全文获取类型
收费全文 | 8491篇 |
免费 | 506篇 |
国内免费 | 20篇 |
出版年
2024年 | 20篇 |
2023年 | 108篇 |
2022年 | 300篇 |
2021年 | 434篇 |
2020年 | 399篇 |
2019年 | 593篇 |
2018年 | 471篇 |
2017年 | 329篇 |
2016年 | 433篇 |
2015年 | 464篇 |
2014年 | 583篇 |
2013年 | 743篇 |
2012年 | 711篇 |
2011年 | 681篇 |
2010年 | 374篇 |
2009年 | 309篇 |
2008年 | 347篇 |
2007年 | 357篇 |
2006年 | 302篇 |
2005年 | 244篇 |
2004年 | 190篇 |
2003年 | 155篇 |
2002年 | 131篇 |
2001年 | 26篇 |
2000年 | 18篇 |
1999年 | 26篇 |
1998年 | 23篇 |
1997年 | 24篇 |
1996年 | 16篇 |
1995年 | 10篇 |
1994年 | 9篇 |
1993年 | 13篇 |
1992年 | 9篇 |
1991年 | 16篇 |
1990年 | 5篇 |
1989年 | 11篇 |
1988年 | 6篇 |
1987年 | 14篇 |
1986年 | 16篇 |
1985年 | 13篇 |
1984年 | 13篇 |
1983年 | 8篇 |
1982年 | 6篇 |
1981年 | 6篇 |
1980年 | 7篇 |
1979年 | 4篇 |
1976年 | 4篇 |
1975年 | 6篇 |
1974年 | 8篇 |
1973年 | 4篇 |
排序方式: 共有9017条查询结果,搜索用时 15 毫秒
61.
SeyyedReza SadatEbrahimi Hassan Amini Reza Rahbarghazi Paria Habibollahi Shahrouz Ghaderi Hadi Rajabi Aysa Rezabakhsh 《Journal of cellular and molecular medicine》2022,26(11):3120
Recently, cytokines belonging to C1q/tumour necrosis factor‐related proteins (CTRPs) superfamily have attracted increasing attention due to multiple metabolic functions and desirable anti‐inflammatory effects. These various molecular effectors exhibit key roles upon the onset of cardiovascular diseases, making them novel adipo/cardiokines. This review article aimed to highlight recent findings correlated with therapeutic effects and additional mechanisms specific to the CTRP9, particularly in cardiac ischaemia/reperfusion injury (IRI). Besides, the network of the CTPR9 signalling pathway and its possible relationship with IRI were discussed. Together, the discovery of all involved underlying mechanisms could shed light to alleviate the pathological sequelae after the occurrence of IRI. 相似文献
62.
Temporal variation of Bistorta vivipara‐associated ectomycorrhizal fungal communities in the High Arctic 下载免费PDF全文
Sunil Mundra Mohammad Bahram Leho Tedersoo Håvard Kauserud Rune Halvorsen Pernille Bronken Eidesen 《Molecular ecology》2015,24(24):6289-6302
Ectomycorrhizal (ECM) fungi are important for efficient nutrient uptake of several widespread arctic plant species. Knowledge of temporal variation of ECM fungi, and the relationship of these patterns to environmental variables, is essential to understand energy and nutrient cycling in Arctic ecosystems. We sampled roots of Bistorta vivipara ten times over two years; three times during the growing‐season (June, July and September) and twice during winter (November and April) of both years. We found 668 ECM OTUs belonging to 25 different ECM lineages, whereof 157 OTUs persisted throughout all sampling time‐points. Overall, ECM fungal richness peaked in winter and species belonging to Cortinarius, Serendipita and Sebacina were more frequent in winter than during summer. Structure of ECM fungal communities was primarily affected by spatial factors. However, after accounting for spatial effects, significant seasonal variation was evident revealing correspondence with seasonal changes in environmental conditions. We demonstrate that arctic ECM richness and community structure differ between summer (growing‐season) and winter, possibly due to reduced activity of the core community, and addition of fungi adapted for winter conditions forming a winter‐active fungal community. Significant month × year interactions were observed both for fungal richness and community composition, indicating unpredictable between‐year variation. Our study indicates that addressing seasonal changes requires replication over several years. 相似文献
63.
Biofabrication with chitosan 总被引:14,自引:0,他引:14
Yi H Wu LQ Bentley WE Ghodssi R Rubloff GW Culver JN Payne GF 《Biomacromolecules》2005,6(6):2881-2894
The traditional motivation for integrating biological components into microfabricated devices has been to create biosensors that meld the molecular recognition capabilities of biology with the signal processing capabilities of electronic devices. However, a different motivation is emerging; biological components are being explored to radically change how fabrication is achieved at the micro- and nanoscales. Here we review biofabrication, the use of biological materials for fabrication, and focus on three specific biofabrication approaches: directed assembly, where localized external stimuli are employed to guide assembly; enzymatic assembly, where selective biocatalysts are enlisted to build macromolecular structure; and self-assembly, where information internal to the biological material guides its own assembly. Also reviewed are recent results with the aminopolysaccharide chitosan, a material that offers a combination of properties uniquely suited for biofabrication. In particular, chitosan can be directed to assemble in response to locally applied electrical signals, and the chitosan backbone provides sites that can be employed for the assembly of proteins, nucleic acids, and virus particles. 相似文献
64.
Zahra Akbari jonous Javad Shabani Shayeh Fatemeh Yazdian Amir Yadegari Mohadeseh Hashemi Meisam Omidi 《Engineering in Life Science》2019,19(3):206-216
In this paper, a most sensitive electrochemical biosensor for detection of prostate‐specific antigen (PSA) was designed. To reach the goal, a sandwich type electrode composed of reduced graphene oxide/ gold nanoparticles (GO/AuNPs), Anti‐Total PSA monoclonal antibody, and anti‐Free PSA antibody was assembled. The functionalized materials were thoroughly characterized by atomic force microscope spectroscopy, transmission electron microscopy, and X‐ray diffraction techniques. The electrochemical properties of each of the modification step were evaluated by cyclic voltammetry and electrochemical impedance spectroscopy. The results presented that the proposed biosensor possesses high sensitivity toward total and free PSA. Furthermore, the fabricated biosensor revealed an excellent selectivity for PSA in comparison to the other tumor markers such as BHCG, Alb, CEA, CA125, and CA19‐9. The limit of detection for the proposed electrochemical biosensor was estimated to be around 0.2 and 0.07 ng/mL for total and free PSA antigen, respectively. 相似文献
65.
Mohammad Reza Afarinesh Vahid Sheibani Somaye Arabzadeh Ali Shamsizadeh 《Addiction biology》2008,13(1):31-39
Chronic exposure to morphine can impair performance in tasks which need sensory processing. Using single unit recordings we investigate the effect of chronic morphine exposure on the firing properties of neurons in layers IV and V of the whisker-related area of rat primary somatosensory cortex. In urethane-anesthetized animals, neuronal activity was recorded in response to principal and adjacent whisker deflections either stimulated independently or in a conditioning test paradigm. A condition test ratio (CTR) was calculated for assessing the inhibitory receptive field. In layer IV, chronic morphine treatment did not change the spontaneous discharge activity. On responses to principal and adjacent whisker deflections did not show any significant changes following chronic morphine exposure. The magnitude Off responses to adjacent whisker deflection decreased while its response latency increased. In addition, there was a significant increase in the latency of Off responses to principal whisker deflection. CTR did not change significantly following morphine exposure. Layer V neurons, on the other hand, did not show any significant changes in their spontaneous activity or their evoked responses following morphine exposure. Our results suggest that chronic morphine exposure has a subtle modulatory effect on response properties of neurons in barrel cortex. 相似文献
66.
Narjes Soltani Ali Roohbakhsh Mohammad Allahtavakoli Elham Salari Vahid Sheibani Iman Fatemi 《Somatosensory & motor research》2013,30(2):131-138
AbstractCholecystokinin (CCK) is one of the most studied neuropeptides in the brain. In this study, we investigated the effects of CCK-8s and LY225910 (CCK2 receptor antagonist) on properties of neuronal response to natural stimuli (whisker deflection) in deep layers of rat barrel cortex. This study was done on 20 male Wistar rats, weighing 230–260?g. CCK-8s (300?nmol/rat) and LY225910 (1?µmol/rat) were administered intracerebroventricularly (ICV). Neuronal responses to deflection of principal (PW) and adjacent (AW) whiskers were recorded in the barrel cortex using tungsten microelectrodes. Computer controlled mechanical displacement was used to deflect whiskers individually or in combination at 30?ms inter-stimulus intervals. ON and OFF responses for PW and AW deflections were measured. A condition-test ratio (CTR) was computed to quantify neuronal responses to whisker interaction. ICV administration of CCK-8s and LY225910 had heterogeneous effects on neuronal spontaneous activity, ON and OFF responses to PW and/or AW deflections, and CTR for both ON and OFF responses. The results of this study demonstrated that CCK-8s can modulate neuronal response properties in deep layers of rat barrel cortex probably via CCK2 receptors. 相似文献
67.
Quaiser Saquib Mohammad Faisal Sabiha Mahmood Ansari Rizwan Wahab 《Saudi Journal of Biological Sciences》2019,26(7):1411-1417
Herein, we studied phorate for its toxicological effects in human lymphocytes. Phorate treatment for 3 h has induced significant increase in the lymphocytic DNA damage. Compared to control, comet data from highest concentration of phorate (1000 µM) showed 8.03-fold increase in the Olive tail moment (OTM). Cytokinesis blocked micronucleus (CBMN) assay revealed 6.4-fold increase in binucleated micronucleated (BNMN) cells following the exposure with phorate (200 µM) for 24 h. The nuclear division index (NDI) in phorate (200 µM) treated cells reduced to 1.8 vis-à-vis control cells showed NDI of 1.94. Comparative to untreated control, 60.43% greater DCF fluorescence was quantitated in lymphocytes treated with phorate (500 µM), affirming reactive oxygen species (ROS) generation and oxidative stress. Flow cytometric data of phorate (200 µM) treated lymphocytes showed 81.77% decline in the fluorescence of rhodamine 123 (Rh123) dye, confirming the perturbation of mitochondrial membrane potential (ΔΨm). Calf thymus DNA (ct-DNA) treated with phorate (1000 µM) exhibited 2.3-fold higher 8-Hydroxy-2′-deoxyguanosine (8-oxodG) DNA adduct formation, signified the oxidative DNA damage. The alkaline unwinding assay revealed 4.0 and 6.5 ct-DNA strand breaks when treated to phorate and phorate-Cu (II) complex. Overall, the data unequivocally suggests the cyto- and genotoxic potential of phorate in human lymphocytes, which may induce comparable toxicological consequences in persons occupationally or non-occupationally exposed to insecticide phorate. 相似文献
68.
Quiberoni A Biswas I El Karoui M Rezaïki L Tailliez P Gruss A 《Journal of bacteriology》2001,183(13):4071-4078
In bacteria, double-strand DNA break (DSB) repair involves an exonuclease/helicase (exo/hel) and a short regulatory DNA sequence (Chi) that attenuates exonuclease activity and stimulates DNA repair. Despite their key role in cell survival, these DSB repair components show surprisingly little conservation. The best-studied exo/hel, RecBCD of Escherichia coli, is composed of three subunits. In contrast, RexAB of Lactococcus lactis and exo/hel enzymes of other low-guanine-plus-cytosine branch gram-positive bacteria contain two subunits. We report that RexAB functions via a novel mechanism compared to that of the RecBCD model. Two potential nuclease motifs are present in RexAB compared with a single nuclease in RecBCD. Site-specific mutagenesis of the RexA nuclease motif abolished all nuclease activity. In contrast, the RexB nuclease motif mutants displayed strongly reduced nuclease activity but maintained Chi recognition and had a Chi-stimulated hyperrecombination phenotype. The distinct phenotypes resulting from RexA or RexB nuclease inactivation lead us to suggest that each of the identified active nuclease sites in RexAB is involved in the degradation of one DNA strand. In RecBCD, the single RecB nuclease degrades both DNA strands and is presumably positioned by RecD. The presence of two nucleases would suggest that this RecD function is dispensable in RexAB. 相似文献
69.
Maruf Mohammad Akbor Koji Tomobe Tomomi Yamada Juhyon Kim Hiroki Mano Nobuyuki Kurosawa Kazuo Sasaki Yasuyuki Nomura Masaharu Isobe 《Biochemical and biophysical research communications》2013
The senescence-accelerated mouse prone 8 (SAMP8) strain exhibits age-related learning and memory deficits (LMD) at 2 months of age. Combined linkage analysis of 264 F2 intercross SAMP8 × JF1 mice and RNA-seq analysis identified Hcn1 gene out of 29 genes in the LMD region on chromosome 13. Hcn1 in SAMP8 strain showed 15 times less polyglutamine repetition compared to Japanese fancy mouse 1 (JF1). Whole cell patch clamp analysis showed that Hcn1 ion conductivity was significantly lower in SAMP8 compared to that of JF1, which may be associated with learning and memory deficiency. 相似文献
70.