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   38163篇
  免费   2384篇
  国内免费   756篇
耳鼻咽喉   213篇
儿科学   709篇
妇产科学   457篇
基础医学   4054篇
口腔科学   232篇
临床医学   5708篇
内科学   4926篇
皮肤病学   178篇
神经病学   2294篇
特种医学   1361篇
外科学   4331篇
综合类   6300篇
预防医学   3788篇
眼科学   177篇
药学   3810篇
  36篇
中国医学   2159篇
肿瘤学   570篇
  2024年   95篇
  2023年   568篇
  2022年   1101篇
  2021年   1685篇
  2020年   1512篇
  2019年   1143篇
  2018年   1136篇
  2017年   1136篇
  2016年   1171篇
  2015年   1167篇
  2014年   2513篇
  2013年   2718篇
  2012年   2266篇
  2011年   2391篇
  2010年   1891篇
  2009年   1709篇
  2008年   1668篇
  2007年   1634篇
  2006年   1538篇
  2005年   1282篇
  2004年   1072篇
  2003年   982篇
  2002年   823篇
  2001年   755篇
  2000年   729篇
  1999年   594篇
  1998年   495篇
  1997年   502篇
  1996年   423篇
  1995年   420篇
  1994年   377篇
  1993年   347篇
  1992年   303篇
  1991年   264篇
  1990年   256篇
  1989年   211篇
  1988年   237篇
  1987年   221篇
  1986年   170篇
  1985年   198篇
  1984年   230篇
  1983年   144篇
  1982年   174篇
  1981年   158篇
  1980年   139篇
  1979年   114篇
  1978年   111篇
  1977年   93篇
  1976年   71篇
  1973年   86篇
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
21.
目的:观察体外循环(CPB)对10例瓣膜置换术病人全血细胞胰岛素受体和红细胞ATP含量的影响。方法:利用放射配体结合试验,测定全血细胞胰岛素受体密度和亲和力;用高效液相色谱法测定红细胞ATP含量,同时监测血糖和胰岛素浓度。结果:转流30分钟,血细胞高亲和胰岛素受体(R1)密度明显增加(P<0.01),亲和力(K1)明显降低(P<0.01),低亲和胰岛素受体(R2)密度也明显增加(P<0.01),但亲和力(K2)变化不大(P>0.05);停机30分钟,上述变化有所恢复,但未到转流前的水平。转流30分钟红细胞ATP含量明显降低(P<0.01),并持续到停机后30分钟,同时伴随血糖明显升高(P<0.01),胰岛素/血糖比值明显降低(P<0.01)。结论:CPB可致血细胞胰岛素受体密度增加而亲和力下降,以及红细胞ATP含量下降。  相似文献   
22.
Summary Twenty-two persons (20 men and 2 women) were examined for their external and internal exposure to the glycol ether 1-methoxypropan-2-ol (PGME) during the production, leak testing and mounting of brake-hoses. For the measurement of external exposure, personal air monitoring was the method of choice. Average concentrations of PGME of 82.2 mg/m3 (22.3 ppm), 68.6 mg/m3 (18.6 ppm) and 11.3 mg/m3 (3.1 ppm) were found in the air of the brakehose production, leak test and mounting areas, respectively. For the estimation of internal exposure to PGME, this glycol ether was measured in both urine and blood. The biological samples were taken post-shift. The highest internal exposure levels were found in the brakehose production section and in the leak test area. The average post-shift concentrations for PGME in workers in the brakehose production section were 4.6 mg/l in urine and 13.5 mg/l in blood; the corresponding figures for workers in the leak test area were 4.2 mg/l in urine and 11.0 mg/l in blood. In blood and urine samples of workers engaged in the mounting area, PGME levels were below the detection limits. The elimination kinetics of PGME were also studied in three highly exposed persons, and mean excretion half-lives of PGME of approximately 4.4 h were found. On the basis of our results we made a rough calculation of a future biological tolerance value: we would except that concentrations of 38-109 mg per litre of blood and 10–31 mg per litre of urine would correspond to the German MAK value for PGME (375 mg/m3).  相似文献   
23.
Ten-year stability of cardiovascular responses to laboratory stressors   总被引:1,自引:0,他引:1  
In this study we examined test-retest stability of cardiovascular stress responses over a decade of the life span. Participants were 55 male college undergraduates. 19 years of age at initial testing, and 29 years of age at follow-up testing Stressors were a foot cold pressor and an aversive reaction time task. Cardiovascular measures included systolic and diastolic blood pressure, heart rate, and preejection period. For cold pressor, the magnitude and pattern of cardiovascular responses remained unchanged at the 10-year follow-up. For the reaction time task, the characteristic cardiovascular response patterns was preserved but with significant attenuation of magnitude. The present findings are consistent with previous observations of temporal stability but over a substantially longer test-retest interval. The long-term stability of stress responses is discussed in the context of stress test methodology, behavioral response demands, and maturation of the physiological systems involved in cardiovascular response expression.  相似文献   
24.
Magnetization prepared segmented acquisition requires a view order that maximizes signal contrast during the acquisition of the central portion of k-space. Steady state free precession (SSFP) acquisition further requires a view order that minimizes changes in phase-encoding gradients from one repetition to the next in order to minimize eddy current artifacts. In this article, optimal view ordering schemes satisfying these two requirements are formulated and applied to inversion prepared 3D SSFP contrast-enhanced MR angiography (MRA). Experiments on phantoms and pigs demonstrated improved background suppression and reduced image artifacts.  相似文献   
25.
The optimal use of kidneys from small pediatric deceased donors remains undetermined. Using data from the Scientific Registry of Transplant Recipients, 2886 small (< 21 kg) pediatric donors between 1993 and 2002 were identified. Donor factors predictive of kidney recovery and transplantation (1343 en bloc; 1600 single) were identified by logistic regression. Multivariable Cox regression was used to assess the risk of graft loss. The rate of kidney recovery from small pediatric donors was significantly higher with increasing age, weight and height. The odds of transplant of recovered small donor kidneys were significantly higher with increasing age, weight, height and en bloc recovery (adjusted odds ratio = 65.8 vs. single; p < 0.0001), and significantly lower with increasing creatinine. Compared to en bloc, solitary transplants had a 78% higher risk of graft loss (p < 0.0001). En bloc transplants had a similar graft survival to ideal donors (p = 0.45) while solitary transplants had an increased risk of graft loss (p < 0.0001). En bloc recovery of kidneys from small pediatric donors may result in the highest probability of transplantation. Although limited by the retrospective nature of the study, kidneys transplanted en bloc had a similar graft survival to ideal donors but may not maximize the number of successfully transplanted recipients.  相似文献   
26.
Computed duplex sonography was used to examine the renal arteries in 36 hypertensive children and adolescents (ages 4–17 years) with arterial hypertension of either renal or non-renal origin. Time-averaged flow velocities, maximum blood flow velocities as well as absolute renal blood flow and renal blood flow per gram kidney weight were measured. Normal flow velocities and normal to elevated renal blood flow volume was found in patients with acute glomerulonephritis and those with signs of chronic glomerulonephritis onset. Patients having advanced stages of chronic glomerulonephritis, on the other hand, were characterized by lower levels of all parameters. Unilateral renal artery stenosis was diagnosed correctly in four patients, although one intra-renal artery stenosis escaped imaging. Scarred kidneys exhibited low-normal or reduced flow velocities and renal blood flow volumes corresponded roughly to kidney size and preservation of normal kidney structure. Hypertension in some patients with normal kidneys showed a tendency to cause higher renal blood flow without consistent acceleration of blood flow velocities. We conclude that duplex sonography is a suitable primary diagnostic tool in measuring blood flow velocities and absolute renal blood flow volume in hypertensive children, thus facilitating the choice of the next diagnostic step.  相似文献   
27.
In this study we wanted to investigate the post-operative astigmatism and visual acuity after phacoemulsification and conventional extracapsular cataract surgery. Patients operated between April and June 1993 (n=150) were retrospectively analyzed. The patients were examined prior to surgery and at day 1, at day 10, and in week 6 post-operatively. The difference between the post-operative log mean visual acuity in the Phaco group and in the CECCE group was significant after 1 and 10 days, however it was not significant (p=0.191) after 6 weeks. The mean astigmatism was significantly less in the Phaco group than in the CECCE group during the whole post-operative check-up period. This study suggests that Phaco results in a lower post-operative astigmatism and an earlier visual rehabilitation compared to the CECCE technique.Abbreviations Phaco Phacoemulsification - CECCE Conventional extracapsular cataract extraction  相似文献   
28.
Summary The aim of this study was to evaluate the level of physical capacity in a female hospital population of Paris and its suburbs. A total of 1505 women working in the selected departments filled in a questionnaire concerning their working conditions, life habits and health and also attended a medical examination. The effort test performed consisted in flexing the legs 20 times with the chest held straigt, in 40 s. The heart rates were measured for the first, the second and the third minutes of recovery (first 15 s multiplied by 4). The blood pressure was measured just after the heart rate, for the first and the third minute. Recovery indices have been constituted from the results. The respective weights of anthropometric and sociodemographic risk factors for recovery indices were studied in multiple logistic regression models. The classification enables us to consider about 25%–30% of our population as having a satisfactory physical capacity, about 26%–27% as having an acceptable capacit, and about 24%–27% as having a weak capacity. About 21% of the population presented an excessive pressure reaction and 44% a questionable pressure reaction. Our results concerning the level of physical capacity of the female nursing staff should be taken into account especially in the future planning of work loads and architectural choices, which must avoid excessive physical burdens in relation to this level. An improvement in the level of physical capacity could be envisaged as well.  相似文献   
29.
The per- and post-operative characteristics of three different i.v. anaesthetic induction agents were studied double-blindly in 75 patients admitted for outpatient gynaecological dilatation and curettage. All the patients were premedicated with midazolam 0.1 mg/kg i.m. Induction started with alfentanil 0.015 mg/kg i.v. 60 s before either: propofol 2.2 mg/kg i.v., or thiopentone 4.0 mg/kg i.v., or methohexitone 2.0 mg/kg i.v. All the patients received 66% nitrous oxide in oxygen. The propofol patients were significantly better relaxed and had a higher incidence of hypotension during the procedure. The methohexitone patients had higher pulse rates and a higher frequency of hiccups during the procedure. Propofol induction resulted in a faster awakening of the patients and a better recovery function compared with methohexitone for the first 15 min and compared with thiopentone for the first 240 min after the procedure. Postoperative side-effects were less frequent in the thiopentone group, and minor abdominal pain was significantly more frequent in the propofol group. There was no significant difference between the groups for any variable after 240 min postoperatively.  相似文献   
30.
The purpose of this study was to compare the stress-response-dampening (SRD) effect of alcohol in hostile and nonhostile men based on a combined score of four subscales of the Cook-Medley Hostility Scale . Subjects were 72 male social drinkers. Subjects' cardiac interbeat-interval, and systolic and diastolic blood pressure reactivity to a situational stressor were measured following the consumption of either alcohol, no alcohol, or an active placebo beverage. Results demonstrated that hostile men evinced lower heart rate and systolic blood pressure (SBP) reactivity to the stressor when given alcohol, compared with intoxicated nonhostile subjects, and lower reactivity relative to all other groups, with the exception of SBP in the nonhostile controls. These results allow for speculation that hostile men may be more likely than controls to experience possible SRD effects of alcohol and thus, perhaps, be predisposed to increased alcohol consumption when under stress.  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