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   4711篇
  免费   438篇
  国内免费   85篇
耳鼻咽喉   16篇
儿科学   221篇
妇产科学   77篇
基础医学   612篇
口腔科学   121篇
临床医学   622篇
内科学   928篇
皮肤病学   71篇
神经病学   306篇
特种医学   404篇
外国民族医学   1篇
外科学   508篇
综合类   126篇
一般理论   5篇
预防医学   499篇
眼科学   55篇
药学   274篇
中国医学   8篇
肿瘤学   380篇
  2021年   50篇
  2019年   52篇
  2018年   54篇
  2017年   50篇
  2016年   51篇
  2015年   69篇
  2014年   84篇
  2013年   164篇
  2012年   162篇
  2011年   184篇
  2010年   118篇
  2009年   126篇
  2008年   199篇
  2007年   190篇
  2006年   152篇
  2005年   143篇
  2004年   177篇
  2003年   159篇
  2002年   167篇
  2001年   173篇
  2000年   140篇
  1999年   136篇
  1998年   123篇
  1997年   120篇
  1996年   100篇
  1995年   91篇
  1994年   78篇
  1993年   80篇
  1992年   123篇
  1991年   93篇
  1990年   100篇
  1989年   112篇
  1988年   96篇
  1987年   100篇
  1986年   88篇
  1985年   103篇
  1984年   71篇
  1983年   56篇
  1982年   43篇
  1980年   43篇
  1979年   71篇
  1978年   40篇
  1977年   39篇
  1975年   40篇
  1974年   43篇
  1973年   47篇
  1972年   50篇
  1971年   45篇
  1969年   46篇
  1968年   39篇
排序方式: 共有5234条查询结果,搜索用时 15 毫秒
81.
The ensheathment of the olfactory nerve fibres is achieved by cooperation of two cell types. The olfactory ensheathing cells have a rounded outer surface enclosed in a continuous single basal lamina, and enclose an inner compartment from which overlapping processes of the same and adjacent cells enwrap interweaving territories of tightly apposed aligned axons. The olfactory nerve fibroblasts are highly flattened, dense cells generating multiple layers of very thin processes encircling individual or groups of olfactory ensheathing cells. This paper illustrates the unique ultrastructural features of this ensheathment.  相似文献   
82.
Although infants have been noted to have greater relative right or left frontal EEG as early as the neonatal period, other ways in which these newborns differ have not been reported. In this study, 48 newborns were divided on the basis of greater relative right versus greater relative left frontal EEG to determine whether these groups differed in other ways at the neonatal period including behavior, physiology, and biochemistry. We also were interested in whether these EEG patterns were related to any prenatal maternal variables including mood states (depression, anxiety, anger) and biochemistry as well as fetal activity. The greater relative right frontal EEG newborns had mothers with lower prenatal and postnatal serotonin and higher postnatal cortisol levels. The mothers of the greater relative right frontal EEG newborns also had greater relative right frontal EEG activation and lower vagal tone. The greater relative right frontal EEG newborns themselves had elevated cortisol levels, showed a greater number of state changes during sleep/wake behavior observations, and performed less optimally on the Brazelton Neonatal Behavior Assessment (T. B. Brazelton, 1973) including the habituation, motor, range of state, excitability, and depressive symptoms scales. These data suggest that greater relative right frontal EEG newborns may be at greater risk for developmental problems than those with greater relative left frontal EEG activation. In addition, a discriminant function analysis correctly classified 67% of the newborns' EEGs by prenatal maternal variables, suggesting that these might be used to target pregnant women for prenatal intervention.  相似文献   
83.
The prevalence of complement-fixing (CF) antibody against the AG-4 early antigen of herpes simplex virus (HSV) type 2 (HSV-2) was determined in patients with culture confirmed HSV-2 genital herpes and control groups using a commercial HSV-2 early antigen (Simplex-2; Gene Link Australia Ltd). Eighty seven per cent of 39 sera collected between 14 and 28 days after confirmed primary and recurrent HSV-2 infection were positive. In acute sera collected between 2-10 days after onset the Simplex-2 test was negative in all 90 patients with presumed primary infection but positive in 53% of 230 sera from recurrent infection. A specificity of 90-94.5% was obtained by testing 36 patients with recent proven HSV-1 infection and 331 control group patients. The Simplex-2 test may be useful in some cases of culture-negative, clinically suspected genital HSV-2 lesions only when sera are collected between 14-28 days after primary and recurrent infection. Its lack of specificity makes it unsuitable for the routine diagnosis of recent HSV-2 infection in the general population.  相似文献   
84.
Alterations in - and -adrenergic responsiveness were investigated prior to and during the development of hypertension in rats treated with desoxycorticosterone acetate and NaCl (DOCA/ NaCl). The DOCA/NaCl rats became noticeably hypertensive (> 150 mm Hg) six weeks after the initiation of treatment. Prior to the development of hypertension, a reduced in vivo and in vitro - and an enhanced -adrenergic responsiveness of the DOCA/NaCl group resulted. At 2 and 12 weeks of the study, the dipsogenic response to isoproterenol was significantly attenuated in the DOCA/NaCl rats, whereas no difference in the dipsogenic response to 24 hour water deprivation was observed between control and DOCA/NaCl rats. Isoproterenol-induced relaxation of aortic smooth muscle from the DOCA/NaCl treated rats was significantly reduced at 4 weeks and further attenuated at 12 weeks of the study. However, aortic smooth muscle sensitivity to norepinephrine stimulation was significantly increased at 4 and 12 weeks of the study. These results suggest that alterations in both in vivo and in vitro - and -adrenergic responsiveness occur prior to establishment of hypertension of the DOCA/NaCl rats and that these alterations may have a role in the early stages of the development of this form of hypertension.  相似文献   
85.
An 11.8-year median follow-up evaluation of 42 "ideal" patients who had chemonucleolysis was obtained by examination, questionnaire, and roentgenograms. The excellent and good rating of this group was 81%, as compared to the total of 135 patients previously evaluated at 42 months and showing 85.2%. No complications were noted. Disc space rewidening, after initial narrowing, was observed in eight patients and 26% of all discs injected. While all who showed rewidening had excellent results, widening was not necessary to achieve an excellent rating. Marked narrowing and sclerosis of intervertebral margins were seen in many excellent and good clinical results. Chemonucleolysis represents a viable option as definitive treatment for a herniated nucleus pulposus in carefully selected patients.  相似文献   
86.
87.
PurposeRenal function outcomes following robot-assisted radical cystectomy (RARC) have not been well established. We sought to compare long-term renal function outcomes between open radical cystectomy, RARC with extracorporeal urinary diversion and intracorporeal urinary diversion at a high volume institution.Materials and MethodsWe retrospectively reviewed our institutional bladder cancer database for patients who underwent RC from 2010 to 2019 with pre-operative estimated glomerular filtration rate (eGFR) > 45 ml/min/1.73m2. Changes in renal function were assessed through locally weighted scatter plot smoothing and comparison of median eGFR between surgical groups. Chronic Kidney Disease Stage 3B was defined as eGFR < 45 ml/min/1.73m2. Renal function decline was defined as a ≥10 ml/min/1.73m2 drop in eGFR. Kaplan Meier method with log-rank was used to compare CKD 3B-free survival and renal function decline. Cox Proportional Hazards model was used to identify predictors of CKD 3B.ResultsSix hundred and forty four patients were included with median follow-up of 32 months (IQR 12–56). Preoperative characteristics were similar among the groups with no differences in median pre-operative eGFR (ORC: 74.6, extracorporeal urinary diversion: 74.3, intracorporeal urinary diversion: 71.6 ml/min/1.73m2, P = 0.15). Median postoperative eGFR on follow up was not different between groups (P = 0.56). 33% of patients developed CKD 3B. There were no differences in CKD 3B-free survival by surgical approach (P = 0.23) or urinary diversion (P = 0.09). 64% of patients experienced renal function decline with a median time of 2.4 years (P 0.23). Predictors of CKD were pathologic T3 disease or greater (HR: 1.77, P = 0.01), ureteroenteric anastomotic stricture (HR: 2.80, P < 0.001), preoperative CKD Stage 2 (HR: 1.81, P =0.02), and preoperative CKD Stage 3A (HR: 5.56, P < 0.001).ConclusionRenal function decline is common after RC. Tumor stage, pre-operative eGFR, and ureteral stricture development, not surgical approach, influence renal function decline.  相似文献   
88.
89.
To account for the increased proportion of paternal nondisjunction in 47,XXY males as compared to other trisomies, it has been suggested that the XY bivalent, with its reduced region of homology, is particularly susceptible to nondisjunction. Molecular studies of liveborn Klinefelter syndrome (47,XXY) individuals have reported an association between the absence of recombination in the pseudoautosomal region and nondisjunction of the XY bivalent. In this study we examined single sperm from a normal 46,XY male to determine if there is any alteration in the recombination frequency of aneuploid disomic 24,XY sperm compared to unisomic sperm (23,X or Y). Two DNA markers STS/STS pseudogene and DXYS15 were typed in sperm from a heterozygous man to determine if recombination had occurred in the pseudoautosomal region. Individual unisomic sperm (23,X or Y) were isolated using a FACStar(Plus) flow cytometer into PCR tubes. To identify disomic 24,XY sperm, 3-colour FISH analysis was performed with probes for chromosomes X,Y and 1. The 24,XY cells were identified using fluorescence microscopy, each disomic sperm was scraped off the slide using a glass needle attached to a micromanipulator and then put into a PCR tube. Hemi-nested PCR analysis of the two markers was performed to determine the frequency of recombination. A total of 329 unisomic sperm and 150 disomic sperm have been typed. The frequency of recombination between the two DNA markers was 38.3% for the unisomic sperm, similar to frequencies previously reported. The 24,XY disomic sperm had an estimated recombination frequency of 25.3%, however, a highly significant decrease compared to the unisomic 23,X or 23,Y sperm (chi(2) = 10.7, P = 0.001). This direct analysis of human sperm indicates that lack of recombination in the pseudoautosomal region is a significant cause of XY nondisjunction and thus Klinefelter syndrome. Copyright Wiley-Liss. Inc.  相似文献   
90.
A patient with severe hyperemesis gravidarum persisting throughout pregnancy is described. She had marked abnormalities of liver function and failed to respond to conservative management. Total parenteral nutrition was used to maintain her nutritional status as well as that of the foetus. Her vomiting continued and was complicated by severe oesophagitis. On delivery her symptoms settled, but she later developed an oesophageal stricture. Changes in liver function tests are described.  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