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   1457篇
  免费   92篇
  国内免费   9篇
耳鼻咽喉   12篇
儿科学   18篇
妇产科学   5篇
基础医学   295篇
口腔科学   32篇
临床医学   93篇
内科学   437篇
皮肤病学   17篇
神经病学   71篇
特种医学   22篇
外科学   230篇
综合类   4篇
预防医学   32篇
眼科学   10篇
药学   78篇
中国医学   13篇
肿瘤学   189篇
  2023年   7篇
  2022年   7篇
  2021年   18篇
  2020年   19篇
  2019年   11篇
  2018年   19篇
  2017年   14篇
  2016年   21篇
  2015年   19篇
  2014年   38篇
  2013年   35篇
  2012年   71篇
  2011年   86篇
  2010年   55篇
  2009年   43篇
  2008年   95篇
  2007年   101篇
  2006年   86篇
  2005年   92篇
  2004年   93篇
  2003年   122篇
  2002年   114篇
  2001年   31篇
  2000年   34篇
  1999年   25篇
  1998年   17篇
  1997年   19篇
  1996年   17篇
  1995年   16篇
  1994年   14篇
  1993年   15篇
  1992年   22篇
  1991年   23篇
  1990年   15篇
  1989年   8篇
  1988年   21篇
  1987年   14篇
  1986年   18篇
  1985年   15篇
  1984年   7篇
  1983年   5篇
  1982年   8篇
  1981年   9篇
  1980年   6篇
  1979年   5篇
  1978年   4篇
  1975年   3篇
  1974年   4篇
  1972年   3篇
  1968年   3篇
排序方式: 共有1558条查询结果,搜索用时 31 毫秒
1.
Few studies have demonstrated the optimal usage of common inflammatory markers, alone or in combination, based on the cost-effectiveness. We analyzed the yield and cost of C-reactive protein (CRP), white blood cell count (WBC), erythrocyte sedimentation rate (ESR), sialic acid, and protein fractionation in 177 new primary care outpatients with inflammation-related symptoms. A useful result (UR) was assigned if tests contributed to a change in physician's diagnosis or decision-making. Costs of testing were calculated based on either single or simultaneous measurement. Five inflammatory markers generated 147 URs in 123 patients. CRP showed the best contribution to generation of UR, followed by sialic acid, protein fractionation, WBC, and ESR. CRP demonstrated poor correlation with WBC (r = 0.458), while sialic acid strongly correlated with total absolute amount of alpha1 and alpha2 fractions in protein fractionation (r = 0.855) and moderately with ESR (r = 0.651). The combination of CRP and WBC produced the best cost-effectiveness at a cost of Yen 1169 (US dollars 9.6 or Euro 9.7)/additional UR against CRP testing alone. Sialic acid, an automated multichannel analyzer-based test, demonstrated the favorable cost-effectiveness over ESR or protein fractionation when combined with CRP (and WBC). Our results indicate that the optimal usage of these inflammatory markers should involve careful cost-effectiveness considerations.  相似文献   
2.
Endoscopic submucosal dissection (ESD) for colorectal cancer is not widely accepted because of its technical difficulty and the risk of perforation. In addition, the risk of peritonitis cannot be completely eliminated even if a perforation is closed successfully. Reported here are two cases of early colon cancer in which the patients sustained iatrogenic perforations of the ascending colon during conventional endoscopic mucosal resection and of the sigmoid colon during ESD, respectively, requiring abdominal decompression with an 18 G Medicut needle. Both of these perforations were successfully treated by endoscopic clipping. In conclusion, conservative medical management may be possible in patients who have undergone successful closure of colonic perforations using endoscopic clipping. In order to perform immediate endoscopic closure, abdominal decompression has been useful to decrease patient discomfort and colonic lumen collapse. Now, CO2 insufflation is being used effectively for the prevention of pneumoperitoneum.  相似文献   
3.
Background: The effects of inhalational anesthetics on the microcirculation, including leukocyte dynamics, remain to be clarified. The authors investigated halothane and sevoflurane anesthesia to determine if these agents evoked leukocyte adhesion through endothelial cell-dependent mechanisms involving such adhesion molecules.

Methods: Rats were anesthetized with halothane or sevoflurane in 100% oxygen and the lungs were mechanically ventilated. Leukocyte behavior in mesenteric venules was recorded through intravital video microscopy under monitoring microvascular hemodynamics. To examine the mechanisms for leukocyte rolling and adhesion, these studies were repeated after animals were pretreated with a monoclonal antibody against P-selectin (MAb PB1.3) or against intracellular adhesion molecule-1 (ICAM-1; MAb 1A29): P-selectin required for rolling of circulating leukocytes and ICAM-1 for firm adhesive interactions with leukocyte integrins.

Results: Under baseline anesthetic conditions (1 minimum alveolar concentration [MAC]), venular wall shear rates, an index of the disperse force on marginating leukocytes, in the sevoflurane-treated rats were about two times higher than those with halothane. At 2 MAC, halothane caused a marked arteriolar constriction and decreasing shear rates concurrent with an increasing density of venular leukocyte adhesion. Sevoflurane at 2 MAC induced leukocyte rolling and adhesion, which were attenuated by PB1.3 and 1A29, without alterations in the wall shear rates. Halothane-induced leukocyte adhesion was not prevented by PB1.3 but it was by 1A29.  相似文献   

4.
5.
Extracardiac Direct Total Cavopulmonary Connection   总被引:2,自引:0,他引:2  
We report a successful extracardiac direct total cavopulmonary connection without prosthetic materials performed in a 3-year-old boy with tricuspid atresia, infundibular pulmonary stenosis, and normally positioned great arteries. The transected pulmonary trunk was bought down posterolaterally with respect to the right atrium and was anastomosed end-to-end with the inferior vena cava.  相似文献   
6.
With the recent advances in DNA sequencing technology, a succession of entire genome sequences have been published. A number of genome projects are underway in pathogenic fungi. From these, we present the history and current status of the genomic analysis of Candida albicans. The sequencing project for this organism has been undertaken at Stanford University, and is now nearing the end.  相似文献   
7.
Computer graphics indicate that a steric hindrance exists between valine-110 side chain of human lysozyme (EC 3.2.1.17) and an acetyl group of a modified substrate that contains N6,O-diacetylmuramic acid. To alter the substrate specificity of human lysozyme to be effective on the modified substrate, we replaced the valine-110 residue with various amino acids by site-directed mutagenesis. One of the mutant proteins (valine residue replaced with proline:P110) was secreted in Saccharomyces cerevisiae as at least four components (P110-A, P110-B, P110-C, and P110-D) with different specific activities. Two components, P110-B and P110-D, were isolated in a pure form and structurally characterized. The results suggest that this mutation lowered the lytic activity against Micrococcus lysodeikticus by changing a local conformation of the catalytic site while keeping almost the same substrate binding sites. Our results also indicate that cis/trans isomerization of prolyl peptide bonds probably occurs in vivo and that the conformational change of protein as well as point mutations in genes might influence the molecular evolution of the protein.  相似文献   
8.
The average of normals(AON) method is a quality control(QC) method that uses measured values of patients' samples instead of QC samples. Because this method is easily affected by fluctuations in the patient population and is insensitive to short-term changes in test values, we developed an alternative method based on the moving average(MA) of latent reference values(LRVs) which are the test results of patients whose other related test results are all within reference intervals. We evaluate the new methodology(MALRV) using seven commonly measured biochemical tests. The LRV of each test were selected with reference to four other items that had the highest coincidences of abnormality. The optimum amount of data needed to compute the MA is determined as that making the coefficient of variation(CV) of the consecutive MA over a study period less than 5.0%. The MALRV is computed each time a new LRV is encountered to monitor quality status continuously. The MALRV CV was within 5.0% when sample sizes were between 20 and 110. When shift and trend simulations were performed with the patient data, the corresponding alterations were detected. MALRV is a useful measure for detecting short-term alterations in patient test results, supplementing the conventional QC chart method.  相似文献   
9.
The relation of membrane transport of alkali cations to their external concentrations or to their cellular contents was studied in HeLa cells. Chilling the cells at 0 degrees C reversed cell Na+ and K+ to a mirror image of the normal pattern. Upon rewarming to 37 degrees C the ouabain-sensitive Rb+ uptake became 2-fold faster than the control. A kinetic analysis revealed that the stimulation was due to an increase in the maximal rate of Rb+ uptake, Jmax. The increase in apparent Km was relatively small. The analysis also showed that the ouabain-sensitive cation transport system seemed to have two binding sites for Rb+. The stimulation of Rb+ uptake was related to an increase in cell Na+, and an addition of ouabain abolished such a relation. Net Na+ flux which was in the direction from inside the cells to the medium at hypernormal cell Na+ was iiincreased when cell Na+ ncreased. In contrast, net Na+ flux which was in the opposite direction in the presence of ovabain was reduced and became almost 0 at cell Na+ of 900 nmol/mg of protein. The Na+/Rb+ coupling ratio in the ouabain-sensitive cation transport was apparently less than 1 at nearly physiological cell Na+, but it approached 1.5 when cell Na+ was sufficiently high. The sum of cell K+ plus Rb+ varied inversely with cell Na+, and this relation was unaffected upon treatment with ouabain. When Rb+ uptake declined below 80% of the control, cell K+ plus Rb+ was reduced, however, 40% of the sum of cell cations was still preserved even after complete inhibition of the cation pumps by ouabain treatment of 2 hr. Interrelations of these results are discussed.  相似文献   
10.
It is well known that dendritic cells (DCs) are developed from the peripheral blood of mice when peripheral blood mononuclear cells (PBMCs) are cultured with GM-CSF. We have previously found that immature DCs are present in the blood even in humans. In the present study, we show that CD11c+ CD3- B220- cells in the mouse peripheral blood are immature DCs. The percentage of CD11c+ CD3- B220- cells in the (PBMCs) of normal mice ranges from 0.5 to 2.5%. The CD11c+ CD3- B220- cells in the PBMCs show dendrites, similar in shape to the CD11c+ CD3- B220- cells in the spleen, which are thought to be DCs definitely. However, they have practically no capacity to stimulate the proliferation of allogeneic T cells, and show a lower expression of MHC class II, B7-1 and B7-2 than CD11c+ CD3- B220- cells in the spleen. When the CD11c+ CD3- B220- cells in the PBMCs are cultured with GM-CSF, they show not only the potent ability to stimulate the proliferation of allogeneic T cells but also a higher expression of MHC class II, B7-1 and B7-2. Moreover, they migrate into the spleen when they are injected intravenously. These results suggest that CD11c+ CD3- B220- cells in the PBMCs are immature DCs, and that they migrate into the spleen, where they mature.  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