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   95735篇
  免费   29117篇
  国内免费   1076篇
耳鼻咽喉   2428篇
儿科学   2531篇
妇产科学   2289篇
基础医学   2163篇
口腔科学   5019篇
临床医学   25644篇
内科学   24199篇
皮肤病学   3265篇
神经病学   12110篇
特种医学   3537篇
外科学   17519篇
综合类   108篇
现状与发展   40篇
一般理论   1篇
预防医学   13164篇
眼科学   2197篇
药学   965篇
中国医学   8篇
肿瘤学   8741篇
  2024年   781篇
  2023年   5239篇
  2022年   1332篇
  2021年   2791篇
  2020年   5313篇
  2019年   1979篇
  2018年   6839篇
  2017年   7278篇
  2016年   7858篇
  2015年   7957篇
  2014年   10325篇
  2013年   11995篇
  2012年   3536篇
  2011年   3310篇
  2010年   6687篇
  2009年   8953篇
  2008年   3254篇
  2007年   2219篇
  2006年   3358篇
  2005年   1928篇
  2004年   1338篇
  2003年   1017篇
  2002年   937篇
  2001年   1784篇
  2000年   1107篇
  1999年   1653篇
  1998年   2042篇
  1997年   1875篇
  1996年   1927篇
  1995年   1668篇
  1994年   1068篇
  1993年   899篇
  1992年   731篇
  1991年   616篇
  1990年   494篇
  1989年   508篇
  1988年   492篇
  1987年   368篇
  1986年   344篇
  1985年   286篇
  1984年   244篇
  1983年   292篇
  1982年   220篇
  1981年   194篇
  1980年   118篇
  1978年   119篇
  1977年   116篇
  1976年   85篇
  1974年   70篇
  1972年   70篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.

Background

Sentinel node (SN) biopsy is associated with much less morbidity than axillary dissection. In patients with early breast cancer, lymphatic mapping and SN biopsy accurately stage the axillary nodes. Both currently available lymphatic mapping agents, radiocolloid and blue dye, have some limitations that may make perioperative or preoperative SN identification difficult. In such cases, exact knowledge of the topography of the axilla and the most probable location of the SN may be crucial.

Methods

In 12 fresh female cadavers with no history of breast carcinoma, injections of patent blue dye were used to visualize the SNs in the axillary quadrants and their lymphatic collectors from the upper outer quadrant of the breast, which is the most common location of breast cancer. The axilla was divided into quadrants with regard to the intersection of the thoracoepigastric vein and the third intercostobrachial nerve.

Results

All SNs were located within a circle of 2-cm radius of this intersection in the fatty tissue at the clavipectoral fascia. In most cases, the SN was located in the fatty tissue near the clavipectoral fascia in the lower ventral quadrant of the axilla (n = 14, 58%). In seven cases (29%), the SN was located in the upper ventral quadrant, in two cases (8%) in the upper dorsal quadrant, and in one case in the lower dorsal quadrant.

Conclusions

The results of this anatomical study may facilitate SN biopsy in patients with breast cancer.  相似文献   
993.
Reduced bone mineral density (BMD) was sporadically reported in patients with Marfan syndrome. This may or may not place the Marfan patient at increased risk for bone fracture. In comparing the BMDs of our patients with those reported in the literature, it seemed that agreement between values, and hence the degree of osteoporosis or osteopenia reported, was dependent on the instrumentation used. The objective of this study was to statistically assess this impression. Bone mineral density measurements from our previously published study of 30 adults with Marfan syndrome performed on a Lunar DPXL machine were compared with studies published between 1993–2000 measured using either Lunar or Hologic bone densitometry instruments. The differences of our measurements compared with those made on other Lunar machines were not statistically significant, but did differ significantly with published results from Hologic machines (P < 0.001). Before progress can be made in the assessment of BMD and fracture risk in Marfan patients and in the evidence-based orthopedic management of these patients, standardization of instrumental bone density determinations will be required along with considerations of height, obesity, age, and sex.  相似文献   
994.
995.
Background Neoadjuvant therapy is increasingly used in resectable locally advanced rectal cancer. The exact role of the addition of chemotherapy is not established. We compared neoadjuvant therapy using chemoradiation (CRT) or hyperfractionated accelerated radiotherapy (HART). Methods Clinical, pathological, and survival data were obtained from patients with resectable stage II or III rectal cancer within 7 cm from the anal verge. A group of 50 patients was treated with a preoperative dose of 41.6 Gy of radiotherapy (RT) in two daily fractions of 1.6 Gy over 13 days immediately followed by surgery (HART). A second group of 96 patients received 45 Gy of conventionally fractionated RT in 25 daily fractions of 1.8 Gy combined with 5-fluorouracil–based chemotherapy followed by surgery within 4 to 6 weeks (CRT). Both groups were compared in terms of morbidity, pathological downstaging, local recurrence, and survival. Results Both groups were comparable in terms of preoperative clinicopathological variables. The mean distance from the anal verge was 5.8 cm (HART) versus 4.9 cm (CRT). Sphincter preservation was possible in 74% (HART) versus 83.5% (CRT) of patients (P = .013). The clinical anastomotic leak rate was 2% (HART) versus 2.2% (CRT). Pathological complete response was observed in 4% (HART) versus 18% (CRT) of the resected specimens (P = .002). A pelvic recurrence developed in 6% (HART) versus 4.4% (CRT) of patients (P = .98). Overall 5-year survival was 58% (HART) versus 66% (CRT) (P = .19); disease-free 5-year survival was 51% (HART) versus 62% (CRT) (P = .037). Conclusions Compared with preoperative HART followed by immediate surgery, preoperative CRT followed by a 6-week waiting period enhances pathological response and increases sphincter preservation rate. This could be explained by the addition of chemotherapy or the longer interval between neoadjuvant therapy and surgery. No statistically significant difference was observed in local control or overall survival.  相似文献   
996.
997.
998.
Amniotic membrane (AM), the most internal placental membrane, has unique properties including antiadhesive effects, bacteriostatic, wound protection and pain-reduction properties, as well as epithelialization initialization capacities. Furthermore, AM is widely available and less costly than other bioengineered skin substitutes. In a prospective pilot study, we evaluated the safety, feasibility, and the effects on healing of AM graft in 15 patients with chronic venous leg ulcers. AM grafts were prepared from placentas harvested during cesarean section. All grafted AM had adhered to the wound bed 7 days after being applied with a 100% engraftment rate. The percentage of granulation tissue increased significantly (from 17% on day 0 to 69% on day 14, p<0.0001), along with a significant decrease of fibrinous slough (from 36% at day 0 to 16% at day 14, p<0.001). A significant clinical response occurred in 12 patients (80%) including complete healing (20%) in three during the 3-month follow-up period. The ulcer surface area decreased significantly from a mean value (+/- standard deviation) of 4.59 +/- 2.49 cm(2) at baseline to 2.91+/-2.01 cm(2) on day 30 (p<0.001). All patients experienced a significant reduction of ulcer-related pain rapidly after AM transplantation. No adverse events were recorded. AM transplantation seems to function as a safe substrate, promoting proper epithelialization while suppressing excessive fibrosis. Further advantages of biotherapy with AM are its easy and low-cost production, and that it can be applied as an ambulatory treatment without immobilization. AM transplantation may thus be considered to be an alternative method for treating chronic leg ulcers.  相似文献   
999.
Chronic wounds are characterized by failure in wound-healing response and a delay in healing or nonclosure of the wounds. This results in a high effort in clinical treatment and/or home care. A major difference between acute wounds and chronic wounds is the imbalance of proteinase inhibitors and proteinase activity that regulates the degradation and regeneration of the extracellular matrix proteins. Collagen and collagen/oxidized regenerated cellulose dressings act as a competitive substrate for matrix metalloproteinase-2, matrix metalloproteinase-9, and bacterial collagenase and influence this imbalance positively. Both wound dressings, approved for chronic wound treatment, the bovine collagen type I sponge and the oxidized regenerated cellulose collagen sponge, did not differ significantly in their sorption profiles for all enzymes. In general, binding was enhanced with a longer incubation time. The density of the device and the accessible surface, which can be controlled by the manufacturing process, are the crucial factors for the efficiency of the wound dressing.  相似文献   
1000.
Clinical Implication of CXCL12 Expression in Gastric Cancer   总被引:1,自引:0,他引:1  
PURPOSE: Recent research has revealed that tumor cells expressing chemokine receptors have a crucial impact on patient survival. However, there is no information regarding chemokine expression in gastro-intestinal cancer. This study immunohistochemically investigated CXCL12 expression in gastric cancer and evaluated its association with clinical factors, including patient prognosis. METHOD: A total of 185 gastric cancer patients receiving curative gastrectomy were assessed. CXCL12 expression was evaluated by immunohistochemical analysis. Tumors with CXCL12-positive cancer cells were regarded as CXCL12 positive, and according to the degree of CXCL12 expression, patients were divided into three groups (weak, 31 cases; moderate, 27 cases; strong, 20 cases). Correlations between CXCL12 expression and clinical factors in gastric cancer were then determined. RESULTS: CXCL12 was found in the cellular membrane of cancer cells. Seventy-four of 185 patients were classified into the CXCL12-positive group. Patients were divided into three groups according to the positivity of CXCL12 expression. Significant associations between CXCL12 and lymph node metastases (p < 0.05), depth of invasion (p < 0.01), lymphatic invasion (p < 0.01), tumor diameter (p < 0.05), and clinical stage (p < 0.01) were seen. Univariate analysis revealed that the CXCL12-positive group had significantly poorer surgical outcome than the CXCL12-negative group (p < 0.01). Multivariate analysis revealed CXCL12 to be an independent prognostic factor in gastric cancer (p = 0.02). CONCLUSION: Cancerous CXCL12 positivity was determined to be an independent prognostic factor in gastric cancer, with CXCL12-positive gastric cancer showing more-aggressive behavior. Autocrine CXCL12 secretion from tumor cells may activate CXCR-4 on the tumor cells, which may be related to of the viability of distant metastases.  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