全文获取类型
收费全文 | 17163篇 |
免费 | 1032篇 |
国内免费 | 66篇 |
专业分类
耳鼻咽喉 | 215篇 |
儿科学 | 520篇 |
妇产科学 | 381篇 |
基础医学 | 2525篇 |
口腔科学 | 910篇 |
临床医学 | 1994篇 |
内科学 | 3310篇 |
皮肤病学 | 362篇 |
神经病学 | 1553篇 |
特种医学 | 308篇 |
外科学 | 1395篇 |
综合类 | 127篇 |
一般理论 | 10篇 |
预防医学 | 2061篇 |
眼科学 | 300篇 |
药学 | 1132篇 |
中国医学 | 84篇 |
肿瘤学 | 1074篇 |
出版年
2024年 | 19篇 |
2023年 | 180篇 |
2022年 | 355篇 |
2021年 | 684篇 |
2020年 | 408篇 |
2019年 | 612篇 |
2018年 | 653篇 |
2017年 | 468篇 |
2016年 | 466篇 |
2015年 | 570篇 |
2014年 | 741篇 |
2013年 | 923篇 |
2012年 | 1456篇 |
2011年 | 1577篇 |
2010年 | 768篇 |
2009年 | 678篇 |
2008年 | 1164篇 |
2007年 | 1104篇 |
2006年 | 1036篇 |
2005年 | 930篇 |
2004年 | 789篇 |
2003年 | 753篇 |
2002年 | 724篇 |
2001年 | 102篇 |
2000年 | 78篇 |
1999年 | 73篇 |
1998年 | 138篇 |
1997年 | 87篇 |
1996年 | 74篇 |
1995年 | 61篇 |
1994年 | 59篇 |
1993年 | 54篇 |
1992年 | 35篇 |
1991年 | 39篇 |
1990年 | 36篇 |
1989年 | 16篇 |
1988年 | 19篇 |
1987年 | 25篇 |
1986年 | 28篇 |
1985年 | 22篇 |
1984年 | 27篇 |
1983年 | 28篇 |
1982年 | 29篇 |
1981年 | 25篇 |
1980年 | 25篇 |
1979年 | 17篇 |
1977年 | 11篇 |
1976年 | 8篇 |
1975年 | 10篇 |
1930年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
Lymphotoxin but not tumor necrosis factor functions to maintain splenic architecture and humoral responsiveness in adult mice 总被引:1,自引:0,他引:1
Fabienne Mackay Gerard R. Majeau Pornsri Lawton Paula S. Hochman Jeffrey L. Browning 《European journal of immunology》1997,27(8):2033-2042
To compare the function of the tumor necrosis factor (TNF) and lymphotoxin (LT)α/β systems in the mature immune system, these two pathways were blocked with soluble receptor-immunoglobulin (R-Ig) fusion proteins in normal adult mice. Inhibition of LTα/β signaling using LTβR-Ig or a blocking monoclonal antibody against murine LTβ had profound effects. The spleen lacked discrete B cell follicles and the marginal zone was altered. Less marked changes were detected in lymph nodes. LTα/β inhibition also prevented germinal center formation in the spleen and impaired Ig production in response to sheep red blood cells (SRBC) immunization. These results show that the LTα/β system is required for the maintenance of splenic architecture and normal immune responses, and not simply for the development of peripheral immune organs during ontogeny. In contrast, inhibition of the TNF/LTα pathway with TNF-R55-Ig did not affect the splenic architecture or the anti-SRBC response. Splenic defects and impaired antibody responses are seen in TNF-deficient mice, suggesting that TNF is important during development. Therefore relative to TNF, the LT system has the dominant influence on splenic organization and anti-SRBC Ig formation in the adult mouse. 相似文献
82.
83.
Prevalence and correlates of HIV infection among young injection drug users in San Francisco 总被引:1,自引:0,他引:1
Shafer KP Hahn JA Lum PJ Ochoa K Graves A Moss A 《Journal of acquired immune deficiency syndromes (1999)》2002,31(4):422-431
OBJECTIVE: We assessed the prevalence of HIV infection and associated risk behaviors among street-recruited young injection drug users (IDUs) in San Francisco. METHODS: In a cross-sectional study, 304 young (age <30 years) IDUs with a history of injecting in the previous 30 days were interviewed and tested for antibodies to HIV. Analyses assessing independent associations with HIV infection were limited to males only, due to the low number of infections in women. RESULTS: The prevalence of HIV infection was 5.3% overall but was highly stratified by gender and sexual preference (15.6% among homosexual/bisexual men vs. heterosexual men) and recruitment neighborhood (18% in the Polk Street area). Of 16 HIV infections, 14 (88%) were in males. Factors independently associated with HIV infection in males included sexual preference (homosexual/bisexual vs. heterosexual: adjusted odds ratio [AOR], 7.5; 95% confidence interval [CI], 1.5-36.6), recruitment neighborhood (Polk Street neighborhood vs. other neighborhoods: AOR, 4.8; 95% CI, 1.4-16.7), and duration of residence in San Francisco (>or=1 year vs. <1 year: AOR, 11.8; 95% CI, 1.4-95.8). CONCLUSIONS: The prevalence of HIV infection was highest among male IDUs who have sex with men. The strong associations between HIV infection and sexual orientation and HIV infection and recruitment locale suggest that risk may be attributable largely to sexual risk. In addition to successful prevention efforts aimed at reducing needle-associated risk, current intervention models aimed at young IDUs should target high-risk neighborhoods and emphasize sexual risk reduction measures, in particular among men who have sex with men. 相似文献
84.
85.
Emergence of nonencapsulated and encapsulated non-b-type invasive Haemophilus influenzae isolates in Portugal (1989-2001)
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)
Phenotypes and genetic relatedness of invasive Haemophilus influenzae strains were evaluated from 1989 through 2001. Among 119 isolates, multidrug resistance decreased (from 50 to 0%), the level of H. influenzae serotype b (Hib) strains declined (from 81 to 16%), the level of noncapsulated strains rose (from 19 to 80%), and the first invasive H. influenzae serotype f strain was described. This study documents changes in invasive H. influenzae infections in Portugal, i.e., the emergence of non-type-b strains that are genetically diverse and unrelated to Hib. 相似文献
86.
Limb girdle muscular dystrophy type 2A (LGMD2A) is caused by mutations in the calpain 3 gene. In a large family affected by LGMD2A with four severely affected members, three additional asymptomatic relatives had very high serum creatine kinase concentrations. All were homozygous for the R110X mutation and showed a total absence of calpain 3 in the muscle. Histological analysis of muscle in these three rare preclinical cases showed a consistent but unusual pattern, with isolated fascicles of degenerating fibres in an almost normal muscle. This pattern was also seen in one patient with early stage LGMD2A who had a P82L missense mutation and a partial deficiency of calpain 3 in the muscle, but was not seen in early stage patients affected by other forms of LGMD. These findings suggest that a peculiar pattern of focal degeneration occurs in calpainopathy, independently of the type of mutation or the amount of calpain 3 in the muscle. 相似文献
87.
Geoffrey Nelson Joanna Ochocka Rich Janzen John Trainor Paula Goering Jonathan Lomotey 《Journal of community psychology》2007,35(5):655-665
The objective of this study was to evaluate the impacts of participation in mental health Consumer/Survivor Initiatives (CSIs), organizations run by and for people with mental illness. A nonequivalent comparison group design was used to compare three groups of participants: (a) those who were continually active in CSIs over a 36‐month period (n = 25); (b) those who had been active in CSIs at 9‐ and 18‐month follow‐up periods, but who were no longer active at 36 months (n = 35); and (c) a comparison group of participants who were never active in CSIs (n = 42). Data were gathered at baseline, 9‐, 18‐, and 36‐month follow‐ups. The three groups were comparable at baseline on a wide range of demographic variables, self‐reported psychiatric diagnosis, service use, and outcome measures. At 36 months, the continually active participants scored significantly higher than the other two groups of participants on community integration, quality of life (daily living activities), and instrumental role involvement, and significantly lower on symptom distress. No differences between the groups were found on other outcome measures. Improvements in 36‐month outcomes for people with mental illness who participated in CSIs suggest the potential value of these peer support organizations. Further research is needed to determine the replicability of these positive findings. © 2007 Wiley Periodicals, Inc. J Comm Psychol 35: 655–665, 2007. 相似文献
88.
Sobrinho-Simões M Preto A Rocha AS Castro P Máximo V Fonseca E Soares P 《Virchows Archiv : an international journal of pathology》2005,447(5):787-793
The newly discovered molecular features of well-differentiated thyroid carcinomas derived from follicular cells are reviewed,
within the frame of the 2004 WHO classification of thyroid tumours, under the following headings: “Follicular carcinoma”,
“Papillary carcinoma”, “Follicular variant of papillary carcinoma” and “Hürthle cell tumours”. A particular emphasis is put
on the meaning of PAX8–PPARγ rearrangements, RAS and BRAF mutations, and deletions and mutations of mitochondrial genes and of nuclear genes encoding for mitochondrial enzymes, for
thyroid tumorigenesis. 相似文献
89.
Donangelo I Marcos HP Araújo PB Marcondes J Filho PN Gadelha M Chimelli L 《Endocrine pathology》2005,16(1):53-62
The retinoblastoma gene (RB1) is a tumor-suppressor gene in chromosomal region 13q14.2. Its role in the pathogenesis of pituitary tumors has not been
fully clarified. Some studies have shown that losses in this chromosomal region are related to aggressive tumor behavior,
although the retinoblastoma protein (pRB) is still expressed. Conversely, lack of expression of pRB was observed in one fourth
of GH-secreting pituitary adenomas (GH-tumors). In order to further study the expression of pRB in GH-tumors, we evaluated
this protein in 49 tumors from patients with acromegaly (20 noninvasive, 25 invasive, and 4 with no information) and 8 normal
pituitaries using immunohistochemistry (IHC). Nuclear staining for pRB ranged from 0 to 90% (median 40%) in the tumors and
from 40 to 80% (median 58%) in normal pituitaries. In 10 tumors (20% of total) the adenomatous cells were negative (5 cases)
or had very low labeling (5 cases) for pRB. Sixty three percent (31/49) of the tumors showed staining in 10–80% of the cells
and in 16% (8/49) of the cases >80% of the adenomatous cells were positive for pRB. The expression of pRB was not different
in invasive and noninvasive tumors. In conclusion, pRB is underexpressed in a subgroup of GH-tumors, and this may represent
an early event in the pathogenesis of this tumor subtype. 相似文献
90.
New microsatellite multiplex PCR for Candida albicans strain typing reveals microevolutionary changes 总被引:4,自引:0,他引:4
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)
Sampaio P Gusmão L Correia A Alves C Rodrigues AG Pina-Vaz C Amorim A Pais C 《Journal of clinical microbiology》2005,43(8):3869-3876
Five new microsatellite loci were described and characterized for use as molecular markers for the identification and genetic differentiation of Candida albicans strains. Following the typing of 72 unrelated clinical isolates, the analysis revealed that they were all polymorphic, presenting from 5 to 30 alleles and 8 to 46 different genotypes. The discriminatory power obtained by combining the information generated by three microsatellites used in a multiplex PCR amplification strategy was 0.99, the highest ever reported. The multiplex PCR was later used to test a total of 114 C. albicans strains, including multiple isolates from the same patient collected from different body locations and along episodes of vulvovaginal infections. Three different scenarios for strain relatedness were identified: (i) different isolates that were revealed to be the same strain, (ii) isolates that were the same strain but that apparently underwent a process of microevolution, and (iii) isolates that corresponded to different strains. Analysis of the microevolutionary changes between isolates from recurrent infections indicated that the genotype alterations observed could be the result of events that lead to the loss of heterozygosity (LOH). In one case of recurrent infection, LOH was observed at the CAI locus, and this could have been related to exposure to fluconazole, since such strains were exposed to this antifungal during treatment. The analysis of microsatellites by a multiplex PCR strategy was found to be a highly efficient tool for the rapid and accurate differentiation of C. albicans strains and adequate for the identification of fine microevolutionary events that could be related to strain microevolution in response to environmental stress conditions. 相似文献