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   15159篇
  免费   1025篇
  国内免费   75篇
耳鼻咽喉   193篇
儿科学   259篇
妇产科学   294篇
基础医学   2037篇
口腔科学   332篇
临床医学   1358篇
内科学   3311篇
皮肤病学   263篇
神经病学   1673篇
特种医学   817篇
外科学   2598篇
综合类   57篇
一般理论   2篇
预防医学   834篇
眼科学   313篇
药学   874篇
中国医学   14篇
肿瘤学   1030篇
  2023年   138篇
  2022年   180篇
  2021年   347篇
  2020年   285篇
  2019年   363篇
  2018年   401篇
  2017年   369篇
  2016年   419篇
  2015年   468篇
  2014年   543篇
  2013年   793篇
  2012年   1127篇
  2011年   1175篇
  2010年   643篇
  2009年   619篇
  2008年   1063篇
  2007年   1035篇
  2006年   972篇
  2005年   879篇
  2004年   761篇
  2003年   720篇
  2002年   660篇
  2001年   196篇
  2000年   145篇
  1999年   153篇
  1998年   141篇
  1997年   113篇
  1996年   95篇
  1995年   80篇
  1994年   79篇
  1993年   89篇
  1992年   106篇
  1991年   90篇
  1990年   75篇
  1989年   82篇
  1988年   72篇
  1987年   70篇
  1986年   64篇
  1985年   67篇
  1984年   53篇
  1983年   64篇
  1982年   45篇
  1981年   51篇
  1980年   32篇
  1979年   29篇
  1978年   43篇
  1977年   33篇
  1976年   24篇
  1975年   29篇
  1974年   39篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
21.
AIM: The aim of this study was to analyse possible intra- and postoperative complications and long-term results in combined orthodontic-orthognathic treatment of mentally handicapped patients compared with a control group of patients without handicap. PATIENTS AND METHODS: A group of 20 mentally handicapped patients (male = 7, female = 13) and of 102 non-handicapped patients (male = 36, female = 66) were evaluated retrospectively. The results of the two point-discrimination sensory test and the cephalometric findings of both groups were assessed. Complications during and after the operation, the results of nerve function tests and relapse rates were reported. The statistical analysis was carried out using binary logistical regression analysis with adjustment according to the diagnosis and the type of operation (p < 0.05) RESULTS: No significant differences could be found between the mentally handicapped and the non-handicapped patients. Only the nerve function test immediately postoperatively revealed differences between the two patient groups. The relapse rate in mentally handicapped patients was similar to non-handicapped patients. Forty-seven months after the operation, relapse (change in the ANB angle of more than 0.5 degrees ) was observed in four patients only (handicapped patients). CONCLUSION: Orthognathic surgical procedures in mentally handicapped patients can be carried out with a similarly high success rate as in mentally healthy patients.  相似文献   
22.
Fragestellung: Die Karzinomassoziierte Retinopathie (CAR) stellt ein seltenes paraneoplastisches Syndrom dar, das bislang am h?ufigsten bei kleinzelligen Bronchialkarzinomen beschrieben wurde. Wir berichten über 3 Patientinnen mit CAR in Gegenwart eines Mammakarzinoms bzw. eines Karzinoids der Cervix uteri. Patienten und Methode: Es wurden biomikroskopische, perimetrische, angiographische und elektrophysiologische Befunde erhoben. Au?erdem erfolgte eine Testung der Immunreaktivit?t der Seren an humaner Retina. Ergebnisse: Die Befunde umfa?ten ringf?rmige Gesichtsfelddefekte mit statokinetischer Dissoziation und eine pathologische St?bchen- und Zapfenantwort im ERG. Bei 1 Patientin wurde immunhistochemisch eine Reaktion im Bereich der Photorezeptorinnensegmente, der ?u?eren K?rnerschicht sowie der ?u?eren plexiformen Schicht bei fehlendem Nachweis von Antik?rpern gegen Recoverin gefunden. Diskussion: Neben dem kleinzelligen Bronchialkarzinom k?nnen auch andere Prim?rtumoren mit einer CAR vergesellschaftet sein. Der Nachweis von retinalen Autoantik?rpern unterstützt die Annahme einer tumorinduzierten Immunantwort aufgrund der Expression identischer Epitope durch die Tumorzellen. Dabei kommen offensichtlich verschiedene retinale Proteine als Autoantigene in Betracht.   相似文献   
23.
There is evidence that the distal intestine participates in the regulation of gastric motor and secretory function. It was the aim of this study to examine in greater detail the effects of ileal nutrient exposure on human gastric acid secretion and to investigate potential intermediary mechanisms. Twelve normal subjects were intubated with an oroileal multilumen tube assembly for gastric, duodenal, and ileal perfusion of marker and test solutions, aspiration, and intestinal manometry. We studied ileal effects on gastric acid output in the unstimulated, interdigestive state (during early phase II,N=6), and during endogenous stimulation by intraduodenal essential amino acid perfusion,N=6) and on release of candidate humoral mediators, peptide YY (PYY) and glucagonlike peptide-1 (GLP-1), both known inhibitors of human gastric acid secretion. Compared with ileal saline perfusion, ileal carbohydrate (total caloric load: 60 kcal) decreased interdigestive gastric acid output by 64% (P<0.01), and endogenously stimulated output by 68%, respectively (P<0.005). Under all experimental conditions, ileal carbohydrate increased plasma GLP-1 by 80–100% (allP<0.005). Ileal lipid perfusion had similar inhibitory effects on gastric acid output and stimulatory effects on GLP-1 release as had ileal carbohydrate. By contrast, ileal perfusion with peptone had no or only weak effects on either acid output or plasma GLP-1. Plasma PYY concentrations and suppression of gastric secretion in response to ileal perfusions were not correlated. In humans, both interdigestive and endogenously stimulated gastric acid output are inhibited in response to intraileal carbohydrate or lipids, but not protein, Decreased acid output is associated with release of GLP-1, but not PYY. These findings support the hypothesis that the distal small intestine may participate in the late postprandial inhibitory regulation of gastric secretory function in humans and that GLP-1 may be an intermediary factor.  相似文献   
24.
25.
Background: Neuropathic pain in spinal cord injury is a common challenging therapeutic condition. The current study examines the analgesic effect of the sodium channel blocker lidocaine on neuropathic pain in patients with spinal cord injury and the predictive role of concomitant evoked pain on pain relief with lidocaine.

Methods: Twenty-four spinal cord injury patients with neuropathic pain at or below the level of injury were randomized and completed a double-blind crossover trial of 5 mg/kg lidocaine and placebo infused over 30 min. Twelve patients reported evoked pain, and 12 patients had no evoked pain. Spontaneous and evoked pains were assessed using a visual analog scale and quantitative sensory testing.

Results: Lidocaine significantly reduced spontaneous pain in all patients (P < 0.01) and in each of the two groups with (P < 0.01) and without (P = 0.048) evoked pain, with no difference in number of responders (pain reduction >= 33%) between the patients with (n = 6) and without (n = 5) evoked pain. Lidocaine significantly relieved both at-level and below-level neuropathic pain and decreased brush-evoked dysesthesia but not cold allodynia, pinprick hyperalgesia, or pain evoked by repetitive pinprick.  相似文献   

26.
Background: Volatile anesthetics are commonly used for general anesthesia. However, these can induce profound cardiovascular alterations. Xenon is a noble gas with potent anesthetic and analgesic properties. However, it is uncertain whether xenon alters myocardial function. The aim of this study was therefore to investigate left ventricular function during anesthesia with xenon compared with isoflurane.

Methods: The authors performed a randomized multicenter trial to compare xenon with isoflurane with respect to cardiovascular stability and adverse effects in patients without cardiac diseases scheduled for elective surgery. Two hundred fifty-nine patients were enrolled in this trial, of which 252 completed the study according to the protocol. Patients were anesthetized with xenon or isoflurane, respectively. Before administration of the study drugs and at four time points, the effects of both anesthetics on left ventricular function were investigated using transesophageal echocardiography.

Results: Global hemodynamic parameters were significantly altered using isoflurane (P < 0.05 vs. baseline), whereas xenon only decreased heart rate (P < 0.05 vs. baseline). In contrast to xenon, left ventricular end-systolic wall stress decreased significantly in the isoflurane group (P < 0.05 vs. baseline). Velocity of circumferential fiber shortening was decreased significantly in the xenon group but showed a more pronounced reduction during isoflurane administration (P < 0.05 vs. baseline). The contractile index (difference between expected and actually measured velocity of circumferential fiber shortening) as an independent parameter for left ventricular function was significantly decreased after isoflurane (P < 0.0001) but unchanged using xenon.  相似文献   

27.
OBJECTIVE: Enlargement of the ascending aorta is often combined with valvular, coronary, or other cardiac diseases. Reduction aortoplasty can be an optional therapy; however, indications regarding the diameter of aorta, the history of dilatation (poststenosis, bicuspid aortic valve), or the intraoperative management (wall excision, reduction suture, external reinforcement) are not established. METHODS: In a retrospective study between 1997 and 2005, we investigated 531 patients operated for aneurysm or ectasia of the ascending aorta (diameter: 45-76mm). Of these, in 50 patients, size-reducing ascending aortoplasty was performed. External reinforcement with a non-coated dacron prosthesis was added in order to stabilize the aortic wall. RESULTS: Aortoplasty was associated with aortic valve replacement in 47 cases (35 mechanical vs 12 biological), subvalvular myectomy in 29 cases, and CABG in 13 cases. The procedure was performed with low hospital mortality (2%) and a low postoperative morbidity. Computertomographic and echocardiographic diameters were significantly smaller after reduction (55.8+/-9mm down to 40.51+/-6.2mm (CT), p<0.002; 54.1+/-6.7mm preoperatively down to 38.7+/-7.1mm (echocardiography), p<0.002), with stable performance in long-term follow-up (mean follow-up time: 70 months). CONCLUSIONS: As demonstrated in this study, size reduction of the ascending aorta using aortoplasty with external reinforcement is a safe procedure with excellent long-term results. It is a therapeutic option in modern aortic surgery in patients with poststenotic dilatation of the aorta without impairment of the sinotubular junction of the aortic valve and root.  相似文献   
28.
Some osteopetrotic mutations lead to low resorption, increased numbers of osteoclasts, and increased bone formation, whereas other osteopetrotic mutations lead to low resorption, low numbers of osteoclasts, and decreased bone formation. Elaborating on these findings, we discuss the possibility that osteoclasts are the source of anabolic signals for osteoblasts. In normal healthy individuals, bone formation is coupled to bone resorption in a tight equilibrium. When this delicate balance is disturbed, the net result is pathological situations, such as osteopetrosis or osteoporosis. Human osteopetrosis, caused by mutations in proteins involved in the acidification of the resorption lacuna (ClC-7 or the a3-V-ATPase), is characterized by decreased resorption in face of normal or even increased bone formation. Mouse mutations leading to ablation of osteoclasts (e.g., loss of macrophage-colony stimulating factor [M-CSF] or c-fos) lead to secondary negative effects on bone formation, in contrast to mutations where bone resorption is abrogated with sustained osteoclast numbers, such as the c-src mice. These data indicate a central role for osteoclasts, and not necessarily their resorptive activity, in the control of bone formation. In this review, we consider the balance between bone resorption and bone formation, reviewing novel data that have shown that this principle is more complex than originally thought. We highlight the distinct possibility that osteoclast function can be divided into two more or less separate functions, namely bone resorption and stimulation of bone formation. Finally, we describe the likely possibility that bone resorption can be attenuated pharmacologically without the undesirable reduction in bone formation.  相似文献   
29.
OBJECTIVE: Recent studies have demonstrated that transplanted bone marrow-derived stem cells (BMCs) possess a broad differentiation potential and are able to form new cardiomyocytes. However, the identity of BMCs as true cardiomyocytes is still ambiguous. Therefore, we investigated the fate of transplanted fluorescence labeled BMCs and cardiomyocytes in co-culture. METHODS: For cell tracking we used two different fluorescent probes, Vybrant/DiO and Vybrant/DiI. BMCs were taken from human sternal marrow, purified using a Ficoll-gradient-centrifugation, treated with 5-azacytidine and stained with Vybrant/DiO. Furthermore, isolated spontaneous beating cardiomyocytes of neonatal rats (CM) were labeled with Vybrant/DiI. Thereafter, the BMCs were transplanted into CM-cultures and investigated on day 1, 4, 7, 14 and 28 using two-color fluorescence phenotyping by laser-scanning-cytometry (LSC). Two-color positive cells were harvested by patch-clamp technique and beta-MHC mRNA expression was analyzed by single-cell PCR. RESULTS: Two different morphological phenotypes were observed by LSC. First, isolated DiO labeled BMCs without contact or with direct cell contact to DiI labeled CMs. Second, some BMCs and CMs were double positive for DiO/DiI spontaneously forming hybrids. This population increased by 18% from day 1 to 4 and decreased only slightly until day 28. Additionally, few two-color positive cell formations expressed both human and rat specific beta-MHC mRNA as well as only human beta-MHC mRNA indicating that cell-fusion and transdifferentiation has occurred. CONCLUSION: These observations provide in vitro evidence for spontaneous cell fusion and transdifferentiation of BMCs in co-culture, raising the possibility that the observed phenomenons may contribute to development or maintenance of these cell types.  相似文献   
30.
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