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   1924篇
  免费   109篇
  国内免费   7篇
耳鼻咽喉   33篇
儿科学   88篇
妇产科学   33篇
基础医学   185篇
口腔科学   52篇
临床医学   166篇
内科学   452篇
皮肤病学   50篇
神经病学   93篇
特种医学   59篇
外科学   273篇
综合类   73篇
预防医学   91篇
眼科学   66篇
药学   166篇
中国医学   15篇
肿瘤学   145篇
  2023年   20篇
  2022年   46篇
  2021年   103篇
  2020年   46篇
  2019年   59篇
  2018年   73篇
  2017年   34篇
  2016年   72篇
  2015年   55篇
  2014年   100篇
  2013年   91篇
  2012年   122篇
  2011年   142篇
  2010年   89篇
  2009年   67篇
  2008年   101篇
  2007年   104篇
  2006年   93篇
  2005年   66篇
  2004年   69篇
  2003年   60篇
  2002年   48篇
  2001年   43篇
  2000年   30篇
  1999年   34篇
  1998年   14篇
  1997年   13篇
  1996年   10篇
  1995年   11篇
  1994年   8篇
  1993年   5篇
  1992年   19篇
  1991年   17篇
  1990年   18篇
  1989年   19篇
  1988年   21篇
  1987年   17篇
  1986年   18篇
  1985年   13篇
  1984年   10篇
  1983年   12篇
  1982年   2篇
  1981年   2篇
  1979年   12篇
  1978年   9篇
  1977年   7篇
  1976年   3篇
  1973年   5篇
  1970年   2篇
  1959年   1篇
排序方式: 共有2040条查询结果,搜索用时 31 毫秒
941.
Conventional pancreatic resections may be unnecessary for tumors of the pancreas that are benign or of low malignant potential and can place the patient at increased risk of developing postoperative exocrine and endocrine complications. Median pancreatectomy is an option that has been investigated in the management of such tumors located in the body of the pancreas. We present our experience with three women who underwent this procedure successfully for neuroendocrine tumors (2) and cystadenoma (1).  相似文献   
942.
Antisera to 4-amino-4′-monochlorobiphenyl, 2-amino-4,5,3′,4′-, and 3-amino-2,6,2′,6′-tetrachlorobiphenyl have been produced in rabbits by conjugating these compounds to proteins using the mixed anhydride method. Extensive characterization studies indicated the antisera were fairly specific to their nonaminated biphenyl analogs. Values for these isomers in Aroclors by radioimmunoassay and gas chromatography correlated well for several of the antisera. Suggestive evidence is presented indicating the feasibility of employing radioimmunoassays for determining the Aroclor product number and concentration in environmental samples. A feature of the assay is the use of nonionic detergents to solubilize the extremely hydrophobic chlorinated biphenyls in a manner permitting their binding to antibodies.  相似文献   
943.
944.
The present prospective study was conducted at two urban slums of Delhi, Kusumpur Pahari and Kathputly Colony, in the peak winter season from November 1994 through February 1995. We studied 642 infants to determine the incidence of acute lower respiratory infection (ALRI) and its relationship to indoor air pollution due to fuel used for cooking (wood or kerosene). In Kusumpur Pahari, there were 317 children (142 wood and 175 kerosene), including 64 controls and 78 cases of ALRI in the wood fuel group and 81 controls and 94 ALRI cases in the kerosene group (p > 0.05). Out of 316 children in Kathputly Colony (174 wood and 142 kerosene), there were 33 and 45 ALRI cases in the wood and kerosene groups, respectively (p < 0.05). Controls were children without ALRI and were used as controls in different groups. The demographic data and risk factors, namely, nutritional and immunization status, were comparable in ALRI cases and controls in both study areas. Pneumonia was the most common ailment in all the groups. Bronchiolitis was reported in 22.5% of the wood group and 27.1% of the kerosene group in Kathputly Colony versus 13.7% in the wood group and 12.1% in the kerosene group in Kusumpur Colony. Only one case of croup was reported from Kusumpur Pahari among wood users. The duration of illness was longer in the Kusumpur Pahari due to poor compliance, feeding, and child rearing habits. In conclusion, a higher incidence of ALRI was reported in kerosene users in Kathputly Colony, a high pollution area; however, the reasons for the differences observed need further elucidation.  相似文献   
945.
OBJECTIVE: We reviewed the records of 126 patients who underwent PEG insertion during a 36-month period to determine the etiology of an observed increase in PEG-related infections. METHODS: Charts were reviewed to determine predictive factors of infection, the occurrence of infection, and culture results of infected sites. Insertion was performed in all cases using a standard sterile, pull-through technique. Infections were defined as having at least two of the following conditions: peristomal erythema, induration, and purulent discharge. RESULTS: PEG infections occurred in 22 patients. During the first 12-month interval, 0 of 25 patients (0%) had PEG-related infections; during the second 12-month interval, four of 37 patients (10.8%); and during the third 12-month interval, 18 of 64 patients (28.1%) (p < 0.05). Cultures from 14 of 22 peristomal infections grew methicillin resistant Staphylococcus aureus (nine), pseudomonads (three), and other organisms (two). One hundred twenty-four of 126 patients received prophylactic antibiotics or were receiving concomitant antibiotics. Of the infected patients, 21 of 22 (95.5%) received prophylaxis, and 11 of 22 (50%) were receiving concomitant antibiotics before PEG. In the noninfected group, 78 of 104 (75%) received prophylaxis, and 47 of 104 (45.2%) received concomitant antibiotics. CONCLUSIONS: Methicillin resistant Staphylococcus aureus is emerging as a major pathogen in PEG site infections. Further prospective studies are needed to establish whether current prophylactic antibiotic recommendations are adequate.  相似文献   
946.
BACKGROUND AND AIM OF THE STUDY: Systemic thromboembolism is a major complication in patients with mitral stenosis (MS), especially in those who have atrial fibrillation (AF). It has been suggested that systemic coagulation activity may be increased in these patients. The study aim was to investigate the relationship between control of ventricular rate and systemic coagulation factors in patients with MS and AF by measuring plasma levels of prothrombin fragment (PF) 1+2, thrombin-antithrombin III complex (TAT) and plasminogen activator inhibitor-1. METHODS: Fifty-four consecutive patients with moderate to severe MS and AF were included in the study. Patients with resting heart rates < 100 beats per min were considered as having a controlled ventricular response rate (group A; n = 28) and those with > 100 beats per min as an uncontrolled ventricular response rate (group B; n = 26). RESULTS: Group A patients had a lower mean mitral gradient and pulmonary artery pressure than group B patients (11 +/- 6 versus 15 +/- 5 and 35 +/- 7 versus 39 +/- 8; p < 0.05, respectively). Plasma concentrations of PF 1+2 (4.17 +/- 2.1 versus 2.95 +/- 1.21; p < 0.01) and TAT III (4.61 +/- 1.75 versus 3.12 +/- 1.01; p < 0.01) were elevated in group B compared with group A. Similarly, group B patients had higher plasminogen activator inhibitor-1 levels than group A patients (7.87 +/- 3.8 versus 5.8 +/- 2.9; p < 0.05). A significant correlation was found between heart rate and plasma PF 1+2 and TAT levels. Multiple logistic regression analysis revealed that heart rate and mean mitral gradient were independent predictors of systemic coagulation activation. CONCLUSION: Besides contributing towards hemodynamic and symptomatic relief, the control of AF rate in MS patients induces a drastic decline in coagulation activation, and may also reduce the incidence of thromboembolism.  相似文献   
947.
BACKGROUND AND AIM OF THE STUDY: The study aim was to examine the long-term outcome (nine years) of mitral balloon valvotomy in pregnant patients with severe mitral stenosis. METHODS: Twenty-three patients with severe, symptomatic (NYHA class III/IV) mitral stenosis underwent mitral balloon valvotomy using an Inoue balloon technique during the second trimester of their pregnancy; mean follow up in 19 patients was 5.1 +/- 2.8 years (range: 1 to 9 years). RESULTS: The procedure was successful in all patients. Immediately after valvotomy, the Doppler-derived mitral valve area increased from 0.90 +/- 0.18 to 1.97 +/- 0.36 cm2 (p <0.0001), and the transmitral mean gradient decreased from 15.7 +/- 4.7 to 5.5 +/- 1.6 mmHg (p <0.0001). Four patients had mild worsening of mitral regurgitation, and six developed insignificant interatrial communication immediately after valvotomy. There was no other morbidity or mortality. Patients showed a significant improvement in mean NYHA class, from 3.0 +/- 0.1 to 1.0 +/- 0.02 (p <0.001). Twenty-two patients had normal deliveries; one cesarean section in week 36 resulted in stillbirth. No developmental abnormalities were seen in the babies. At long-term follow up of mothers, the mitral valve area was 1.8 +/- 0.52 cm2; restenosis developed in three patients (16%). One baby died at one week from sudden infant death syndrome, and one at eight months, from pneumonia. All other children showed normal growth, development and speech for their age. CONCLUSION: Mitral balloon valvotomy using the Inoue balloon technique can provide satisfactory immediate relief and long-term outcome in pregnant patients with severe mitral stenosis.  相似文献   
948.
Seven cases of colorectal (five of colonic and two of rectal) uberculosis are presented. Only one of these patients had associated pulmonary tuberculosis. Radiologic signs of colorectal tuberculosis are nontypical, making the preoperative diagnosis difficult. All five patients with colonic tuberculosis presented with subacute intestinal obstruction and underwent resectional surgery followed by antitubercular chemotherapy. Both patients with rectal tuberculosis presented with rectal strictures and were treated by repeated dilatation combined with antitubercular drugs. All seven patients have been followed for two to ten years and have remained asymptomatic.  相似文献   
949.
BACKGROUND. - The normal increase in isometric developed force (DF) with faster pacing rates, known as the positive force-frequency response/relationship (FFR), is altered in failing myocardium, as shown by its negative response to increased pacing. The objective of this study was to determine if increasing Ca2+ influx with L-type Ca2+ channel (L-CaCh) agonists: BayK 8644 (BayK) and FPL 64176 (FPL) or increased extracellular Ca2+ could increase contractility and normalize the FFR in failing myocardium. METHODS. - Isometric DF was measured in right ventricular trabeculae from failing (n = 28) and non-failing (n = 12) human hearts at various stimulation frequencies (0.5-2.5 Hz) before and after bath application of BayK (250 nM), FPL (100 nM), or high Ca2+ (7.0 mM). Post-rest (PR) experiments were also conducted on several trabeculae. RESULTS. - In trabeculae from failing hearts, the DF decreased with an increase in pacing. Addition of L-CaCh agonists increased DF to similar levels in trabeculae from both failing and non-failing hearts at slow pacing rates, but did not alter the negative FFR in the failing group. During increased rest intervals, the amount of PR potentiation was diminished in trabeculae from failing hearts as compared to the non-failing preparations. CONCLUSION. - This study demonstrates that the abnormal FFR observed in trabeculae from failing hearts is a reliable physiologic signature of the cardiomyopathic state even when DF, at slow stimulation frequencies, is relatively high. These studies further demonstrate that the impaired FFR is not due to an inability to further increase contractility. Rather, our findings suggest that the abnormal FFR and blunted PR potentiation alike are a reflection of an altered functional balance between Ca2+ re-uptake and Ca2+ extrusion.  相似文献   
950.
The pairing of the 14 half-cystine residues of bovine neurophysin was established by sequential proteolytic digestion. Purified released peptides and the residual disulfide-linked core were monitored at each step by use of amino acid analysis, gas-phase sequencing, and mass spectrometry. The approach included application of gas-phase sequencing to assign disulfide pairs in peptides containing multiple disulfides. The results demonstrate that neurophysin disulfides are paired in two distinct domains--an NH2 domain (residues 10-54) containing four disulfides and a COOH domain (residues 61-85) containing three disulfides. The specific disulfide bridges are Cys-10 to Cys-54, Cys-13 to Cys-27, Cys-21 to Cys-44, Cys-28 to Cys-34, Cys-61 to Cys-73, Cys-74 to Cys-79, and Cys-67 to Cys-85. The results place the internally duplicated segments of neurophysin (residues 12-31 and 60-77) in separate domains. Disulfide-pairing patterns within each domain are homologous with the exception of the Cys-10 to Cys-54 bond, which is unique to the NH2 domain and which links the two ends of this domain together. The potential role of the Cys-10 to Cys-54 bond in organizing the hormone-binding site is discussed.  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