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   8233篇
  免费   436篇
  国内免费   43篇
耳鼻咽喉   70篇
儿科学   323篇
妇产科学   213篇
基础医学   1239篇
口腔科学   214篇
临床医学   811篇
内科学   1540篇
皮肤病学   93篇
神经病学   865篇
特种医学   436篇
外科学   1231篇
综合类   59篇
一般理论   2篇
预防医学   572篇
眼科学   114篇
药学   442篇
  1篇
中国医学   25篇
肿瘤学   462篇
  2022年   64篇
  2021年   130篇
  2020年   81篇
  2019年   131篇
  2018年   138篇
  2017年   97篇
  2016年   115篇
  2015年   126篇
  2014年   180篇
  2013年   264篇
  2012年   356篇
  2011年   362篇
  2010年   204篇
  2009年   186篇
  2008年   320篇
  2007年   323篇
  2006年   360篇
  2005年   358篇
  2004年   345篇
  2003年   340篇
  2002年   286篇
  2001年   259篇
  2000年   279篇
  1999年   244篇
  1998年   101篇
  1997年   95篇
  1996年   85篇
  1995年   56篇
  1994年   75篇
  1993年   83篇
  1992年   189篇
  1991年   178篇
  1990年   163篇
  1989年   168篇
  1988年   143篇
  1987年   159篇
  1986年   125篇
  1985年   153篇
  1984年   111篇
  1983年   89篇
  1982年   53篇
  1981年   59篇
  1979年   70篇
  1978年   87篇
  1975年   54篇
  1974年   64篇
  1973年   63篇
  1972年   71篇
  1971年   62篇
  1970年   57篇
排序方式: 共有8712条查询结果,搜索用时 31 毫秒
111.
OBJECTIVES: To test the hypothesis that patients with non-small cell lung cancer and single-level N2 metastases constitute a favorable subgroup of patients with mediastinal metastases, we analyzed the results of the Eastern Cooperative Oncology Group 3590 (a randomized prospective trial of adjuvant therapy in patients with resected stages II and IIIa non-small cell lung cancer) by site of primary tumor and pattern of lymph node metastases. METHODS: Accurate staging was ensured by mandating either systematic sampling or complete dissection of the ipsilateral mediastinal lymph nodes. The overall survival of patients with left lung non-small cell lung cancer and metastases in only 1 of lymph node levels 5, 6, or 7 and right lung non-small cell lung cancer with metastases in only 1 of levels 4 or 7 was compared with that of patients with N1 disease originating in the same lobe. RESULTS: The median survival of the 172 patients with single-level N2 disease was 35 months (95% confidence interval: 27-40 months) versus 65 months (95% confidence interval: 45-84 months) for the 150 patients with N1 disease (median follow-up 84 months, P =.01). However, among patients with left upper lobe tumors, survival was not significantly different between patients with N1 disease and patients with single-level N2 disease (49 vs 51 months, P =.63). The median survival of the 71 patients with single-level N2 metastases without concomitant N1 disease (skip metastases) was 59 months (95% confidence interval: 36-107 months) versus 26 months (95% confidence interval: 16-36 months) for the 145 patients with both N1 and N2 metastases (P =.001). CONCLUSIONS: Survival of patients with left upper lobe non-small cell lung cancer and metastases to single-level N2 lymph nodes is not significantly different from that of patients with N1 disease. The presence of isolate N2 skip metastases is associated with improved survival when compared with patients with both N1 and N2 disease. Survival should be reported by the lobe of primary tumor and metastatic pattern to guide future clinical trial development, treatment strategies, and revisions of the TNM staging system.  相似文献   
112.
Our objective was to compare maternal pelvimetry and patient acceptability between open low-field (0.5-T) and closed 1.5-T MR systems. Thirty women referred for pelvimetry (pregnant: n=15) were scanned twice in the supine position, once in the vertical open system and once in the closed system. Each patient completed a comfort and acceptability questionnaire. Pelvimetric and questionnaire data were compared between systems. Total scan time was double in the open system (7:52±1:47 vs 3:12±1:20 min). Poor image quality in the open system prevented assessment of interspinous and intertuberous diameters in one woman and all measurements in another, both pregnant, with abdominal circumferences >120 cm. The open system was much more acceptable in terms of claustrophobia and confinement (both p<0.01). Claustrophobia interrupted one closed examination. Thirty-three percent of pregnant women in both systems reported fear of fetal harm. Sixty percent of all women preferred the open system, 7% the closed system, and 33% had no preference. Limits of agreement of 3–5% from the mean for all diameters confirmed good pelvimetric reproducibility. Women's preference for open-system MR pelvimetry is feasible with abdominal circumferences ≤120 cm. Electronic Publication  相似文献   
113.
114.
9-[( 2-Hydroxy-1-(hydroxymethyl)ethoxy]-methyl)guanine (BW B759U) is a more potent inhibitor of human cytomegalovirus (HCMV) in vitro than is the related nucleoside analog acyclovir (ACV). BW B759U was selectively activated to the 5'-triphosphate (BW B759U-triphosphate) in cells infected with HCMV to levels at least 10-fold higher than those measured for ACV-triphosphate and up to as much as 100-fold higher than the levels found in uninfected cells. BW B759U-triphosphate accumulated in HCMV-infected cells with time; the rate of this increase was dependent upon the drug dose and virus multiplicity of infection. Enzyme activities that catalyzed the phosphorylation of thymidine and 2'-deoxycytidine increased 3- to 7-fold in extracts of cells early after HCMV infection but thereafter declined. No concomitant increase in the rate of BW B759U phosphorylation was detected under these assay conditions. Maximal rate of accumulation of both BW B759U-triphosphate and ACV-triphosphate after a short exposure to drug occurred in the late phase of the infective cycle, as the titer of extracellular virus reached a peak in untreated cultures, but after the decline of stimulated host deoxypyrimidine kinase activities. Once formed, the BW B759U-triphosphate pool decreased very slowly and thus it persisted for several days in both HCMV-infected and uninfected cells.  相似文献   
115.
The present paper examines reported frequencies of 21 health practices, beliefs that these health practices can prevent six different illnesses, and beliefs about those illnesses in a community sample of 396 people: 173 young (20 to 39 years), 111 middle-aged (40 to 59 years), and 112 elderly adults (60 to 89 years). Elderly respondents report higher frequencies of health-promoting actions (e.g., regular medical check-ups, avoidance of salt, regular sleep, and eating a balanced diet) than younger respondents. Health practices aimed at reinterpreting stress and controlling emotions (e.g., avoiding emotional stress, staying mentally alert and active) also increased with age. Belief that these 21 practices prevent specific illnesses was consistent across the three age groups. Beliefs about the six illnesses were consistent across age with three exceptions: Elderly people considered themselves more vulnerable to disease, saw it as more serious for them, and were less likely to use chronic mild symptoms, like weakness and aches, as illness warnings.  相似文献   
116.
Gastrointestinal transit times of cathartics combined with charcoal   总被引:2,自引:0,他引:2  
Oral activated charcoal usually is administered in toxic ingestions along with a cathartic. A study was done in volunteers to determine the rapidity of gastrointestinal transit when activated charcoal was administered with various cathartics. A control of activated charcoal was compared to the gastrointestinal transit times of activated charcoal plus the cathartics magnesium citrate, magnesium sulfate, or sorbitol. Activated charcoal alone produced a mean transit time of 23.5 hours; magnesium citrate catharsis occurred in 4.2 hours, magnesium sulfate catharsis occurred in 9.3 hours, and sorbitol catharsis occurred in 0.9 hours. Sorbitol clearly was the most rapidly acting cathartic.  相似文献   
117.
The severity of pulmonary emphysema can be affected by exposure to cigarette smoke in several ways. Inactivation of alpha-1-antitrypsin and recruitment of leukocytes to lung airways shifts the protease-antiprotease balance towards increased elastolytic activity. The present study demonstrates an additional effect of cigarette smoke inhalation and retardation of the repair process and of the neosynthesis of cross-linked elastin. Hamsters with elastase-induced emphysema, exposed to cigarette smoke for 1 wk immediately after elastase administration, showed a 40% reduction of 14C-lysine incorporation into the elastin-specific cross-links, desmosine, and isodesmosine. Concomitantly, there was a decrease in the level of lung lysyl oxidase to that observed in uninjured control animals, in sharp contrast to the sevenfold increase in lysyl oxidase activity in hamsters with elastase-induced emphysema recovering under atmospheric conditions. These findings suggest that impairment of the production of lysyl oxidase and the resynthesis of cross-linked elastin by smoke inhalation exacerbates alveolar destruction.  相似文献   
118.
Previous research has shown that the ventral medial prefrontal cortex (vmPFC) and hippocampus (Hipp) are critical for extinction memory. Basal forebrain (BF) cholinergic input to the vmPFC and Hipp is critical for neural function in these substrates, which suggests BF cholinergic neurons may be critical for extinction memory. In order to test this hypothesis, we applied cholinergic lesions to different regions of the BF and observed the effects these lesions had on extinction memory. Complete BF cholinergic lesions induced contextual fear memory generalization, and this generalized fear was resistant to extinction. Animals with complete BF cholinergic lesions could not acquire cued fear extinction. Restricted cholinergic lesions in the medial septum and vertical diagonal bands of Broca (MS/vDBB) mimicked the effects that BF cholinergic lesions had on contextual fear memory generalization and acquisition of fear extinction. Cholinergic lesions in the horizontal diagonal band of Broca and nucleus basalis (hDBB/NBM) induced a small deficit in extinction of generalized contextual fear memory with no accompanying deficits in cued fear extinction. The results of this study reveal that MS/vDBB cholinergic neurons are critical for inhibition and extinction of generalized contextual fear memory, and via this process, may be critical for acquisition of cued fear extinction. Further studies delineating neural circuits and mechanisms through which MS/vDBB cholinergic neurons facilitate these emotional memory processes are needed. © 2015 Wiley Periodicals, Inc.  相似文献   
119.
Study Type – Symptom prevalence (case control) Level of Evidence 3a What's known on the subject? and What does the study add? In recent years, a number of studies have reported a high prevalence of erectile dysfunction (ED) among patients with chronic prostatitis/chronic pelvic pain syndrome (CP/CPPS). Several studies have reported that the prevalence of ED ranges from 15.0 to 40.5% in men in China with CP/CPPS; however, the previous studies focusing on the prevalence of ED among patients with CP/CPPS all neglected to explore the magnitude of this association. Our study found an association between ED and previously diagnosed CP/CPPS. The odds of previous CP/CPPS were 3.62 times greater for cases than for controls, after adjusting for patient socio‐demographic characteristics, comorbidities, obesity, and alcohol abuse/alcohol dependence syndrome.

OBJECTIVE

  • ? To examine the association between erectile dysfunction (ED) and a previous diagnosis of chronic prostatitis/chronic pelvic pain syndrome (CP/CPPS) using a population‐based dataset.

PATIENTS AND METHODS

  • ? The data for this case–control study was obtained from the National Health Insurance database.
  • ? A total of 3194 males, who were ≥18 years of age when they first received a diagnosis of ED, were identified and 15 970 controls were randomly selected.
  • ? The prevalence and risk of CP/CPPS among cases and controls were calculated by using conditional logistic regression analysis.

RESULTS

  • ? In total, 667 (3.5%) of the 19 164 sampled subjects had been diagnosed with CP/CPPS before the index date; CP/CPPS was found in 276 (8.6%) cases and in 391 (2.5%) controls (P < 0.001).
  • ? Regression analysis indicated that cases were more likely to have had previous CP/CPPS (odd ratio 3.62, 95% confidence interval 3.07–4.26) after adjusting for patient monthly income, geographical location and urbanization level, as well as hypertension, diabetes, coronary heart disease, renal disease, obesity and alcohol abuse/alcohol dependence syndrome status, when compared with controls.

CONCLUSIONS

  • ? We conclude that there was an association between ED and having been previously diagnosed with CP/CPPS.
  • ? Urologists should be alert to the association between CP/CPPS and ED, and assess the erectile function of patients suffering from CP/CPPS.
  相似文献   
120.
Iwama T  Yoshimura K  Keller E  Imhof HG  Khan N  Leblebicioglu-Könu D  Tanaka M  Valavanis A  Yonekawa Y 《Neurosurgery》2003,53(6):1251-8; discussion 1258-60
OBJECTIVE: We sought to evaluate the efficacy of emergency craniotomy for patients with massive hematoma secondary to endovascular embolization of supratentorial arteriovenous malformations (AVMs) and to investigate relevant factors affecting outcome. METHODS: Within the past 15 years, 605 patients with intracranial AVMs have undergone 1066 endovascular embolizations at our institution. Of these, 24 patients experienced intracranial hemorrhage during or after the procedure. Fourteen patients were demonstrated to have massive intraparenchymal hematomas and deteriorated to a comatose state (Glasgow Come Scale score < or =6). Twelve patients underwent craniotomy within 170 minutes of being diagnosed with intraparenchymal hemorrhage. The surgical procedures performed were hematoma evacuation with total (6 patients) or partial (2 patients) resection of the AVM or hematoma evacuation only (4 patients). The clinical records of these 12 patients were analyzed retrospectively. RESULTS: Nine patients recovered to a favorable condition (good recovery, four patients; moderately disabled, five patients), one patient remained in a persistent vegetative state, and two patients died. The interval between hemorrhage and emergency craniotomy was significantly shorter in patients with favorable outcomes than in those with poor clinical outcomes. Advanced age and a larger volume of intraoperative blood loss were the factors relevant to poor outcome. Temporal lobe location of the AVM and incomplete embolization tended to correlate to poor clinical outcome, but this correlation was not statistically significant. The sizes of the AVM and the hematoma did not correlate to patient outcome. There was no difference in outcomes with regard to the surgical procedure performed. CONCLUSION: In patients with massive postembolization hematomas, emergency craniotomy should be performed as soon as possible to achieve a favorable outcome. Cooperation among interventional neuroradiologists, intensive care physicians, and neurosurgeons is essential to manage AVM patients with critical postembolization hemorrhage. There is no need to persist in performing simultaneous total resection of the AVM at the emergency craniotomy.  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