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   4015篇
  免费   125篇
  国内免费   10篇
耳鼻咽喉   15篇
儿科学   95篇
妇产科学   128篇
基础医学   262篇
口腔科学   84篇
临床医学   820篇
内科学   1059篇
皮肤病学   176篇
神经病学   148篇
特种医学   3篇
外科学   427篇
综合类   27篇
一般理论   34篇
预防医学   345篇
眼科学   65篇
药学   379篇
中国医学   5篇
肿瘤学   78篇
  2017年   25篇
  2016年   51篇
  2015年   59篇
  2014年   59篇
  2013年   141篇
  2012年   39篇
  2010年   114篇
  2009年   128篇
  2008年   35篇
  2007年   39篇
  2006年   58篇
  2005年   29篇
  2003年   24篇
  2001年   53篇
  2000年   42篇
  1999年   128篇
  1998年   163篇
  1997年   236篇
  1996年   249篇
  1995年   178篇
  1994年   130篇
  1993年   135篇
  1992年   117篇
  1991年   124篇
  1990年   111篇
  1989年   121篇
  1988年   104篇
  1987年   80篇
  1986年   91篇
  1985年   74篇
  1984年   83篇
  1983年   72篇
  1982年   79篇
  1981年   91篇
  1980年   77篇
  1979年   76篇
  1978年   63篇
  1977年   47篇
  1976年   52篇
  1975年   32篇
  1974年   35篇
  1971年   32篇
  1968年   23篇
  1966年   22篇
  1959年   25篇
  1958年   31篇
  1957年   33篇
  1956年   35篇
  1955年   23篇
  1954年   24篇
排序方式: 共有4150条查询结果,搜索用时 15 毫秒
1.
2.
AIM: To evaluate the outcome of primary vesicoureteral reflux (VUR) using conservative treatment. METHODS: Eighty-seven children with primary VUR who had been treated with a conservative medical regimen and monitored through a yearly cystogram were recruited for the study. The study was conducted at the Pediatric Nephrology Clinic in Songklanagarind Hospital, the major tertiary care center in southern Thailand. Statistical analyses using Kaplan-Meier survival curves, chi-squared test, Fisher's exact test and multivariate analysis with Cox regression were performed. RESULTS: The study group consisted of 41 boys and 46 girls, with a total of 133 VUR. The age of the boys was significantly lower than that of the girls (P < 0.001). Resolution of the low grades (grades I-III) of VUR was significantly more frequent than that of the high grades (grades IV-V) (68/95, 72%vs 14/38, 37%; P < 0.001). Using the Kaplan-Meier survival analysis and log-rank test, the resolutions of VUR in boys versus girls, and age <1 years versus >or=1 years were not significantly different (P = 0.2252 and 0.4756, respectively). Low-grade VUR and unilateral VUR had significantly higher probabilities of resolution than high-grade VUR and bilateral VUR, respectively (P = 0.0041 and 0.0467, respectively). Multivariate Cox regression analysis indicated that among low-grade VUR, boys and unilateral VUR had significantly higher probabilities of resolution. Among the high-grade VUR, neither sex nor laterality had a significant effect on the probabilities of VUR resolution. CONCLUSION: This study offers more evidence that children with low-grade VUR have a higher chance of reflux resolution if they are boys and have only unilateral VUR. There is still no good guide for resolution of reflux in children with high-grade VUR.  相似文献   
3.
4.
The aim of this research is to characterize the presence of insulin-degrading enzyme in human colon and ileal mucosal cells. Biochemical studies, including the activity-pH profiles, the effects of enzyme inhibitors, immunoprecipitation and western blots, were conducted. The majority of insulin-degrading activity in colon mucosal cells was localized in the cytosol. In both colon and ileum, cytosolic insulin-degrading activities had a pH optimum at pH 7.5, and were extensively inhibited by each of N-ethylmaleimide, p-chloromercuribenzoate, and 1,10-phenanthroline, but were very weakly affected by each of leupeptin, chymostatin, diisopropyl phosphofluoridate and soybean trypsin inhibitor. In the colon and ileum, more than 93% and 96%, respectively, of cytosolic insulin-degrading activities were removed by the mouse monoclonal antibody to human RBC insulin-degrading enzyme, as compared with less than 20% by the normal mouse IgG for both tissues. Further, a western blot analysis revealed that a cytosolic protein of 110 kD, in both human colon and ileum, reacted with the monoclonal antibody to insulin-degrading enzyme. It is concluded that insulin-degrading enzyme is present in the cytosol of human colon and ileal mucosal cells.  相似文献   
5.
A 90-Day Inhalation Toxiaty Study with Benomyl in Rats. WARHEIT,D. B., KELLY, D. P., CARAKOSTAS, M. C., AND SINGER, A. W. (1989).Fundam Appl Toxicol./ 12, 333-345. Benomyl [methyl 1-(butylcarbamoyl)-2-benzimidazolecarbamate,CAS Registry No. 17804-35-2] is a fungicide and the possibilityfor inhalation exposure exists for field workers. To assessthe toxicity of benomyl, groups of 20 male and 20 female CDrats were exposed nose-only 6 hr a day, 5 days a week, to concentrationsof 0, 10, 50 or 200 mg/m3 of a benomyl atmosphere. At the midpoint(approximately 45 days on test) and at the end of the exposureperiod, blood and urine samples for clinical evaluation werecollected from 10 rats/group/sex, and these animals were sacrificedfor pathological examination. Similar evaluations were performadon all remaining rats at the end of the 90-day test period.After approximately 45 days on test, compoundrelated degenerationof the olfactory epithelium was observed in all males and in8 of 10 female rats exposed to 200 mg/m3 benomyl. Two male ratsexposed to 50 mg/m3 had similar, although less severe, areasof olfactory epithelial degeneration. After approximately 90days of exposure, the remaining 10 rats/group/sex were sacrificedand examined. Of these rats, all of the males and females exposedto 200 mg/m3 had olfactory degeneration, along with 3 malesexposed to 50 mg/m3 of benomyl. No other observed lesions wereinterpreted to have been caused by the benomyl exposure. Inaddition, male rats exposed to 200 mg/m3 benomyl had depressedmean body weights compared to controls and this finding correlatedwith a reduction in food consumption. Based on pathologicalobservations, 10 mg/m3 represents the no-observable-effect level(NOEL) for the male rats, and 50 mg/m3 is the NOEL for the femalerats.  相似文献   
6.
A protein from rat testes that catalyzes the oxidation of ethanolin the presence of NAD+, but not NADP+, has been characterizedenzymatically and compared to that of hepatic alcohol dehydrogenaseobtained from the same animals. The testicular enzyme, likethe hepatic enzyme, has a Km value for ethanol in the 0.5–1.0-mMrange and can utilize other alcohols such as n-propanol, n-butanol,and isobutanol, although the Km values for these other alcoholsare considerably lower (0.03–0.08 mM) that that for ethanol.The testicular enzyme is more heat-labile than is the hepaticenzyme. Finally, the testicular enzyme catalyzes the oxidationof retinol and its retinol dehydrogenase activity is inhibitedby ethanol.  相似文献   
7.
Implantable Transvenous Pacing Leads:   总被引:1,自引:0,他引:1  
With the dawn of a new millennium, physicians' demands for very thin transvenous leads able to be positioned in nontraditional sites like the Bachmann's bundle, the high and mid-right ventricular septum, and the His bundle have created new and exciting challenges for lead engineers. Bipolar leads can now be as thin and reliable as unipolar leads. Cathode electrodes are very small, porous, and demonstrate high impedance. To optimize stimulation thresholds, steroid-eluting passive- and active-fixation electrodes have become popular for use in the atrium and ventricle. To create thin lead body diameters, new insulation and conductor materials and lead body designs are necessary. Hybrid medical materials having the best features of silicone rubber and polyurethane will allow for reliable insulation. Conductor cables instead of helical coils permit strong thin diameter leads to be designed. Transvenous lead implantation using the traditional stylet may not be possible with thin diameter leads, necessitating the use of sophisticated workstations using steerable catheters to guide these new active-fixation leads to selective sites in the right heart. The pacing lead of the future may be very different from the one used today. Ironically, it will have features and implantation techniques similar to the transvenous leads designed prior to the use of the stylet. We are now approaching full circle in lead development, retracing the footprints of the early implanters of three and a half decades ago. (PACE 2004; 27[Pt. II]:887–893)  相似文献   
8.
9.
10.
A Comparison of mortality from ischaemic heart disease underthe age of 60 for 1980 to 1981 between the Grampian Health Boardand the North Staffordshire Health Authority has been made.A total of 993 deaths was notified by death certificate fromthe two areas of similar population of which 434 were from Grampianand 559 from North Staffordshire. After examination of generalpractitioner and hospital case notes, autopsy reports and deathcertificates, nearly all (532) of the North Staffordshire deathswere accepted as being due to ischaemic heart disease but onlythree-fifths (263) of the Grampian deaths could be begin besubstantiated as there was inadequate information for the remainder.Deaths from ischaemic heart disease seem apparently to be twofoldgreater in North Staffordshire than Grampian but much of thisdiscrepancy could be attributed to a widely different autopsyrate and to unavailability of case notes. Experience of thissurvey suggests that the results of other epidemiological investigationsmay be equally or even more unreliable.  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