全文获取类型
收费全文 | 871篇 |
免费 | 26篇 |
国内免费 | 7篇 |
专业分类
化学 | 547篇 |
晶体学 | 7篇 |
力学 | 23篇 |
数学 | 135篇 |
物理学 | 192篇 |
出版年
2023年 | 6篇 |
2021年 | 15篇 |
2020年 | 12篇 |
2019年 | 16篇 |
2018年 | 8篇 |
2016年 | 21篇 |
2015年 | 10篇 |
2014年 | 19篇 |
2013年 | 19篇 |
2012年 | 37篇 |
2011年 | 45篇 |
2010年 | 23篇 |
2009年 | 17篇 |
2008年 | 44篇 |
2007年 | 37篇 |
2006年 | 48篇 |
2005年 | 48篇 |
2004年 | 39篇 |
2003年 | 30篇 |
2002年 | 31篇 |
2001年 | 18篇 |
2000年 | 49篇 |
1999年 | 28篇 |
1998年 | 8篇 |
1997年 | 7篇 |
1995年 | 8篇 |
1993年 | 9篇 |
1992年 | 10篇 |
1991年 | 8篇 |
1990年 | 5篇 |
1989年 | 7篇 |
1988年 | 7篇 |
1987年 | 9篇 |
1986年 | 8篇 |
1985年 | 6篇 |
1984年 | 8篇 |
1983年 | 13篇 |
1982年 | 15篇 |
1981年 | 9篇 |
1980年 | 10篇 |
1979年 | 13篇 |
1978年 | 7篇 |
1977年 | 8篇 |
1976年 | 6篇 |
1975年 | 9篇 |
1974年 | 9篇 |
1973年 | 10篇 |
1970年 | 5篇 |
1969年 | 7篇 |
1959年 | 5篇 |
排序方式: 共有904条查询结果,搜索用时 15 毫秒
51.
Inside Back Cover: Self‐Assembly of a 3d–5f Trinuclear Single‐Molecule Magnet from a Pentavalent Uranyl Complex (Angew. Chem. Int. Ed. 49/2014) 下载免费PDF全文
52.
Wenjun Yang Bo Ling Bowen Hu Haolin Yin Jianyou Mao Patrick J. Walsh 《Angewandte Chemie (International ed. in English)》2020,59(1):161-166
An umpolung 1,4‐addition of aryl iodides to enals promoted by cooperative (terpy)Pd/NHC catalysis was developed that generates various bioactive β,β‐diaryl propanoate derivatives. This system is not only the first reported palladium‐catalyzed arylation of NHC‐bound homoenolates but also expands the scope of NHC‐induced umpolung transformations. A diverse array of functional groups such as esters, nitriles, alcohols, and heterocycles are tolerated under the mild conditions. This method also circumvents the use of moisture‐sensitive organometallic reagents. 相似文献
53.
B. M. Walsh 《Laser Physics》2010,20(3):622-634
Dual wavelength lasers are discussed, covering fundamental aspects on the spectroscopy and laser dynamics of these systems.
Results on Tm:Ho:Er:YAG dual wavelength laser action (Ho at 2.1 μm and Er at 2.9 μm) as well as Nd:YAG (1.06 and 1.3 μm) are
presented as examples of such dual wavelength systems. Dual wavelength lasers are not common, but there are criteria that
govern their behavior. Based on experimental studies demonstrating simultaneous dual wavelength lasing, some general conclusions
regarding the successful operation of multi-wavelength lasers can be made. 相似文献
54.
Control of chemoselectivity is one of the most challenging problems facing chemists and is particularly important in the synthesis of bioactive compounds and medications. Herein, the first highly chemoselective tandem C(sp3)–H arylation/[1,2]-Wittig rearrangement of pyridylmethyl ethers is presented. The efficient and operationally simple protocols enable generation of either arylation products or tandem arylation/[1,2]-Wittig rearrangement products with remarkable selectivity and good to excellent yields (60–99%). Choice of base, solvent, and reaction temperature play a pivotal role in tuning the reactivity of intermediates and controlling the relative rates of competing processes. The novel arylation step is catalyzed by a Pd(OAc)2/NIXANTPHOS-based system via a deprotonative cross-coupling process. The method provides rapid access to skeletally diverse aryl(pyridyl)methanol core structures, which are central components of several medications. 相似文献
55.
56.
Anomalous nonlinear effects in the alkylation of substituted benzaldehydes with diethylzinc using aminoalcohol catalysts are rationalized in terms of a simple extension of the Noyori model to allow for nonthermodynamically controlled partitioning of the catalyst between monomeric and dimeric species. This work highlights the fact that catalyst composition in such systems may be influenced by substrate properties. 相似文献
57.
58.
59.
Summary The main features of the spectral characteristics of the spontaneously emitted Ĉerenkov light in circular and rectangular
wave guides filled with dielectric are discussed. The characteristics of the radiation emitted by an electron beam moving
near and parallel to the surface of a dielectric slab are also analysed. Finally, the relevance of these results to a possible
FEL-Ĉerenkov operation is briefly discussed.
Riassunto In questo lavoro si discutono le caratteristiche dello spettro della radiazione Ĉerenkov, emessa in guide d'onde circolari e rettangolari riempite con dielettrico. Si analizzano inoltre le proprietà della radiazione emessa da un fascio di elettroni in moto in prossimità e parallelamente alla superficie di una ?slab? di dielettrico. Si discute, infine, brevemente, l'importanza di questi risultati per la realizzazione di un possibile FEL-Ĉerenkov.
Резюме Обсуждаются основиые особенности спектральных характеристик спонтанного черенковского излучения в круговых и прямоугольных волноводах, заполненных диэлектриком. Также анализируются характеристики излучения, испущенного электронным пучком, движущимся вблизи и пораллелйно поверхности диэлектрической пластинки. В заключение, вкратце обсуждется применимость полученных результатов в возможных FEL-черенковских приборах.相似文献
60.
A hierarchy of disjoint ?ech carriers properties is introduced; and each is shown to be characteristic of ANR's whose products with 2-cells are Hilbert cube manifolds. 相似文献