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   609篇
  免费   31篇
耳鼻咽喉   17篇
儿科学   34篇
妇产科学   5篇
基础医学   44篇
口腔科学   9篇
临床医学   38篇
内科学   115篇
皮肤病学   12篇
神经病学   19篇
特种医学   21篇
外科学   139篇
综合类   17篇
预防医学   46篇
眼科学   29篇
药学   57篇
中国医学   2篇
肿瘤学   36篇
  2023年   9篇
  2022年   5篇
  2021年   14篇
  2020年   6篇
  2019年   3篇
  2018年   8篇
  2017年   5篇
  2016年   10篇
  2015年   11篇
  2014年   22篇
  2013年   38篇
  2012年   56篇
  2011年   47篇
  2010年   17篇
  2009年   23篇
  2008年   18篇
  2007年   24篇
  2006年   27篇
  2005年   36篇
  2004年   31篇
  2003年   22篇
  2002年   24篇
  2001年   14篇
  2000年   10篇
  1999年   6篇
  1998年   4篇
  1996年   3篇
  1995年   5篇
  1994年   3篇
  1993年   3篇
  1992年   13篇
  1991年   9篇
  1990年   7篇
  1989年   7篇
  1988年   4篇
  1987年   10篇
  1986年   5篇
  1985年   13篇
  1984年   10篇
  1983年   11篇
  1982年   5篇
  1980年   2篇
  1979年   5篇
  1978年   7篇
  1977年   6篇
  1976年   4篇
  1975年   2篇
  1972年   2篇
  1970年   2篇
  1936年   3篇
排序方式: 共有640条查询结果,搜索用时 31 毫秒
1.
Antiphospholipid antibody syndrome (APLS) is a rare disorder characterized by a hypercoagulable state. Manifestations include arterial or venous thrombosis, recurrent fetal wastage, coronary artery disease, valvular heart disease, dilated cardiomyopathy, pulmonary artery hypertension, and intracardiac thrombus. Most commonly mitral valve is affected followed by aortic and then tricuspid valve. In this report, a rare case of spontaneous aortic thrombosis with tricuspid stenosis uncomplicated by other valve lesions is presented with clinical and echocardiographic studies and computed tomographic images.  相似文献   
2.
Farnesyltransferase (FTase) is one of the prenyltransferase family enzymes that catalyse the transfer of 15-membered isoprenoid (farnesyl) moiety to the cysteine of CAAX motif-containing proteins including Rho and Ras family of G proteins. Inhibitors of FTase act as drugs for cancer, malaria, progeria and other diseases. In the present investigation, we have developed two structure-based pharmacophore models from protein–ligand complex (3E33 and 3E37) obtained from the protein data bank. Molecular dynamics (MD) simulations were performed on the complexes, and different conformers of the same complex were generated. These conformers were undergone protein–ligand interaction fingerprint (PLIF) analysis, and the fingerprint bits have been used for structure-based pharmacophore model development. The PLIF results showed that Lys164, Tyr166, TrpB106 and TyrB361 are the major interacting residues in both the complexes. The RMSD and RMSF analyses on the MD-simulated systems showed that the absence of FPP in the complex 3E37 has significant effect in the conformational changes of the ligands. During this conformational change, some interactions between the protein and the ligands are lost, but regained after some simulations (after 2 ns). The structure-based pharmacophore models showed that the hydrophobic and acceptor contours are predominantly present in the models. The pharmacophore models were validated using reference compounds, which significantly identified as HITs with smaller RMSD values. The developed structure-based pharmacophore models are significant, and the methodology used in this study is novel from the existing methods (the original X-ray crystallographic coordination of the ligands is used for the model building). In our study, along with the original coordination of the ligand, different conformers of the same complex (protein–ligand) are used. It concluded that the developed methodology is significant for the virtual screening of novel molecules on different targets.  相似文献   
3.
Three cases of chronic rheumatic heart disease with involvement of all four valves are presented. The involvement of tricuspid and pulmonary valves was suspected clinically and was confirmed by two-dimensional echo, Doppler, hemodynamic and angiographic findings. These findings were also verified surgically and histopathologically in 2 cases. One of the cases died after cardiac catheterization; the other 2 cases were treated surgically with success.  相似文献   
4.
Laparoscopic transhiatal surgery of the esophagus.   总被引:4,自引:0,他引:4  
OBJECTIVE: Esophagectomy is an operation with high morbidity and mortality. Its adoption as a minimally invasive operation worldwide has been slow, but the potential benefits of reducing the trauma of surgery need to be considered. Our 30-month experience with transhiatal esophagectomy in a district general hospital is presented herein. METHODS: Patients were considered for surgery after radiological staging had excluded inoperable disease. Laparoscopic staging was initially performed. Patients with tumors of the esophagus and high-grade dysplasia in a Barrett's esophagus were included. RESULTS: Twenty-nine patients were referred for consideration for resectional surgery. Nine underwent outpatient laparoscopy only. Twenty patients (age range, 34 to 78, 15 males:5 females) underwent resectional surgery. Seventeen transhiatal resections were completed, 2 were converted to open procedures, and 1 transhiatal resection of a benign tumor was performed. Median time of surgery was 415 minutes (range, 320 to 480) and blood loss was 300 mL (range, 200 to 350). The median length of post-operative ventilation and critical care stay were 1 (range, 1 to 4) and 4 (range, 2 to 8) days. Median duration of hospitalization was 17 days (range, 10 to 28). Thirty-day mortality was 0; 1 patient who was converted to an open procedure died after a cerebrovascular event on day 34. CONCLUSION: A zero mortality rate for laparoscopic resection and a low-morbidity rate compare well with morbidity and mortality in reported series using this method and open surgery. Laparoscopic transhiatal esophagectomy is an advanced, complex procedure that can be performed safely in a district general hospital setting.  相似文献   
5.
6.
The objective of radiotherapeutic management in esophageal cancer is to accomplish maximum tumor sterilization with minimal normal tissue damage. This sincere effort is most often countered by the differential in tumor dose response vs normal tissue tolerance. Intraluminal isotope radiation, with its inherent advantage of rapid dose falloff, spares the lungs, the spinal cord, and other vital structures, yet yields adequately high doses to esophageal tumor. Though in existence since the turn of the century, the method of intracavitary radium bougie application dropped out of favor due to technical difficulties imposed by the size of the radium source and radiation exposure to the personnel involved. The authors describe a simple “iridium 192 afterloading intraluminal technique” that eliminates technical problems and reduces radiation exposure considerably.  相似文献   
7.

Textile dyes are becoming a growing threat to the environment. This report presents the findings of the study on the toxicity of the textile dye Alizarin Red S on two freshwater microalgae. The acute toxicity assay revealed that 96-h EC50 values of Chlorella vulgaris and Spirulina platensis were 29.81 mg/L and 18.94 mg/L respectively. The pigments chlorophyll-a, b and carotenoids in C. vulgaris on 96-h exposure to the dye were 2.91, 3.29 and 3.01 times lower in analogy to control whereas Spirulina platensis showed 2.89and 2.56 fold decrease in chlorophyll-a and carotenoid content than control. After the test period of 96-h with dye, the protein content of C. vulgaris and S. platensis were 2.33 and 1.77 times lower compared to the control. The growth inhibition rate, pigment as well as the protein content declined in compliance with the rise in dye concentration, which anticipate paradigm about the toxic effects of the textile dye.

  相似文献   
8.
Human leukocyte response to an endurance race   总被引:3,自引:0,他引:3  
Summary The response of circulating leukocytes (WBC's) with regard to changes in number, proportion of neutrophils versus lymphocytes and changes in lymphocyte function as well as proportions of T and B cells was studied in eleven men who ran a 20-mile race. A marked leukocytosis was noted 10–15 min after the race with the predominant increase being polymorphonuclear leukocytes (P<0.001). A significant rise in mean serum cortisol levels was also noted (P<0.001) which correlated with both the increase in total WBC's (P< 0.001) and granulocytes (P<0.001), but not lymphocytes. The increase in serum cortisol was inversely correlated with miles of prior training (P<0.001). An increase in lymphocytes from 1767±112/mm3 to 2431±202/mm3 was less than that previously described in short-term exercise. As with short-term exercise the most significant increase in lymphocytes was in B lymphocytes bearing surface immunoglobulin (P<0.0025). However, in contrast to short-term exercise lymphocytes maintained good in vitro response to the mitogen phytohemagglutinin.This study demonstrates that endurance racing produces a more marked granulocytosis and less lymphocytosis than short bouts of exercise. It is suggested that the degree of leukocytosis is stress dependent in that it was positively correlated with serum cortisol and inversely correlated with prior training.Supported in part by a joint fellowship from the National and Wisconsin Kidney Foundations  相似文献   
9.
The metabolism and fate of phenyl ring-labeled14C-phenthoate {O,O- dimethylS-[-(carboethoxy)benzyl] phosphorodithioate} was examined in the Valencia orange fruit with emphasis on the characterization of bound phenthoate residues in the fruit peel. The products recovered from the citrus fruit wash were unchanged phenthoate, phenthoate oxon, demethyl phenthoate, phenthoate acid, ethyl mandelate, and mandelic acid. The same products, with the exception of phenthoate oxon, were found in the acetone extract of the fruit peel. Enzymatic hydrolysis of the bound residue in the peel with-glucosidase, followed by acidic and basic hydrolysis gave ethyl mandelate as the major product, followed by mandelic acid, demethyl phenthoate and phenthoate acid. Phenthoate was metabolized and conjugated in citrus fruits into detoxication products.  相似文献   
10.
Alpha‐cypermethrin is an isoform of cypermethrin; it is an active pyrethroid used extensively to control a wide range of pests in agriculture and animal breeding. In this study four groups of six fish were examined. The first group served as a control in fresh water alone, with no pyrethroid. The second, third and fourth groups were exposed to alpha‐cypermethrin for 4, 8 and 96 h respectively. At the end of the each exposure period, the fish were sacrificed, and the required muscle tissues were collected for histological examination. The blood was drawn with heparinized needles and processed for serum enzymatic studies. Serum enzymes such as aspartate transaminase (AST), alanine transaminase (ALT), amylase, acid phosphatase (ACP) and gamma‐glutamyl transpeptidase (GGT) were measured at 4, 8 and 96 h. AST enzyme activity was significantly increased at 4 h, whereas ALT and amylase enzyme activities were significantly reduced at all the time points. ACP enzyme activity was significantly reduced at 4 and 8 h, whereas GGT enzyme activity was significantly increased at all the time points. Hepatocyte cytoplasmic vacuolisation and degeneration, rupture of blood vessels, and necrosis was found at all time points. Congestion of blood vessels, bulging, distortion of filaments, erosion and disintegration of blood corpuscles and hyperplasia of epithelium were found in treated gills at 4, 8 and 96 h. Breakdown of muscle fibres, vacuolation and accumulation of lipids and melanin in white muscle were observed in treated fish muscle at 4, 8 and 96 h.  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