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   132篇
  免费   17篇
  国内免费   26篇
儿科学   6篇
妇产科学   3篇
基础医学   16篇
口腔科学   4篇
临床医学   30篇
内科学   20篇
皮肤病学   13篇
神经病学   2篇
特种医学   14篇
外科学   15篇
综合类   7篇
预防医学   3篇
眼科学   4篇
药学   31篇
中国医学   1篇
肿瘤学   6篇
  2022年   1篇
  2021年   5篇
  2020年   1篇
  2019年   1篇
  2018年   5篇
  2017年   1篇
  2016年   3篇
  2015年   6篇
  2014年   7篇
  2013年   11篇
  2012年   3篇
  2011年   2篇
  2010年   8篇
  2009年   6篇
  2008年   3篇
  2007年   14篇
  2006年   5篇
  2005年   5篇
  2004年   4篇
  2003年   2篇
  2002年   5篇
  2001年   4篇
  2000年   4篇
  1999年   6篇
  1998年   6篇
  1997年   19篇
  1996年   4篇
  1995年   4篇
  1994年   5篇
  1993年   5篇
  1992年   7篇
  1991年   5篇
  1990年   2篇
  1989年   3篇
  1987年   2篇
  1984年   1篇
排序方式: 共有175条查询结果,搜索用时 1 毫秒
71.
帕米膦酸二钠的合成   总被引:2,自引:1,他引:2  
目的:合成二钠3-氨基-1-羟基-亚丙基-二膦酸盐(帕米膦酸二钠)。方法:有,无溶剂的两种合成路线,并对工艺进行改进,所得产物经元素分析,红外光谱,质谱等分析确证结构。结果;两种路线均可合成目标化合物。路线A收率高于路线B。结论:溶剂的加入使本反应体系均一,有利于产物生成。  相似文献   
72.
The expression of the anti-apoptotic molecules Bcl-2 and transforming growth factor-beta 1 is known to confer protective effects on the cerebral ischemia-reperfusion injury.The current study investigated the expression levels of Bcl-2 and transforming growth factor-beta 1 in response to multiple pre-ischemia electro-acupuncture at acupoints Zusanli(ST36)and Fengchi(GB20) stimulation.Rats were divided into five groups:uninjured,control,non-acupoint,GB20 and ST36. Rats in the non-acupoint,GB20 and ST36 groups received 30 minutes(3 times or 18 times)of electro-acupuncture stimulation before experimental cerebral ischemia was induced.Bcl-2 and transforming growth factor-beta 1 were found to be significantly increased in the ST36 groups with either 3 or 18 electro-acupuncture treatments(P<0.05).The production was higher with 18 electro-acupuncture treatments in the ST36 groups(P<0.05).In the GB20 groups,significant increase was only observed in transforming growth factor-beta 1 with 18 electro-acupuncture treatments(P<0.05).No significant elevation of the level of transforming growth factor-beta 1 was observed in the non-acupoint groups.However,the production of Bcl-2 increased with 18 treatments in the non-acupoint groups(P<0.05).The data suggest that multiple pre-ischemia electro-acupuncture at ST36 was effective in conferring neuroprotective effect on the brain by means of upregulation of Bcl-2 and transforming growth factor-beta 1 and the effect was increase with the number of treatment.  相似文献   
73.
74.
75.
1. The plasma brain natriuretic peptide (BNP) concentration is elevated in patients with essential hypertension and normal systolic function. This may be related to left ventricular hypertrophy or diastolic dysfunction, both of which commonly occur in hypertension. 2. Echocardiography was performed on 32 patients with newly diagnosed untreated mild-to-moderate hypertension (19 men, 13 women; mean±SD age 51±15 years; diastolic blood pressure 99±12mmHg; systolic blood pressur. 153.2±18.0 mmHg; plasma creatinine 86±15 μmol/L; creatinine clearance 92.2±20.5 mL/min; left ventricular mass index 116±28 g/m2; left ventricular ejection fraction 66±9%). A 15 mL peripheral venous blood sample was obtained at the time of echocardiography for radioimmunoassay of BNP. 3. Sixteen patients had abnormal Doppler transmitral flow (E/A rati. < 1) and a higher median plasma BNP concentration compared with those patients with E/A ≥1 (12.9 vs 5.9 pmol/L, respectively; P = 0.006). The plasma BNP level correlated significantly with E/A ratio (r = -0.50; P = 0.035). Multivariate analysis showed that the E/A ratio is related to plasma BNP, independent of age and blood pressure. 4. Our results suggest that the plasma BNP level is influenced by diastolic dysfunction. Further studies are needed to determine whether assay of plasma BNP helps to identify patients with diastolic dysfunction.  相似文献   
76.
EJ Read  ; LL Cardine  ; MY Yu 《Transfusion》1991,31(6):502-508
In vivo survival studies of human red cells (RBCs) are commonly carried out by using chromium-51 (51Cr), a gamma-emitting radionuclide, as the cell label. The effects of labeling human RBCs with PKH-2, a nonradioactive lipophilic fluorescent dye that binds to the cell membrane, and the feasibility of detecting the labeled cells by flow cytometric analysis were investigated. Optimal labeling, defined as maximum mean fluorescence intensity with minimal cell-to-cell variability in fluorescence intensity and minimal cell loss, was achieved with the use of 15.0 x 10(-6) M (15.0 x 10(-6) mol/L) PKH-2 and a cell concentration of 4.0 x 10(9) RBCs per mL. Both freshly drawn and stored RBCs could be labeled, but RBCs stored for more than 20 days did not take up the label as uniformly as fresher cells. Although labeling with PKH-2 did not interfere with the detection of ABO, Rh(D), or common minor RBC antigens by routine serologic methods, it resulted in a morphologic appearance resembling echinocytosis and an increased resistance to osmotic lysis by hypotonic saline. RBCs labeled by this method could be quantitated accurately in blood samples in which their proportion was 0.01 percent, or 1 labeled cell in 10,000 cells. This method holds promise as a simple, reliable, and sensitive method for the detection of labeled human RBCs, but the in vivo significance of the label's effects on cell morphology and osmotic fragility is not known. Further studies directly comparing PKH-2-labeled and 51Cr-labeled RBCs will be necessary to establish the accuracy of the former method in determining the in vivo survival of human RBCs.  相似文献   
77.
78.
Background : In the past, practitioners have used distance and/or near visual acuity (VA) to calculate required magnification for low vision aids. Magnification was usually under‐estimated when compared with the final magnification prescribed. Recent studies have emphasised the importance of acuity reserve in determining the required magnification for optimum reading rate. Two different approaches have been proposed for the appropriate acuity reserve to use in calculating magnification. These are a fixed acuity reserve of 0.3 log unit or an individual determination of optimum acuity reserve. The aim of this study was to investigate the magnification and reading rates with low vision aids selected by the two methods. Methods : Nineteen low vision subjects with age‐related macular degeneration (AMD) who were experienced magnifier‐users were recruited. Reading rates and near VA with low vision aids determined by the fixed and individual acuity reserve methods were compared with the same measures made with the subjects' own magnifiers. Results : There were no significant differences in reading rate and near VA measured with low vision aids selected by either the fixed or individual acuity reserve methods or the subjects' own magnifiers. Reading rate with low vision aids was not significantly different from reading rate for large print with conventional near additions. Thus, for experienced users, magnifiers do not cause reduced reading rate. Conclusions : The fixed acuity reserve method is simple to apply as only near VA and print size of the target reading task are required. For the individual acuity reserve method, reading rates at different print sizes need to be measured. We recommend the use of a fixed acuity reserve (0.3 log unit) for the calculation of required magnification for low vision patients. If near VA or reading rate are not satisfactory with the magnification calculated by this method, individual assessment of required acuity reserve is necessary.  相似文献   
79.
We have investigated whether a protective immune response occurred in mice infected with a virulent cloned strain of Plasmodium chabaudi. Animals inoculated intravenously with 10(7) parasitized erythrocytes (PE) showed an exponentially increasing parasitaemia and died by day 6 of the infection, presenting a pronounced anaemia. Smaller inocula produced a longer pre-patent period but did not change the lethal course of infection, since mice injected with 100 parasites died on day 12. When anaemia was compensated for by red blood cell (RBC) transfusion, infected mice recovered and thereafter exhibited a strong immunity, comparable to that of mice immunized by a drug-controlled infection. The immune response was P. chabaudi specific, as the mice were fully susceptible to a challenge by P. yoelii. Three transfusions of 5 x 10(9) RBC per mouse at 2-day intervals were necessary before all the animals were able to control the infection. Transfusion of a larger number of RBC resulted in a lower anaemia and a delay in reticulocytaemia but, paradoxically, the expression of the immune response was delayed. Three transfusions of 1.2 x 10(10) RBC enabled three out of eight mice to survive the infection, while six transfusions enabled all the mice to survive. The data suggest that parasitized immature RBC could play an important role in triggering the protective immune response.  相似文献   
80.
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