全文获取类型
收费全文 | 8527篇 |
免费 | 1386篇 |
国内免费 | 673篇 |
专业分类
化学 | 5790篇 |
晶体学 | 87篇 |
力学 | 504篇 |
综合类 | 36篇 |
数学 | 999篇 |
物理学 | 3170篇 |
出版年
2024年 | 23篇 |
2023年 | 163篇 |
2022年 | 286篇 |
2021年 | 290篇 |
2020年 | 365篇 |
2019年 | 304篇 |
2018年 | 275篇 |
2017年 | 261篇 |
2016年 | 422篇 |
2015年 | 431篇 |
2014年 | 469篇 |
2013年 | 604篇 |
2012年 | 789篇 |
2011年 | 755篇 |
2010年 | 530篇 |
2009年 | 487篇 |
2008年 | 553篇 |
2007年 | 421篇 |
2006年 | 457篇 |
2005年 | 333篇 |
2004年 | 265篇 |
2003年 | 218篇 |
2002年 | 173篇 |
2001年 | 139篇 |
2000年 | 148篇 |
1999年 | 176篇 |
1998年 | 155篇 |
1997年 | 129篇 |
1996年 | 136篇 |
1995年 | 116篇 |
1994年 | 101篇 |
1993年 | 84篇 |
1992年 | 80篇 |
1991年 | 76篇 |
1990年 | 44篇 |
1989年 | 38篇 |
1988年 | 39篇 |
1987年 | 35篇 |
1986年 | 30篇 |
1985年 | 23篇 |
1984年 | 20篇 |
1983年 | 20篇 |
1982年 | 10篇 |
1981年 | 14篇 |
1980年 | 9篇 |
1977年 | 6篇 |
1976年 | 10篇 |
1975年 | 9篇 |
1973年 | 8篇 |
1972年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
971.
Single‐Crystal‐to‐Single‐Crystal Transition in an Enantiopure [7]Helquat Salt: The First Observation of a Reversible Phase Transition in a Helicene‐Like Compound 下载免费PDF全文
Dr. Naba K. Nath Lukáš Severa Dr. Roman A. Kunetskiy Prof. Ivana Císařová Prof. Michal Fulem Prof. Květoslav Růžička Dr. Dušan Koval Dr. Václav Kašička Dr. Filip Teplý Prof. Panče Naumov 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(39):13508-13512
Here it is reported that crystals of an enantiopure [7]helquat salt undergo reversible thermal solid–solid phase transition at 404 K. Differential scanning calorimetry (DSC), capillary electrophoresis (CE), and X‐ray diffraction analysis were used to unravel the mechanistic details of this process. The single‐crystal‐to‐single‐crystal course enabled direct monitoring of the structural changes by in situ variable‐temperature X‐ray diffraction, thus providing the first direct evidence of a solid phase transition in a helicene‐like compound. 相似文献
972.
973.
Frontispiece: A Step‐by‐Step Assembly of a 3D Coordination Polymer in the Solid‐State by Desolvation and [2+2] Cycloaddition Reactions 下载免费PDF全文
974.
By integrating photoinduced electron transfer (PET) into the design of functional bioluminogenic probes, Urano and his coworkers recently developed a new rational design strategy, BioLeT. It is expected that this BioLeT strategy will enable us to design and develop new bioluminescence probes for detecting various biomolecules with no catalytic or reactive activity. 相似文献
975.
The rapid and reliable measurement of hydrogen peroxide (H2O2) is imperative for many areas of technology, including pharmaceutical, clinical, food industry and environmental applications. In this work, a novel multifunctional complex, [Ru(bpy)2(luminol-bpy)](PF6)2 (bpy: 2,20'-bipyridine), was designed and synthesized by incorporating a Ru(II) complex with a luminal group. In the presence of horseradish peroxidase (HRP), reaction of [Ru(bpy)2(luminol-bpy)]2+ with H2O2 can be monitored by three sensing channels including photoluminescence (PL), chemiluminiscence (CL) and eletrochemiluminiscence (ECL). The quantitative assays for H2O2 in aqueous solutions using [Ru(bpy)2(Luminalbpy)]( PF6)2 as a probe were established with PL, ECL and CL signal output modes, respectively. 相似文献
976.
Rui Tao Xue-Jiao Yin Ke-Hu Wang Yu-Zhuo Niu Ya-Lin Wang Dan-Feng Huang Ying-Peng Su Jin-Xian Wang Yu-Lai Hu Ying Fu Zheng-Yin Du 《中国化学快报》2015,26(8):1046-1049
Exceedingly fast preparation of trifluoromethyl tertiary alcohols has been accomplished from methyl ketones and trifluoromethyl ketones under solvent free conditions by cross Aldol reaction. The reaction was achieved in the presence of common inorganic base by grinding method at ambient temperature to give β-trifluoromethyl-β-hydroxyl ketones in high yields (up to 95%). 相似文献
977.
Development and validation of polymerized high internal phase emulsion monoliths coupled with HPLC and fluorescence detection for the determination of trace tetracycline antibiotics in environmental water samples 下载免费PDF全文
Fuyou Du Xian Zheng Lin Sun Qun Qin Lin Guo Guihua Ruan 《Journal of separation science》2015,38(21):3774-3780
A polymerized high internal phase emulsion monolith was used as a novel sorbent for solid‐phase extraction coupled with high‐performance liquid chromatography and fluorescence detection for the determination of oxytetracycline, tetracycline, doxycycline, and chlorotetracycline in environmental water samples. The polymerized high internal phase emulsion monolithic column was prepared by the in situ polymerization of the continuous phase of a high internal phase emulsion containing glycidyl methacrylate, styrene, and divinylbenzene in pipette tips, and then functionalized with iminodiacetic acid. The resulting monolith exhibited highly interconnected porosity and large surface areas, making it an excellent candidate as an solid‐phase extraction sorbent for the enrichment of trace tetracycline antibiotics. Several factors affecting the extraction performance of polymerized high internal phase emulsion monoliths, including the pH of sample solution, the eluting solvents, the sample loading flow rate and volume, were investigated, respectively. Under the optimized conditions, the mean recoveries of oxytetracycline, tetracycline, doxycycline, and chlorotetracycline spiked in pond and farm wastewater samples ranged from 78.1 to 119.3% with relative standard deviation less than 15%. The detection limits (S/N = 3) of the proposed method were in the range of 51–137 pg/mL. This study demonstrated that the monolithic polymerized high internal phase emulsion would be promising solid‐phase extraction sorbents in the extraction and proconcentration of trace analytes from complex samples. 相似文献
978.
Hydrophobic terminal group of surfactant initiating micellization as revealed by 1H NMR spectroscopy
The critical aggregation concentration (CAC) of four with three kinds of conventional surfactants, namely, two cationic surfactants [hexadecyltrimethyl ammonium bromide (CTAB) and tetradecyltrimethyl ammonium bromide (TTAB)], one anionic surfactant [sodium dodecyl sulfate (SDS)], and a nonionic surfactant [Triton X-100 (TX-100)], were determined by variation of 1H chemical shifts with surfactant concentrations. Results show that the CAC values of protons at different positions of the same molecule are different, and those of the terminal methyl protons are the lowest, respectively, which suggests that the terminal groups of the alkyl chains aggregates first during micellization. Measurement of the transverse relaxation time (T2) of different protons in SDS also show that the terminal methyl protons start to decrease with the increase in concentration first, which supports the above mentioned tendency. 相似文献
979.
Cai-Na Xu Hua-Yu Tian Yan-Bing Wang Yang Du Jie Chen Lin Lin Zhao-Pei Guo Xue-Si Chen 《中国化学快报》2017,28(4):807-812
Direct administration of drugs and genes to the lungs by pulmonary delivery offers a potential effective therapy for lung cancers.In this study,combined doxorubicin(DOX)and Bcl2 siRNA was employed for cancer therapy using polyethylenimine(PEI)as the carrier of Bcl2 siRNA.Most of the DOX and siRNA possessed high cellular uptake efficiency in B16F10 cells,which was proved by FCM and CLSM analysis. Real-time PCR showed that PEI/Bcl2 siRNA exhibited high gene silencing efficiency with 70% Bcl2 mRNA being knocked down.The combination of DOX and siRNA could enhance the cell proliferation inhibition and the cell apoptosis against B16F10 cells compared to free DOX or PEI/Bcl2 siRNA.Furthermore,the biodistribution of DOX and siRNA via pulmonary administration was studied in mice with B16F10 metastatic lung cancer.The results showed that most of the DOX and siRNA were accumulated in lungs and lasted at least for 3 days,which suggested that combined DOX and siRNA by pulmonary administration may have high anti-tumor effects for metastatic lung cancer treatment in vivo. 相似文献
980.
Juan Du Zhie Zhou Xueqing Zhang Shuang Wu Jianhua Xiong Wenjun Wang Qiushui Luo 《Journal of Cluster Science》2017,28(6):3149-3158
Biosynthesis of gold nanoparticles (GNPs) by flavonoids from Lilium casa blanca has been developed. Several parameters such as pH, reaction temperature, reaction time and concentration of flavonoids were explored to control the formation of the GNPs. The synthesized GNPs were characterized by UV–Vis spectroscopy, transmission electron microscopy and X-ray diffraction. Stability and catalytic activity of the synthesized GNPs were also discussed. The results showed that the synthesized GNPs were in spherical, about 2.6 nm, with a face centered cubic structure. Synthesized GNPs showed good catalytic activity in the reduction of p-nitrophenol (p-NP) to p-aminphenol (p-AP). This method for synthesis of GNPs is simple, economic, nontoxic and efficient. 相似文献