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   1933篇
  免费   103篇
  国内免费   14篇
耳鼻咽喉   15篇
儿科学   49篇
妇产科学   12篇
基础医学   209篇
口腔科学   33篇
临床医学   163篇
内科学   561篇
皮肤病学   75篇
神经病学   146篇
特种医学   25篇
外科学   268篇
综合类   8篇
预防医学   79篇
眼科学   14篇
药学   230篇
中国医学   3篇
肿瘤学   160篇
  2021年   27篇
  2020年   16篇
  2019年   26篇
  2018年   29篇
  2017年   27篇
  2016年   26篇
  2015年   25篇
  2014年   41篇
  2013年   63篇
  2012年   83篇
  2011年   80篇
  2010年   43篇
  2009年   45篇
  2008年   78篇
  2007年   96篇
  2006年   108篇
  2005年   97篇
  2004年   95篇
  2003年   84篇
  2002年   90篇
  2001年   82篇
  2000年   69篇
  1999年   76篇
  1998年   34篇
  1997年   27篇
  1996年   26篇
  1995年   16篇
  1994年   15篇
  1993年   14篇
  1992年   51篇
  1991年   43篇
  1990年   49篇
  1989年   35篇
  1988年   40篇
  1987年   22篇
  1986年   30篇
  1985年   39篇
  1984年   27篇
  1983年   23篇
  1981年   6篇
  1979年   23篇
  1978年   12篇
  1977年   11篇
  1976年   8篇
  1973年   6篇
  1971年   8篇
  1969年   14篇
  1968年   6篇
  1967年   10篇
  1966年   8篇
排序方式: 共有2050条查询结果,搜索用时 31 毫秒
1.
During the last 5 years, 5 cases of traumatic diaphragmatic rupture were surgically treated. These cases were reported and the literature concerning traumatic diaphragmatic hernia in the last one decade in Japan, including 80 cases was studied. The purpose of this study is to discuss the most important early diagnostic tools and to consider the choice of incision and approach. The following two results were gotten. (1) Plain chest X-ray, computed tomography and ultrasonography were the most valuable diagnostic tools. (2) The choice of incision and approach depends on the stage at which the rupture is recognized (early or late), the site of rupture and associate injuries.  相似文献   
2.
B M Psaty  T D Koepsell  J P LoGerfo  E H Wagner  T S Inui 《JAMA》1989,261(14):2087-2094
We conducted a population-based, case-control study to determine whether beta-blockers, used for the treatment of hypertension, prevent first events of coronary heart disease. Cases were patients who had high blood pressure treated with medicines and who presented in 1982 to 1984 with angina or fatal or nonfatal myocardial infarction. Controls were a probability sample of health maintenance organization patients with pharmacologically treated hypertension and free of coronary heart disease. Blinded to case-control status, we reviewed the medical records of the 248 cases and 737 controls. The health maintenance organization's computerized pharmacy database was used to ascertain the use of beta-blockers. Fewer cases than controls were taking beta-blockers. This difference was confined to those with nonfatal infarctions. After adjustment for confounding, the estimated relative risk was 0.62 (95% confidence interval, 0.39 to 0.99). Higher doses of beta-blockers conferred greater protection. We conclude that beta-blockers may prevent first events of nonfatal myocardial infarction in patients with high blood pressure.  相似文献   
3.
A 10-year-old girl with autoimmune hepatitis (AIH) was reported. She was admitted to our hospital because of cholestasis and elevation of liver enzymes for 2 months. Laboratory examination revealed that EBV-DNA copy number in the PBMNC (peripheral mononuclear cells) was 1.2 x 10(3) copies/microg of DNA, hypergammaglobulinemia, and positive antinuclear antibody, positive anti-smooth muscle antibody. The histology of her liver biopsy specimen revealed interface hepatitis, dense mononuclear cell infiltrates, mild fibrosis, and negative for EBV in situ hybridization assay indicating AIH and not EBV-associated hepatitis. She was treated firstly with methylprednisolone pulses, then will prednisolone p.o.+azathioprine p.o.. Intravenous cyclophosphamide pulse therapy was introduced because of her abnormal immune pathology. All abnormal laboratory parameters improved to normal levels within 2 months, and EBV-DNA copy number in the PBMNC became negative after 4 months. The histology of liver biopsy specimen was useful for the diagnosis of AIH in such a difficult case needed to be differentiated from EBV hepatitis.  相似文献   
4.
The purpose of this study was to determine the effect of pulsatile flow on cerebral perfusion under cardiopulmonary bypass (CPB). Twenty-three patients who underwent cardiac operations were divided into two comparable groups: Group A (N = 11) had standard nonpulsatile flow, while in Group B (N = 12), a pulsatile pump was used. The blood flow of left common carotid artery and radial arterial pressure were continuously monitored during cardiac operation in both groups and cerebral vascular resistance was calculated. In Group B, the perfusion pressure of left common carotid artery was monitored and compared with that of radial artery. Arterial and internal jugular venous blood were sampled and the difference of cerebral A.V O2 contents and cerebral oxygen consumption was calculated. Cerebral vascular resistance in Group B (54.0 +/- 11.2% of the value of before-CPB) significantly decreased compared to that in Group A (72.2 +/- 11%) at the end of CPB (p less than 0.05). Pulse pressure following pulsatile CPB flow was 15.1 +/- 5.8 mmHg monitored in radial artery and it reduced to 8.5 +/- 5 mmHg in left common carotid artery. Although there was no significant difference in cerebral oxygen consumption of both groups during and just after CPB, the difference of cerebral A-V O2 contents of Group B was greater than Group A just after CPB. These data suggest that pulsatile flow may minimize the cerebral microcirculatory shunt during CPB, resulting from the reduction of cerebral vascular resistance.  相似文献   
5.
Temporal Delta Wave and Ischemic Lesions on MRI   总被引:1,自引:1,他引:0  
Abstract: The present study was designed to determine the clinical significance of a temporal low-voltage irregular delta wave (TLID) on EEG. Among 808 EEG records examined during one year at our hospital, the TLID was commonly detected in patients with clinically diagnosed ischemic brain diseases such as multiple infarction. Subsequently, a relation of the TLID to ischemic lesions on MRI was examined in 50 elderly depressive patients. It was found that there was a close correlation between the occurrence of the TLID and small ischemic lesions on MRI (p<0.001). These results suggest that the TLID is a valuable indicator of minor ischemic changes of the brain.  相似文献   
6.
The possible roles of cytochrome P450 (P450) enzymes in the metabolic activation of N-nitrosodimethylamine (NDMA) and N-nitrosodiethylamine (NDEA) by rat liver microsomes have been examined in a system containing the bacterial tester strain Salmonella typhimurium NM2009, a newly developed strain showing high O-acetyltransfer activities. The DNA-damaging activity could be determined by measuring expression of the umu gene in a plasmid containing the fused umuC-lacZ gene construct in the bacteria. The following lines of evidence support the view that both NDMA and NDEA are principally oxidized to reactive products by P450 2E1 in rat liver microsomes. First, NDMA and NDEA were activated by rat liver microsomes in a protein- and substrate-dependent manner and the former chemical was more active than the latter; both activities were induced in rats treated with P450 2E1 inducers such as ethanol, acetone and isoniazid and by starvation. Second, activation of NDMA and NDEA were both inhibited significantly by antibodies raised against rat P450 2E1 and by P450 2E1 inhibitors such as diethyldithiocarbamate and 4-methylpyrazole in rat liver microsomes. Finally, in reconstituted monooxygenase systems containing purified rat P450 enzymes, P450 2E1 gave the highest rates of the activation of both NDMA and NDEA; the addition of rabbit cytochrome b5 to the system caused about a 1.5-fold increase in both reactions. In separate experiments we also found that N-nitrosomethylacethoxymethylamine, a compound that reacts with DNA after ester cleavage, is more genotoxic in S.typhimurium NM2009 than in S.typhimurium NM2000, a strain that is defective in O-acetyltransferase activity. Part of the pathway involved in the activation of nitrosamines is suggested to be acetylation of alkyldiazohydroxides formed by P450 or acetylesterase, because the genotoxic activity of N-nitrosomethylacethoxymethylamine in S.typhimurium NM2009 could be inhibited by the O-acetyltransferase inhibitor pentachlorophenol. These results indicate that NDMA and NDEA are oxidized to gentoxoic products by rat liver microsomes and that a P450 2E1 enzyme plays a major role in the activation of these two potent carcinogens. The activation pathway of N-nitrosodialkylamines through acetylation by O-acetyltransferase has been proposed. This simple bacterial system for measuring genotoxicity should facilitate studies on the activation of N-nitroso alkylamines.  相似文献   
7.
Using a new instrument designed by the Authors having two cannulas to allow filling of a contrast medium exclusively in the cervical canal and uterine cavity, selective hysterography was performed for 22 cases of endometrial carcinoma. This method was useful not only for evaluation of the size, location and growth patterns but also for estimation of the cervical involvement of endometrial carcinoma.  相似文献   
8.
STUDY OBJECTIVE: To determine the predictive validity of the American Board of Internal Medicine (ABIM) certification process. DESIGN: Prospective measurement of the knowledge, skills, and attitudes of 185 ABIM-certified and 74 noncertified internists by a written examination; evaluation by professional associates; a patient questionnaire assessing satisfaction with care, physician's counseling role, and preventive care; and review of records of patients with common illnesses. SUBJECTS: Practicing internists who completed training or received ABIM certification 5 to 10 years previously. SETTING: Office-based practices in six western states. RESULTS OF DATA ANALYSIS: Physicians certified by the ABIM had significantly higher scores on the written examination than the noncertified physicians, and scores on our examination correlated highly with the ABIM certification examination (r = 0.73). Ratings of clinical skills by professional associates were significantly higher for certified internists and also correlated highly with ABIM examination scores (r = 0.53 to 0.59). Regression analysis showed that ABIM certification status was the major variable affecting performance on these measures of clinical competence. Results from other measures did not show many differences between certified and noncertified physicians in the care of patients with common illnesses, but modest differences in preventive care and a few differences in outcome favored the certified physicians. CONCLUSIONS: Comparison of findings from the written examination and the professional associate ratings with certification status and original ABIM certification examination scores shows predictive validity of ABIM certification. Further studies are needed to determine if certification status predicts important differences in the care of patients with complex illnesses.  相似文献   
9.
Effects of urine pH on the renal tubular secretion of an organic cation (tetraethylammonium, TEA) and an organic anion (p-aminohippurate, PAH) were investigated using the isolated erythrocyte-perfused rat kidney. The method was based on a multiple indicator dilution experiment and noncompartmental moment analysis. Treatment with sodium bicarbonate and sodium dihydrogen phosphate increased and decreased urine pH, respectively, but affected neither the condition of the perfused kidney nor the renal handling of albumin and inulin. In TEA studies, the increase of urine pH prolonged the mean residence time in renal epithelial cells (T cell) and reduced the apparent secretion intrinsic clearance, but did not influence the volume of distribution in the kidney (Vd drug). The decrease of urine pH did not affect these kinetic parameters. By contrast, PAH secretion was constant against the change of urine pH. Since any change in the basolateral membrane transport is reflected in Vd drug, the net transport from blood to cells can be regarded as similar under these treatments. On the other hand, the prolonged T cell of TEA with the increased urine pH suggested a slow transport from cells to lumen across the brush-border membranes. The present results coincide with the hypothetical mechanism that organic cations are secreted via an active transport system, coupled to the countertransport of H+ into cells. In conclusion, the present method is useful to separately evaluate the transmembrane transport across both sides of the renal epithelial cells in a morphologically intact kidney.  相似文献   
10.
In our previous study, we demonstrated that high-dose 60Co irradiation was able to prevent rejection of canine tracheal allografts. To determine the maximum possible length of these grafts, in the present study we attempted to transplant five-ring and ten-ring tracheal allografts in two groups of five dogs each. Either five or ten rings were excised from donor tracheas and irradiated with 100,000 cGy of 60Co. The irradiated tracheal grafts were transplanted to replace either five- or ten-ring sections of the mediastinal tracheas removed from the recipient dogs. The grafts were covered with omental pedicles and no immunosuppressants were used. Graft incorporation was achieved in four of the five dogs in the five-ring group, and three of these dogs survived for more than 700 days. However, four of the five animals in the ten-ring group died from tracheostenosis accompanied by ischemia within 3 weeks. These findings demonstrate the impossibility of performing ten-ring tracheal allotransplantation using irradiated grafts, even with omentopexy.  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