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   31481篇
  免费   1498篇
  国内免费   279篇
耳鼻咽喉   361篇
儿科学   784篇
妇产科学   699篇
基础医学   3736篇
口腔科学   1794篇
临床医学   2442篇
内科学   6860篇
皮肤病学   609篇
神经病学   2112篇
特种医学   716篇
外科学   3763篇
综合类   1168篇
现状与发展   2篇
一般理论   34篇
预防医学   3696篇
眼科学   424篇
药学   2215篇
  2篇
中国医学   505篇
肿瘤学   1336篇
  2024年   31篇
  2023年   279篇
  2022年   360篇
  2021年   845篇
  2020年   531篇
  2019年   746篇
  2018年   1170篇
  2017年   750篇
  2016年   760篇
  2015年   971篇
  2014年   1111篇
  2013年   1435篇
  2012年   2539篇
  2011年   2764篇
  2010年   1495篇
  2009年   1143篇
  2008年   2146篇
  2007年   2214篇
  2006年   2005篇
  2005年   1866篇
  2004年   1610篇
  2003年   1435篇
  2002年   1317篇
  2001年   546篇
  2000年   601篇
  1999年   411篇
  1998年   129篇
  1997年   74篇
  1996年   68篇
  1995年   60篇
  1994年   54篇
  1993年   56篇
  1992年   235篇
  1991年   164篇
  1990年   146篇
  1989年   124篇
  1988年   112篇
  1987年   105篇
  1986年   90篇
  1985年   79篇
  1984年   67篇
  1983年   60篇
  1979年   31篇
  1975年   41篇
  1974年   52篇
  1973年   30篇
  1971年   36篇
  1970年   37篇
  1969年   32篇
  1968年   38篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
ObjectiveTo analyse the effects of training in elective colorectal laparoscopic surgery with a minimum 6 months follow up to assess early and delayed complications, and comparing the first 40 cases in the 1st Period (P-1: 1996–2002) with the 100 cases in the 2nd Period (P-2: 2003–2008). One of the surgeons had two training courses between P-1 and P-2.Material and methodsA total of 66 colorectal resections due to cancer were performed and 74 operations for benign disease. The cases of malignant diseases increased between P-1 and P-2 (P<0.001). (Odds-Ratio=0.16).ResultsThere number of complex cases increased between P-1 and P-2 (Anterior resection-amputation, left hemicolectomy, total colectomy, rectopexy) vs. Others (Sigmoidectomy, right resections) (P<0.05), but the mean duration of the operations was reduced by 29 minutes P<0.01). There were 24% conversions, with no change in P-2 (P=0.85). Surgical mortality at 3 months (1.4%) showed no differences (P=0.49). The total complications rate (31%) was significantly lower in P-2 (P=0.001), because medical complications (P=0.05), the more serious surgical complications (with reintervention) (P=0.05) and wound infections (P=0.0001) were lower. There was no change in the other surgical complications (P=0.61).The overall mean stay was 7.8 days (3-36) (median=6 days), with no differences between P-1 and P-2 (P=0.165). Conversion significantly lengthened the mean hospital stay (P=0.015) (from 7.2±5 days to 10.1±7 days), but there was no increase in complications (P=0.31).ConclusionTraining in colorectal laparoscopy and training periods with experts improve results (duration, complications, more complex surgery). Conversions did not decrease with experience and the hospital stays lengthened, but they were not associated with more complications.  相似文献   
992.
Abstract: Synchronous bilateral breast carcinoma (SBBC) and early onset are important characteristics of hereditary cases. The lifetime risk for breast carcinoma in Cowden syndrome (CS) is estimated to be 25–50%. We reported a 44‐year‐old woman presenting SBBC and characteristic mucocutaneous lesions of CS, confirmed by PTEN gene mutation analysis. Bilateral modified mastectomy and axillary dissection were performed. Histopathologic examination revealed a moderate‐differentiated invasive ductal carcinoma with mixed features of luminal A immunophenotype (Estrogen and/or Progesterone Receptors >50% and/or Ki67 < 30% of positive cells). The skin lesions showed the characteristic findings of tricholemmoma. Lack of PTEN expression was observed in all specimens. Sequencing analysis confirmed the presence of PTEN splice‐acceptor site mutation in intron 8 (c.1027‐2A>G), a germline mutation which had not been previously reported in CS. The patient received adjuvant chemotherapy and tamoxifen for 5 years. After 5 years of follow‐up, she persists recurrence‐free. SBBC with early onset suggests a hereditary predisposition. Thus, analysis of PTEN expression abnormality, easily assessed by immunohistochemistry, may be of clinical value to screen those patients with CS.  相似文献   
993.
ObjectivesTo assess the level of agreement on the GEMA 2009 clinical recommendations by a Spanish expert panel on asthma.Materials and methodsThe study was divided into four stages: 1) establishment of a 9 member scientific committee (GEMA authors) for selection of GEMA recommendations to use in the survey; 2) formation of a panel of 74 professionals with expertise in this field (pulmonologists, allergists, family doctors, ear, nose and throat and paediatric specialists); 3) Delphi survey in two rounds, sent by mail, with intermediate processing of opinions and a report to the panel members; and 4) analysis and discussion of results for the Scientific Committee.ResultsSeventy four participants completed the two rounds of survey. During the first round, a consensus was reached in 49 out of 56 questions analysed. Following discussion by the panel, the consensus was increased to a total of 53 items in the survey. With respect to the remaining questions, Insufficient consensus was obtained on the rest of the questions, due to differing views between sub-specialists, or lack of criteria by most of the experts.ConclusionsThe external analysis by asthma experts from different specialities showed a high level of professional agreement with the GEMA 2009 recommendations in Spain (96.5 %). The disagreement shown in three recommendations reflect the lack of a high level evidence. These issues represent areas of interest for future research.  相似文献   
994.
Joó JG  Beke A  Papp Z  Csaba A  Rab A  Papp C 《Prenatal diagnosis》2007,27(11):1028-1032
OBJECTIVE: The goal of the current publication is to review isolated central nervous system malformations (CSMs) using a database in excess of 75 000 cases, with special regard to the risk of recurrence of these malformations alone or in combination. METHODS: In the period between 1 January 1976 and 31 December 2005, among the 75 320 documented cases, consultations were requested due to earlier isolated CSMs in the patients' histories in 3030 cases (4.2%). Processing the data we only considered disorders of genetic origin, and that was why we excluded the cases due to intrauterine infection. Monogenically inherited malformations were also excluded from the analysis. The diagnosis of the malformations was based on the prenatal diagnosis of ultrasonography as well as the findings of the foetopathological examination. RESULTS: In 65% of the cases, the couples sought counselling because of malformation in a previous pregnancy. In these cases, the risk of recurrence was thought to be 5.2%, while in the case of two affected children this figure stood at 21.9%. Analysing the values for the risk of recurrence in 5-year periods, neural tube defects (NTDs) (particularly anencephaly and spina bifida) showed a detectable decrease, which could be attributed to a growing use of folic acid supplementation around the time of conception and during pregnancy. CONCLUSION: There is a clear decrease of risk of recurrence of NTDs, while in the case of the other CSMs in this study, there is no noteworthy chronological change in their risk of recurrence.  相似文献   
995.
OBJECTIVE: To evaluate the role a daily intake of 100 mg of ascorbic acid plays in urinary infection prophylaxis during pregnancy. METHODS AND MATERIALS: A single-blind clinical trial was carried out on pregnant women randomly assigned to the following treatment groups - Group A: oral treatment with ferrous sulphate (200 mg per day), folic acid (5 mg per day) and ascorbic acid (100 mg per day) for 3 months, and Group B: oral treatment with ferrous sulphate (200 mg per day) and folic acid (5 mg per day) for 3 months. All patients were clinically evaluated, and a urine culture was carried out each month for a period of 3 months. The chi(2) and odds ratio were used to compare effects with and without ascorbic acid, and statistical significance was considered at p<0.05. RESULTS: Global frequency of urinary infections was 25%. The presence of urinary infections in Group A (12.7%) was significantly lower than in Group B (29.1%), (p=0.03, OR =0.35, CI 95% =0.13-0.91). CONCLUSIONS: Daily intake of 100 mg of ascorbic acid played an important role in the reduction of urinary infections, improving the health level of the gestating women. We recommend additional vitamin C intake for pregnant women in populations which have a high incidence of bacteriuria and urinary infections.  相似文献   
996.
The use of percutaneously inserted central catheters (PICCs) is an established practice in most NICUs. With the widespread use of these catheters, an increasing number of PICC complications has been reported in neonates. We present one case of a PICC retained and tethered in the vein in a very low birth weight infant, as well as a systematic review of PICC retention cases. Ten previous cases of PICC retention in neonates were found. Among those cases, the most common associated factors were coagulase-negative staphylococcus catheter colonization/bactcremia and long duration of catheterization. Occlusion was not a usefiul sign for predicting catheter retention. Once retention was established, heparin or urokinase instillations were ineffective. Although surgical exploration was sometimes required, firm, continuous traction applied to the catheter over several hours or intermittent, moderately strong pulling maneuvers were successful in 44.4 percent of the cases in which they were performed. Traction did not show major side effects. Our case provides additional support for use of traction as the initial approach in the management of this rare complication.  相似文献   
997.
We determined the prevalence of hepatitis C virus (HCV) in hemodialysis patients by antibody testing and HCV RNA determination by PCR. A total of 149 patients with kidney failure with replacement therapy were tested. The prevalence of anti-HCV was 6.7% (10 of 149 patients), and viremia was detectable in 8 of 149 (5%) patients. Three of 149 patients (2%) were anti-HCV negative with detectable HCV RNA.  相似文献   
998.
The micronucleus (MN) assay can be used to detect the genotoxic effects of chemical agents in virtually any cell that divides frequently. Salamanders (Ambystoma sp.) are amphibians that can be easily maintained and bred in the laboratory and spontaneously shed their skin every 2.5-4 days. In this present study, we have evaluated the usefulness of this shed skin for the MN assay. We exposed salamanders to different concentrations of both the aneugen colchicine (COL) and the clastogen cyclophosphamide (CP) and we determined the frequency of micronucleated cells (MNCs) in their sheds. Fragments of shed skin were placed on clean slides, fixed, stained, observed with a light microscope, and the number of MNCs was counted. The MNC frequency was increased significantly by all doses of COL and CP tested, administered either as single or repeated exposures. The presence of MNCs in the shed skin and the speed of sloughing lead us to propose that the sheds of Ambystoma sp., or other amphibians that slough their skin, are suitable alternative models for detecting genotoxic exposures relevant to aquatic environments.  相似文献   
999.
Previous studies conducted in Leishmania led us to test the hypothesis that addition of human urine (HU) to the Liver Infusion Tryptose (LIT) medium would stimulate the in vitro growth of Trypanosoma cruzi and Trypanosoma rangeli strains. Herein, we show that the addition of 3% HU to LIT medium (LIT-HU3) significantly stimulated the growth of all the T. rangeli strains studied when compared with the parasite growth in conventional LIT medium (p < 0.05), and it was equivalent to the growth observed in LIT supplemented with fetal calf serum (FCS) in two parasite strains. Four out of the six T. cruzi strains analyzed showed a significant increase in parasite multiplication in LIT-HU3 (p < 0.05). However, two parasite strains presented good growth in both LIT and LIT-HU, suggesting differences in the parasite’s ability to grow in vitro. Furthermore, we have not observed differences in T. cruzi growth in LIT-HU3 and LIT supplemented with heat-denatured HU and in the metacyclogenesis of parasite strains cultured in LIT-HU3. These results allow concluding that the addition of HU to LIT medium stimulates the in vitro growth of T. rangeli and T. cruzi and can replace FCS as a supplement in culture medium.  相似文献   
1000.
Determining the optimal conditions for learning anatomy will help medical students to do better in a gross anatomy course. We examined the two types of anatomy courses offered in our institution: slow-paced (SP) and fast-paced (FP) courses, in which the same content is taught in approximately the same number of hours (SP = 91 hr; FP = 90 hr), but the duration of each course differed (SP = 91 1-hr sessions lasting 20 weeks; FP = 45 2-hr sessions lasting 9 weeks). The objective of this study was to find out whether a relationship exists between anatomy course pace and achievement. Two groups of students were tested on their anatomy knowledge both before beginning and after completing either the SP or the FP course. The average difference in scores obtained on the pre- and postcourse tests for each group was obtained and a t-test was used (P < 0.05) to compare the mean score for each group. A significant difference was found between group SP and group FP, with the highest achievement obtained by group SP. The pace of the course is thus a factor that influences achievement.  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