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   11116篇
  免费   876篇
  国内免费   25篇
耳鼻咽喉   66篇
儿科学   334篇
妇产科学   235篇
基础医学   1418篇
口腔科学   549篇
临床医学   1079篇
内科学   1792篇
皮肤病学   167篇
神经病学   797篇
特种医学   352篇
外国民族医学   2篇
外科学   1109篇
综合类   68篇
一般理论   3篇
预防医学   2610篇
眼科学   92篇
药学   700篇
中国医学   23篇
肿瘤学   621篇
  2023年   77篇
  2022年   121篇
  2021年   143篇
  2020年   182篇
  2019年   166篇
  2018年   241篇
  2017年   226篇
  2016年   224篇
  2015年   204篇
  2014年   281篇
  2013年   477篇
  2012年   431篇
  2011年   446篇
  2010年   329篇
  2009年   350篇
  2008年   437篇
  2007年   391篇
  2006年   430篇
  2005年   409篇
  2004年   355篇
  2003年   287篇
  2002年   367篇
  2001年   335篇
  2000年   327篇
  1999年   388篇
  1998年   240篇
  1997年   282篇
  1996年   266篇
  1995年   208篇
  1994年   116篇
  1993年   186篇
  1992年   201篇
  1991年   213篇
  1990年   203篇
  1989年   206篇
  1988年   209篇
  1987年   208篇
  1986年   211篇
  1985年   196篇
  1984年   116篇
  1983年   133篇
  1982年   91篇
  1981年   90篇
  1980年   71篇
  1979年   115篇
  1978年   98篇
  1977年   90篇
  1976年   73篇
  1975年   67篇
  1974年   64篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
By means of a questionnaire sent to all medical units in Malm?, including primary care, homes for the elderly, and industrial health clinics, 275 patients with leg and foot ulcers were identified. With a population of 232,908 in Malm?, this corresponds to a prevalence of 0.12%, which is lower than reported by others. Since the response rate was high (88% total, Primary Care: 100%), the prevalence of 0.12% is, however, believed to be real and might be explained by the urban area investigated, with easy access to care and proximity to one somatic hospital. 50% of the patients with leg and foot ulcers were treated in Primary Care, and 30% of the leg ulcer patients were treated at the Department of Dermatology. 88% of leg and foot ulcer patients were over 75 years of age. Median age was 79.5 years, with 80 for women and 76.5 for men. In Primary Care the median age was 82. There was a predominance of women in the study population with an overall sex ratio of 3:1. A higher proportion of patients living alone was found in Primary Care. The etiology of the ulcers was considered to be "unknown" or "other" or else no statement was given in 36% of the leg ulcer- and 22% of the foot ulcer patients. This might reflect an overall uncertainty about the underlying etiological cause. Medially and laterally located leg ulcers were reported equally often, but there was also a great proportion of wholly or partially circumferential ulcers. 76% of the foot ulcers were located on the toes.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
62.
In a double-blind crossover study, 12 depressed inpatients receiving bilateral electroconvulsive therapy (ECT) were given 22.5 mg oxazepam or placebo (identical tablets, randomized order) the night before treatment. Seizure duration was measured using the cuff method and a total of 20 pairs of measurements were made. Mean duration after oxazepam administration was 0.9 s longer than after placebo; this difference was not statistically significant. The relevant lower one-sided 95% confidence limit was -4.1 s. Single administration of oxazepam, 22.5 mg, has little average effect on seizure duration in ECT.  相似文献   
63.
64.
Molecular epidemiology of hepatitis B virus infections in Denmark.   总被引:3,自引:0,他引:3  
BACKGROUND: Denmark has a low incidence of acute hepatitis B (HBV) infections but the impact of an increasing number of immigrants with chronic HBV infection on HBV transmission is unknown. OBJECTIVES: To characterise individuals with chronic and acute HBV infection in a defined region and to examine the importance of different risk groups for the current HBV transmission. METHODS: During 2000-2001 all consecutive HBV infected individuals routinely diagnosed through the regional HBV serology laboratory in the County of Funen were classified according to ethnicity, presumed route of transmission and stage of infection based on clinical data mainly supplied by the requesting physician. HBV DNA was sequenced and subjected to phylogenetic analysis. RESULTS: Of 309 identified cases, 91 (29%) were classified as acute infection. HBV DNA sequencing was possible in 54 (59%) of these cases. Phylogenetic analysis showed that HBV isolated from injecting drug users (IDUs) was identical or closely related. Among acute cases acquired in Denmark 89% (74/83) were seen in IDUs (65) or in individuals presumably exposed to IDUs (nine) and phylogenetic analysis corroborated the assumption of IDU related transmission in every case with available sequence data. Among 83 ethnic Danes who acquired their HBV infection in Denmark, no new cases of transmission from immigrants were detected. CONCLUSION: Injecting drug use was the single most important factor for hepatitis B transmission in Denmark. The current Danish vaccination strategy is unable to protect IDUs from HBV infection and IDUs pose a greater risk of HBV transmission to the general population than immigrants.  相似文献   
65.
1. Impulse response functions were determined from complex point impedance and transfer functions from cultured NG-108 cells to simulate the propagation of a synaptic potential in response to the release of transmitter. In general, the flow of synaptic current has a much shorter duration than the normal membrane time constant, thereby making the use of impulse response functions useful approximations to synaptic events. 2. The resonance observed during the activation of the potassium conductance was reflected in the impulse response function as a pronounced damped oscillation. A comparison of the impulse response functions calculated from point impedance and transfer functions showed similar results for current injections in the growth cone. 3. In addition to the resonance effects of the voltage-dependent conductances on transfer and impulse response functions due principally to the activation of conductances for outward currents, transfer functions were measured during the activation of a steady-state negative conductance. Under these conditions the phase function approaches 180 degrees, indicating that the voltage response is out of phase with the current. 4. In the steady state, the effect of a negative conductance is to algebraically add to the positive conductances and generally decrease the absolute conductance unless there is a net negative current. The decreased conductance enhances the impulse response and the DC space constant, thus leading to a better propagation of slow potentials. This effect can be seen as a decrease in the electrotonic length, L, with intermediate depolarizations. At large depolarizations the steady-state activation of the K conductance generally dominates and leads to a greatly increased electrotonic length. 5. Both the net conductances and the associated kinetics play a role in shaping the potential changes during a synaptic current. This is especially critical if there is a net negative steady-state conductance. Under these conditions there is a surprising reduction in the impulse response function. 6. Thus, during a subthreshold activation of the voltage-dependent negative conductances, the observable synaptic potentials would be either large potential responses due to an apparent increase in the impedance (algebraic summation of positive and negative conductances with a net positive conductance) or a minimal response because of the phasic cancellation due to a net negative conductance. The latter condition could exist near the synaptic reversal potential due to a large synaptic drive and would appear experimentally as a form of inhibition.(ABSTRACT TRUNCATED AT 400 WORDS)  相似文献   
66.
Male and female Long Evan rats and Brattleboro rats with ADH-deficient diabetes insipidus were treated with lithium administered in the diet for 12 weeks. The plasma lithium level was about 1 mmol/l in all groups. Lithium caused polydipsia and polyuria and lowering of renal concentrating ability in normal rats. In rats with ADH deficiency lithium tended to increase water intake, but did not influence spontaneous urine osmolality or maximal urine osmolality during water deprivation. The results indicate that the renal concentrating defect caused by lithium in rats can be explained by ADH-blockade as the only mechanism. However, there is circumstantial evidence that lithium in addition may stimulate thirst mechanisms by an ADH-independent action.  相似文献   
67.
Several reports suggest that the glutathione-S-transferase (GST) family of enzymes is involved in a variety of cancers, due to their carcinogen-detoxification properties. A polymorphism in codon 105 of the pi variant (GSTP1 I105V), which affects the enzymatic activity of the enzyme, has been linked to the incidence of cancers from different organs. However, the published data in prostate cancer (PCa) is controversial. Some studies report an association with the GSTP1 I105V polymorphism and sporadic PCa, whereas other studies report no association. Recently, one study showed a positive correlation between the GSTP1 I105V polymorphism and familial PCa in a Japanese population. In the present study, we assessed the correlation of the GSTP1 I105V polymorphism with familial and sporadic PCa in an American population. We analyzed DNA samples from 438 patients with familial PCa, 499 patients with sporadic PCa, and 510 controls. We found no significant association between the GSTP1 I105V polymorphism and familial or sporadic PCa when compared to the control group [odds ratio (OR) =1.0 (0.74-1.37); P=0.58]. Moreover, no association was found after stratification for age of diagnosis, Gleason grade, or lymph node involvement [OR =0.84 (0.65-1.09), P=0.37]. These data indicate that there is no associated risk for sporadic or familial PCa in American families containing the GSTP1 I105V polymorphism.  相似文献   
68.
Slime production is not a generally recognized feature of Staphylococcus epidermidis. In a recent outbreak of S. epidermidis intravascular catheter-associated sepsis, we noted that 63% of clinically implicated strains grew as a slimy film coating the culture tube walls when propagated in tryptic soy broth. Only 37% of randomly collected blood culture contaminants and skin isolates demonstrated a similar phenomenon (p less than 0.05). Transmission electron micrographs of these coating bacteria showed them to be encased in an extracellular matrix that stained with alcian blue. Slime production was most evident in autoclaved media containing Casamino Acids and glucose supplementation (0.25% wt/vol). There were strain and media preparation variability of slime production in the presence of other carbohydrates. Some strains were not able to produce slime under any of the tested conditions. The production or nonproduction of slime did not influence growth rate. When grown in vitro, slime producers accumulated on the surface of intravascular catheters as macrocolonies, whereas non-slime, producers did not. Transmission and scanning electron micrographs showed slime producers to be encased in an adhesive layer on the catheter surface, whereas nonproducers were not encased. These results suggest that slime-mediated adherence may be a critical factor in the pathogenesis of S. epidermidis infections of medical devices.  相似文献   
69.
In a community sample of 2,327 Caucasians, we tested the hypotheses that polymorphisms in the COMT and DRD3 genes are associated with personality traits conferring vulnerability to anxiety, depression, or alcohol misuse, or with current symptoms of these; and that the association is stronger in persons who also have been exposed to stressor experiences. To conserve resources and to allow replication, the genetic analysis was undertaken in two stages. For the COMT polymorphism, no statistically significant associations were found in the first sample of 862 persons. The remainder of the sample was therefore not analysed for that gene. For the DRD3 polymorphism, those in the first sample with at least one of the Ser(9) alleles had significantly higher scores in neuroticism (p=0.006) and behavioral inhibition (p=0.003). There was a trend, failing to meet the 1% significance criterion, for those with this genotype also to have higher depression and anxiety. The groups did not differ in alcohol use. In persons with the Ser(9) allele who were also exposed to stressors, there was a higher level of depression at the 5% level; and the depression level was higher in homozygotes. But when the remainder of the sample (1,465) was analysed, none of the associations reached statistical significance. We conclude that neither the COMT nor DRD3 polymorphisms are associated with anxiety, depression, or alcohol abuse. Am. J. Med. Genet. (Neuropsychiatr. Genet.) 96:102-107, 2000 Copyright 2000 Wiley-Liss, Inc.  相似文献   
70.
Available Escherichia coli mutants with temperature-sensitive mutations in genes essential for DNA replication have been used to investigate the host protein involvement in the DNA synthesis of bacteriophage T1. This study has shown that T1 is independent of the E. coli initiation gene products dnaA, dnaC, dnaI, dnaP, and dnaT. The gene products of the polC, dnaG, and dnaZ loci, know to be involved in the elongation events of replication, are required for a productive T1 infection. T1 was found to be independent of the functioning of the dnaB gene product in the four dnaB mutants tested.  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