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   3507篇
  免费   178篇
  国内免费   10篇
耳鼻咽喉   27篇
儿科学   181篇
妇产科学   77篇
基础医学   374篇
口腔科学   79篇
临床医学   316篇
内科学   765篇
皮肤病学   127篇
神经病学   223篇
特种医学   371篇
外科学   331篇
综合类   52篇
预防医学   408篇
眼科学   39篇
药学   171篇
中国医学   5篇
肿瘤学   149篇
  2023年   21篇
  2022年   28篇
  2021年   45篇
  2020年   29篇
  2019年   42篇
  2018年   101篇
  2017年   58篇
  2016年   55篇
  2015年   80篇
  2014年   84篇
  2013年   142篇
  2012年   180篇
  2011年   202篇
  2010年   104篇
  2009年   102篇
  2008年   177篇
  2007年   190篇
  2006年   179篇
  2005年   188篇
  2004年   206篇
  2003年   159篇
  2002年   175篇
  2001年   115篇
  2000年   100篇
  1999年   92篇
  1998年   37篇
  1997年   56篇
  1996年   42篇
  1995年   41篇
  1994年   35篇
  1993年   28篇
  1992年   56篇
  1991年   47篇
  1990年   35篇
  1989年   49篇
  1988年   45篇
  1987年   62篇
  1986年   44篇
  1985年   36篇
  1984年   25篇
  1983年   19篇
  1982年   20篇
  1981年   19篇
  1980年   19篇
  1979年   13篇
  1978年   16篇
  1977年   13篇
  1974年   11篇
  1973年   12篇
  1972年   12篇
排序方式: 共有3695条查询结果,搜索用时 31 毫秒
41.
In December 1992, Enterobacter cloacae was isolated from the oropharynx and respiratory tract of six ventilated neonates hospitalized in the intensive care unit (ICU) of our hospital. To establish the spread of the outbreak, 41 strains of E. cloacae were analyzed for genotypic markers by three methods: plasmid profile analysis, ribotyping with EcoRI or PvuII endonuclease, and arbitrarily primed (AP) PCR. The tested strains included 12 isolates from the 6 epidemic cases, 4 isolates from the respiratory tract of 4 children hospitalized in other wards during the same period, 13 isolates from 12 children hospitalized in pediatric units before or after the outbreak, and 12 epidemiologically unrelated isolates. Ribotyping and AP PCR demonstrated that each of the last 12 strains exhibited distinct genomic patterns, as did each of the strains isolated from neonates hospitalized before or after the epidemic peak. Conversely, two clones of strains were found among the isolates recovered in December, with concordant results being obtained by the three typing methods: the first clone included seven strains from five ventilated children in the ICU and two children from another ward; another clone was shared by one neonate in the ICU and an infant from another ward. These results indicate that ribotyping and AP PCR-the latter applied, to our knowledge, for the first time to the genotypic analysis of E. cloacae--represent very discriminatory tools for the investigation of nosocomial outbreaks caused by this species.  相似文献   
42.
Here we analyze limb development after the conditional inactivation of Fgf8 from the epiblast, using the previously described MORE (Mox2Cre) line. This line drives variable mosaic recombination of a floxed Fgf8 allele, resulting in a small proportion of AER cells that maintain Fgf8 expression. The phenotype of Mox2Cre;Fgf8 limbs is most similar to that of Msx2Cre;Fgf8 forelimbs, indicating that a small but durable expression of FGF8 is equivalent to an early normal, but transitory, expression. This functional equivalence likely relies on the subsequent Fgf4 upregulation that buffers the differences in the pattern of Fgf8 expression between the two conditional mutants. The molecular analysis of Mox2Cre;Fgf8 limbs shows that, despite Fgf4 upregulation, they develop under reduced FGF signaling. These limbs also exhibit an abnormal area of cell death at the anterior forelimb autopod, overlapping with an ectopic domain of Bmp7 expression, which can explain the abnormal morphogenesis of the anterior autopod.  相似文献   
43.
Monoclonal antibodies against Vibrio cholerae lipopolysaccharide.   总被引:11,自引:5,他引:11       下载免费PDF全文
A cell line producing monoclonal antibodies directed against the core region of Vibrio cholerae lipopolysaccharide has been established. These antibodies were inhibited by lipopolysaccharide preparations of both O-group 1 vibrios and some non-O-group 1 vibrios as detected in enzyme-linked immunosorbent assay-inhibition experiments. Coagglutination experiments with monoclonal and polyclonal antibodies adsorbed to protein A-carrying staphylococci were performed. All V. cholerae strains tested, regardless of serotype, were agglutinated when mixed with staphylococci coated with the monoclonal antibodies, whereas staphylococci coated with group-specific (O1) polyclonal antibodies only agglutinated with O-group 1 vibrios.  相似文献   
44.
Although firefighters have been shown in some studies to suffer chronic respiratory morbidity from their occupational exposures, an increased risk for dying from non-malignant respiratory diseases has not been documented in any previous retrospective cohort mortality study. In order to assess the possibility that an unusually strong "healthy worker effect" among firefighters might mask this increased risk, a mortality analysis of firefighters was carried out in three cities in relation to the United States population and also to a comparison cohort of police officers. The firefighters were employed between 1945 and 1980 and experienced 886 deaths by 1 January 1984; compared with the United States population they had a significantly reduced risk of dying from all causes (SMR = 82, 95% confidence interval, 77-87), and from non-malignant circulatory diseases (SMR = 81, 95% confidence interval 73-89), but no significant difference in risk of non-malignant respiratory diseases (SMR = 88, 95% confidence interval 66-117). Compared with police, the firefighters experienced a trend toward improved mortality outcomes for all causes investigated (SMR = 82), but they had an excess of deaths from non-malignant respiratory diseases (SMR = 141). The results indicate that firefighters are probably at increased risk for dying from non-malignant respiratory diseases; this increased risk may have been missed in previous studies because of the limitations of using a general reference population.  相似文献   
45.
By in situ hybridization we studied the expression patterns of Msx and Hoxd genes during the late development of the chick leg autopodium (foot) and compared them to patterns during the experimental development of interdigital extra digits. Extra digits are induced in the third interdigital space after various experimental manipulations, such as transient isolation of the interdigit, or removal of the interdigital marginal ectoderm and mesoderm. Msx1 and Msx2 are normally expressed in the interdigital tissue programmed to die. Our experiment changes the fate of the interdigital tissue from cell death to chondrogenesis and provides a good model for studying Msx involvement in defining areas of programmed cell death. Among the proposed roles for Hoxd genes is their involvement in the specification of digit identity early in development. The induction of extra digits allows us to examine whether this new morphogenetic commitment of the interdigital tissue involves changes in the domains of expression of Hoxd genes. Our results show that extra digits develop without a previous modification of the normal pattern of expression of Msx or Hoxd genes. This observation does not support the correlation between the expression of Msx genes and programmed cell death and suggests a role for these genes in maintaining the interdigital tissue in an undifferentiated state. Our results show that an increased number of digits can be formed without modifications in the pattern of expression of the 5-located Hoxd genes and suggest the existence of latent or residual digit organization mechanisms past the time when digits are normally determined, independent of Hoxd gene expression.  相似文献   
46.
Increased sweat concentrations (92, 76 and 80 mEq/l) were observed in a 7-year-old boy with pitressin-resistant diabetes insipidus. All previous observations of elevated sweat electrolytes in diabetes insipidus have been in infants less than 10 months of age. The sweat test is an exceptionally reliable, sensitive and specific test for the diagnosis of Cystic Fibrosis. Pitressin-resistant diabetes insipidus is one of the diseases associated with elevated sweat test results.  相似文献   
47.
Nitric oxide (NO) has been reported to mediate several effects in response to muscarinic cholinergic stimulation in cardiovascular tissues. Recently, an attenuation of guinea pig cardiac myocyte contraction by NO has been described. The aim of the present study was to determine whether the indirect negative inotropic effect of M-cholinoceptor stimulation in human myocardium is in part due to an effect of endogenous NO. Therefore, the effect of carbachol was studied under control conditions and during inhibition of NO-synthase by pretreatment with NG-monomethyl-l-arginine (NMMA). Functional experiments were performed in isolated, electrically driven (1 Hz, 37°C) left ventricular papillary muscle strips of human myocardium. Since cytokines have been reported to be increased in the serum of patients with heart failure and could induce NO-synthase activity in failing myocardium, we compared samples from nonfailing and terminally failing (classified as NYHA IV) hearts. The indirect negative inotropic effect of carbachol (10 mol/l) was studied in the presence of the \-adrenoceptor agonist isoprenaline (0.03 mol/l).After stimulation with isoprenaline, carbachol significantly (P < 0.05) reduced force of contraction. This effect was diminished in failing myocardium compared to nonfailing, probably due to the diminished inotropic response most likely due to the lower cAMP levels in response to \-adrenoceptor stimulation in the former condition. Pretreatment with NMMA (100 mol/l) altered the antiadrenergic effect of carbachol neither in nonfailing nor in failing preparations. Furthermore, inhibition of guanylyl cyclase, the target enzyme of NO, by preincubation with methylene blue (10 mol/l) for 30 min had no effect on the carbachol-induced decrease in force of contraction. Basal force of contraction, as well as the positive inotropic effect of isoprenaline remained unaffected by NMMA or methylene blue.The present study provides evidence that the indirect negative inotropic effect of M-cholinoceptor agonists is not due to an effect of NO in the human myocardium. Furthermore, the well known enhancement of cGMP in response to M-cholinoceptor stimulation appears not to be involved in this antiadrenergic effect.  相似文献   
48.
The present study describes a clinical trial in which Spanish patients suffering from peripheral vascular disease (Fontaine stage II) were given specific lipid supplements. Designed as a longitudinal intervention study, patients were provided with olive oil for 3 months, followed by a 3 month wash-out period, then supplemented with a combination of fish oil and olive oil for the final 3 months. Changes in plasma and lipoprotein fatty acid composition and susceptibility of LDL to in vitro oxidation were examined. Furthermore, lipid-supplement-induced changes in LDL properties were measured as relative electrophoretic mobility and macrophage uptake. In addition, thirteen patients not provided with olive oil and fish oil were included as a control group and twenty healthy age-matched individuals were used as a reference group. A complete clinical study and a nutritional survey concerning food habits and lifestyle were performed every 3 months. Yao indices and claudicometry did not change significantly with dietary intervention although changes in plasma lipid composition suggested an improvement in the condition of the patients. The intake of the fish-oil supplement resulted in significantly increased plasma levels of eicosapentaenoic acid (20:5n-3) and docosahexaenoic acid (22:6n-3) in comparison with baseline concentrations, olive-oil and control groups. Fish-oil consumption significantly decreased plasma triacylglycerol levels compared with the olive-oil period, control and reference groups. The susceptibility of LDL to Cu-mediated oxidation was lower in the patients consuming olive oil and the fish-oil supplement than in the control group, and the uptake of LDL by macrophages was significantly lower in the group supplemented with fish oil. In conclusion, consumption of olive oil together with a dietary supplement of fish oil may be useful in the nutritional management of patients suffering from peripheral vascular disease in terms of increasing plasma n-3 long-chain polyunsaturated fatty acids and decreasing susceptibility of LDL to oxidation.  相似文献   
49.
Tamoxifen versus placebo in the treatment of Peyronie's disease   总被引:3,自引:0,他引:3  
PURPOSE: We evaluated the effects of oral tamoxifen and placebo in patients with Peyronie's disease. MATERIALS AND METHODS: We selected 25 patients with Peyronie's disease who did not have calcified plaque for treatment in the andrology outpatient clinic. A medical history was obtained, and physical examination, penile x-ray, penile ultrasound and pharmacologically induced erection with prostaglandin E1 were performed. Patients were randomly divided into group 1--those who received 20 mg. tamoxifen twice daily for 3 months and group 2--those who received placebo for the same period. The same evaluations were done 4 months later and results were compared. Qualitative (chi-square test) and quantitative (Student's t test) results were analyzed using the Yates correction factor with p <0.05 considered significant. RESULTS: Pain subsided in 66.6 and 75% of the patients treated with tamoxifen and placebo, respectively (p >0.05). In groups 1 and 2 a reduction in the penile deformity was noticed by 46.1 and 41.7% of the patients (p >0.05), and a decrease in plaque size was noticed by 30.7 and 25%, respectively. On the other hand, objective measurements did not reveal any difference in plaque area or curvature angle. CONCLUSIONS: This study did not show significant improvement in pain, curvature or plaque size in patients with Peyronie's disease who were treated with tamoxifen compared with those treated with placebo.  相似文献   
50.
Presentation of eight cases of urinary candidiasis in patients who underwent radical cystectomy and were managed using by-pass of the urinary tract, oral antifungal therapy and solutions in the way of intermittent instillation through nephrostomy catheters.  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