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   158906篇
  免费   10793篇
  国内免费   625篇
耳鼻咽喉   1769篇
儿科学   3906篇
妇产科学   2722篇
基础医学   20962篇
口腔科学   3389篇
临床医学   15560篇
内科学   33637篇
皮肤病学   3241篇
神经病学   14613篇
特种医学   6964篇
外国民族医学   14篇
外科学   25227篇
综合类   1959篇
一般理论   109篇
预防医学   11808篇
眼科学   3306篇
药学   10132篇
中国医学   238篇
肿瘤学   10768篇
  2023年   885篇
  2022年   1485篇
  2021年   3374篇
  2020年   2079篇
  2019年   3118篇
  2018年   3591篇
  2017年   2798篇
  2016年   3136篇
  2015年   3584篇
  2014年   5091篇
  2013年   6851篇
  2012年   10341篇
  2011年   11012篇
  2010年   6310篇
  2009年   6017篇
  2008年   9749篇
  2007年   10190篇
  2006年   10105篇
  2005年   10148篇
  2004年   9316篇
  2003年   8623篇
  2002年   8270篇
  2001年   2150篇
  2000年   1849篇
  1999年   2136篇
  1998年   1928篇
  1997年   1551篇
  1996年   1334篇
  1995年   1253篇
  1994年   1127篇
  1993年   1015篇
  1992年   1298篇
  1991年   1196篇
  1990年   1034篇
  1989年   979篇
  1988年   918篇
  1987年   894篇
  1986年   891篇
  1985年   867篇
  1984年   932篇
  1983年   805篇
  1982年   962篇
  1981年   861篇
  1980年   728篇
  1979年   657篇
  1978年   647篇
  1977年   534篇
  1976年   515篇
  1974年   513篇
  1973年   451篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
72.
73.
OBJECTIVE: The authors described the influence of specific medical conditions on clinical remission and response of major depression (MDD) in a clinical trial evaluating a care-management intervention among older primary-care patients. METHODS: Adults age 60 years and older were randomly selected and screened for depression. Participants were randomly assigned to Usual Care or to an Intervention with a depression care-manager offering algorithm-based care for MDD. In all, 324 adults meeting criteria for MDD were included in these analyses. Remission and response was defined by a score on the Hamilton Rating Scale for Depression <10 and by a decrease from baseline of > or =50%, respectively. Medical comorbidity was ascertained through self-report. Cognitive impairment was defined by a score <24 on the Mini-Mental State Exam (MMSE). RESULTS: In Usual Care, rates of remission were faster in persons who reported atrial fibrillation (AF) than in persons who did not report AF and slower in persons who reported chronic pulmonary disease than in persons who did not report chronic pulmonary disease; rates of response were less stable in persons with MMSE <24 than in those with MMSE > or =24. In the Intervention condition, none of the specific chronic medical conditions were significantly associated with outcomes for MDD. CONCLUSIONS: Because disease-specific findings were observed in persons who received Usual Care but not in persons who received more intensive treatment in the Intervention condition, our results suggest that the association of medical comorbidity and treatment outcomes for MDD may be determined by the intensity of treatment for depression.  相似文献   
74.
Acute myelogenous leukemia (AMU is a hematologic disorder that is characterized by an abnormal proliferation of immature myeloid cells. Granulocytic sarcomas are clusters of leukemic myeloid cells that may develop as a result of AML. Oral manifestations of AML are common and often involve enlargements of the gingiva and/or mucosal tissue from direct leukemia cell infiltration. We describe the case history of a 50-year-old man who had an ulcera-tive lesion of the oral mucosa that was determined to be a granulocytic sarcoma of AML-M0 subtype. The combination of both the subtype and clinical presentation of the leukemia makes this presentation unusual, and to the best of our knowledge, of a type that has not been previously reported in the literature.  相似文献   
75.
Phase II clinical trials are performed to investigate whether a novel treatment shows sufficient promise of efficacy to justify its evaluation in a subsequent definitive phase III trial, and they are often also used to select the dose to take forward. In this paper we discuss different design proposals for a phase II trial in which three active treatment doses and a placebo control are to be compared in terms of a single‐ordered categorical endpoint. The sample size requirements for one‐stage and two‐stage designs are derived, based on an approach similar to that of Dunnett. Detailed computations are prepared for an illustrative example concerning a study in stroke. Allowance for early stopping for futility is made. Simulations are used to verify that the specified type I error and power requirements are valid, despite certain approximations used in the derivation of sample size. The advantages and disadvantages of the different designs are discussed, and the scope for extending the approach to different forms of endpoint is considered. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   
76.
Against the theoretical background of the effort–recovery model and the action regulation theory, the author presents a cross‐sectional questionnaire study testing hypotheses about the relationship between work‐related time pressure, cognitive and emotional irritation, work–family conflict and psychosomatic complaints. Subjects were 576 female home care nurses. Results of a path analysis show that the relation of time pressure and psychosomatic complaints is partially mediated by experiencing a work–family conflict; also the relation of time pressure and work–family conflict is partially mediated by cognitive and emotional irritation. It is argued that cognitive and emotional irritation are fruitful concepts for a more comprehensive understanding of the relationship between work stressors and the development of strain‐based work–family conflict. Implications for the prevention of work–family conflict are outlined. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   
77.
78.
79.
BACKGROUND: Studies suggest that patients who undergo off-pump coronary artery bypass grafting (OPCABG) have fewer short-term complications and use fewer inpatient resources than do patients who undergo standard coronary artery bypass grafting (CABG) with extracorporeal circulation. However, dissimilarity between groups in risk factors for complications has hindered interpretation of results. OBJECTIVES: To compare the prevalence of selected complications (atrial fibrillation, stroke, reoperation, and bleeding) and inpatient resource utilization (length of stay, discharge disposition, total charges) between subjects undergoing primary isolated CABG or OPCABG who were matched with respect to key risk factors. METHODS: Retrospective, causal-comparative survey conducted in 1 center for 18 months. Patients who underwent primary isolated CABG or OPCABG were matched for sex, age (within 2 years), left ventricular ejection fraction (within 0.05), and graft-patient ratio (exact match) and compared for prevalence of new-onset atrial fibrillation, stroke, reoperation within 24 hours, and bleeding. Statistical analysis included Wilcoxon and t tests for paired comparisons. RESULTS: The sample (107 matched pairs) was 63% male, with a mean age of 66 (SD 9.5) years, a mean left ventricular ejection fraction of 0.51 (SD 0.13), and a mean graft-patient ratio of 3.41 (SD 0.74). The 2 groups did not differ significantly in New York Heart Association class (P = .43), Acute Physiology and Chronic Health Evaluation III score (P = .22), postoperative beta-blocker use (P = .73), or comorbid conditions. None of the complications examined differed significantly between pairs. CONCLUSION: Patients with comparable risk profiles have similar prevalences of selected complications after CABG and OPCABG.  相似文献   
80.
Teeth with white spot lesions (WSL) might be more prone to enamel loss during bracket debonding. This in vitro study compared enamel loss from teeth with (n = 14) and without (n = 14) WSL after polishing with low-speed finishing burs or disks (Sof-Lex, 3M ESPE, St Paul, Minn). Debonded surfaces were analyzed with a contact stylus profilometer, and digitized data were compared with baseline readings by using AnSur NT software (Regents, University of Minnesota, Minneapolis, Minn). Specimen surfaces were also examined with a scanning electron microscope. Two-way analysis of variance was performed to analyze the data. In teeth without WSL, the volume losses were 0.16 mm(3) for the bur group and 0.10 mm(3) for the disk group; the mean maximum depths were 47.7 microm for the bur group and 54.3 microm for the disk group. In teeth with WSL, the volume losses were 0.06 and 0.17 mm(3), and the mean maximum depths were 35.1 and 48.7 microm for the bur and disk groups, respectively. There were no significant differences in enamel loss between the 2 groups of teeth without WSL (P =.12). However, in teeth with WSL, the burs removed less enamel than the disks (P = 0.006). Scanning electron microscope examination showed that any damage on the enamel surface was usually located in the cervical third of the teeth. On most specimens, even though tooth surfaces appeared resin-free to the naked eye, there were remnants of it. The differences between groups were so small that they might be clinically insignificant.  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