全文获取类型
收费全文 | 4278篇 |
免费 | 334篇 |
国内免费 | 26篇 |
专业分类
耳鼻咽喉 | 29篇 |
儿科学 | 135篇 |
妇产科学 | 131篇 |
基础医学 | 590篇 |
口腔科学 | 115篇 |
临床医学 | 361篇 |
内科学 | 1099篇 |
皮肤病学 | 97篇 |
神经病学 | 301篇 |
特种医学 | 272篇 |
外科学 | 597篇 |
综合类 | 47篇 |
预防医学 | 370篇 |
眼科学 | 54篇 |
药学 | 211篇 |
中国医学 | 30篇 |
肿瘤学 | 199篇 |
出版年
2023年 | 20篇 |
2022年 | 53篇 |
2021年 | 98篇 |
2020年 | 69篇 |
2019年 | 121篇 |
2018年 | 112篇 |
2017年 | 106篇 |
2016年 | 79篇 |
2015年 | 95篇 |
2014年 | 132篇 |
2013年 | 185篇 |
2012年 | 217篇 |
2011年 | 217篇 |
2010年 | 131篇 |
2009年 | 119篇 |
2008年 | 176篇 |
2007年 | 191篇 |
2006年 | 218篇 |
2005年 | 197篇 |
2004年 | 164篇 |
2003年 | 160篇 |
2002年 | 135篇 |
2001年 | 116篇 |
2000年 | 140篇 |
1999年 | 114篇 |
1998年 | 58篇 |
1997年 | 54篇 |
1996年 | 48篇 |
1995年 | 40篇 |
1994年 | 40篇 |
1993年 | 44篇 |
1992年 | 87篇 |
1991年 | 71篇 |
1990年 | 67篇 |
1989年 | 81篇 |
1988年 | 72篇 |
1987年 | 68篇 |
1986年 | 58篇 |
1985年 | 58篇 |
1984年 | 51篇 |
1983年 | 52篇 |
1982年 | 36篇 |
1981年 | 29篇 |
1980年 | 22篇 |
1979年 | 29篇 |
1978年 | 24篇 |
1977年 | 22篇 |
1976年 | 30篇 |
1975年 | 18篇 |
1974年 | 21篇 |
排序方式: 共有4638条查询结果,搜索用时 15 毫秒
31.
Reyes A Moran CA Suster S Michal M Dominguez H 《American journal of clinical pathology》2003,120(2):182-187
We studied 10 cases of primary pure testicular neuroendocrine carcinoma. Patients were between 16 and 48 years old and had testicular swelling with pain or a painless testicular mass and no history of neuroendocrine carcinoma or other malignant neoplasm. All underwent orchiectomy. The tumors were low (n = 9) and intermediate (n = 1) grades with a variegated histologic appearance characterized by a nesting pattern, cords of neoplastic cells with rosettes, or sheets of neoplastic cells. Mitotic activity was lacking in 9 cases. In 1 case, mitotic figures ranged from 7 to 8 per 10 high-power fields, and cellular atypia and comedo-like necrosis were present. Immunohistochemical studies using a keratin cocktail, chromogranin, synaptophysin, epidermal growth factor, p53, placental-like alkaline phosphatase, and CD117 (c-kit) were performed in all cases. Keratin, chromogranin, and synaptophysin were positive in all tumors. Clinical follow-up information was obtained for 6 patients (range, 12-60 months): 5 with low-grade tumors were alive 24 to 60 months after diagnosis; 1 with an intermediate-grade tumor died of tumor 12 months after initial diagnosis. The behavior of these tumors, while in the testicular region, correlates well with the histologic grade. We propose replacing the term testicular carcinoid with neuroendocrine carcinoma, which better reflects the nature of these neoplasms. 相似文献
32.
Use of quantitative competitive PCR to measure Epstein-Barr virus genome load in the peripheral blood of pediatric transplant patients with lymphoproliferative disorders. 总被引:13,自引:8,他引:13
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)
D T Rowe L Qu J Reyes N Jabbour E Yunis P Putnam S Todo M Green 《Journal of clinical microbiology》1997,35(6):1612-1615
A quantitative competitive PCR (QC-PCR) assay for Epstein-Barr virus (EBV) has been developed to provide accurate measurement of EBV genome load in pediatric transplant recipients at risk for developing posttransplant lymphoproliferative disorder (PTLD). The assay quantifies between 8 and 5,000 copies of the EBV genome in 10(5) lymphocytes after a 30-cycle amplification reaction. For 14 pediatric patients diagnosed with PTLD, the median EBV genome load was 4,000, and 13 of the 14 patients had values of >500 copies per 10(5) lymphocytes. Only 3 of 12 control transplant recipients not diagnosed with PTLD had detectable viral genome loads (median value, 40). This median was calculated by using the highest value obtained by PCR testing on each of these patients posttransplantation. PCR values of >500 copies per 10(5) lymphocytes appear to correlate with a diagnosis of PTLD. By a modified protocol, the EBV genome copy number in latently infected adults was estimated to be <0.1 copy per 10(5) lymphocytes. 相似文献
33.
34.
Life expectancy in British Marfan syndrome populations 总被引:2,自引:0,他引:2
JR Gray AB Bridges RR West L. McLeish AG Stuart JCS Dean MEM Porteous M. Boxer SJ Davies 《Clinical genetics》1998,54(2):124-128
A total of 206 patients with Marfan syndrome were ascertained throughout genetic clinics in Wales and Scotland during the period 1970–1990. There were 45 deaths representing 22% of the cohort. Mean age at death was 45.3 ± 16.5 years. 50% median cumulative survival in the total cohort (n = 206) was 53 years for males and 72 years for females. Multivariate analysis confirmed severity as the best independent indicator of survival. These findings and survival curves will assist in the counselling of British families and individuals with Marfan syndrome. 相似文献
35.
Titanium-porcelain system. Part III: effects of surface modification on bond strengths 总被引:1,自引:0,他引:1
Reyes MJ Oshida Y Andres CJ Barco T Hovijitra S Brown D 《Bio-medical materials and engineering》2001,11(2):117-136
During its development, titanium was found to be incompatible with conventional dental porcelains due to weak bond strength brought about by titanium's high yet oxidative nature. In spite of the development of new low-fusing porcelains designed for titanium application, previous studies have shown that sandblasting pre-treatment prior to porcelain application led to weakening of the metal-ceramic bonding. The aim of this study is to search for an effective alternative to sandblasting for the surface treatment of the titanium substrate in the titanium-porcelain system. The research evaluated the bond strength of 165 samples of titanium-porcelain systems divided into 11 groups. A three-point flexural bend test was conducted to measure the force required to fracture the porcelain on the titanium substrate. A correlation between the type of surface treatment and the bond strengths of each group was evaluated if it resulted to significant differences. The study found significantly differences in the energy-to-break of titanium-porcelain systems treated with hydrochloric acid and sandblasting compared with the control group. The bonds strength achieved by the titanium-porcelain system when treated with hydrochloric acid is comparable to that of conventional metal-ceramic alloy system. Hydrochloric acid treatment of the titanium substrate is a promising alternative to sandblasting for the surface treatment of the titanium substrate in the titanium-porcelain system. 相似文献
36.
37.
Solid-phase enzyme-linked immunosorbent assay for hepatitis E virus IgG and IgM antibodies utilizing recombinant antigens and synthetic peptides. 总被引:17,自引:0,他引:17
G J Dawson K H Chau C M Cabal P O Yarbough G R Reyes I K Mushahwar 《Journal of virological methods》1992,38(1):175-186
Four recombinant antigens representing two distinct antigenic domains from two different strains of hepatitis E virus (HEV), were used individually to develop four ELISAs designed to detect antibodies to HEV. Both IgG and IgM class antibodies to HEV were detected in 7 of 8 pedigreed serum/plasma from known outbreaks of HEV in Mexico, Burma, Somalia and Pakistan. In addition, specific HEV-antibodies were detected in cynomolgus macaques following inoculation with various HEV strains. Anti-HEV was also detected in 8 of 386 (2.1%) randomly selected American blood donors. Supplemental tests utilizing both synthetic peptides and specific blocking assays provided additional serologic data confirming the presence of anti-HEV. Similar prevalence studies on a limited number of available sera from other geographical regions (Alaska, Japan, Germany, New Zealand, Thailand and Mexico) confirmed the presence of anti-HEV in at least 1.1 to 7.6% of the specimens. 相似文献
38.
Genetic composition and complexity of virus populations at tungro-endemic and outbreak rice sites 总被引:1,自引:0,他引:1
Azzam O Arboleda M Umadhay KM de los Reyes JB Cruz FS Mackenzie A McNally KL 《Archives of virology》2000,145(12):2643-2657
Summary. We have recently demonstrated the geographic isolation of rice tungro bacilliform virus (RTBV) populations in the tungro-endemic
provinces of Isabela and North Cotabato, Philippines. In this study, we examined the genetic structure of the virus populations
at the tungro-outbreak sites of Lanao del Norte, a province adjacent to North Cotabato. We also analyzed the virus populations
at the tungro-endemic sites of Subang, Indonesia, and Dien Khanh, Vietnam. Total DNA extracts from 274 isolates were digested
with EcoRV restriction enzyme and hybridized with a full-length probe of RTBV. In the total population, 22 EcoRV-restricted genome profiles (genotypes) were identified. Although overlapping genotypes could be observed, the outbreak
sites of Lanao del Norte had a genotype combination distinct from that of Subang or Dien Khanh but a genotype combination
similar to that identified earlier from North Cotabato, the adjacent endemic province. Sequence analysis of the intergenic
region and part of the ORF1 RTBV genome from randomly selected genotypes confirms the geographic clustering of RTBV genotypes
and, combined with restriction analysis, the results suggest a fragmented spatial distribution of RTBV local populations in
the three countries. Because RTBV depends on rice tungro spherical virus (RTSV) for transmission, the population dynamics
of both tungro viruses were then examined at the endemic and outbreak sites within the Philippines. The RTBV genotypes and
the coat protein RTSV genotypes were used as indicators for virus diversity. A shift in population structure of both viruses
was observed at the outbreak sites with a reduced RTBV but increased RTSV gene diversity.
Accepted April 28, 2000 Received November 26, 1999 相似文献
39.
Human MSH2 binds to trinucleotide repeat DNA structures associated with neurodegenerative diseases 总被引:5,自引:5,他引:5
The expansion of trinucleotide repeat sequences is associated with several
neurodegenerative diseases. The mechanism of this expansion is unknown but
may involve slipped-strand structures where adjacent rather than perfect
complementary sequences of a trinucleotide repeat become paired. Here, we
have studied the interaction of the human mismatch repair protein MSH2 with
slipped-strand structures formed from a triplet repeat sequence in order to
address the possible role of MSH2 in trinucleotide expansion. Genomic
clones of the myotonic dystrophy locus containing disease-relevant lengths
of (CTG)n x (CAG)n triplet repeats were examined. We have constructed two
types of slipped-strand structures by annealing complementary strands of
DNA containing: (i) equal numbers of trinucleotide repeats (homoduplex
slipped structures or S-DNA) or (ii) different numbers of repeats
(heteroduplex slipped intermediates or SI-DNA). SI-DNAs having an excess of
either CTG or CAG repeats were structurally distinct and could be separated
electrophoretically and studied individually. Using a band-shift assay, the
MSH2 was shown to bind to both S-DNA and SI-DNA in a structure- specific
manner. The affinity of MSH2 increased with the length of the repeat
sequence. Furthermore, MSH2 bound preferentially to looped-out CAG repeat
sequences, implicating a strand asymmetry in MSH2 recognition. Our results
are consistent with the idea that MSH2 may participate in trinucleotide
repeat expansion via its role in repair and/or recombination.
相似文献
40.
Montes-Rodríguez CJ Alavez S Elder JH Haro R Morán J Prospéro-García O 《Neuroscience letters》2004,360(3):133-136
The human immunodeficiency virus (HIV) induces neuronal death, presumably by apoptosis. This effect may be triggered by the glycoprotein 120 (HIVgp120) released by HIV when infecting a cell, and mediated by tumor necrosis factor alpha (TNF), a pro-inflammatory cytokine. Both molecules, HIVgp120 and TNF, increase sleep when administered acutely in the brain. On the other hand, sleep deprivation increases the levels of several growth factors. In this context, we challenged rats with HIVgp120 or TNF simultaneously with sleep deprivation. Our results indicate that both HIVgp120 and TNF increase neuronal death in the rat cerebral cortex, but not hippocampus, and that this effect is completely prevented by total deprivation of sleep. These results suggest that acute total deprivation of sleep protects against the HIVgp120 and TNF deleterious effects. 相似文献