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   17507篇
  免费   1344篇
  国内免费   38篇
耳鼻咽喉   160篇
儿科学   638篇
妇产科学   503篇
基础医学   2369篇
口腔科学   208篇
临床医学   2620篇
内科学   3012篇
皮肤病学   190篇
神经病学   1951篇
特种医学   403篇
外科学   1332篇
综合类   239篇
一般理论   37篇
预防医学   2577篇
眼科学   348篇
药学   986篇
中国医学   7篇
肿瘤学   1309篇
  2023年   128篇
  2022年   182篇
  2021年   378篇
  2020年   227篇
  2019年   356篇
  2018年   419篇
  2017年   315篇
  2016年   338篇
  2015年   415篇
  2014年   557篇
  2013年   871篇
  2012年   1175篇
  2011年   1260篇
  2010年   691篇
  2009年   578篇
  2008年   1109篇
  2007年   1178篇
  2006年   1208篇
  2005年   1147篇
  2004年   1024篇
  2003年   973篇
  2002年   987篇
  2001年   148篇
  2000年   122篇
  1999年   145篇
  1998年   210篇
  1997年   158篇
  1996年   136篇
  1995年   118篇
  1994年   131篇
  1993年   127篇
  1992年   92篇
  1991年   72篇
  1990年   85篇
  1989年   82篇
  1988年   76篇
  1987年   65篇
  1986年   84篇
  1985年   81篇
  1984年   93篇
  1983年   73篇
  1982年   99篇
  1981年   77篇
  1980年   96篇
  1979年   52篇
  1978年   64篇
  1977年   58篇
  1975年   60篇
  1974年   51篇
  1973年   59篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
82.
83.
Interactions are known to occur in the brain between serotonin (5-HT) and substance P (SP). To investigate whether SP can directly influence serotonergic neurons, double immunohistochemical labelings were performed on rat brain sections with NK1 or NK3 affinity-purified antibodies and a 5-HT monoclonal antibody. It was found that the vast majority of serotonergic cell bodies do not colocalize NK1 or NK3 labeling. Only in the central linear nucleus and ventral part of the dorsal raphe nucleus were a few serotonergic neurons double-labeled for NK1 receptors (15 and 0.8% of serotonergic neurons, respectively). It is suggested that serotonergic neurons are not major direct targets for SP in the rat brain.  相似文献   
84.
Sex-based differences in CD4 T-cell (CD4) counts are well recognized, but the basis for these differences has not been identified. Conceivably, homeostatic factors may play a role in this process by regulating T-cell maintenance and repletion. Interleukin (IL)-7 is essential for normal T-cell production and homeostasis. We hypothesized that differences in IL-7 might contribute to sex-based differences in CD4 counts. Circulating IL-7 levels were analyzed in 299 HIV-1-infected women and men. Regression analysis estimated that IL-7 levels were 40% higher in women than in men (P = 0.0032) after controlling for CD4 count, age, and race. Given the important role of IL-7 in T-cell development and homeostasis, these findings suggest that higher IL-7 levels may contribute to higher CD4 counts in women.  相似文献   
85.
Purpose: To determine whether the observed phenotypic stability in explosive strength during adolescence, as measured by inter-age correlations in vertical jump (VTJ), is mainly caused by genetic and/or environmental factors. Methods: Subjects are from the Leuven Longitudinal Twin Study (LLTS) (n = 105 pairs, equally divided over five zygosity groups). VTJ data were aligned on age at peak height velocity (APHV) to attenuate the temporal fluctuations in inter-age correlations caused by differences in timing of the adolescent growth spurt. Simplex models were fitted using structural equation modelling. Results: After aligning the data on APHV, the annual inter-age correlations show a clear simplex structure over a 4 year interval. The best fitting models included additive genetic and unique environmental sources of variation. Heritability estimates ranged between 60.8% (CI 37.7%–77.2%) and 87.3% (CI 74.2%–94.0%) for boys and between 76.5% (CI 56.7%–89.0%) and 88.6% (CI 77.8%–94.1%) for girls. Up to 56.4% and 62.8% of the total variation at the last measurement occasion is explained by additive genetic factors that already explained a significant amount of variation at previous measurement occasions in boys and girls respectively. It thus can be concluded that the observed stability of explosive strength during adolescence is mainly caused by a stable genetic influence in boys and girls. Conclusions: Additive genetic factors seem to be the main cause of the observed phenotypic stability in VTJ performance in boys and girls during adolescence.  相似文献   
86.
87.
88.
Tissue modulated Raman spectroscopy was used noninvasively to measure blood glucose concentration in people with type I and type II diabetes with HemoCue fingerstick measurements being used as reference. Including all of the 49 measurements, a Clarke error grid analysis of the noninvasive measurements showed that 72% were A range, i.e., clinically accurate, 20% were B range, i.e., clinically benign, with the remaining 8% of measurements being essentially erroneous, i.e., C, D, or E range. Rejection of 11 outliers gave a correlation coefficient of 0.80, a standard deviation of 22 mg/dL with p<0.0001 for N=38 and places all but one of the measurements in the A and B ranges. The distribution of deviations of the noninvasive glucose measurements from the fingerstick glucose measurements is consistent with the suggestion that there are at least two systematic components in addition to the random noise associated with shot noise, charge coupled device spiking, and human factors. One component is consistent with the known variation of fingerstick glucose concentration measurements from laboratory reference measurements made using plasma or whole blood. A weak but significant correlation between the deviations of noninvasive measurements from fingerstick glucose measurements and the test subject's hemoglobin concentration was also observed.  相似文献   
89.
Sex chromosome abnormalities such as Turner syndrome, Klinefelter syndrome, triple X syndrome, and 47,XYY can be prenatally diagnosed and electively terminated. This investigation examined the pattern of pregnancy outcome of prenatally and postnatally diagnosed sex chromosome abnormalities in Hawaii during 1986-1999 and calculated prenatal diagnosis and subsequent elective termination rates for various factors. Data were obtained from a statewide population-based birth defects registry. The study included 205 detected sex chromosome abnormality cases of which 93 (45%) were live births, 18 (9%) late fetal deaths, 37 (18%) early fetal deaths, and 57 (28%) elective terminations. Pregnancy outcome distribution varied by type of sex chromosome abnormality. Prenatal diagnosis was reported for 132 (64%) of the cases, of which 46 (35%) were subsequently electively terminated. Eleven cases were elective terminations where the sex chromosome abnormality was diagnosed after delivery. Elective termination rates subsequent to prenatal diagnosis differed by sex chromosome abnormality, being highest for 45,X (54%), followed by 47,XXY (46%), 47,XYY (29%), and 47,XXX (17%). Although prenatal diagnosis rates increased significantly over the time period (P = 0.006), the subsequent elective termination rate declined slightly, albeit the trend was not statistically significant (P = 0.440). The prenatal diagnosis rate was highest for the 35-39-year maternal age group, although this age group did not have subsequent elective termination rates higher than other maternal age groups. Pregnancy outcome distribution and prenatal diagnosis and subsequent elective termination of sex chromosome abnormalities appeared to depend on the type of sex chromosome abnormality, year of delivery, and maternal age.  相似文献   
90.
Recurrent respiratory papillomatosis (RRP) is the most common benign tumour of the larynx, affecting both children and adults. We present a series of 25 patients, including 10 cases of juvenile multiple, 8 cases of adult solitary, and 7 cases of adult multiple RRP. Biopsy tissue from each patient was screened by Southern blot hybridization and polymerase chain reaction for the presence of human papillomavirus (HPV) DNA. Sera from patients and age- and sex-matched controls were tested for the presence of HPV-specific antibodies using a synthetic pep-tide derived from the minor capsid protein (L2) of HPV 6/11. By Southern blot hybridization and/or polymerase chain reaction, biopsies from all patients were positive for HPV 6/11 DNA. There was no difference in antibody response between cases and controls. Female cases and controls had significantly higher antibody titers than male subjects. A correlation was observed between the HPV-specific antibody level and the number of surgery-necessitating recurrences. © 1994 Wiiey-Liss, Inc.  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