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   6390篇
  免费   525篇
  国内免费   10篇
耳鼻咽喉   92篇
儿科学   192篇
妇产科学   141篇
基础医学   822篇
口腔科学   202篇
临床医学   738篇
内科学   1329篇
皮肤病学   76篇
神经病学   614篇
特种医学   395篇
外国民族医学   4篇
外科学   616篇
综合类   99篇
预防医学   579篇
眼科学   208篇
药学   553篇
中国医学   9篇
肿瘤学   256篇
  2021年   65篇
  2019年   64篇
  2018年   73篇
  2017年   58篇
  2016年   78篇
  2015年   86篇
  2014年   134篇
  2013年   189篇
  2012年   300篇
  2011年   324篇
  2010年   182篇
  2009年   165篇
  2008年   269篇
  2007年   286篇
  2006年   249篇
  2005年   274篇
  2004年   227篇
  2003年   246篇
  2002年   207篇
  2001年   228篇
  2000年   206篇
  1999年   176篇
  1998年   90篇
  1997年   58篇
  1996年   72篇
  1995年   50篇
  1994年   79篇
  1993年   59篇
  1992年   136篇
  1991年   156篇
  1990年   159篇
  1989年   174篇
  1988年   146篇
  1987年   125篇
  1986年   124篇
  1985年   110篇
  1984年   103篇
  1983年   61篇
  1982年   47篇
  1979年   76篇
  1978年   72篇
  1977年   58篇
  1976年   52篇
  1975年   47篇
  1974年   55篇
  1973年   62篇
  1972年   68篇
  1971年   54篇
  1970年   47篇
  1967年   50篇
排序方式: 共有6925条查询结果,搜索用时 31 毫秒
21.
Controversy about the use of restrictive behavioral procedures persists within the field of developmental disabilities. Many advocates and proponents of the use of exclusively nonrestrictive behavioral procedures have argued that restrictive procedures pose unacceptably high risks of adverse side effects and harm to the people who are treated with them. Yet, little is known about the extent to which procedures like timeout, manual restraint, and overcorrection are actually used in the treatment of people with developmental disabilities who manifest severe behavior disorders. In this article, data gathered on a national sample of people with developmental disabilities age 45 years and older are reviewed to ascertain the extent to which several restrictive procedures are being used in treatment. Findings indicate that these procedures are not being used in an indiscriminate manner.  相似文献   
22.
Depression is common in Parkinson's disease (PD) and affects 30 to 50% of all patients. In contrast to the wealth of research on depression in PD, little is known about the occurrence of depression in other movement disorders. The primary objective of the current study was to determine whether the high prevalence of depression symptoms seen in PD is also found in other movement disorders, by directly comparing rates of specific depression symptoms and depression severity across PD, dystonia, and essential tremor (ET). Three hundred and fifty-four patients with PD, 83 patients with dystonia, and 53 patients with ET completed the Beck Depression Inventory (BDI). We found no significant between-groups differences for depression severity, frequency, or endorsement of specific depression symptoms. Forty-eight percent of PD patients, 37.3% of dystonia patients, and 34% of ET patients were found to be at least mildly depressed (BDI score of 10 or higher). The most commonly endorsed symptoms were fatigability, difficulty with work, anhedonia, and sleep disturbance. Clinicians should be aware that depression is a frequent problem in dystonia and ET, in addition to PD, and inquire about depression symptoms in these patients so that they can be appropriately treated.  相似文献   
23.
The role of renal alpha 2-adrenoceptors in the regulation of glomerular filtration and renal perfusion is unknown. We studied the effects of alpha 2-adrenergic blockade on renal hemodynamics in six patients with insulin-dependent diabetes mellitus (IDDM) and in six healthy subjects. At the basal state, glomerular filtration rate (GFR) was higher in IDDM although the difference from control levels was not statistically significant. Volume expansion, achieved by infusion of isotonic sodium chloride solution, during placebo infusion induced a significant drop in GFR in healthy subjects but not in IDDM patients. Infusion of the alpha 2-adrenoceptor antagonist idazoxan did not further modify the effect of volume expansion on GFR. Renal plasma and blood flow as well as filtration fraction were not significantly changed by volume expansion or idazoxan infusion. Plasma renin activity and plasma aldosterone levels decreased during volume expansion in both IDDM and control subjects. In conclusion, volume expansion induced decreased GFR in healthy controls but not in IDDM patients. Since infusion of idazoxan did not affect GFR or other parameters of renal hemodynamics, renal alpha 2-adrenoceptors do not seem to be involved in the regulation of renal function. Hence, enhanced renal alpha 2-adrenoceptor activity is not likely to underlie hyperfiltration as seen in IDDM.  相似文献   
24.
A survey was conducted to ascertain the risk of tuberculosis (TB) among migrant farm workers on the Delmarva peninsula. Relevant histories were obtained from 842 migrants; a total of 709 skin tests were completed, and 239 sputum specimens were examined for acid-fast bacilli (AFB) and culture. No cases of infectious tuberculosis were ascertained by history or AFB examination. One sputum culture was positive for M. tuberculosis and 13 were positive for various species of nontuberculous mycobacteria. Thirty-seven per cent of migrants tested had significant skin test reactions of 10 mm or more. Reaction rates for men were 41 per cent and for women 25 per cent. Age specific rates ranged from 14 per cent in children aged 5-14 to 54 per cent for ages 45-54. Rates for the principal national/ethnic groups were Haitians 55 per cent, Mexicans 36 per cent, US Blacks 29 per cent and US-born Latinos 20 per cent. Based on these results and other information currently available, it is recommended that current Centers for Disease Control (CDC) recommendations for TB prophylaxis continue to be applied for migrant workers, but that mass screening by skin testing in camp populations not be emphasized. Other recommendations focus on: case finding of active disease, improving continuity and follow-up, increasing coordination among involved agencies, and actively supporting improved economic and living conditions for migrant farm workers.  相似文献   
25.
PURPOSE: Adjuvant chemotherapy, especially with anthracyclines, is known to cause acute and chronic cardiotoxicity in breast cancer patients. We studied the cardiac effects of chemotherapy in a population-based sample of breast cancer patients aged > or = 65 years with long-term follow-up. PATIENTS AND METHODS: In the Surveillance, Epidemiology, and End Results (SEER)-Medicare database, we analyzed treatments and outcomes among women > or = 65 years of age who were diagnosed with stage I to III breast cancer from January 1, 1992 to December 31, 1999. Propensity scores were used to control for baseline heart disease (HD) and other known predictors of chemotherapy, and Cox proportional hazards models were used to estimate the risk of cardiomyopathy (CM), congestive heart failure (CHF), and HD after chemotherapy. RESULTS: Of 31,748 women with stage I to III breast cancer, 5,575 (18%) received chemotherapy. Chemotherapy was associated with younger age, fewer comorbidities, hormone receptor negativity, multiple primary tumors, and advanced disease. Patients who received chemotherapy were less likely than other patients to have pre-existing HD (45% v 55%, respectively; P < .001). The hazard ratios for CM, CHF, and HD for patients treated with doxorubicin (DOX) compared with patients who received no chemotherapy were 2.48 (95% CI, 2.10 to 2.93), 1.38 (95% CI, 1.25 to 1.52), and 1.35 (95% CI, 1.26 to 1.44), respectively. The relative risk of cardiotoxicity among patients who received DOX compared with untreated patients remained elevated 5 years after diagnosis. CONCLUSION: When baseline HD was taken into account, chemotherapy, especially with anthracyclines, was associated with a substantially increased risk of CM. As the number of long-term survivors grows, identifying and minimizing the late effects of treatment will become increasingly important.  相似文献   
26.
Tetrahydrobiopterin is an essential co-factor in the natural synthesis of dopamine. Oral tetrahydrobiopterin was given in small doses to four patients with early Parkinson's disease but had no discernible effect.  相似文献   
27.
The Medical Outcomes Study HIV Health Survey (MOS-HIV) is a brief, comprehensive measure of health-related quality of life (HRQoL) used extensively in human immunodeficiency virus/acquired immune deficiency syndrome (HIV/AIDS). The 35-item questionnaire includes ten dimensions (health perceptions, pain, physical, role, social and cognitive functioning, mental health, energy, health distress and quality of life (QoL)) and takes approximately 5 minutes to complete. Subscales are scored on a 0–100 scale (a higher score indicates better health) and physical and mental health summary scores can be generated. The MOS-HIV has been shown to be internally consistent, correlate with concurrent measures of health, discriminate between distinct groups, predict future outcomes and be responsive to changes over time. Limited experience suggests acceptable reliability and validity in women, injecting drug users and African–American and lower socioeconomic status patients. The MOS-HIV is available in 14 languages and has been included as a secondary outcome measure in numerous clinical trials for all stages of disease. In several studies it has detected significant differences between treatments; in some cases concordant with conventional end-points and, in others, discordant. The interpretation of scores is facilitated by an explanation in terms meaningful to the intended audience. Research is needed to compare the MOS-HIV to other strategies for HRQoL assessment in early HIV disease.  相似文献   
28.
We investigated the effect of multiple freeze-thaw cycles on mumps, measles, and rubella virus serum antibody levels with whole-virus immunoglobulin G enzyme-linked immunoassays. Fresh serum samples from nine healthy adult volunteers were divided into six sets of five aliquots each. Samples were taken through a total of 10 freeze-thaw cycles and stored at 4°C until assayed. Each assay measurement was done in replicates of five, and the mean value was reported. After completing 10 freeze-thaw cycles, we found no clinically or statistically significant effect on measured antibody levels and found no discernible detrimental effect on the ability to measure these antibodies by enzyme-linked immunoassays.  相似文献   
29.
The effects of region of interest (ROI) selection and correction for Compton-scattered photons using a buildup factor on radionuclide left ventricular volumes calculated by the Links method were compared in 19 humans with contrast ventriculography and in phantoms. Three different methods of ROI selection were compared: a manual ROI, a second derivative ROI and a 50% count-threshold ROI. In phantoms without Compton scatter correction, volumes were overestimated by 30% (manual ROI), 20% (derivative ROI) and 1% (count threshold ROI). In subjects, results without Compton scatter correction were similar with overestimates of 50% (manual ROI) and 20% (derivative ROI) and an underestimate by 3% (count threshold method). Correction for Compton-scattered photons with the use of a phantom-derived buildup factor resulted in improved accuracy for the manual ROI (+15%) and the derivative ROI (0%). A 50% count threshold ROI following interpolative background subtraction allows the accurate calculation of cardiac volumes without the need for scatter correction, while a second derivative ROI method requires a correction for Compton scatter with the use of a buildup factor.  相似文献   
30.
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