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   3624953篇
  免费   256427篇
  国内免费   9490篇
耳鼻咽喉   48956篇
儿科学   120108篇
妇产科学   99576篇
基础医学   509968篇
口腔科学   102200篇
临床医学   331998篇
内科学   706628篇
皮肤病学   85536篇
神经病学   293263篇
特种医学   137605篇
外国民族医学   941篇
外科学   541041篇
综合类   77868篇
现状与发展   8篇
一般理论   1392篇
预防医学   277278篇
眼科学   84074篇
药学   264855篇
  12篇
中国医学   7996篇
肿瘤学   199567篇
  2019年   28708篇
  2018年   40904篇
  2017年   31189篇
  2016年   35510篇
  2015年   40225篇
  2014年   55672篇
  2013年   83215篇
  2012年   112223篇
  2011年   118826篇
  2010年   71163篇
  2009年   67555篇
  2008年   110617篇
  2007年   117799篇
  2006年   119399篇
  2005年   114557篇
  2004年   110260篇
  2003年   106017篇
  2002年   102416篇
  2001年   175878篇
  2000年   180002篇
  1999年   151408篇
  1998年   43082篇
  1997年   37967篇
  1996年   38066篇
  1995年   36892篇
  1994年   33736篇
  1993年   31599篇
  1992年   117157篇
  1991年   112988篇
  1990年   109364篇
  1989年   105649篇
  1988年   96609篇
  1987年   94622篇
  1986年   88845篇
  1985年   84820篇
  1984年   63238篇
  1983年   53658篇
  1982年   31489篇
  1981年   28064篇
  1979年   55943篇
  1978年   39277篇
  1977年   33431篇
  1976年   31176篇
  1975年   32984篇
  1974年   39341篇
  1973年   37600篇
  1972年   35118篇
  1971年   32586篇
  1970年   30122篇
  1969年   28780篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Seventy seven antral biopsies were collected from patients attending endoscopy clinic at King Khalid University Hospital, Riyadh, Saudi Arabia during a period of six months between December 1988 to May 1989. Of these 69 (89.6%) showed chronic gastritis as well as Helicobacter-like organisms (HLOs) in the biopsy specimens while 63 (81.8%) of biopsies grew Helicobacter pylori on culture. These findings indicate a good correlation between the histological diagnosis of chronic gastritis and isolation of H. pylori on culture.  相似文献   
992.
993.
Endourological experience with cystine calculi and a treatment algorithm   总被引:2,自引:0,他引:2  
Between May 1984 and January 1988, 18 patients (31 pyeloureteral units) with documented symptomatic cystine stones were treated. Stone size ranged from 5 to 56 mm. in largest diameter, with an average of 21 mm. All pyeloureteral units were treated initially by endourological methods, including ureteroscopy in 10, percutaneous ultrasonic lithotripsy in 9, extracorporeal shock wave lithotripsy (ESWL) in 10 and chemolysis in 2. Of the patients 10 required a combination of these technologies and 2 required an open operation. Of the 31 units 23 were free of stones when the patient was discharged from the hospital. Of 8 patients with retained stones only 3 had fragments greater than 3 mm. in diameter. Based on this experience an algorithm was developed for the urological management of cystine stones. Ureteral calculi may be removed by ureteroscopic techniques or manipulated into the renal pelvis and managed as renal stones. Cystine renal calculi of less than 1.5 cm. may be treated with ESWL monotherapy. Stones of 1.5 to 3 cm. may be treated with ESWL and dissolution, or percutaneous ultrasonic lithotripsy plus dissolution. Staghorn calculi may be treated by percutaneous ultrasonic lithotripsy plus ESWL and/or dissolution for retained fragments.  相似文献   
994.
995.
Circulating immune complexes in pre-eclampsia.   总被引:3,自引:0,他引:3  
Serum samples from 20 non-pregnant women, 30 women with normal pregnancy and 50 women with pregnancy associated with pre-eclampsia were tested for circulating immune complexes using the polyethyleneglycol precipitation method. A highly significant positive correlation was found between circulating immune complexes and severe pre-eclampsia (BP greater than 140/90 mm Hg, albuminuria greater than 0.25 g/l). In contrast to this the difference in immune complex levels between non-pregnant subject, normal pregnancy cases and patients with mild pre-eclampsia was not statistically significant. A significant positive correlation was found between the level of circulating immune complexes and the severity of albuminuria. These findings suggest that circulating immune complexes, though not seeming to play an aetiological role in pre-eclampsia may very well be involved in its pathogenesis.  相似文献   
996.
Existing triage algorithms consider, for the most part, only the primary casualty with physical trauma. Algorithms fail to appreciate the primary, secondary, or tertiary neuropsychiatric casualty. Research advances on neuropsychiatric casualties must link with the mandates of emergency medical services and disaster management to improve triage sensitivity and specificity. Early recognition and management of neuropsychiatric casualties will diminish the potential for long-term consequences. Expanded triage algorithm supplements are proposed to improve the recognition of those victims at risk.  相似文献   
997.
The authors suggest additional criteria evidencing inflammations in the gallbladder and colloid stability of the bile: bile acid absorption and cholesterol sedimentation coefficients. Derivation of these coefficients is based on biochemical examination of the bile with measurements of bile acid, cholesterol, and bilirubin concentrations in both portions. The results of examinations of 99 subjects evidence the diagnostic value and specificity of the characteristics, and availability of this method for clinical practice.  相似文献   
998.
The dermal absorption of niclosamide, a drug shown to prevent Schistosomiasis by blocking the dermal penetration of cercariae, has been examined in Sinclair minipigs and rats. Radioactivity in the urine and feces collected daily for 7 days after application of 14C-niclosamide accounted for less than 2 per cent and 10 per cent of the labelled compound applied to pig and rat skin, respectively. Approximately 20 per cent of the radioactivity from the dose solution was recovered on the skin excised from the area of application in both minipigs and rats. No radioactivity was detected in organs removed from the pig 7 days after application of radiolabelled drug while less than 6 per cent of the dose could be accounted for in the rat organs/carcass. Radioactivity in swine blood, removed 0.5, 1, 2, 4 and at 24 h intervals after dosing, was at or below three times background in all of the samples. Total recovery of the applied radioactivity was 78 per cent in pigs and 57 per cent in rats. These studies indicate that niclosamide is very poorly absorbed after dermal application. The results are consistent with earlier comparative studies showing that dermal penetration of xenobiotics in rats is generally higher than in swine.  相似文献   
999.
Rats exposed on their first postnatal day to 100% nitrogen for 25 min developed hyperactivity and lower performance in passive avoidance task during development. Administration of MK-801 (0.5 mg/kg i.p.) 1 h before anoxia or (0.25 and 0.5 mg/kg) 1 h after completely reversed this behavioral impairment. Senescent rats (24-26 months) exposed to hypoxia (92% N2 + 8% O2) for 5 h failed in their performance in C.A.R., 30 days later. Pretreatment with MK-801 (1 mg/kg i.p.) completely reversed this impairment. These data suggest that activation of endogenous NMDA receptors produces different behavioral consequences in neonatal and senescent rats and that MK-801 administration close to exposure of animals to anoxia or hypoxia can prevent such damage, thus preventing behavioral impairments in postnatal as well as in senescent rats.  相似文献   
1000.
Transient transfection of pLB2CAT constructs bearing short synthetic oligonucleotides derived either from the tyrosine hydroxylase (TH) promoter or other sources was used to examine functional cAMP regulatory element (CRE) activity in a variety of cell lines. The region containing only the putative TH CRE was found to be as or more effective in conferring cAMP responsiveness onto pLB2CAT (which employs the TK promoter) than the immediate 272 bp region of the TH promoter. Increases in CAT activity of 10- to 20-fold were observed in JEG-3 cells with a single insert of the TH CRE region (-31 to -54) in pLB2CAT, and the presence of a second insert generated only a modest further increase. This construct also responded to cAMP in 4 other cell lines tested but the degree of increase was less dramatic. Inserts containing the consensus 8 bp CRE motif embedded in other natural or artificial contexts served generally as weak functional CREs in all cell lines tested. In vitro analysis revealed that a specific protein-DNA complex apparently containing a single protein with a MW of 45-50 kDa was formed equally well with JEG-3 cell nuclear extract and CRE-bearing-TH and other fragments which produced dramatically different cAMP effects in vivo. These results suggest specificity in the effects of cAMP on different CREs which are dictated by contextual differences.  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