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   3364篇
  免费   159篇
  国内免费   19篇
耳鼻咽喉   31篇
儿科学   71篇
妇产科学   43篇
基础医学   319篇
口腔科学   129篇
临床医学   183篇
内科学   1152篇
皮肤病学   74篇
神经病学   187篇
特种医学   194篇
外科学   474篇
综合类   12篇
一般理论   1篇
预防医学   80篇
眼科学   34篇
药学   202篇
中国医学   5篇
肿瘤学   351篇
  2024年   2篇
  2023年   19篇
  2022年   60篇
  2021年   145篇
  2020年   62篇
  2019年   84篇
  2018年   98篇
  2017年   75篇
  2016年   93篇
  2015年   87篇
  2014年   94篇
  2013年   156篇
  2012年   232篇
  2011年   231篇
  2010年   113篇
  2009年   114篇
  2008年   206篇
  2007年   226篇
  2006年   219篇
  2005年   223篇
  2004年   220篇
  2003年   204篇
  2002年   207篇
  2001年   28篇
  2000年   32篇
  1999年   24篇
  1998年   32篇
  1997年   36篇
  1996年   36篇
  1995年   16篇
  1994年   21篇
  1993年   11篇
  1992年   6篇
  1991年   12篇
  1990年   11篇
  1989年   13篇
  1988年   12篇
  1987年   9篇
  1986年   8篇
  1985年   6篇
  1984年   8篇
  1983年   11篇
  1982年   8篇
  1981年   5篇
  1980年   10篇
  1979年   2篇
  1978年   2篇
  1977年   2篇
  1975年   3篇
  1959年   1篇
排序方式: 共有3542条查询结果,搜索用时 46 毫秒
991.
BACKGROUND: Fractalkine is a relatively newly discovered CX(3)C chemokine, which is a chemoattractant for T cells, monocytes and natural killer cells. Several reports have demonstrated the association between chemokine levels in seminal plasma and semen quality. The fractalkine levels in ejaculates from normal donors and infertile male patients with or without asthenozoospermia, were examined and correlated with sperm motility and morphology. METHODS AND RESULTS: Western blot analysis showed fractalkine protein to be present in the seminal plasma. Fractalkine titres in the seminal plasma of infertile men with asthenozoospermia (0.64 +/- 0.04 microg/ml; n = 58) were lower than those in patients without asthenozoospermia (0.94 +/- 0.10 microg/ml; n = 22, P < 0.01) and fertile donors (1.04 +/- 0.07 microg/ml; n = 10, P < 0.001). There was no significant difference between fractalkine levels in patients with and without leukospermia. No significant correlation was found between fractalkine and interleukin-8 levels in seminal plasma. Sperm motility was positively correlated (R(2) = 0.14, P < 0.001) with fractalkine concentration. The existence of CX(3)CR-positive leukocytes in semen was confirmed using specific primers for CX(3)CR. CONCLUSIONS: These results suggest that fractalkine is a chemokine associated with sperm motility and the migration of CX(3)CR-positive leukocytes into semen.  相似文献   
992.
Atopic dermatitis (AD) is a common inflammatory skin disease. In AD, cytokines such as interleukin (IL)-4 or interferon (IFN)-gamma are considered to affect the disease status. Recently, human V alpha 24(+) natural killer T (NKT) cells have been found to produce large amounts of IL-4 and IFN-gamma. Thus there is a possibility that the proportion of V alpha 24(+) NKT cells modifies the AD status. In this study, we examine the proportion of the V alpha 24(+)/V beta 11(+) cells that composes the V alpha 24(+) NKT cells in peripheral blood mononuclear cells (PBMCs) from 71 healthy donors (HDs) and 31 AD patients. Because CD4(-) and CD4(+) NKT subsets show different cytokine production patterns concerning IL-4, these two subsets are evaluated. Our results have shown that the proportion of the V alpha 24(+) NKT cells is markedly reduced in AD patients. In addition, the CD4(-) V alpha 24(+) NKT subset has a tendency to be more reduced than the CD4(+) V alpha 24(+) NKT subset. Moreover, the proportion of CD4(-) V alpha 24(+) NKT(+) cells and Th2 deviation of Th1/Th2 balance is inversely correlated. These observations may contribute to the understanding of the mechanism involved in AD.  相似文献   
993.
To identify semen in forensic samples, we developed an analytical system for one-step immunoassay that has been constructed using the concept of immunochromatography and can identify semenogelin (Sg), which originates in the seminal vesicles. The system employed monoclonal antibody (mAb) and polyclonal antibody (pAb) against recombinant Sg-II (63 kDa), which has been synthesized in insect cells using baculovirus. The two antibodies bound with the seminal plasma motility inhibitor (SPMI; 14 kDa) as a final fragment peptide of Sg. The test stick is based on the sandwich technique using the above antibodies. When serial dilutions of seminal plasma were analyzed using this test stick, the intensity of a clear immunoreactive signal peaked at 2000-fold dilution. Thereafter, the signals decreased slowly but still persisted up to 400,000-fold dilution. The Sg antigen was undetectable in saliva, urine, breast milk, serum or vaginal secretions. Also, the test stick shown did not react with animal semen samples, such as those from horses, dogs, swine and bulls. When semen samples, diluted 100,000-fold from 100 men were tested, the Sg antigenic activity was detectable in all samples. In addition, the specificity and sensitivity of the test stick for identification of semen were demonstrated by comparative forensic studies. We conclude that this immunoassay method is a useful confirmatory test for the identification of semen. The immunochromatographic system for forensic testing or research use will become available commercially soon.  相似文献   
994.
To investigate clinical characteristics of early central nervous system (CNS) complications after reduced-intensity stem cell transplantation (RIST), we reviewed the medical records of 232 patients who had undergone RIST for hematologic diseases at our institutions between September 1999 and June 2003. All patients had received purine analog-based preparative regimens. Stem cell sources comprised granulocyte colony-stimulating factor-mobilized blood from HLA-identical or 1 locus-mismatched related donors (n = 151), unrelated bone marrow (n = 44), or unrelated cord blood (n = 37). Graft-versus-host disease prophylaxis incorporated cyclosporine with or without methotrexate. Diagnosis of CNS complications was based on clinical, radiologic, and microbiological findings. CNS complications occurred in 18 patients (7.8%), with a median onset of 22 days, and were infectious (n = 1), metabolic (n = 15), or cerebrovascular (n = 2). Symptoms included seizures (n = 7), visual disturbance (n = 2), headache (n = 8), nausea (n = 8), vomiting (n = 6), impaired consciousness (n = 16), and hemiparesis (n = 3). Complications improved promptly in 10 patients, and 8 patients died without improvement within 30 days. Multivariate analysis with logistic regression identified umbilical cord blood transplantation as a significant risk factor for early CNS complications (odds ratio, 14.5; 95% confidence interval, 3.7-56.9; P <.0001). CNS complications are a significant problem after RIST, particularly with umbilical cord blood. Limbic encephalopathy is an unrecognized subtype of neurotoxicity after umbilical cord blood transplantation.  相似文献   
995.
A case of neuroendocrine lung tumor located beneath the pleura in a 71 year old woman is reported. At autopsy, the tumor was found to have metastasized to the bones and liver without involving the hilar lymph nodes. Histological-ly, the tumor cells at the primary site and in the liver metastasis exhibited a carcinoid-like organoid structure, whereas pleomorphic giant cells were noted in the bone metastasis. The argyrophilic tumor cells were immuno-reactive for neuron specific enolase, chromogranin A, serotonin, calcitonin, calcitonin gene-related peptide, gas-trin-releasing peptide, neuropeptide Y, gastrin, pancreatic polypeptide, glicentin, the alpha subunit of human cho-rionic gonadotropin, keratin, epithelial membrane antigen, Leu M1 and carcinoembryonic antigen. Electron microscopy revealed abundant neurosecretory granules in the cytoplasm. This was considered to be a rare case of neuroendocrine lung tumor showing carcinoid like histology at the primary site and large-cell transformation in bone metastasis.  相似文献   
996.
997.
Although many cases of sarcoidosis are self-limiting with spontaneous remission, uncontrolled pulmonary granulomatosis with fibrosis produces intolerable long-term respiratory symptoms in a minority of patients. Individuals with chronic pulmonary sarcoidosis require an alternative therapy to corticosteroidal treatment because of its insufficient effectiveness. Although many researchers have considered infection as the triggering factor for this disease, the mechanisms by which the candidate causative organisms induce this disorder remain unclear. We report here that extrapulmonary sensitization to Propionibacterium acnes, which is one of the candidates to date, induced pulmonary Th-1 granulomas mainly in the subpleural and peribronchovascular regions often observed in sarcoidosis. These granulomas appear to be caused by indigenous P. acnes pre-existing in the lower respiratory tract of the normal lung, which is believed to be germ-free, and by an influx of P. acnes-sensitized CD4(+) T cells from the circulation. Importantly, the eradication of indigenous P. acnes with antibiotics alleviated the granulomatous lung disease. This is the first report to present clear evidence of the contribution of an indigenous pulmonary bacterium to the formation of granulomatous lesions in the lung. We propose that treatment targeting indigenous P. acnes in the lung may be a possible remedy for pulmonary sarcoidosis.  相似文献   
998.
Nonspecific immunoglobulin E (IgE) production is an event characteristically observed in parasitic helminth infections, but its mechanisms are still unclear. To define these mechanisms, we prepared a recombinant Dirofilaria immitis protein (rDiAg) and assessed its effect on nonspecific IgE production. rDiAg preferentially induced nonspecific IgE production, without eliciting specific IgE production, as well as a Th2-type cytokine profile (high interleukin-4 [IL-4] and IL-10 production but low gamma interferon production) in BALB/c mice. rDiAg significantly elicited the proliferative response of naive B cells. This response was not abolished by polymyxin B, an inhibitor of lipopolysaccharide (LPS), and rDiAg normally expanded splenic B cells from LPS nonresponder C3H/HeJ mice. Thus, the mitogenic effect of rDiAg was not due to LPS contamination. rDiAg also enhanced levels of CD23 expression on splenic B cells. Splenic B cells produced marked levels of IgE when cultured with the combination of rDiAg and IL-4 (rDiAg-IL-4), whereas peritoneal B cells produced negligible levels of IgE. rDiAg-IL-4-induced IgE production by splenic B cells was synergistically increased by coculture with peritoneal B cells. rDiAg-driven IL-10 secretion was higher in peritoneal B cells than in splenic B cells. IgE production by splenic B cells cocultured with peritoneal B cells was decreased to a level comparable to that by splenic B cells in the presence of a neutralizing anti-IL-10 monoclonal antibody. Collectively, these results suggest that rDiAg-induced polyclonal expansion and IgE class switching of splenic B cells contribute to nonspecific IgE production and that these responses are enhanced by peritoneal B-cell-derived IL-10.  相似文献   
999.
The genomes of 28 bacterial strains, including mycobacterial species Mycobacterium tuberculosis and Mycobacterium bovis, were analyzed for the presence of a special class of microsatellite, that of trinucleotide repeat sequences (TRS). Results of a search of all 10 possible TRS motifs (i.e., CCT, CGG, CTG, GAA, GAT, GTA, GTC, GTG, GTT, and TAT) with five or more repeating units showed that (CGG)(5) was highly represented within the genomic DNA of M. tuberculosis and M. bovis. Most of the (CGG)(5) repeats in the genome were within the open reading frames of two large gene families encoding PE_PGRS and PPE proteins that have the motifs Pro-Glu (PE) and Pro-Pro-Glu (PPE). (CGG)(5)-probed Southern hybridization showed that some mycobacterial species, such as Mycobacterium marinum, Mycobacterium kansasii, and Mycobacterium szulgai, possess many copies of (CGG)(5) in their genomes. Analysis of clinical isolates obtained from Tokyo and Warsaw with both IS6110 and (CGG)(5) probes showed that there is an association between the fingerprinting patterns and the geographic origin of the isolates and that (CGG)(5) fingerprinting patterns were relatively more stable than IS6110 patterns. The (CGG)(5) repeat is a unique sequence for some mycobacterial species, and (CGG)(5) fingerprinting can be used as an epidemiologic method for these species as well as IS6110 fingerprinting can. If these two fingerprinting methods are used together, the precise analysis of M. tuberculosis isolates will be accomplished. (CGG)(5)-based fingerprinting is particularly useful for M. tuberculosis isolates with few or no insertion elements and for the identification of other mycobacterial species when informative probes are lacking.  相似文献   
1000.
BACKGROUND: The biological functions of basophils are precisely regulated by various cytokines in vitro, but little is known about surface markers that are upregulated during the cytokine-mediated activation process. OBJECTIVE: It has been well established that CD69, CD44, and CD54 represent "activation markers" for cytokine-mediated eosinophil activation. The objective of this study was to elucidate the expression and regulation of these molecules in human basophils in vitro as well as in vivo. METHODS: Basophils were purified from venous blood by means of density gradient centrifugation followed by negative selection. Surface expression was analyzed by means of flow cytometry. We also studied the expression of CD69, CD44, and CD54 on basophils in bronchoalveolar lavage fluid and blood specimens from patients with asthma. RESULTS: CD44 and CD54 were constitutively expressed on basophils and moderately upregulated by IL-3. On the other hand, CD69 expression was only weakly observed in freshly isolated basophils, but IL-3 induced extremely high levels of expression. Surface CD69 appeared rather slowly in comparison with CD63 and CD11b, and the induction of expression was completed within 24 hours. Basophil CD69 had no functional relevance, but it did have biological relevance. Whole blood basophils from asthmatic individuals expressed significantly higher levels of CD69 than did those from normal individuals. Furthermore, bronchoalveolar lavage fluid basophils showed higher levels of CD69 expression than did blood basophils from the same donors. CONCLUSION: CD69 expression on basophils was preferentially and strongly upregulated by IL-3. CD69 on basophils might be useful as an in vitro as well as in vivo marker of activation of these cells by IL-3.  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