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   9137篇
  免费   410篇
  国内免费   47篇
耳鼻咽喉   63篇
儿科学   141篇
妇产科学   110篇
基础医学   1073篇
口腔科学   211篇
临床医学   609篇
内科学   2201篇
皮肤病学   199篇
神经病学   598篇
特种医学   361篇
外科学   1593篇
综合类   33篇
预防医学   309篇
眼科学   71篇
药学   1068篇
中国医学   22篇
肿瘤学   932篇
  2023年   30篇
  2022年   70篇
  2021年   172篇
  2020年   78篇
  2019年   106篇
  2018年   161篇
  2017年   129篇
  2016年   132篇
  2015年   133篇
  2014年   187篇
  2013年   226篇
  2012年   381篇
  2011年   454篇
  2010年   261篇
  2009年   230篇
  2008年   414篇
  2007年   473篇
  2006年   442篇
  2005年   468篇
  2004年   402篇
  2003年   425篇
  2002年   448篇
  2001年   375篇
  2000年   394篇
  1999年   340篇
  1998年   111篇
  1997年   93篇
  1996年   84篇
  1995年   69篇
  1994年   72篇
  1993年   62篇
  1992年   243篇
  1991年   238篇
  1990年   234篇
  1989年   216篇
  1988年   211篇
  1987年   186篇
  1986年   178篇
  1985年   181篇
  1984年   98篇
  1983年   82篇
  1982年   40篇
  1981年   28篇
  1980年   26篇
  1979年   69篇
  1978年   35篇
  1977年   18篇
  1976年   12篇
  1975年   12篇
  1969年   10篇
排序方式: 共有9594条查询结果,搜索用时 156 毫秒
31.
Time density curve (TDC) can be reconstructed from the data of intravenous digital subtraction angiography (IVDSA). We evaluated peak time (PT) and modal transit time (MOTT) of the TDC as the probable indicator of cerebral intravascular blood flow. Cerebral IVDSA and single photon emission CT (SPECT) were performed on 12 patients of ischemic cerebrovascular disease, which consisted of 3 internal carotid artery (ICA) occlusions, one middle cerebral artery (MCA) occlusion, one anterior cerebral artery (ACA) branch occlusion and 7 lacunar infarctions. We classified former 4 patients as occlusion group and latter 8 as reference group. In 3 patients (2 ICA and one MCA occlusions), SPECT study revealed definite hypoaccumulation in the MCA territory of occlusive side. Two regions of interest (ROI) were placed on the territories of right and left middle cerebral arteries in the frontal view of cerebral IVDSA. Digital data processor fitted gamma curve to the TDC of each ROI, and calculated PT and MOTT. The absolute lateralities of PT and MOTT of MCA territory was significantly (p less than 0.05) larger in occlusion group than reference group. Patients with hypoaccumulation in SPECT had significantly (p less than 0.02) larger laterality of MOTT than patients with isoaccumulation. One ICA occluded patient without hypoaccumulation in corresponding MCA territory had relatively small laterality of MOTT similar to the patients of ACA branch occlusion and lacunar infarction. These results suggest that PT and MOTT are possible to detect the laterality of the intravascular blood flow in MCA territories caused by major artery occlusion.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
32.
The effects of (6)-shogaol, a pungent component of dried ginger with a capsaicin-like chemical structure, on the release of immunoreactive substance P from the spinal dorsal horn were examined by in vitro superfusion of the dorsal-half slices of the spinal cord of the rat. (6)-Shogaol (30 microM to 1 mM) increased dose-dependently the release of immunoreactive substance P. The maximum effect of (6)-shogaol was observed at a concentration of 100 microM and less than a half of the effect of 10 microM capsaicin. The effect of (6)-shogaol (100 microM) was attenuated in slices from rats with dorsal rhizotomy and abolished by elimination of calcium ions from the perfusion medium. Pretreatment with (6)-shogaol in vitro inhibited the capsaicin-evoked release of immunoreactive substance P. On the other hand, systemic administration of (6)-shogaol (160 mg/kg) produced antinociception in rats, with a peak effect between 15 and 30 min and a smaller dose of 80 mg/kg was without effect. Treatment of rats with (6)-shogaol, at a dose of 160 mg/kg but not at 80 mg/kg, for 20 min significantly decreased release of immunoreactive substance P, evoked by capsaicin (10 microM), from the slices of cord. These data suggest that (6)-shogaol shares the sites of action with capsaicin, on the terminals of substance P-containing primary afferents, to release of the neuropeptide and inhibit the release of substance P, by subsequent stimulation of the primary afferents. The latter action of (6)-shogaol might be relevant to its analgesic effect.  相似文献   
33.
Electrogastrograms (EGGs) were recorded in patients both before and after receiving proximal gastrectomy plus jejunal interposition (PGJI) or just after receiving total gastrectomy plus jejunal interposition (TGJI). Intraluminal pressure was also recorded in some postoperative patients. The EGG 3 cpm component (2.5-4.9 cpm) remained after PGJI, but subsequently decreased with a significant reduction in the preoperative to postoperative ratio of the 3 cpm components (P<0.05). The mean frequency of the 3 cpm components increased significantly after PGJI (P<0.05) and its instability factor increased. The EGG 10 cpm components became relatively dominant compared to other frequency components in 2 out of 8 of patients having PGJI but the mean amplitude of 10 cpm decreased. In TGJI patients, only the 10 cpm component was conspicuous in EGG as in the case of total gastrectomy and Roux en Y anastomosis procedures. The spectral frequencies of intraluminal pressure in the interposed jejunum were similar to the EGG of 10 cpm components both in the case of PGJI and TGJI patients. In conclusion, surface EGG could record the electrical activities of the interposed jejunum more easily in patients having had TGJI than in PGJI.  相似文献   
34.
Serial DWIs were performed in a patient with CJD who developed symptoms acutely and progressed rapidly. DWI discloed an increased signal in the frontal and parietal inner cortical areas, and in the caudate nuclei and putamina 20 days after the onset of symptoms. T2-weighted images showed only signal abnormality in the caudate nuclei and putamina, but not in the cerebral cortex. In the CSF obtained 15 days after the onset of symptoms, total tau protein was markedly elevated and 14-3-3 protein was positive. Measurement of these proteins are highly specific and sensitive for the diagnosis of CJD, but not available as a rapid routine examination at present. DWI is not specific, but useful for making the diagnosis of CJD in the early stage of the disease.  相似文献   
35.
36.
A 64-year-old female was found to have localized ground-glass opacity (GGO) in the middle lobe on a chest computed tomography (CT) for screening. Middle lobectomy with video-assisted thoracoscopic surgery (VATS) was undertaken, and pathological diagnosis was a bronchioloalveolar carcinoma (BAC) in stage IA. A follow-up CT a year following the surgery revealed localized GGO in area S6 of the left lung. However, it disappeared during the gravitation-dependent gradient in the observation period. The patient was scanned again under prone position to exclude the gravitational effect, resulting in definite detection of the GGO. Left extended S6 segmentectomy with VATS was performed, and pathological diagnosis was a BAC in stage IA. As GGO existing in a gravitation-dependent area may be masked by the gravitation-dependent density, a change of the scanning position may lead to a proper detection of the tumor for the diagnosis of BAC.  相似文献   
37.
38.
Background The purpose of this study was to examine the effects of bacterial suporantigens, which can derange the immune response and contribute to the renal lesions of immunoglobulin A (lgA) nephropathy. Methods Twenty-five micrograms of a bacterial superantigen, staphylococcal enterotoxin B (SEB), was injected into IgA nephropathy-prone ddY mice intrathymically when they reached 6 weeks of age. Evaluation included measurement of albumin excretion in urine, immunoglobulin concentration, and lymphokine production in vitro, as well as analysis of T-cell receptor expression in splenic T-cell subsets and examination of renal histology by light and fluorescence microscopy. Results At 40 weeks of age, the serum level of IgA in these mice was substantially increased and the number of Vβ8+ CD4+splenic T-cells was significantly decreased compared with measurements in untreated controls. Both control and SEB-treated mice excreted less than 30 μg/mL of urinary albumin. In mice given SEB, the amount of interleukin 2 (IL-2) and tumor necrosis factor-α (T helper 1 [Th1]-type cytokines) produced by the in vitro-stimulated lymphocytes significantly decreased. whereas that of interleukin 4 (IL-4) and interleukin 6 (IL-6) (Th2-type cytokines) markedly increased compared with measurements in control mice. At 40 weeks of age, mice given SEB showed marked glomerular hypercellularity and enhanced glomerular C3 deposition by renal histology, compared with control mice. Conclusion These results suggest that bacterial superantigen SEB may modify glomerular lesions through activating Th2 cells, while inducing deletion of Th1 cells in this experimental model.  相似文献   
39.
A patient, an 80-year-old female, had complained of a cough for 20 weeks, and was not cured by cough medicine. Gastroesophageal reflux was considered as the cause of the cough because of her symptoms and gastrointestinal fiberscopy (GIF) and barium meal studies. She made favorable progress on a histamine H2 blocker and cysapurid for 4 weeks. Therefore we diagnosed her cough as caused by gastroesophageal reflux. We also studied the incidence of chronic persistent cough in patients suspected of gastroesophageal reflux because of symptoms and GIF results. Among 676 cases examined by GIF at Niigata-kenritsu Myoko Hospital, we detected 7 cases who complained of heartburn and in whom we observed hiatal hernia and reflux esophagitis by GIF. Only one of them, the present case, complained of a cough. CPC caused by gastroesophageal reflux is not seen frequently, but the possibility of GER as the cause of CPC should be considered.  相似文献   
40.
Mercury (Hg) and selenium (Se) levels were determined for erythrocytes, plasma and urine of 25 male and 29 female workers exposed to elemental mercury (Hgo) vapor. Interrelationship between the Hg levels and the Se levels was examined by the correlational analysis and the stepwise regression analysis. Indicators of Se status (erythrocyte Se levels, plasma Se levels and urinary Se levels) were closely intercorrelated; similarly, indicators of exposure to Hgo vapor (erythrocyte inorganic Hg levels, plasma Hg levels and urinary Hg levels) were significantly intercorrelated. Since plasma Hg level was one of the significant independent variables in determining the erythrocyte Se and plasma Se levels, Hgo vapor exposure was thought likely to influence the Se metabolism in workers. None of the Se status indicators were significant as determinants of the indicators of Hgo vapor exposure.  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