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   4601篇
  免费   219篇
  国内免费   64篇
耳鼻咽喉   52篇
儿科学   383篇
妇产科学   69篇
基础医学   494篇
口腔科学   106篇
临床医学   393篇
内科学   796篇
皮肤病学   65篇
神经病学   220篇
特种医学   181篇
外科学   1072篇
综合类   78篇
一般理论   4篇
预防医学   179篇
眼科学   173篇
药学   272篇
中国医学   20篇
肿瘤学   327篇
  2023年   41篇
  2022年   92篇
  2021年   175篇
  2020年   78篇
  2019年   159篇
  2018年   165篇
  2017年   131篇
  2016年   140篇
  2015年   134篇
  2014年   211篇
  2013年   204篇
  2012年   353篇
  2011年   369篇
  2010年   220篇
  2009年   157篇
  2008年   269篇
  2007年   288篇
  2006年   282篇
  2005年   250篇
  2004年   247篇
  2003年   174篇
  2002年   167篇
  2001年   48篇
  2000年   53篇
  1999年   41篇
  1998年   22篇
  1997年   30篇
  1996年   25篇
  1995年   29篇
  1994年   21篇
  1993年   15篇
  1992年   31篇
  1991年   20篇
  1990年   17篇
  1989年   16篇
  1988年   15篇
  1987年   13篇
  1986年   18篇
  1985年   12篇
  1984年   16篇
  1983年   11篇
  1982年   8篇
  1980年   11篇
  1979年   14篇
  1978年   9篇
  1977年   7篇
  1976年   8篇
  1974年   14篇
  1973年   6篇
  1970年   6篇
排序方式: 共有4884条查询结果,搜索用时 15 毫秒
21.
22.
Homozygote hypotransferrinaemic mice (hpx/hpx) have cytopathological features similar to those of human congenital atransferrinaemia, genetic haemochromatosis, and neonatal haemochromatosis. These conditions all have in common high levels of cytotoxic non-transferrin-bound serum iron. This study describes the ultrastructural features of iron overload in liver, pancreas, heart, and small intestine of 2- and 12-month-old hypotransferrinaemic mice. Electron microscopic studies of unstained sections showed early parenchymal cell siderosis, with accumulation of numerous ferritin particles and clusters in the cytosol, as well as ferritin and haemosiderin in lysosomes (siderosomes). In the 12-month-old animals, iron was also found in Kupffer cells and macrophages in other tissues. In addition, there were conspicuous iron-containing compounds in the bile canaliculi, and marked iron deposition in the pancreas and heart. Laser microprobe mass analysis (LAMMA) enabled localization and relative quantitation of iron deposition in subcellular compartments providing in situ documentation of iron accumulation in siderosomes and contributed in assessing total cytosolic iron in various cell types. Moreover, it demonstrated the importance and magnitude of the biliary route for iron excretion in these animals.  相似文献   
23.
Unlike the penetrating monoenergetic 662 keV gamma rays emitted by 137Cs LDR sources, the spectrum of 192Ir used in HDR brachytherapy contains low-energy components. Since these are selectively absorbed by the high-atomic number materials of which intracavitary applicators are made, the traditional neglect of applicator attenuation can lead to appreciable dose errors. We investigated the attenuation effects of a uterine applicator, and of a set of commonly used vaginal cylinders. The uterine applicator consists of a stainless steel source guide tube with a wall thickness of 0.5 mm and a density of 8.02 g/cm3, whereas the vaginal cylinders consist of the same stainless steel tube plus concentric polysulfone cylinders with a radius of 1 or 2 cm and a density of 1.40 g/cm3. Monte Carlo simulations were performed to compute dose distributions for a bare 192Ir-HDR source, and for the same source located within the applicators. Relative measurements of applicator attenuation using ion-chambers (0.125 cm3) confirmed the Monte Carlo results within 0.5%. We found that the neglect of the applicator attenuation overestimates the dose along the transverse plane by up to 3.5%. At oblique angles, the longer photon path within applicators worsens the error. We defined attenuation-corrected radial dose and anisotropy functions, and applied them to a treatment having multiple dwell positions inside a vaginal cylinder.  相似文献   
24.
An implementation trial of leukocyte-reduced transfusions in cardiac surgery (primary coronary artery bypass graft and valve replacement) was performed from July to December 1998; comparisons were made with data from the same period in 1997. Patients from both periods were similar in important preoperative and intraoperative variables (age, sex, weight, number of units of RBCs transfused, ejection fraction). The mean total number of complications was statistically significantly decreasedfrom 0.26 complications per patient in the non-leukocyte-reduced to 0.19 in the leukocyte-reduced recipients. Overall, the mean +/- ISD costs of care per patient decreasedfrom 1997 ($27,615 +/- $33,973) to 1998 ($27,038 +/- $24,107). Mean costs decreased $1,700 per patient for recipients of leukocyte-reduced blood in 1998 compared with recipients of non-leukocyte-reduced blood in 1997 Mean costs increased $4,000 per patient in patients who did not receive transfusions in 1998 compared with 1997. Hospitalization costs decreased when leukocyte-reduced transfusions were implemented for patients undergoing cardiac surgery in our institution. Implementation of leukocyte reduction may be cost neutral or cost saving in at least some settings.  相似文献   
25.
26.
Prevention Science - There is evidence that universal school-based mindfulness training (SBMT) can have positive effects for young people. However, it is unknown who benefits most from such...  相似文献   
27.
Purpose

To define the clinical and pathological patterns of urinary bladder carcinoma from the University Hospital of Nepal.

Methods

This is a retrospective analytical study. Patients with bladder mass who underwent surgery over 1 year and who had data record were included in the study. Demographic profile, type of surgery, findings on clinical examination, cystoscopy findings, histopathological report, tumor stage, and post-surgery adjuvant therapy were analyzed.

Results

Out of 86 patients who underwent transurethral resection of bladder tumor, 77 patients had biopsy-proven malignant bladder tumor. Urothelial cancer was present in 96.1%. Male were 78.6%. The mean age of diagnosis was 65.5?±?11.8 years. Non-muscle-invasive bladder cancer (NMIBC) was 3.7 times more common than muscle-invasive bladder cancer (MIBC). High-grade tumors (58.6%) were more common than low grade (41.4%). The detrusor muscle was present inthe biopsy specimen of 48 patients (64%). Re-TURBT within 2–6 weeks was considered based on histopathology reports for about half of the patients (45.3%). Upstaging and upgrading of the tumor was present in 5.8 and 5.8% of the patients, respectively. Residual tumor without upstaging and upgrading was present in 23.5%. One patient (1.3%) had Clavien–Dindo grade 1, three (4%) patients had grade 2 and two patients (2.7%) had grade 3b.

Conclusion

In the present study, patients with bladder cancer are younger than reported in other studies. Smokers are strongly predisposed. The histological pattern is similar to the Western and Asian populations. NMIBC and MIBC occur in proportion to that described as in other studies. We had a lower rate of recurrence, upstaging and upgrading. We had a lesser rate of acceptance for radical cystectomy in our patients.

  相似文献   
28.
In the context of collateral circulation of the heart, the role of extra-cardiac collateral arteries has been thought to be negligible. We present a case in which such collateral vessel acted as a rescue, subsequent to a failed revascularisation attempt. With surgeons nowadays considering ‘less is more’ in terms of grafting in coronary artery bypass grafting (CABG), and more evidence arising in favour of medical therapy, we need to re-assess the role of these collateral vessels in the coronary circulation.  相似文献   
29.
Injury-related morbidity and mortality have been one of the most common causes of loss in productivity across all geographic distributions. It remains to be a global concern despite a continual improvement in regional and national safety policies. The establishment of trauma care systems and advancements in diagnostics and management have improved the overall survival of severely injured. A better understanding of the physiopathological and immunological responses to injury led to a significant shift in trauma care from “Early Total Care” to “Damage Control Orthopedics.” While most of these algorithms were tailored to the philosophy of “life before limb,” the impact of improper fracture management on disability and societal loss is increasingly being recognized. Recently, “Early Appropriate Care” of extremities has gained importance; however, its implementation is influenced by regional health care policies, available resources, and expertise and varies between low and high-income countries. A review of the literature was performed using PubMed, Embase, Web of Science, and Scopus databases on articles published from 1990 to 2020 using the Mesh terms “Polytrauma,” “Multiple Trauma,” and “Fractures.” This review aims to consolidate on guidelines and available evidence in the management of extremity injuries in a polytraumatized patient to achieve better clinical outcomes of these severely injured.  相似文献   
30.
BACKGROUND CONTEXTThe indication to perform a fusion and decompression surgery as opposed to decompression alone for lumbar degenerative spondylolisthesis (LDS) remains controversial. A variety of factors are considered when deciding on whether to fuse, including patient demographics, radiographic parameters, and symptom presentation. Likely surgeon preference has an important influence as well.PURPOSEThe aim of this study was to assess factors associated with the decision of a Canadian academic spine surgeon to perform a fusion for LDS.STUDY DESIGN/SETTINGThis study is a retrospective analysis of patients prospectively enrolled in a multicenter Canadian study that was designed to evaluate the assessment and surgical management of LDS.PATIENT SAMPLEInclusion criteria were patients with: radiographic evidence of LDS and neurogenic claudication or radicular pain, undergoing posterior decompression alone or posterior decompression and fusion, performed in one of seven, participating academic centers from 2015 to 2019.OUTCOME MEASURESPatient demographics, patient-rated outcome measures (Oswestry Disability Index [ODI], numberical rating scale back pain and leg pain, SF-12), and imaging parameters were recorded in the Canadian Spine Outcomes Research Network (CSORN) database. Surgeon factors were retrieved by survey of each participating surgeon and then linked to their specific patients within the database.METHODSUnivariate analysis was used to compare patient characteristics, imaging measures, and surgeon variables between those that had a fusion and those that had decompression alone. Multivariate backward logistic regression was used to identify the best combination of factors associated with the decision to perform a fusion.RESULTSThis study includes 241 consecutively enrolled patients receiving surgery from 11 surgeons at 7 sites. Patients that had a fusion were younger (65.3±8.3 vs. 68.6±9.7 years, p=.012), had worse ODI scores (45.9±14.7 vs. 40.2±13.5, p=.007), a smaller average disc height (6.1±2.7 vs. 8.0±7.3 mm, p=.005), were more likely to have grade II spondylolisthesis (31% vs. 14%, p=.008), facet distraction (34% vs. 60%, p=.034), and a nonlordotic disc angle (26% vs. 17%, p=.038). The rate of fusion varied by individual surgeon and practice location (p<.001, respectively). Surgeons that were fellowship trained in Canada more frequently fused than those who fellowship trained outside of Canada (76% vs. 57%, p=.027). Surgeons on salary fused more frequently than surgeons remunerated by fee-for-service (80% vs. 64%, p=.004). In the multivariate analysis the clinical factors associated with an increased odds of fusion were decreasing age, decreasing disc height, and increasing ODI score; the radiographic factors were grade II spondylolisthesis and neutral or kyphotic standing disc type; and the surgeon factors were fellowship location, renumeration type and practice region. The odds of having a fusion surgery was more than two times greater for patients with a grade II spondylolisthesis or neutral and/or kyphotic standing disc type (opposed to lordotic standing disc type). Patients whose surgeon completed their fellowship in Canada, or whose surgeon was salaried (opposed to fee-for-service), or whose surgeon practiced in western Canada had twice the odds of having fusion surgery.CONCLUSIONSThe decision to perform a fusion in addition to decompression for LDS is multifactorial. Although patient and radiographic parameters are important in the decision-making process, multiple surgeon factors are associated with the preference of a Canadian spine surgeon to perform a fusion for LDS. Future work is necessary to decrease treatment variability between surgeons and help facilitate the implementation of evidence-based decision making.  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