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   6345篇
  免费   343篇
  国内免费   27篇
耳鼻咽喉   70篇
儿科学   98篇
妇产科学   72篇
基础医学   934篇
口腔科学   190篇
临床医学   375篇
内科学   1477篇
皮肤病学   61篇
神经病学   455篇
特种医学   313篇
外科学   748篇
综合类   36篇
预防医学   220篇
眼科学   260篇
药学   579篇
中国医学   13篇
肿瘤学   814篇
  2023年   18篇
  2022年   57篇
  2021年   96篇
  2020年   36篇
  2019年   47篇
  2018年   63篇
  2017年   53篇
  2016年   75篇
  2015年   85篇
  2014年   129篇
  2013年   169篇
  2012年   247篇
  2011年   272篇
  2010年   163篇
  2009年   141篇
  2008年   276篇
  2007年   300篇
  2006年   304篇
  2005年   288篇
  2004年   323篇
  2003年   305篇
  2002年   324篇
  2001年   258篇
  2000年   276篇
  1999年   249篇
  1998年   112篇
  1997年   93篇
  1996年   84篇
  1995年   70篇
  1994年   66篇
  1993年   68篇
  1992年   152篇
  1991年   190篇
  1990年   181篇
  1989年   168篇
  1988年   157篇
  1987年   137篇
  1986年   132篇
  1985年   95篇
  1984年   77篇
  1983年   51篇
  1982年   37篇
  1981年   29篇
  1980年   16篇
  1979年   49篇
  1978年   43篇
  1977年   34篇
  1976年   26篇
  1975年   14篇
  1966年   9篇
排序方式: 共有6715条查询结果,搜索用时 15 毫秒
51.
The extent of restriction fragment length polymorphism in genes for the arginine deiminase enzyme among 28 species of mycoplasmas was assessed by Southern blot analysis of DNA digested with EcoRI or TaqI nuclease probed with a 725-bp internal fragment of the arginine deiminase gene from Mycoplasma arginini. The results indicated unexpected heterogeneity among species of a single genus.  相似文献   
52.
Genetic polymorphism in the ABO blood group gene of Han, Kazak and Uygur populations inhabiting the most northwestern part of China was investigated using polymerase chain reaction-based techniques. The present study enrolled 43 healthy unrelated Han, 37 Kazak and 59 Uygur volunteers. The allele in A1 blood group is distinguished A0101 and A0102 in difference of nucleotide position 467. The A0101 allele is more frequent in Caucasian and the A0102 allele is characteristic in Mongoloid. It must be notable that A0201 in the A2 group (with a single base deletion at nucleotides 1059 to 1061) which was characteristic of Caucasian was observed in Kazak and Uygur populations but not in Han. Further, 00201 (with no nucleotide deletion at 261 and three nucleotide differences), which is frequent in different races including Caucasian except for Mongoloid, was detected also in Kazak and Uygur populations. The frequencies of B0101 in Kazak, Uygur and Han were comparable to those of other Asian populations but higher than those of Caucasian populations. Collectively, these results reveal that the allele frequencies of Kazak and Uygur at the ABO blood group locus are an intermediate between those of Mongoloid and Caucasian, suggesting the admixed feature of Kazak and Uygur with Mongoloid and Caucasian.  相似文献   
53.
In order to clarify the histological and immunohistochemical characteristics of suppurative granuloma in abscess-forming granulomatous lymphadenitis (AGL), and the relation between AGL and cat scratch disease (CSD), 36 cases of AGL were studied. The combined results showed that there were two types of suppurative granulomas. The suppurative granulomas histologically revealed small lymphocytes of predominantly T cell phenotype distributed among the epithelioid histiocytes bordering central necrotic areas in the suppurative granulomas. These suppurative granulomas could be further subdivided into two groups, mainly those with and without the intermingling of large transformed cells of B-cell phenotypes: Type B granuloma with large transformed B cells and Type A without large transformed B cells. Both types of granulomas were observed in a varying degree in most cases. According to the predominant type of granulomas, 36 patients with AGL were further classified into two groups: Group I of Type A dominance and Group II of Type B dominance. Warthin-Starry (WS) silver stain positive bacteria, which are said to be a causative agent of CSD, were present in about 50% of both groups. No Brown-Hopps' Gram-positive bacteria, fungus, toxoplasma, Chlamydia or Bacillus Calmette-Guerin antigen were found in any case. Clinically, there was no significant difference between these two groups. On the other hand, the detection of WS-positive bacteria seemed to have some relationship with the duration of disease and the history of exposure to cats, and 70% of AGL cases occurred in autumn without a single concurrent epidemic.  相似文献   
54.
Loop-mediated isothermal amplification (LAMP) is a novel nucleic acid amplification method in which reagents react rapidly and efficiently, with a high specificity, under isothermal conditions. We used a LAMP assay for the detection of herpes simplex virus type 1 (HSV-1), herpes simplex virus type 2 (HSV-2), and varicella-zoster virus (VZV). The virus specificities of primers were confirmed by using 50 HSV-1, 50 HSV-2, and 8 VZV strains. The assay was performed for 45 min at 65 degrees C. The LAMP assay had a 10-fold higher sensitivity than a PCR assay. An analysis of nucleotide sequence variations in the target and primer regions used for the LAMP assay indicated that 3 of 50 HSV-1 strains had single nucleotide polymorphisms. No HSV-2 or VZV strains had nucleotide polymorphisms. Regardless of the sequence variation, there were no differences in sensitivity with the HSV-1-specific LAMP assay. To evaluate the application of the LAMP assay for clinical diagnosis, we tested clinical samples from 40 genital herpes patients and 20 ocular herpes patients. With the LAMP assay, 41 samples with DNA extraction and 26 direct samples without DNA extraction were identified as positive for HSV-1 or HSV-2, although 37 samples with DNA extraction and just one without DNA extraction were positive by a PCR assay. Thus, the LAMP assay was less influenced than the PCR assay by the presence of inhibitory substances in clinical samples. These observations indicate that the LAMP assay is very useful for the diagnosis of HSV-1, HSV-2, and VZV infections.  相似文献   
55.
To evaluate the potential role of NK1.1 (CD161c) cells in autoimmune uveoretinitis, we treated experimental autoimmune uveoretinitis (EAU)-susceptible mice with anti-CD161c antibodies (PK136) to deplete natural killer (NK) cells. Injection of anti-CD161c antibodies deleted NK cells from the peripheral blood of EAU-susceptible mice. The T cell proliferative response against the ocular autoantigen K2 was not suppressed in mice treated with anti-CD161c antibody when compared with T cells from control mice. Although mice treated with anti-CD161c developed EAU, the clinical severity on days 17 and 19 after induction of EAU was significantly mild in anti-CD161c-treated mice compared with control mice. In addition, the histopathological severity of EAU was significantly milder in mice treated with anti-CD161c antibodies than controls 21 days after induction of EAU. Our results indicate that the severity of EAU is augmented by NK1.1(+) NK cells.  相似文献   
56.
A Japanese patient with tuberous sclerosis (TSC), who manifested with multiple lung cysts and pneumothorax, is described. All exons of two TSC genes, TSC1 and TSC2, in peripheral blood leukocytes from the patient were analyzed by polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP). A novel T-to-G transition was found in exon 19 of TSC2 at nucleotide position 2168. This mutation caused an amino acid change, L717R. There was no such mutation in any other family members or in 100 normal Japanese. An automated sequencer-assisted quantitative analysis of normal and mutated SSCP-bands revealed no loss of heterozygosity (LOH) in the lung cyst tissue of the patient.  相似文献   
57.
F213I突变型高雪氏病分子伴侣治疗方法的研究   总被引:3,自引:0,他引:3  
目的 研究高雪氏病新的分子治疗方法。方法 用β-葡萄糖脑昔脂酶(β-glucocerebrosidase,β-Glc)(EC3.2.1.45)的底物类似物(glucocerebroside analogue,GCA)作为分子伴侣,处理体外培养的不同突变型的高雪氏病患者皮肤成纤维细胞,采用荧光酶学手段测定β-Glc活性;Western印迹杂交技术分析该酶蛋白表达的量;细胞双染确定β-Glc在细胞内的定位;薄层层析法分析葡萄糖脑苷脂的降解情况。结果 该酶的底物类似物GCA可以提高体外培养的F213I突变型患者成纤维细胞内β-Glc活性;增加该酶蛋白的表达量;促进该酶蛋白向溶酶体内转运,加速底物葡萄糖脑苷脂(glucocerebroside,GlcCer)的降解。结论低分子量的GCA作为一种分子伴侣可能为F213I突变型高雪氏病的治疗开辟一条新的途径。  相似文献   
58.
Summary We report here the nucleotide sequences of the core region of HCV isolates from Egyptian and Yemeni patients and the method for classifying these HCV isolates by phylogenetic analysis. Sequence comparison suggested that the genotypes of these isolates were the same. Preliminary phylogenetic analysis of the HCV core region indicated that the genotypes of both isolates were 1c. However, an additional phylogenetic tree of the HCV core region constructed using a greater number of HCV isolates than that used in the preliminary analysis and on the basis of alignment of nucleotide sequences in an appropriate length indicated that the genotypes of these isolates were 4 and not 1c. For a more detailed analysis, the nucleotide sequences of the HCV E1 region as well as the core region for the same Yemeni patient were determined. A phylogenetic tree of the E1 region confirmed that the genotype of the HCV isolate from the Yemeni patient was 4. These data indicate that even when classifying HCV isolates using phylogenetic analysis, the misclassification would occur if care is not taken regarding the number and sequence lengths of the isolates included in the analysis.  相似文献   
59.
The ocular inflammation and antibody production that follow intravitreal injection of rabbit eyes with bovine gamma globulin were suppressed by treatment with Cytoxan by the intramuscular (i.m.) route. The drug suppressed PFC responses of uveal tract and corneal cells when it was administered, beginning as late as 5 days after immunization, if treatment was continued until day 12 or 13. Short-term treatments and treatment with smaller Cytoxan doses were less effective. We noted a good correlation between the presence or absence of ocular inflammation, suppression of ocular PFC responses and depression of serum, aqueous humour and vitreous humour antibody titres. In some treatment groups ocular antibody production seemed to be completely suppressed, while in others antibody production was significantly delayed.  相似文献   
60.
Plasma lipopolysaccharide (LPS)-binding protein (LBP) and membrane CD14 function to enhance the responses of monocytes to low concentrations of endotoxin. Surprisingly, recent reports have suggested that LBP or CD14 may be dispensable for macrophage responses to low concentrations of LPS or may even exert an inhibitory effect in the case of LBP. We therefore investigated whether LBP and CD14 participated in the response of mouse peritoneal exudate macrophages (PEM) to LPS stimulation. In the presence of a low amount of plasma (<1%) or of recombinant mouse or human LBP, PEM were found to respond to low concentrations of LPS (<5 to 10 ng/ml) in an LBP- and CD14-dependent manner. However, tumor necrosis factor production (not interleukin-6 production) by LPS-stimulated PEM was reduced when cells were stimulated in the presence of higher concentrations of plasma or serum (5 or 10%). Yet, the inhibitory effect of plasma or serum was not mediated by LBP. Taken together with previous results obtained with LBP and CD14 knockout mice in models of experimental endotoxemia, the present data confirm a critical part for LBP and CD14 in innate immune responses of both blood monocytes and tissue macrophages to endotoxins.  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