全文获取类型
收费全文 | 730篇 |
免费 | 20篇 |
国内免费 | 4篇 |
专业分类
化学 | 451篇 |
晶体学 | 3篇 |
力学 | 18篇 |
数学 | 181篇 |
物理学 | 101篇 |
出版年
2023年 | 8篇 |
2022年 | 9篇 |
2021年 | 30篇 |
2020年 | 9篇 |
2019年 | 17篇 |
2018年 | 8篇 |
2017年 | 6篇 |
2016年 | 24篇 |
2015年 | 31篇 |
2014年 | 23篇 |
2013年 | 53篇 |
2012年 | 51篇 |
2011年 | 54篇 |
2010年 | 44篇 |
2009年 | 36篇 |
2008年 | 43篇 |
2007年 | 36篇 |
2006年 | 27篇 |
2005年 | 26篇 |
2004年 | 20篇 |
2003年 | 19篇 |
2002年 | 20篇 |
2001年 | 16篇 |
2000年 | 6篇 |
1999年 | 6篇 |
1998年 | 5篇 |
1996年 | 7篇 |
1995年 | 7篇 |
1994年 | 16篇 |
1993年 | 2篇 |
1992年 | 6篇 |
1991年 | 5篇 |
1990年 | 7篇 |
1989年 | 4篇 |
1988年 | 8篇 |
1987年 | 6篇 |
1986年 | 2篇 |
1985年 | 3篇 |
1984年 | 7篇 |
1982年 | 5篇 |
1981年 | 4篇 |
1980年 | 4篇 |
1979年 | 3篇 |
1978年 | 5篇 |
1977年 | 4篇 |
1976年 | 4篇 |
1973年 | 3篇 |
1968年 | 2篇 |
1966年 | 2篇 |
1954年 | 2篇 |
排序方式: 共有754条查询结果,搜索用时 15 毫秒
91.
S. Giordano P. L. Palla L. Colombo 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,66(1):29-35
We prove a generic theorem stating the equivalence
between a graded dielectric ellipsoid (with gradation along a family of
internal confocal ellipsoids) and an anisotropic homogeneous ellipsoid. We then describe a procedure to obtain the three principal
permittivities of the effective ellipsoid for any given dielectric gradation profile. Finally, we apply a multiscale approach
to homogenize dispersions of ellipsoidal graded particles. 相似文献
92.
Alessandro Colombo 《Physica D: Nonlinear Phenomena》2008,237(22):2900-2912
Piecewise smooth systems are known to present a richer set of bifurcations than their smooth counterparts. An interesting family of bifurcations that is present in this type of systems are the so called boundary intersection crossing bifurcations, that take place when a periodic orbit crosses the intersection between two or more discontinuity boundaries. Such bifurcations have been observed in many different models, and have been studied in a number of papers over the past few years. Nonetheless, the particular case in which sliding solutions (as defined by Filippov) are involved, has been left out in previous analyses. This paper addresses this particular case, carrying out a complete analysis and deriving the discontinuity mappings that can be used to characterise such bifurcations. Then, in the second part of the paper, the results are applied to the study of a model of a common electronic device, showing how the mappings can be used systematically to determine the dynamics around the bifurcation. 相似文献
93.
Molina FD Bertollo EM Assis CM Falleiros LR Campos SG Maniglia JV Taboga SR 《Micron (Oxford, England : 1993)》2008,39(7):910-914
Squamous cell carcinoma of the tongue is one of the most common head and neck cancer. Treatment in the early stages is still controversial. This study aims to correlate the apoptosis rate of primary tongue cancer with cervical node metastasis, found in the histopathological studies of specimens obtained from neck dissections or during clinical follow-up. Twenty patients, 65% males, mean age 64.5 years, without clinical evidence of cervical metastasis was included. Eighty-five percent were smokers and 40% were alcohol abusers. Mann-Whitney test was used for statistical analysis (p=0.05). Five patients with clinically occult cervical metastases had metastasis in the histopathological specimens (25%) occult metastasis. The mean apoptosis rate in patients without cervical metastasis was 9.43%. Twenty-five percent of the patients had occult cervical metastasis. High apoptosis rate in tongue cancer, even in the absence of palpable neck nodes, correlates with the presence of occult metastasis. 相似文献
94.
We consider the problem of sending a message from a sender to a receiver through an unreliable network by specifying in a protocol what each vertex is supposed to do if it receives the message from one of its neighbors. A protocol for routing a message in such a graph is finite if it never floods with an infinite number of copies of the message. The expected reliability of a given protocol is the probability that a message sent from reaches when the edges of the network fail independently with probability .We discuss, for given networks, the properties of finite protocols with maximum expected reliability in the case when is close to 0 or 1, and we describe networks for which no one protocol is optimal for all values of . In general, finding an optimal protocol for a given network and fixed probability is challenging and many open problems remain. 相似文献
95.
96.
97.
Senka Djakovi Ljubica Glava‐Obrovac Jasmina Lapi Silvija Mara
i Juraj Kirchofer Marija Kneevi Marijana Juki Silvana Rai‐Mali 《应用有机金属化学》2021,35(1)
Mono‐ ( 3a – 3e and 4a – 4e ) and bis‐ferrocene ( 5a – 5e and 6a – 6e ) conjugated 5‐substituted uracil derivatives that are bridged by 1,2,3‐triazole linker were synthesized. The impact of ferrocene unit and spacer between ferrocene and triazole on radical scavenging potency was observed. Bis‐ferrocenyl uracil derivatives exhibited better antiproliferative activities than their mono‐ferrocenyl analogs. Bis‐ferrocenyl methyl‐ ( 5b ) and halogen‐substituted ( 5e , 6c , and 6d ) uracil derivatives showed pronounced and selective cytostatic activities on colon adenocarcinoma (CaCo‐2) and Burkitt lymphoma (Raji) cells, with higher potency and selectivity than the reference drug 5‐fluorouracil. Generation of reactive oxygen species (ROS) in CaCo‐2 and Raji cells when treated with compounds 5b , 5e , and 6d was observed. Bis‐ferrocenyl 5‐chlorouracil 6c induced significant disruption in mitochondrial membrane potential that is accompanied by activation of apoptosis in CaCo‐2, Raji, and acute lymphoblastic leukemia (CCRF‐CEM) cells, while 6d caused mitochondrial dysfunction and apoptosis induction in CaCo‐2 and Raji cells. Potent antiproliferative activity of 6c and 6d could be associated with mitochondrial membrane potential disruption accompanied by apoptosis induction. Our findings highlighted 6c and 6d with potent and selective antiproliferative activity on CaCo‐2, Raji, and CCRF‐CEM cells that may be associated with targeting cancer cell mitochondria, as a molecular target. 相似文献
98.
Lopez Kenneth Pinheiro Silvana Zamora William J. 《Journal of computer-aided molecular design》2021,35(8):923-931
Journal of Computer-Aided Molecular Design - A multiple linear regression model called MLR-3 is used for predicting the experimental n-octanol/water partition coefficient (log PN) of 22... 相似文献
99.
Silvana Alborés Paola Mora María José Bustamante María Pía Cerdeiras Laura Franco Fraguas 《Applied biochemistry and biotechnology》2014,172(4):2081-2090
A lectin was isolated from fruiting bodies of the mushroom Gymnopilus spectabilis (GSL) by ionic exchange chromatography. The lectin agglutinates mouse red cells exhibiting broad specificity towards several monosaccharides including the N-acetylneuraminic acid. Agglutination was also inhibited by the glycoproteins: fetuin, lactoferrin, and recombinant erythropoietin. GSL is a glycoprotein possessing 16 % of carbohydrates; the SDS-PAGE showed two bands with molecular mass of 52.1 and 64.4 kDa. Isoelectric focusing displayed microheterogeneity, with two bands at pIs 5.1 and 5.3. The lectin was stable between pH 2 and pH 8 while at pH 10, the agglutination decayed to 50 % of initial activity. Incubation at 40 and 80 °C led to 50 and 100 % loss in activity of the lectin, respectively. Synthesized GSL-Sepharose interacts with serum pregnant mare gonadotropin, and at least two subpopulations of this glycoprotein were separated. There was no interaction between transferrin and soluble GSL while a partial recognition was achieved with GSL-Sepharose. The terminal sialic acid seems to play an active role in modifying the interaction with GSL, depending if the lectin is in a soluble or immobilized form. The purified lectin inhibited in vitro the growth of Staphylococcus aureus and Aspergillus niger. 相似文献
100.
Research on Chemical Intermediates - l-arginine is often covalently linked to vectors for gene or drug delivery as a means of increasing their transfection activity and reducing toxicity. This... 相似文献