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   11354篇
  免费   712篇
  国内免费   62篇
耳鼻咽喉   105篇
儿科学   312篇
妇产科学   228篇
基础医学   1640篇
口腔科学   255篇
临床医学   994篇
内科学   2577篇
皮肤病学   424篇
神经病学   1146篇
特种医学   263篇
外科学   958篇
综合类   57篇
现状与发展   1篇
一般理论   3篇
预防医学   1351篇
眼科学   217篇
药学   780篇
中国医学   50篇
肿瘤学   767篇
  2024年   11篇
  2023年   139篇
  2022年   269篇
  2021年   506篇
  2020年   261篇
  2019年   430篇
  2018年   520篇
  2017年   316篇
  2016年   303篇
  2015年   376篇
  2014年   526篇
  2013年   639篇
  2012年   982篇
  2011年   945篇
  2010年   549篇
  2009年   445篇
  2008年   716篇
  2007年   709篇
  2006年   603篇
  2005年   645篇
  2004年   553篇
  2003年   508篇
  2002年   455篇
  2001年   70篇
  2000年   30篇
  1999年   79篇
  1998年   75篇
  1997年   60篇
  1996年   56篇
  1995年   49篇
  1994年   27篇
  1993年   38篇
  1992年   26篇
  1991年   23篇
  1990年   14篇
  1989年   8篇
  1988年   12篇
  1987年   8篇
  1986年   7篇
  1985年   7篇
  1984年   15篇
  1983年   14篇
  1982年   7篇
  1981年   8篇
  1980年   7篇
  1979年   6篇
  1978年   7篇
  1977年   6篇
  1974年   7篇
  1968年   5篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
31.
Myxoid leiomyosarcoma of the ovary: Analysis of three cases   总被引:2,自引:0,他引:2  
The first three cases of myxoid leiomyosarcoma occurring in the ovary are reported. Two cases in stage III were found in postmenopausal patients and a further case was found in stage I in a 32-year-old. All masses were large and gelatinous with cystic change, necrosis, and hemorrhage, but both uteri and ligaments and contralateral adnexa appeared normal. Microscopically, the tumors showed a predominantly reticular meshwork of elongated cells surrounded by abundant basophilic material. While electron microscopy proved inconclusive due to nondifferentiation, the use of monoclonal antibodies against smooth muscle actin demonstrated a smooth muscle type of differentiation. The differential diagnosis of this rare ovarian condition includes other myxoid ovarian lesions, such as ovarian edema, myxoma, endodermal sinus tumors, and the sarcomatous component of malignant mixed müllerian tumor and carcinosarcoma, as well as lymphovascular tumors. Since mitotic count due to decreased cellular density is unusually low in myxoid leiomyosarcoma, capsular rupture and clinical stage seem to be more reliable prognostic markers. The highly aggressive behavior of myxoid leiomyosarcoma parallels that of typical ovarian leiomyosarcoma. Two of the three patients in this series died of tumor at 13 and 24 months after diagnosis; the other patient is free of disease at 3 years after diagnosis.  相似文献   
32.
This is the first application of flow cytometry for the detection of lamina propria plasma cells and their intracellular immunoglobulins in patients with inflammatory bowel disease compared to healthy controls. The study has been focused on the distribution of IgA, IgG, IgM and the four IgG subclasses. Plasma cells were detected as high CD38 positive cells. For fixation and permeabilisation a single step reagent, Ortho Permeafix®, was used.

By flow cytometry, in patients with inflammatory bowel disease compared to healthy controls, a higher percentage of IgG+ cells can be observed, in Crohn's disease also a higher percentage of IgM+ cells. Regarding the IgG subclass distribution, patients with Crohn's disease show an increase in IgG2+ cells, patients with ulcerative colitis an increase in IgG1+ and IgG3+ cells. These results do agree with and expand the results of earlier immunohistochemical and functional studies, which are favoured today. For the determination of lymphocyte subset proportions and the detection of intracellular antigens, flow cytometry provides a useful alternative to well-established immunohistochemical methods. By analysing a larger number of cells, this method is more reproducible and less prone to interobserver variations than immunohistochemistry, which needs the pre-selection of a mucosal area, the microscopic scoring of a limited number of cells and the circumvention of high background staining. The optimized flow cytometric protocol used in this study might be a promising tool for further investigations of various purposes.  相似文献   

33.
Changes in the activity of glycogen synthase a and related kinases (phosphatidylinositol-3-kinase, protein kinase B, p44/42 MAP kinases and p70s6 kinase) evoked by GLP-1 in human myocytes from normal subjects were recently implied in the effect of this hormone upon D-glucose transport and glycogen synthesis in the same cells. The major aims of the present study were i) to investigate the possible extension of this knowledge to myocytes obtained from type 2 diabetic patients, ii) to compare in these patients the response to GLP-1, insulin or the structurally related GLP-1 peptides, exendin (1-39)amide and exendin(9-39)amide, and iii) to explore possible differences in the responsiveness to these agents between normal and diabetic subjects. Apart from the much higher basal PI3K activity and impaired response to insulin of p44/42 MAP kinases in the diabetic patients, the changes in enzyme activity caused by either hormone or peptide, although not identical, were essentially comparable. Nevertheless, significant differences in glucose transport and metabolism parameters were observed in the diabetic patients vs. normal subjects: in the diabetic patients, basal 2-deoxy-glucose uptake and glycogen synthase a activity were lower, accompanied by a similar increasing effect of GLP-1 or insulin; yet, the basal value for glycogen synthesis was higher, coinciding with a lesser relative increment in response to GLP-1 or insulin.  相似文献   
34.
High-risk combinations of recipient and graft characteristics are poorly defined for liver retransplantation (reLT) in the current era. We aimed to develop a risk model for survival after reLT using data from the European Liver Transplantation Registry, followed by internal and external validation. From 2006 to 2016, 85 067 liver transplants were recorded, including 5581 reLTs (6.6%). The final model included seven predictors of graft survival: recipient age, model for end-stage liver disease score, indication for reLT, recipient hospitalization, time between primary liver transplantation and reLT, donor age, and cold ischemia time. By assigning points to each variable in proportion to their hazard ratio, a simplified risk score was created ranging 0–10. Low-risk (0–3), medium-risk (4–5), and high-risk (6–10) groups were identified with significantly different 5-year survival rates ranging 56.9% (95% CI 52.8–60.7%), 46.3% (95% CI 41.1–51.4%), and 32.1% (95% CI 23.5–41.0%), respectively (< 0.001). External validation showed that the expected survival rates were closely aligned with the observed mortality probabilities. The Retransplantation Risk Score identifies high-risk combinations of recipient- and graft-related factors prognostic for long-term graft survival after reLT. This tool may serve as a guidance for clinical decision-making on liver acceptance for reLT.  相似文献   
35.
36.
37.
38.
Zusammenfassung Nach Darlegung technischer und ballistischer Einzelheiten über Handfeuerwaffen und eine klinische Einleitung wird über 20 eigene Fälle mit Schädelschußverletzungen berichtet. 16 Verletzungen gingen mit direkter Gehirnbeteiligung einher, 12 von denen verstarben. Es wird auf die Wichtigkeit der Kenntnis der Tatwaffen und des Schußkanalverlaufs im Röntgenbild verwiesen, und die besondere Bedeutung der Bewußtseinslage, der neurologischen Symptomatik und der Schocksituation zur prognostischen Bewertung dieser Verletzungen herausgestellt.
Summary After setting out technical and ballistic details of small arms and after a clinical introduction, a series of 20 personal cases with gun-shot wounds of the head are described. Sixteen patients had direct involvement of the brain, of whom 12 died. The importance of a knowledge of the weapon used and of the course of the missile as seen in the radiographs is referred to. It is demonstrated that in these patients the level of consciousness, the neurological symptoms and the degree of shock are of especial importance in assessing prognosis.

Resumen Después de un breve resumen de los detalles técnicos y balísticos de armas de fuego y tras una introduction clínica se analiza una serie de 20 casos personales de heridas craneales por arma de fuego. De 16 enfermos que tuvieron lesiones cerebrales 12 fallecieron. El autor insiste sobre la importancia del conocimiento del arma utilizada, así como del trayecto de la bala visto en las radiografías. En estos enfermos el nivel de conciencia, los signos neurológicos y el grado de shock tienen una gran importancia para el pronóstico.

Résumé Après un bref rappel des détails techniques et ballistiques des armes légères, et après une introduction clinique, une série de 20 cas personnels de blessures cranielles par coup de fusil est rapportée. Sur 16 malades qui ont eu des lésions cérébrales: 12 sont décédés. L'auteur insiste sur l'importance de la connaissance de l'arme utilisée et du trajet de la balle vu sur les clichés. Chez ces malades, le niveau de conscience, les signes neurologiques et le degré du choc ont une grande importance dans le pronostic.

Riassunto Vengono discussi venti casi di ferite craniche da arma da fuoco, 16 dei quali avevano una compromissione cerebrale. Di essi 12 sono morti. Viene praticamente discussa l'importanza della conoscenza della forza di penetrazione della pallottola nei radiogrammi e della localizzazione del canale di entrata e di uscita e della situazione neurologica e dello stato di shock per la prognosi di questi feriti.
  相似文献   
39.
Summary The influence of respiratory and metabolic acid-base alterations on the myocardial sensitivity to catecholamines was studied in the isolated rat atria. The ability of noradrenaline for increasing the atrial rate was enhanced during alkalosis and conversely, it was decreased by acidosis. These changes in sensitivity shifted the concentration-effect curve for noradrenaline to the right by about 0.5 log unit when the pH was lowered from 7.60 to 7.00. No changes in the maximum attainable response were detected. Essentially the same shifts of the concentration-effect curves were obtained with changes in pH brought about by altering the pCO2 or at constant pCO2. The decrease in the pH produced a similar shift to the right of the concentration-effect curve for isoprenaline, after the extraneuronal uptake inhibition by hydrocortisone and also in atria tissue with low content of endogenous noradrenaline (reserpine-pretreated and newborn rats). The ability of isoprenaline for increasing cyclic AMP levels in atrial tissue was also enhanced by alkalosis and decreased by acidosis. However, the shift to the right of the concentration-effect curve for cyclic AMP induced by the decrease in the pH was greater than the shift detected in the chronotropic-effect curve. In addition a decrease in the maximum increment of cyclic AMP was detected under acidosis, in spite of equal maximal chronotropic response.Our results support the hypothesis that the alterations in the sensitivity to catecholamines induced by the changes in pH are not due to a release of endogenous noradrenaline nor to alterations of the mechanisms which remove catecholamines from the biophase. The fact that cyclic AMP response to catecholamines was also reduced by acidosis strongly suggests that the mechanism(s) involved is located in the earlier steps of the events leading to the chronotropic effect of the -agonists.  相似文献   
40.
Alcohol and Sober Mood State in Female Social Drinkers   总被引:1,自引:0,他引:1  
The goals of the present study were to measure the relationship between alcohol consumption in 93 female social drinkers and their cognitive functioning and mood in the sober state, and to investigate the possible causal effects of alcohol consumption on these variables. In the first test session, a limited relationship was seen between previous alcohol consumption and sober cognitive performance. A strong relationship was found between alcohol consumption and self-reported depression and anger in the sober state. Either a prolonged reduction in alcohol consumption or a prolonged maintenance of alcohol consumption was undertaken by random subsets of the original sample. In the second test session 6 weeks later, women who had been randomly selected to reduce their alcohol intake showed decreases in depression, anger, and mental confusion when they were sober, relative to women who maintained or increased their alcohol consumption over the same period of time. We found no changes in cognitive performance in these groups. We concluded that the simplest explanation of the findings is that relatively low levels of alcohol consumption produce substantial increases in depression and anger in the sober state in female social drinkers. The value of considering alcohol consumption as a continuous variable rather than a dichotomous variable with "safe" and "unsafe" zones was 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