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   2718篇
  免费   229篇
  国内免费   77篇
耳鼻咽喉   36篇
儿科学   82篇
妇产科学   74篇
基础医学   478篇
口腔科学   95篇
临床医学   225篇
内科学   547篇
皮肤病学   35篇
神经病学   220篇
特种医学   131篇
外科学   276篇
综合类   31篇
一般理论   1篇
预防医学   239篇
眼科学   77篇
药学   257篇
中国医学   42篇
肿瘤学   178篇
  2023年   22篇
  2022年   43篇
  2021年   92篇
  2020年   60篇
  2019年   75篇
  2018年   95篇
  2017年   65篇
  2016年   72篇
  2015年   66篇
  2014年   104篇
  2013年   106篇
  2012年   159篇
  2011年   146篇
  2010年   89篇
  2009年   90篇
  2008年   120篇
  2007年   172篇
  2006年   127篇
  2005年   124篇
  2004年   107篇
  2003年   114篇
  2002年   86篇
  2001年   69篇
  2000年   87篇
  1999年   97篇
  1998年   39篇
  1997年   32篇
  1996年   35篇
  1995年   25篇
  1994年   19篇
  1993年   20篇
  1992年   44篇
  1991年   42篇
  1990年   39篇
  1989年   52篇
  1988年   40篇
  1987年   29篇
  1986年   28篇
  1985年   17篇
  1984年   23篇
  1983年   19篇
  1977年   10篇
  1975年   8篇
  1974年   8篇
  1973年   10篇
  1971年   9篇
  1970年   11篇
  1969年   11篇
  1966年   10篇
  1965年   8篇
排序方式: 共有3024条查询结果,搜索用时 0 毫秒
1.
2.
Summary BACKGROUND: Endometriosis is a relatively common pathology in women of childbearing age and of low parity but rarely shows extraperitoneal involvement. The main aim of this paper is to raise the attention of specialists to the necessity of carrying out penetrating diagnosis of nonspecific extraperitoneal masses occurring in women of reproductive age. METHODS: We performed a retrospective review of six patients diagnosed with extraperitoneal endometriosis who were treated at the Vega Baja University Hospital (Spain) during the last 5 years. RESULTS: Surgical treatment had positive results in five patients. The preoperative diagnosis was correctly made in only two patients. The accurate aetiology of endometriosis remains unknown and diagnosis is based on clinical and cytopathological findings. CONCLUSIONS: Surgical treatment of extraperitoneal endometriosis is recommended. However, postoperative follow-up is obligatory and hormonal suppressive therapy may be necessary. Medical treatment with gestagens, Danazol, or agonists of the gonadotropin-releasing hormone are ineffective in endometriomas which are bigger than 2 cm.   相似文献   
3.
硫酸多糖对体外人脐静脉内皮细胞损伤的保护作用   总被引:8,自引:1,他引:7  
研究表明,硫酸多糖体外对多聚阳离子和氧自由基损伤的人脐静脉内皮细胞有保护作用。肝素、硫酸软骨素A抗多聚阳离子损伤作用比同浓度低分子肝素和甘糖酯强。肝素、硫酸软骨素A、甘糖酯抗氧自由基损伤作用优于同浓度低分子肝素。结果显示硫酸多糖有保护血管内皮的作用,其作用可能与所带阴离子基团有关。  相似文献   
4.
The lectin-binding properties of 44 cases of serous and mucinous ovarian cystadenoma, tumor of low malignant potential (LMP), and invasive carcinoma were examined histochemically. Wheat germ agglutinin (WGA), concanavalin A (con A), Ulex europaeus agglutinin I (UEA-I), peanut agglutinin (PNA), Ricinus communis agglutinin I (RCA-I), soybean agglutinin (SBA), and Robina pseudoaccacia (RPA) were employed. All the lectins examined were bound to neoplastic epithelial cells of benign and malignant tumors, but none bound exclusively to ovarian tumor cells. Different lectin-binding patterns between serous and mucinous neoplasms were observed, with the exception of RPA. UEA-I, con A, RPA, and PNA in serous neoplasms and UEA-I, RPA, and WGA in mucinous neoplasms demonstrated lectin-binding properties of LMP tumors intermediate between those of cystadenoma and invasive carcinoma. These findings indicate that serous and mucinous ovarian neoplasms contain different glycoconjugates, that malignant transformation of the neoplasms is associated with alteration of these glycoconjugates, and especially that LMP tumors have a different composition of cellular glycoconjugates from that of invasive ovarian carcinoma.  相似文献   
5.
We report the generation of murine triomas by fusing splenocytes from mice previously immunized with HBsAg ay-subtype and a hybridoma, secreting anti-HBsAg ad-subtype monoclonal antibody, which was rendered HGPRT- by induced mutagenesis with N-methyl-N'nitro-N-nitrosoguanidine. The fusion yielded a 83.8% of hybrids showing the antigen specificity of the parental hybridoma and a 16.1% of bi-specific monoclonal antibodies. One of them, coded as 1C8A5, showing a heavy chain isotype (IgG1/IgG2b) was used as capture reagent in an ultramicro-ELISA. As little as 0.78 I.U. of both HBsAg ad- and ay-subtypes could be realiably detected.  相似文献   
6.
Introduction : Hypertrophic scar is a devastating sequel to burns and other tangential skin injuries. It follows deep dermal injuries and does not occur after superficial injuries. Nitric oxide (NO) plays many important roles in wound healing from inflammation to scar remodeling. Studies have shown that expression of nitric oxide synthase and nitric oxide production are decreased in human hypertrophic scar. However little is known about NO involvement in the early stages of hypertrophic scarring, because of the lack of an animal model. It was recently reported that the female red Duroc pig (FRDP) makes thick scar, which is similar to human hypertrophic scar. We hypothesized that NO production in wounds on the female, red Duroc pig is similar to that of human hypertrophic scar and that NO involvement in deep wounds is different from that in superficial wounds. Methods : Superficial (0.015” to 0.030”) and deep (0.045” to 0.060”) wounds were created on the backs of four FRDPs. Biopsies were collected at weeks 1.5, 4, 8 and 21 post wounding including samples of uninjured skin. Nitric oxide levels were measured with the Griess reaction assay and normalized with tissue protein level. Results : Superficial wounds healed with an invisible scar whereas the deep wounds healed with scar resembling mild hypertrophic scar. The thickness of the scars from the deep wounds was significantly greater than uninjured skin and healed superficial wounds (p < 0.01). NO levels were increased at 1.5 weeks in deep wounds compared to superficial wounds and uninjured skin (p < 0.05). At 8 weeks, NO levels in deep wounds had returned to the level of uninjured tissue and superficial wounds. By 21 weeks, NO levels had decreased significantly when compared to superficial wounds (p < 0.01). There were no differences in NO levels between uninjured skin and superficial wounds at any time point (p > 0.05). Conclusions : NO production is similar in late, deep wounds on the female, red Duroc pig to that reported in the literature for human hypertrophic scar further validating this animal model. NO production is quite different after deep wounds as compared to superficial wounds in the FRDP. Early elevation in nitric oxide production might account for excessive inflammation in deep wounds that become thick scars in the FRDP. Nitric oxide regulators and effects at early stages of scar formation should be elucidated further and the FRDP appears to be a useful model.  相似文献   
7.
Using an intracellular cytokine assay, we recently showed that the frequencies of rotavirus (RV)-specific CD4(+) and CD8(+) T cells secreting INFgamma, circulating in RV infected and healthy adults, are very low compared to the frequencies of circulating cytomegalovirus (CMV) reactive T cells in comparable individuals. In children with acute RV infection, these T cells were barely or not detectable. In the present study, an ELISPOT assay enabled detection of circulating RV-specific INFgamma-secreting cells in children with RV diarrhea but not in children with non-RV diarrhea without evidence of a previous RV infection. Using microbead-enriched CD4(+) and CD8(+) T cell subsets, IFNgamma-secreting RV-specific CD8(+) but not CD4(+) T cells were detected in recently infected children. Using the same approach, both CD4(+) and CD8(+) RV-specific T cells were detected in healthy adults. Furthermore, stimulation of purified subsets of PBMC that express lymphocyte homing receptors demonstrated that RV-specific INFgamma-secreting CD4(+) T cells from adult volunteers preferentially express the intestinal homing receptor alpha4beta7, but not the peripheral lymph node homing receptor L-selectin. In contrast, CMV-specific INFgamma-secreting CD4(+) T cells preferentially express L-selectin but not alpha4beta7. These results suggest that the expression of homing receptors on virus-specific T cells depends on the organ where these cells were originally stimulated and that their capacity to secrete INFgamma is independent of the expression of these homing receptors.  相似文献   
8.
Hepatitis C virus (HCV) has high genomic variability and at least six different types have been reported. The genotypes distribution is currently unknown among HCV strains circulating in Central America. In order to study the degree of genetic variability of strains isolated in Costa Rica, sequence data obtained from the 5' non coding region from 7 patients from Costa Rica were compared with published sequences from 57 strains of all types. The phylogenetic analysis revealed the existence of type 1 strains of a novel genetic lineage, recently described for some South American countries, and indicates an increasing diversification of HCV.  相似文献   
9.
We used the species specificity and repetitious nature of subtelomeric kinetoplastida sequences to generate a duplex PCR assay for the simultaneous detection of Trypanosoma cruzi and Trypanosoma rangeli in experimentally and naturally infected triatomine (Reduviid) bugs and in infected human subjects. The assay was species specific and was capable of detecting 1/20th of T. cruzi and 1/4th of T. rangeli cell equivalents without complementary hybridization. In addition, the PCR-based assay was robust enough for direct application to difficult biological samples such as Reduviid feces or guts and was capable of recognizing all T. cruzi and T. rangeli strains and lineages. Because the assay primers amplify entirely different target sequences, no reaction interference was observed, facilitating future adaptation of this assay to an automated format.  相似文献   
10.
ABSTRACT: Pemphigus vulgaris (PV) is an autoimmune disease of the skin and mucous membranes characterized by an autoantibody response against an epidermal cadherin. We performed high resolution HLA class II typing in 19 patients with PV from Rawalpindi, Pakistan and 19 non-Jewish European PV patients from Boston by sequence-specific oligonucleotide probe hybridization. The results were compared with two separate ethnically matched control populations. We found that PV patients from Pakistan had significantly increased frequencies of DRB1*1404 ( p = 0.01), DQA1*0101 ( p = 0.02), and DQB1*0503 ( p = 0.01). Among the patients of non-Jewish European ancestry, DRB1*1401 ( p < 10−6), DQA1*0101 ( p < 10−5) and DQB1*0503 ( p < 10−6), were increased in PV patients. Formal linkage analysis between the major histocompatibility complex and the PV antibody was performed in 67 relatives of the 19 Pakistani patients. The results showed strong evidence for linkage of HLA-DRB1*1404, DQA1*0101, DQB1*0503, with the presence of PV antibody in relatives’ families with a significant logarithm of the odds score of 6.06. Based on the three dimensional structure of class II molecules, we propose that HLA-DQA1*0101 and DQB1*0503, encode a negatively charged P9 peptide binding pocket of the DQ molecule and are significantly associated with susceptibility to PV in non-Jewish populations.  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