全文获取类型
收费全文 | 951篇 |
免费 | 40篇 |
国内免费 | 4篇 |
专业分类
化学 | 780篇 |
晶体学 | 9篇 |
力学 | 16篇 |
数学 | 35篇 |
物理学 | 155篇 |
出版年
2023年 | 7篇 |
2022年 | 12篇 |
2020年 | 24篇 |
2019年 | 18篇 |
2018年 | 7篇 |
2017年 | 6篇 |
2016年 | 13篇 |
2015年 | 24篇 |
2014年 | 21篇 |
2013年 | 48篇 |
2012年 | 49篇 |
2011年 | 67篇 |
2010年 | 34篇 |
2009年 | 31篇 |
2008年 | 58篇 |
2007年 | 45篇 |
2006年 | 57篇 |
2005年 | 46篇 |
2004年 | 48篇 |
2003年 | 35篇 |
2002年 | 30篇 |
2001年 | 17篇 |
2000年 | 10篇 |
1999年 | 17篇 |
1998年 | 17篇 |
1997年 | 11篇 |
1996年 | 9篇 |
1995年 | 6篇 |
1994年 | 8篇 |
1993年 | 6篇 |
1992年 | 11篇 |
1991年 | 6篇 |
1990年 | 7篇 |
1989年 | 6篇 |
1988年 | 6篇 |
1987年 | 8篇 |
1986年 | 5篇 |
1985年 | 21篇 |
1984年 | 16篇 |
1983年 | 15篇 |
1982年 | 16篇 |
1981年 | 10篇 |
1980年 | 11篇 |
1979年 | 16篇 |
1978年 | 7篇 |
1977年 | 12篇 |
1976年 | 12篇 |
1975年 | 6篇 |
1974年 | 7篇 |
1973年 | 6篇 |
排序方式: 共有995条查询结果,搜索用时 31 毫秒
141.
Dr. Yoji Horii Prof. Dr. Keiichi Katoh Prof. Dr. Yuji Miyazaki Dr. Marko Damjanović Tetsu Sato Prof. Dr. Liviu Ungur Prof. Dr. Liviu F. Chibotaru Prof. Dr. Brian K. Breedlove Prof. Dr. Motohiro Nakano Prof. Dr. Wolfgang Wernsdorfer Prof. Dr. Masahiro Yamashita 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(36):8076-8082
Gd3+ complexes have been shown to undergo unusual slow magnetic relaxation processes similar to those of single-molecule magnets (SMMs), even though Gd3+ does not exhibit strong magnetic anisotropy. To reveal the origin of the slow magnetic relaxation of Gd3+ complexes, we have investigated the magnetic properties and heat capacities of two Gd3+-phthalocyaninato triple-decker complexes, one of which has intramolecular Gd3+–Gd3+ interactions and the other does not. It was found that the Gd3+–Gd3+ interactions accelerate the magnetic relaxation processes. In addition, magnetically diluted samples, prepared by doping a small amount of the Gd3+ complexes into a large amount of diamagnetic Y3+ complexes, underwent dual magnetic relaxation processes. A detailed dynamic magnetic analysis revealed that the coexistence of spin–lattice relaxation and phonon-bottleneck processes is the origin of the dual magnetic relaxation processes. 相似文献
142.
143.
Qiang Chen Dr. Luigi Brambilla Dr. Lakshya Daukiya Dr. Kunal S. Mali Prof. Dr. Steven De Feyter Prof. Matteo Tommasini Prof. Dr. Klaus Müllen Dr. Akimitsu Narita 《Angewandte Chemie (International ed. in English)》2018,57(35):11233-11237
Two unprecedented porphyrin fused nanographene molecules, 1 and 2 , have been synthesized by the Scholl reaction from tailor‐made precursors based on benzo[m]tetraphene‐substituted porphyrins. The chemical structures were validated by a combination of high‐resolution matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry (HR MALDI‐TOF MS), IR and Raman spectroscopy, and scanning tunnelling microscopy (STM). The UV‐vis‐near infrared absorption spectroscopy of 1 and 2 demonstrated broad and largely red‐shifted absorption spectra extending up to 1000 and 1400 nm, respectively, marking the significant extension of the π‐conjugated systems. 相似文献
144.
Ohuchi Shokichi Nakamura Hiroyuki Sligiura Hlroto Narita Mltsuaki Sode Koji 《Applied biochemistry and biotechnology》1997,(1):659-665
Conclusion We have shown that PTE chiral recognition is limited to organophosphorous esters having the chiral center on the phosphorous
atoms, which is attacked with nucleophile, not having the chiral center on the other atoms of the leaving group. Therefore,
PTE can be utilized for the synthesis of their chiral organophosphorous esters. 相似文献
145.
Okada S Arayama K Murayama R Ishizuka T Hara K Hirone N Hata T Urabe H 《Angewandte Chemie (International ed. in English)》2008,47(36):6860-6864
146.
147.
Hazra P Inoue K Laan W Hellingwerf KJ Terazima M 《The journal of physical chemistry. B》2008,112(5):1494-1501
A recently developed method for time-resolved thermodynamic measurements was used to study the photochemical reaction(s) of the BLUF domain of AppA (AppA-BLUF), which has a dimeric form in the ground state, in terms of the energetics and heat capacity changes (DeltaC(p)) in different time domains. The enthalpy change (DeltaH) of the first intermediate that forms within 1 ns after photoexcitation was 38 (+/-8) kJ mol(-1) at 298 K. The heat capacity change (DeltaC(p)) upon formation of this intermediate was positive [1.4 (+/-0.3) kJ mol(-1) K(-1)]. This positive DeltaC(p) suggests that the hydrophobic surface area of AppA-BLUF exposed to the bulk solvent increased. After this initial transition, a dimerization reaction with another ground-state dimer (i.e., tetramer formation) takes place. Upon this reaction, the energy was stabilized to 26 (+/-6) kJ mol(-1) at 298 K. Interestingly, the dimer formation was accompanied by a larger but negative DeltaC(p) [-6.0 (+/-1) kJ mol(-1) K(-1)]. This negative DeltaC(p) might indicate buried hydrophobic residues at the interface of the dimer and/or the existence of trapped water at the interface. We suggest that hydrophobic interactions are the main driving force for the formation of the dimer upon photoactivation of AppA-BLUF. 相似文献
148.
Volatile acidic solutes were used to make dilute solutions, which were frozen by various methods. The concentration of solutes and the pH of the samples were measured before and after being frozen. When the sample solution is frozen from the bottom to the top, solutes are concentrated into the unfrozen solution (i.e., the upper part of the sample) due to the freeze concentration effect. Thereafter, concentrated anions combine with protons to form acids, and the amount of acids in the unfrozen solution increase as the ice formation progresses. At the end of freezing, the acid is saturated at the ice surface, and if the formed acid is volatile, then evaporation occurs. Frozen solutions were allowed to stand below 0 degrees C, where evaporation rates were obtained in the following order: formate > acetate > propionate > n-butyrate > chloride > nitrate. Except for nitrate, evaporation rates were enough to take place in frozen water of the natural environment (e.g., ice crystal, graupel, snow crystal, and frozen droplets). The relationship between the evaporation rate of volatile acids and their physical properties demonstrate that the evaporation rates of weak acids are faster than those of strong acids, and the evaporation rates among weak acids are the same as the volatility of weak acids. 相似文献
149.
Yokoyama A Katsumata K Ohba H Akagi H Saeki M Yokoyama K 《The journal of physical chemistry. A》2008,112(29):6571-6577
Oxygen isotopic selectivity on infrared multiphoton dissociation of 2,3-dihydropyran has been studied by the examination of the effects of excitation frequency, laser fluence, and gas pressure on the dissociation probability of 2,3-dihydropyran and isotopic composition of products. Oxygen-18 was enriched in a dissociation product: 2-propenal. The enrichment factor of 18O and the dissociation probability were measured at a laser frequency between 1033.5 and 1057.3 cm-1, the laser fluence of 2.2-2.3 J/cm2, and the 2,3-dihydropyran pressure of 0.27 kPa. The dissociation probability decreases as the laser frequency being detuned from the absorption peak of 2,3-dihydropyran around 1081 cm-1. On the other hand, the enrichment factor increases with detuning the frequency. The enrichment factor of 18O increases with increasing the 2,3-dihydropyran pressure at the laser fluence of 2.7 J/cm2 or less and the laser frequency of 1033.5 cm-1, whereas the yield of 2-propenal decreases with increasing the pressure. A very high enrichment factor of 751 was obtained by the irradiation of 0.53 kPa of 2,3-dihydropyran at 2.1 J/cm2. Collisional effect of vibrationally excited molecules with ambient molecules on isotopic selectivity is discussed on the basis of a rate equation model including a collisional vibrational de-excitation process. 相似文献
150.
Takashima H Kawahara H Kitano M Shibata S Murakami H Tsukahara K 《The journal of physical chemistry. B》2008,112(48):15493-15502
The reconstituted zinc-myoglobin (ZnMb) dyads, ZnMb-[M(II)(edta)], have been prepared by incorporating a zinc-porphyrin (ZnP) cofactor modified with ethylenediaminetetraacetic acid (H(4)edta) into apo-Mb. In case of the monomeric ZnP(edta) cofactor coordinated by one pyridine molecule, ZnP(py)(edta), a spontaneous 1:1 complex with a transient metal ion was formed in an aqueous solvent, and the photoexcited singlet state of ZnP, (1)(ZnP)*, was quenched by the [Cu(II)(edta)] moiety through intramolecular photoinduced electron-transfer (ET) reaction. The rate constant for the intramolecular quenching ET (k(q)) at 25 degrees C was successfully obtained as k(q) = 5.1 x 10(9) s(-1). In the case of Co(2+), Ni(2+), and Mn(2+), intersystem crossing by paramagnetic effect was mainly considered between (1)(ZnP)* and the [M(II)(edta)] complex. For the ZnMb-[M(II)(edta)] systems, the intramolecular ET reaction between the excited singlet state of (1)(ZnMb)* and the [Cu(II)(edta)] moieties provided the slower quenching rate constant, k(q) = 2.1 x 10(8) s(-1), compared with that of the ZnP(py)(edta) one. Kinetic studies also presented the efficient fluorescence quenching of the (1)(ZnMb)*-[Co(II)(edta)] dyad. Our study clearly demonstrates that wrapping of the ZnP cofactor by the apoprotein matrix and synthetic manipulation at the Mb surface ensure metal ion-sensitive fluorescent dynamics of ZnMb and provides valuable information to elucidate the complicated mechanism of the biological photoinduced ET reactions of hemoproteins. 相似文献