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   4226篇
  免费   415篇
  国内免费   51篇
耳鼻咽喉   41篇
儿科学   88篇
妇产科学   104篇
基础医学   424篇
口腔科学   66篇
临床医学   471篇
内科学   929篇
皮肤病学   63篇
神经病学   372篇
特种医学   215篇
外科学   723篇
综合类   103篇
一般理论   2篇
预防医学   421篇
眼科学   61篇
药学   314篇
中国医学   10篇
肿瘤学   285篇
  2023年   27篇
  2022年   65篇
  2021年   106篇
  2020年   76篇
  2019年   90篇
  2018年   140篇
  2017年   116篇
  2016年   111篇
  2015年   156篇
  2014年   232篇
  2013年   285篇
  2012年   242篇
  2011年   240篇
  2010年   206篇
  2009年   197篇
  2008年   183篇
  2007年   159篇
  2006年   173篇
  2005年   175篇
  2004年   152篇
  2003年   157篇
  2002年   138篇
  2001年   86篇
  2000年   63篇
  1999年   77篇
  1998年   57篇
  1997年   63篇
  1996年   46篇
  1995年   48篇
  1994年   35篇
  1993年   27篇
  1992年   41篇
  1991年   37篇
  1990年   54篇
  1989年   37篇
  1988年   36篇
  1987年   29篇
  1986年   36篇
  1985年   32篇
  1984年   19篇
  1983年   27篇
  1982年   19篇
  1979年   24篇
  1978年   31篇
  1976年   19篇
  1975年   23篇
  1974年   21篇
  1973年   23篇
  1972年   22篇
  1971年   20篇
排序方式: 共有4692条查询结果,搜索用时 15 毫秒
41.
Entrapment of a central venous catheter (CVC) guide wire in an inferior vena cava (IVC) filter is a rare, but reported complication during CVC placement. With the increasing use of vena cava filters (VCFs), this number will most likely continue to grow. The consequences of this complication can be serious, as continued traction upon the guide wire may result in filter dislodgement and migration, filter fracture, or injury to the IVC. We describe a case in which a J-tipped guide wire introduced through a left subclavian access without fluoroscopic guidance during CVC placement was entrapped at the apex of an IVC filter. We describe a technique that we used successfully in removing the entrapped wire through the left subclavian access site. We also present simple useful recommendations to prevent this complication.  相似文献   
42.
OBJECTIVE: Calcium and vitamin D deficiency is common in older individuals, particularly those who live in nursing homes, and increases the risk of osteoporosis and fractures. METHODS: We conducted a randomized double-blind placebo-controlled study of combined supplementation with 500 mg of elemental calcium, as carbonate, and 400 IU of vitamin D bid for 12 months in women older than 65 years of age with vitamin D deficiency, defined as serum 25(OH)D concentrations 相似文献   
43.
44.

Background

Little is known about the long-term prognosis of small bowel carcinoids because currently no staging system exists.

Methods

A search of the Surveillance, Epidemiology and End Results (SEER) database identified 6,380 patients with small bowel carcinoid tumors from 1977 to 2004. Patients were analyzed according to various clinicopathologic factors and a tumor (T1, T2, T3), lymph node (N0, N1), and metastasis (M0, M1) staging system was created according to these parameters.

Results

Among the 6,380 patients, 2,985 women and 3,395 men, with a median age of 66 years (range 14-98), the median tumor size was 1.9 cm (range .1-30 cm). Multivariate analysis demonstrated that age, size of the primary tumor, and depth of invasion were significant factors. Four stages were created according to statistically significant prognostic factors: 13% of patients were classified into stage I, 31% into stage II, 16% into stage III, and 40% into stage IV. Five-year survival rates were 96%, 87%, 74%, and 43% for stages I through IV, respectively.

Conclusions

The newly developed TNM staging system accurately discriminates prognosis for small bowel carcinoid tumors.  相似文献   
45.
This work aimed to assess seminal alpha-1,4-glucosidase activity in infertile oligoasthenozoospermic men associated with and without scrotal varicocele. Eighty men were investigated. They were divided into three groups: group 1 (n = 20), fertile normozoospermic men; group 2 (n = 30), oligoasthenozoospermia with varicocele; and group 3 (n = 30), oligoasthenozoospermia without varicocele. The patients underwent medical history, clinical examination, conventional semen analysis and estimation of seminal plasma alpha-1,4-glucosidase activity by double-beam spectrophotometer method and serum testosterone by radioimmunoassay method. There was a significant decrease in the mean seminal alpha-1,4-glucosidase activity levels in infertile men versus controls (mean +/- SD; 7.66 +/- 0.433, 2.088 +/- 0.565, 5.384 +/- 0.85 mU ml(-1) respectively). Mean serum testosterone levels demonstrated nonsignificant differences between studied groups. Seminal alpha-1,4-glucosidase activity levels demonstrated significant correlation with sperm count, sperm motility percentage and serum testosterone in oligoasthenozoospermia with varicocele group and demonstrated nonsignificant correlation in other groups. It is concluded that varicocele-induced hypoxia is the adverse effect that causes both oligoasthenozoospermia and decreased seminal alpha-1,4-glucosidase levels.  相似文献   
46.
47.
Kidney allografts possess the ability to enable a short course of immunosuppression to induce tolerance of themselves and of cardiac allografts across a full‐MHC barrier in miniature swine. However, the renal element(s) responsible for kidney‐induced cardiac allograft tolerance (KICAT) are unknown. Here we investigated whether MHC disparities between parenchyma versus hematopoietic‐derived “passenger” cells of the heart and kidney allografts affected KICAT. Heart and kidney allografts were co‐transplanted into MHC‐mismatched recipients treated with high‐dose tacrolimus for 12 days. Group 1 animals (n = 3) received kidney and heart allografts fully MHC‐mismatched to each other and to the recipient. Group 2 animals (n = 3) received kidney and heart allografts MHC‐matched to each other but MHC‐mismatched to the recipient. Group 3 animals (n = 3) received chimeric kidney allografts whose parenchyma was MHC‐mismatched to the donor heart. Group 4 animals (n = 3) received chimeric kidney allografts whose passenger leukocytes were MHC‐mismatched to the donor heart. Five of six heart allografts in Groups 1 and 3 rejected <40 days. In contrast, heart allografts in Groups 2 and 4 survived >150 days without rejection (p < 0.05). These data demonstrate that KICAT requires MHC‐matching between kidney allograft parenchyma and heart allografts, suggesting that cells intrinsic to the kidney enable cardiac allograft tolerance.  相似文献   
48.
The purpose of this study was to determine which commonly reported outcome measures best correlated with patient satisfaction after revision hip arthroplasty and to identify factors unrelated to hip status that may also play a role. From our institutional database, we identified 78 patients (80 hips) who underwent revision total hip arthroplasty and collected follow-up data. Patients with moderate or severe pain and those with limited walking ability reported significantly lower satisfaction scores. Harris hip score and patient-rated general health status were independently associated with patient satisfaction. Patient-rated anxiety and depression correlated inversely with satisfaction. Commonly reported outcome measures do reflect patient satisfaction after revision hip arthroplasty. However, satisfaction also appears to be influenced by psychologic factors.  相似文献   
49.
Sciatic nerve palsy after revision hip arthroplasty is rare, but can have substantial impacts. The purpose of this study is to report the safety and reliability of limited sciatic nerve exposure during revision surgery. A retrospective case series of 350 revision hip surgeries performed by a single surgeon underwent sciatic nerve identification. In each case, the sciatic nerve was identified and tagged loosely with a Penrose drain. Three hundred forty-eight of 350 patients (99.4%) underwent successful revision hip arthroplasty. One patient developed a transient sensory palsy; and another patient, a delayed palsy. Both nerve palsies recovered by the 1-year visit. We advocate visual nerve identification and tagging in revision hip surgery as 1 possible method to potentially reduce the risks of sciatic nerve injury.  相似文献   
50.
BACKGROUND CONTEXT: Two common justifications for orienting cervical screws in an angled direction are to increase pullout strength and to allow use of longer screws. This concept is widely taught and has guided implant design. Fixed- versus variable-angle systems may offer strength advantages. Despite these teachings, there is a paucity of supporting biomechanical evidence. The purpose of our study is to test the influence of screw orientation and plate design on the maximum screw pullout force. PURPOSE: This study evaluates the effect of screw orientation and plate type (fixed- vs. variable-angle) on screw pullout strength. STUDY DESIGN: Anterior cervical plates of both a fixed- and variable-angle CSLP, were tested for peak pullout strength in a direct plate pullout model using polyurethane foam bone, which models osteoporotic bone. METHODS: Self-tapping, locking screws (4.0x14mm and 4.0x16mm) were used. Screws were oriented in the fixed-angle plate in the standard fashion. In the variable plate, screws were instrumented in three different orientations. Biomechanical testing was performed on an Instron DynaMight 8841 servohydraulic testing machine, measuring maximum pullout force under a displacement-controlled pullout rate of 1mm/min. Five samples were tested per group. RESULTS: When all screws were placed 90 degrees to the plate, there was a significantly increased peak pullout strength (412.8+/-22.2N) compared with when all screws were placed 12 degrees "up and in" (376.2+/-24.3N, p less than or equal to .03). When the 90 degrees construct was reproduced using 14-mm screws and compared with 16-mm screws oriented 12 degrees "all up and in," there was still significantly higher pullout strength with the all 90 degrees construct (434.2+/-28.7N vs. 376.2+/-24.3N, p less than or equal to .009). The fixed-angle plate had a significantly decreased peak pullout strength (288.2+/-15.7N) compared with the variable-angle plate (416.6+/-12.6N) (p less than .00001) when the screws were placed in the same orientation. Overall, the variable-angle plate, regardless of the orientation of screws, had a significantly greater pullout strength than the fixed-angle plate (p less than .001). CONCLUSIONS: In this system, a variable-angle plate has greater pullout strength than a fixed-angle plate, regardless of the orientation of screws. With the variable-angle plate, a construct of all screws 12 degrees "up and in" is the weakest configuration. We found that with the 90 degrees construct, both 16- and 14-mm screws performed significantly better than 16-mm convergent screws. These findings are remarkable because they contradict the current doctrine. This may be a function of plate-dependent factors and should not be applied universally to all plate systems. Further study of screw orientation in additional plating systems is warranted.  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