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   11815篇
  免费   726篇
  国内免费   46篇
耳鼻咽喉   171篇
儿科学   249篇
妇产科学   260篇
基础医学   1902篇
口腔科学   1106篇
临床医学   780篇
内科学   2272篇
皮肤病学   269篇
神经病学   923篇
特种医学   263篇
外科学   1344篇
综合类   43篇
一般理论   3篇
预防医学   1271篇
眼科学   259篇
药学   848篇
中国医学   104篇
肿瘤学   520篇
  2023年   92篇
  2022年   229篇
  2021年   354篇
  2020年   242篇
  2019年   329篇
  2018年   433篇
  2017年   297篇
  2016年   340篇
  2015年   388篇
  2014年   536篇
  2013年   613篇
  2012年   936篇
  2011年   980篇
  2010年   521篇
  2009年   385篇
  2008年   681篇
  2007年   690篇
  2006年   578篇
  2005年   580篇
  2004年   508篇
  2003年   481篇
  2002年   339篇
  2001年   249篇
  2000年   254篇
  1999年   232篇
  1998年   75篇
  1997年   55篇
  1996年   43篇
  1995年   47篇
  1994年   41篇
  1993年   37篇
  1992年   127篇
  1991年   102篇
  1990年   105篇
  1989年   67篇
  1988年   79篇
  1987年   63篇
  1986年   59篇
  1985年   61篇
  1984年   35篇
  1983年   22篇
  1982年   20篇
  1981年   17篇
  1979年   33篇
  1975年   18篇
  1974年   20篇
  1973年   22篇
  1972年   17篇
  1971年   14篇
  1969年   18篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
An estimated 350 million persons worldwide are chronically infected with hepatitis B virus (HBV). Immunosuppression after renal transplantation seems to enhance viral replication and increase the risk of developing cirrhosis and hepatocellular carcinoma. This retrospective study was performed to assess the prevalence among and serological status of HBV infection after renal transplantation at a single university Brazilian center. Thirty six (4.2%) patients among 850 kidney recipients showed positive HBsAg for more than 6 months; 31 were hepatitis B surface antigen (HBsAg) positive at transplantation. Of the 15 hepatitis B e antigen (HbeAg) positive patients, six had spontaneous HBeAg seroconversion and three also had HBsAg clearance. An additional two showed HBeAg clearance with Lamivudine without seroconversion. Among 15 HBeAg-negative patients, three developed HBeAg reversion with no elevation of alanine transferase (ALT) levels and one had HBsAg clearance. Only one patient had acute exacerbation of hepatitis B (ALT > 20 times normal range) but remained HbeAg negative. During follow-up, five patients became HBsAg positive; two reactivations of resolved hepatitis B, two with previous anti-HBS induced by vaccination, and one with no serological marker for HBV. Lamivudine was prescribed for 16 patients, two of whom had HbeAg clearance without seroconversion and five who developed viral resistance to Lamivudine after a mean of 29.2 months. No hepatocellular carcinoma or deaths related to hepatitis B were seen in this group. In summary, prevalence of HBV in kidney transplant patients was 4.2%. Immunosuppression after renal transplantation in HBV infection led to an increased risk of liver complications and changes in HBV serological status.  相似文献   
102.
Thymectomy by partial sternotomy for the treatment of myasthenia gravis   总被引:5,自引:0,他引:5  
BACKGROUND: Myasthenia gravis is an autoimmune disease characterized by weakness and fatigue of voluntary muscles. Surgical treatment of choice for myasthenia gravis has been thymectomy. However, thymectomy indications and surgical approach are still controversial. The purpose of this study is to evaluate the efficacy of partial median sternotomy approach to the thymus. METHODS: From 1973 to 1999, 478 patients with myasthenia gravis underwent thymectomy through a partial median sternotomy. RESULTS: Sixty-one patients (12.7%) had complete remission of symptoms, 299 (62.5%) had a significant improvement, and 83 (17.4%), a mild improvement; whereas 35 patients (7.4%) had no improvement of clinical symptoms. CONCLUSIONS: Partial median sternotomy has shown to be a useful surgical approach to the thymus, as demonstrated by the good functional and aesthetic results, associated with low morbidity and no mortality.  相似文献   
103.
BACKGROUND: The role of local excision for pT2 distal rectal cancer has been challenged because of the observation of high rates of lymph node metastases and local failure. However, neoadjuvant chemoradiation therapy (CRT) has led to increased local disease control and significant tumor downstaging, possibly decreasing rates of lymph node metastases. In this setting, a possible role for local excision of ypT2 has been suggested. METHODS: A total of 401 patients with distal rectal cancer underwent neoadjuvant CRT. Tumor response assessment was performed after at least 8 weeks from CRT completion. One hundred and twelve patients with complete clinical response were not immediately operated on and were excluded from the study, and 289 patients with incomplete clinical response were managed by radical surgery. Patients with final pathological stage ypT2 were analyzed to determine the risk of unfavorable pathological features that could represent unacceptable risk for local failure after local excision. RESULTS: Eighty-eight (30%) patients had ypT2 rectal cancer. Final ypT status was not associated with pretreatment radiological staging (p = 0.62). ypT status was significantly associated with the risk of lymph node metastases, risk of perineural and vascular invasion, and recurrence (p = 0.001). Lymph node metastases were present in 19% of patients with ypT2 rectal cancer. The risk of lymph node metastases in ypT2 was associated with the presence of perineural invasion (47% vs 4%; p = <0.001), vascular invasion (59% vs 6%; p < 0.001), and decreased mean interval CRT surgery (12 vs 18 weeks; p < 0.001), but not with mean tumor size (3.2 vs 3.1 cm; p = 0.8). Disease-free and overall survival rates were significantly better for patients with ypT2N0 (p = 0.02 and 0.006, respectively). Fifty-five (63%) patients with ypT2 had at least one unfavorable pathological feature for local excision (lymph node metastases, vascular or perineural invasion, mucinous type or tumor size >3 cm). CONCLUSION: Lymph node metastases were present in 19% of patients with ypT2 and were significantly associated with poor overall and disease-free survival rates. The risk of lymph node metastases could not be predicted by radiological staging or tumor size. Radical surgery should be considered the standard treatment option for ypT2 rectal cancer after CRT.  相似文献   
104.
OBJECTIVES: The transmission of vibrations from the tympanic membrane to the stapes footplate by an ossicular reconstruction prosthesis is affected by the size of the prosthesis head. We sought to determine if augmenting or reducing the head size of prosthesis had a systematic effect on transmission of vibrations to the stapes. STUDY DESIGN: We conducted a fresh cadaveric temporal bone middle ear study. METHODS: The incus was replaced with a prosthesis using a tympanic membrane to stapes head (TASH)-type hydroxyapatite prosthesis in nine fresh cadaveric temporal bones. Three prosthesis head sizes were created: unaltered, reduced, and augmented. Stapes vibrations were measured with a laser Doppler vibrometer in response to acoustic frequency chirps at 90 dB SPL. RESULTS: All three head size prostheses resulted in smaller stapes vibrations than the intact ear. There was no difference in the vibration transmission between the three different head sizes. All prostheses showed a vibration loss of 10 to 15 dB compared to the intact ear. CONCLUSIONS AND SIGNIFICANCE: Within the range of sizes tested, prosthesis head size had little impact on vibration transmission to the stapes footplate.  相似文献   
105.
This study was to evaluate specific effects of photodynamic therapy (energy density 15.8 J/cm2, 26.3 J/cm2 and 39.5 J/cm2) using methylene blue, toluidine blue and malachite green as photosensitizers and low-power laser irradiation on the viability of Candida albicans. Suspensions of C. albicans containing 106 cells/ml were standardized in a spectrophotometer. For each dye, 120 assays, divided into four groups according to the following experimental conditions, were carried out: laser irradiation in the presence of the photosensitizer; laser irradiation only; treatment with the photosensitizer only; no exposure to laser light or photosensitizer. Next, serial dilutions were prepared and seeded onto Sabouraud dextrose agar for the determination of the number of colony-forming units per milliliter (CFU/ml). The results were subjected to analysis of variance and the Tukey test (P < 0.05). Photodynamic therapy using the photosensitizers tested was effective in reducing the number of C. albicans.. The number of CFU/ml was reduced by between 0.54 log10 and 3.07 log10 and depended on the laser energy density used. Toluidine blue, methylene blue and malachite green were effective photosensitizers in antimicrobial photodynamic therapy against C. albicans, as was low-power laser irradiation alone.  相似文献   
106.
The aim of this study was to evaluate the acute effects of unilateral ankle plantar flexors static-stretching (SS) on the passive range of movement (ROM) of the stretched limb, surface electromyography (sEMG) and single-leg bounce drop jump (SBDJ) performance measures of the ipsilateral stretched and contralateral non-stretched lower limbs. Seventeen young men (24 ± 5 years) performed SBDJ before and after (stretched limb: immediately post-stretch, 10 and 20 minutes and non-stretched limb: immediately post-stretch) unilateral ankle plantar flexor SS (6 sets of 45s/15s, 70-90% point of discomfort). SBDJ performance measures included jump height, impulse, time to reach peak force, contact time as well as the sEMG integral (IEMG) and pre-activation (IEMGpre-activation) of the gastrocnemius lateralis. Ankle dorsiflexion passive ROM increased in the stretched limb after the SS (pre-test: 21 ± 4° and post-test: 26.5 ± 5°, p < 0.001). Post-stretching decreases were observed with peak force (p = 0.029), IEMG (P<0.001), and IEMGpre-activation (p = 0.015) in the stretched limb; as well as impulse (p = 0.03), and jump height (p = 0.032) in the non-stretched limb. In conclusion, SS effectively increased passive ankle ROM of the stretched limb, and transiently (less than 10 minutes) decreased muscle peak force and pre-activation. The decrease of jump height and impulse for the non-stretched limb suggests a SS-induced central nervous system inhibitory effect.

Key points

  • When considering whether or not to SS prior to athletic activities, one must consider the potential positive effects of increased ankle dorsiflexion motion with the potential deleterious effects of power and muscle activity during a simple jumping task or as part of the rehabilitation process.
  • Since decreased jump performance measures can persist for 10 minutes in the stretched leg, the timing of SS prior to performance must be taken into consideration.
  • Athletes, fitness enthusiasts and therapists should also keep in mind that SS one limb has generalized effects upon contralateral limbs as well.
Key words: Athletic training, exercise performance, exercise training, crossover, cross-education  相似文献   
107.
IntroductionLiver transplantation is the standard treatment for end-stage liver disease. Brazil holds the third highest number of liver transplants performed per year, but center maldistribution results in high discrepancies in accessing this treatment. In 2012, an interstate partnership successfully implemented a new liver transplantation program in the middle west of Brazil. Here, we report the results of the first 500 liver transplants performed in this new program and discuss the impacts of a new transplant center in regional transplantation dynamics.MethodsWe reviewed data from the first 500 consecutive deceased donor liver transplants performed in the new program during an 8-year period. We analyzed data on patients’ clinical and demographic profiles, postoperative outcomes, and graft and recipient survival rates. Univariate survival analysis was conducted using log-rank tests to compare the groups.ResultsAlmost half (48%) of the procured organs and 40% of the recipients transplanted in our center were from outside our state. Recipient 30-day mortality was 9%. Overall recipient survival at 1 year and 5 years was 85% and 80%, respectively. Mortality was significantly associated with higher Model for End-Stage Liver Disease (P < .001) but not with the presence of hepatocellular carcinoma (P = .795).DiscussionThe new transplantation program treated patients from different regions of Brazil and became the reference center in liver transplantation for the middle west region. Despite the recent implementation, our outcomes are comparable to experienced centers around the world. This model can inspire the creation of new transplantation programs aiming to democratize access to liver transplantation nationwide.  相似文献   
108.
Lung isolation techniques   总被引:6,自引:0,他引:6  
Left-sided double-lumen endotracheal tubes should be the tube of choice for most cases in which lung isolation is required. A right-sided double-lumen endotracheal tube can be used effectively when a contraindication to placing a left-sided double-lumen endotracheal tube exists. The method of choice to select left-sided double-lumen endotracheal tubes is based on chest radiograph or CT scan measurements of the trachea or bronchus. Based on clinical reports, Univents or WEB blockers may be a better choice for patients with difficult airways who require one-lung ventilation or for when a selective lobar blockade is needed. For all selective intubation, the method of choice for proper tube placement and bronchial blockade is fiberoptic bronchoscopy with the patient in a supine position at first or in a lateral decubitus position later, or if a malposition occurs.  相似文献   
109.
Epipericardial fat necrosis is an uncommon clinical condition of unknown etiology. It typically presents as acute pleuritic chest pain and should be differentiated from acute pulmonary embolism and acute coronary syndrome. This condition is diagnosed by characteristic chest computed tomography findings of an ovoid mediastinal fatty lesion with intrinsic and surrounding soft‐tissue stranding. Treatment of epipericardial fat necrosis includes the administration of anti‐inflammatory agents, and symptoms usually resolve within a few days after treatment initiation. This disease entity has rarely been reported since it was first described in 1957. Most current knowledge of epipericardial fat necrosis is based on case reports that describe this condition in previously healthy individuals. We present the case of a 39‐year‐old woman with a history of heart transplant, who presented with chest pain secondary to epipericardial fat necrosis. Serial computed tomography revealed lesion resolution after appropriate treatment.  相似文献   
110.
The aim of this study is to evaluate the validity and reliability of the Mandibular Function Impairment Questionnaire (MFIQ) (Portuguese version). Face and content validity of the Portuguese version were performed. To assess reproducibility of the data gathered with MFIQ, it was applied to 62 individuals who completed the questionnaire on two occasions. Validity and reliability of the data gathered with MFIQ were evaluated in a sample of 249 patients. Construct-related validity was assessed through factorial validity (by means of a confirmatory factor analysis), and convergent and discriminant validities were assessed, respectively, by the average variance extracted (AVE), composite reliability (CC) and bivariate correlations between factors. The internal consistency was estimated by the standardised Cronbach's alpha coefficient (α) and reproducibility by the intra-class correlation coefficient (ICC). All the items of MFIQ showed content validity. Reproducibility was excellent in both the 'functional capacity' dimension (D1) (ICC(D1) =0·895, 95% CI=0·832 to 0·935) and the 'feeding' dimension (D2) (ICC(D2) =0·825, 95% CI= 0·726 to 0·891). Items 1, 2, 6 and 7 of D1 had factor weights below the desired cut-off (0·5), and overall fit of the original bifactorial structure of the MFIQ was poor [(confirmatory fit index) CFI= 0·850, (goodness of fit index) GFI= 0·781, (root mean square error of approximation) RMSEA= 0·118]. Thus, these items were excluded, and the new, reduced version of the MFIQ showed good fit (CFI=0·933, GFI=0·879, RMSEA=0·099). The convergent validity was adequate (AVE≥0·5, CC≥0·7) for both factors. However, their discriminant validity was low (AVE(D1) = 0·51 and AVE(D2) = 0·66 <ρ(2) (D1D2) =0·70). The internal consistency was excellent (α(D1) =0·874; α(D2) =0·918). The Portuguese version of the reduced MFIQ produced data with good validity and reliability.  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