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   5427篇
  免费   360篇
  国内免费   39篇
耳鼻咽喉   47篇
儿科学   106篇
妇产科学   77篇
基础医学   609篇
口腔科学   66篇
临床医学   512篇
内科学   1445篇
皮肤病学   97篇
神经病学   723篇
特种医学   176篇
外科学   929篇
综合类   6篇
一般理论   1篇
预防医学   253篇
眼科学   60篇
药学   413篇
中国医学   8篇
肿瘤学   298篇
  2024年   5篇
  2023年   54篇
  2022年   138篇
  2021年   212篇
  2020年   105篇
  2019年   167篇
  2018年   199篇
  2017年   141篇
  2016年   166篇
  2015年   163篇
  2014年   234篇
  2013年   285篇
  2012年   415篇
  2011年   400篇
  2010年   236篇
  2009年   233篇
  2008年   356篇
  2007年   340篇
  2006年   330篇
  2005年   348篇
  2004年   326篇
  2003年   277篇
  2002年   230篇
  2001年   34篇
  2000年   32篇
  1999年   33篇
  1998年   59篇
  1997年   33篇
  1996年   38篇
  1995年   28篇
  1994年   39篇
  1993年   19篇
  1992年   8篇
  1991年   15篇
  1990年   9篇
  1989年   20篇
  1988年   15篇
  1987年   11篇
  1986年   11篇
  1985年   8篇
  1984年   9篇
  1983年   11篇
  1982年   6篇
  1980年   4篇
  1979年   4篇
  1976年   3篇
  1975年   2篇
  1974年   3篇
  1970年   2篇
  1968年   3篇
排序方式: 共有5826条查询结果,搜索用时 31 毫秒
61.
62.
Eight new oleanane saponins (1- 8) together with four know saponins (9-12) were isolated from the aerial parts of Meryta denhamii. Their structures were elucidated by 1D and 2D NMR experiments including 1D TOCSY, DQF-COSY, ROESY, HSQC, and HMBC spectroscopy, as well as ESIMS analysis. The antiproliferative activity of all compounds was evaluated using three murine and human cancer cell lines: J774.A1, HEK-293, and WEHI-164.  相似文献   
63.
Vitrification, an ultra-rapid cooling technique, offers a new perspective in attempts to develop an optimal cryopreservation procedure for human oocytes and embryos. To further evaluate this method for human oocytes, 796 mature oocytes (metaphase II) were collected from 120 volunteers. Since Italian legislation allows the fertilization of a maximum of only three oocytes per woman, there were 463 supernumerary oocytes; instead of being discarded, they were vitrified. When, in subsequent cycles, these oocytes were utilized, 328 out of 330 (99.4%) oocytes survived the warming procedure. The fertilization rate, pregnancy rate and implantation rate per embryo were 92.9, 32.5 and 13.2% respectively. Thus, as already reported in the literature, the vitrification procedure seems to be highly effective, safe (since healthy babies have been born) and easy to apply. In situations where embryo cryopreservation is not permitted (as in Italy), there is now good indication for routine application of the method, once further standardization is achieved.  相似文献   
64.

Background and aim

Breast cancer remains a leading cause of mortality among women. In metastasis, cascade migration of cancer cells and invasion of extracellular matrix (ECM) represent critical steps. Urokinase-type plasminogen activator (uPA), as well as metalloproteinases MMP-2 and MMP-9, strongly contribute to ECM remodelling, thus becoming associated with tumour migration and invasion. In addition, the high expression of cytoskeletal (CSK) proteins, as fascin, has been correlated with clinically aggressive metastatic tumours, and CSK proteins are thought to affect the migration of cancer cells. Consumption of fruits and vegetables, characterized by high procyanidin content, has been associated to a reduced mortality for breast cancer. Therefore, we investigated the biological effect of grape seed extract (GSE) on the highly metastatic MDA-MB231 breast cancer cell line, focusing on studying GSE ability in inhibiting two main metastatic processes, i.e., cell migration and invasion.

Methods

After MDA-MB231 breast cancer cells stimulated with GSE migration and invasion were evaluated by means of trans-well assays and uPA as well as MMPs activity was detected by gelatin zymography. Fascin, β-catenin and nuclear factor-κB (NF-κB) expression were determined using western blot technique. β-Catenin localization was observed by confocal microscopy.

Results

We observed that high concentrations of GSE inhibited cell proliferation and apoptosis. Conversely, low GSE concentration decreased cell migration and invasion, likely by hampering β-catenin expression and localization, fascin and NF-κB expression, as well as by decreasing the activity of uPA, MMP-2 and MMP-9.

Conclusions

These results make GSE a powerful candidate for developing preventive agents against cancer metastasis.  相似文献   
65.
Surgical treatment of pancreatic cancer is to date the only modality that offers a chance of long-term survival. Potentially curative surgery is an option for only about 15% of patients with pancreatic adenocarcinoma. The aim of this study was to determine the survival and to assess the association of clinical, pathological, and treatment features with survival of patients who underwent resection of pancreatic cancer at the Department of Surgery of Udine University Hospital. From November 1989 to December 2005, 137 consecutive patients, who underwent surgical procedures for pancreatic cancer, were followed in our department. We performed 76 pancreatico-duodenectomy, 26 distal pancreatectomies and 35 total pancreatectomies. The surgical reconstruction after pancreatico-duodenectomy was as follows: 11 closures of the main duct with manual nonabsorbable stitches, 24 closures of the main duct with a linear stapler, 17 occlusions of the main duct with neoprene glue and 24 duct-to-mucosa anastomoses. Mean survival time was 27.7 +/- 26.93 months (mean +/- SD) and mean disease-free survival time was 25.4 +/- 23.06 months (mean +/- SD). 1, 3, 5, 7 and 9-year survival rates were 63.9, 33.7, 21.17, 12.7 and 10.2%, respectively. Significant differences in survival were recorded by the Log-rank test for age > 70 (p = 0.001), surgical procedures (p = 0.00046) and presence of metastases (p = 0.0055) The treatment of pancreatic cancer is undertaken with two different aims. The first is radical surgery for patients with early-stage disease, mainly stage I and partly stage II. In all other cases, the aim of treatment is the palliation of the several distressing symptoms related to this cancer. The standard treatment option for resectable tumours is radical pancreatic resection according to the Whipple procedure or total pancreatectomy.  相似文献   
66.
Cotard's syndrome is a neuropsychiatric disease characterized by a variety of nihilistic delusions, commonly associated with several psychotic and major affective disorders, and neurological diseases, including stroke, dementia, and mental retardation. A 39-year-old male with mental retardation developed Cotard's syndrome, following an important episode of fear. During admission to our neurological unit, the patient underwent an accurate assessment, including neuroradiological, clinical, and neuropsychological examinations. At the psychiatric evaluation, he presented nihilistic delusions, in which he negated the existence of his body parts and the existence of his family members. The neuropsychological assessment ruled out other possible causes of misidentification, including the post-traumatic stress disorder. Thus, since also organic causes of Cotard's syndrome were excluded, the correlation between fear and the syndrome has been postulated and the patient opportunely treated, using a multidisciplinary approach. Our case suggests that in predisposed individuals negative emotions, including fear, may lead to delusional syndromes.  相似文献   
67.
Adjuvant chemotherapy and endocrine therapy can induce early iatrogenic menopause or worsen pre-existing menopausal symptoms in breast cancer survivors (BCS). The second most frequent menopausal symptom after hot flushes is the genitourinary syndrome (GSM). Since hormone replacement therapy is contraindicated in BCS, vaginal laser might represent a new nonhormonal option for GSM. This study aims at evaluating the effectiveness of the fractional CO₂ vaginal laser for GSM in BCS compared with healthy women. This is a retrospective study on 135 postmenopausal women (45 BCS and 90 healthy women) who underwent fractional CO2 laser for GSM. Objective (VHI and VVHI) and subjective outcomes (VAS for dyspareunia and vaginal dryness and a pain questionnaire) were evaluated at baseline visit and at every follow-up visit. Subjective and objective parameters improved significantly in both groups after laser therapy. The improvement was progressive and long-lasting up to 12 months after the end of the treatment. No severe adverse events were observed during the treatment. Fractional CO₂ vaginal laser induces a significant and long-lasting improvement on GSM symptoms in BCS. However, this improvement is slower than in healthy women undergoing the same treatment. Laser therapy turns out to be safe and well-tolerated.  相似文献   
68.
Respiratory complications are common in the patient with muscular dystrophy. The periodic clinical and instrumental respiratory evaluation is extremely important. Despite the presence in the literature of updated guidelines, patient associations often report lack of knowledge of these pathologies, particularly in peripheral hospitals. The purpose of this work, inspired by the Italian Muscular Dystrophy Association (UILDM) is to improve management of respiratory problems necessary for the management of these patients complex. To this end, the main items that the specialist can meet in the follow-up of these pathologies have been analyzed and discussed, among which the respiratory basal evaluation, the criteria of adaptation to non-invasive ventilation, management of bronchial secretions, situations of respiratory emergency, indications for tracheostomy and the subject of advance directives of treatment (DAT).Key words: respiratory failure, muscular dystrophy, cough efficacy, spirometry, polygraphy, non-invasive ventilation, arterial blood gases, cough machine, invasive ventilation, tracheostomy, mechanical ventilation  相似文献   
69.
BackgroundElevation of the joint line frequently occurs in revision total knee arthroplasty (RTKA) because of a wider flexion space than extension space. One solution to balance this flexion-extension space involves the introduction of couplers between the stem and femoral components, and the use of posteriorly offset femoral stems that we hypothesized would improve gap balancing and facilitate joint line restoration.MethodsWe retrospectively reviewed a selected series of 43 RTKA. Postoperative joint line height was subtracted from intended height using postoperative lateral radiographs. The value was negative if the joint line position was lowered, and positive if raised.ResultsForty knees were followed for a mean of 3.5 years. Mean postoperative joint line position change from intended position was 1.5 mm (range ? 2.5–7.5 mm). In 28 knees (70%), the joint line position was restored to within ± 2 mm of the intended position; in eight knees (20%), from 2–4 mm; and in four knees (10%), > 4 mm. Joint line position was raised in 32 knees (80%) and lowered in eight (20%). In the offset stem knees, the intended joint line position was 0.9 mm (range ? 1.2–3.4 mm) as compared with 3.2 mm (range ? 2.5–7.5 mm) for the straight stem knees.ConclusionsA coupler system between the femoral stem and femoral component restored the joint line in 70% of cases. The posterior offset stem provided increased posterior condylar offset, addressed the wider flexion space, provided better positioning of the stem, and restored the joint line.Level of evidenceTherapeutic Study Level IV  相似文献   
70.
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