全文获取类型
收费全文 | 2534篇 |
免费 | 146篇 |
出版年
2023年 | 16篇 |
2022年 | 14篇 |
2021年 | 45篇 |
2020年 | 34篇 |
2019年 | 54篇 |
2018年 | 88篇 |
2017年 | 89篇 |
2016年 | 123篇 |
2015年 | 146篇 |
2014年 | 133篇 |
2013年 | 199篇 |
2012年 | 209篇 |
2011年 | 215篇 |
2010年 | 143篇 |
2009年 | 100篇 |
2008年 | 152篇 |
2007年 | 143篇 |
2006年 | 160篇 |
2005年 | 125篇 |
2004年 | 102篇 |
2003年 | 92篇 |
2002年 | 90篇 |
2001年 | 15篇 |
2000年 | 8篇 |
1999年 | 12篇 |
1998年 | 15篇 |
1997年 | 15篇 |
1996年 | 8篇 |
1995年 | 8篇 |
1994年 | 10篇 |
1993年 | 12篇 |
1992年 | 6篇 |
1991年 | 8篇 |
1990年 | 10篇 |
1989年 | 5篇 |
1988年 | 4篇 |
1987年 | 4篇 |
1986年 | 3篇 |
1985年 | 4篇 |
1984年 | 7篇 |
1983年 | 7篇 |
1982年 | 5篇 |
1981年 | 10篇 |
1980年 | 7篇 |
1979年 | 8篇 |
1975年 | 3篇 |
1974年 | 3篇 |
1973年 | 2篇 |
1969年 | 2篇 |
1960年 | 1篇 |
排序方式: 共有2680条查询结果,搜索用时 31 毫秒
1.
2.
3.
Gro O. Nygaard Elisabeth G. Celius Sigrid A. de Rodez Benavent Piotr Sowa Marte W. Gustavsen Anders M. Fjell Nils I. Landr? Kristine B. Walhovd Hanne F. Harbo 《PloS one》2015,10(8)
New treatment options may make “no evidence of disease activity” (NEDA: no relapses or disability progression and no new/enlarging MRI lesions, as opposed to “evidence of disease activity” (EDA) with at least one of the former), an achievable goal in relapsing-remitting multiple sclerosis (RRMS). The objective of the present study was to determine whether early RRMS patients with EDA at one-year follow-up had different disability, cognition, treatment and gray matter (GM) atrophy rates from NEDA patients and healthy controls (HC). RRMS patients (mean age 34 years, mean disease duration 2.2 years) were examined at baseline and one-year follow-up with neurological (n = 72), neuropsychological (n = 56) and structural MRI (n = 57) examinations. Matched HC (n = 61) were retested after three years. EDA was found in 46% of RRMS patients at follow-up. EDA patients used more first line and less second line disease modifying treatment than NEDA (p = 0.004). While the patients groups had similar disability levels at baseline, they differed in disability at follow-up (p = 0.010); EDA patients progressed (EDSS: 1.8–2.2, p = 0.010), while NEDA patients improved (EDSS: 2.0–1.7, p<0.001). Cognitive function was stable in both patient groups. Subcortical GM atrophy rates were higher in EDA patients than HC (p<0.001). These results support the relevance of NEDA as outcome in RRMS and indicate that pathological neurodegeneration in RRMS mainly occur in patients with evidence of disease activity. 相似文献
4.
5.
6.
The influence of hypomagnesemia on erythrocyte antioxidant enzyme defence system in mice 总被引:2,自引:1,他引:1
Andrzej Kuzniar Przemyslaw Mitura Piotr Kurys Stanislawa Szymonik-Lesiuk Boleslaw Florianczyk Marta Stryjecka-Zimmer 《Biometals》2003,16(2):349-357
The effect of magnesium deficiency on antioxidant defence system was studied in RBC of mice suffering from hypomagnesemia. The animals were kept for 8, 15 and 22 days on magnesium-deficient diet with consequent reduction of magnesium level in plasma by 38% at the first 8 days and by 64% after 22 days of experiment. The activities of the most important antioxidant enzymes, catalase, glutathione peroxidase, superoxide dismutase, glutathione reductase, glutahione S-transferase were assayed in hemolysates. The level of reduced glutathione in erythrocytes was measured as well. Apart from catalase, the activities of antioxidant enzymes were decreasing. The activity of superoxide dismutase decreased gradually during the experiment and on the 15th and 22nd day of experiment was significantly (P<0,05) lowered by 30 and 32% respectively. The catalase activity was increased on each point of the experiment with the peak value up to 149% on 15th day, and by 32% on 22nd day. Glutathione peroxidase activity was insignificantly reduced. The reduction of Glutatione reductase and Glutathione S-transferase activities by 24 and 21%, respectively, were observed after 8 days of the experiment with a further downward tendency. The reduced glutathione was significantly depleted after 8 days by 33% and was kept on that level in the course of the study. These findings support previous reports on the hypomagnesemia – induced alteration in endogenous enzyme antioxidant defences and glutathione redox cycle of mice. 相似文献
7.
Piotr J Durka 《Biomedical engineering online》2003,2(1):1
This paper presents a summary of time-frequency analysis of the electrical activity of the brain (EEG). It covers in details
two major steps: introduction of wavelets and adaptive approximations. Presented studies include time-frequency solutions
to several standard research and clinical problems, encountered in analysis of evoked potentials, sleep EEG, epileptic activities,
ERD/ERS and pharmaco-EEG. Based upon these results we conclude that the matching pursuit algorithm provides a unified parametrization
of EEG, applicable in a variety of experimental and clinical setups. This conclusion is followed by a brief discussion of
the current state of the mathematical and algorithmical aspects of adaptive time-frequency approximations of signals. 相似文献
8.
Piotr Cysewski 《Journal of molecular modeling》2010,16(11):1721-1729
Non-additivity of base-base interactions in all ten possible model dinucleotide steps were analyzed on MP2/aug-cc-pvDZ quantum
chemistry level. Conformations of four nucleobases exactly matched to ones occurring in B-DNA crystals. In most of thw 162
analyzed tetramers both three- and four-body contributions are negligible except for d(GpG) steps. However, in these dinucleotides
both contributions are always of opposite signs and in all cases the sum of all non-additive part of intermolecular interactions
do not exceed 2.6 kcal mol-1. This stands for less than 5% of the overall binding energy of dinucleotide steps. Also replacements of guanine with 8-oxoguanine
in d(GpG) systems introduces non-additivity of the same magnitude as for canonical dinucleotides. It is observed linear relationships
between values of total binding energy obtained in the tetramer basis set and estimated energy exclusively in dimers basis
sets with assumption of pairwise additivities. For all analyzed dinucleotides steps there are also linear correlations between
amount of non-additive contributions and magnitude of pairs interactions. Based on differences in electrostatic contribution
to the total binding energy of four nucleobases and polarity of dinucleotide steps three distinct classes of dinucleotide
steps were identified. 相似文献
9.
The paper presents a computationally effective method for fault detection. A system’s responses are measured under healthy and ill conditions. These signals are used to calculate so-called signature functions that create a signal space. The current system’s response is projected into this space. The signal location in this space easily allows to determine the fault. No classifier such as a neural network, hidden Markov models, etc. is required. The advantage of this proposed method is its efficiency, as computing projections amount to calculating dot products. Therefore, this method is suitable for real-time embedded systems due to its simplicity and undemanding processing capabilities which permit the use of low-cost hardware and allow rapid implementation. The approach performs well for systems that can be considered linear and stationary. The communication presents an application, whereby an industrial process of moulding is supervised. The machine is composed of forms (dies) whose alignment must be precisely set and maintained during the work. Typically, the process is stopped periodically to manually control the alignment. The applied algorithm allows on-line monitoring of the device by analysing the acceleration signal from a sensor mounted on a die. This enables to detect failures at an early stage thus prolonging the machine’s life. 相似文献
10.
Piotr Politański Elźbieta Rajkowska Marcin Brodecki Andrzej Bednarek Marek Zmyślony 《Bioelectromagnetics》2013,34(4):333-336
The aim of this study was to investigate the effect of static magnetic fields (SMF) on reactive oxygen species induced by X‐ray radiation. The experiments were performed on lymphocytes from male albino Wistar rats. After exposure to 3 Gy X‐ray radiation (with a dose rate of 560 mGy/min) the measurement of intracellular reactive oxygen species in lymphocytes, using a fluorescent probe, was done before exposure to the SMF, and after 15 min, 1 and 2 h of exposure to the SMF or a corresponding incubation time. For SMF exposure, 0 mT (50 µT magnetic field induction opposite to the geomagnetic field) and 5 mT fields were chosen. The trend of SMF effects for 0 mT was always opposite that of 5 mT. The first one decreased the rate of fluorescence change, while the latter one increased it. Bioelectromagnetics 34:333–336, 2013. © 2012 Wiley Periodicals, Inc. 相似文献