全文获取类型
收费全文 | 777篇 |
免费 | 22篇 |
国内免费 | 12篇 |
专业分类
化学 | 500篇 |
晶体学 | 1篇 |
力学 | 41篇 |
综合类 | 11篇 |
数学 | 85篇 |
物理学 | 173篇 |
出版年
2024年 | 2篇 |
2023年 | 7篇 |
2022年 | 19篇 |
2021年 | 37篇 |
2020年 | 32篇 |
2019年 | 28篇 |
2018年 | 29篇 |
2017年 | 12篇 |
2016年 | 35篇 |
2015年 | 27篇 |
2014年 | 29篇 |
2013年 | 56篇 |
2012年 | 54篇 |
2011年 | 43篇 |
2010年 | 30篇 |
2009年 | 31篇 |
2008年 | 33篇 |
2007年 | 54篇 |
2006年 | 32篇 |
2005年 | 38篇 |
2004年 | 20篇 |
2003年 | 31篇 |
2002年 | 31篇 |
2001年 | 8篇 |
2000年 | 2篇 |
1999年 | 10篇 |
1998年 | 8篇 |
1997年 | 5篇 |
1995年 | 2篇 |
1994年 | 5篇 |
1993年 | 6篇 |
1992年 | 2篇 |
1991年 | 5篇 |
1989年 | 2篇 |
1988年 | 2篇 |
1986年 | 2篇 |
1985年 | 2篇 |
1983年 | 2篇 |
1982年 | 4篇 |
1980年 | 2篇 |
1979年 | 6篇 |
1977年 | 5篇 |
1976年 | 2篇 |
1970年 | 2篇 |
1968年 | 3篇 |
1960年 | 1篇 |
1959年 | 1篇 |
1957年 | 1篇 |
1945年 | 1篇 |
1936年 | 1篇 |
排序方式: 共有811条查询结果,搜索用时 375 毫秒
111.
Aqsa Habib Mansoureh Nazari V. Muhammad Adnan Iqbal Haq Nawaz Bhatti M.B. Khadeer Ahmed A.M.S. Abdul Majid 《Journal of Saudi Chemical Society》2019,23(7):795-808
The promising biomedical applications of silver complexes stimulated the researchers to test these compounds against cancer. The present research work was designed to achieve this goal. In this work, a series of 5-methyl benzimidazole based N-Heterocyclic carbene ligands and respective silver(I) complexes were synthesized and tested on cancer cell lines to assess their anticancer activity. Unsymmetrically substituted benzimidazole was found unique in its reactivity and generation of a single product during NHC ligand formation was only possible after two successive alkylations with same alkyl halide. The corresponding Ag(I)-NHC adducts were obtained by in situ deprotonation of the NHC ligands. Synthesized compounds were characterized by various physcio-chemical and spectroscopic methods. Single crystal X-ray diffraction study of complex 7 revealed its mononuclear structure. Preliminary in vitro anticancer study of azolium salts and respective Ag(I)-NHC complexes against human breast cancer (MDA-MB-231), colon cancer (HCT-116) and normal endothelial cells (EA.hy926) cells revealed that all the compounds are more cytotoxic to cancer cells than normal cells and the complexes are relatively more potent compared to the corresponding NHC ligands. It was found that increased chain length and presence of methyl substituent on benzimidazole ring enhance the biopotency of Ag(I)-NHC complexes. The synthesized compounds were further studied for pro-apoptotic mechanism of action via Rhodamine 123 test. The tested compounds were found to induce apoptosis via extrinsic mitochondrial pathway. 相似文献
112.
Muhammad Zafar Irshad Khan Syeda Saniya Zahra Madiha Ahmed Humaira Fatima Bushra Mirza Ihsan-ul Haq 《Natural product research》2019,33(14):2099-2104
Ipomoea carnea Jacq. is an important folklore medicinal plant, assessed for its underexplored biological potential. Antioxidant, cytotoxic, antiproliferative and polyphenolic profile of whole plant was evaluated using various techniques. Maximum extract recovery (29% w/w), phenolic [13.54 ± 0.27 μg GAE/mg dry weight (DW)] and flavonoid (2.11 ± 0.10 μg QE /mg DW) content were recorded in methanol-distilled water (1:1) flower extract. HPLC-DAD analysis quantified substantial amount of six different polyphenols ranging from 0.081 to 37.95 μg/mg extract. Maximum total antioxidant and reducing potential were documented in methanol-distilled water and acetone-distilled water flower extracts (42.62 ± 0.47 and 24.38 ± 0.39 μg AAE/mg DW) respectively. Ethanol-chloroform root extract manifested highest free radical scavenging (IC50 of 61.22 μg/mL) while 94.64% of the extracts showed cytotoxicity against brine shrimps. Ethanol leaf extract exhibited remarkable activity against THP-1 cell line (IC50 = 8 ± 0.05 μg/mL) and protein kinases (31 mm phenotype bald zone). 相似文献
113.
Kumar Mahesh Reddy G. Janardhana Bég O. Anwar 《Journal of Thermal Analysis and Calorimetry》2019,138(1):531-543
Journal of Thermal Analysis and Calorimetry - This article studies the pattern of heat lines in free convection non-Newtonian flow from a semi-infinite vertical cylinder via Bejan’s heat... 相似文献
114.
Andrew Care Helena Nevalainen Peter L. Bergquist Anwar Sunna 《Applied biochemistry and biotechnology》2014,173(8):2225-2240
An inorganic-binding peptide sequence with high affinity to silica-containing materials was fused to a glycoside hydrolase GH26 mannanase, ManA, from the extremely thermophilic bacterium Dictyoglomus thermophilum. The resulting recombinant enzyme produced in Escherichia coli, ManA-Linker, displayed high binding affinity towards synthetic zeolite while retaining its catalytic activity at 80 °C. ManA-Linker was able to bind to the zeolite at different pH levels, indicating a true pH-independent binding. However, complete degradation of the peptide linker was observed when the recombinant ManA-Linker was exposed to the supernatant from the filamentous fungus Trichoderma reesei. This degradation was caused by extracellular proteinases produced by T. reesei during its growth phase. Several derivatives of ManA-Linker were designed and expressed in E. coli. All the derivatives carrying a single sequence of the linker were still susceptible to T. reesei proteinase degradation. Complete substitution of the linker sequence by (GGGGS)16 resulted in a proteinase-resistant ManA derivative, ManA-Linker-(GGGGS)16, which was able to bind to zeolite in a pH-dependent manner. 相似文献
115.
Dr. Jan Nekvinda Michael Kugler Dr. Josef Holub Dr. Suzan El Anwar Dr. Jiří Brynda Klára Pospíšilová Dr. Zdeňka Růžičková Dr. Pavlína Řezáčová Dr. Bohumír Grüner 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(69):16541-16553
Carbonic anhydrase IX (CA IX), a tumor-associated metalloenzyme, represents a validated target for cancer therapy and diagnostics. Herein, we report the inhibition properties of isomeric families of sulfonamidopropyl-dicarba-closo-dodecaboranes group(s) prepared using a new direct five-step synthesis from the corresponding parent cages. The protocol offers a reliable solution for synthesis of singly and doubly substituted dicarba-closo-dodecaboranes with a different geometric position of carbon atoms. The closo-compounds from the ortho- and meta-series were then degraded to corresponding 11-vertex dicarba-nido-undecaborate(1−) anions. All compounds show in vitro enzymatic activity against CA IX in the low nanomolar or subnanomolar range. This is accompanied by clear isomer dependence of the inhibition constant (Ki) and selectivity towards CA IX. Decreasing trends in Ki and selectivity index (SI) values are observed with increasing separation of the cage carbon atoms. Interactions of compounds with the active sites of CA IX were explored with X-ray crystallography, and eight high-resolution crystal structures uncovered the structural basis of inhibition potency and selectivity. 相似文献
116.
A theoretical study is presented of peristaltic hydrodynamics of an aqueous electrolytic non-Newtonian Jeffrey bio-rheological fluid through an asymmetric microchannel under an applied axial electric field. An analytical approach is adopted to obtain the closed form solution for velocity, volumetric flow, pressure difference and stream function. The analysis is also restricted under the low Reynolds number assumption (Stokes flow) and lubrication theory approximations (large wavelength). Small ionic Peclét number and Debye–Hückel linearization (i.e. wall zeta potential ≤ 25 mV) are also considered to simplify the Nernst–Planck and Poisson–Boltzmann equations. Streamline plots are also presented for the different electro-osmotic parameter, varying magnitudes of the electric field (both aiding and opposing cases) and for different values of the ratio of relaxation to retardation time parameter. Comparisons are also included between the Newtonian and general non-Newtonian Jeffrey fluid cases. The results presented here may be of fundamental interest towards designing lab-on-a-chip devices for flow mixing, cell manipulation, micro-scale pumps etc. Trapping is shown to be more sensitive to an electric field (aiding, opposing and neutral) rather than the electro-osmotic parameter and viscoelastic relaxation to retardation ratio parameter. The results may also help towards the design of organ-on-a-chip like devices for better drug design. 相似文献
117.
118.
119.
Inam ul Haq Raja Jae Yeol Lee In Tae Kim So Ha Lee 《Monatshefte für Chemie / Chemical Monthly》2008,139(7):725-737
Much effort has been devoted to the design and synthesis of polymers for use in flat panel display, solid state lighting,
transistors, and photovoltaic devices. Especially, development of white light emitting polymeric materials has recently attracted
much interest owing to their possible use in lighting application and backlights for flat panel displays. White emission has
been obtained from polymeric molecules, small organic molecules, organometallic molecules, and phosphor-based or quantum dot-based
inorganic molecules. Among materials used in white light emitting diodes, we summarize the white light emitting polymeric
materials synthesized and published till December 2007.
Correspondence: In Tae Kim, Department of Chemistry, Kwangwoon University, 447-1 Wolgye-Dong, Nowon-Ku, Seoul 139-701, Korea,
So Ha Lee, Life Sciences Research Division, Korea Institute of Science and Technology, P.O. Box 131, Cheongryang, Seoul 130-650,
Korea. 相似文献
120.
Density and viscosity data of proline (Pro) in sodium dodecyl sulfate/cetyltrimethylammonium bromide/poly (oxyethylene) isooctyl phenyl ether in formamide were measured at 298.15, 303.15, 308.15, and 313.15K and 0.1MPa. The density data were utilized to evaluate standard partial molar volumes (φ0V) and partial molar isobaric expansibility (φ0E). The viscosity data were used to evaluate A-and B-coefficients, free energy of activation of viscous flow (⊿μ0*1) and (⊿μ0*2), per mole of solvent and solute respectively, enthalpy (⊿H*) and entropy (⊿S*) of activation of viscous flow. The results obtained were utilized in the qualitative elucidation of the Pro-surfactant/formamide and Pro-Pro interactions in the present systems. 相似文献