. Thus, the proposed bioanalytical chromatography protocol is a useful tool in veterinary applications to determine this kind of intoxication. 相似文献
10.
K.M.J. Rocha R.G. Leitão E.G. Oliveira-Barros M.A. Oliveira C.G.L. Canellas M.J. Anjos L.E. Nasciutti R.T. Lopes 《X射线光谱测定》2019,48(5):476-481
Prostate cancer is a highly prevalent disease and ranks second among malignant neoplasms that affect men around the world, behind lung cancer alone. Trace elements are very important and are involved in many cellular processes. The X-ray microfluorescence technique is an advanced tool of high spatial resolution, sensitivity, multielemental analysis, and nondestructiveness for trace element study. This study aimed to investigate the elemental distribution in spheroids obtained through the following human prostate cell lines using synchrotron X-ray microfluorescence: tumor cell line androgen independent (DU145), tumor cell line androgen dependent (LNCaP), and normal cell line (RWPE-1). The measurements were performed with a standard geometry of 45° of incidence, excited by a white beam using a pixel of 25 μm and an acquisition time of 300 ms/pixel at the X-ray fluorescence beamline at the Synchrotron Light National Laboratory (Campinas, Brazil). The synchrotron X-ray microfluorescence results showed differences between groups in all elements analyzed and suggested that further studies should be performed to understand the relationship of these trace elements with the progression and development of the disease. 相似文献