首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   27207篇
  免费   1806篇
  国内免费   253篇
耳鼻咽喉   424篇
儿科学   446篇
妇产科学   591篇
基础医学   3939篇
口腔科学   701篇
临床医学   2350篇
内科学   5209篇
皮肤病学   585篇
神经病学   2020篇
特种医学   1641篇
外科学   4356篇
综合类   290篇
一般理论   10篇
预防医学   1127篇
眼科学   663篇
药学   2342篇
  1篇
中国医学   270篇
肿瘤学   2301篇
  2023年   162篇
  2022年   384篇
  2021年   711篇
  2020年   387篇
  2019年   664篇
  2018年   719篇
  2017年   594篇
  2016年   690篇
  2015年   1023篇
  2014年   1264篇
  2013年   1432篇
  2012年   2132篇
  2011年   2091篇
  2010年   1295篇
  2009年   1193篇
  2008年   1626篇
  2007年   1560篇
  2006年   1454篇
  2005年   1381篇
  2004年   1246篇
  2003年   1084篇
  2002年   955篇
  2001年   776篇
  2000年   761篇
  1999年   604篇
  1998年   230篇
  1997年   215篇
  1996年   193篇
  1995年   164篇
  1994年   139篇
  1993年   115篇
  1992年   243篇
  1991年   186篇
  1990年   180篇
  1989年   177篇
  1988年   152篇
  1987年   111篇
  1986年   98篇
  1985年   74篇
  1984年   82篇
  1983年   52篇
  1982年   56篇
  1981年   50篇
  1980年   46篇
  1979年   58篇
  1978年   47篇
  1977年   53篇
  1974年   37篇
  1972年   45篇
  1971年   42篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
This study analyzed the expression of anti-islet autoantibodies and HLA-DR and -DQ genotypes in Korean children with type 1 diabetes mellitus (T1DM). The positivity of the anti-ICA512, anti-GAD65, and anti-insulin autoantibodies in the newly onset T1DM patients (n = 15) was 66.7%, 86.7%, and 46.7%, respectively, and all of them had one or more of the autoantibodies. HLA analysis showed higher frequencies of HLA-DRB1*0301, *0405, *09012 and -DQB1*0201, *0401, *03032 alleles in T1DM patients compared to controls (P(c) < 0.05). Because HLA-DQB1*0401, *03032 alleles carry aspartic acid at position 57 of DQB, susceptibility to T1DM in Korean children was not related to the presence of aspartic acid at position 57 of DQB1 locus. We suggest this unique HLA-DR, -DQ allele distribution might be an important factor for the low incidence of T1DM in Korea, and the combined anti-islet autoantibody assays could be valuable screening markers for the early detection of T1DM in Korea.  相似文献   
992.
Spinocerebellar ataxia type 1 (SCA1) is an autosomal dominant neurodegenerative disorder caused by the expansion of a CAG trinucleotide repeat which encodes glutamine in the novel protein ataxin-1. In order to characterize the developmental expression pattern of SCA1 and to identify putative functional domains in ataxin-1, the murine homolog (Sca1) was isolated. Cloning and characterization of the murine Sca1 gene revealed that the gene organization is similar to that of the human gene. The murine and human ataxin-1 are highly homologous but the CAG repeat is virtually absent in the mouse sequence suggesting that the polyglutamine stretch is not essential for the normal function of ataxin-1 in mice. Cellular and developmental expression of the murine homolog was examined using RNA in situ hybridization. During cerebellar development, there is a transient burst of Sca1 expression at postnatal day 14 when the murine cerebellar cortex becomes physiologically functional. There is also marked expression of Sca1 in mesenchymal cells of the intervertebral discs during development of the spinal column. These results suggest that the normal Sca1 gene, has a role at specific stages of both cerebellar and vertebral column development.   相似文献   
993.
The imprinted H19 gene is frequently inactivated in Wilms' tumors (WTs) either by chromosome 11p15.5 loss of heterozygosity (LOH) or by hypermethylation of the maternal allele and it is possible that there might be coordinate disruption of imprinting of multiple 11p15.5 genes in these tumors. To test this we have characterized total and allele- specific mRNA expression levels and DNA methylation of the 11p15.5 KIP2 gene in normal human tissues, WTs and embryonal rhabdomyosarcoma (RMS). Both KIP2 alleles are expressed but there is a bias with the maternal allele contributing 70-90% of mRNA. Tumors with LOH show moderate to marked reductions in KIP2 mRNA relative to control tissues and residual mRNA expression is from the imprinted paternal allele. Among WTs without LOH most cases with H19 inactivation also have reduced KIP2 expression and most cases with persistent H19 expression have high levels of KIP2 mRNA. In contrast to the extensive hypermethylation of the imprinted H19 allele, both KIP2 alleles are hypomethylated and WTs with biallelic H19 hypermethylation lack comparable hypermethylation of KIP2 DNA. 5-aza-2'-deoxycytidine (aza-C) increases H19 expression in RD RMS cells but does not activate KIP2 expression. These data indicate coordinately reduced expression of two linked paternally imprinted genes in most WTs and also suggest mechanistic differences in the maintenance of imprinting at these two loci.   相似文献   
994.
Listeria monocytogenes causes major food-borne outbreaks of disease worldwide. Specific identification of this microorganism is of utmost importance to public health and industry. Listeria species are known to secrete a 60-kDa protein collectively termed p60, which is encoded by the iap (invasion-associated protein) gene and secreted in large quantities into the growth media. p60 is a highly immunogenic murein hydrolase that is essential for cell division. Due to these properties, p60 is an ideal diagnostic target for the development of immunological detection systems for L. monocytogenes. We report here two independent lines of monoclonal antibody (MAb): p6007, which specifically recognizes L. monocytogenes p60, and p6017, which reacts with a wide range of Listeria p60 proteins. By combining these antibodies with a polyclonal antibody, we developed efficient sandwich enzyme-linked immunosorbent assay (ELISA) systems which can specifically identify L. monocytogenes or generally detect Listeria species. Since an excess amount of the peptide corresponding to PepA or PepD did not interfere with the ELISA, and direct ELISAs were unable to detect both peptides, we concluded that the epitope presumed to be recognized by p6007 or p6017 could be distinguished from PepA and PepD as described by Bubert et al. (Appl. Environ. Microbiol. 60:3120-3127, 1997). To our best knowledge, this is the first example of an immunological identification system that uses p60-recognizing MAbs.  相似文献   
995.
The expression of vascular endothelial growth factor (VEGF) and fibroblast growth factor (FGF)2 in the irradiated brain was examined to test how a single high dose radiation, similar to that used for intraoperative radiation therapy given to the normal cerebrum, can affect the vascular endothelium. After a burr hole trephination in the rat skull, the cerebral hemisphere was exposed to a single 10 Gy dose of gamma rays, and the radiation effect was assessed at 1, 2, 4, 6, and 8 weeks after irradiation. Histological changes, such as reactive gliosis, inflammation, vascular proliferation and necrosis, were correlated with the duration after irradiation. Significant VEGF and FGF2 expression in the 2- and 8-week were detected by enzyme-linked immunosorbent assay quantification in the radiation group. Immunohistochemical study for VEGF was done and the number of positive cells gradually increased over time, compared with the sham operation group. In conclusion, the radiation injuries consisted of radiation necrosis associated with the expression of VEGF and FGF2. These findings indicate that VEGF and FGF2 may play a role in the radiation injuries after intraoperative single high-dose irradiation.  相似文献   
996.
AIMS: To study the expression of mucins in peripheral airways in patients with chronic obstructive pulmonary disease (COPD). METHODS AND RESULTS: Peripheral lung sections from smokers with COPD (n = 9) and age-matched controls including smokers (n = 11) and lifelong non-smokers with normal lung function (n = 6) were stained with alcian blue, periodic acid-Schiff (PAS) and by immunohistochemistry of mucins (MUC): MUC2, MUC4, MUC5AC, MUC5B and MUC6. Histochemical staining and immunoreactivity of bronchiolar epithelium were graded and the presence or absence of stained mucus in the bronchiolar lumen was evaluated. There were no differences in alcian blue and PAS epithelial staining between the three groups. Intraluminal PAS staining was significantly more frequent among COPD subjects (P < 0.05). The expression of MUC5AC was significantly higher in the bronchiolar epithelium of patients with COPD (P < 0.05). Within the bronchiolar lumen, the predominant mucin was MUC5B. Intraluminal MUC5B was significantly more frequent among COPD patients (P < 0.05). CONCLUSIONS: COPD is specifically associated with increased expression of MUC5B in the bronchiolar lumen and of the mucin MUC5AC in the bronchiolar epithelium. These changes in mucin production in the peripheral airways may contribute to the pathophysiology of COPD.  相似文献   
997.
To assess whether the free-to-total prostate specific antigen (PSA) ratio (F/T PSA ratio) would enhance prostate cancer detection in Korean men with serum total PSA levels between 4 and 20 ng/ml. Methods: A total of 240 consecutive patients whose serum PSA levels were between 4 and 20 ng/ml were enrolled in this two-year study. All patients underwent ultrasound-guided transrectal biopsies of the prostate gland. The F/T PSA ratio was measured using the Roche immunoassay. Results: Of the 240 patients, 202 (84%) had benign histologies, while 38 (16%) had prostate cancer. The two patient groups were well matched for age. The mean F/T PSA ratio showed a statistically significant difference between the two groups: in the benign histology group it was 0.14 (0.04 - 0.37), and 0.10 (0.08 - 0.20) in the prostate cancer group (p < 0.05). Out of the 183 patients with a PSA level between 4-10 ng/ml, the mean F/T PSA ratios were 0.14 and 0.11 in the benign histology (n=158) and prostate cancer groups (n=25), respectively (p < 0.05). From the 57 patients with a PSA level between 10 - 20 ng/ml, the mean F/T PSA ratios were 0.14 and 0.10 in the benign histology (n=44) and prostate cancer groups (n=13), respectively (p < 0.05). Overall, when the cut-off value of the F/T PSA ratio was 0.10, the sensitivity and specificity were 75.0% and 76.5%, while for the cut-off value of 0.15 they were 83.3% and 39.7% respectively. Conclusion: Our data demonstrated the usefulness of the free to total PSA ratio in distinguishing benign prostate disease and cancer disease, hence eliminating unnecessary biopsies. It is recommended that a cut-off value for the F/T PSA ratio of 0.10 be applied to Korean men which this is lower than the value used in Western countries.  相似文献   
998.

Background

With the rapid advance of genetics, the application of genetic testing has become increasingly popular. Test results have had a tremendous impact on individuals who receive the test and his or her family. The ethical, legal, and social implications (ELSI) of genetic testing cannot be overlooked. The Internet is a potential tool for public engagement.

Objectives

This study aimed at establishing ethical guidelines for genetic testing in Taiwan through a participatory citizen consensus approach via the Internet.

Methods

The research method used was a citizen consensus conference modified by an Internet application and the Delphi technique. The citizen consensus conference is one of the public participation mechanisms. The draft ethical guidelines for genetic testing were written by an expert panel of 10. The Delphi technique was applied to a citizen panel recruited via the Internet until a consensus was reached. Our research population was restricted to people who had Internet access.

Results

Included in the citizen panel were 100 individuals. A total of 3 individuals dropped out of the process. The citizen panel was exposed to the issues through Internet learning and sharing. In all, 3 rounds of anonymous questionnaires were administered before a consensus was reached in terms of importance and feasibility. The result was ethical guidelines composed of 4 categories and 25 items. The 4 categories encompassed decision making (6 items), management of tissue samples (5 items), release of results (8 items), and information flow (6 items). On a scale of 1 to 10, the average (SD) importance score for the decision-making category was 9.41 (SD 0.58); for the management of tissue samples category, the average score was 9.62 (SD 0.49); for the release of results category, the average score was 9.34 (SD= 0.59); and for the information flow category, the average score was 9.6 (SD = 0.43). Exploratory analyses indicated that participants with higher education tended to attribute more importance to these guidelines.

Conclusions

The resulting recommended ethical guidelines had 4 categories and 25 items. We hope through the implementation of these guidelines that mutual trust can be established between health care profession and the general public with respect to genetic tests.  相似文献   
999.
Epidemiologic data on the etiologic organisms is important for appropriate empirical antibiotic treatment of bacterial meningitis. We identified the etiologies of community-acquired bacterial meningitis in Korean adults and the associated epidemiological factors. A retrospective, multicenter nationwide study was carried out. Patients 18 years of age or older with community-acquired bacterial meningitis with a confirmed pathogen were enrolled. Demographic, clinical, and microbiological data were collected. One hundred and ninety-five cases were collected. Streptococcus pneumoniae was the most common pathogen (50.8%), followed by Staphylococcus aureus (10.3%), Klebsiella pneumoniae (7.7%), Listeria monocytogenes (6.7%), and group B Streptococcus (3.1%). The penicillin resistance rate of the S. pneumoniae was 60.3%; 40.0% of the organisms were not susceptible to third-generation cephalosporins. The combination of third-generation cephalosporin with vancomycin was used in 76.3% of cases. Steroids were given before or with the first dose of antibiotics in 37.4% of patients. The 30-day mortality rate was 20.5% and neurological sequelae developed in 15.6% of cases. S. pneumoniae was the most common organism identified in community-acquired bacterial meningitis among Korean adults. S. aureus, K. pneumoniae, L. monocytogenes, and group B Streptococcus were also common. S. pneumoniae had high rates of resistance to penicillin and third-generation cephalosporins.  相似文献   
1000.
Emergency surgical repair for acute traumatic aortic ruptures has been associated with a high peri-procedural mortality rate. Endovascular stent-grafting, as a less invasive procedure, has shown encouraging results. This report describes a patient with a short landing zone, who was treated by transposing the supra-aortic branch without sternotomy, followed by covered stent-grafting with an extended proximal bare portion to enhance fixation.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号