全文获取类型
收费全文 | 27198篇 |
免费 | 862篇 |
国内免费 | 157篇 |
专业分类
化学 | 18227篇 |
晶体学 | 255篇 |
力学 | 926篇 |
综合类 | 1篇 |
数学 | 2346篇 |
物理学 | 6462篇 |
出版年
2023年 | 154篇 |
2022年 | 410篇 |
2021年 | 494篇 |
2020年 | 432篇 |
2019年 | 448篇 |
2018年 | 333篇 |
2017年 | 317篇 |
2016年 | 727篇 |
2015年 | 631篇 |
2014年 | 793篇 |
2013年 | 1490篇 |
2012年 | 1951篇 |
2011年 | 2135篇 |
2010年 | 1295篇 |
2009年 | 1143篇 |
2008年 | 1741篇 |
2007年 | 1644篇 |
2006年 | 1533篇 |
2005年 | 1428篇 |
2004年 | 1262篇 |
2003年 | 984篇 |
2002年 | 967篇 |
2001年 | 672篇 |
2000年 | 575篇 |
1999年 | 338篇 |
1998年 | 252篇 |
1997年 | 293篇 |
1996年 | 334篇 |
1995年 | 257篇 |
1994年 | 274篇 |
1993年 | 278篇 |
1992年 | 264篇 |
1991年 | 204篇 |
1990年 | 154篇 |
1989年 | 139篇 |
1988年 | 140篇 |
1987年 | 118篇 |
1986年 | 95篇 |
1985年 | 169篇 |
1984年 | 112篇 |
1983年 | 97篇 |
1982年 | 123篇 |
1981年 | 88篇 |
1980年 | 79篇 |
1978年 | 80篇 |
1977年 | 85篇 |
1976年 | 94篇 |
1975年 | 101篇 |
1974年 | 79篇 |
1973年 | 102篇 |
排序方式: 共有10000条查询结果,搜索用时 9 毫秒
991.
Chester M. Mikulski Scott Grossman Chung Ja Lee Nicholas M. Karayannis 《Transition Metal Chemistry》1987,12(1):21-25
Summary Complexes of the general types Pd(L)(LH)Cl (LH=hxH, xnH, or tbH) and Pt(L)(LH)Cl3 (LH=hxH, or xnH) are formed by boiling under reflux 21 molar mixtures of hypoxanthine (hxH), xanthine (xnH) or theobromine (tbH) and PdCl2 or PtCl4 in ethanol-triethyl orthoformate. These complexes appear to be linear chain polymeric species, characterized by single monoanionic L– ligands bridging between adjacent Pd2+ or Pt4+ ions. Inclusion of one terminal neutral LH and one terminal chloro-ligand completes the coordination sphere in the square-planar Pd2+ complexes, while the Pt4+ complexes aretrans-octahedral, involving three terminal chloro and one terminal LH ligand per platinum. The possible binding sites of the bidentate bridging L– and the unidentate terminal LH are discussed. 相似文献
992.
S. Salaymeh S. C. Lee P. K. Kuroda 《Journal of Radioanalytical and Nuclear Chemistry》1987,111(1):147-155
Radiochemical measurements of239,240Pu were carried out for a total of 57 individual rain and snow samples collected at Fayetteville (36 °N, 94 °W), Arkansas, during the period between November 1984 and June 1986. The results indicate that the fallout of plutonium observed during the past three years is due, primarily, to the nuclear debris originating from the 7 February 1983 burn-up of the nuclear-powered Soviet satellite Cosmos-1402.This investigation was supported by the National Science Foundation under Grant ATM 84-07618. 相似文献
993.
Julie P. Harmon Sanboh Lee J. C. M. Li 《Journal of polymer science. Part A, Polymer chemistry》1987,25(12):3215-3229
The effect of cold work on the transport of liquid methanol in crosslinked PMMA disks has been determined at temperatures from 35–56°C. Deformed samples absorb at fast rates with kinetics that approach those of Fickian diffusion. Undeformed samples sorb at lower rates and the kinetics tend toward those of Case II transport. Shape recovery accompanied swelling in deformed samples. Samples saturated with methanol were desorbed in cyclohexanol. Resorption of desorbed samples showed fast rates for both deformed and undeformed samples and matched those of the absorption cycle in deformed samples. An analogy is made between the microstructure due to cold work and due to swelling. 相似文献
994.
995.
Chi-So Lee 《中国化学会会志》1987,34(3):207-210
A differential pulse polarographic method for the determination of nitrate ion has been developed. With 0.5 M CaCl2 as supporting electrolyte, NO?3 is reduced to give a peak with E1/2=–1.836 Volt vs. the Ag/AgCl electrode. The differential pulse polarographic peak height is proportional to the nitrate concentration from 20 to 60 ppm. The detection limit for nitrate is 2 ppm in pure aqueous solution. In the determination of 40 ppm nitrate a relative precision (relative standard deviation) of less than 2% was achieved. Nitrite interferes seriously and should be absent if accurate results are required. The method has been applied to the determination of nitrate in Ammonium Uranyl Tricarbonate (AUT) Solution, results obtained by this method are compared to those obtained by ion chromatography. The agreement between the two sets of results suggests that the DPP method can be used with a fair degree of confidence. 相似文献
996.
Kazufumi Takahashi Raymond N. Castle Milton L. Lee 《Journal of heterocyclic chemistry》1987,24(4):977-979
The four acridinecarbaldehydes, namely, acridine-1-carbaldehyde, acridine-2-carbaldehyde, acridine-3-carbaldehyde, and acridine-4-carbaldehyde have been synthesized for the first time. 相似文献
997.
Hong-Bing Tsai Yu-Der Lee 《Journal of polymer science. Part A, Polymer chemistry》1987,25(8):2195-2206
The kinetics of interfacial polycondensation of bisphenol A with isophthaloyl chloride and terephthaloyl chloride in dichloromethane with triethylbenzylammonium chloride (TEBAC) as the catalyst was investigated via measurements of bisphenolate concentration by UV. The reaction was found to be second order with respect to bisphenolate. The dependence of the rate constant on stirring speed, amount of TEBAC, and reaction temperature was studied. The rate constant was increased with an increase of stirring speed, quantity of TEBAC added, as well as the reaction temperature. The activation energy was found to be 7.7 kcal/mol at a stirring speed of 700 rpm in the presence of 0.160 of TEBAC. The role of TEBAC was found to be interesting. It did not alter the equilibrium (the partition coefficient remained the same in the presence of TEBAC), but it did enhance the transfer rate of bisphenolate. 相似文献
998.
Xiaona Rong Nabila Mehwish Xueming Niu Niteng Zhu Bae Hoon Lee 《Macromolecular bioscience》2023,23(3):2200463
Nowadays, hydrogels-based microneedles (MNs) have attracted a great interest owing to their outstanding qualities for biomedical applications. For the fabrication of hydrogels-based microneedles as tissue engineering scaffolds and drug delivery carriers, various biomaterials have been tested. They are required to feature tunable physiochemical properties, biodegradability, biocompatibility, nonimmunogenicity, high drug loading capacity, and sustained drug release. Among biomaterials, human proteins are the most ideal biomaterials for fabrication of hydrogels-based MNs; however, they are mechanically weak and poorly processible. To the best of the knowledge, there are no reports of xeno-free human protein-based MNs so far. Here, human albumin-based hydrogels and microneedles for tissue engineering and drug delivery by using relatively new processible human serum albumin methacryloyl (HSAMA) are engineered. The resultant HSAMA hydrogels display tunable mechanical properties, biodegradability, and good biocompatibility. Moreover, the xeno-free HSAMA microneedles display a sustained drug release profile and significant mechanical strength to penetrate the model skin. In vitro, they also show good biocompatibility and anticancer efficacy. Sustainable processible human albumin-based biomaterials may be employed as a xeno-free platform in vivo for tissue engineering and drug delivery in clinical trials in the future. 相似文献
999.
Alexandre Chappard Dr. Craig Leighton Dr. Rebecca S. Saleeb Kiani Jeacock Dr. Sarah R. Ball Katie Morris Owen Kantelberg Dr. Ji-Eun Lee Dr. Elsa Zacco Prof. Dr. Annalisa Pastore Prof. Dr. Margaret Sunde Dr. David J. Clarke Dr. Patrick Downey Prof. Dr. Tilo Kunath Dr. Mathew H. Horrocks 《Angewandte Chemie (International ed. in English)》2023,62(15):e202216771
Protein misfolding and aggregation into oligomeric and fibrillar structures is a common feature of many neurogenerative disorders. Single-molecule techniques have enabled characterization of these lowly abundant, highly heterogeneous protein aggregates, previously inaccessible using ensemble averaging techniques. However, they usually rely on the use of recombinantly-expressed labeled protein, or on the addition of amyloid stains that are not protein-specific. To circumvent these challenges, we have made use of a high affinity antibody labeled with orthogonal fluorophores combined with fast-flow microfluidics and single-molecule confocal microscopy to specifically detect α-synuclein, the protein associated with Parkinson's disease. We used this approach to determine the number and size of α-synuclein aggregates down to picomolar concentrations in biologically relevant samples. 相似文献
1000.
Dr. Huanhuan Shi Prof. Mengmeng Li Shuai Fu Dr. Christof Neumann Dr. Xiaodong Li Dr. Wenhui Niu Yunji Lee Prof. Mischa Bonn Dr. Hai I. Wang Prof. Andrey Turchanin Dr. Ali Shaygan Nia Dr. Sheng Yang Prof. Xinliang Feng 《Angewandte Chemie (International ed. in English)》2023,62(28):e202303929
Two-dimensional van der Waals heterostructures (2D vdWHs) have recently gained widespread attention because of their abundant and exotic properties, which open up many new possibilities for next-generation nanoelectronics. However, practical applications remain challenging due to the lack of high-throughput techniques for fabricating high-quality vdWHs. Here, we demonstrate a general electrochemical strategy to prepare solution-processable high-quality vdWHs, in which electrostatic forces drive the stacking of electrochemically exfoliated individual assemblies with intact structures and clean interfaces into vdWHs with strong interlayer interactions. Thanks to the excellent combination of strong light absorption, interfacial charge transfer, and decent charge transport properties in individual layers, thin-film photodetectors based on graphene/In2Se3 vdWHs exhibit great promise for near-infrared (NIR) photodetection, owing to a high responsivity (267 mA W−1), fast rise (72 ms) and decay (426 ms) times under NIR illumination. This approach enables various hybrid systems, including graphene/In2Se3, graphene/MoS2 and graphene/MoSe2 vdWHs, providing a broad avenue for exploring emerging electronic, photonic, and exotic quantum phenomena. 相似文献