全文获取类型
收费全文 | 525篇 |
免费 | 25篇 |
国内免费 | 1篇 |
专业分类
化学 | 447篇 |
晶体学 | 4篇 |
力学 | 11篇 |
数学 | 43篇 |
物理学 | 46篇 |
出版年
2022年 | 10篇 |
2021年 | 16篇 |
2020年 | 8篇 |
2019年 | 15篇 |
2018年 | 5篇 |
2017年 | 3篇 |
2016年 | 15篇 |
2015年 | 12篇 |
2014年 | 15篇 |
2013年 | 28篇 |
2012年 | 41篇 |
2011年 | 61篇 |
2010年 | 22篇 |
2009年 | 20篇 |
2008年 | 36篇 |
2007年 | 26篇 |
2006年 | 33篇 |
2005年 | 14篇 |
2004年 | 27篇 |
2003年 | 21篇 |
2002年 | 22篇 |
2000年 | 3篇 |
1999年 | 7篇 |
1998年 | 7篇 |
1997年 | 5篇 |
1996年 | 13篇 |
1995年 | 2篇 |
1994年 | 4篇 |
1993年 | 2篇 |
1992年 | 3篇 |
1989年 | 2篇 |
1988年 | 3篇 |
1985年 | 2篇 |
1984年 | 3篇 |
1983年 | 2篇 |
1982年 | 3篇 |
1981年 | 3篇 |
1980年 | 3篇 |
1979年 | 3篇 |
1978年 | 3篇 |
1977年 | 2篇 |
1975年 | 6篇 |
1958年 | 1篇 |
1941年 | 1篇 |
1935年 | 1篇 |
1932年 | 2篇 |
1913年 | 1篇 |
1908年 | 1篇 |
1907年 | 1篇 |
1902年 | 2篇 |
排序方式: 共有551条查询结果,搜索用时 15 毫秒
91.
Dana A. Weinberger Thomas B. Higgins Chad A. Mirkin Louise M. Liable-Sands Arnold L. Rheingold 《Angewandte Chemie (International ed. in English)》1999,38(17):2565-2568
By controlling the extent of oxidation of the polymeric forms of the new class of isolable, polymerizable terthienyl RuII complexes 1 , one can modulate both the binding strength of the polymer backbone for RuII and the electronic nature of the bound metal centers. 相似文献
92.
The First One‐Pot Synthesis of Metal–Organic Frameworks Functionalised with Two Transition‐Metal Complexes 下载免费PDF全文
Dr. Ana E. Platero‐Prats Dr. Antonio Bermejo Gómez Dr. Louise Samain Prof. Xiaodong Zou Prof. Belén Martín‐Matute 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(2):861-866
The synthesis of a metal–organic framework (UiO‐67) functionalised simultaneously with two different transition metal complexes (Ir and Pd or Rh) through a one‐pot procedure is reported for the first time. This has been achieved by an iterative modification of the synthesis parameters combined with characterisation of the resulting materials using different techniques, including X‐ray absorption spectroscopy (XAS). The method also allows the first synthesis of UiO‐67 with a very wide range of loadings (from 4 to 43 mol %) of an iridium complex ([IrCp*(bpydc)(Cl)Cl]2?; bpydc=2,2′‐bipyridine‐5,5′‐dicarboxylate, Cp*=pentamethylcyclopentadienyl) through a pre‐functionalisation methodology. 相似文献
93.
94.
A simplex procedure is shown to be an efficient approach for solving separation problems. The best solvent ratio for the separation of phosphatidylcholine and sphingomyelin has been found by means of a two-dimensional simplex capable of expansion and contraction. A successful high-pressure liquid chromatography separation of lysophosphatidylcholine, phoaphatidylethanolamine, phosphatidylinositol, phosphatidylserine, phosphatidylcholine, sphingomyelin and phosphatidic acid was achieved with a 180-cm column packed with Corasil II and a solvent mixture of chloroform—methanol—ammonia (50.0:35.9:7.0, v/v/v). 相似文献
95.
Kenneth P. Ghiggino Louise E. Bennett Robert W. Henderson 《Photochemistry and photobiology》1988,47(1):65-72
Abstract— The absorption and fluorescence properties of porphyrin c (P c ), the porphyrin chromophore present in cytochrome c , have been determined in several solvents and micellar environments. In aqueous buffer solutions at pH 7.5 Pc may exist in both a fluorescent monomeric form with quantum yield of fluorescence, (Φf ,) ∼ 0.03, and fluorescence lifetime, (τf ) ∼ 8 ns, and as a non-fluorescent aggregate. The proportion of monomeric form is higher in organic solvents and micelles but is reduced with increasing porphyrin concentrations in aqueous solutions. Porphyrin c readily complexes with Zn2+ to produce a fluorescent chelate (Zn-P c ) with Φf , ∼ 0.02 and τf , ∼ 2 ns at pH 7.5. The yields of singlet excited oxygen formation from Pc and the Zn-P c complex are higher than observed for hematoporphyrin derivative (HpD). Both P c and Zn-P c are effective agents in tumor phototherapy and do not induce the prolonged cutaneous photosensitivity observed with the use of HpD. 相似文献
96.
Fabien Joux Wade H. Jeffrey Maher Abboudi Jacques Neveux Mireille Pujo-Pay Louise Oriol Jean-Jacques Naudin 《Photochemistry and photobiology》2009,85(3):783-793
The high content in nutrients of freshwater outflows induces highly productive and buoyant plumes spreading over marine waters (MW). As a consequence, the growth of organisms developing in these low‐salinity waters (LSW) might be potentially affected by UV‐R (280–400 nm). This study investigated the penetration of UV‐R and its impact on net community production (NCP) and bacterial protein (BPROTS) and DNA (BDNAS) synthesis in mesotrophic‐LSW formed from the Rhône River and in oligotrophic MW of the Northwestern Mediterranean Sea (Gulf of Lions) in May 2006. High concentrations of chlorophyll a (up to 8 μg L?1) measured in the LSW (<37.8 psu, 0–10 m) were the main factor influencing the diffuse attenuation coefficients (Kd) of both UV‐R and photosynthetically active radiation (PAR). The mean ratio of the Kd measured between the LSW and the MW increased with wavelength from 2.4 at 305 nm to 2.9 at 380 nm and 3.1 for PAR indicating more similarity in the UV region. NCP was severely inhibited by UV‐R at the surface of the LSW, whereas no effect was measured in the surrounding MW. In contrast, BPROTS and BDNAS were affected deeper by UV‐R in the MW (up to 8 m depth) compared to the LSW where inhibition was only observed at the surface. Differences in response of bacteria in LSW and MW are largely explained by differences in UV‐R transparency; however, transplant experiments indicate that bacterial assemblages from the MW were also more sensitive to UV‐R than those present in the LSW. We also observed that higher activity of bacteria after nutrient additions increased their sensitivity to UV‐R during the day, but favored their recovery during the night incubation period for both LSW and MW. Results suggest that riverine and nutrient inputs may alter the effects of UV‐R on microbial activity by attenuating the UV‐R penetration and by modifying the physiology of bacteria. 相似文献
97.
Duncan TV Susumu K Sinks LE Therien MJ 《Journal of the American Chemical Society》2006,128(28):9000-9001
We show that meso-to-meso ethyne-bridged (porphinato)zinc(II) oligomers (PZnn structures) define exceptional low band gap organic materials that possess both large magnitude NIR S1 --> S0 fluorescence quantum yields and substantial S1 --> Sn absorptive cross-sections, tunable over a wide 850-1400 nm spectral window. These PZnn species possess fluorescence quantum yields (phif values) comparable to the highest reported for NIR laser dyes in the 750-900 nm regime; importantly, these emitters do not suffer from commonly cited tricarbocyanine dye drawbacks of poor photostability and substantial phif sensitivity to solvent polarity. Furthermore, tauo (kr-1) values determined using the Strickler-Berg method highlight the close correlation of fluorescence quantum yields with S0 --> S1 integrated oscillator strength and demonstrate a rare if not unique example of broad NIR spectral domain fluorescence energy modulation, where phif magnitudes follow a simple Strickler-Berg relationship. 相似文献
98.
de la Riva H Nieuwhuyzen M Mendicute Fierro C Raithby PR Male L Lagunas MC 《Inorganic chemistry》2006,45(4):1418-1420
Changes in the optical properties of an alkynyldigold(I) complex upon reaction with Cu(I) are associated with a complicated structural change to form an unusual Au4Cu2 cluster with metallophilic interactions as well as pi-alkyne coordination. 相似文献
99.
The valence state of iron in minerals has useful applications in the geosciences for estimating redox conditions during mineral formation or re-equilibration. STEM/EELS techniques offer the advantage over other methods of being able to measure Fe valence with very high spatial resolution across mineral grains and grain boundaries. We have modified an EELS method for point analyses of iron valence ratios (Fe(3+)/SigmaFe) making it possible to generate line scans and maps of Fe valence. We demonstrate this method with measurements at an interface between iron-bearing oxides in a finely intergrown sample of magnetite and ilmenite. The STEM/EELS method is based on a calibrated relationship between Fe(3+)/SigmaFe and the relative intensities of the Fe L(3) and L(2) white lines in core energy-loss spectra for oxide and silicate minerals. Our method overcomes problems of energy drift in spectrum images by aligning energy-loss edges at a fixed energy position prior to background removal. An automated routine for batch processing of core loss spectra, including additional background removal and calculation of Fe L(3)/L(2) intensity ratios, allows for rapid Fe(3+)/SigmaFe determinations of multiple point analyses or spectrum images and the preparation of Fe valence maps, with an analytical error of +/-0.05 to +/-0.09 in the Fe(3+)/SigmaFe measurements. 相似文献
100.
Mukarram H. Zaghal Hanan A. Qaseer Arab K. El-Qisairi Solhe F. Alshahateet Mazin Y. Shatnawi Louise N. Dawe 《Journal of chemical crystallography》2009,39(8):564-567
Abstract The X-ray structure of 6,7-dihydro-1,4-di(2′-pyridyl)-5H-cyclopenta[d]pyridazine ligand (5-dppn) shows the existence of a trans/trans conformation. The 5-dppn crystallizes in a triclinic space group P-1 with a = 7.1048(15) ?; b = 9.008(2) ?; c = 10.986(3) ?; α = 88.279(16)°; β = 85.454(15)°; γ = 69.104(12)°; V = 654.7(3) ?3 and Z = 2. The analysis of 5-dppn crystal structure demonstrates the presence of edge-edge Ar–H···N and face-face Aliph-H···N centrosymmetric
dimer interactions. The unit cell packing arrangement confirmed the presence of two molecules opposite to each other.
Index Abstract The X-ray structure of 6,7-dihydro-1,4-di(2′-pyridyl)-5H-cyclopenta[d]pyridazine ligand (5-dppn) shows the existence of a trans/trans conformation.
相似文献