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   7719篇
  免费   470篇
  国内免费   22篇
耳鼻咽喉   102篇
儿科学   252篇
妇产科学   109篇
基础医学   1258篇
口腔科学   193篇
临床医学   636篇
内科学   1760篇
皮肤病学   219篇
神经病学   576篇
特种医学   527篇
外国民族医学   2篇
外科学   1203篇
综合类   69篇
一般理论   1篇
预防医学   490篇
眼科学   95篇
药学   370篇
  1篇
中国医学   9篇
肿瘤学   339篇
  2021年   115篇
  2020年   63篇
  2019年   84篇
  2018年   116篇
  2017年   84篇
  2016年   138篇
  2015年   141篇
  2014年   172篇
  2013年   240篇
  2012年   324篇
  2011年   373篇
  2010年   187篇
  2009年   201篇
  2008年   323篇
  2007年   363篇
  2006年   342篇
  2005年   279篇
  2004年   281篇
  2003年   319篇
  2002年   271篇
  2001年   247篇
  2000年   273篇
  1999年   218篇
  1998年   102篇
  1997年   94篇
  1996年   93篇
  1995年   87篇
  1994年   83篇
  1993年   61篇
  1992年   119篇
  1991年   127篇
  1990年   110篇
  1989年   126篇
  1988年   143篇
  1987年   153篇
  1986年   131篇
  1985年   127篇
  1984年   96篇
  1983年   75篇
  1981年   53篇
  1979年   77篇
  1978年   67篇
  1977年   49篇
  1976年   51篇
  1974年   61篇
  1973年   76篇
  1972年   53篇
  1971年   52篇
  1970年   50篇
  1968年   51篇
排序方式: 共有8211条查询结果,搜索用时 15 毫秒
991.
Much of the ill health of Australian indigenous populations can be attributed to diet-related diseases. This community nutrition project is part of a wider renal screening and prevention program based in the Umoona aboriginal community in Coober Pedy in South Australia's far north. The nutrition project facilitates the capacity of the Umoona aboriginal community to identify and redress nutrition-related issues considered important in improving their overall health status. Project nutritionists developed and implemented a specialized nutrition training program with the Umoona aboriginal health workers. The nutritionists were responsive to requests from community groups to provide nutrition expertise and support in program development. Individual nutrition counseling for adults and children taking part in renal health screening was also provided. The aboriginal health workers reported increased nutritional knowledge and confidence in addressing nutrition-related issues within the community after nutrition training. Individual consultations and partnerships formed with community groups have increased awareness and prompted action to address the importance of nutrition in renal disease and overall health in the Umoona community.  相似文献   
992.
A prospective blind comparison was completed between duplex sonography and angiography of the vertebral arteries. Thirty-two vertebral arteries were studied for direction of flow, degree of origin plaque or stenosis, Doppler characteristics, and vessel size. The vertebral arteries were reliably identified by imaging their course from the subclavian artery into the transverse foramina and by identifying a Doppler signal similar in waveform to the internal carotid artery. With Doppler, a 90% accuracy was obtained for direction of blood flow. Nonvisualization of origins was primarily due to vessel depth and/or tortuosity. In 12 vessel origins that were well seen with both techniques, angiography and sonography agreed in two-thirds of the cases. In four cases, origin plaque was underestimated with duplex imaging. Interestingly, no Doppler frequency or velocity elevation was identified distal to significant stenoses. One false-positive diagnosis of occlusion occurred with sonography, in which a 99% origin stenosis resulted in no detectable Doppler signal. By comparing sonography with angiography, sonography was shown to be 80% accurate in determining vertebral artery size. Our preliminary results indicate that duplex scanning is a reasonably accurate screening technique for size, patency, and direction of blood flow in the vertebral arteries. Duplex evaluation of the vertebral artery origin was limited by vessel depth, tortuosity, and calcifications.  相似文献   
993.
994.
The aim of this study was to evaluate the clinical relevance of coronary artery calcifications detected by spiral CT, congruence with fluoroscopy (FS) and coronary angiography, and comparison with studies reporting on application of double-helical CT and ultrafast CT. Forty patients underwent spiral CT (2-mm slice thickness, table feed 3 mm/s), coronary angiography, and FS (performed in the usual manner). Stenosis and calcifications were evaluated semiquantitatively. Nineteen patients suffering from a stenosis ≥ 75 % were verified at coronary angiography. All had coronary artery calcification on spiral CT. Fluoroscopy did not detect 8 of 19 patients with a stenosis ≥ 75 % (1 vessel: n = 1; 2 vessels: n = 3; 3 vessels: n = 4). In spiral CT sensitivity was 100 % and specificity was 33 % (FS: 58 and 48 %). Positive predictive value was 83 % for spiral CT (FS: 50 %), and negative predictive value was 100 % (FS: 56 %). A significant linear increase in the calcification score was found for increasing maximal stenosis (p < 0.005). Spiral CT is more sensitive than FS in the recognition of hemodynamic relevant stenoses using the detection of coronary artery calcifications. Statistical parameters are comparable to ultrafast-CT. Spiral CT is a suitable non-invasive diagnostic technique in coronary heart disease. Coronary calcifications found incidentally in symptomatic patients at chest CT should be reported to the referring physician for further cardiological workup. Received 14 July 1997; Revision received 29 December 1997; Accepted 5 January 1998  相似文献   
995.
BACKGROUND: The effect of non-pulsatile, normothermic cardiopulmonary-bypass (CPB) on the splanchnic blood-flow and oxygen-transport, the hepatic function and the gastrointestinal barrier were observed in a prospective observational study in 31 adults undergoing cardiac valve replacement surgery. METHODS: The splanchnic (i.e. hepatic) blood-flow (HBF) was measured by the constant infusion of indocyanine-green (ICG) using a hepatic-venous catheter. Liver function was examined by calculation of lactate uptake, ICG extraction and the monoethylglycinexylidide (MEGX) test. A day before and after surgery the gastrioduodenal and intestinal permeability was measured by determination of sucrose and lactulose/mannitol excretion. RESULTS: Splanchnic blood flow and oxygen delivery did not decrease during and after surgery while splanchnic oxygen consumption (P < 0.0125) and arterial lactate concentrations increased. The splanchnic lactate uptake paralleled the lactate concentration. After but not during CPB an increase of systemic oxygen consumption was observed. The MEGX test values decreased on the first day after surgery. The ICG extraction was attenuated during the operation. The gastroduodenal and the intestinal permeability increased significantly postoperatively (P < 0.002, respectively, P < 0.001). There was no correlation between these findings and the duration of CPB. There was a significant correlation of the intestinal permeability but not of the gastroduodenal permeability between the prior and after surgery values (P < 0.001). CONCLUSION: Increased oxygen consumption during CPB may indicate an inflammatory reaction due to the pump beginning in the splanchnic area or a redistribution of the splanchinc blood flow during the CPB. Normothermic CPB does not lead to a significant or prolonged reduction of liver function. Normothermic CPB causes an increase of gastrointestinal permeability. The intestinal barrier function prior to surgery was accountable for the degree of loss of intestinal barrier function following surgery.  相似文献   
996.
997.
BACKGROUND: Uraemic pruritus (UP) is still one of the most vexing and disabling symptoms in chronic renal failure. The pathogenesis of UP is obscure and effective therapeutic strategies are elusive. Deduced from partial successful treatment modalities, there is evidence that an alteration of the immune system with a pro-inflammatory pattern along with a deranged T-helper-cell differentiation may be involved in the pathogenesis of UP. We, therefore, investigated whether UP is related to an augmented Th1-differentiation as measured by determination of intracytoplasmatic (i.c.) cytokines and expression of chemokine receptors. Additionally, pro-inflammatory cytokines were determined in serum. METHODS: In a multicentre study, 171 patients on haemodialysis (HD) were screened for UP. Finally, 13 HD patients with and 13 HD patients without UP, as well as 15 healthy controls were enrolled in the study. Peripheral blood mononuclear cells were isolated and the proportion of Th1- and Th2-cells was determined by flow cytometry. The expression of chemokine receptors on CD4 cells (CXCR3 preferentially on Th1 and CCR4 on Th2) and i.c. cytokines (IFNgamma for Th1 and IL4 for Th2) were measured after in vitro stimulation. Serum cytokine levels (IL6 and TNFalpha) and CRP were measured by ELISA. RESULTS: Compared to HD patients without UP, those complaining of UP showed a significantly enhanced proportion of Th1-cells as measured by both techniques. Additionally, serum CRP and IL6 levels were significantly higher in HD patients with UP, compared to HD patients without UP. CONCLUSIONS: These results point to a central role of inflammation in the pathogenesis of UP in HD patients.  相似文献   
998.
Sonography of the neck and superior mediastinum is a very instructive method of investigation. However, the topographical anatomy of the region makes major demands on the investigator. In many diseases in this area, ultrasonography may be used as the first and also only imaging method (thyroid, salivary glands, lymph nodes). Pathological findings are detected with high sensitivity. The dynamic investigation with palpation, compression and observation of deglutition is especially helpful in appraising the consistency, displace-ability and topographical identification of structures. The specificity can be substantially improved by use of color Doppler sonography and ultrasound-guided biopsy. The pharyngeal and retropharyngeal space, the base of the brain and the posterior mediastinum are difficult to access by sonography. The investigator must therefore arrange for supplementary imaging procedures such as CT, MRI or thyroid scintigraphy in unclear cases, e.g. in diagnosis and staging of tumors. Mediastinal space occupations are most frequent in the anterior upper mediastinum. They can be appraised almost as reliably by transthoracic sonography as by computer tomography.  相似文献   
999.
The in vivo washout kinetics of [3H]quinuclidinyl benzilate ([3H]QNB) varies significantly in various structures in the rat brain. The slowest washout rates are from the hippocampus, corpus striatum, and cortex, intermediate rates are exhibited from the thalamus and colliculi, while the fastest washout rate is from the cerebellum. We have also demonstrated a difference in the in vitro dissociation rates (k-1) of [3H]QNB from various structures. The k-1 for the hippocampus, corpus striatum and cortex, is two-fold slower than that observed in the thalamus, colliculi, and cerebellum. The differences in the in vitro dissociation kinetics are not, however, sufficient to explain the differences in the in vivo washout kinetics. We have developed a theoretical formulation which describes conditions under which the washout kinetics are a function of the concentration of receptor in a structure. Furthermore, we present a graphical method in which a plot of the reciprocal of the observed washout rate constant, 1/k(obs), vs receptor concentration is linear. Analysis of the washout kinetics of [3H]QNB from various structures of the CNS of rat were well described by this theory when the differences in in vitro k-1 are included.  相似文献   
1000.
The effect of bis-(p-cyanophenyl)imidazo-1-yl-methane hemisuccinate (CGS 18320B) and other non-steroidal compounds on the aromatization of androstenedione by human placental microsomal aromatase was studied. CGS 18320B exhibited competitive inhibition with an apparent Ki of 0.16 nM, a 90 and 3800-fold increase in affinity compared to 4-hydroxyandrostenedione and amino-glutethimide, respectively. The inhibition is not time-dependent, indicating that the active site interaction is reversible. CGS 18230B showed a two-fold increased affinity as compared to 4-(5,6,7,8-tetrahydroimidazo[1,5a]pyridin-5-yl)benzonitrile (CGS 16949A) and cis-1-[(4-[(1-imidazoyl)methyl]cyclohexyl)methyl]-imidazole succinate (CGS 14796C) which showed Ki values of 0.35 and 0.39 4M, respectively. 1-[2-[1-(4-carboxyphenyl)-3-ureido]ethyl]-2-(4-pyridyl)-2-imidazoline monohydrochloride (CGP 15720A) showed negligible inhibition.  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