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   9604篇
  免费   1120篇
  国内免费   114篇
耳鼻咽喉   79篇
儿科学   233篇
妇产科学   164篇
基础医学   919篇
口腔科学   744篇
临床医学   767篇
内科学   2019篇
皮肤病学   64篇
神经病学   473篇
特种医学   76篇
外科学   420篇
综合类   507篇
预防医学   1905篇
眼科学   55篇
药学   1380篇
中国医学   48篇
肿瘤学   985篇
  2023年   88篇
  2022年   105篇
  2021年   275篇
  2020年   277篇
  2019年   325篇
  2018年   331篇
  2017年   365篇
  2016年   344篇
  2015年   350篇
  2014年   539篇
  2013年   974篇
  2012年   430篇
  2011年   483篇
  2010年   422篇
  2009年   467篇
  2008年   522篇
  2007年   436篇
  2006年   418篇
  2005年   374篇
  2004年   322篇
  2003年   292篇
  2002年   289篇
  2001年   260篇
  2000年   216篇
  1999年   178篇
  1998年   150篇
  1997年   173篇
  1996年   151篇
  1995年   143篇
  1994年   108篇
  1993年   99篇
  1992年   98篇
  1991年   88篇
  1990年   85篇
  1989年   69篇
  1988年   59篇
  1987年   69篇
  1986年   42篇
  1985年   52篇
  1984年   64篇
  1983年   35篇
  1982年   43篇
  1981年   35篇
  1980年   30篇
  1979年   36篇
  1978年   24篇
  1977年   20篇
  1976年   22篇
  1975年   15篇
  1973年   18篇
排序方式: 共有10000条查询结果,搜索用时 343 毫秒
81.
Background Occupational allergic respiratory symptoms in coffee workers have been frequently reported, but the ultimate cause of sensilization is still debated, castor bean being considered besides green coffee beans. Atopy and cigarette smoking have been suggested as promoting factors of sensitizalion for several occupational allergens. Objective This study was carried out to assess the prevalence of allergic respiratory symptoms and of sensitization to both green coffee beans and castor bean in the whole workforce of a coffee manufacturing plant. Furthermore we wanted to ascertain both the presence of castor bean antigens in the settled dust of the green coffee beans warehouse and the possible crossreactivity between the two beans. Meanwhile, the effect of smoking and atopy was considered. Method: Two-hundred and eleven workers were examined. A questionnaire on oculorhinitis and asthma was administered and skin-prick tests for green coffee beans, castor bean and 15 common inhalant allergens were carried out. Isoelectric focusing, isoelectric focusing immunoblot and radioallergosorbent assay (RAST) inhibition were performed on samples of settled environmental dust from the green coffee area, as well as on castor bean and green coffee beans. Results Ten per cent of the workers complained of oculorhinitis alone and 16% of asthma (nearly always associated with oculorhinitis). The overall prevalence of skin-sensitization was: 15% for green coffee beans, 22% for castor bean, 22% for common allergens. Evidence of sensitization to occupational allergens was more common in smokers, with a more than twofold increase in relative risk. The strong association between skin positivity to common and occupational allergens suggests that atopy acts as an enhancing host factor towards occupational sensitization. The analysis of the dust confirmed the presence of castor bean antigens. Conclusion Our findings indicate that castor bean is the major cause of occupational sensitization among coffee workers, whereas smoking and atopy act as enhancing factors.  相似文献   
82.
This paper reports the results of a postal questionnaire completed by 2343 smokers who had contacted a television company for help with stopping smoking. Of these, 1848 (78.9%) completed a follow-up questionnaire 1 year later. This indicated that 797 had tried to stop, 709 had tried to cut down, and 164 had become abstinent. Analyses show that the intention to try to stop smoking was dependent not only on the perceived health benefit, but also on the subjects' confidence that they would succeed if they tried to stop. As predicted by Weiner's [(1979). J. Educ. Psychol.71: 3–25] model of achievement motivation, those who attributed other smokers' failures at quitting to stable factors had lower expectancies of success, as had those who saw themselves as more addicted. When the follow-up data are considered, reported attempts at quitting were strongly related to previously declared intentions, and reported abstinence was related to previous confidence (expectancy of success) and perceived addiction. There is no support for hypotheses concerning self-other differences in attribution, or defensive attribution, in subjects' attributions for their own failures at cessation. Implications for antismoking interventions are discussed.This research was facilitated to various extents by grants from the British Council, the Department of Health and Social Security, the Medical Research Council, and the Social Science Research Council, London. When the data were collected, all authors were at the Addiction Research Unit, Institute of Psychiatry, University of London.  相似文献   
83.
Attitudes toward smoking cessation among men and women   总被引:3,自引:0,他引:3  
Recent reports indicate that women are less successful than men in their attempts to quit smoking. Sex differences in attitudes toward smoking cessation were examined cross-sectionally in a sample of 447 smokers randomly selected from employees of 10 diverse Minnesota worksites and interviewed in early 1984. No sex differences were found in the percentage of smokers who had tried to quit at least once in the past; indeed, over four of five respondents reported prior attempts to quit. Yet compared to women, men were more interested in quitting. Women were less likely than men to perceive the health benefits of quitting and expressed more concern about weight gain and job pressures related to quitting. No significant sex differences were found in prior use of formal cessation services, which had been used by about one-fourth of these respondents. Yet compared to men, women appeared to rely on informal sources of support, such as encouragement from co-workers. These findings underline the importance of intervention programs targeting women and suggest strategies that might enhance the effectiveness of such programs oriented toward women.  相似文献   
84.
Summary Chronic serum sickness glomerulonephritis was induced in 20 Wistar rats, using radio-labelled, chemically cationised bovine serum albumin (BSA) as antigen. Four days after the last injection of antigen, when relocation of antigen within the rat had effectively ceased, the rats were given a single large intraperitoneal dose of either non-immune rat gamma globulin or anti-BSA rat gamma globulin. Ten days later the rats were killed. The rats which had received the anti-BSA globulin had significantly more antigen in renal cortex and in isolated glomeruli than the control group. They also had larger mesangial deposits as assessed by morphometry at electron microscope level; assessment of subepithelial deposits provided equivocal results. These findings provide direct confirmation that circulating antibody which is directed against an antigen which is trapped within deposits in the glomerulus will inhibit the removal of the antigen and deposits from the mesangium.  相似文献   
85.
Research has demonstrated that smoking during pregnancy has deleterious effects on the health of the unborn child as well as the mother. The present study examined whether pregnant smokers would have a greater intention to quit smoking, whether the stage of pregnancy would influence the intention to quit, and whether variables which have predicted cessation among pregnant smokers would also predict intention to quit. The results indicated that pregnant women did not have a significantly greater intention to quit smoking compared to nonpregnant smokers, despite the health risks to their child. Women who were further along in their pregnancy and women who smoked more cigarettes on a daily basis demonstrated the least intention to quit. Notably, women in the first trimester showed the greatest intention to quit, suggesting that pregnant women may be most receptive to quitting during their first trimester.  相似文献   
86.
Atherosclerosis (AR) is the leading cause of morbidity and mortality in the US and cigarette smoking is a major contributing factor to the disease. Like cigarette smoking in lung cancer, genetic susceptibility may be an important factor in determining who is more likely to develop AR. However, the current emphasis has been on susceptibility based on altered cardiovascular homeostasis. In this investigation, we studied 120 AR patients and 90 matched controls to elucidate the association between polymorphisms in some metabolizing genes (GSTM1, GSTT1, CYP2E1, mEH, PON1, and MPO) and susceptibility to AR. We found that the GSTT1 null allele and the fast allele of mEH(*) (exon 4) are associated with risk for AR. Furthermore, the combined genotypes GSTM1 null/ CYP2E1(*)5B, GSTM1 null/mEH YY, and GSTT1 null/mEH YY are significantly associated with susceptibility to AR (OR = 15.42, 95% CI = 1.33-77.93, P = 0.021; OR = 3.48, 95% CI = 1.63-8.04, P = 0.0008; OR = 3.4; 95% CI = 0.99-17.38, P = 0.05; respectively). We have also conducted cytogenetic analysis to elucidate if induction of chromosome aberrations (CAs) is a biomarker of AR susceptibility. We found that among cigarette smokers (AR patients and smoker controls), individuals having the GSTM1 null allele had a significantly higher frequency of CAs compared to those with the normal allele (P < 0.05). This association was not found among nonsmokers. In addition, individuals who had inherited the CYP2E1(*)5B allele exhibited a significantly higher CA frequency (8.0 +/- 0.82) compared to those with the CYP2E1 wild-type genotype (4.31 +/- 0.35). Since the analysis of genetic susceptibility factors is still in its infancy, our study may stimulate additional investigations to understand the roles of genetic susceptibility and cigarette smoking in AR.  相似文献   
87.
The quasistatic passive venous elastic properties were studied in-vitro on 6 cylindrical segments of abdominal vena cava from Wistar rats. Using noncontact methods of deformation measurement, diameters and axial force of the segments were analyzed as a function of simultaneous axial stretch and internal pressure in the physiological range of 0–2.7 kPa. The elasticity of the wall tissue was investigated in terms of moduli of elasticity in the circumferential, axial and radial direction. Results show that the pressure-diameter relationship is highly nonlinear, indicating that veins are extremely compliant at lowest pressures and rather stiff beginning from some 0.7 kPa of pressure. The axial force decreases with pressure at small prestretches, increases at large, but remains constant for the in-vivo prestretch. The venous wall tissue is markedly anisotropic in the entire physiological range of deformations.  相似文献   
88.
The purpose of this study was to use a model of aging to examine the relationships between passive properties of the calf muscles and plantarflexion concentric isokinetic torque characteristics. Eighty-one active women 20–84 years of age were tested using a Kin-Com isokinetic dynamometer interfaced with electromyography (EMG). The passive properties were tested by stretching the muscles from relaxed plantarflexion to a maximal dorsiflexion (DF) angle at a rate of 5°·s–1 (0.087 rad·s–1) with minimal raw EMG activity (<0.05 mV). The maximal concentric torque was tested from maximal passive DF into plantarflexion at four randomly ordered velocities of 30, 60, 120, and 180°·s–1. Pearson correlation coefficients (Bonferroni adjusted) indicated a hierarchical order of high to moderate positive correlations between four passive properties and the peak and mean concentric torque for all test velocities. Correlation coefficients for the four passive properties ranged from 0.50 to 0.78 (P<0.001), and the coefficients of determination (r 2) from higher to lower were: (1) maximal DF passive resistive torque (r 2: 0.50–0.62), (2) length extensibility (r 2: 0.40–0.49), (3) maximal muscle length (r 2: 0.28–0.41), and (4) passive elastic stiffness in the last half of the full-stretch range of motion (r 2: 0.25–0.31). The maximal DF passive resistive torque and the length extensibility accounted for 50–62% and 40–49% of the variability in the concentric torque, respectively. The results indicate that the concentrically stronger calf muscles of active women were positively correlated with passively stronger, longer, and stiffer calf muscles, which are characteristics of the calf muscles of younger women. Further studies are needed to examine whether therapeutic interventions, such as stretching and strengthening, can promote adaptations in the calf muscles of older women to attain these more youthful characteristics. Electronic Publication  相似文献   
89.
We investigated the association between human leucocyte antigen (HLA) antigens and lymph node metastasis in 724 gastric cancer patients. Among patients who had poorly differentiated adenocarcinoma with or without HLA-DR4 antigen, lymph node metastasis was detected in 80.8 and 54.9%, respectively (relative risk (RR)=3.5, P = 0.0005, corrected P = 0.0285). It was more common in patients with a family history of cancer death (RR = 7.7). Among signet ring cell carcinoma patients with or without HLA-1152 antigen, lymph node metastasis was detected in 57.7 and 19.7%, respectively (RR =5.6, P=0.0001, corrected P=0.0086). It was more common in patients who were smokers (RR = 8.3). Our findings suggest that HLA-DR4 and HLA-1152 antigens are associated with lymph node metastasis in gastric cancer.  相似文献   
90.
The effects of variations in stroke volume on the intensity of cardiac stimuli was examined in a series of three experiments that empolyed classical psychophsical methods to assess heartbeat detection. Stroke volume was manipulated by passive body tilt and recorded using impedance cardiography while subjects performed heartbeat detection tasks. The postural manipulation generated little or no change in contractility or momentum but did produce substantial changes in stroke volume. However, this potential source of variation in cardiac stimulus magnitude did not influence either the precision of heartbeat detection or the temporal location of heartbeat sensations. It is concluded that the intensity dimension of the heartbeat stimulus is not determined by stroke volume.  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