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   20402篇
  免费   1290篇
  国内免费   30篇
耳鼻咽喉   200篇
儿科学   724篇
妇产科学   609篇
基础医学   2552篇
口腔科学   196篇
临床医学   3929篇
内科学   3408篇
皮肤病学   342篇
神经病学   1756篇
特种医学   320篇
外科学   1763篇
综合类   160篇
一般理论   35篇
预防医学   2721篇
眼科学   198篇
药学   1313篇
  2篇
中国医学   7篇
肿瘤学   1487篇
  2023年   119篇
  2022年   153篇
  2021年   433篇
  2020年   285篇
  2019年   437篇
  2018年   524篇
  2017年   439篇
  2016年   450篇
  2015年   501篇
  2014年   663篇
  2013年   995篇
  2012年   1512篇
  2011年   1505篇
  2010年   843篇
  2009年   763篇
  2008年   1389篇
  2007年   1513篇
  2006年   1479篇
  2005年   1379篇
  2004年   1352篇
  2003年   1242篇
  2002年   1154篇
  2001年   152篇
  2000年   92篇
  1999年   141篇
  1998年   237篇
  1997年   186篇
  1996年   183篇
  1995年   158篇
  1994年   162篇
  1993年   115篇
  1992年   80篇
  1991年   80篇
  1990年   76篇
  1989年   65篇
  1988年   80篇
  1987年   59篇
  1986年   68篇
  1985年   55篇
  1984年   60篇
  1983年   40篇
  1982年   69篇
  1981年   75篇
  1980年   62篇
  1979年   32篇
  1978年   35篇
  1977年   30篇
  1976年   20篇
  1974年   19篇
  1973年   20篇
排序方式: 共有10000条查询结果,搜索用时 62 毫秒
951.
Many rural communities are actively pursuing technology as a resource for solving education, health care, and economic development issues. These communities are establishing a technology and telecommunication infrastructure that makes them appealing to individuals and companies from urban communities. But this has created a challenge and an opportunity for the mental health industry in general, and more specifically, "substance abuse" professionals. The opportunity for the "substance abuse" profession is to design and use new services using the exact same technologies that may precipitate the need for the services.  相似文献   
952.
953.
When cardiac function and blood flow are first established are fundamental questions in mammalian embryogenesis. The earliest erythroblasts arise in yolk sac blood islands and subsequently enter the embryo proper to initiate circulation. Embryos staged 0 to 30 somites (S) were examined in utero with 40- to 50-MHz ultrasound biomicroscopy (UBM)-Doppler, to determine onset of embryonic heartbeat and blood flow and to characterize basic physiology of the very early mouse embryonic circulation. A heartbeat was first detected at 5 S, and blood vascular flow at 7 S. Heart rate, peak arterial velocity, and velocity-time integral showed progressive increases that indicated a dramatically increasing cardiac output from even the earliest stages. In situ hybridization revealed an onset of the heartbeat coincident with the appearance of yolk sac-derived erythroblasts in the embryo proper at 5 S. Early maturation of the circulation follows a tightly coordinated program.  相似文献   
954.
955.
OBJECTIVE: In previous studies, factors related to a history of suicide attempts in persons with alcohol dependence have included sociodemographic variables, a more severe course of alcoholism, additional substance use disorders, and psychiatric comorbidity. This 5-year prospective study evaluated attributes associated with suicide attempts in a group of treatment-seeking persons with alcohol dependence. Psychiatric comorbidity was examined in terms of a distinction between substance-induced and independent psychiatric disorders. METHOD: Semistructured interviews were conducted with 1,237 alcohol-dependent subjects from the Collaborative Study on the Genetics of Alcoholism both at an initial evaluation and at a 5-year follow-up. Clinically relevant information was gathered at baseline, and suicidal behavior, aspects of alcohol dependence, and drug use were evaluated at the follow-up interview. RESULTS: Alcohol-dependent subjects (N=56) with suicide attempts during the follow-up period were more likely than subjects with no suicide attempts (N=1,181) to have made prior attempts. Other factors related to future suicide attempts in univariate analyses included younger age, being separated or divorced, other drug dependence, substance-induced psychiatric disorders, and indicators of a more severe course of alcoholism. Gender did not predict future attempts. CONCLUSIONS: A 5-year prospective evaluation of attributes associated with suicide attempts among alcohol-dependent persons identified factors that contributed to a small but significant proportion of the variance for future suicidal behavior.  相似文献   
956.
OBJECTIVE: This longitudinal study had three aims: 1) determine the extent to which boys at high average risk and low average risk for substance use disorder differ on a construct of neurobehavioral disinhibition, 2) evaluate the capacity of neurobehavioral disinhibition to predict substance use frequency at age 16, and 3) demonstrate the utility of neurobehavioral disinhibition in predicting substance use disorder. METHOD: The authors derived an index of neurobehavioral disinhibition from measures of affect, behavior, and cognition. The neurobehavioral disinhibition score was used to discriminate youth at high and low average risk for substance use disorder and to predict substance use frequency after 4-6 years and substance use disorder after 7-9 years. RESULTS: The neurobehavioral disorder score significantly discriminated boys at high average risk from those at low average risk at ages 10-12. Neurobehavioral disinhibition at age 16, in conjunction with substance use frequency and risk status group, predicted substance use disorder at age 19 with 85% accuracy and accounted for 50% of the variance in Drug Use Screening Inventory overall problem density score. Neurobehavioral disinhibition was a stronger predictor of substance use disorder (odds ratio=6.83) than substance consumption frequency (odds ratio=3.19). CONCLUSIONS: Cross-sectional and longitudinal analyses indicated that neurobehavioral disinhibition is a component of the liability to early age at onset of substance use disorder.  相似文献   
957.
OBJECTIVE: Postmortem and in vivo brain imaging studies have identified abnormalities in the thalamus and the pons in both schizophrenia and alcoholism. The authors sought to determine whether patients with both schizophrenia and alcohol dependence would manifest exaggerated volume deficits in either structure. METHOD: Volumetric measures of the left and right thalamus and the pons were derived from magnetic resonance imaging scans obtained from 27 patients with schizophrenia, 19 patients with schizophrenia and comorbid alcohol dependence, 25 patients with alcohol dependence without comorbid axis I disorders, and 51 healthy comparison subjects. RESULTS: The alcohol-dependent patients had significant volume deficits in both the thalamus and the pons. Among patients with schizophrenia, there were no differences in thalamus volumes between those with and without comorbid alcohol dependence. However, patients with schizophrenia who were taking atypical antipsychotic medications had bilateral thalamic deficits, whereas those taking typical neuroleptics did not. Patients with schizophrenia and comorbid alcohol dependence had deficits in the pons. CONCLUSIONS: Patients with schizophrenia and comorbid alcohol dependence are at risk for alcohol-related reduction of pontine structures that are not necessarily affected by schizophrenia per se. The effect of alcohol dependence on the thalamus in schizophrenic patients may be mitigated by the type of neuroleptic medication they receive.  相似文献   
958.
BACKGROUND: High prevalence estimates in epidemiological surveys have led to concerns that the DSM system is overly inclusive and that mild cases should be excluded from future DSM editions. OBJECTIVE: To demonstrate that the DSM-III-R disorders in the baseline National Comorbidity Survey (NCS) can be placed on a severity gradient that has a dose-response relationship with outcomes assessed a decade later in the NCS follow-up survey (NCS-2) and that no inflection point exists at the mild severity level. METHODS: The NCS was a nationally representative household survey of DSM-III-R disorders in the 3-year time span 1990-1992. The NCS-2 is a follow-up survey of 4375 NCS respondents (76.6% conditional response rate) reinterviewed in 2000 through 2002. The NCS-2 outcomes include hospitalization for mental health or substance disorders, work disability due to these disorders, suicide attempts, and serious mental illness. RESULTS: Twelve-month NCS/DSM-III-R disorders were disaggregated into 3.2% severe, 3.2% serious, 8.7% moderate, and 16.0% mild case categories. All 4 case categories were associated with statistically significantly (P<.05, 2-sided tests) elevated risk of the NCS-2 outcomes compared with baseline noncases, with odds ratios of any outcome ranging monotonically from 2.4 (95% confidence interval, 1.6-3.4) to 15.1 (95% confidence interval, 10.0-22.9) for mild to severe cases. Odds ratios comparing mild to moderate cases were generally nonsignificant. CONCLUSIONS: There is a graded relationship between mental illness severity and later clinical outcomes. Retention of mild cases in the DSM is important to represent the fact that mental disorders (like physical disorders) vary in severity. Decisions about treating mild cases should be based on cost-effectiveness not current severity. Cost-effectiveness analysis should include recognition that treatment of mild cases might prevent a substantial proportion of future serious cases.  相似文献   
959.
BACKGROUND: Ataxic myelopathy due to copper deficiency has been described in ruminant animals and is called swayback. Neurological manifestations due to inherited copper deficiency secondary to the failure of intestinal copper absorption is well recognized as Menkes disease. The neurological consequences of acquired copper deficiency in humans are not well described. OBJECTIVE: To report 2 cases where patients developed a myelopathy with copper deficiency after gastrointestinal surgery.Patients Two patients developed a myelopathy many years after gastrointestinal surgery. Both had severe copper deficiency, which was the likely cause of the myelopathy. CONCLUSIONS: Acquired copper deficiency may present as a myelopathy. Gastrointestinal surgery and resulting decreased copper absorption may be causative.  相似文献   
960.
A case of an adolescent boy with multiple phobias who was treated successfully for his dental phobia is described to illustrate the clinical utility of the Dental Cognitions Questionnaire (DCQ) in aiding effective cognitive-behavior therapy. The client showed drops in dental anxiety that coincided with the use of the DCQ in cognitive restructuring, and there was a close correlation between dental cognitions and degree of dental anxiety over the time-course of therapy and follow up.  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