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   15029篇
  免费   601篇
  国内免费   60篇
耳鼻咽喉   136篇
儿科学   303篇
妇产科学   302篇
基础医学   1818篇
口腔科学   272篇
临床医学   926篇
内科学   4052篇
皮肤病学   202篇
神经病学   1084篇
特种医学   420篇
外科学   2687篇
综合类   58篇
预防医学   430篇
眼科学   213篇
药学   1369篇
中国医学   27篇
肿瘤学   1391篇
  2022年   148篇
  2021年   219篇
  2020年   127篇
  2019年   162篇
  2018年   186篇
  2017年   178篇
  2016年   211篇
  2015年   206篇
  2014年   304篇
  2013年   390篇
  2012年   594篇
  2011年   713篇
  2010年   368篇
  2009年   354篇
  2008年   618篇
  2007年   653篇
  2006年   660篇
  2005年   657篇
  2004年   727篇
  2003年   717篇
  2002年   734篇
  2001年   486篇
  2000年   470篇
  1999年   440篇
  1998年   248篇
  1997年   185篇
  1996年   136篇
  1995年   131篇
  1994年   129篇
  1993年   125篇
  1992年   383篇
  1991年   321篇
  1990年   327篇
  1989年   347篇
  1988年   336篇
  1987年   316篇
  1986年   275篇
  1985年   225篇
  1984年   202篇
  1983年   162篇
  1982年   89篇
  1980年   71篇
  1979年   158篇
  1978年   98篇
  1977年   81篇
  1975年   92篇
  1972年   77篇
  1971年   86篇
  1969年   75篇
  1968年   69篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
32.
We implanted normal peripheral blood lymphocytes (PBL) from healthy donors and splenic tissues from patients with gastric cancers into the severe combined immunodeficient (SCID) mouse, demonstrating that SCID mouse with splenic tissue can produce a high level of human immunoglobulin G (IgG). The normal PBLs at 10(7) and 10(8)/mouse were implanted intraperitoneally, and three splenic tissues with a size of 3 x 3 x 3 mm from gastric cancer patients were inoculated subcutaneously into the bilateral backs of the mice. At 2, 4, 6 and 8 weeks after inoculation, mice were killed, and the human IgG was assessed by an ELISA method. SCID mice with splenic tissue revealed high human IgG levels from 2 weeks after inoculation and approximately 2 mg of IgG per ml was observed at 8 weeks post-implantation, while the IgG levels in mice treated with PBLs were limited. Since the half life of the extrinsic human IgG was 10.2 days, the high level of human IgG in the SCID mice was supposed to be produced by human plasma cells in the splenic tissue from gastric cancer patients. This model was thought to be adequate for evaluating human immunological functions in vivo.  相似文献   
33.
There is no definitive surgical procedure for acquired lesions of the tricuspid valve (TV). From Feb, 1978, through March, 1990, the surgical treatment for the organic lesions of TV was performed in 10 patients, repair in 6 and TV replacement in 4. TV was repaired by commissurotomy, annuloplasty or valvuloplasty, or combination of them. When residual significant tricuspid regurgitation (TR) and/or stenosis (TS) was detected by intraoperative pulsed Doppler echocardiography after reparative procedures, TV was replaced. Follow-up periods ranged from 1 to 12 years (mean, 45.3 months). There was no early death, and late death was noted in one patient 32 months after operation. Preoperatively, 7 patients were in NYHA class IV and 3 in class III. Out of survivors, 7 are in class I and 2 in class II because of progression of mitral stenosis or coronary artery disease. Following surgery, the patients exhibited significant decrease in the cardiothoracic ratio (69.3 +/- 7.2 to 56.9 +/- 6.4%; p less than 0.01) and in the mean right atrial pressure (11.4 +/- 3.6 to 8.6 +/- 3.1 mmHg; p less than 0.05). The postoperative right ventriculography showed mild to moderate TR in 3 of 6 patients who underwent TV repair. In conclusion, TV repair could be a reasonable procedure for the organic TV lesions, although careful follow-up is recommended for residual TR.  相似文献   
34.
The fiber type composition of the soleus muscle was investigated in male Sprague-Dawley rats exposed to hypobaric hypoxia of 460 mm Hg from 5 to 12 weeks of age. The muscle fibers were classified as fast-twitch oxidative (FO) and slow-twitch (S) on the basis of adenosine triphosphatase (ATPase) and succinate dehydrogenase (SDH) reactions. Intermediate fibers (INT) with intermediate ATPase and high SDH reaction intensities were also examined. A type shift of muscle fibers from FO to INT and S was found in the control group during development. After exposure to hypoxia, the hypoxia group had a significantly greater percentage of FO fibers than the age-matched control group. There was no significant change in the total number of fibers in the muscle during development and after exposure to hypoxia. These results indicate that the increased percentage of FO fibers found in the developing rat under hypoxic conditions is due to a hypoxia-induced inhibition of the type shift of muscle fibers from FO to S during development.  相似文献   
35.
The effects of NG-nitro-L-arginine methyl ester (L-NAME), the nitric oxide (NO) synthase inhibitor, on gastric HCO3- secretion were examined in anesthetized rats. Intravenous administration of L-NAME (1, 2.5, 5 mg/kg) increased HCO3- secretion in a dose-related manner. This effect of L-NAME was mimicked by NG-mono-methyl-L-arginine (50 mg/kg, i.v.) and was antagonized significantly by concurrent administration of L-arginine but not D-arginine (200 mg/kg, i.v.). These results indicate that gastric HCO3- secretion is stimulated by inhibition of NO biosynthesis.  相似文献   
36.
We did 18 arthrodeses of the wrist in 16 patients with rheumatoid arthritis using an intramedullary fixation technique. There were 15 women and one man, whose ages at operation ranged from 47 to 71 years (mean 58). Follow up ranged from 13 to 68 months (mean 27). The operative technique consists of a combination of intramedullary placement of two Kirschner (K)-wires and an autogenous bone graft. At follow up bony union was apparent in all cases. K-wires came out of the metacarpal joints in two cases. Paraesthesiae in the median nerve distribution occurred in two cases which both recovered within three months.  相似文献   
37.
The CA-50 enzyme immunoassay kit (EIA kit) that has been developed with the use of C-50 monoclonal antibody prepared by L. Lindholm et al. was evaluated for diagnosis of human cancer. The levels of CA-50 in the sera were determined using this kit supplied from Mitsui Pharmaceuticals, Inc. Co. in 759 healthy donors, 728 patients with benign disease and 1,263 untreated patients with cancer. A CA-50 concentration of 40 U/ml of serum was used as the cut-off value. Patients with pancreatic cancer and patients with bile duct cancer had high positive incidence of 75% and 68%, respectively, compared with a low positive incidence of under 40% in patients with other cancers. On the other hand, positive rates in patients with benign disease were as low as 13%. Comparison of the serum levels of CA-50 with CA19-9 in the same samples did not exhibit complete positive correlation in patients with pancreatic cancer, patients with bile duct cancer and patients with liver cancer. These findings indicated that C-50 antibody reacted with two epitopes of CA19-9 and sialosyllactotetraose. From the above results, the usefulness of CA-50 as a tumor marker for pancreatic cancer and bile duct cancer was recognized with this EIA kit.  相似文献   
38.
To examine species differences in the distribution pattern of guanosine triphosphate (GTP)-binding protein (Go) within the vertebrate retina, paraffin-embedded retinae from a number of vertebrate species, including the goldfish, frog, turtle, chicken, monkey, and human, were immunohistochemically stained with affinity-purified antibody against the alpha-subunit of Go. Go-immunoreactive products were found to be located in the neuropil, but not in the cell bodies of neurons, in the retina of all these species. However, some species differences were observed. In the frog, monkey and human, the inner plexiform layer (IPL) was homogeneously stained with this antibody, but in the goldfish, turtle and chicken, the IPL was heterogeneously stained. In the frog, chicken, turtle and human, the outer plexiform layer (OPL) was densely stained with this antibody, but in the goldfish and monkey, the OPL was rather faintly immunoreactive to the antibody. In the goldfish, monkey and human, the outer nuclear layer (ONL) was not immunoreactive to the Go-antibody, whereas in the frog, turtle and chicken, the ONL was immunoreactive to it. The implications of these species differences in Go localization in the vertebrate retina are discussed.  相似文献   
39.
To assess the pathophysiological role of atrial natriuretic factors in the regulation of blood pressure, we studied the effect of chronic infusion of a synthetic atrial natriuretic factor of 25 amino-acid residues on blood pressure and sodium-water excretion. Experimental subjects were rats with hypertension made by chronic infusion of vasopressin on regular intakes of sodium or on sodium loading with 1% NaCl as drinking water. When a subdepressor dose (150 micrograms/kg/day) of synthetic atrial natriuretic factor was delivered via an osmotic minipump into the jugular vein simultaneously with 7.2 U/kg/day of vasopressin infused intraperitoneally by another osmotic minipump, the expected elevation of systolic blood pressure was completely inhibited. This was not accompanied by any changes in urine volume and urinary sodium excretion. The antihypertensive effect was sustained throughout the experimental period lasting 3 days in rats on regular sodium intake (p less than 0.01) or on sodium loading with 1% NaCl as drinking water (p less than 0.01). These results indicate that a subdepressor dose of synthetic atrial natriuretic factor can modulate the vasopressor effect of vasopressin. Therefore it is suggested that an atrial natriuretic factor may be involved in the regulation of blood pressure via its antagonizing effect to vasopressin.  相似文献   
40.
OBJECTIVE AND DESIGN: JTE-607, a multiple cytokine inhibitor, was evaluated in lipopolysaccharide (LPS)-induced acute lung injury in rats in vivo and in vitro. MATERIALS AND METHODS: LPS instillation into airways of rats was performed. JTE-607 at 3-30 mg/kg and dexamethasone at 3 mg/kg were administered intravenously at 10 min and 0 min for JTE-607, and 60 min for dexamethasone prior to the LPS instillation (n = 8). Cytokine-induced neutrophil chemoattractant (CINC)-1 level and myeloperoxidase (MPO) activity in lung were measured at 4 h after LPS instillation, and at 24 h for lung wet weight measurement and histological study. LPS-induced CINC-1 production by rat alveolar macrophages were also measured in vitro. RESULTS: JTE-607 and dexamethasone showed a significant reduction of increased CINC-1 level and MPO activity in lung after LPS treatment in vivo. Increased wet weight was also significantly inhibited. Histological studies revealed that JTE-607 and dexamethasone significantly inhibited LPS-induced accumulation of peribronchial neutrophils and eosinophils, and perivascular edema. JTE-607 and dexamethasone suppressed CfNC-1 synthesis by rat alveolar macrophages in vitro with IC50 values of 12.4 microM and 2.3 nM, respectively. CONCLUSIONS: These results indicate that JTE-607 has an inhibitory effect on LPS-induced rat lung inflammation in parallel with CINC-1 reduction. The effect of JTE-607 was suggested to be through direct inhibition of CINC-1 production from rat alveolar macrophages. JTE-607 may thus be efficacious in cytokine-mediated lung inflammation such as acute respiratory distress syndrome.  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