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   9542篇
  免费   446篇
  国内免费   36篇
耳鼻咽喉   108篇
儿科学   273篇
妇产科学   75篇
基础医学   1113篇
口腔科学   342篇
临床医学   546篇
内科学   2511篇
皮肤病学   137篇
神经病学   711篇
特种医学   383篇
外科学   1642篇
综合类   57篇
预防医学   334篇
眼科学   297篇
药学   624篇
中国医学   12篇
肿瘤学   859篇
  2022年   69篇
  2021年   181篇
  2020年   98篇
  2019年   117篇
  2018年   147篇
  2017年   134篇
  2016年   142篇
  2015年   158篇
  2014年   200篇
  2013年   281篇
  2012年   373篇
  2011年   433篇
  2010年   252篇
  2009年   208篇
  2008年   405篇
  2007年   425篇
  2006年   438篇
  2005年   392篇
  2004年   383篇
  2003年   386篇
  2002年   388篇
  2001年   379篇
  2000年   364篇
  1999年   371篇
  1998年   122篇
  1997年   80篇
  1996年   82篇
  1995年   78篇
  1994年   57篇
  1993年   61篇
  1992年   265篇
  1991年   227篇
  1990年   231篇
  1989年   269篇
  1988年   200篇
  1987年   190篇
  1986年   188篇
  1985年   171篇
  1984年   129篇
  1983年   97篇
  1982年   62篇
  1981年   48篇
  1979年   75篇
  1978年   46篇
  1977年   46篇
  1975年   48篇
  1974年   46篇
  1973年   48篇
  1971年   47篇
  1966年   44篇
排序方式: 共有10000条查询结果,搜索用时 234 毫秒
71.
A case of leiomyosarcoma of the spermatic cord, occurring in a 79-year-old male patient, is reported. The tumor was resected with high inguinal ligation and orchiectomy. It was located at the scrotal part of the spermatic cord on the left side and was shown to have originated from the spermatic duct using the dissecting method. Histologically, it was identical to leiomyosarcoma showing a typical morphological appearance of smooth muscle cell tumor in the conventional histochemical preparations as well as a focal positive reaction to antidesmin antibody, a marked nuclear pleomorphism, and abundant mitotic figures. The patient had been untroubled for six months after the resection of the tumor. Leiomyosarcoma arising in spermatic cord is quite rare.  相似文献   
72.
Association of defensin beta-1 gene polymorphisms with asthma   总被引:2,自引:0,他引:2  
BACKGROUND: Defensins are antimicrobial peptides that may take part in airway inflammation and hyperresponsiveness. OBJECTIVE: We characterized the genetic diversity in the defensin beta-1 (DEFB1) locus and tested for an association between common genetic variants and asthma diagnosis. METHODS: To identify single nucleotide polymorphisms (SNPs), we resequenced this gene in 23 self-defined European Americans and 24 African Americans. To test whether DEFB1 genetic variants are associated with asthma, we genotyped 4 haplotype-tag SNPs in 517 asthmatic and 519 control samples from the Nurses' Health Study (NHS) and performed a case-control association analysis. To replicate these findings, we evaluated the DEFB1 polymorphisms in a second cohort from the Childhood Asthma Management Program. RESULTS: Within the NHS, single SNP testing suggested an association between asthma diagnosis and a 5' genomic SNP (g.-1816 T>C; P = .025) and intronic SNP (IVS+692 G>A; P = .054). A significant association between haplotype (Adenine, Cytosine, Thymine, Adenine [ACTA]) and asthma ( P = .024) was also identified. Associations between asthma diagnosis and both DEFB1 polymorphisms were observed in Childhood Asthma Management Program, a second cohort: g.-1816 T>C and IVS+692 G>A demonstrated significant transmission distortion ( P = .05 and .007, respectively). Transmission distortion was not observed in male subjects. The rare alleles (-1816C and +692A) were undertransmitted to offspring with asthma, suggesting a protective effect, contrary to the findings in the NHS cohort. Similar effects were evident at the haplotype level: ACTA was undertransmitted ( P = .04) and was more prominent in female subjects ( P = .007). CONCLUSION: Variation in DEFB1 contributes to asthma diagnosis, with apparent gender-specific effects.  相似文献   
73.
74.
To evaluate the pathogenetic roles of immune complexes and alveolar hyaline membrane in idiopathic interstitial pneumonia (IIP), immunohistological and ultrastructural studies of the kidney and lung were performed in 23 cases of IIP, 19 cases of autoimmune diseases, 17 cases of interstitial pneumonia other than IIP, and 11 cases of bronchopneumonia as a control group. None of the cases of IIP or interstitial pneumonia other than IIP showed immune complexes in the alveolar and glomerular capillary walls. On the other hand, one case of SLE was positive for IgG and components of complement along the alveolar and glomerular capillary walls. The alveolar hyaline membrane in the present cases revealed immunoglobulins as well as components of complement, which were poorly soluble in chaotropic solution or acidic buffer. These results indicate that circulating immune complexes play a minor role in the pathogenesis of IIP and other types of interstitial pneumonia, and that there is no relationship between immune complex deposition in alveoli and the alveolar hyaline membrane. It is necessary to further investigate factors other than immune complexes involved in alveolar tissue damage and to clarify the significance of the hyaline membrane in the processes occurring from acute changes to pulmonary fibrosis in IIP.  相似文献   
75.
太空发育鸡胚的前庭感受器细胞形态学研究   总被引:4,自引:0,他引:4  
为了探讨太空微重力对鸡胚前庭感觉上皮细胞的形态发育的影响 ,选取在航天飞机 (STS-2 9)发育鸡胚和地面发育鸡胚各两只 ,利用计算机显微测量技术分别测量椭圆囊和球囊的毛细胞、支持细胞核的切面面积、周长、形状系数。太空发育鸡胚的球囊支持细胞核的切面面积、周长显著大于地面组 ,形状系数无差异 ;太空发育鸡胚的椭圆囊支持细胞核的切面面积、周长、形状系数以及椭圆囊和球囊毛细胞的切面面积、周长与地面发育鸡胚相比无明显差异。微重力可能对球囊支持细胞核的体积发育有影响 ,对椭圆囊和球囊的毛细胞以及椭圆囊支持细胞核的形态发育无影响。  相似文献   
76.
BACKGROUND: The loop-mediated isothermal amplification (LAMP) method is a novel technique for the amplification of specific DNA sequences. OBJECTIVES: To establish the LAMP method for amplifying Epstein-Barr virus (EBV) DNA and to examine its reliability for the detection of EBV DNA in clinical specimens. STUDY DESIGN: Sera from 108 patients, who were initially suspected of primary EBV infection, were tested by the EBV LAMP method, and the results were compared with those of the real-time PCR assay. Serological examination was regarded as the standard diagnostic method. RESULTS: To diagnose primary EBV infection, the sensitivity of LAMP was 86.4% and the specificity was 100%. The sensitivity of the real-time PCR assay was 84.1% and the specificity was 98.4%. Longitudinal analysis showed that the detection rate of EBV DNA in serum by the LAMP method decreased with time in accordance with the decrease of the EBV load. EBV DNA could not be detected in serum 40 days after onset of symptoms. CONCLUSIONS: These results indicate that the sensitivity and specificity of the LAMP method are comparable to those of real-time PCR and that detecting EBV DNA in serum by this method is potentially useful for diagnosing primary EBV infection.  相似文献   
77.
Fluconazole monotherapy for cryptococcosis in non-AIDS patients   总被引:3,自引:0,他引:3  
Treatment with 200 to 400 mg/day fluconazole was evaluated in 44 patients without AIDS who had cryptococcosis (19 with cryptococcal meningitis, 22 with pulmonary cryptococcosis, 3 with other cryptococcal infections). For all patients, the clinical response rate was 89% (48% were clinically cured and 41 % clinically improved). Of the patients with cryptococcal meningitis, 89% were mycologically cured. These rates are comparable to those obtained in the treatment of AIDS patients with cryptococcal disease. In the group of patients with cryptococcal meningitis, there was a high rate of agreement between the mycological response to therapy and cryptococcal antigen test results. The use of cryptococcal antigen testing is recommended in all patients with cryptococcosis.  相似文献   
78.
BACKGROUND: The yeast [PSI+] factor is transmitted by a prion mechanism involving self-propagating Sup35 aggregates. As with mammalian prions, a species barrier prevents prion transmission between yeast species. The N-terminal of Sup35 of Saccharomyces cerevisiae, necessary for [PSI+], contains two species-signature elements-a Gln/Asn-rich region (residues 1-41; designated NQ) that is followed by oligopeptide repeats (designated NR). RESULTS: In this study, we show that S. cerevisiae[PSI+] is transmissible through plasmid shuffling and cytoplasmic transfer to heterotypic Sup35s whose NQ is replaced with the S. cerevisiae NQ. In addition to homology, the N-terminal location is essential for NQ mediated susceptibility to [PSI+] transmission amongst heterotypic Sup35s. In vitro, a swap of NQ of S. cerevisiae Sup35 led to cross seeding of amyloid formation. CONCLUSIONS: These findings suggest that NQ discriminates self from non-self, and is sufficient to initiate [PSI+] transmission irrespective of whether NR is heterotypic. NR as well as NQ alone coalesces into existing [PSI+] aggregates, showing their independent potentials to interact with the identical sequence in the [PSI+] conformer. The role of NQ and NR in [PSI+] prion formation is discussed.  相似文献   
79.
80.
A protein reacting with antibody against chum salmon serum IgM was found in salmon egg yolk. The protein tentatively named IgM-like protein was partially purified from egg yolk extract by removal of euglobulin from the extract by dialysis against a low ionic strength buffer following DEAE ion-exchange chromatography. The IgM-like protein was antigenically identical with serum IgM, showing a complete fusion of precipitin line of the IgM-like protein with that of serum IgM on double immunodiffusion with antiserum IgM. The molecular weight of intact IgM-like protein was assessed by 3% SDS-PAGE to be 495 kDa, smaller than that of serum IgM (750 kDa). Upon 10% SDS-PAGE with mercaptane and subsequent Western blotting with antiserum IgM, the IgM-like protein separated into three components with molecular weights of 68 kDa, 51.5 kDa, and 23 kDa. The 68 kDa, the most minor component, and the 23 kDa, the smallest molecular weight component, were identified, respectively, as H and L chain in view of their molecular weights identical to those of serum IgM. The 51.5 kDa, the main component, was also identified as H chain, since it reacted with antiserum IgM absorbed with purified L chain. From these results, it was concluded that the IgM-like protein in egg yolk, having a lower molecular weight than that of serum IgM, consists of H chain of smaller molecular weight as well as H and L chain of ordinary molecular weight.  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