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   284篇
  免费   20篇
  国内免费   11篇
耳鼻咽喉   4篇
儿科学   10篇
妇产科学   2篇
基础医学   25篇
口腔科学   5篇
临床医学   32篇
内科学   58篇
皮肤病学   7篇
神经病学   11篇
特种医学   66篇
外科学   40篇
综合类   3篇
预防医学   5篇
眼科学   2篇
药学   36篇
中国医学   2篇
肿瘤学   7篇
  2023年   6篇
  2021年   10篇
  2020年   4篇
  2019年   2篇
  2018年   4篇
  2017年   3篇
  2016年   6篇
  2015年   5篇
  2014年   9篇
  2013年   6篇
  2012年   8篇
  2011年   9篇
  2010年   8篇
  2009年   13篇
  2008年   10篇
  2007年   17篇
  2006年   13篇
  2005年   9篇
  2004年   7篇
  2003年   10篇
  2002年   4篇
  2001年   2篇
  2000年   1篇
  1999年   1篇
  1998年   16篇
  1997年   12篇
  1996年   9篇
  1995年   9篇
  1994年   10篇
  1993年   4篇
  1992年   5篇
  1991年   3篇
  1990年   2篇
  1989年   8篇
  1988年   5篇
  1987年   9篇
  1986年   10篇
  1985年   6篇
  1984年   4篇
  1983年   1篇
  1982年   6篇
  1981年   7篇
  1980年   5篇
  1979年   2篇
  1978年   2篇
  1977年   3篇
  1976年   4篇
  1975年   2篇
  1973年   1篇
  1964年   1篇
排序方式: 共有315条查询结果,搜索用时 31 毫秒
41.
Nyberg  DA; Filly  RA; Filho  DL; Laing  FC; Mahony  BS 《Radiology》1986,158(2):393-396
Simultaneous sonography and quantitative serum human chorionic gonadotropin (HCG) levels from 126 women with threatened abortion were compared. Of 56 women with normal outcome, 39 (70%) had a gestation sac greater than or equal to 5 mm in mean sac diameter, and in each case the HCG level was 1,800 milli-international units (mIU/ml) or greater. The serum HCG levels strongly correlated with the gestation sac sizes to a mean sac diameter of 25 mm. Of 70 abnormal pregnancies, 31 demonstrated a gestation sac. Of these, 20 women (65%) had disproportionately low HCG levels relative to sac size, including 12 in whom the HCG level was less than 1,800 mIU/ml. One woman with an early molar pregnancy had a disproportionately elevated HCG level. Correlation of sonograms with a simultaneous measurement of serum HCG level is a useful method for evaluating threatened spontaneous abortion. A disproportionately low HCG level relative to gestation sac size is evidence for an abnormal pregnancy.  相似文献   
42.
Myopic crescent, refractive error and axial length were previously investigated in Hong Kong Chinese subjects. The myopic crescent was found to correlate with axial length and myopic refraction. In this study, three groups of Hong Kong Chinese with different degrees of myopia were assessed for optic disc ovalness, refractive error and axial length. The axial length was significantly correlated with the degree of myopia, indicating that the myopia was axial in nature. The regression line shows that 0.44 mm of axial elongation would give about one dioptre of increase in myopia. The elliptical ratio of the optic disc was defined as the maximal disc diameter divided by the minimal disc diameter. All three groups showed an oval disc with vertical axis greater and an increased ovalness for the high myopic group with an elliptical ratio from 1.11 in low myopia to 1.29 in high myopia. There is a small amount (about four degrees) of temporal rotation of this vertical oval orientation, which is independent of the amount of myopia. This result shows an association between axial elongation of the globe and optic disc ovalness, in addition to the previously described temporal myopic crescent. Therefore, in myopic subjects, a vertically oval disc may be associated with a myopic refraction rather than glaucoma.  相似文献   
43.
44.
LaBerge  JM; Laing  FC; Federle  MP; Jeffrey  RB  Jr; Lim  RC  Jr 《Radiology》1984,152(2):485-490
A retrospective review of the CT and ultrasound scans from examinations of 30 patients who had hepatocellular carcinoma (hepatoma) was undertaken with special emphasis placed on evaluation of hepatic distribution of tumor, vascular invasion, and extrahepatic spread. Although both CT and ultrasound detected hepatoma in 29 of 30 patients (96%), CT showed more extensive hepatic parenchymal involvement in eight of the patients. Vascular invasion was seen more frequently with ultrasound than with CT. Invasion into the main portal vein was seen by ultrasound in 11 of 30 patients (37%). Extrahepatic spread of tumor was much more frequently detected by CT and was present in 21 of 30 patients (70%). A reasoned approach to the diagnostic workup of hepatomas that will minimize invasive procedures and unnecessary surgery is presented.  相似文献   
45.
Tegtmeyer  CJ; McCue  FC  d; Higgins  SM; Ball  DW 《Radiology》1979,132(1):37-41
Single and double contrast arthrographic techniques were compared in 951 patinets with suspected meniscal injuries. Exploratory surgery of the knee was performed in 384 of these patients and good clinical follow-up was obtained in 135 patients. In the latter two groups of patients, the single contrast technique was 97% accurate in assessing the medial meniscus and 96% accurate in assessing the lateral meniscus. Double contrast arthrography was 97% accurate in assessing the medial meniscus and 93% accurate in assessing the lateral meniscus. Numerical differences in the results from the two techniques were not statistically significant. Therefore both techniques can be considered equally effective diagnostically.  相似文献   
46.
To clarify the relationship between the vertebral level reached by the thumb and the internal rotation angle of the humerus, 7 shoulders in healthy volunteers were examined by use of an electromagnetic tracking device. Measurements were repeated in the hanging-arm position with the thumb pointing anteriorly and at the buttock, sacrum, and each vertebral level up to T6. From the hanging-arm position to the buttock, 54.3% of internal rotation occurred (mean, 39.8 degrees ), and from the buttock to the sacrum, 11.7% occurred (mean, 8.6 degrees ). In total, 66% of internal rotation occurred from the hanging-arm position to the sacrum. Above the sacrum, the contribution of elbow flexion to the level of the vertebral spine became much greater, and internal rotation of the shoulder did not change significantly above the T12 level. We recommend that the level of the thumb below the buttock be subdivided for more accurate assessment of internal rotation.  相似文献   
47.
48.
49.
Our previous studies showed the possibility that oxidative stress, including oxidative DNA damage, is involved in the mechanism of dicyclanil (DC)-induced hepatocarcinogenesis at the preneoplastic stage in mice. In this study, the expression analyses of genes, including oxidative stress-related genes, were performed on the tissues of hepatocellular tumors in a two-stage liver carcinogenesis model in mice. After partial hepatectomy, male ICR mice were injected with N-diethylnitrosamine (DEN) and given a diet containing 0 or 1500 ppm of DC for 20 weeks. Histopathological examinations revealed that the incidence of hepatocellular tumors (adenomas and carcinomas) significantly increased in the DEN + DC group. Gene expression analysis on the microdissected liver tissues of the mice in the DEN + DC group showed the highest expression levels of oxidative stress-related genes, such as Cyp1a1 and Txnrd1, in the tumor areas. However, no remarkable up-regulation of Ogg1-an oxidative DNA damage repair gene-was observed in the tumor areas, but the expression of Trail-an apoptosis-signaling ligand gene-was significantly down-regulated in the tumor tissues. These results suggest the possibility that the inhibition of apoptosis and a failure in the ability to repair oxidative DNA damage occur in the hepatocellular DC-induced tumors in mice.  相似文献   
50.
Most female moths produce species-specific sex pheromone blends in the modified epidermal pheromone gland (PG) cells generally located between the 8 and 9th abdominal segments. The biosynthesis is often regulated by pheromone biosynthesis activating neuropeptide (PBAN) either in or prior to de novo fatty acid synthesis or at the formation of oxygenated functional group. In Pseudaletia separata, information about life span, calling, PG morphology, daily fluctuation of pheromone production and its hormonal regulation is limited.We measured pheromone titer daily (16:8; L:D) at 2 h intervals in scotophase. Blend ratio stabilized during the 2nd day (till 4-5th) at 6th hour of scotophase, with the ratio of 27.5:12.8:44.4:15.3 for Z-11-16OH:16OH:Z-11-16Ac:16Ac, respectively. Females showed calling behavior from this time. We found with light and fluorescence microscopy that PG consisted of intersegmental membrane (A part), and dorso-lateral region of 9th abdominal segment (B part), encountering for ∼35% of total production revealed by gas chromatography. Ratios did not reveal difference. We did not find precursor (triacylglycerols) accumulation in form of lipid droplets, implying that PBAN stimulates de novo biosynthesis of 16:acyl precursors. In vivoHez-PBAN injections (1-3 × 5 pmol, 2 h intervals) into 3 days old 16-18 h decapitated females stimulated pheromone production, both in A and B parts. Blend analyses including ratios suggest stimulation of the initial phase of synthesis, but desaturation of fatty acyl intermediates do not follow proportionally. More saturated fatty acid is converted from the available pool to the final OH and Ac, compared to females kept intact in scotophase. In vitro studies (PGs incubated 4-6 h in the presence of 0.25 or 0.5 μM Hez-PBAN, especially with surplus 2 mM malonyl-CoA) revealed higher saturated component ratio than the unsaturated, compared to natural blend or in vivo injections.  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