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   1392篇
  免费   80篇
耳鼻咽喉   27篇
儿科学   41篇
妇产科学   15篇
基础医学   182篇
口腔科学   34篇
临床医学   127篇
内科学   407篇
皮肤病学   34篇
神经病学   80篇
特种医学   35篇
外科学   114篇
综合类   3篇
预防医学   115篇
眼科学   34篇
药学   105篇
中国医学   1篇
肿瘤学   118篇
  2021年   12篇
  2020年   11篇
  2019年   13篇
  2018年   15篇
  2017年   11篇
  2016年   20篇
  2015年   28篇
  2014年   15篇
  2013年   53篇
  2012年   57篇
  2011年   70篇
  2010年   29篇
  2009年   32篇
  2008年   66篇
  2007年   55篇
  2006年   59篇
  2005年   81篇
  2004年   73篇
  2003年   75篇
  2002年   57篇
  2001年   48篇
  2000年   36篇
  1999年   39篇
  1998年   21篇
  1997年   16篇
  1995年   13篇
  1992年   10篇
  1991年   18篇
  1990年   10篇
  1989年   13篇
  1987年   12篇
  1986年   10篇
  1985年   11篇
  1984年   18篇
  1981年   10篇
  1980年   11篇
  1979年   29篇
  1978年   13篇
  1977年   10篇
  1976年   11篇
  1975年   19篇
  1974年   22篇
  1973年   21篇
  1972年   20篇
  1971年   14篇
  1970年   20篇
  1969年   23篇
  1968年   20篇
  1967年   12篇
  1965年   16篇
排序方式: 共有1472条查询结果,搜索用时 230 毫秒
1.
Synovialsarkome sind mitunter schwierig von anderen Spindelzellsarkomen zu unterscheiden. In diesen Fällen kann der Nachweis einer t(X;18) Translokation unter Verwendung der FISH und RT-PCR helfen. Die vorliegende Arbeit wurde unter der Fragestellung durchgeführt, ob bei Synovialsarkom-verdächtigen Tumoren der simultane Einsatz beider Methoden zum Translokationsnachweis erforderlich ist oder ob eine der Methoden ausreicht.In die Studie wurde Paraffin-eingebettetes Tumorgewebe von 53 Patienten einbezogen, bei denen nach Lichtmikroskopie und Immunhistochemie der Verdacht auf das Vorliegen eines Synovialsarkoms bestand. Es erfolgte der Nachweis von t(X;18) mittels FISH und RT-PCR.  相似文献   
2.
BACKGROUND: Past receiver operating characteristic (ROC) studies have demonstrated that single photon emission computed tomography (SPECT) perfusion imaging by use of iterative reconstruction with combined compensation for attenuation, scatter, and detector response leads to higher area under the ROC curve (A(z)) values for detection of coronary artery disease (CAD) in comparison to the use of filtered backprojection (FBP) with no compensations. A new ROC study was conducted to investigate whether this improvement still holds for iterative reconstruction when observers have available all of the imaging information normally presented to clinical interpreters when reading FBP SPECT perfusion slices. METHODS AND RESULTS: A total of 87 patient studies including 50 patients referred for angiography and 37 patients with a lower than 5% likelihood for CAD were included in the ROC study. The images from the two methods were read by 4 cardiology fellows and 3 attending nuclear cardiologists. Presented for the FBP readings were the short-axis, horizontal long-axis, and vertical long-axis slices for both the stress and rest images; cine images of both the stress and rest projection data; cine images of selected cardiac-gated slices; the CEQUAL-generated stress and rest polar maps; and an indication of patient gender. This was compared with reading solely the iterative reconstructed stress slices with combined compensation for attenuation, scatter, and resolution. With A(z) as the criterion, a 2-way analysis of variance showed a significant improvement in detection accuracy for CAD for the 7 observers (P = .018) for iterative reconstruction with combined compensation (A(z) of 0.895 +/- 0.016) over FBP even with the additional imaging information provided to the observers when scoring the FBP slices (A(z) of 0.869 +/- 0.030). When the groups of 3 attending physicians or 4 cardiology fellows were compared separately, the iterative technique was not statistically significantly better; however, the A(z) for each of the 7 observers individually was larger for iterative reconstruction than for FBP. Compared with results from our previous studies, the additional imaging information did increase the diagnostic accuracy of FBP for CAD but not enough to undo the statistically significantly higher diagnostic accuracy of iterative reconstruction with combined compensation. CONCLUSIONS: We have determined through an ROC investigation that included two classes of observers (experienced attending physicians and cardiology fellows in training) that iterative reconstruction with combined compensation provides statistically significantly better detection accuracy (larger A(z)) for CAD than FBP reconstructions even when the FBP studies were read with all of the extra clinical nuclear imaging information normally available.  相似文献   
3.
Changes of the age-specific and age-standardized incidence of malignant neoplasms in the GDR between 1962 and 1980 are investigated. A series of cancer localisation has increased in which case improved diagnostics and increased risk are discussed as causes (cancer of colon and rectum, of the pancreas, the breast and the testicle). The epidemics of bronchial cancer has apparently reached its climax, the admission rates stagnate. Cancer of the stomach and recently also cancer of the gallbladder and the extrahepatic bile ducts decrease in their frequency.  相似文献   
4.
Platelets stored in CLX™ blood bags, under normal blood banking conditions, were studied for up to 7 days to determine if changes ocurred in the levels of membrane glycoproteins (GP) Ib-IX and IIb-IIIa. Radiolabeled monoclonal antibodies (MAB) were used to estimate the number of glycoprotein molecules on the surface membrane of intact platelets. GP IX and GP IIb-IIIa levels remained essentially unaltered during storage. In contrast, the content of GP Ib at day 7 decreased by 45% of the total when fresh. The aggregation response to ristocetin, which requires GP Ib, was also diminished after 7 days. Addition of protease inhibitors, leupeptin and/or aprotinin did not appear to influence the degradation of this glycoprotein. We conclude that storage at 22°C has deleterious effects on the GP Ib content of platelets.  相似文献   
5.
As unilateral nephrectomy (UNX) is associated with enhanced mercuric chloride nephrotoxicity, studies were undertaken to characterize the effects of UNX on the tissue content, urinary excretion, and renal cortical subcellular distribution of mercury in the rat. Animals were studied immediately, 2 days or 14 days following UNX, during separate phases of compensatory renal hypertrophy. As compared to sham surgery controls, mercury content in renal cortex was higher in all UNX groups at 24 hr following injection and in the immediate and 2-day groups at 1 or 3 hr. However, UNX was not associated with any alteration in mercury content within outer or inner medulla, liver, plasma, or red blood cells. Subcellular distribution studies demonstrated that cytosolic mercury was uniformly elevated in all UNX groups at 1, 3, and 24 hr following injection while mercury bound to "metallothionein-like" proteins or free in the cytosol was increased only at 1 or 3 hr. Nuclear, mitochondrial, or microsomal mercury content was elevated in the animals studied immediately or 14 days after UNX at 3 or 24 hr following injection, while animals studied 2 days after UNX demonstrated a nearly uniform increase at 1, 3, and 24 hr. Single-kidney urinary mercury excretion was elevated in all UNX groups while excretion per gram kidney weight was increased only in the animals studied immediately or 2 days after surgery. These studies suggest that all phases of compensatory renal hypertrophy are associated with an enhanced content of mercury within the cell cytoplasm and in critical cellular organelles, which may explain the enhanced nephrotoxicity seen following UNX.  相似文献   
6.
Geometric uncertainties arise during treatment planning and treatment and mean that dose-dependent parameters such as EUD are random variables with a patient specific probability distribution. Treatment planning with highly conformal treatment techniques such as intensity modulated radiation therapy requires new evaluation tools which allow us to estimate this influence of geometrical uncertainties on the probable treatment dose for a planned dose distribution. Monte Carlo simulations of treatment courses with recalculation of the dose according to the daily geometric errors are a gold standard for such an evaluation. Distribution histograms which show the relative frequency of a treatment quality parameter in the treatment simulations can be used to evaluate the potential risks and chances of a planned dose distribution. As treatment simulations with dose recalculation are very time consuming for sufficient statistical accuracy, it is proposed to do treatment simulations in the dose parameter space where the result is mainly determined by the systematic and random component of the geometrical uncertainties. Comparison of the parameter space simulation method with the gold standard for prostate cases and a head and neck case shows good agreement as long as the number of fractions is high enough and the influence of tissue inhomogeneities and surface curvature on the dose is small.  相似文献   
7.
There are a number of difficulties regarding the diagnosis of Barrett's mucosa and the varying grades of neoplasia that may be associated with it. It was therefore the aim of a consensus conference of the "Working Group for Gastroenterological Pathology within the German Society of Pathology" to achieve standardization regarding the following issues: definition and diagnostic criteria for Barrett's mucosa and its discrimination from intestinal metaplasia of the cardia, diagnostic criteria for intraepithelial neoplasia, number of biopsies necessary to establish the diagnosis, significance of additional immunohistochemical and/or molecular biological methods as well as importance of a second opinion in the diagnosis of intraepithelial neoplasia.  相似文献   
8.
Zusammenfassung Bei nicht exakt erfolgender diastolischer arterieller Gegenpulsation kommt es nicht allein zu dem erwünschten Absinken des herzeigenen systolischen Druckes sowie des Spannungszeitindexes. Zusätzlich werden Anteile der Systole durch den Druckvolumenstoß miterfaßt. Die resultierenden Druckänderungen vor allem des LV konnten in drei Abschnitte gegliedert werden.I. Trifft der absteigende Anteil des Gegenimpulses auf das Ende der isometrischen Phase bzw. den Beginn der Austreibungsperiode des linken Ventrikels, so wird der enddiastolische Aortendruck erhöht, die Aortenklappen öffnen sich verspätet, der LV-Druck liegt bei unverändertem LVEDD höher als beim Kontrollschlag, ohne daß immer eine Minderung des Schlagvolumens eintritt. Dieser anscheinende Widerspruch zu den Frank-Starlingschen Gesetzen konnte in der vorliegenden Untersuchungsanordnung nicht eindeutig geklärt werden, weil das normale systolische Durchflußvolumen mit der aufgezwungenen Volumenänderung interferiert und dadurch ein zu hohes Schlagvolumen vorgetäuscht werden kann.II. Fällt der Druckvolumenstoß zeitlich mit dem Maximum der ventrikulären Druckentwicklung zusammen, so nimmt nach den Frank-Starlingschen Gesetzen das Schlagvolumen bei vermehrter ventrikulärer Druckentwicklung ab.III. Erfaßt der Beginn des Gegenimpulses das Ende der ventrikulären Austreibungsphase, so resultiert eine zusätzliche isometrische Kontraktion, die sich der Form des Gegenimpulses angleicht. Die Aortenklappen schließen vorzeitig, und die Austreibungsphase wird verkürzt.Mit 5 TextabbildungenMit Unterstützung der Deutschen Forschungsgemeinschaft.  相似文献   
9.
10.
In cats anesthetized with chloralose-urethane, the central respiratory chemoreceptors were exposed to mock CSF of pH 7.02, 7.20, or 7.57. The right carotid body was simultaneously stimulated by intracarotid injections of 40, 80, or 160 μg sodium cyanide in 200 μl Ringer solution. The left carotid nerve and, in some animals, both vagosympathetic truncs were dissected. It could be demonstrated the the increase in ventilation produced by application of NaCN to the peripheral chemoreceptors is significantly larger at high than at low mock CSF pH (i.e. at low than at high central stimulus intensity). In vagotomized cats the responses of VT and gelai to NaCN similarly depend upon CSF pH; they are somewhat larger, though, than in intact animals. These results are discussed as compared with results reported by different authors. Supported by the Deutsche Forschungsgemeinschaft (Be 477)  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