全文获取类型
收费全文 | 2069篇 |
免费 | 95篇 |
国内免费 | 22篇 |
专业分类
化学 | 1377篇 |
晶体学 | 15篇 |
力学 | 37篇 |
数学 | 209篇 |
物理学 | 548篇 |
出版年
2023年 | 13篇 |
2022年 | 12篇 |
2021年 | 58篇 |
2020年 | 50篇 |
2019年 | 44篇 |
2018年 | 35篇 |
2017年 | 37篇 |
2016年 | 93篇 |
2015年 | 55篇 |
2014年 | 74篇 |
2013年 | 168篇 |
2012年 | 144篇 |
2011年 | 167篇 |
2010年 | 92篇 |
2009年 | 83篇 |
2008年 | 120篇 |
2007年 | 125篇 |
2006年 | 115篇 |
2005年 | 112篇 |
2004年 | 96篇 |
2003年 | 88篇 |
2002年 | 77篇 |
2001年 | 39篇 |
2000年 | 41篇 |
1999年 | 26篇 |
1998年 | 26篇 |
1997年 | 21篇 |
1996年 | 19篇 |
1995年 | 12篇 |
1994年 | 16篇 |
1993年 | 30篇 |
1992年 | 17篇 |
1991年 | 5篇 |
1990年 | 12篇 |
1989年 | 10篇 |
1988年 | 2篇 |
1986年 | 3篇 |
1985年 | 6篇 |
1984年 | 4篇 |
1983年 | 6篇 |
1982年 | 4篇 |
1981年 | 7篇 |
1980年 | 6篇 |
1979年 | 2篇 |
1978年 | 2篇 |
1975年 | 4篇 |
1970年 | 1篇 |
1969年 | 1篇 |
1968年 | 1篇 |
1966年 | 1篇 |
排序方式: 共有2186条查询结果,搜索用时 265 毫秒
991.
Myung Hwan Park Jung Oh Huh Youngkyu Do Min Hyung Lee 《Journal of polymer science. Part A, Polymer chemistry》2008,46(17):5816-5825
The copolymerization of ethylene with triphenylamine (TPA)‐containing α‐olefin monomer 1 using a rac‐Et(Ind)2ZrCl2 ( EBIZr )/MAO catalytic system was investigated to prepare polyethylene with pendent TPA groups. Despite the presence of a large excess of TPA moieties, the polymerization reactions efficiently produce copolymers of high‐molecular‐weight with the comonomer incorporation up to 6.1 mol % upon varying the comonomer concentration in the feed. Inspection of the aliphatic region of the 13C‐NMR spectrum and the estimated copolymerization parameters (r 1 ≈ 0 for 1 and rE ≈ 43 for ethylene) reveal the presence of isolated comonomer units in the polymer chain. While UV–vis absorption measurements of the copolymers show an invariant absorption feature, PL spectra exhibit a slightly red‐shifted emission with increasing content of 1 in the polymer chain. All the copolymers show high thermal stability (Td5 > 436 °C), and the electrochemical stability toward oxidation is also observed. Particularly, the copolymer displays hole‐transporting ability for the stable green emission of Alq3 when incorporated into the hole‐transporting layer of an electroluminescence device. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5816–5825, 2008 相似文献
992.
993.
Dr. Tae Hyung Kim Dr. Magdalena Swierczewska Dr. Yumin Oh Dr. AeRyon Kim Prof. Dr. Dong Gyu Jo Prof. Dr. Jae Hyung Park Prof. Dr. Youngro Byun Prof. Dr. Scheherazade Sadegh‐Nasseri Prof. Dr. Martin G. Pomper Prof. Dr. Kang Choon Lee Prof. Dr. Seulki Lee 《Angewandte Chemie (International ed. in English)》2013,52(27):6880-6884
994.
Young Seon Oh Shunsuke Kotani Masaharu Sugiura Makoto Nakajima 《Tetrahedron: Asymmetry》2010,21(15):1833-1835
Chiral dinitrones were synthesized by the condensation of a C2-symmetrical chiral dihydroxylamine with various aldehydes. The electronic and steric properties of the dinitrones can be modified by changing the aldehyde component. The activity of dinitrones as Lewis base catalysts was examined for the asymmetric allylation of aldehydes with allyltrichlorosilanes. Using DMPU as an additive in chloroform, the reaction proceeded at room temperature to afford allylated products in good yields and good enantioselectivities. 相似文献
995.
996.
Sang-Yeon Lee Hyun Been Choi Mina Park Il Soon Choi Jieun An Ami Kim Eunku Kim Nahyun Kim Jin Hee Han Min young Kim Seung min Lee Doo-Yi Oh Bong Jik Kim Nayoung Yi Nayoung K. D. Kim Chung Lee Woong-Yang Park Young Ik Koh Heon Yung Gee Hyun Sung Cho Tong Mook Kang Byung Yoon Choi 《Experimental & molecular medicine》2021,53(7):1192
Loss-of-function variant in the gene encoding the KCNQ4 potassium channel causes autosomal dominant nonsyndromic hearing loss (DFNA2), and no effective pharmacotherapeutics have been developed to reverse channel activity impairment. Phosphatidylinositol 4,5-bisphosphate (PIP2), an obligatory phospholipid for maintaining KCNQ channel activity, confers differential pharmacological sensitivity of channels to KCNQ openers. Through whole-exome sequencing of DFNA2 families, we identified three novel KCNQ4 variants related to diverse auditory phenotypes in the proximal C-terminus (p.Arg331Gln), the C-terminus of the S6 segment (p.Gly319Asp), and the pore region (p.Ala271_Asp272del). Potassium currents in HEK293T cells expressing each KCNQ4 variant were recorded by patch-clamp, and functional recovery by PIP2 expression or KCNQ openers was examined. In the homomeric expression setting, the three novel KCNQ4 mutant proteins lost conductance and were unresponsive to KCNQ openers or PIP2 expression. Loss of p.Arg331Gln conductance was slightly restored by a tandem concatemer channel (WT-p.R331Q), and increased PIP2 expression further increased the concatemer current to the level of the WT channel. Strikingly, an impaired homomeric p.Gly319Asp channel exhibited hyperactivity when a concatemer (WT-p.G319D), with a negative shift in the voltage dependence of activation. Correspondingly, a KCNQ inhibitor and chelation of PIP2 effectively downregulated the hyperactive WT-p.G319D concatemer channel. Conversely, the pore-region variant (p.Ala271_Asp272del) was nonrescuable under any condition. Collectively, these novel KCNQ4 variants may constitute therapeutic targets that can be manipulated by the PIP2 level and KCNQ-regulating drugs under the physiological context of heterozygous expression. Our research contributes to the establishment of a genotype/mechanism-based therapeutic portfolio for DFNA2.Subject terms: Genetics research, Translational research 相似文献
997.
Screening for superoxide reactivity in Li-O2 batteries: effect on Li2O2/LiOH crystallization 总被引:1,自引:0,他引:1
Black R Oh SH Lee JH Yim T Adams B Nazar LF 《Journal of the American Chemical Society》2012,134(6):2902-2905
Unraveling the fundamentals of Li-O(2) battery chemistry is crucial to develop practical cells with energy densities that could approach their high theoretical values. We report here a straightforward chemical approach that probes the outcome of the superoxide O(2)(-), thought to initiate the electrochemical processes in the cell. We show that this serves as a good measure of electrolyte and binder stability. Superoxide readily dehydrofluorinates polyvinylidene to give byproducts that react with catalysts to produce LiOH. The Li(2)O(2) product morphology is a function of these factors and can affect Li-O(2) cell performance. This methodology is widely applicable as a probe of other potential cell components. 相似文献
998.
Lee N Cho HR Oh MH Lee SH Kim K Kim BH Shin K Ahn TY Choi JW Kim YW Choi SH Hyeon T 《Journal of the American Chemical Society》2012,134(25):10309-10312
Multimodal imaging is highly desirable for accurate diagnosis because it can provide complementary information from each imaging modality. In this study, a sol-gel reaction of tantalum(V) ethoxide in a microemulsion containing Fe(3)O(4) nanoparticles (NPs) was used to synthesize multifunctional Fe(3)O(4)/TaO(x) core/shell NPs, which were biocompatible and exhibited a prolonged circulation time. When the NPs were intravenously injected, the tumor-associated vessel was observed using computed tomography (CT), and magnetic resonance imaging (MRI) revealed the high and low vascular regions of the tumor. 相似文献
999.
P Khiev OK Kwon HH Song SR Oh KS Ahn HK Lee YW Chin 《Chemical & pharmaceutical bulletin》2012,60(8):955-961
From the stems of Dipterocarpus obtusifolius, five new triterpenes, 3-oxo-20-hydroxy-30α-methyl,17(29)α-epoxy-28-norlupane (1), 3-oxo-20-hydroxy-30β-methyl-17(29)α-epoxy-28-norlupane (2), 3,20-dioxo-28,29-norlupan-17α-ol (3), 27-demethyl-20(S)-dammar-23-ene-20-ol-3,25-dione (4), and 3-epi-cecropic acid (5) together with 13 known compounds including diterpene, sesquiterpenes and triterpenes were isolated and characterized. All isolates were tested for their cytotoxicities against a small panel of human cancer cell lines. Of the tested compounds, compounds 4-11 were found to be cytotoxic against one or more human cancer cell lines. 相似文献
1000.
Simultaneous determination of zolazepam and tiletamine in dog plasma by liquid chromatography coupled to a tandem mass spectrometry 总被引:1,自引:0,他引:1
Noh K Kim KS Ahn B Archimbault P Oh TH Kang W 《Biomedical chromatography : BMC》2012,26(10):1133-1136
A mixture of tiletamine, a dissociative anesthetic, and zolazepam, a minor tranquilizer, has been widely used as an anesthetic or an immobilizing agent in a variety of animal species. However, interestingly, their pharmacokinetic behaviors have been published only in polar bears and pigs. In this study, we introduce a sensitive liquid chromatography/tandem mass spectrometry (LC/MS/MS) method for determining the two drugs in dog plasma. After simple protein precipitation with acetonitrile including midazolam (internal standard), the analytes were chromatographed on a reversed‐phase column with a mobile phase of 10 m m ammonium acetate aqueous solution and acetonitrile (1:4, v/v). The accuracy and precision of the assay were in accordance with FDA regulations for the validation of bioanalytical methods. This method was used to measure the concentrations of zolazepam and tiletamine in plasma after a single intramuscular 10 mg dose of each in beagle dogs. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献