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   5426篇
  免费   272篇
  国内免费   81篇
耳鼻咽喉   154篇
儿科学   170篇
妇产科学   156篇
基础医学   547篇
口腔科学   188篇
临床医学   494篇
内科学   998篇
皮肤病学   120篇
神经病学   278篇
特种医学   234篇
外国民族医学   2篇
外科学   877篇
综合类   307篇
现状与发展   1篇
一般理论   1篇
预防医学   377篇
眼科学   116篇
药学   352篇
  2篇
中国医学   101篇
肿瘤学   304篇
  2023年   50篇
  2022年   115篇
  2021年   172篇
  2020年   88篇
  2019年   114篇
  2018年   145篇
  2017年   126篇
  2016年   132篇
  2015年   158篇
  2014年   193篇
  2013年   212篇
  2012年   348篇
  2011年   350篇
  2010年   207篇
  2009年   132篇
  2008年   226篇
  2007年   290篇
  2006年   269篇
  2005年   305篇
  2004年   208篇
  2003年   216篇
  2002年   233篇
  2001年   158篇
  2000年   179篇
  1999年   165篇
  1998年   45篇
  1997年   40篇
  1996年   36篇
  1995年   46篇
  1994年   33篇
  1993年   14篇
  1992年   82篇
  1991年   70篇
  1990年   62篇
  1989年   51篇
  1988年   41篇
  1987年   47篇
  1986年   53篇
  1985年   43篇
  1984年   30篇
  1983年   21篇
  1979年   20篇
  1975年   14篇
  1974年   27篇
  1973年   18篇
  1971年   21篇
  1970年   25篇
  1969年   16篇
  1968年   13篇
  1967年   13篇
排序方式: 共有5779条查询结果,搜索用时 15 毫秒
11.
12.
Summary.  In this work we present evidence that the homologous peptides IHSMNSTIL and IHSMNSSIL derived from L1 HPV-16 and 18 proteins respectively, and with high specificity for the allele HLA-B*3901, according with an algorithm prediction program, induced T cell stimulation in patients with advanced cervical cancer positive for HPV-16 or 18 infection and for the HLA-B*3901 allele. Interestingly, T lymphocytes derived from a patient with HPV-18 infection and stimulated with the peptide IHSMNSTIL were capable to kill a cervical cancer cell line named Rova, derived from the tumor of the same patient. In addition, the cytotoxic activity was strongly increased when this cell line was previously treated with hrIFN-γ. These results suggest that the CTL immune response to L1 HPV-16 and 18 protein derived epitopes is maintained in patients with advanced cervical cancer within specific alleles, and opens the possibility that homologous epitopes may be used in the generation of prophylactic vaccines for cervical tumors bearing different HPV-types. Received March 4, 2002; accepted May 20, 2002  相似文献   
13.
Vaccinia virus propagated in rotated cultures of RK13 cells was purified by sucrose density gradient zonal centrifugation. The purified virus was dissociated with sodium dodecyl sulfate end its protein composition analyzed by polyacrylamide gel electrophoresis. The protein composition of the virion envelope, isolated by the non-ionic detergent Nonidet P-40, was also determined.  相似文献   
14.
Many data suggest involvement of inflammation in neurodegeneration. However, the exact mechanisms of this cooperation are poorly understood. We have previously shown that induction of inflammatory reaction, both before and after injury of the striatum, affects regeneration of dopaminergic neurons. In the present research we studied the role of inflammatory reaction in non-injured striatum. We used myelin oligodendrocyte glycoprotein (MOG) 35-55 in complete Freund's adjuvant (CFA) to elicit experimental autoimmune encephalomyelitis (EAE) mice model. As determined by HPLC, striatal dopamine (DA) and serotonin levels in mice treated with either MOG 35-55 in CFA or CFA alone were significantly higher compared to vehicle-treated controls on 13th day after induction. The ratio of homovanilic acid/dopamine (HVA/DA) and 3, 4 dihydroxyphenylacetic acid/dopamine (DOPAC/DA) were significantly lower in the MOG and CFA groups on 13th day, indicating decreased DA metabolism. Noradrenaline (NA) concentration did not differ between groups. Moreover, the striatal mRNA IL-1beta and TNF-alpha levels were elevated during induction phase of EAE in both groups, as determined by RT-PCR. Our data indicate regulatory connection between dopaminergic and immune systems.  相似文献   
15.
Inositol is an essential precursor for the formation of glycosyl-phosphatidylinositol (GPI)-anchors found in the majority of surface molecules in trypanosomatids, in addition to its requirement for phoshatidylinositol signal transduction pathways. In Leishmania donovani, high-affinity inositol transport is catalyzed by the active myo-inositol/H+ transporter MIT, which is driven by a proton gradient across the parasite membrane. We have characterized the substrate specificity and pharmacology of L. donovani MIT in vitro and in promastigote cultures. High substrate specificity of myo-inositol transport was shown in competition studies with 14 different monosaccharides and MIT function was unaffected by the structurally similar pentose sugars or hexoses. L-Fucose and D-xylose, both inhibitors of the Na+-dependent inositol transport system in the human host, did not affect MIT transport function in the parasite. Competition studies with eight different inositol isomers revealed that proton bonds between the C-2, C-3 and C-5 hydroxyl groups of myo-inositol and the transporter protein played a critical role for substrate recognition, and the C-3 hydroxyl oxygen appears to act as an electron donor to form an H-bond with a positive charge of the MIT permease. The cytotoxic inositol analogue 3-fluoro-myo-inositol was recognized by MIT with similar affinity as myo-inositol and showed an IC50 value of 42 +/- 8 microM in L. donovani cultures. Finally, substrate affinities of MIT revealed apparent Km values of 84 +/- 8 microM for myo-inositol and 5.4 +/- 0.9 nM for H+, equal pH 8.27 + 0.08, suggesting that the L. donovani myo-inositol/H+ symporter is fully activated at physiological pH in the sandfly midgut or macrophage phagolysosome. We conclude that Leishmania MIT constitutes an attractive target for delivery of cytotoxic inositol analogues and differs significantly from the sodium-coupled myo-inositol transport system of the human host.  相似文献   
16.
A combined analysis procedure was used to study auditory, sensory evoked potentials (EPs) and event-related potentials (ERPs) in human subjects. Single sweep and averaged data were analysed in the time and frequency domains. Recognised peaks, seen in the averaged data, were related to specific poststimulus changes within conventional delta, theta and alpha frequency bands. The potential advantages of single sweep analysis, selective averaging and frequency domain analysis are discussed. The importance of studying prestimulus EEG activity in order to understand poststimulus changes is emphasised in relation to proposed hypotheses concerning brain dynamics and evoked response mechanisms. Specific frequency changes, elicited by target tones in auditory "odd ball" experiments, are described and contrasted to changes seen in EPs and nontarget ERPs. Our findings suggest that the P300 change of averaged data is the later consequence of poststimulus frequency changes which can be detected within the first 100 msec. The practical implications of our findings are briefly discussed.  相似文献   
17.
Many people with heel pain in the general population are often diagnosed with plantar calcaneal spurs (PCS). The aim of this study was to evaluate the radiological and demographic characteristics of PCS patients and to compare the differences with the control group. In 2018, 420 patients with weightbearing lateral ankle X-ray images were included in the study. The patients were divided into 2 groups as PCS group and control group. Groups were compared age and age group (20-29, 30-39, 40-49, 50-59, 60-69, 70 and over) weight, height, body mass index (<25, 25-30, >30), chronic diseases as demographically and were also compared radiologically as calcaneal inclination angle (CIA), lateral talocalcaneal angle (LTCA), Bohler angle and Gissane angle. A statistically significant relationship was found between gender and PCS. Plantar calcaneal spur is more common in females than in males (X2:8.101, p < .03). PCS was less common in patients with BMI <25 and 25-29.9, whereas PCS is more common in patients with BMI >30 (X2:7.698, p < .021). Although the CIA angle was within normal limits in both groups, it was significantly lower in patients with PCS than in the control group(p < .05). There was no statistically significant difference between the 2 groups in terms of age, chronic disease, LTCA, Bohler angle, Gissane angle. Female gender and obesity are among the risk factors for PCS formation. CIA may have an important role in PCS formation. In order to clarify the etiology and pathophysiology of PCS, further studies with radiological features are needed.  相似文献   
18.
In this study we report that the use of a heterologous radioimmunoassay (RIA) is valid for the detection of insulin-like growth factor-I (IGF-I) levels in plasma of a variety of fish species. Parallelism between standard curves and plasma dilutions were observed and the standard curve obtained with mammalian IGF-I presented the same characteristics as that obtained with coho salmon recombinant IGF-I.The RIA was biologically validated since total plasma IGF-I values were significantly modified by different experimental conditions. Hyperinsulinemia induced either by arginine or insulin injection was accompanied by increases in IGF-I plasma levels in brown trout (Salmo trutta). In contrast, parallel decreases in insulin and IGF-I circulating levels were observed after 45 days of fasting and 20 days after a single streptozotocin injection. Administration of arginine in fasted fish led to a relative increase in insulin and IGF-I plasma concentrations, while arginine injection in fish previously treated with streptozotocin increased IGF-I levels only. The above data suggest that insulin, together with other factors, may act to increase the levels of IGF-I in plasma.  相似文献   
19.
20.
BACKGROUND: Although adrenal insufficiency may not occur with moderate hypotension, it does occur with severe hemorrhage. Since hepatocellular function is depressed following severe hemorrhage, it remains unknown whether the liver plays any role in regulating adrenal function after trauma and hemorrhagic shock. HYPOTHESIS: Hepatic 11beta-hydroxysteroid dehydrogenase (11beta-HSD), a microsomal enzyme responsible for the degradation of bioactive corticosterone, plays a major role in the development of adrenal insufficiency following trauma and severe hemorrhage. DESIGN, INTERVENTIONS, AND MAIN OUTCOME MEASURES: Male rats underwent laparotomy to induce trauma before hemorrhage. They were then bled to and maintained at a blood pressure of 40 mm Hg until 40% of the maximal bleed-out volume was returned in the form of Ringer lactate. The rats were then resuscitated with 4 times the volume of maximal bleed-out with Ringer lactate during a 60-minute period. Plasma levels of corticosterone and corticotropin were measured at various intervals. In additional groups, corticotropin-induced corticosterone release, adrenal contents of corticosterone and cyclic adenosine monophosphate (cAMP), hepatic 11beta-HSD activity, and plasma levels of corticosterone-binding globulin were determined at 1.5 hours after resuscitation. Moreover, a model of moderate hypotension (blood pressure, 80 mm Hg) was used to determine whether adrenal function is depressed under such conditions. RESULTS: At the time of maximal bleed-out, plasma corticosterone and corticotropin levels increased by 245% (P<.001) and 293% (P<.001), respectively. Despite corticotropin levels being similar to those of the animals undergoing sham operation after resuscitation, corticosterone levels in hemorrhaged animals remained elevated up to 4 hours after resuscitation (by 158%-207%; P<.001). In addition, corticotropin-induced corticosterone release decreased by 78% at 1.5 hours after resuscitation (P = .009). In contrast, moderate hypotension did not reduce corticotropin-induced corticosterone release. Adrenal corticosterone content and cAMP levels (i.e., the second messenger of corticotropin action) decreased by 55% (P<.001) and 25% (P = .03), respectively. Hepatic 11beta-HSD activity decreased significantly at 1.5 hours after resuscitation (P<.001). CONCLUSIONS: Sustained increase in plasma corticosterone levels following hemorrhage and resuscitation may be, in part, due to the decreased hepatic 11beta-HSD activity. The high level of corticosterone negatively regulates corticotropin release, further reducing adrenal responsiveness to corticotropin stimulation. Thus, the liver appears to play an important role in regulating adrenal function following trauma and severe hemorrhage.  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