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   1073篇
  免费   73篇
耳鼻咽喉   7篇
儿科学   16篇
妇产科学   11篇
基础医学   115篇
口腔科学   8篇
临床医学   76篇
内科学   224篇
皮肤病学   30篇
神经病学   107篇
特种医学   22篇
外科学   71篇
综合类   22篇
预防医学   227篇
眼科学   5篇
药学   33篇
肿瘤学   172篇
  2023年   7篇
  2022年   27篇
  2021年   32篇
  2020年   24篇
  2019年   40篇
  2018年   41篇
  2017年   30篇
  2016年   29篇
  2015年   21篇
  2014年   24篇
  2013年   30篇
  2012年   56篇
  2011年   44篇
  2010年   13篇
  2009年   32篇
  2008年   46篇
  2007年   57篇
  2006年   60篇
  2005年   69篇
  2004年   51篇
  2003年   32篇
  2002年   37篇
  2001年   51篇
  2000年   31篇
  1999年   43篇
  1998年   14篇
  1997年   8篇
  1996年   15篇
  1995年   4篇
  1994年   9篇
  1992年   10篇
  1991年   14篇
  1990年   12篇
  1988年   8篇
  1987年   4篇
  1986年   11篇
  1985年   7篇
  1984年   8篇
  1983年   7篇
  1981年   8篇
  1980年   4篇
  1978年   5篇
  1977年   4篇
  1975年   6篇
  1974年   7篇
  1973年   11篇
  1972年   6篇
  1971年   7篇
  1970年   4篇
  1967年   4篇
排序方式: 共有1146条查询结果,搜索用时 33 毫秒
51.
Study Objective: To evaluate the efficacy of cisatracurium, rocuronium, and d-tubocurarine in preventing succinylcholine-induced fasciculations and postoperative myalgia in patients undergoing ambulatory surgery.

Design: Randomized, prospective, placebo-controlled trial

Setting: Teaching hospital.

Subjects: 80 ASA physical status I and II patients scheduled for elective ambulatory surgery with general anesthesia.

Intervention: A standardized balanced anesthetic technique was used for all patients.

Measurements and Main Results: Patients were randomized to receive cisatracurium 0.01 mg/kg, rocuronium 0.06 mg/kg, d-tubocurarine 0.05 mg/kg, or saline, 3 minutes prior to intravenous (IV) succinylcholine 1.5 mg/kg. The intensity of fasciculations and intubating conditions were assessed using a four-point rating scale. In addition, the severity of myalgia was assessed using a four-point rating scale in the postanesthesia care unit and at 24 hours postoperatively. No patient complained of any side effects after the administration of the study drug. Fasciculations were observed less frequently (p < 0.05) in the d-tubocurarine and rocuronium groups compared with the placebo and cisatracurium groups. However, there was no difference between the d-tubocurarine group and the rocuronium group (21% vs. 10%, respectively). Although fasciculations occurred less frequently in the cisatracurium group than in the placebo group (59% vs. 85%, respectively), this difference did not reach statistical significance. There was no difference among the four groups in the intubating conditions or the incidence of postoperative myalgia.

Conclusion: Pretreatment with rocuronium and d-tubocurarine was superior to cisatracurium in preventing succinylcholine-induced fasciculations. However, pretreatment did not have any effect on the incidence of myalgia after ambulatory surgery.  相似文献   

52.
Network analyses inform complex systems such as human brain connectivity, but this approach is seldom applied to gold-standard histopathology. Here, we use two complimentary computational approaches to model microscopic progression of the main subtypes of tauopathy versus TDP-43 proteinopathy in the human brain. Digital histopathology measures were obtained in up to 13 gray matter (GM) and adjacent white matter (WM) cortical brain regions sampled from 53 tauopathy and 66 TDP-43 proteinopathy autopsy patients. First, we constructed a weighted non-directed graph for each group, where nodes are defined as GM and WM regions sampled and edges in the graph are weighted using the group-level Pearson''s correlation coefficient for each pairwise node comparison. Additionally, we performed mediation analyses to test mediation effects of WM pathology between anterior frontotemporal and posterior parietal GM nodes. We find greater correlation (i.e., edges) between GM and WM node pairs in tauopathies compared with TDP-43 proteinopathies. Moreover, WM pathology strongly correlated with a graph metric of pathology spread (i.e., node-strength) in tauopathies (r = 0.60, p < 0.03) but not in TDP-43 proteinopathies (r = 0.03, p = 0.9). Finally, we found mediation effects for WM pathology on the association between anterior and posterior GM pathology in FTLD-Tau but not in FTLD-TDP. These data suggest distinct tau and TDP-43 proteinopathies may have divergent patterns of cellular propagation in GM and WM. More specifically, axonal spread may be more influential in FTLD-Tau progression. Network analyses of digital histopathological measurements can inform models of disease progression of cellular degeneration in the human brain.SIGNIFICANCE STATEMENT In this study, we uniquely perform two complimentary computational approaches to model and contrast microscopic disease progression between common frontotemporal lobar degeneration (FTLD) proteinopathy subtypes with similar clinical syndromes during life. Our models suggest white matter (WM) pathology influences cortical spread of disease in tauopathies that is less evident in TDP-43 proteinopathies. These data support the hypothesis that there are neuropathologic signatures of cellular degeneration within neurocognitive networks for specific protienopathies. These distinctive patterns of cellular pathology can guide future efforts to develop tissue-sensitive imaging and biological markers with diagnostic and prognostic utility for FTLD. Moreover, our novel computational approach can be used in future work to model various neurodegenerative disorders with mixed proteinopathy within the human brain connectome.  相似文献   
53.
Dual process theories of recognition memory posit that recollection and familiarity represent dissociable processes. Animal studies and human functional imaging experiments support an anatomic dissociation of these processes in the medial temporal lobes (MTL). By this hypothesis, recollection may be dependent on the hippocampus, while familiarity appears to rely on extrahippocampal MTL (ehMTL) structures, particularly perirhinal and lateral entorhinal cortices. Despite these findings, the dual process model and these anatomic mappings remain controversial, in part because the study of patients with lesions to the MTL has been limited and has revealed predominantly single dissociations. We examined measures of recollection and familiarity in three groups (normal older adults, amnesic‐mild cognitive impairment, Alzheimer's disease) in which these memory measures and the relative integrity of MTL structures are variable, thus enhancing our power to detect MTL‐memory relationships. Recollection and familiarity and volumes of hippocampus and ehMTL, defined as a region including entorhinal/perirhinal cortices and parahippocampus, were measured. Regression analyses revealed a stronger relationship of recollection with the hippocampus compared to ehMTL, while familiarity was more highly related to ehMTL compared to hippocampus. These results are consistent with a division of labor in the MTL and the dual process model. © 2010 Wiley‐Liss, Inc.  相似文献   
54.
We compared three implementations of single‐shot arterial spin labeled (ASL) perfusion magnetic resonance imaging: two‐dimensional (2D) pulsed ASL (PASL), 2D pseudocontinuous ASL (PCASL), and background‐suppressed (BS) 3D PCASL obtained in a cohort of patients with mild cognitive impairment (MCI) and elderly controls. Study subjects also underwent 18F‐fluorodeoxyglucose positron emission tomography (18F‐FDG PET). While BS 3D PCASL showed the lowest (P < 0.001) gray matter–white matter cerebral blood flow (CBF) contrast ratio, it provided the highest (P < 0.001) temporal signal‐to‐noise ratio. Mean relative CBF estimated using the PCASL methods in posterior cingulate cortex (PCC), precuneus, and hippocampus showed hypoperfusion in the MCI cohort compared to the controls consistent with hypometabolism measured by 18F‐FDG PET. BS 3D PCASL demonstrated the highest discrimination between controls and patients with effect size comparable to that seen with 18F‐FDG PET. 2D PASL did not demonstrate group differentiation with relative CBF in any ROI, whereas 2D PCASL demonstrated significant differences only in PCC and hippocampus. Mean global CBF values did not differ across methods and were highly correlated; however, the correlations were significantly higher (P < 0.001) when either the same labeling (PCASL) or the same acquisition strategy (2D) was used as compared to when both the labeling and readout methods differed. In addition, there were differences in regional distribution of CBF between the three modalities, which can be attributed to differences in sequence parameters. These results demonstrate the superiority of ASL with PCASL and BS 3D readout as a biomarker for regional brain function changes in MCI. Hum Brain Mapp 38:5260–5273, 2017. © 2017 Wiley Periodicals, Inc.  相似文献   
55.
Information on correlates of total physical activity (PA) levels among middle-aged and elderly women is limited. This article aims to investigate whether total daily PA levels are associated with age, body mass index, smoking, drinking status, and sociodemographic factors.  相似文献   
56.
OBJECTIVES: To compare outcome attributes of three available technologies for stem cell transplantation--bone marrow transplantation (BM), peripheral blood cell transplantation (PB), and cord blood transplantation (CB). To compare the cost per recipient for the three technologies, incorporating all donor and antigen matching functions, as well as the transplantation procedures. METHODS: Review of relevant literature using the CancerLit and HealthSTAR databases (plus earlier searches of MEDLINE and Embase) to summarize outcome differences. Estimations of cost per transplant using models drawing on Canadian experience. RESULTS: The literature review indicated that PB may have a modest advantage over BM in terms of outcomes. The literature indicated that CB has longer engraftment times (although this may be due to inadequate controls). Our modeling exercise indicated that costs for PB and BM are similar. CB has a higher cost per recipient, due in large part to the higher testing costs for every donated unit. CONCLUSIONS: Current literature is inadequate to provide an outcomes comparison of CB, PB, and BM. Viewed from a system-wide perspective, CB is a higher cost technique. However, PB and CB are emerging as technologies, and so our results should be viewed alongside the notion that there may be a steep learning curve in these technologies.  相似文献   
57.
A systematic review of telemedicine assessments based on searches of electronic databases between 1966 and December 2000 identified 66 scientifically credible studies that included comparison with a non-telemedicine alternative and that reported administrative changes, patient outcomes, or results of economic assessment. Thirty-seven of the studies (56%) suggested that telemedicine had advantages over the alternative approach, 24 (36%) also drew attention to some negative aspects or were unclear whether telemedicine had advantages and five (8%) found that the alternative approach had advantages over telemedicine. The most convincing evidence on the efficacy and effectiveness of telemedicine was given by some of the studies on teleradiology (especially neurosurgical applications), telemental health, transmission of echocardiographic images, teledermatology, home telecare and on some medical consultations. However, even in these applications, most of the available literature referred only to pilot projects and to short-term outcomes. Few papers considered the long-term or routine use of telemedicine. For several applications, including teleradiology, savings and sometimes clinical benefit were obtained through avoidance of travel and associated delays. Studies of home care and monitoring applications showed convincing evidence of benefit, while those on teledermatology indicated that there were cost disadvantages to health-care providers, although not to patients. Forty-four of the studies (67%) appeared to have potential to influence future decisions on the telemedicine application under consideration. However, a number of these had methodological limitations. Although useful clinical and economic outcomes data have been obtained for some telemedicine applications, good-quality studies are still scarce and the generalizability of most assessment findings is rather limited.  相似文献   
58.
The Department of Defense Familial Breast/Ovarian Cancer Research Project has offered genetic counseling and testing for BRCA1 and BRCA2 on a research basis to patients meeting specific diagnostic criteria, with risk for BRCA1 and BRCA2 mutations calculated based on the Couch model. In 2.5 years, 250 patients were evaluated and 101 patients met criteria requirements, including 33 who met criteria in more than one category. Ninety patients elected to undergo DNA testing. In this group of 90 patients, 14 mutations (15.5%) and 16 unclassified variants (17.7%) were identified. The most common inclusion criteria were onset of breast/ovarian cancer before age 45 years (n = 32) and onset of breast/ovarian cancer before age 45 years with strong family history (n = 21). However, when number of mutations and unclassified variants found were compared separately across all diagnostic criteria (including those of more than one capacity) using the chi 2 statistic, no significant differences were seen among the categories to suggest that one criterion was more predictive of mutations or variants than another. Couch risk values for patients with mutations showed a mean of 14% and ranged from 3.2 to 43.5% (range for all patients, 1.2-69.7%). These findings emphasize the importance of using multiple diagnostic criteria and suggest that a Couch risk value of > 3% may be useful in selecting patients for testing. The data also underscore the necessity of genetic counseling in the testing process, particularly given the large number of unclassified variants diagnosed and their uncertain status for disease predisposition.  相似文献   
59.
The omega-3 fatty acids, especially long-chain eicosapentaenoic acid (20:5n-3) and docosahexaenoic (22:6n-3) contained in "fatty" fish, have consistently been shown to retard the growth of breast cancer in vitro and in animal experiments. In contrast, studies of the association between fish consumption and breast cancer risk in human populations have not consistently shown inverse associations. However, previous studies have not considered the specific types of fish consumed. Using data from a large, nationwide case-control study conducted in Sweden, we examined the association between consumption of fatty and lean fish and breast cancer risk. Odds ratios (OR) and 95% confidence intervals were computed from unconditional logistic regression models. High consumption of fish was weakly associated with reduced breast cancer risk, and the association was not statistically significant. With multivariate adjustment, the OR for women with the highest consumption (> or =3.5 servings/wk) compared with women with the lowest (virtually none) was 0.88 (95% confidence interval = 0.60-1.29, P for trend = 0.15). When type of fish was examined separately, the association was similar for fatty and lean fish.  相似文献   
60.
Although laboratory data and a few adenoma prevention trials suggest that calcium supplementation may reduce the risk of colorectal neoplasia, the results of observational studies of calcium intake and colorectal cancer risk are contradictory. However, few studies have examined the association among women or effects in specific colon subsites. Women with colorectal cancer diagnosed through 31 December 2000 were identified by linkage to regional cancer registries. During an average 11.3 yr of follow-up of 61,463 women, we observed 572 incident cases of colorectal cancer. Using data obtained from a 67-item food frequency questionnaire and Cox proportional hazards models to estimate rate ratios and 95% confidence intervals, we found an inverse association between dietary calcium intake and colorectal cancer risk. Women with the highest calcium intake (median 914 mg/day) had a reduced risk of colorectal cancer (rate ratio = 0.72, 95% confidence interval = 0.056-0.93, P for trend = 0.02) compared with women with the lowest intake (median 486 mg/day). Furthermore, our results suggest that the inverse association may be strongest in relation to distal cancers and among older women. The association with dairy products was less clear, suggesting that calcium intake per se is more important than specific calcium sources. Vitamin D intake was not clearly associated with risk. In sum, our data suggest that high calcium intake may lower colorectal cancer risk.  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