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   3312670篇
  免费   268870篇
  国内免费   13500篇
耳鼻咽喉   44922篇
儿科学   102612篇
妇产科学   83963篇
基础医学   529656篇
口腔科学   89200篇
临床医学   297581篇
内科学   576807篇
皮肤病学   90516篇
神经病学   281013篇
特种医学   131191篇
外国民族医学   225篇
外科学   512575篇
综合类   100233篇
现状与发展   23篇
一般理论   2188篇
预防医学   273487篇
眼科学   75953篇
药学   232633篇
  27篇
中国医学   9967篇
肿瘤学   160268篇
  2021年   55025篇
  2020年   35056篇
  2019年   57922篇
  2018年   70837篇
  2017年   54009篇
  2016年   59718篇
  2015年   73966篇
  2014年   108190篇
  2013年   173307篇
  2012年   88159篇
  2011年   87355篇
  2010年   115609篇
  2009年   120371篇
  2008年   74257篇
  2007年   76731篇
  2006年   87818篇
  2005年   82840篇
  2004年   84661篇
  2003年   75739篇
  2002年   65437篇
  2001年   107058篇
  2000年   99896篇
  1999年   98825篇
  1998年   65005篇
  1997年   62828篇
  1996年   60593篇
  1995年   56156篇
  1994年   50045篇
  1993年   46802篇
  1992年   68009篇
  1991年   64355篇
  1990年   61409篇
  1989年   60528篇
  1988年   55519篇
  1987年   54004篇
  1986年   51203篇
  1985年   50929篇
  1984年   46664篇
  1983年   42686篇
  1982年   40778篇
  1981年   38379篇
  1980年   36316篇
  1979年   37668篇
  1978年   33360篇
  1977年   31342篇
  1976年   28143篇
  1975年   27036篇
  1974年   27209篇
  1973年   26176篇
  1972年   24572篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
Vaccine cuisine.   总被引:1,自引:0,他引:1       下载免费PDF全文
  相似文献   
993.
994.
Omeprazole is a member of a new class of substituted benzimidazoles. These agents inhibit the proton pump in the gastric parietal cell, blocking the final step in the gastric acid secretory pathway. Omeprazole has been investigated for the treatment of gastric ulcer, duodenal ulcer, gastroesophageal reflux, and various hypersecretory states. The prolonged inhibition of gastric acid secretion allows for once-daily dosing in patients with peptic ulcer disease and gastroesophageal reflux, and once- or twice-daily dosing in patients with Zollinger-Ellison syndrome. Compared with currently available therapies, omeprazole is well tolerated and demonstrates a more rapid ulcer healing rate. It is superior to conventional therapies in the treatment of Zollinger-Ellison syndrome. Side effects are infrequent when the drug is used for the short-term management of ulcers.  相似文献   
995.
Agenesis of the Gallbladder Revisited Laparoscopically   总被引:1,自引:0,他引:1  
Gallbladder agenesis is an extremely rare disease. Necropsy incidence has been reported to be 0.016%. Failure lo locate the gallbladder at the time of a planned cholecystectomy can be very challenging. We report such a case during a laparoscopic cholecystectomy. The indication for surgery in these patients are complaints of gallbladder symptoms along with a false-positive ultrasound study. During exploration, an abnormal location of the gallbladder has to be excluded. Ectopic gallbladder locations include intrahepatic, lesser omentum, retroperitoneal, retrohepatic, within the falciform ligament, retroduodenal, and retrohepatic areas. Thorough exploration and cholangiography are essential. Embryologically, the gallbladder and cystic duct arise from the caudal portion of the hepatic bud. All of the previously reported cases of gallbladder agenesis have shown an absence of both the gallbladder and cystic duct. We report an embryological oddity wherein a patent cystic duct was found along with an agenetic gallbladder. This is the first case report of this finding, along with this being the first absent gallbladder discovered laparoscopically.  相似文献   
996.
The vasomotor response of native human collateral vessels to pharmacologic or hemodynamic vasodilatory stimuli is not well known. We describe a case where retrograde collateral flow velocity was measured both at baseline and following selected hemodynamic and pharmacologic interventions. This index case represents the first in a series of potential human physiologic studies designed to address questions pertaining to control of collateral blood supply in humans. © 1993 Wiley-Liss, Inc.  相似文献   
997.
Background: The management and follow-up of asthma patients presenting at Accident and Emergency (A&E) departments have mostly been studied in children's hospitals or specialised teaching hospitals. Aims: To study the adequacy of assessment, treatment and follow-up of patients presenting at A&E departments in non-teaching hospitals. Methods: A twenty-five per cent sample of presentations to A&E departments in all public hospitals in the Illawarra for one year was selected for a case note audit. Information on demographics, assessment, management and referral was extracted from the A&E case notes and medical records of cases with documentation of a final diagnosis of asthma. Chi square and Fischer's Exact tests were used for comparisons among hospitals. Results: Of 359 presentations with a final diagnosis of asthma, 88% were self referred and only 5% were first presentations. Objective measures of airways obstruction was not documented in 34% of admissions and 48% of nonadmissions. There was no documented follow-up in 28% of cases. The assessment and management of asthma in A&E was significantly poorer in smaller hospitals. Conclusion: Evidence of high use of A&E as a primary care facility by asthma patients was found in the study. There is a need to implement protocols to optimise assessment and treatment of asthma in smaller hospitals. (Aust NZ J Med 1993; 23: 672–677.).  相似文献   
998.
The region is characterized by diversity in cultural, political, economic and health conditions. Blindness in the region varies from 6.4% to 0.2% with cataract ranking highly as an underlying cause. There is a need to develop national policies to deliver affordable, technically suitable, and cost effective management plans to reduce cataract. Economic, demographic, health, and manpower statistics are essential information to be considered in formulating such policies.  相似文献   
999.
Diarrhetic shellfish poisoning (DSP) is a serious and globally widespread phytoplankton-related seafood illness. Although DSP is rarely life-threatening, it causes incapacitating diarrhea and vomiting with no known medical treatments. In addition, phytoplankton producing DSP toxins have been identified in temperate coastal waters worldwide, and their numbers may be increasing as a result of coastal eutrophication. The toxic effects of the major DSP toxins, okadaic acid and dinophysistoxin-1 (35-methylokadaic acid), appear to originate from their inhibitory activity against a family of structurally related serine/threonine protein phosphatases (PSPases). In particular, the inhibition of essential PSPases (e.g. PP1 and PP2A) has catastrophic consequences in most eukaryotic cells. Exploiting the potent inhibitory property of the DSP toxins, we have developed an enzyme-based assay (PP2A assay) capable of detecting both okadaic acid and dinophysis- toxin-1 in nanogram amounts. The assay employs purified PP2A, which has an extremely high affinity for both DSP toxins. This provides the PP2A assay with a level of sensitivity comparable to, or surpassing, that of most monoclonal antibody probes. To evaluate the PP2A assay as a means of detecting contaminated shellfish, a series of spike recovery experiments was conducted. The findings from these studies suggest that the PP2A assay has the potential for development into a rapid and relatively simple method for detecting PSPase inhibitors in crude extracts produced from shellfish.  相似文献   
1000.
Transcranial magnetic stimulation (TMS) and transcranial electrical stimulation (TES) of the human motor cortex produce a silent period (SP) following motor evoked potentials (MEPs). The early part of the SP can be explained by decreased alpha motor neuron excitability, whereas the late part is presumably due to suprasegmental mechanisms. In order to determine the level of the suprasegmental contribution to the generation of SPs, we recorded excitatory and inhibitory responses to TMS, TES, and percutaneous electrical brainstem stimulation (PBS) in the voluntarily activated first dorsal interosseous muscle of the hand. Stimulus intensities were set so that PBS and TES induced MEPs with areas equal to or larger than those of MEPs obtained with TMS. This procedure revealed that SPs were 49% and 83% shorter with TES and PBS, respectively, than with TMS. As TMS is more effective than TES or PBS in activating cortical interneurons, these findings support the idea that a significant component of the SP arises from intracortical mechanisms.  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