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   11071篇
  免费   688篇
  国内免费   18篇
耳鼻咽喉   63篇
儿科学   423篇
妇产科学   408篇
基础医学   1447篇
口腔科学   88篇
临床医学   1331篇
内科学   1975篇
皮肤病学   208篇
神经病学   1034篇
特种医学   241篇
外科学   1316篇
综合类   77篇
一般理论   6篇
预防医学   1310篇
眼科学   174篇
药学   841篇
  2篇
中国医学   5篇
肿瘤学   828篇
  2024年   33篇
  2023年   117篇
  2022年   178篇
  2021年   347篇
  2020年   188篇
  2019年   331篇
  2018年   381篇
  2017年   271篇
  2016年   303篇
  2015年   285篇
  2014年   418篇
  2013年   649篇
  2012年   1028篇
  2011年   964篇
  2010年   491篇
  2009年   447篇
  2008年   783篇
  2007年   794篇
  2006年   679篇
  2005年   659篇
  2004年   644篇
  2003年   524篇
  2002年   461篇
  2001年   77篇
  2000年   75篇
  1999年   76篇
  1998年   78篇
  1997年   67篇
  1996年   49篇
  1995年   29篇
  1994年   43篇
  1993年   30篇
  1992年   23篇
  1991年   23篇
  1990年   19篇
  1989年   16篇
  1988年   17篇
  1987年   21篇
  1986年   18篇
  1985年   15篇
  1984年   9篇
  1983年   17篇
  1982年   9篇
  1981年   8篇
  1979年   8篇
  1978年   10篇
  1977年   8篇
  1975年   8篇
  1972年   6篇
  1971年   6篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
92.
93.
The study aims to define how imaging findings, patient demographics, patient–provider interactions, and health care practices may affect a woman's decision to follow‐up in the setting of a BI‐RADS Category 3. A total of 398 women from the University of Arizona Breast Imaging Center with a BI‐RADS Category 3 assessment for mammography and/or ultrasound findings were evaluated between February 2012 and June 2014. Demographic information was analyzed for all patients, regardless of follow‐up. Women who returned for follow‐up within the recommended time period were given one survey at the time of their follow‐up appointment, and women who returned for follow‐up, but later than recommended, were given a separate survey to complete. Age, palpability of a lesion, and menopause status were related to follow‐up. Self‐rated general health was the only factor found to be associated with the decision to follow‐up on time. The majority of patients who followed up on time reported that mailed reminder cards were the primary practice that prompted follow‐up. Of patients who followed up later than recommended, the major reason was “no time.” The findings suggest that additional counseling regarding the benefits of short‐interval imaging follow‐up might be advantageous for patients.  相似文献   
94.

OBJECTIVE

To determine whether prostate‐specific antigen velocity (PSAV) is useful for prostate cancer detection in men from different age groups, and whether the same PSAV thresholds can reasonably be applied to all men aged ≥40 years.

PATIENTS AND METHODS

From a large prostate cancer screening study, 13 615 men had data on age and a calculable PSAV. We used statistical analysis to examine the ability of PSAV to predict prostate cancer risk in each age decade.

RESULTS

For men of all ages, the median PSAV was 0.6–0.7 ng/mL/year in men with prostate cancer, and 0–0.1 ng/mL/year in men with no prostate cancer (P < 0.005 for all). On receiver operating characteristic (ROC) analysis, the area under the curve was 0.800, 0.697, 0.693, and 0.668 for predicting prostate cancer risk using PSAV for men aged 40–49, 50–59, 60–69 and ≥70 years, respectively. In the multivariate model controlling for race, family history, and the total PSA level, both PSA and PSAV were significant independent predictors of prostate cancer risk in men of all ages.

CONCLUSIONS

The PSAV is significantly higher in men of all ages with prostate cancer compared with men with no prostate cancer; although on ROC analysis it performed the best in young men. Interestingly, the median PSAV in men with prostate cancer was <0.75 ng/mL/year regardless of age, suggesting that this threshold may be too high. Overall, this data confirms that PSAV is a useful tool for prostate cancer detection for men aged ≥40 years.  相似文献   
95.

Background

Surgery residents teach medical students; feedback is one critical teaching skill. We investigated whether feedback given by surgery residents to students could be improved through an online spaced education program.

Methods

Surgery residents were randomized to receive either a weekly spaced education e-mail during a 9-month period containing teaching bullets on how to provide effective feedback, or no intervention. Medical students rated the frequency and quality of feedback they received from the residents.

Results

Students reported 45% (67 of 149) of the spaced education residents gave frequent feedback, compared with 31% (55 of 175) of control residents (relative risk [RR], 1.43; P = .016). Students reported resident feedback was “helpful in their learning” in 92% (132 of 143) of their evaluations of spaced education residents, compared with 82% (132 of 161) of their evaluations of control residents (RR, 1.13; P = .01).

Conclusions

Educational programs using feedback bullets e-mailed weekly can significantly improve the frequency and quality of feedback that surgical residents provide medical students.  相似文献   
96.

Background

In breast cancer treatment, sentinel lymph node (SLN) evaluation is used to identify patients who may benefit from axillary lymph node dissection (ALND). Intraoperative evaluation (IE) of SLNs facilitates immediate ALND. Controversy exists regarding the accuracy of intraoperative SLN evaluation for patients with invasive lobular carcinoma (ILC) compared to invasive ductal carcinoma (IDC).

Methods

Using breast cancer registry data from January 2003 to March 2008, the intraoperative SLN evaluation of 66 ILC and 810 IDC patients was compared to the final SLN pathology result and to the performance of ALND.

Results

In ILC, the sensitivities of IE for isolated tumor cells (≤.2 mm, N0[i+], n = 9), micrometastases (>.2 mm and ≤ 2.0 mm, N1mi, n = 6), and macrometastases (>2.0 mm, N1a-3a, n = 21) were 0%, 17%, and 71%, respectively. The specificity was 100%. IE identified 16/27 (59%) of SLN-positive (N1mi, N1a-3a) axillae, resulting in synchronous ALND. Delayed ALND for false negative IEs (11/27, 41%) occurred in 7/11 patients (64%). In IDC, the sensitivities of IE for N0(i+) (n = 60), N1mi (n = 75), and N1a-3a (n = 129) metastases were 0%, 7%, and 71%, respectively. The specificity was 99.6%. IE identified 97/204 (48%) of SLN-positive (N1mi, N1a-3a) axillae, resulting in synchronous ALND. Delayed ALND for false negative IEs (107/204, 52%) occurred in 38/107 patients (36%).

Conclusions

Sensitivity and specificity of intraoperative SLN evaluation is very similar in ILC and IDC patients. Intraoperative SLN evaluation facilitated synchronous ALND in concordance with recommended practice guidelines.  相似文献   
97.

Objective

Extremity injuries account for the majority of wounds incurred during US armed conflicts. Information regarding the severity and short-term outcomes of patients with extremity wounds, however, is limited. The aim of the present study was to describe patients with battlefield extremity injuries in Operation Iraqi Freedom (OIF) and to compare characteristics of extremity injury patients with other combat wounded.

Patients and methods

Data were obtained from the United States Navy-Marine Corps Combat Trauma Registry (CTR) for patients who received treatment for combat wounds at Navy-Marine Corps facilities in Iraq between September 2004 and February 2005. Battlefield extremity injuries were classified according to type, location, and severity; patient demographic, injury-specific, and short-term outcome data were analysed. Upper and lower extremity injuries were also compared.

Results

A total of 935 combat wounded patients were identified; 665 (71%) sustained extremity injury. Overall, multiple wounding was common (an average of 3 wounds per patient), though more prevalent amongst patients with extremity injury than those with other injury (75% vs. 56%, P < .001). Amongst the 665 extremity injury patients, 261 (39%) sustained injury to the upper extremities, 223 (34%) to the lower extremities, and 181 (27%) to both the upper and lower extremities. Though the total number of patients with upper extremity injury was higher than lower extremity injury, the total number of extremity wounds (n = 1654) was evenly distributed amongst the upper and lower extremities (827 and 827 wounds, respectively). Further, lower extremity injuries were more likely than the upper extremity injuries to be coded as serious to fatal (AIS > 2, P < .001).

Conclusions

Extremity injuries continue to account for the majority of combat wounds. Compared with other conflicts, OIF has seen increased prevalence of patients with upper extremity injuries. Wounds to the lower extremities, however, are more serious. Further research on the risks and outcomes associated with extremity injury is necessary to enhance the planning and delivery of combat casualty medical care.  相似文献   
98.
Bone loss is a current limitation for long-term space exploration. Bone markers, calcitropic hormones, and calcium kinetics of crew members on space missions of 4-6 months were evaluated. Spaceflight-induced bone loss was associated with increased bone resorption and decreased calcium absorption. INTRODUCTION: Bone loss is a significant concern for the health of astronauts on long-duration missions. Defining the time course and mechanism of these changes will aid in developing means to counteract these losses during space flight and will have relevance for other clinical situations that impair weight-bearing activity. MATERIALS AND METHODS: We report here results from two studies conducted during the Shuttle-Mir Science Program. Study 1 was an evaluation of bone and calcium biochemical markers of 13 subjects before and after long-duration (4-6 months) space missions. In study 2, stable calcium isotopes were used to evaluate calcium metabolism in six subjects before, during, and after flight. Relationships between measures of bone turnover, biochemical markers, and calcium kinetics were examined. RESULTS: Pre- and postflight study results confirmed that, after landing, bone resorption was increased, as indicated by increases in urinary calcium (p < 0.05) and collagen cross-links (N-telopeptide, pyridinoline, and deoxypyridinoline were all increased >55% above preflight levels, p < 0.001). Parathyroid hormone and vitamin D metabolites were unchanged at landing. Biochemical markers of bone formation were unchanged at landing, but 2-3 weeks later, both bone-specific alkaline phosphatase and osteocalcin were significantly (p < 0.01) increased above preflight levels. In studies conducted during flight, bone resorption markers were also significantly higher than before flight. The calcium kinetic data also validated that bone resorption was increased during flight compared with preflight values (668 +/- 130 versus 427 +/- 153 mg/day; p < 0.001) and clearly documented that true intestinal calcium absorption was significantly lower during flight compared with preflight values (233 +/- 87 versus 460 +/- 47 mg/day; p < 0.01). Weightlessness had a detrimental effect on the balance in bone turnover such that the daily difference in calcium retention during flight compared with preflight values approached 300 mg/day (-234 +/- 102 versus 63 +/- 75 mg/day; p < 0.01). CONCLUSIONS: These bone marker and calcium kinetic studies indicated that the bone loss that occurs during space flight is a consequence of increased bone resorption and decreased intestinal calcium absorption.  相似文献   
99.
PURPOSE: Almost 75% of men with a prostate specific antigen (PSA) of 2.6 to 4.0 ng/ml have no evidence of prostate cancer on biopsy. Deciding whether and when to repeat the biopsy is challenging. We determined if patient specific variables might identify men at increased risk for the subsequent detection of prostate cancer. MATERIALS AND METHODS: We analyzed the records of 24,893 men from a community based prostate cancer screening study. Our study group consisted of 1,202 men with PSA 2.6 to 4.0 ng/ml and a previously negative prostate biopsy. Patient specific variables were analyzed for their value in predicting a future diagnosis of prostate cancer. RESULTS: Of 1,011 men with adequate followup 136 (13.5%) were subsequently diagnosed with prostate cancer. Mean followup +/- SD in men without prostate cancer was 72 +/- 36 months. Prostate cancer was subsequently diagnosed in 35% of men with high grade prostatic intraepithelial neoplasia (HGPIN) on initial biopsy (p <0.0001), in 18% with abnormal or suspicious digital rectal examination (DRE) (p = 0.02) and 16% with an annual PSA velocity of 0 ng/ml (p = 0.002). Multivariate analysis identified HGPIN, initial PSA 3.6 to 4.0 ng/ml, abnormal DRE, family history of prostate cancer and annual PSA velocity 0 ng/ml as predictors of prostate cancer. CONCLUSIONS: Men with a PSA of 2.6 to 4.0 ng/ml and negative biopsy should be advised to undergo repeat biopsy if they have HGPIN, initial PSA 3.6 to 4.0 ng/ml, abnormal DRE, a family history of prostate cancer or a PSA velocity of 0 ng/ml or greater.  相似文献   
100.
Living organ donors face direct costs when donating an organ, including transportation, lodging, meals, and lost wages. For those most in need, the National Living Donor Assistance Center (NLDAC) provides reimbursement to defray travel and subsistence costs associated with living donor evaluation, surgery, and follow‐up. While this program currently supports 9% of all US living donors, there is tremendous variability in its utilization across US transplant centers, which may limit patient access to living donor transplantation. Based on feedback from the transplant community, NLDAC convened a Best Practices Workshop on August 2, 2018, in Arlington, VA, to identify strategies to optimize transplant program utilization of this valuable resource. Attendees included team members from transplant centers that are high NLDAC users; the NLDAC program team; and Advisory Group members. After a robust review of NLDAC data and engagement in group discussions, the workgroup identified concrete best practices for administrative and transplant center leadership involvement; for individuals filing NLDAC applications at transplant centers; and to improve patient education about potential financial barriers to living organ donation. Multiple opportunities were identified for intervention to increase transplant programs’ NLDAC utilization and reduce financial burdens inhibiting expansion of living donor transplantation in the United States.  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