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   3869篇
  免费   354篇
  国内免费   27篇
耳鼻咽喉   83篇
儿科学   110篇
妇产科学   117篇
基础医学   524篇
口腔科学   44篇
临床医学   441篇
内科学   890篇
皮肤病学   53篇
神经病学   301篇
特种医学   263篇
外国民族医学   1篇
外科学   376篇
综合类   145篇
一般理论   2篇
预防医学   376篇
眼科学   62篇
药学   268篇
中国医学   3篇
肿瘤学   191篇
  2021年   55篇
  2020年   33篇
  2019年   52篇
  2018年   55篇
  2017年   45篇
  2016年   49篇
  2015年   55篇
  2014年   84篇
  2013年   160篇
  2012年   136篇
  2011年   156篇
  2010年   106篇
  2009年   116篇
  2008年   112篇
  2007年   160篇
  2006年   137篇
  2005年   145篇
  2004年   119篇
  2003年   134篇
  2002年   148篇
  2001年   139篇
  2000年   123篇
  1999年   117篇
  1998年   89篇
  1997年   82篇
  1996年   69篇
  1995年   54篇
  1994年   65篇
  1993年   63篇
  1992年   80篇
  1991年   83篇
  1990年   85篇
  1989年   102篇
  1988年   76篇
  1987年   79篇
  1986年   94篇
  1985年   65篇
  1984年   55篇
  1983年   63篇
  1982年   40篇
  1981年   42篇
  1980年   27篇
  1979年   45篇
  1978年   25篇
  1976年   30篇
  1975年   32篇
  1974年   41篇
  1973年   28篇
  1972年   35篇
  1971年   26篇
排序方式: 共有4250条查询结果,搜索用时 15 毫秒
31.
32.
The ProHeat reusable hot pack is being used increasingly as a substitute for the standard hydrocollator steam pack. This study evaluated the effects of these two modalities on skin temperature. Seventeen subjects were studied during separate 30-minute applications of a ProHeat pack with a wet barrier, a ProHeat pack with a dry barrier, a hydrocollator pack, and a control pack on their nondominant calf. We measured the skin interface temperature and pack surface temperature during each application with surface thermocouples. The skin interface temperature rise time to the minimum therapeutic temperature (104°F) and the total time at and above the minimum therapeutic temperature, for each application, were analyzed using an analysis of variance (ANOVA) with repeated measures (p<.05). The ProHeat pack application, with one layer of wet toweling as a barrier, was not significantly different from the hydrocollator steam pack application. We conclude that the ProHeat pack, prepared with a wet barrier, can be considered a viable alternative to the standard hydrocollator steam pack.  相似文献   
33.
Ligamentous injuries of the ankle are usually benign and may be managed satisfactorily by nonoperative measures. This is not true, however, of the Maisonneuve variant. In this paper we present a case report of a high school athlete who sustained a Maisonneuve fracture dislocation of the ankle. The diagnosis was missed initially, because of an incomplete examination. The subsequent physical and radiographic examination revealed the proper diagnosis. Guidelines for the evaluation and appropriate treatment are discussed.  相似文献   
34.
35.
36.
The ratio between the length of the 2nd and 4th digits is: (a) fixed in utero; (b) lower in men than in women; (c) negatively related to testosterone and sperm counts; and (d) positively related to oestrogen concentrations. Prenatal levels of testosterone and oestrogen have been implicated in infertility, autism, dyslexia, migraine, stammering, immune dysfunction, myocardial infarction and breast cancer. We suggest that 2D:4D ratio is predictive of these diseases and may be used in diagnosis, prognosis and in early life-style interventions which may delay the onset of disease or facilitate its early detection.  相似文献   
37.
During spermiogenesis, histone-to-protamine exchange causes chromatin condensation. Spermatozoa from infertile men are known to exhibit an increased protamine-1 (PRM1) to protamine-2 (PRM2) protein ratio. Since patients undergoing testicular sperm extraction (TESE) followed by intracytoplasmic sperm injection (ICSI) reveal low fertilization rates, whether the outcome of ICSI could be related to the percentage of round spermatids expressing PRM1-mRNA and PRM2-mRNA was investigated. Applying in-situ hybridization, 55 testicular biopsies from men undergoing TESE/ICSI were investigated. The percentage of PRM1-mRNA and PRM2-mRNA positive spermatids was significantly (P < 0.0001) decreased in men with at least qualitatively normal spermatogenesis (PRM1-mRNA: 58.4 +/- 13.8%; PRM2-mRNA: 56.4 +/- 11.3%) and impaired spermatogenesis (PRM1-mRNA: 32.6 +/- 10.8%; PRM2-mRNA: 31.7 +/- 11.1%) compared with men with obstructive azoospermia and quantitatively normal spermatogenesis (PRM1-mRNA: 79.9 +/- 4.6%; PRM2-mRNA: 78.1 +/- 5.7%). A positive correlation (r(PRM1) = 0.733; r(PRM2) = 0.784; P < 0.001) was demonstrated between the score and the percentage of PRM1-mRNA and PRM2-mRNA positive spermatids. While successful fertilization was neither related to the score, nor to the percentage of PRM1-mRNA and PRM2-mRNA positive spermatids, a significant (P < 0.05) relationship was demonstrated between successful fertilization and the PRM1-mRNA to PRM2-mRNA ratio. Therefore, the PRM1-mRNA to PRM2-mRNA ratio in round spermatids may serve as a possible predictive factor for the outcome of ICSI.  相似文献   
38.
Mycobacterial isolates were obtained by radiometric culture from 33 different species of captive or free-ranging animals (n = 106) and environmental sources (n = 3) from six geographic zones within the United States. The identities of all 109 isolates were confirmed by using mycobactin J dependence and characterization of five well-defined molecular markers, including two integration loci of IS900 (loci L1 and L9), one Mycobacterium avium subsp. paratuberculosis (M. paratuberculosis)-specific sequence (locus 251), and one M. avium subsp. avium-specific marker (IS1245), as well as hsp65 and IS1311 restriction endonuclease analyses. Seventy-six acid-fast isolates were identified as M. paratuberculosis, 15 were identified as belonging to the M. avium-M. intracellulare complex (but not M. paratuberculosis), and the remaining 18 were identified as mycobacteria outside the M. avium-M. intracellulare complex. Fingerprinting by multiplex PCR for IS900 integration loci clustered 67 of the 76 M. paratuberculosis strains into a single clade (designated clade A18) and had a Simpson's diversity index (D) of 0.53. In contrast, sequence-based characterization of a recently identified M. paratuberculosis short sequence repeat (SSR) region enabled the differentiation of the M. paratuberculosis isolates in clade A18 into seven distinct alleles (D = 0.75). The analysis revealed eight subtypes among the 33 species of animals, suggesting the interspecies transmission of specific strains. Taken together, the results of our analyses demonstrate that SSR analysis enables the genetic characterization of M. paratuberculosis isolates from different host species and provide evidence for the host specificity of some M. paratuberculosis strains as well as sharing of strains between wild and domesticated animal species.  相似文献   
39.
Shiga toxin-producing Escherichia coli (STEC) strains are a diverse group of organisms which are known to cause diarrhea and hemorrhagic colitis in humans. We have recently described a large food-borne outbreak of STEC disease caused by contaminated semidry fermented sausage (A. W. Paton, R. Ratcliff, R. M. Doyle, J. Seymour-Murray, D. Davos, J. A. Lanser, and J. C. Paton, J. Clin. Microbiol. 34:1622-1627, 1996). STEC strains belonging to several O serotypes were isolated from the contaminated food source, but of these, only a subset were isolated from patients with diarrhea or hemolytic-uremic syndrome (HUS). In the present study, we characterized these STEC isolates with respect to the presence of putative virulence-associated genes and the capacity to adhere to a human intestinal epithelial cell line (Henle 407). The O111:H- STEC strain 95NR1 (isolated from one of the outbreak HUS patients) was shown to adhere to Henle 407 cells in a dose-dependent, mannose-resistant fashion. Microscopic examination revealed a diffuse pattern of adherence for this as well as several other STEC strains. Interestingly, the adherence of STEC strains from HUS cases (both outbreak related and sporadic) was significantly greater than that of STEC strains found in the contaminated food source but not found in any patients. These studies support the hypothesis that an enhanced capacity to adhere to intestinal cells is one of the factors which distinguishes human-virulent STEC strains from those of lesser clinical significance.  相似文献   
40.
Fetal alcohol spectrum disorders (FASD) describe a range of physical, behavioral, and neurologic deficits in individuals exposed to alcohol prenatally. Reduced palpebral fissure length is one of the cardinal facial features of FASD. However, other ocular measurements have not been studied extensively in FASD. Using the Fetal Alcohol Syndrome Epidemiologic Research (FASER) database, we investigated how inner canthal distance (ICD), interpupillary distance (IPD), and outer canthal distance (OCD) centiles differed between FASD and non‐FASD individuals. We compared ocular measurement centiles in children with FASD to non‐FASD individuals and observed reductions in all three centiles for ICD, IPD, and OCD. However, when our non‐FASD children who had various forms of growth deficiency (microcephaly, short‐stature, or underweight) were compared to controls, we did not observe a similar reduction in ocular measurements. This suggests that reductions in ocular measurements are a direct effect of alcohol on ocular development independent of its effect on growth parameters, which is consistent with animal models showing a negative effect of alcohol on developing neural crest cells. Interpupillary distance centile appeared to be the most significantly reduced ocular measure we evaluated, suggesting it may be a useful measure to be considered in the diagnosis of FASD.  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