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   36841篇
  免费   3799篇
  国内免费   53篇
耳鼻咽喉   480篇
儿科学   1009篇
妇产科学   748篇
基础医学   5260篇
口腔科学   1394篇
临床医学   4201篇
内科学   7367篇
皮肤病学   412篇
神经病学   2928篇
特种医学   1462篇
外国民族医学   2篇
外科学   4824篇
综合类   932篇
一般理论   30篇
预防医学   3848篇
眼科学   1018篇
药学   2809篇
  1篇
中国医学   27篇
肿瘤学   1941篇
  2021年   526篇
  2020年   333篇
  2019年   554篇
  2018年   607篇
  2017年   450篇
  2016年   475篇
  2015年   582篇
  2014年   819篇
  2013年   1215篇
  2012年   1677篇
  2011年   1763篇
  2010年   961篇
  2009年   940篇
  2008年   1550篇
  2007年   1657篇
  2006年   1511篇
  2005年   1587篇
  2004年   1440篇
  2003年   1377篇
  2002年   1357篇
  2001年   1093篇
  2000年   1152篇
  1999年   1069篇
  1998年   422篇
  1997年   364篇
  1996年   403篇
  1995年   374篇
  1994年   372篇
  1993年   355篇
  1992年   864篇
  1991年   844篇
  1990年   871篇
  1989年   788篇
  1988年   757篇
  1987年   742篇
  1986年   716篇
  1985年   727篇
  1984年   536篇
  1983年   500篇
  1982年   318篇
  1981年   323篇
  1980年   294篇
  1979年   471篇
  1978年   382篇
  1977年   311篇
  1976年   296篇
  1974年   374篇
  1973年   361篇
  1972年   297篇
  1971年   311篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
Hallucinations and associated factors in Alzheimer's disease.   总被引:1,自引:0,他引:1  
In a consecutive sample of 230 community-dwelling patients with probable Alzheimer's disease, a structured interview yielded evidence of current hallucinations in 29.1% and misperceptions in another 11.3%. Visual and auditory modalities were similarly represented in apparent hallucinations. Hallucinations prior to the current monitoring period were rare among patients with misperceptions or with no perceptual abnormality. The probability of hallucinations was associated with the severity of cognitive dysfunction, the degree of other behavioral disturbances, and the presence of extrapyramidal signs. A logistic regression model predicting hallucinations based on these diverse clinical features accurately classified 87.0% of the sample.  相似文献   
42.
Presumed accidental corneal exposure to Hibiclens (chlorhexidine 4% and detergent) in two patients resulted in severe and permanent corneal opacification. We investigated the corneal toxicity of Hibiclens by gross, biomicroscopic, and histopathologic studies of rabbit eyes exposed to Hibiclens for varying time intervals ranging from five to 15 minutes. Severe, irreversible, and progressive corneal damage resulted in all eyes studied.  相似文献   
43.
Heated sugar/amino acid reaction mixtures, known to contain products that are clastogenic and/or mutagenic to cells in vitro, were evaluated for clastogenic activity in mouse bone marrow using the erythrocyte micronucleus assay. Heated (i.e. browned) fructose/lysine reaction mixtures were also evaluated in the Salmonella his-reversion assay and the Chinese hamster ovary (CHO) cell chromosomal aberration assay to confirm and extend previous in vitro observations. Significant mutagenicity of fructose/lysine mixtures was observed in Salmonella typhimurium strains TA100, TA2637, TA98 and TA102, with greater activity in mixtures heated at pH 10 than at pH 7. S-9 decreased the activity in strains TA100, TA2637 and TA98, but increased the activity in strain TA102. Both pH 7 and pH 10 reaction mixtures of the fructose/lysine browning reaction were highly clastogenic in CHO cells. Heated mixtures of fructose and lysine, and of glucose or ribose with lysine, histidine, tryptophan or cysteine, did not increase the frequency of micronucleated erythrocytes in mice when administered by the oral route. This indicates the absence of chromosomal aberrations in erythrocyte precursor cells, and indicates that the genotoxic components of the browned mixtures are not absorbed and distributed to bone marrow cells in amounts sufficient to induce micronuclei when given orally. Because sugar/amino acid browning reactions occur commonly in heated foods, it is important to evaluate further the in vivo genotoxicity of browning products in cell populations other than bone marrow.  相似文献   
44.
The postnatal development of soma size and cytochrome oxidase activity was examined in the perigeniculate nucleus (PGN) and reticular nucleus of the thalamus (RNT). Neurons in the PGN and RNT exhibited a rapid increase in soma size between 2 and 4 weeks of age. During this period of cell growth there is an increase in the intensity of cytochrome oxidase staining within the cell body. Cells in both the PGN and RNT decrease in size after 4 weeks of age, and become very fusiform in shape. During this postnatal period, there is also a shift in cytochrome oxidase staining from the cell body to the dendrites.  相似文献   
45.
46.
Anticholinergic activity of a number of tricyclic antidepressives and nomifensine was demonstrated and their order of affinity for the cholinergic receptors of rat jejunum was determined. The influence of ethinyl estradiol and a conjugated estrogen product, Premarin on the binding of several tricyclic antidepressives to the hepatic mixed function oxidase system was investigated. The influence of these steroids on the metabolism of the antidepressives was evaluated and ethinyl estradiol was shown to have a marked influence on the metabolism of the antidepressives studied, while conjugated estrogens were shown to have little effect.  相似文献   
47.
In order to investigate the possible relationship between physical health and political violence in Northern Ireland a random sample of residents of four electoral areas (two with relatively high violence and two with relatively low violence) was interviewed at home. Each person was asked to rate their health in terms of common physical symptoms, to indicate their use of family doctor and hospital services, and to rate the level of political violence in their neighbourhood. Analysis of covariance (with a measure of psychological well-being, a measure of trait neuroticism plus age and socioeconomic status as covariates) revealed that women reported more physical symptoms than did men, people in the ‘high’ violence areas reported more symptoms than did those in the ‘low’ violence areas, while those who rated their own neighbourhood most highly in terms of perceived violence also reported the greatest number of physical symptoms. However, a series of χ2 tests revealed no association between political violence or perceived political violence and uptake of services.  相似文献   
48.
Single-antibiotic use for penetrating abdominal trauma   总被引:1,自引:0,他引:1  
A prospective randomized study compared the use of moxalactam disodium vs clindamycin phosphate and tobramycin sulfate for treatment of 190 patients with penetrating abdominal trauma. Twenty-seven patients were disqualified because of early death or failure to follow the protocol. The patients in each group were comparable regarding the cause and severity of injury. No significant difference was seen in the incidence of intra-abdominal infection between the moxalactam-treated group (13%) and the clindamycin- and tobramycin-treated group (9%). The intra-abdominal infection rate in patients with colon injuries (21%) was significantly increased when compared with the patients without colon injuries (6%), but the antibiotic regimen did not significantly change the infection rate. No evidence of bleeding problems from moxalactam were noted. Changes in prothrombin and partial thromboplastin times appeared to be related to shock rather than the use of moxalactam. The most severe coagulopathies occurred prior to moxalactam therapy and were seen only in those patients who had shock requiring 10 or more units of blood. Moxalactam is as effective as combination (clindamycin and tobramycin) antimicrobial therapy in patients with penetrating abdominal trauma.  相似文献   
49.
50.
The production and prevention of calcium paradox injury in myocardium was studied in a canine model of cardiopulmonary bypass with multidose, moderately hypothermic, crystalloid cardioplegic solution. During 4 1/2 hours of global ischemia, three groups of six dogs each received one of three histidine-buffered cardioplegic solutions (500 ml initially and 250 ml every 30 minutes) at 27 degrees C. Group 1 cardioplegic solution was calcium free, group 2 solution contained a trace amount of calcium chloride (70 mumols /L), and group 3 cardioplegic solution was calcium free but contained diltiazem (150 micrograms/kg body weight). Left ventricular function measured as percent control of developed pressure revealed significantly greater (p less than 0.05) recovery in groups 2 and 3. Triphenyltetrazolium chloride staining showed 35% +/- 9% (mean +/- standard error) of heart mass necrosis in group 1 versus 0% and 0.5% +/- 0.4% in groups 2 and 3, respectively (p less than 0.001). Electron microscopy revealed ultrastructural changes characteristic of calcium paradox injury in group 1 myocardium. Calcium paradox injury was produced in an in vivo model of global myocardial ischemia and multidose cardioplegia despite moderate hypothermia and non-coronary collateral flow. The addition of either trace levels of calcium or diltiazem to the cardioplegic solution was effective in preventing this injury.  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