全文获取类型
收费全文 | 1677篇 |
免费 | 64篇 |
国内免费 | 3篇 |
专业分类
化学 | 1474篇 |
晶体学 | 7篇 |
力学 | 8篇 |
数学 | 115篇 |
物理学 | 140篇 |
出版年
2024年 | 4篇 |
2023年 | 12篇 |
2022年 | 112篇 |
2021年 | 78篇 |
2020年 | 47篇 |
2019年 | 49篇 |
2018年 | 35篇 |
2017年 | 43篇 |
2016年 | 74篇 |
2015年 | 66篇 |
2014年 | 64篇 |
2013年 | 105篇 |
2012年 | 96篇 |
2011年 | 132篇 |
2010年 | 84篇 |
2009年 | 72篇 |
2008年 | 109篇 |
2007年 | 87篇 |
2006年 | 61篇 |
2005年 | 80篇 |
2004年 | 60篇 |
2003年 | 40篇 |
2002年 | 32篇 |
2001年 | 15篇 |
2000年 | 18篇 |
1999年 | 5篇 |
1998年 | 11篇 |
1997年 | 14篇 |
1996年 | 12篇 |
1995年 | 14篇 |
1994年 | 8篇 |
1993年 | 9篇 |
1992年 | 6篇 |
1991年 | 5篇 |
1990年 | 6篇 |
1989年 | 9篇 |
1988年 | 10篇 |
1987年 | 6篇 |
1986年 | 4篇 |
1985年 | 4篇 |
1984年 | 3篇 |
1982年 | 2篇 |
1981年 | 3篇 |
1980年 | 6篇 |
1979年 | 8篇 |
1978年 | 6篇 |
1977年 | 4篇 |
1976年 | 3篇 |
1975年 | 3篇 |
1973年 | 3篇 |
排序方式: 共有1744条查询结果,搜索用时 15 毫秒
71.
Sara Janowska Dmytro Khylyuk Anna Bielawska Anna Szymanowska Agnieszka Gornowicz Krzysztof Bielawski Jarosaw Noworl Sawomir Mandziuk Monika Wujec 《Molecules (Basel, Switzerland)》2022,27(6)
We designed and synthesized the 1,3,4-thiadiazole derivatives differing in the structure of the substituents in C2 and C5 positions. The cytotoxic activity of the obtained compounds was then determined in biological studies using MCF-7 and MDA-MB-231 breast cancer cells and normal cell line (fibroblasts). The results showed that in both breast cancer cell lines, the strongest anti-proliferative activity was exerted by 2-(2-trifluorometylophenylamino)-5-(3-methoxyphenyl)-1,3,4-thiadiazole. The IC50 values of this compound against MCF-7 and MDA-MB-231 breast cancer cells were 49.6 µM and 53.4 µM, respectively. Importantly, all new compounds had weaker cytotoxic activity on normal cell line than on breast cancer cell lines. In silico studies demonstrated a possible multitarget mode of action for the synthesized compounds. The most likely mechanism of action for the new compounds is connected with the activities of Caspase 3 and Caspase 8 and activation of BAX proteins. 相似文献
72.
R. K. Sinha A. Dhal P. Agarwal S. Kumar Monika B. B. Singh R. Kumar P. Bringel A. Neusser R. Kumar K. S. Golda R. P. Singh S. Muralithar N. Madhavan J. J. Das K. S. Thind A. K. Sinha I. M. Govil R. K. Bhowmik J. B. Gupta P. K. Joshi A. K. Jain S. C. Pancholi L. Chaturvedi 《The European Physical Journal A - Hadrons and Nuclei》2006,28(3):277-281
High-spin states in 79Rb were populated in the reaction
at E(beam) = 60 MeV. The lifetimes of the excited states of the
positive-parity yrast band and of the
negative-parity band in 79Rb were measured by the Doppler Shift Attenuation Method. The deduced transition quadrupole moments Qt are found to have a decreasing trend with rotational frequency for both the bands, consistent with those found experimentally
in neighbouring nuclei.
An erratum to this article is available at . 相似文献
73.
Shadow effects in spiral phase contrast microscopy 总被引:3,自引:0,他引:3
Recently it has been demonstrated that spatial filtering of images in microscopy with a spiral phase element in a Fourier plane of the optical path results in a strong edge enhancement of object structures. In principle the operation is isotropic, i.e., all phase edges of a sample object are highlighted simultaneously, independent of their local direction. However, here we demonstrate that the symmetry can be broken intentionally by controlling the phase of the central area of a spiral phase hologram, which is displayed at a computer controlled spatial light modulator. This produces an apparent shadow effect which can be rotated at video rate. The resulting relieflike impression of the sample topography with a longitudinal resolution in the subwavelength regime is demonstrated by imaging a standard low contrast test sample consisting of a human cheek cell. 相似文献
74.
Monika Sinha Manjari Bagchi Jishnu Dey Mira Dey Subharthi Ray Siddhartha Bhowmick 《Physics letters. [Part B]》2004,590(3-4):120-125
Strange stars (ReSS) calculated from a realistic equation of state (EOS), that incorporate chiral symmetry restoration as well as deconfinement at high density [Phys. Lett. B 438 (1998) 123; Phys. Lett. B 447 (1999) 352, Addendum; Phys. Lett. B 467 (1999) 303, Erratum; Indian J. Phys. B 73 (1999) 377] show compact objects in the mass radius curve. We compare our calculations of incompressibility for this EOS with that of nuclear matter. One of the nuclear matter EOS has a continuous transition to ud-matter at about five times normal density. Another nuclear matter EOS incorporates density dependent coupling constants. From a look at the consequent velocity of sound, it is found that the transition to ud-matter seems necessary. 相似文献
75.
76.
Monika Kořenková Dr. Ing. Martin Hejda Prof. Milan Erben Dr. Ing. Robert Jirásko Prof. Dr. Roman Jambor Prof. Aleš Růžička Dr. Elena Rychagova Prof. Sergey Ketkov Prof. Libor Dostál 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(56):12884-12888
The reaction of N,C,N-chelated stibinidene ArSb ( 1 ) (Ar=C6H3-2,6-(CH=NtBu)2) with selected N-alkyl/aryl-maleimides RN(C(O)CH)2 (R=Me, tBu, Ph) gave the addition products with bridged bicyclic [2.2.1] structure containing an antimony atom at the bridgehead position, fused with a 6-membered benzene and a 5-membered N-alkyl/aryl-pyrrolidine ring. These compounds were completely characterized. More importantly, additional studies showed that these reactions are reversible in solution, thereby representing an unprecedented reversible activation of a C=C bond by an antimony(I) compound. 相似文献
77.
Lana K. Hiscock Brooke M. Raycraft Monika Wałęsa-Chorab Coralie Cambe Alexandre Malinge Prof. Dr. W. G. Skene Hi Taing Prof. Dr. S. Holger Eichhorn Prof. Dr. Louise N. Dawe Prof. Dr. Kenneth E. Maly 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(4):1018-1028
A series of new tetrakis(dialkoxyphenyl) dicyanotetraoxapentacene derivatives ( 1 a – c ) were prepared by reaction of the appropriate terphenyl diols with tetrafluoroterephthalonitrile in good yields. Compounds 1 b and 1 c , which bear hexyloxy and decyloxy side chains, exhibited columnar hexagonal mesophases, as shown by polarized optical microscopy, variable-temperature powder X-ray diffraction, and differential scanning calorimetry. Single-crystal X-ray diffraction of methoxy-substituted 1 a revealed that the dicyanotetraoxapentacene core is highly planar, consistent with the notion that these molecules are able to stack in columnar mesophases. A detailed photophysical characterization showed that these compounds exhibit aggregation-induced emission in solution, emission in nonpolar solvents, weak emission in polar solvents, and strong emission in the solid state both as powder and in thin films. These observations are consistent with a weakly emissive charge-transfer state in polar solvents and a more highly emissive locally excited state in nonpolar solvents. 相似文献
78.
Journal of Thermal Analysis and Calorimetry - In the present investigation, gene expression programming (GEP) is used to predict thermal conductivity of nanofluids consisting of $$hbox {Al}_2hbox... 相似文献
79.
80.
Daniel Josef Bell Monika Wiese Ariel Augusto Schönberger Matthias Wessling 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(37):16181-16187
Metal–organic frameworks (MOFs) are suitable enzyme immobilization matrices. Reported here is the in situ biomineralization of glucose oxidase (GOD) into MOF crystals (ZIF-8) by interfacial crystallization. This method is effective for the selective coating of porous polyethersulfone microfiltration hollow fibers on the shell side in a straightforward one-step process. MOF layers with a thickness of 8 μm were synthesized, and fluorescence microscopy and a colorimetric protein assay revealed the successful inclusion of GOD into the ZIF-8 layer with an enzyme concentration of 29±3 μg cm−2. Enzymatic activity tests revealed that 50 % of the enzyme activity is preserved. Continuous enzymatic reactions, by the permeation of β-d -glucose through the GOD@ZIF-8 membranes, showed a 50 % increased activity compared to batch experiments, emphasizing the importance of the convective transport of educts and products to and from the enzymatic active centers. 相似文献