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   2153篇
  免费   196篇
  国内免费   28篇
耳鼻咽喉   80篇
儿科学   202篇
妇产科学   35篇
基础医学   279篇
口腔科学   92篇
临床医学   196篇
内科学   337篇
皮肤病学   53篇
神经病学   62篇
特种医学   177篇
外科学   294篇
综合类   39篇
预防医学   116篇
眼科学   45篇
药学   64篇
中国医学   2篇
肿瘤学   304篇
  2023年   14篇
  2022年   10篇
  2021年   15篇
  2020年   15篇
  2019年   11篇
  2018年   50篇
  2017年   53篇
  2016年   48篇
  2015年   68篇
  2014年   91篇
  2013年   127篇
  2012年   71篇
  2011年   61篇
  2010年   90篇
  2009年   104篇
  2008年   55篇
  2007年   74篇
  2006年   87篇
  2005年   57篇
  2004年   60篇
  2003年   46篇
  2002年   48篇
  2001年   35篇
  2000年   42篇
  1999年   49篇
  1998年   115篇
  1997年   94篇
  1996年   110篇
  1995年   69篇
  1994年   83篇
  1993年   47篇
  1992年   26篇
  1991年   32篇
  1990年   32篇
  1989年   44篇
  1988年   46篇
  1987年   43篇
  1986年   34篇
  1985年   34篇
  1984年   20篇
  1983年   15篇
  1982年   25篇
  1981年   17篇
  1980年   18篇
  1979年   12篇
  1977年   14篇
  1976年   15篇
  1975年   13篇
  1974年   9篇
  1973年   11篇
排序方式: 共有2377条查询结果,搜索用时 15 毫秒
21.
Prenatal cytogenetic analysis of 71 fetuses conceived by intracytoplasmic sperm injection (ICSI) resulted in the detection of nine (12.7%) chromosome aberrations including two cases of 47,XXY, four cases involving a 45,X cell line and three autosomal trisomies. Molecular analysis of the parental origin of the deleted or supernumerary chromosome was performed by using polymorphic microsatellite markers. Six cases involving a sex chromosome abnormality were found to be of paternal origin while the two trisomic cases that could be analysed were of maternal origin. Two cases involved the same infertile couple who had two consecutive ICSI pregnancies terminated because of a chromosome abnormality. The replaced embryos in both cases originated from a single batch of ICSI fertilized oocytes of which part was used to initiate the first pregnancy and part was cryopreserved and used to initiate the second pregnancy.   相似文献   
22.
23.
European Journal of Clinical Microbiology &; Infectious Diseases -  相似文献   
24.
The aims of this work were to measure the accuracy of one continuous speech recognition product and dependence on the speaker's gender and status as a native or nonnative English speaker, and evaluate the product's potential for routine use in transcribing radiology reports. IBM MedSpeak/Radiology software, version 1.1 was evaluated by 6 speakers. Two were nonnative English speakers, and 3 were men. Each speaker dictated a set of 12 reports. The reports included neurologic and body imaging examinations performed with 6 different modalities. The dictated and original report texts were compared, and error rates for overall, significant, and subtle significant errors were computed. Error rate dependence on modality, native English speaker status, and gender were evaluated by performing ttests. The overall error rate was 10.3 +/- 3.3%. No difference in accuracy between men and women was found; however, significant differences were seen for overall and significant errors when comparing native and nonnative English speakers (P = .009 and P = .008, respectively). The speech recognition software is approximately 90% accurate, and while practical implementation issues (rather than accuracy) currently limit routine use of this product throughout a radiology practice, application in niche areas such as the emergency room currently is being pursued. This methodology provides a convenient way to compare the initial accuracy of different speech recognition products, and changes in accuracy over time, in a detailed and sensitive manner.  相似文献   
25.
The wave I-wave V delay in the auditory brain-stem response is commonly used as a diagnostic tool in otoneurology. Normative values have been established for different populations and different types of stimuli. This I-V delay has been known for some time as "central conduction time" or "central transmission time." This implies that the measure reflects in normal and in pathologic cases delays due to nerve conduction, synaptic transmission, and neural integration and is not caused by cochlear processes. By virtue of the traveling wave delay in the cochlea, amounting to some 4 ms from the base to the "500-Hz place," it is conceivable that this delay contributes to the I-V delay. From a series of 69 pontine angle tumors in which the auditory brain-stem response was recorded, we selected cases with an apparent peripheral origin of a prolonged I-V delay by comparing the whole-click response to responses derived from high-pass noise masking. It seems that cases with an increased I-V delay in the whole-click response but (almost) normal I-V delays in the narrow-band response are indicative of small intracanalicular acoustic neuroma.  相似文献   
26.
The preterm infant fed parenterally is prone to some demineralisation due in part to insufficient Calcium (Ca) and Phosphorus (P) retention. In an attempt to augment Ca and P retention, we prepared a standardised parenteral solution containing calcium gluconate and glucose-1-phosphate (Phocytan) as source of phosphorus, yielding a daily supply of 75 mg/kg Ca and 45 mg/kg P. 28 very low birthweight infants were randomly assigned to receive either this solution (high Ca P ; n = 15) or a conventional formulation containing calcium gluconate and potassium mono- and dibasic phosphate delivering 42 mg/kg Ca and 36 mg/kg P daily (low Ca P ; n = 13). In the high Ca P daily retention was respectively 80% and 99% for Ca and P whereas in the low Ca P group, retention was 70% and 82%. Serum parathormone levels were significantly lower in the high Ca P group. We conclude that parenteral nutrition with a new high Ca P supplement results in an augmented Ca and P retention in very low birthweight infants. This may help to prevent neonatal bone demineralization.  相似文献   
27.
The Dynamic Spatial Reconstructor (DSR) is a device constructed at the Biodynamics Research Unit of the Mayo Clinic for (among other things) the visualization of the beating heart inside the intact thorax. The device consists of 28 rotating X-ray sources arranged on a circular arc at 6° intervals (total span 162°) and a matching set of 28 imaging systems. The whole thorax of the patient is projected onto the two-dimensional screen of the imaging systems by cone beams of X rays from the sources. All of the X-ray sources are switched on and off within a total period of 10 milliseconds. The Medical Image Processing Group at the State University of New York at Buffalo has developed a software package for the design and evaluation of algorithms to be used by the DSR. In this paper we illustrate the operation of the package and a particular algorithm for the reconstruction of the dynamically changing structure of the heart from data collected by the DSR.  相似文献   
28.
-Adrenoceptor stimulation may induce malignant hyperthermia(MH) in vivo. Consequently, we have investigated the effectsof the -adrenoceptor agonist phenylephrine and, for comparison,the effects of the ß-adrenoceptor agonist isoproterenolon inositol-lipid metabolism of malignant hyperthermia susceptible(MHS) and healthy control (MHN) swine. The experiments wereperformed on electrically stimulated (frequency 0.2 Hz) trabeculaeisolated from the right ventricles of the hearts of MHS andMHN animals. After labelling with [3H] inositol for 6 h, differentinositol phosphates were measured by high pressure liquid chromatography,including inositol 1 - phosphate, inositol 1,4-bisphosphate,inositol 1,3,4-trisphosphate, inositol 1,4,5-trisphosphate (1,4,5-IP3)and inositol 1,3,4,5 - tetrakisphosphate. After stimulationwith isoproterenol, the inositol phosphate content did not increaseor vary between muscle from MHS and MHN animals. In contrast,all inositol phosphates increased after stimulation with phenylephrinein both muscle types, the effects being greater in MHS thanin MHN, especially as regards 1,4,5-IP3 content. As 1,4,5-IP3,a presumed second messenger, has been shown to mobilize intracellularcalcium, it is concluded that an enhanced -adrenergic responseis involved in the development of MH. *Address for correspondence: Abteilung für Anästhesiologie,Universitäts-Krankenhaus Eppendorf, Martinistrasse52, D-2000Hamburg 20, Germany. Presented in part at the 1989 Meeting of the European Academyof Anaesthesiology in Bonn.  相似文献   
29.
OBJECTIVE: To evaluate the impact of zinc supplementation on the clinical course, stool weight, duration of diarrhoea, changes in serum zinc, and body weight gain of children with acute diarrhoea. DESIGN: Randomised double blind controlled trial. Children were assigned to receive zinc (20 mg elemental zinc per day) containing multivitamins or control group (zinc-free multivitamins) daily in three divided doses for two weeks. SETTING: A diarrhoeal disease hospital in Dhaka, Bangladesh. PATIENTS: 111 children, 3 to 24 months old, below 76% median weight for age of the National Center for Health Statistics standard with acute diarrhoea. Children with severe infection and/or oedema were excluded. MAIN OUTCOME MEASURES: Total diarrhoeal stool output, duration of diarrhoea, rate of weight gain, and changes in serum zinc levels after supplementation. RESULTS: Stool output was 28% less and duration 14% shorter in the zinc supplemented group than placebo (p = 0.06). There were reductions in median total diarrhoeal stool output among zinc supplemented subjects who were shorter (less than 95% height for age), 239 v 326 g/kg (p < 0.04), and who had a lower initial serum zinc (< 14 mmol/l), 279 v 329 g/kg (p < 0.05); a shortening of mean time to recovery occurred (4.7 v 6.2 days, p < 0.04) in those with lower serum zinc. There was an increase in mean serum zinc in the zinc supplemented group (+2.4 v -0.3 mumol/l, p < 0.001) during two weeks of supplementation, and better mean weight gain (120 v 30 g, p < 0.03) at the time of discharge from hospital. CONCLUSIONS: Zinc supplementation is a simple, acceptable, and affordable strategy which should be considered in the management of acute diarrhoea and in prevention of growth faltering in children specially those who are malnourished.  相似文献   
30.
This study was designed to compare the growth of Pakistani schoolchildren in the UK with the 1990 UK growth standards. Measurements of height, weight, and sitting height were performed on 785 Pakistani schoolchildren aged 5-14 years with the mean values for each age and sex being plotted on the UK growth standards. The results were expressed as SD scores relative to the 1990 reference data. The mean height for the boys was only 0.2 SD scores below the mean for the new growth standards with the mean height for the girls being 0.4 SD scores below the mean. The mean values for weight and body mass index were 0.3 and 0.5 SD scores less than the mean for boys and girls respectively. This study demonstrates that the growth of Pakistani schoolchildren in the UK is comparable to the 1990 UK growth standards with only minor differences. It is not safe to assume that short stature or low body weight in a Pakistani child is due to his or her ethnic background.  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