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   1273篇
  免费   90篇
  国内免费   22篇
耳鼻咽喉   4篇
儿科学   63篇
妇产科学   9篇
基础医学   132篇
口腔科学   46篇
临床医学   120篇
内科学   283篇
皮肤病学   38篇
神经病学   50篇
特种医学   320篇
外科学   72篇
综合类   43篇
预防医学   77篇
眼科学   9篇
药学   48篇
中国医学   2篇
肿瘤学   69篇
  2022年   6篇
  2021年   6篇
  2020年   6篇
  2019年   10篇
  2018年   8篇
  2017年   12篇
  2016年   13篇
  2015年   16篇
  2014年   25篇
  2013年   22篇
  2012年   42篇
  2011年   33篇
  2010年   35篇
  2009年   32篇
  2008年   57篇
  2007年   40篇
  2006年   36篇
  2005年   37篇
  2004年   38篇
  2003年   27篇
  2002年   33篇
  2001年   33篇
  2000年   34篇
  1999年   31篇
  1998年   41篇
  1997年   55篇
  1996年   53篇
  1995年   41篇
  1994年   26篇
  1993年   39篇
  1992年   46篇
  1991年   29篇
  1990年   37篇
  1989年   34篇
  1988年   39篇
  1987年   52篇
  1986年   34篇
  1985年   22篇
  1984年   14篇
  1983年   13篇
  1982年   17篇
  1981年   21篇
  1980年   18篇
  1979年   11篇
  1978年   10篇
  1977年   10篇
  1976年   22篇
  1975年   10篇
  1974年   5篇
  1926年   4篇
排序方式: 共有1385条查询结果,搜索用时 390 毫秒
31.
BACKGROUND. Although psychoactive medications have substantial side effects in the elderly, these drugs are used frequently in nursing homes. Few interventions have succeeded in changing this situation, and little is known about the clinical effects of such interventions. METHODS. We studied six matched pairs of nursing homes; at one randomly selected nursing home in each pair, physicians, nurses, and aides participated in an educational program in geriatric psychopharmacology. At base line we determined the type and quantity of drugs received by all residents (n = 823), and a blinded observer performed standardized clinical assessments of the residents who were taking psychoactive medications. After the five-month program, drug use and patient status were reassessed. RESULTS. Scores on an index of psychoactive-drug use, measuring both the magnitude and the probable inappropriateness of medication use, declined significantly more in the nursing homes in which the program was carried out (experimental nursing homes) than in the control nursing homes (decrease, 27 percent vs. 8 percent; P = 0.02). The use of antipsychotic drugs was discontinued in more residents in the experimental nursing homes than in the control nursing homes (32 percent vs. 14 percent); the comparable figures for the discontinuation of long-acting benzodiazepines were 20 percent vs. 9 percent, and for antihistamine hypnotics, 45 percent vs. 21 percent. In the experimental nursing homes residents who were initially taking antipsychotic drugs showed less deterioration on several measures of cognitive function than similar residents in the control facilities, but they were more likely to report depression. Those who were initially taking benzodiazepines or antihistamine hypnotic agents reported less anxiety than controls but had more loss of memory. Most other measures of clinical status remained unchanged in both groups. CONCLUSIONS. An educational program targeted to physicians, nurses, and aides can reduce the use of psychoactive drugs in nursing homes without adversely affecting the overall behavior and level of functioning of the residents.  相似文献   
32.
Three cases are presented with computed tomographic evidence of gas in retroperitoneal soft tissues in association with the so-called "vacuum phenomenon" (Knutsson sign) in lumbar disks. We review the explanations of Knutsson sign and offer an explanation of how extradiscal gas can occur in association with it.  相似文献   
33.
Over the past 30 years, an explosion in health care expenditures has occurred. Prior to 1960, health care accounted for 4.4% of the U.S. Gross National Product; today it is 11%. Before rational solutions to controlling this rise can be proposed, we must determine whether the care that we are currently paying for is appropriate to the needs of the elderly. This paper analyzes the literature regarding appropriateness of acute care provided to the elderly. We identified 17 articles that explicitly cited appropriate or inappropriate care (including under-, over- and misuse) provided in hospital and ambulatory settings and for procedures, and 19 articles that presented data on the appropriateness of medication use in the elderly. Virtually every study included in this review found at least double-digit levels of inappropriate care. Perhaps as much as one-fifth to one-quarter of acute hospital services or procedures were felt to be used for equivocal or inappropriate reasons, and two-fifths to one-half of the medications studied were overused in outpatients. The few studies that examined underuse or misuse of services also documented the existence of these phenomena. This was especially true for the ambulatory care of chronic physical and mental conditions and concerned the use of low-cost technologies (visits, preventive services, some medications). Thus, we conclude that there appears to be a substantial problem in the matching of acute services to the needs of elderly patients. This mismatch occurs both in terms of overuse and underuse, at least for areas where research has been conducted.  相似文献   
34.
In this prospective, randomized study, 23 patients having spinal anaesthesia for transurethral prostatectomy (TURP) were evaluated for the adequacy of their block using a visual analog pain score (V4 PS). Each patient with a “standard”(≥T10) block level (n = 5) or “intermediate” (L1 or T12) block level (n = 5) found the block adequate. Sixty-two percent (8/13) of patients with a “low”-L3) block level found their block adequate. The VAPS was assessed every five minutes or whenever pain abruptly increased during TURP; an “inadequate block” was defined as a V4 PS ≥ 5 /10 during prostatic resection. Intravesical pressure was monitored and kept <15 mmHg to distinguish between pain from bladder distension and from prostatic resection. “Low” block patients (LBP) who found their block inadequate (n = 5) received supplemental intrathecal local anaesthetic given through a spinal catheter. The subsequent L1 block level was adequate for TURP. In LBP, who found their block adequate (n = 8), a higher (P < 0.01) VAPS was observed than in patients with a “standard” block level. However, a smaller (P < 0.05) maximum percent decrease in diastolic blood pressure was found in LBPs, than in “intermediate” or “standard” block patients. It is concluded that a spinal block ≥L1) is adequate during TURP when bladder pressure is monitored and kept low. Mid-lumbar block levels should be reserved for patients in whom the benefit of minimizing haemodynamic changes outweighs the risk of a “less complete” anaesthetic.  相似文献   
35.
To analyze the optimal timing strategy for the detection of hypervascular liver tumors during the arterial phase of magnetic resonance (MR) imaging, a test examination after injection of 2 mL of gadopentetate dimeglumine was performed in 47 patients. The time course of the tumor-to-liver contrast-to-noise ratio (CNR) for all studies together was determined relative to the start of injection, the time of peak aortic enhancement, and the time of peak enhancement in the tumor. All studies were grouped together and the highest CNR was transiently observed at the time of peak tumor enhancement. This CNR was significantly higher than those observed at fixed delays after peak aortic enhancement. However, the CNRs at peak tumor enhancement+/-1.5 seconds did not differ significantly from those obtained after peak aortic enhancement. Finally, the CNRs obtained at fixed delays after the start of injection remained significantly lower. In hypervascular liver tumors, a higher CNR can be obtained during the arterial phase when the MR imaging delay is determined relative to the time of peak enhancement in the tumor or the aorta rather than being fixed after the start of contrast material injection. Timing based on the enhancement profile in the tumor rather than in the aorta should be performed only if rapid MR imaging is available with a time resolution of about 1.5 seconds to image the whole liver.  相似文献   
36.
37.
OBJECTIVE: Alcohol use disorders (defined as DSM-IV alcohol dependence or abuse) are prevalent and serious problems among adolescents. As adolescence is marked by progressive hippocampal development, this brain region may be particularly susceptible to the adverse effects of adolescent alcohol use disorders. This study compared the hippocampal volumes of adolescents and young adults with adolescent-onset alcohol use disorders to those of healthy matched comparison subjects. METHOD: Magnetic resonance imaging was used to measure the hippocampal volumes and volumes of comparison brain regions in 12 subjects with alcohol use disorders and 24 comparison subjects matched on age, sex, and handedness. RESULTS: Both left and right hippocampal volumes were significantly smaller in subjects with alcohol use disorders than in comparison subjects. Total hippocampal volume correlated positively with the age at onset and negatively with the duration of the alcohol use disorder. Intracranial, cerebral, and cortical gray and white matter volumes and measures of the mid-sagittal area of the corpus callosum did not differ between groups. CONCLUSIONS: In the mature brain, chronic alcohol use disorders are associated with graded global brain dysmorphology. Although the etiology, neuropsychological consequences, and permanence of these hippocampal findings need to be further examined, these findings suggest that, during adolescence, the hippocampus may be particularly susceptible to the adverse effects of alcohol.  相似文献   
38.
Intestinal permeability can be assessed non-invasively using the lactulose-rhamnose (L-R) test, which is a reliable measure of small intestinal integrity. AIMS: To determine risk factors for abnormal intestinal permeability in kwashiorkor, and to measure changes in L-R ratios with inpatient rehabilitation. DESIGN: A case-control study of 149 kwashiorkor cases and 45 hospital controls. The L-R test was adapted to study kwashiorkor in Malawi, with testing at weekly intervals during nutritional rehabilitation. Urine sugars were measured by thin layer chromatography in London. RESULTS: The initial geometric mean L-R ratios (x100) (with 95% confidence interval) in kwashiorkor were 17.3 (15.0 to 19.8) compared with 7.0 (5.6 to 8.7) for controls. Normal ratios are < 5, so the high ratios in controls indicate tropical enteropathy syndrome. Abnormal permeability in kwashiorkor was associated with death, oliguria, sepsis, diarrhoea, wasting and young age. Diarrhoea and death were associated with both decreased L-rhamnose absorption (diminished absorptive surface area) and increased lactulose permeation (impaired barrier function) whereas nutritional wasting affected only L-rhamnose absorption. Despite, clinical recovery, mean L-R ratios improved little on treatment, with mean weekly ratios of 16.3 (14.0 to 19.0), 13.3 (11.1 to 15.9) and 14.4 (11.0 to 18.8). CONCLUSION: Abnormal intestinal permeability in kwashiorkor correlates with disease severity, and improves only slowly with nutritional rehabilitation.  相似文献   
39.
Challa  A; Rao  DR; Reddy  BS 《Carcinogenesis》1997,18(10):2023-2026
Several epidemiological studies point to a strong correlation between nutrient composition of the diet and cancer of the colon. Phytic acid, present in grains, has been credited with reducing the risk of cancer of the colon. A number of reports are available indicating the benefits of green tea consumption in reducing the risk of stomach, lung and skin cancer, but little data are available on the effect of green tea in reducing the risk of colon cancer. Also, there are no studies on the combined effect of these compounds on colon tumorigenesis. Thus the primary objective of this investigation was to elucidate the combined effects of green tea and phytic acid on colonic preneoplastic lesions and the Phase II enzyme glutathione S-transferase. Fisher 344 male weanling rats were divided into nine groups of 15 rats each and fed the experimental diet for 13 weeks. Rats received two s.c. injections of azoxymethane in saline at 16 mg/kg body wt at 7 and 8 weeks of age. Rats received three levels (0, 1 and 2%) of phytic acid with three levels (0, 1 and 2%) of green tea within each phytic acid level in a 3 x 3 factorial experiment. Results indicate that while green tea had a marginal effect (P < 0.14), phytic acid significantly reduced the incidence of aberrant crypt foci (P < 0.008). The interaction between green tea and phytic acid was significant (P < 0.029 for distal and < 0.0168 for entire colon) and positive, pointing to a synergistic effect of green tea and phytic acid.   相似文献   
40.
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