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   1563篇
  免费   119篇
  国内免费   10篇
耳鼻咽喉   3篇
儿科学   45篇
妇产科学   49篇
基础医学   214篇
口腔科学   40篇
临床医学   146篇
内科学   358篇
皮肤病学   26篇
神经病学   145篇
特种医学   25篇
外科学   186篇
综合类   9篇
预防医学   194篇
眼科学   13篇
药学   122篇
中国医学   19篇
肿瘤学   98篇
  2024年   5篇
  2023年   12篇
  2022年   27篇
  2021年   55篇
  2020年   33篇
  2019年   59篇
  2018年   63篇
  2017年   41篇
  2016年   42篇
  2015年   44篇
  2014年   76篇
  2013年   90篇
  2012年   99篇
  2011年   104篇
  2010年   73篇
  2009年   55篇
  2008年   81篇
  2007年   74篇
  2006年   84篇
  2005年   82篇
  2004年   74篇
  2003年   55篇
  2002年   66篇
  2001年   29篇
  2000年   33篇
  1999年   36篇
  1998年   11篇
  1997年   13篇
  1996年   11篇
  1994年   9篇
  1992年   10篇
  1991年   9篇
  1990年   8篇
  1989年   12篇
  1988年   7篇
  1987年   7篇
  1986年   8篇
  1985年   7篇
  1983年   6篇
  1979年   6篇
  1976年   6篇
  1975年   4篇
  1974年   4篇
  1973年   6篇
  1972年   6篇
  1970年   8篇
  1969年   7篇
  1968年   5篇
  1967年   6篇
  1966年   6篇
排序方式: 共有1692条查询结果,搜索用时 15 毫秒
1.
The psychophysiological correlates of induced headaches were examined. Subjects with frequent muscle-contraction headaches, frequent migraine headaches, or infrequent headaches were exposed to a 1-h cognitive stressor while multiple electromyographic and cardiovascular measures were monitored. The stressor was associated with significant changes in all psychophysiological measures. Eleven of 16 headache subjects and 2 of 8 control subjects developed headaches. Significant associations between several psychophysiological variables and headache occurrence were found and individual differences in the association between psychophysiological variables and headaches intensity were examined. The results were consistent with the hypothesized role of cardiovascular factors in the pathophysiology of muscle-contraction headache. This was the first controlled demonstration of headaches occurring as a function of environmental stressors.This research was supported by Grant 5-R01-NS-1875 from the National Institute of Health.  相似文献   
2.
Many facial plastic surgeons have set up their own personal World Wide Web (WWW) pages with an electronic mail link to communicate with and educate prospective patients. The possible dilemma is in that these services are provided without actually meeting patients face to face. Also, despite the growing popularity of computer imaging systems, it is not clear whether the medical and legal advantages of using such a system outweigh the disadvantages. The purpose of this article is to evaluate these aspects and to provide some protective guidelines. An examination of possible causes of actions arising from computer imaging suggests that surgeons who follow a few simple guidelines, and who use computer imaging responsibly and cautiously, minimize their legal liability. Issues surrounding Internet discussion groups, posted medical advice, intellectual property, and the use of an electronic mail link are also discussed.  相似文献   
3.
Energy-impacted communities experience rapid population growth due to energy resource production. A high prevalence of psychological and social problems are frequently reported in such communities. The present research employed a standardized instrument and random sampling in a community needs assessment to document high prevalence of problems in an energy-impacted town that has attempted to plan for rapid growth. At least 35 percent of the men and 25 percent of the women randomly sampled in the community reported elevated levels of psychological distress; 48 percent of the men admitted to alcohol problems. How the local mental health center utilized the needs assessment results to improve services, obtain funding for needed programs, and generally promote the community's quality of life is described. Recommendations for social planning that go beyond the brick and mortar approach to community planning are provided; prevention services are recommended above traditional remedial mental health services for such circumstances.Tom Bougsty, Ph.D., and Prudy Marshall, Ph.D., are both at the SEW Mental Health Center in Cheyenne WY. Ernest Chavez, Ph.D., is at the Colorado State University at Fort Collins, CO. Requests for reprints should be directed to the first author at 118 W. 4th Ave., Cheyenne, WY 82001.  相似文献   
4.
The metabolic syndrome among postmenopausal women in Ecuador.   总被引:1,自引:0,他引:1  
BACKGROUND: The prevalence of the metabolic syndrome increases with age and after the onset of menopause, and may explain in part the apparent acceleration of cardiovascular disease in postmenopausal women. OBJECTIVE: To determine the prevalence of metabolic syndrome and related risk determinants among postmenopausal women in Ecuador. METHODS: Postmenopausal women >or=40 years of age, non-users of hormone therapy and with an intact uterus, were asked to participate in a metabolic syndrome screening and educational program at the Institute of Biomedicine of the Universidad Católica of Guayaquil, Ecuador. Sociodemographic data, waist circumference and blood pressure measurements were recorded, and a fasting blood sample obtained for serum glucose and lipid profile determinations. Woman were counseled and managed according to the results. Metabolic syndrome was defined in accordance with the criteria of the Third Adult Treatment Panel (ATP III). RESULTS: Three hundred and twenty-five postmenopausal women entered the program. Mean (+/-standard deviation) age was 55.9 +/- 8.1 years, 53.5% of them were aged >or=54 years (median). The prevalence of metabolic syndrome, according to ATP III criteria, was 41.5%. Using the same criteria, 38.8%, 16.6%, 56.9% and 54.2% of the women presented with hypertension, diabetes, hypertriglyceridemia and abdominal obesity, respectively. More than 40% of women determined to have hypertension or diabetes lacked knowing so. Logistic regression analysis determined that age increased the risk of presenting hypertension and diabetes (odds ratio (95% confidence interval): 2.0 (1.2-3.2) and 1.6 (0.9-3.0), respectively, p < 0.05), entities which in turn duplicated the risk of having high triglyceride levels. Sedentary women with <5 years since menopause onset were at higher risk of having abdominal obesity, which was directly related to diabetes and hypertension. CONCLUSIONS: In this postmenopausal Ecuadorian population the prevalence of the metabolic syndrome was high and its determinant factors related to age, time since menopause onset and sedentary habits. Because of the implications for cardiovascular risk, counseling programs directed toward high-risk populations should be encouraged.  相似文献   
5.
6.
Recurrence of ischemic placental disease   总被引:1,自引:0,他引:1  
OBJECTIVE: To test the hypothesis that the presence of preeclampsia, small for gestational age (SGA)-birth, and placental abruption in the first pregnancy confers increased risk in the second pregnancy. METHODS: A retrospective cohort study entailing a case-crossover analysis was performed based on women who had two consecutive singleton live births (n=154,810) between 1989 and 1997 in Missouri. Small for gestational age was defined as infants with birth weight below the 10th centile for gestational age. Risk and recurrence of ischemic placental disease was assessed from fitting logistic regression models after adjusting for several confounders. RESULTS: Preeclampsia in the first pregnancy was associated with significantly increased risk of preeclampsia (odds ratio 7.03, 95% confidence interval 6.51, 7.59), SGA (odds ratio 1.16, 95% confidence interval 1.06, 1.27), and placental abruption (odds ratio 1.90, 95% confidence interval 1.51, 2.38) in the second pregnancy. Similarly, women with SGA and abruption in the first pregnancy were associated with increased risks of all other conditions in the second pregnancy. CONCLUSION: Women with preeclampsia, SGA, and placental abruption in their first pregnancy--conditions that constitute ischemic placental disease--are at substantially increased risk of recurrence of any or all these conditions in their second pregnancy. Although causes of these conditions remain largely speculative, these entities may manifest through a common pathway of ischemic placental disease with significant risk of recurrence.  相似文献   
7.
8.
Conditional mouse knock-outs provide an informative approach to drug target validation where no pharmacological blockers exist or global knock-outs are lethal. Here, we used the Cre-loxP system to delete BDNF in most nociceptive sensory neurons. Conditional null animals were healthy with no sensory neuron loss. However, pain-related behavior was substantially altered. Baseline thermal thresholds were reduced. Carrageenan-induced thermal hyperalgesia was inhibited. Formalin-induced pain behavior was attenuated in the second phase, and this correlated with abolition of NMDA receptor NR1 Ser896/897 phosphorylation and ERK1 and ERK2 activation in the dorsal horn; AMPA receptor phosphorylation (GluR1/Ser831) was unaffected. NGF-induced thermal hyperalgesia was halved, and mechanical secondary hyperalgesia caused by intramuscular NGF was abolished. By contrast, neuropathic pain behavior developed normally. Nociceptor-derived BDNF thus plays an important role in regulating inflammatory pain thresholds and secondary hyperalgesia, but BDNF released only from nociceptors plays no role in the development of neuropathic pain.  相似文献   
9.
BACKGROUND: C-reactive protein (CRP), a marker of chronic subclinical inflammation (CSI), is related to cardiovascular mortality in the general and renal transplant populations. In the general population, high CRP levels are associated with pre-diabetic glucose homeostasis alterations which may contribute to the proatherogenic effect of CSI. METHODS: We studied 134 consecutive renal transplant recipients without pre-existing or new onset diabetes. CRP, oral glucose tolerance test, insulin sensitivity and HbA1c were measured. RESULTS: Among CRP tertiles, fasting glucose and glucose after 120 min were not different. However, HbA1c was higher (4.9+/-0.6; 5.2+/-0.5; 5.4+/-0.5; P=0.005] and insulin sensitivity lower (McAuley index: 7.2+/-2; 6.8+/-2; 6.2+/-1.3; P=0.042) in the third CRP tertile. In addition, HDL-cholesterol was lower and triglycerides and body mass index (BMI) higher in the third tertile. Consequently, metabolic syndrome was more prevalent in the upper CRP tertiles [11 (25%); 19 (43%); 22 (50%); P=0.01). In multivariate analyses, HbA1c was related to higher CRP levels (standardized beta coefficient=0.21, P=0.013), independently of BMI (standardized beta coefficient=0.24, P=0.005) and triglycerides (standardized beta coefficient=0.18; P=0.03). CONCLUSIONS: Subclinical glucose homeostasis alterations are related to chronic inflammation in renal transplant recipients without pre-existing or new onset diabetes and may contribute to their high cardiovascular mortality.  相似文献   
10.
BACKGROUND: The diagnosis of acute rejection (AR) relies on biopsy (Bx), with all the noninvasive tests failing to show satisfactory predictive value. Nitric oxide (NO) has been shown to play a role in AR. The aim of this study is to analyze the relationship between NO and (1) biopsy-proven allograft rejection and (2) other reasons of allograft dysfunction. PATIENTS AND METHODS: Fifty consecutive renal allograft recipients ages 23-72 yrs who were transplanted were prospectively recruited. Blood samples were collected for 3 months. Endogenous serum nitrate (SNO(3)) levels were measured with Griess reagent in 1178 samples. Biopsies were performed as clinically indicated. Tacrolimus levels, urinary cultures, and renal function tests were done as per unit protocol. RESULTS: Fifty recipients (mean+/-SD age 45.2+/-2.18 yrs, 24 men and 6 women) underwent 68 biopsies. Forty-five Bx (66.2%) showed AR in 19 recipients (mean age 47+/-8) and 23 (33.8%) Bx in 13 recipients (mean age 43+/-12) showed no AR. SNO(3) in AR was (73+/-8.89 micromol/L) compared with negative Bx (45+/-4.5 micromol/L; P<0.05). There was also a significant difference in SNO(3) during AR and other causes of allograft dysfunction; delayed graft function (54+/-7.8 micromol/L), urinary tract infection (44+/-2.9 micromol/L), tacrolimus toxicity (51+/-2.86 micromol/L), and increase in serum creatinine (44+/-2.36 micromol/L). CONCLUSION: There is a significant increase of serum nitrate with episodes of acute rejection compared with other causes of renal dysfunction. SNO(3) can therefore aid in the diagnosis of acute rejection.  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