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   2989篇
  免费   226篇
  国内免费   11篇
耳鼻咽喉   32篇
儿科学   85篇
妇产科学   22篇
基础医学   454篇
口腔科学   56篇
临床医学   294篇
内科学   632篇
皮肤病学   30篇
神经病学   150篇
特种医学   339篇
外科学   461篇
综合类   66篇
一般理论   1篇
预防医学   171篇
眼科学   33篇
药学   143篇
肿瘤学   257篇
  2021年   41篇
  2019年   27篇
  2018年   40篇
  2017年   34篇
  2016年   35篇
  2015年   36篇
  2014年   62篇
  2013年   77篇
  2012年   111篇
  2011年   122篇
  2010年   96篇
  2009年   85篇
  2008年   99篇
  2007年   111篇
  2006年   112篇
  2005年   106篇
  2004年   95篇
  2003年   93篇
  2002年   72篇
  2001年   90篇
  2000年   67篇
  1999年   65篇
  1998年   74篇
  1997年   79篇
  1996年   76篇
  1995年   60篇
  1994年   60篇
  1993年   49篇
  1992年   56篇
  1991年   61篇
  1990年   58篇
  1989年   69篇
  1988年   69篇
  1987年   61篇
  1986年   61篇
  1985年   69篇
  1984年   45篇
  1983年   50篇
  1982年   41篇
  1981年   27篇
  1980年   28篇
  1979年   47篇
  1978年   31篇
  1977年   31篇
  1976年   40篇
  1974年   30篇
  1973年   30篇
  1972年   27篇
  1971年   25篇
  1970年   28篇
排序方式: 共有3226条查询结果,搜索用时 15 毫秒
51.
52.
The omega neurons (ON1s) are a mirror-symmetrical pair of identified prothoracic auditory interneurons of crickets which have been previously described as intraganglionic. Using intracellular techniques we stained ON1s of female Teleogryllus oceanicus and found that many ON1s have axons which project anteriorly out of the prothoracic ganglion. The ascending axon arises contralateral to the soma at the most anteriolateral bend of the bow-shaped process of an otherwise "archetypical" ON1 and travels up the neck connective in a ventral position just inside the connective tissue sheath. The occurrence of the ascending axon is age-dependent. Seventy-five percent of ON1s stained in late nymphal stages and in young adults had an ascending axon while only 30% of ON1s in older adults had an ascending axon. Evidence is presented to show that ON1s having ascending axons are developmental variants of the "archetypical" ON1 and do not represent a separate neuron type. The two morphological types of ON1s are not distinguishable on the basis of their responses to sound stimuli having carrier frequencies of 3.5-60 kHz. Although we know that the ascending axon conducts action potentials, its target and terminal morphology are not yet known.  相似文献   
53.
BackgroundThe use of immune checkpoint inhibitors combined with vascular endothelial growth factor (VEGF)-targeted therapy as second-line treatment for metastatic clear cell renal cancer (mRCC) has not been evaluated prospectively.ObjectiveTo evaluate the efficacy and safety of atezolizumab + bevacizumab following disease progression on atezolizumab or sunitinib monotherapy in patients with mRCC.Design, setting, and participantsIMmotion150 was a multicenter, randomized, open-label, phase 2 study of patients with untreated mRCC. Patients randomized to the atezolizumab or sunitinib arm who had investigator-assessed progression as per RECIST 1.1 could be treated with second-line atezolizumab + bevacizumab.InterventionPatients received atezolizumab 1200 mg intravenously (IV) plus bevacizumab 15 mg/kg IV every 3 wk following disease progression on either atezolizumab or sunitinib monotherapy.Outcome measurements and statistical analysisThe secondary endpoints analyzed during the second-line part of IMmotion150 included objective response rate (ORR), progression-free survival (PFS), and safety. PFS was examined using Kaplan-Meier methods.Results and limitationsFifty-nine patients in the atezolizumab arm and 78 in the sunitinib arm were eligible, and 103 initiated second-line atezolizumab + bevacizumab (atezolizumab arm, n = 44; sunitinib arm, n = 59). ORR (95% confidence interval [CI]) was 27% (19–37%). The median PFS (95% CI) from the start of second line was 8.7 (5.6–13.7) mo. The median event follow-up duration was 19.4 (12.9–21.9) mo among the 25 patients without a PFS event. Eighty-six (83%) patients had treatment-related adverse events; 31 of 103 (30%) had grade 3/4 events. Limitations were the small sample size and selection for progressors.ConclusionsThe atezolizumab + bevacizumab combination had activity and was tolerable in patients with progression on atezolizumab or sunitinib. Further studies are needed to investigate sequencing strategies in mRCC.Patient summaryPatients with advanced kidney cancer whose disease had worsened during treatment with atezolizumab or sunitinib began second-line treatment with atezolizumab + bevacizumab. Tumors shrank in more than one-quarter of patients treated with this combination, and side effects were manageable.  相似文献   
54.

Two types of sex education are generally offered in the U.S. abstinence-only and comprehensive sex education. There is no clear scientific consensus over which approach minimizes the risk of unintended pregnancy and sexually transmitted diseases for youth. While there have been many studies of specific programs in clinical or quasi-experimental settings, there are very few evaluations of how state-level sex education policies affect the youth population. We estimate the impact of various state-level sex education policies on youth sexual activity and contraceptive use using data from four waves of the Youth Risk Behavior Surveillance System from 39 states. We found that states that require sexuality (sex and/or HIV/STD) education and contraceptive content or states that mandate education but leave the actual content up to local districts have lower rates of sexually active youth and higher rates of contraception use when youth are sexually active. States that require sexuality education and require abstinence content increase the rate at which youth are sexually active, and youth in those states are less likely to use hormonal birth control if they are sexually active. In conclusion, we found that state policies regarding sex and HIV/STD education had statistically significant effects that are meaningful in magnitude from a public health perspective.

  相似文献   
55.
The search for alternatives to metered-dose inhalers has accelerated recently in a bid to find effective products that do not use chlorofluorocarbon (CFC) propellants. This paper reviews the factors to be considered in developing dry powder inhalers (DPIs), particularly the formulation, metering design and flow path in the device. The advantages and disadvantages of current DPIs are discussed and possible future approaches outlined.  相似文献   
56.
This is the first report of the association of spina bifida and eating disorders. Five patients were diagnosed rather late in the course of their illness. They all had been overweight premorbidly and had been urged to lose weight for years in order to improve their mobility. As they dieted, they experienced their weight loss as a source of power that could somehow compensate for their losses and neurologic limitations. They responded to a multidisciplinary intervention. Clinicians taking care of patients with spina bifida need to be cognizant that they may be at risk of developing an eating disorder. Such awareness should influence the quality of nutritional counseling (prevention aspect) and the clinical assessment of sudden weight loss (early intervention).  相似文献   
57.
A strong relationship exists between employee satisfaction and patients' perceptions of the quality of their care, measured in terms of their intent to return and to recommend the hospital to others. Employee dissatisfaction can negatively affect quality of care and have an adverse effect on patient loyalty and, thus hospital profitability. Therefore, health care marketers should regularly measure employee satisfaction as one way to monitor service quality. Health care marketers must work more closely with their human-resource departments to understand and influence employees' work environment and maintain a high level of job satisfaction. Marketers also should place an increased emphasis on both employee and patient perceptions of satisfaction when developing internal and external strategic marketing plans and formulating future research.  相似文献   
58.
Fever: the old and the new   总被引:2,自引:0,他引:2  
Early concepts of fever as a major feature of illness range from those of Hippocrates to those present in the Bible and have influenced cultural attitudes during several major European pandemics of both black plague and tuberculosis, the "white plague" of the early 19th century. Evolving ideas of thermoregulation and fever in the 19th century followed the first extensive use of the clinical thermometer by Wunderlich. Experimental studies on the pathogenesis of fever during the last 30 years suggest that fever and certain aspects of both immunoregulation and inflammation are produced by a single hormone, the monokine interleukin-1, which has presumably been selected by evolution to protect the host against infection.  相似文献   
59.
Our experience of 54 patients with end-stage renal failure, who were treated with intermittent peritoneal dialysis and compared with patients maintained by haemodialysis over the years 1972 to 1978, has been reviewed. All patients received peritoneal dialysis for more than six weeks. The total experience was 32.8 patient dialysis-years, 48% as home dialysis. Peritoneal dialysis was used as an interim procedure in 19 patients who were waiting for haemodialysis. However, in 35 patients (particularly in the very young and elderly, and in situations of poor social support), recurrent peritoneal dialysis was chosen as the definitive dialysis therapy. Dialysis was assessed as "adequate" in all, but two, patients. The major complication of peritoneal dialysis was peritonitis, although its over-all incidence of 1.31 episodes per patient dialysis-year was low. An attack of peritonitis occurred every nine months of patient exposure, though the incidence of bacterial peritonitis averaged only once every 26 months. Fifty per cent of patients never had an episode of peritonitis. Intermittent peritoneal dialysis was associated with greater morbidity and mortality than haemodialysis, perhaps due, in part, to the older age of the peritoneal dialysis group. Intermittent peritoneal dialysis is a valuable adjunct to haemodialysis and transplantation in the treatment of end-stage renal failure.  相似文献   
60.
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