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   213196篇
  免费   18434篇
  国内免费   4700篇
耳鼻咽喉   3279篇
儿科学   4123篇
妇产科学   3622篇
基础医学   17357篇
口腔科学   7337篇
临床医学   19512篇
内科学   20524篇
皮肤病学   2484篇
神经病学   10550篇
特种医学   5806篇
外国民族医学   11篇
外科学   20482篇
综合类   33868篇
现状与发展   10篇
一般理论   24篇
预防医学   28803篇
眼科学   2019篇
药学   20581篇
  339篇
中国医学   26068篇
肿瘤学   9531篇
  2024年   963篇
  2023年   4274篇
  2022年   8052篇
  2021年   10597篇
  2020年   10269篇
  2019年   11541篇
  2018年   10196篇
  2017年   8758篇
  2016年   7824篇
  2015年   7264篇
  2014年   14290篇
  2013年   14564篇
  2012年   12783篇
  2011年   13657篇
  2010年   11018篇
  2009年   9535篇
  2008年   8861篇
  2007年   8945篇
  2006年   7622篇
  2005年   6425篇
  2004年   5310篇
  2003年   4778篇
  2002年   3703篇
  2001年   3088篇
  2000年   2730篇
  1999年   2232篇
  1998年   1797篇
  1997年   1636篇
  1996年   1331篇
  1995年   1257篇
  1994年   1165篇
  1993年   1026篇
  1992年   929篇
  1991年   862篇
  1990年   751篇
  1989年   743篇
  1988年   679篇
  1987年   607篇
  1986年   569篇
  1985年   1825篇
  1984年   2076篇
  1983年   1302篇
  1982年   1735篇
  1981年   1203篇
  1980年   1031篇
  1979年   917篇
  1978年   747篇
  1977年   563篇
  1976年   701篇
  1975年   480篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
In Kobe University Hospital, a new method for endoscopic mucosal resection (EMR) using insulated‐tip electrosurgical knife (IT‐EMR) for early gastric cancer (EGC) was introduced from November 2001. To achieve an effective and safe IT‐EMR procedure, we use a high‐frequency surgical unit for cutting and coagulation (ERBOTOM ICC 200) with automatically controlled cutting mode (ENDOCUT). In this study, we show not only our results of IT‐EMR for EGC in comparison with those of the conventional strip biopsy method, but also the optimal conditions for the apparatus of a high‐frequency surgical unit to prevent complications such as bleeding and perforation.  相似文献   
52.
目的评价牙冠延长术在牙体缺损达龈下的残根残冠修复中的临床疗效。方法自2004年5月至2005年6月,对32例患者的36颗牙体缺损达龈下的患牙,术前按断端位于龈下最深距离分为A组(20颗患牙,距离<3.0mm)和B组(16颗患牙,3.0mm≤距离≤4.0mm),均采用牙冠延长术暴露龈下牙体断面,术后6周行桩冠修复。分别记录和比较手术前、后牙周探诊深度(PD)、菌斑指数(PLI)、龈沟出血指数(SBI)和牙齿松动度,以观察临床疗效。结果术后随访患者6个月,两组病例术后6周牙体断端均暴露较好、龈缘颜色正常,术后修复效果有效率为100%,满意率为77.78%。A组术后无松动,修复效果满意;B组术后50.00%出现Ⅰ度松动,修复效果欠佳,两组修复效果比较差异有显著意义(P<0.05)。术后各阶段两组的PD、PLI、SBI均明显优于术前(P<0.05),但两组术后牙周指数比较差异无显著意义(P>0.05)。结论牙冠延长术有利于残根残冠的保存和修复,但要注意适应证的选择。  相似文献   
53.
Predictors of gastric emptying (GE) in patients with idiopathic Parkinson's disease (PD) of a solid and liquid meal are not well defined. For measurement of GE 80 patients with PD were randomly assigned to receive either a solid meal (250 kcal) containing 13C-octanoate (n = 40) or a liquid meal (315 kcal) with 13C-acetate (n = 40). All patient groups were off medication affecting motility and were matched for age, gender, body mass index, disease duration and severity, using Unified Parkinson's Disease Rating Scale (UPDRS). Gastric emptying was compared with a healthy control group (n = 40). Multiple regression analysis was used to determine predictors of gastric emptying. Exactly 88% and 38% of PD patients had delayed GE of solids and liquids respectively. Solid and liquid emptying was similar in women and men. There were no differences in GE in PD patients < 65 years of age when compared with patients > or = 65 years. Multiple regression analysis showed that motor handicaps such as rigour and action tremor are independent predictors of solid GE (r = 0.68, P < 0.001). The severity of motor impairment, but not any other neurological symptom, as assessed by UPDRS is associated with gastroparesis in PD and solid emptying is more likely to be delayed.  相似文献   
54.
The incidence of uterine cervical cancer has increased slightly in Western countries, with an increase in relatively young women. Overexpression of matrix metalloproteinases (MMPs)-2 and -9 has turned out as a prognostic factor in many cancers. We compared the expression of the proteins MMP-2 and MMP-9 in cervical primary tumors with clinical outcome and risk factors of cervical cancer. One hundred sixty-one patients with cervical cancer treated in Ume? University Hospital or Sahlgrenska University Hospital, Sweden, between 1991 and 1995 were included in the study. Paraffin-embedded tissue samples obtained prior to treatment were examined immunohistochemically by specific antibodies for MMP-2 and MMP-9. Forty-two percent of the tumors were intensively positive for MMP-2 and 31% for MMP-9. Nineteen percent of the samples were intensively positive for both proteinases and 47% negative or weak for both. Overexpression of MMP-2 seemed to predict unfavorable survival under Kaplan-Meier analysis and in the multivariate analysis. Early sexual activity and low parity seemed to correlate to overexpression of MMP-2. MMP-9 was not associated with survival or sexual behavior. Intensive MMP-9 was noted in grade 1 tumors. We conclude that MMP-2 and MMP-9 have different roles in uterine cervical cancer. MMP-2 could be associated with aggressive behavior, but MMP-9 expression diminishes in high-grade tumors.  相似文献   
55.
In a retrospective study using univariate analysis, we identified tumor type (nonendometrioid vs endometrioid), depth of myoinvasion (MI), mode of MI (infiltrative vs cohesive), and direct anatomic invasion of the cervical wall from the isthmus as significant positive risk factors for intramyometrial lymphvascular space involvement (LVSI). On multivariate analysis, tumor grade, depth of MI, and mode of MI retained their significance. We created a grid for the relative risks of LVSI with respect to these variables individually or in combination. We suggest that our indirect estimate of the risk of LVSI can help in assessing prognosis and determining the need for adjuvant therapy whenever LVSI is important in clinical decision making, but its pathologic diagnosis is uncertain.  相似文献   
56.
BACKGROUND: 1Alpha,25-dihydroxyvitamin D(3) [1,25(OH)(2) Vitamin D(3)] induces growth inhibition in squamous cell carcinoma (SCC) cell lines of the head and neck by arresting the cells in the G0/G1 phase of the cell cycle, probably due to an enhanced expression of p21, which could be demonstrated in other cell lines (JPPA, SCC9) before. In SCC25, a SCC cell line isolated from tongue, growth inhibition but no overexpression of p21 was detected. The retinoblastoma gene, as a direct target of G1 cyclin-CDK complexes, showed an obvious shift from the hyperphosphorylated to the hypophosphorylated form under 1,25(OH)(2)Vitamin D(3), which indicates that the growth inhibition takes place in the G0/G1 phase. To explore the possible pathway of growth inhibition in SCC25 we investigated other cell cycle inhibitors (p18, p19, p27). METHODS: Synchronized cells were treated with 1,25(OH)(2)Vitamin D(3) over 96 h. The cell cycle status and expression of cell cycle-regulating proteins was determined by fluorescence-activated cell sorting (FACS) and Western blotting. An overexpression of p18 in 1,25(OH)(2)Vitamin D(3) vs. ethanol-treated cells was determined until 30 h in SCC25. No influence was detectable on the expression of p27 and p19. CONCLUSION: One mechanism by which 1,25(OH)(2)Vitamin D(3) controls cell growth might be the upregulation of p21. As p21 was unsusceptible to 1,25(OH)(2)Vitamin D(3) in SCC25, other inhibiting proteins were necessary to be tested. The proven upregulation of p18 seems to be the responsible step for growth inhibition of 1,25(OH)(2)Vitamin D(3) in SCC25.  相似文献   
57.
本文提出了我国医疗器械产业中数字化技术发展中存在的主要问题,并分析了问题产生的原因。  相似文献   
58.
Purpose: To assess the accuracy of intraarterial measurement of transstenotic pressure gradients for the detection of hemodynamically suboptimal iliac angioplasty. Methods: In 14 patients, referred for diagnostic angiography, mean pressure gradients in the aorta and iliac artery were obtained twice, using a double-sensor pressure catheter. Additional iliac measurements were performed during pharmacologically induced flow augmentation. Repeatability was assessed by calculation of the mean difference plus standard deviation (MD ± SD) and repeatability coefficient (2 × SD). These results were extrapolated to 137 iliac angioplasty procedures with secondary stenting where there was a residual pressure gradient > 10 mmHg. Results: MD ± SD for repeated measurements at rest and during flow augmentation were 0 ± 2 mmHg and 1 ± 3 mmHg, respectively. Repeatability coefficients were 3 and 6 mmHg. Mean pressure gradients after hemodynamically insufficient angioplasty were 8 ± 7 mmHg at rest and 17 ± 5 mmHg following vasodilatation. Inaccurate pressure recordings may have led to inappropriate stent placement in less than 2.5%, and inappropriate denial of stent placement in less than 5% of the lesions. Conclusion: Variability of intraarterial pressure measurements has little consequence in the detection of hemodynamically significant stenosis after angioplasty. Received: 0/00/00/Accepted: 0/00/00  相似文献   
59.
The decoction of Sclerocarya birroea Hochst. shows hypoglycaemic effects, an increase in plasma IRI in normal rats and an incremented oral-glucose tolerance. The decoction is also active against diet-induced hypercholesterolaemia.  相似文献   
60.
Background: The management and follow-up of asthma patients presenting at Accident and Emergency (A&E) departments have mostly been studied in children's hospitals or specialised teaching hospitals. Aims: To study the adequacy of assessment, treatment and follow-up of patients presenting at A&E departments in non-teaching hospitals. Methods: A twenty-five per cent sample of presentations to A&E departments in all public hospitals in the Illawarra for one year was selected for a case note audit. Information on demographics, assessment, management and referral was extracted from the A&E case notes and medical records of cases with documentation of a final diagnosis of asthma. Chi square and Fischer's Exact tests were used for comparisons among hospitals. Results: Of 359 presentations with a final diagnosis of asthma, 88% were self referred and only 5% were first presentations. Objective measures of airways obstruction was not documented in 34% of admissions and 48% of nonadmissions. There was no documented follow-up in 28% of cases. The assessment and management of asthma in A&E was significantly poorer in smaller hospitals. Conclusion: Evidence of high use of A&E as a primary care facility by asthma patients was found in the study. There is a need to implement protocols to optimise assessment and treatment of asthma in smaller hospitals. (Aust NZ J Med 1993; 23: 672–677.).  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