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   6392篇
  免费   338篇
  国内免费   25篇
耳鼻咽喉   64篇
儿科学   83篇
妇产科学   80篇
基础医学   930篇
口腔科学   193篇
临床医学   398篇
内科学   1576篇
皮肤病学   56篇
神经病学   473篇
特种医学   328篇
外科学   677篇
综合类   25篇
预防医学   237篇
眼科学   264篇
药学   568篇
中国医学   15篇
肿瘤学   788篇
  2023年   20篇
  2022年   60篇
  2021年   103篇
  2020年   44篇
  2019年   54篇
  2018年   64篇
  2017年   59篇
  2016年   78篇
  2015年   85篇
  2014年   135篇
  2013年   181篇
  2012年   267篇
  2011年   276篇
  2010年   171篇
  2009年   140篇
  2008年   311篇
  2007年   314篇
  2006年   308篇
  2005年   284篇
  2004年   305篇
  2003年   286篇
  2002年   309篇
  2001年   263篇
  2000年   285篇
  1999年   251篇
  1998年   99篇
  1997年   81篇
  1996年   76篇
  1995年   62篇
  1994年   55篇
  1993年   54篇
  1992年   155篇
  1991年   194篇
  1990年   182篇
  1989年   167篇
  1988年   157篇
  1987年   139篇
  1986年   133篇
  1985年   102篇
  1984年   82篇
  1983年   49篇
  1982年   36篇
  1981年   27篇
  1980年   16篇
  1979年   53篇
  1978年   43篇
  1977年   32篇
  1976年   24篇
  1975年   11篇
  1966年   8篇
排序方式: 共有6755条查询结果,搜索用时 15 毫秒
51.
52.
Polyglutamine (polyQ) diseases are a growing class of inherited neurodegenerative diseases including Huntington's disease, which are caused by abnormal expansions of the polyQ stretch in each unrelated disease protein. The expanded polyQ stretch is thought to confer toxic properties on the disease proteins through alteration of their conformation leading to pathogenic protein-protein interactions including oligomerization and/or aggregation. Hypothesizing that molecules with selective binding affinity to the expanded polyQ stretch may interfere with the pathogenic properties, we previously identified Polyglutamine Binding Peptide 1 (QBP1) from combinatorial peptide phage display libraries. We show here that a tandem repeat of the inhibitor peptide QBP1, (QBP1)(2), significantly suppresses polyQ aggregation and polyQ-induced neurodegeneration in the compound eye of Drosophila polyQ disease models, which express the expanded polyQ protein under the eye specific promoter. Most importantly, (QBP1)(2) expression dramatically rescues premature death of flies expressing the expanded polyQ protein in the nervous system, resulting in the dramatic increase of the median life span from 5.5 to 52 days. These results suggest that QBP1 can prevent polyQ-induced neurodegeneration in vivo. We propose that QBP1 prevents polyQ oligomerization and/or aggregation either by altering the toxic conformation of the expanded polyQ stretch, or by simply competing with the expanded polyQ stretches for binding to other expanded polyQ proteins. The peptide inhibitor QBP1 is a promising candidate with great potential as a therapeutic molecule against the currently untreatable polyQ diseases.  相似文献   
53.
Nakamura M  Terada M  Sasaki H  Kamada M  Ohno T 《Hybridoma》2000,19(6):427-434
Antibody humanization by transplanting the complimentarity determining region (CDR) to a human framework aims to reduce the response of the human immune system against a foreign molecule during passive immunization. We transferred the CDR from the murine monoclonal antibody (MAb) NM-01 to a human IgG frame. The humanized NM-01 (hNM-01) recognizes the same epitope on Human Immunodeficiency Virus type 1 (HIV-1) envelope as its murine progenitor, but with greater efficiency, and shows enhanced neutralization of HIV-1. We have shown that this increase in reactivity may be attributed to residue 4 of the humanized kappa chain, where the presence of a methionine residue rather than the murine leucine appears to promote a more advantageous conformation of the antigen-binding site, perhaps via packing interactions with the V(kappa) CDR1. The capacity of humanized NM-01 to neutralize direct clinical isolates was also examined with the expectation that hNM-01 will prove suitable for development as a therapeutic agent. This reshaped antibody reacted with several clinical isolates of HIV-1 tested. Moreover, we proved the ability of this antibody of its activation of complement by flow cytometry and electron microscopy analysis. Although hNM-01 alone was capable of neutralizing HIV-1, the presence of complement enhanced neutralization. The enhancement of complement activation was also observed in hNM-01 than murine progenitor. This finding supports a potential role for antibody-dependent complement-mediated virolysis and more effective neutralization in HIV-1 therapy.  相似文献   
54.
Laminin is a high molecular weight glycoprotein found in all basement membranes studied to date. Two subunits of laminin, A and B, have been isolated and characterized from a variety of tumor matrices. Recently we have reported the finding, in human placenta, of a new laminin subunit which we termed M. In the present study we report on the presence of laminin M in placentae of other species such as bovine, rat and mouse. In addition, we have examined laminin extracted from mouse EHS-tumor, rat ED-PYS carcinoma and three human carcinoma cell lines. The laminin subunits were detected by the electroimmunoblot technique using antibodies against mouse, rat and human laminin. Laminin M could not be demonstrated either in the two murine tumors, or in the three different human neoplastic cell lines studied. If the absence of laminin M is the consequence of neoplastic transformation, then studies of the metabolism of this subunit may provide new information on neoplastic transformation and invasion, and a useful marker in tumor diagnosis.  相似文献   
55.
A phase I study ofN 4-behenoyl-1-β-d-arabinofuranosylcytosine (BHAC) was conducted in 66 patients, 41 with solid tumors and 25 with hematological malignancies. The patients received either a 2-h single intravenous (i.v.) drip infusion (Schedule 1) or consecutive daily 2-h i.v. infusions (Schedule 2). In Schedule 1 the daily dose was initiated with 1.5 mg kg?1 which was escalated up to 7 mg kg?1. Side-effects were mild, and included nausea, vomiting, epilation, and hot flushes. Because of the presence of the solvent vehicle, HCO-60 and in consideration of the mechanism of action of BHAC, the dose escalation was stopped at 7 mg kg?1. In Schedule 2, the daily dose was started with 1.5 mg kg?1 which was escalated up to 8 mg kg?1 and given for 2–16 days. Myelosuppression was found to be dose-limiting toxicity. The maximum tolerated dose (MTD) in patients with non-hematological solid tumors was assumed to be 5 mg kg?1 daily × 5 days. The plasma disappearance curve of BHAC looked biphasic, and when 4 mg kg?1 of BHAC were administered the half-lives of the initial phase (t 1/2α) and the second phase (t 1/2β) were calculated as 0.798 and 5.76 h respectively. In Schedule 2 complete remission was observed in 5 out of 21 patients with acute leukemia, one partial remission in Hodgkin’s disease, and one 1-B response (Karnofsky) in thyroid papillary adenocarcinoma.  相似文献   
56.
In order to explore the effects of metals upon the subsequent onset of several clinical events in SMON, a retrospective cohort study was attempted. Study subjects were 216 "exposed" patients and 149 "unexposed" patients. "Exposure" was defined as the simultaneous ingestion of metal-containing drugs with clioquinol before the onset of neurological disorders. These two cohorts were identified from 531 patients among 832 patients, collected by the nationwide survey in 1975 and 1976. Effects provoked by ingestion of five metals (alminum, calcium, magnesium, copper and bismuth) were evaluated by relative risks with and without adjustment of the total amount of clioquinol ingested. Adjusted relative risks were estimated by maximum likelihood method. Significance of relative risk was determined by its 95% confidence interval. Following major findings emerged from the present analysis. (1) Simultaneous ingestion of Al-, Ca-, Mg-, Cu- or Bi-containing drugs with clioquinol significantly reduced the risk of developing motor disturbances. (2) Risk of developing visual disturbances were favorably modified by Al-containing drugs. (3) Clinical severity was significantly reduced by ingestion of Al-, Ca-, Mg- or Bi-containing drugs. (4) About 2-fold increase in risk of unfavorable clinical course was demonstrated by Al-containing drugs. (5) Onset of both green-fur on the tongue and relapse appeared unrelated to the metal-containing drugs ingested. (6) Combined ingestion of two kinds of metal-containing drugs with clioquinol appeared to yield more favorable effects than single ingestion of metal-containing drugs. (7) Al- or Bi-containing drugs demonstrated the strongest association with clinical features of SMON, followed by the drugs containing Mg or Ca. Cu-containing drugs had little association.  相似文献   
57.
The aim of this research was to reveal the characteristics of gut microbiome altered by acarbose intervention in Japanese patients with type 2 diabetes (T2D) and its possible association with habitual dietary intake. Eighteen patients with T2D were administered acarbose for four weeks. The abundances of two major phyla, namely Actinobacteria and Bacteroidetes, were reciprocally changed accompanied by the acarbose intervention. There were also significant changes in the abundances of ten genera, including the greater abundance of Bifidobacterium, Eubacterium, and Lactobacillus and the lower abundance of Bacteroides in the group after the intervention than that before the intervention. Hierarchical clustering of habitual dietary intake was performed based on the pattern of changes in the gut microbiota and were classified into distinct three clusters. Cluster I consisted of sucrose, cluster II mainly included fat intake, and cluster III mainly included carbohydrate intake. Moreover, the amount of change in Faecalibacterium was positively correlated with the intake of rice, but negatively correlated with the intake of bread. The intake of potato was negatively correlated with the amount of change in Akkermansia and Subdoligranulum. Acarbose altered the composition of gut microbiome in Japanese patients with T2D, which might be linked to the habitual dietary intake.  相似文献   
58.
We analyzed the genetic origins of anti-GD3 antibodies by comparing nucleotide sequences of the variable regions from the human monoclonal antibody (mAb), 27-26 (mu, k), established from a patient with leukemia, and another human anti-GD3 mAb, HJM-1 (mu, lambda) derived from a patient with melanoma. The variable regions of 27-26 and HJM-1 were remarkably similar to the germ-line genes. The mAb 27-26 was thought to be derived from germ-line repertoire expanded throughout our experiment. HJM-1 was derived from lymphocytes stimulated by GD3 abundantly expressed on melanoma cells.  相似文献   
59.
To investigate the role of p53 abnormalities in predicting the survival of patients with non-small cell lung cancer (NSCLC), polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP) and immunohistochemical analyses were performed on 74 and 67 tumor samples, respectively, from patients with pathological stage I-IIIa NSCLC. An abnormally migrating SSCP band was observed in 21 of 74 (28%) tumor specimens. DNA sequence analysis revealed 23 intragenic mutations including 3 small deletions and 20 point mutations. Immunohistochemical analysis using the DO-7 monoclonal antibody showed abnormal expression of p53 in 27 of 67 (40%) patients. The concordance rate between immunohistochemical and PCRSSCP analyses was 73% (49/67) in this study. Univariate and multivariate analyses demonstrated that abnormal expression of p53 may be associated with prolonged survival (p=0.0997 and 0.0099, respectively). In contrast, no relationship was observed between p53 mutation and overall survival (0.6968). These results suggest that p53 status and the survival outcome changes between immunohistochemical and mutational analyses in stage I-IIIa NSCLC.  相似文献   
60.
Three myoepitheliomas (MEOs) derived from the salivary glands were examined immunohistochemically. Proliferating cell nuclear antigen (PCNA)-positive cells were very rare (less than 2% of all tumor cells) in localized tumors of case 1 (epithelioid) (E-oid) cells) and case 2 (plasmacytoid) (P-toid) cells with a small number of spindle-shaped cells), but the percentage of PCNA-positive cells was high (21.8%) in case 3 (clear cells) exhibiting bone destruction. Strong c-myc expression was detected in all the tumors, but p53 or c-erbB-2 protein was not detected in any of the cases. More than half of the clear cells were positive for epidermal growth factor (EGF), while fewer tumor cells in cases 1 and 2 expressed EGF. A few tumor cells in cases 2 and 3 were positive for EGF-receptor (R). Keratin was most prominent in the E-oid cells, The P-toid cells were most strongly positive for S-100 protein followed by the E-oid and clear cells. More than half of the spindle-shaped cells and one-third of the E-oid cells were positive for alpha-smooth muscle actin (alpha-SMA), but less than 5% of the clear cells and none of the P-toid cells were positive for alpha-SMA. These results suggest that tumor cells in MEO are heterogenous and have different proliferation activities.  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