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   28630篇
  免费   8545篇
  国内免费   173篇
耳鼻咽喉   257篇
儿科学   809篇
妇产科学   514篇
基础医学   5451篇
口腔科学   1053篇
临床医学   4063篇
内科学   6967篇
皮肤病学   570篇
神经病学   2183篇
特种医学   1911篇
外科学   6327篇
综合类   355篇
一般理论   12篇
预防医学   3094篇
眼科学   814篇
药学   1551篇
  4篇
中国医学   26篇
肿瘤学   1387篇
  2021年   483篇
  2020年   340篇
  2018年   435篇
  2017年   435篇
  2016年   621篇
  2015年   960篇
  2014年   1621篇
  2013年   2257篇
  2012年   934篇
  2011年   815篇
  2010年   1320篇
  2009年   1397篇
  2008年   731篇
  2007年   553篇
  2006年   659篇
  2005年   564篇
  2004年   515篇
  2003年   396篇
  2002年   417篇
  2001年   543篇
  2000年   448篇
  1999年   638篇
  1998年   822篇
  1997年   783篇
  1996年   821篇
  1995年   790篇
  1994年   668篇
  1993年   620篇
  1992年   628篇
  1991年   604篇
  1990年   548篇
  1989年   643篇
  1988年   648篇
  1987年   638篇
  1986年   597篇
  1985年   625篇
  1984年   557篇
  1983年   543篇
  1982年   599篇
  1981年   570篇
  1980年   541篇
  1979年   539篇
  1978年   511篇
  1977年   519篇
  1976年   449篇
  1975年   408篇
  1974年   366篇
  1973年   346篇
  1972年   348篇
  1971年   311篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
31.
Chronic pain has been shown to affect up to 60% of patients undergoing surgery for breast cancer. Besides younger age, other risk factors for the development of chronic pain have not been consistent in previous studies. The objective of the current investigation was to detect the prevalence and risk factors for the development of chronic pain after breast cancer surgery by examining a patient population from a tertiary cancer center in the United States. The study was a prospective observational cohort study. Subjects were evaluated at least 6 months after the surgical procedure. Subjects responded to the modified short form Brief pain inventory and the short form McGill pain questionnaire to identify and characterize pain. Demographic, surgery, cancer treatment, and perioperative characteristics were recorded. Propensity matching regression analysis were used to examine risk factors associated with the development of chronic pain. 300 patients were included in the study. 110 reported the presence of chronic pain. Subjects with chronic pain reported median (interquartile range [IQR]) rating of worst pain in the last 24 hours of 4 (2–5) and a median (IQR) rating on average pain in the last 24 hours of 3 (1–4) on a 0–10 numeric rating scale. Independent risk factors associated with the development of chronic pain were age, OR (95% CI) of 0.95 (0.93–0.98) and axillary lymph node dissection, 7.7 (4.3–13.9) but not radiation therapy, 1.05(0.56–1.95). After propensity matching for confounding covariates, radiation was still not associated with the development of chronic pain. Chronic pain after mastectomy continues to have a high prevalence in breast cancer patients. Younger age and axillary lymph node dissection but not radiation therapy are risk factors for the development of chronic pain. Preventive strategies to minimize the development of chronic pain are highly desirable.  相似文献   
32.
33.
We evaluated management of positive sub‐areolar/nipple duct margins in nipple‐sparing mastectomies (NSM) at our institution. Retrospective chart review of all NSM from January 2007 to April 2012 was performed and patient, tumor, and treatment information was collected. Sub‐areolar/nipple duct margins included ductal tissue from within the nipple. Of 438 NSM, 22 (5%) had positive sub‐areolar/nipple duct margins; 21 of 220 cancer‐bearing breasts (10%) and 1 of 218 prophylactic mastectomies (0.5%). Positive margins included four with invasive lobular carcinoma and 18 with ductal carcinoma in situ (DCIS). Management included removal of eight nipples and nine nipple areola complexes (NAC). Four of 17 nipple/NAC specimens had evidence of residual DCIS and none had residual invasive cancer. The majority of nipple/NAC specimens excised for a positive margin had no residual malignancy. Future studies are needed to determine the extent of NAC tissue removal required for positive margins.  相似文献   
34.
35.
Endophytic species of Colletotrichum associated with Mangifera indica (mango) are poorly understood. In this study, Colletotrichum species were isolated from mango in Pernambuco State, Brazil. There were significant differences in isolation frequencies of Colletotrichum species among sites and plant tissues. Mature leaf blades were colonized by most Colletotrichum isolates at the majority of sites. Partial sequences of glyceraldehyde-3-phosphate dehydrogenase (GAPDH) of 97 Colletotrichum isolates were amplified as an initial measure of genetic diversity. Phylogenetic analysis with a subset of 22 isolates were performed based on a multi-locus dataset (ACT, TUB2, CAL, CHS-1, GAPDH, ITS) followed by Apn2/MAT IGS sequence-analysis for isolates within the C. gloeosporioides species complex. Molecular analysis associated with phenotypic characteristics revealed six previously described species [C. asianum, C. cliviae, C. dianesei (syn. C. melanocaulon), C. fructicola, C. karstii and C. tropicale] and one new species. This new species is introduced as C. endomangiferae. All species isolated were pathogenic on mango fruits but varied in their virulence. There was no distribution pattern of species among sites and plant tissues, although C. asianum was the most prevalent species at all sites and in all plant tissues studied. Five previously reported Colletotrichum species causing anthracnose in mango fruits in northeastern Brazil were also recovered as endophytes.  相似文献   
36.
37.
We previously reported a zebrafish model of type I diabetes mellitus (DM) that can be used to study the hyperglycemic (HG) and metabolic memory (MM) states within the same fish. Clinically, MM is defined as the persistence of diabetic complications even after glycemic control is pharmacologically achieved. In our zebrafish model, MM occurs following β‐cell regeneration, which returns fish to euglycemia. During HG, fish acquire tissue deficits reflective of the complications seen in patients with DM and these deficits persist after fish return to euglycemia (MM). The unifying mechanism for the induction of diabetic complications involves a cascade of events that is initiated by the HG stimulation of poly‐ADP ribose polymerase enzyme (Parp) activity. Additionally, recent evidence shows that the HG induction of Parp activity stimulates changes in epigenetic mechanisms that correlate with the MM state and the persistence of complications. Here we report that wound‐induced angiogenesis is impaired in DM and remains impaired when fish return to a euglycemic state. Additionally, inhibition of Parp activity prevented the HG‐induced wound angiogenesis deficiency observed. This approach can identify molecular targets that will provide potential new avenues for therapeutic discovery as angiogenesis imbalances are associated with all HG‐damaged tissues.  相似文献   
38.

Background

Thromboembolic events represent a clinically significant cause of neurological morbidity during the endovascular management of cerebral aneurysms. We have implemented an anti-thromboembolic regimen consisting of pre- and postoperative dual antiplatelet therapy, as well as postoperative anticoagulation using heparin and dextran. The aims of our study were to examine the effect of this regimen on thromboembolic rates during elective aneurysm coiling, and to elucidate risk factors associated with the development of thromboembolic events in this setting.

Methods

We conducted a retrospective review of patients who underwent elective intracranial aneurysm coiling between January 2005 and February 2012. The primary outcome of interest was the occurrence of a clinically significant peri-procedural thromboembolic event. Secondary outcomes included the occurrence of a central nervous system (CNS) or systemic hemorrhage.

Results

During the study period, 312 patients underwent elective aneurysm coiling and six (2 %) thromboembolic events occurred; three (1 %) occurred in the group that received the anti-thromboembolic regimen (261 patients) and three (6 %) occurred in the group that did not receive the regimen (51 patients), resulting in a statistically significant difference (P?=?0.024). Both the presence of a hypercoagulable state (P?=?0.014) and the lack of the anti-thromboembolic regimen (P?=?0.043) were significantly associated with the occurrence of a thromboembolic event.

Conclusions

This study provides evidence that the regimen described here is safe and reduces thromboembolic complications during elective aneurysm coiling. Ours is likely the most aggressive regimen in the published literature and significantly reduced the rate of thromboembolism without any significant increase hemorrhagic complications.  相似文献   
39.
The in vitro activity of SK&F 104662, a new glycopeptide antibiotic, against gram-positive bacteria was evaluated. Activity was comparable to those of teicoplanin and vancomycin against most organisms. SK&F 104662 inhibited diphtheroids at concentrations of less than or equal to 0.5 microgram/ml. Addition of human serum to the test medium lowered the inhibitory activity of this glycopeptide against some organisms by as much as eightfold.  相似文献   
40.
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