全文获取类型
收费全文 | 13764篇 |
免费 | 1030篇 |
国内免费 | 38篇 |
专业分类
耳鼻咽喉 | 183篇 |
儿科学 | 355篇 |
妇产科学 | 363篇 |
基础医学 | 1727篇 |
口腔科学 | 231篇 |
临床医学 | 1476篇 |
内科学 | 2695篇 |
皮肤病学 | 97篇 |
神经病学 | 1244篇 |
特种医学 | 475篇 |
外科学 | 2187篇 |
综合类 | 174篇 |
一般理论 | 13篇 |
预防医学 | 1222篇 |
眼科学 | 846篇 |
药学 | 696篇 |
中国医学 | 9篇 |
肿瘤学 | 839篇 |
出版年
2023年 | 64篇 |
2022年 | 126篇 |
2021年 | 311篇 |
2020年 | 160篇 |
2019年 | 235篇 |
2018年 | 335篇 |
2017年 | 243篇 |
2016年 | 239篇 |
2015年 | 343篇 |
2014年 | 450篇 |
2013年 | 636篇 |
2012年 | 955篇 |
2011年 | 1016篇 |
2010年 | 557篇 |
2009年 | 496篇 |
2008年 | 904篇 |
2007年 | 904篇 |
2006年 | 933篇 |
2005年 | 906篇 |
2004年 | 864篇 |
2003年 | 797篇 |
2002年 | 775篇 |
2001年 | 147篇 |
2000年 | 105篇 |
1999年 | 162篇 |
1998年 | 148篇 |
1997年 | 132篇 |
1996年 | 103篇 |
1995年 | 107篇 |
1994年 | 105篇 |
1993年 | 84篇 |
1992年 | 92篇 |
1991年 | 75篇 |
1990年 | 81篇 |
1989年 | 74篇 |
1988年 | 65篇 |
1987年 | 77篇 |
1986年 | 64篇 |
1985年 | 82篇 |
1984年 | 92篇 |
1983年 | 73篇 |
1982年 | 88篇 |
1981年 | 104篇 |
1980年 | 84篇 |
1979年 | 53篇 |
1978年 | 49篇 |
1977年 | 32篇 |
1976年 | 35篇 |
1975年 | 28篇 |
1974年 | 26篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
Neuroprotective effects of IGF-I against TNFalpha-induced neuronal damage in HIV-associated dementia
Ying Wang J Peruzzi F Lassak A Del Valle L Radhakrishnan S Rappaport J Khalili K Amini S Reiss K 《Virology》2003,305(1):66-76
Human immunodeficiency virus type 1 (HIV-1) infection often results in disorders of the central nervous system, including HIV-associated dementia (HAD). It is suspected that tumor necrosis factor-alpha (TNFalpha) released by activated and/or infected macrophages/microglia plays a role in the process of neuronal damage seen in AIDS patients. In light of earlier studies showing that the activation of the insulin-like growth factor I receptor (IGF-IR) exerts a strong neuroprotective effect, we investigated the ability of IGF-I to protect neuronal cells from HIV-infected macrophages. Our results demonstrate that the conditioned medium from HIV-1-infected macrophages, HIV/CM, causes loss of neuronal processes in differentiated PC12 and P19 neurons and that these neurodegenerative effects are associated with the presence of TNFalpha. Furthermore, we demonstrate that IGF-I rescues differentiated neurons from both HIV/CM and TNFalpha-induced damage and that IGF-I-mediated neuroprotection is strongly enhanced by overexpression of the wt IGF-IR cDNA and attenuated by the antisense IGF-IR cDNA. Finally, IGF-I-mediated antiapoptotic pathways are continuously functional in differentiated neurons exposed to HIV/CM and are likely supported by TNFalpha-mediated phosphorylation of I(kappa)B. All together these results suggest that the balance between TNFalpha and IGF-IR signaling pathways may control the extent of neuronal injury in this HIV-related experimental setting. 相似文献
92.
Use of 16S rRNA gene sequencing for rapid identification and differentiation of Burkholderia pseudomallei and B. mallei
下载免费PDF全文
![点击此处可从《Journal of clinical microbiology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Gee JE Sacchi CT Glass MB De BK Weyant RS Levett PN Whitney AM Hoffmaster AR Popovic T 《Journal of clinical microbiology》2003,41(10):4647-4654
Burkholderia pseudomallei and B. mallei, the causative agents of melioidosis and glanders, respectively, are designated category B biothreat agents. Current methods for identifying these organisms rely on their phenotypic characteristics and an extensive set of biochemical reactions. We evaluated the use of 16S rRNA gene sequencing to rapidly identify these two species and differentiate them from each other as well as from closely related species and genera such as Pandoraea spp., Ralstonia spp., Burkholderia gladioli, Burkholderia cepacia, Burkholderia thailandensis, and Pseudomonas aeruginosa. We sequenced the 1.5-kb 16S rRNA gene of 56 B. pseudomallei and 23 B. mallei isolates selected to represent a wide range of temporal, geographic, and origin diversity. Among all 79 isolates, a total of 11 16S types were found based on eight positions of difference. Nine 16S types were identified in B. pseudomallei isolates based on six positions of difference, with differences ranging from 0.5 to 1.5 bp. Twenty-two of 23 B. mallei isolates showed 16S rRNA gene sequence identity and were designated 16S type 10, whereas the remaining isolate was designated type 11. This report provides a basis for rapidly identifying and differentiating B. pseudomallei and B. mallei by molecular methods. 相似文献
93.
The Escherichia coli O26 serogroup includes important food-borne pathogens associated with human and animal diarrheal disease. Current typing methods have revealed great genetic heterogeneity within the O26 group; the data are often inconsistent and focus only on verotoxin (VT)-positive O26 isolates. To improve current understanding of diversity within this serogroup, the genomic relatedness of VT-positive and -negative O26 strains was assessed by comparative genomic indexing. Our results clearly demonstrate that irrespective of virulence characteristics and pathotype designation, the O26 strains show greater genomic similarity to each other than to any other strain included in this study. Our data suggest that enteropathogenic and VT-expressing E. coli O26 strains represent the same clonal lineage and that VT-expressing E. coli O26 strains have gained additional virulence characteristics. Using this approach, we established the core genes which are central to the E. coli species and identified regions of variation from the E. coli K-12 chromosomal backbone. 相似文献
94.
Extravasation and transcytosis of liposomes in Kaposi's sarcoma-like dermal lesions of transgenic mice bearing the HIV tat gene. 总被引:2,自引:0,他引:2
下载免费PDF全文
![点击此处可从《The American journal of pathology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
S. K. Huang F. J. Martin G. Jay J. Vogel D. Papahadjopoulos D. S. Friend 《The American journal of pathology》1993,143(1):10-14
Transgenic mice bearing the HIV tat gene develop dermal lesions resembling a common malignant tumor in AIDS, Kaposi's sarcoma (KS). To evaluate the permeability characteristics of these lesions and the therapeutic potential of drug-carrying liposomes, we have studied the localization of sterically stabilized liposomes, which show long circulation time in blood and increased accumulation in tumors. Liposomes encapsulating colloidal gold were injected intravenously into transgenic mice bearing KS lesions, and tissues were processed 24 hours later for both electron microscopy and for light microscopy with silver enhancement. Liposomes and silver marker were detected predominantly in the dermis surrounding the early and mature KS lesions, which were characterized by a proliferation of fibroblast-like spindle cells and abnormal blood vessels close to the epidermis. The silver-enhanced gold marker often surrounded vascular channels and scattered erythrocytes. As determined by electron microscopy, some spindle cells and macrophages had ingested intact liposomes. Transendothelial transport of liposomes was observed both through open channels between endothelial cells and also through endothelial cells lining intact vessels. Both extravasation and transcytosis of liposomes through irregular endothelium were much higher in KS lesions than in the adjacent normal skin. The high accumulation of sterically stabilized liposomes in KS lesions and their intracellular uptake by some spindle cells enhances their potential as carriers of chemotherapeutic agents against this neoplasm. 相似文献
95.
OBJECTIVE: To identify subjects' changes in postural control during single-leg stance in the 4 weeks after acute lateral ankle sprain. DESIGN AND SETTING: We used a 2 x 2 x 3 (side-by-plane-by-session) within-subjects design with repeated measures on all 3 factors. All tests were performed in a university laboratory. SUBJECTS: Seventeen young adults (9 men, 8 women; age, 21.8 +/- 5.9 years; mass, 74.9 +/- 10.5 kg; height, 176.9 +/- 7.1 cm) who had sustained unilateral acute mild or moderate lateral ankle sprains. MEASUREMENTS: Measures of center-of-pressure excursion length, root mean square velocity of center-of-pressure excursions (VEL), and range of center-of-pressure excursions (RANGE) were calculated separately in the frontal and sagittal planes during 5-second trials of static single-leg stance. RESULTS: We noted significant side-by-plane-by-session interactions for magnitude of center-of-pressure excursions in a given trial (PSL) (P =.004), VEL (P =.011), and RANGE (P =.009). Both PSL and VEL in the frontal plane were greater in the injured limbs compared with the uninjured limbs on day 1 and during week 2 but not during week 4, whereas sagittal-plane differences existed during all 3 testing sessions. Injured-limb, frontal-plane RANGE scores were greater than uninjured values at day 1 but not during weeks 2 or 4. No significant differences in sagittal-plane RANGE scores were seen. CONCLUSIONS: Postural control was significantly impaired in the injured limbs at day 1 and during week 2 after lateral ankle sprain but not during week 4. Consistent improvement in postural control measures on both injured and uninjured limbs was seen throughout the 4 weeks after ankle sprain. 相似文献
96.
Linkage refinement localises Sorsby fundus dystrophy between markers D22S275 and D22S278. 总被引:3,自引:0,他引:3
下载免费PDF全文
![点击此处可从《Journal of medical genetics》网站下载免费的PDF全文](/ch/ext_images/free.gif)
C Y Gregory S Wijesuriya K Evans M Jay A C Bird S S Bhattacharya 《Journal of medical genetics》1995,32(3):240-241
Sorsby fundus dystrophy is an autosomal dominant disorder which both clinically and histopathologically bears striking similarities to age related macular degeneration, one of the leading causes of blindness in the developed world. Recent studies have suggested a genetic localisation of the disease to chromosome 22q in a large genetic interval of approximately 25 cM. Independent genetic linkage analysis in a six generation British pedigree confirms linkage to the chromosome 22q region. A maximum two point lod score of 7.09 with no recombination was obtained with marker D22S280. Haplotype data positioned the disease between loci D22S275 and D22S278, thus significantly reducing the region on chromosome 22q where the gene is located. 相似文献
97.
Taams LS Vukmanovic-Stejic M Smith J Dunne PJ Fletcher JM Plunkett FJ Ebeling SB Lombardi G Rustin MH Bijlsma JW Lafeber FP Salmon M Akbar AN 《European journal of immunology》2002,32(6):1621-1630
Anergic/suppressive CD4+CD25+ T cells have been proposed to play an important role in the maintenance of peripheral tolerance. Here we demonstrate that in humans these cells suppress proliferation to self antigens, but also to dietary and foreign antigens. The suppressive CD4+CD25+ T cells display a broad usage of the T cell receptor Vbeta repertoire,suggesting that they recognize a wide variety of antigens. They reside in the primed/memory CD4+CD45RO+CD45RB(low) subset and have short telomeres, indicating that these cells have the phenotype of highly differentiated CD4+ T cells that have experienced repeated episodes of antigen-specific stimulation in vivo. This suggests that anergic/suppressive CD4+CD25+ T cells may be generated in the periphery as a consequence of repeated antigenic encounter. This is supported by the observation that highly differentiated CD4+T cells can be induced to become anergic/suppressive when stimulated by antigen presented by non-professional antigen-presenting cells. We suggest that besides being generated in the thymus, CD4+CD25+ regulatory T cells may also be generated in the periphery. This would provide a mechanism for the generation of regulatory cells that induce tolerance to a wide array of antigens that may not be encountered in the thymus. 相似文献
98.
This study measured expression of Fos protein, an indicator of neural activation, in 116 brain regions of rats that were able to control a stressor (i.e., avoid and/or escape an electric shock), and compared the changes with those observed in yoked rats that received the same shocks but without having control over them. The authors' interest was to find brain regions where elevated activity occurs in conjunction with control. Activity in these brain regions might be responsible for the consequences of having control, such as reduction of stress responses. Eleven brain regions were found in which rats with control showed significantly more Fos expression than was seen in yoked rats that did not have control. Six of these brain regions were part of the mesocorticolimbic dopamine system. These results point to the mesocorticolimbic dopamine system as being importantly involved in the mediation and/or the consequences of coping behavior. 相似文献
99.
The effect of a competitive soccer match on maximal power performance was assessed on 19 members of an NCAA Division III female soccer team. Performance testing occurred within 24 hours prior to the game (Pre), immediately postgame (IP), and 24 hours postgame (24P). Each subject performed a squat jump (SJ) and countermovement jump (CMJ). Comparisons between starters (n = 10) and nonstarters (n = 9) revealed no between-group differences in power performance at IP, but starters were found to have significantly lower power and force measures at 24P than nonstarters. There were significant correlations between playing time and peak force during the SJ at 24P (r = -0.47), and between playing time and peak power during the SJ at IP (r = -0.57) and 24P (r = -0.51), and during the CMJ at IP (r = -0.49). Comparisons between different positions revealed no differential fatigue patterns. Results of this study show that power performance appears to be maintained for the duration of a soccer match but declines significantly within 24 hours after the match. Position played does not appear to affect performance decrements seen at 24 hours postmatch. 相似文献
100.
Interleukin-17: an emerging role in lung inflammation 总被引:5,自引:0,他引:5