全文获取类型
收费全文 | 20114篇 |
免费 | 2705篇 |
国内免费 | 1922篇 |
专业分类
化学 | 11282篇 |
晶体学 | 186篇 |
力学 | 844篇 |
综合类 | 67篇 |
数学 | 1790篇 |
物理学 | 4863篇 |
无线电 | 5709篇 |
出版年
2024年 | 84篇 |
2023年 | 542篇 |
2022年 | 647篇 |
2021年 | 881篇 |
2020年 | 877篇 |
2019年 | 733篇 |
2018年 | 644篇 |
2017年 | 586篇 |
2016年 | 902篇 |
2015年 | 964篇 |
2014年 | 1040篇 |
2013年 | 1433篇 |
2012年 | 1665篇 |
2011年 | 1697篇 |
2010年 | 1158篇 |
2009年 | 1202篇 |
2008年 | 1328篇 |
2007年 | 1115篇 |
2006年 | 1075篇 |
2005年 | 978篇 |
2004年 | 706篇 |
2003年 | 601篇 |
2002年 | 539篇 |
2001年 | 437篇 |
2000年 | 376篇 |
1999年 | 409篇 |
1998年 | 275篇 |
1997年 | 217篇 |
1996年 | 258篇 |
1995年 | 209篇 |
1994年 | 176篇 |
1993年 | 147篇 |
1992年 | 130篇 |
1991年 | 113篇 |
1990年 | 113篇 |
1989年 | 80篇 |
1988年 | 70篇 |
1987年 | 51篇 |
1986年 | 42篇 |
1985年 | 50篇 |
1984年 | 42篇 |
1983年 | 22篇 |
1982年 | 17篇 |
1981年 | 20篇 |
1980年 | 11篇 |
1979年 | 9篇 |
1976年 | 10篇 |
1975年 | 12篇 |
1971年 | 7篇 |
1969年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 62 毫秒
991.
Catalysis Surveys from Asia - Co3O4 catalyst derived from Co-MOFs demonstrated rich active sites in the catalytic reaction. In this paper, we prepared the rod-like Co3O4 catalysts by calcining... 相似文献
992.
Yang Lu Nie Cui-Yun Han Ying Sun Jing Yan Chao-Guo 《Journal of inclusion phenomena and macrocyclic chemistry》2022,102(1-2):89-97
Journal of Inclusion Phenomena and Macrocyclic Chemistry - The condensation reaction of mono-amido-functionalized pillar[5]arenes with tere- and iso-phthaloyl diisothiocyanates in acetone under... 相似文献
993.
Graphene oxide (GO) has been considered as a promising stationary phase for chromatographic separation. However, the very strong adsorption of the analytes on the GO surface lead to the severe peak tailing, which in turn resulting in decreased separation performance. In this work, GO and silica nanoparticles hybrid nanostructures (GO/SiO2 NPs@column) were coated onto the capillary inner wall by passing the mixture of GO and silica sol through the capillary column. The successful of coating of GO/SiO2 NPs onto the capillary wall was confirmed by SEM and electroosmotic flow mobilities test. By partially covering the GO surface with silica nanoparticles, the peak tailing was decreased greatly while the unique high shape selectivity arises from the surface of remained GO was kept. Consequently, compared with the column modified with GO (GO@column), the column modified with GO and silica nanoparticles through layer‐by‐layer method (GO‐SiO2 NPs@column), or the column modified with silica nanoparticles (SiO2 NPs@column), GO/SiO2 NPs@column possessed highest resolutions. The GO/SiO2 NPs@column was applied to separate egg white and both acidic and basic proteins as well as three glycoisoforms of ovalbumin were separated in a single run within 36 min. The intra‐day, inter‐day, and column‐to‐column reproducibilities were evaluated by calculating the RSDs of the retention of naphthalene and biphenyl in open‐tubular capillary electrochromatography. The RSD values were found to be less than 7.1%. 相似文献
994.
Changming Cheng Tao Jiang Jun Han Kai Lv Sheng Hu Xiaolin Wang 《Electrophoresis》2016,37(20):2657-2662
In this study, in‐column fiber‐optic (ICFO) laser‐induced fluorescence (LIF) detection technique is coupled with capillary electrophoresis (CE) for the rapid separation of neodymium for the first time. The effects of buffer concentration, buffer pH, and separation voltage on the CE behaviors, including electrophoretic efficiency and detection sensitivity, are investigated in detail. Under the optimal condition determined in this study (15 mM borate buffer, pH 10.50, separation voltage 24 kV), neodymium could be separated effectively from the neighboring lanthanides (praseodymium and samarium) within several minutes, and the limit of detection for neodymium is estimated to be at the ppt level. The ICFO‐LIF‐CE system assembled in this study exhibits unique performance characteristics such as low cost and flexibility. Meanwhile, the separation efficiency and detection sensitivity of the assembled CE system are comparable to or somewhat better than those obtained in the previous traditional CE systems, indicating the potential of the assembled CE system for practical applications in the fields of spent nuclear fuel analysis, nuclear waste disposal/treatment, and nuclear forensics. 相似文献
995.
Yao Qian Zhiyue Han Yinghao Zhang Zhiming Du Yan Zhao Yuezhen Yang Jingchang Zhang 《Journal of heterocyclic chemistry》2016,53(2):651-657
1,5‐diaminotetrazolium chloride (DATC) and 1,5‐diaminotetrazolium sulfate (DATS) were synthesized in this work. The structures of DATS and DATC were characterized. The single crystal of DATS was first cultured, and its structure was analyzed. The thermal behavior of DATS was investigated. The activation energy and pro‐exponential factor were calculated, Ek = 120.86 KJ/mol, Ak = 1012.96 s?1. The density, heat of formation, detonation pressure, and detonation velocity of DATS were first calculated. The detonation pressure and detonation velocity of DATS are P = 11.877 GPa, D = 5.617 km s?1, which are smaller than those of 1,5‐diaminotetrazolium nitrate (DATN) (P = 33.3GPa, D = 8.77 km s?1). 相似文献
996.
Screening anaphylactic components of MaiLuoNing injection by using rat basophilic leukemia‐2H3 cell membrane chromatography coupled with HPLC–ESI‐TOF‐MS 下载免费PDF全文
Shengli Han Yanni Lv Wenjing Xue Jiao Cao Ronghua Cui Tao Zhang 《Journal of separation science》2016,39(3):466-472
MaiLuoNing injection is a traditional Chinese medicine that used clinically since the 1950s in China. However, anaphylactic reactions, through the potentiation of mast cell degranulation, have been reported. In the present study, a rat basophilic leukemia‐2H3 cell membrane chromatography coupled with high‐performance liquid chromatography and electrospray ionization‐ion trap‐time of flight‐mass spectrometry method was established for screening, analyzing, and identifying the potential anaphylactic components of MaiLuoNing injection. Harpagoside, a potential degranulator of rat basophilic leukemia‐2H3 cells, was retained in rat basophilic leukemia‐2H3 cell membrane chromatography. We aimed to evaluate the retained components to determine which of those were capable of inducing degranulation of basophilic leukemia cells. A β‐hexosaminidase assay revealed that harpagoside can induce rat basophilic leukemia‐2H3 cell degranulation in a dose‐dependent manner. BLBA/c mice also exhibit passive cutaneous anaphylaxis in response to harpagoside. These results indicate that rat basophilic leukemia‐2H3 cell membrane chromatography coupled with high‐performance liquid chromatography and electrospray ionization ion trap time‐of‐flight mass spectrometry is effective in screening for the anaphylactic components of MaiLuoNing injection. 相似文献
997.
Assessment of Polygonum capitatum Buch.‐Ham. ex D.Don by metabolomics based on gas chromatography with mass spectrometry 下载免费PDF全文
Pei Han Yong Huang Peter J. Hylands Cristina Legido‐Quigley 《Journal of separation science》2016,39(10):1979-1986
Polygonum capitatum is widely used in southwest China. It has considerable therapeutic efficacy for urinary tract infections. P. capitatum contains multiple components and quality assessment can be achieved by means of metabolic fingerprinting. In this paper, a new strategy for P. capitatum quality determination was developed. Eleven batches of P. capitatum were collected from five geographical areas in China including a standard batch regulated by Good Agriculture Practice. Gas chromatography with mass spectrometry was used to generate fingerprints from triplicate extractions to each batch (n = 33). Hierarchical clustering analysis was applied to assess similarities among the ten batches to the standard batches. Orthogonal projection to latent structures discriminate analysis, cross‐validated with permutation tests, was performed to investigate discriminating metabolites. Results demonstrated that the overall evaluation hierarchical clustering analysis clustered two batches with distance > 3. Orthogonal projection to latent structures discriminate analysis (R2Y (cum) = 0.997, Q2 (cum) = 0.97, CV‐ANOVA = 8.48 × 10?11) indicated that several sugars contributed to batch classification. This method is a rational approach that can classify against a regulated plant standard and distinguishes samples from different origins or processing time in a holistic manner and metabolites driving any differences can be easily identified. 相似文献
998.
Jae-Hyun Yang Tae-Yang Song Chanhee Jo Jinyoung Park Han-Young Lee Ilang Song Suji Hong Kwan Young Jung Jaehoon Kim Jeung-Whan Han Hong-Duk Youn Eun-Jung Cho 《Experimental & molecular medicine》2016,48(8):e252
Replication-independent incorporation of variant histone H3.3 has a profound impact on chromatin function and numerous cellular processes, including the differentiation of muscle cells. The histone chaperone HIRA and H3.3 have essential roles in MyoD regulation during myoblast differentiation. However, the precise mechanism that determines the onset of H3.3 deposition in response to differentiation signals is unclear. Here we show that HIRA is phosphorylated by Akt kinase, an important signaling modulator in muscle cells. By generating a phosphospecific antibody, we found that a significant amount of HIRA was phosphorylated in myoblasts. The phosphorylation level of HIRA and the occupancy of phosphorylated protein on muscle genes gradually decreased during cellular differentiation. Remarkably, the forced expression of the phosphomimic form of HIRA resulted in reduced H3.3 deposition and suppressed the activation of muscle genes in myotubes. Our data show that HIRA phosphorylation limits the expression of myogenic genes, while the dephosphorylation of HIRA is required for proficient H3.3 deposition and gene activation, demonstrating that the phosphorylation switch is exploited to modulate HIRA/H3.3-mediated muscle gene regulation during myogenesis. 相似文献
999.
The ordering configurations of a fluid of anisotropic ellipsoids under the confinement of two apposing impenetrable walls are studied by Monte Carlo simulations. The excess adsorption of the fluid on the walls with respect to the aspect ratio has a maximum at the critical aspect ratio of 2.9 in high-density ellipsoid fluids, indicating an orientational ordering in the adjacent region of the walls, which is confirmed by probing into the density configurations and the orientational order parameter in the adjacent region of the walls for varying aspect ratios. In addition, the orientational order parameter in the bulk fluid at the same density is calculated, and it indicates an isotropic state as the bulk density is still below the bulk isotropic-to-nematic transition. Therefore, it can be concluded that the anisotropic ordering near the walls in the ellipsoid fluid that exhibits isotropic in the bulk is induced by the confinement effect of the walls. 相似文献
1000.
Bing Han Li Zhang Samuel J. Kyran Binyuan Liu Zhongyu Duan Donald J. Darensbourg 《Journal of polymer science. Part A, Polymer chemistry》2016,54(13):1938-1944
Chromium complexes supported by tetradentate dianionic imine‐thioether‐bridged bis(phenol) ligands were prepared and employed in the synthesis of poly(cyclohexene carbonate) via the copolymerization of CO2 and cyclohexene oxide. The catalytic activity, product selectivity, and kinetic behaviors of these [ONSO]CrIII complexes have been systematically investigated. Results indicate the presence of electron‐withdrawing substituents on the ligands to enhance catalytic activity and polymer selectivity. A turnover frequency of 100 h?1 is observed at a temperature of 110 °C, producing polycarbonate with >60% selectivity. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 1938–1944 相似文献