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   4105篇
  免费   235篇
  国内免费   21篇
耳鼻咽喉   29篇
儿科学   56篇
妇产科学   20篇
基础医学   350篇
口腔科学   104篇
临床医学   361篇
内科学   972篇
皮肤病学   57篇
神经病学   264篇
特种医学   190篇
外科学   957篇
综合类   20篇
预防医学   98篇
眼科学   49篇
药学   374篇
中国医学   7篇
肿瘤学   453篇
  2023年   19篇
  2022年   38篇
  2021年   79篇
  2020年   49篇
  2019年   74篇
  2018年   93篇
  2017年   76篇
  2016年   65篇
  2015年   85篇
  2014年   95篇
  2013年   109篇
  2012年   172篇
  2011年   206篇
  2010年   108篇
  2009年   92篇
  2008年   176篇
  2007年   210篇
  2006年   185篇
  2005年   210篇
  2004年   192篇
  2003年   197篇
  2002年   186篇
  2001年   186篇
  2000年   183篇
  1999年   139篇
  1998年   59篇
  1997年   39篇
  1996年   44篇
  1995年   36篇
  1994年   27篇
  1993年   23篇
  1992年   67篇
  1991年   74篇
  1990年   68篇
  1989年   86篇
  1988年   69篇
  1987年   68篇
  1986年   58篇
  1985年   56篇
  1984年   33篇
  1983年   36篇
  1982年   17篇
  1981年   16篇
  1979年   41篇
  1978年   24篇
  1977年   32篇
  1974年   18篇
  1973年   18篇
  1972年   21篇
  1971年   22篇
排序方式: 共有4361条查询结果,搜索用时 10 毫秒
21.
Isatin (indole-2,3-dione), an endogenous inhibitor of monoamine oxidase (MAO), has several physiological properties for stress and anxiety. We previously identified isatin in the brain of stroke-prone spontaneously hypertensive rats (SHRSP) using gas-chromatography mass spectrometry. This study elucidated the effects of isatin on the ACh and DA levels of brain tissues in rats. Furthermore, we evaluated the effect of isatin on DA levels in a rat model of Parkinson's disease induced by Japanese encephalitis virus. Striatal ACh and DA levels significantly increased at 2 hours after isatin (50-200 mg/kg, i.p.) administration. Perfused through a microdialysis probe, isatin (10(-6)-10(-4) M) also produced a significant and concentration-dependent increase in the ACh and DA concentrations in the perfusate from the rat striatum. Furthermore, urinary isatin concentrations in patients with Parkinson's disease tend to increase according to the severity of disease. Isatin (100 mg/kg, i.p.) significantly increased striatal DA levels in a rat model of Parkinson's disease. These results suggest that urinary isatin may become a diagnostic marker for the clinical severity of Parkinson's disease and that endogenous isatin, a new biological modulator, may play a role in the regulation of the brain levels of ACh by increasing the level of DA under stress.  相似文献   
22.
We examined the effects of granulocyte colony-stimulating factor (G-CSF) on cell-cycling of hematopoietic progenitors in serum-free methylcellulose clonal cultures. Serial observations of the cultures showed hastening of growth of colonies by G-CSF, as determined by evaluating the time for individual colonies of 20 cells to reach 40 cells. G-CSF did not affect the incidence of proliferating cells in each developing colony. Cell-cycle analysis revealed that addition of G-CSF to cultures led to a decrease in the percentage of cells in the G1 phase of the cell-cycle, thereby indicating that G-CSF can modulate the cell-cycle of hematopoietic progenitors mainly by shortening the period of the G1 phase. Tumor necrosis factor alpha (TNF alpha) exerted opposite effects on cell-cycling of hematopoietic progenitors to those seen with G-CSF. G-CSF abolished the inhibitory effects of TNF alpha on the cell-cycling of hematopoietic progenitors. These observations indicate positive and negative regulatory roles of C-CSF and TNF alpha, respectively, and their interactions in the regulation of cell-cycling of hematopoietic progenitors.  相似文献   
23.
In order to study the changes of the psychological status during perioperative period, we performed four different psychological tests, Spielberger's rating scale "The State-Trait Anxiety Inventory (STAI)", Self-rating Depression Scale (SDS), Maudsley Personality Inventory (MPI) and Baum test, in 63 patients who received simple total hysterectomy for myoma of uterus. The anxiety ratings showed a significant decrease postoperatively. On the contrary, the SDS index that expresses the level of depressive mood showed no significant change during perioperative period. Moreover the patients who had shown a tendency of nervousness in MPI kept the high level of the SDS index during perioperative period than the other patients who had not shown a tendency of nervousness in MPI. In Baum test, more than 75% of patients manifested psychologic fragility or lability. These results suggest that depressive mood affects strictly the psychological status in postoperative period more than anxiety. We presume that the depressive mood during perioperative period is responsible for the postoperative psychological disturbance.  相似文献   
24.
25.
26.
The pattern of subchondral bone density has been considered to reflect the stress distribution that occurs under physiologic loading conditions. To determine the force distribution through the wrist joint with Kienb?ck's disease in living subjects, we applied a computed tomography osteoabsorptiometry and investigated the subchondral bone density pattern across the radio-carpal joint of 6 normal subjects and 10 patients suffering from Kienb?ck's disease (Lichtman's stage IIIA, 5 patients; stage IIIB, 5 patients). A single density maximum was found in each scaphoid and lunate fossa in all normal subjects. Among the subjects with Kienb?ck's disease, the current analysis demonstrated that the density maximum area significantly increased in the scaphoid fossa and decreased in the lunate fossa from stage IIIA to IIIB group. These findings indicate that the load is shifted away from the lunate to the scaphoid with the progression of Kienb?ck's disease in living subjects.  相似文献   
27.
Coracoacromial arch decompression in rotator cuff surgery   总被引:1,自引:0,他引:1  
In rotator cuff surgery it is important to obtain adequate decompression of the coracoacromial arch. However, it is difficult to localize the impingement site preoperatively. Based on histological and morphological studies and the clinical findings in 45 patients and 15 cadavers, we have tried to determine the impingement site. In addition, as a part of these investigations, we assessed the clinical outcome for 100 patients. Soft tissue decompression was indicated in 12 shoulders, anterior acromioplasty in 67 and anterior acromioplasty with coracoplasty in 21. According to Neer’s criteria there were 92 satisfactory and 8 unsatisfactory results. The mean postoperative UCLA score was 33.4 points and the results were rated excellent in 78, good in 18 and fair in 4.
Résumé  Dans la chirurgie de la coiffe des rotateurs, il est important d’obtenir une décompression adéquate sous-acromiale, mais il est difficile de localiser la zone de conflit avant l’opération. A partir d’études histologiques, morphologiques et des conclusions cliniques chez 45 malades et 15 cadavres, nous avons essayé de déterminer l’emplacement du conflit. De plus, nous avons évalué le résultat clinique de 100 cas. La décompression des parties molles était indiquée dans 12 épaules, l’acromioplastie antérieure dans 67 et l’acromioplastie antérieure avec coracoplastie dans 21 cas. D’après les critères de NEER, il y avait 92 résultats satisfaisants et 8 médiocres. Le score UCLA moyen postopératoire était à 33,4 points avec 78 résultats jugés excellents, 18 jugés bons, et 4 médiocres.


Accepted: 19 March 2000  相似文献   
28.
Vascularised fibular grafts. An experience of 102 patients   总被引:6,自引:0,他引:6  
The results and complications of 104 vascularised fibular grafts in 102 patients are presented. Bony union was ultimately achieved in 97 patients, with primary union in 84 (84%). The mean time to union was 15.5 weeks (8 to 40). In 13 patients, primary union was achieved at one end of the fibula and secondary union at the other end. In these patients, the mean time to union was 31.1 weeks (24 to 40). Five patients failed to achieve union, with a resultant pseudarthrosis (3 patients) or amputation (2 patients). There were various complications. Immediate thrombosis occurred in 14 cases. In two of 23 patients with osteomyelitis, infection recurred at two and six months after surgery, respectively. Both patients had active osteomyelitis less than one month before the operation. Bony infection occurred in a patient with a synovial sarcoma of the forearm one year after surgery. In 15 patients, 19 fractures of the fibular graft occurred after bony union, all except one within one year after union. In patients in whom an external fixator had been used, fracture occurred soon after its removal. Union was difficult to achieve in cases of congenital pseudarthrosis of the tibia. Appropriate alignment of the fibular graft is an important factor in preventing stress fracture. The vascularised fibula should be protected during the first year after union. Postoperative complications at the donor site included transient palsy of the superficial peroneal nerve in three patients, contracture of flexor hallucis longus in two and valgus deformity of the ankle in three. Vascularised fibular grafts are useful in the reconstruction of massive bony defects. We believe that meticulous preoperative planning, including choosing which vessels to select in the recipient and the type of fixation devices to use, and care in the introduction of the vascularised fibula, can improve the results and prevent complications.  相似文献   
29.
The mechanism underlying hypertrophy of experimentally vascularized bone grafts was studied in 15-week-old rats. The segmental ulna was grafted to the tibial defect with an external fixator. In experiment 1, 24 rats were classified into four groups to evaluate conventional (non-vascularized), cuff (periosteum-encased, non-vascularized), and vascularized bone grafts, and vascularized segmental grafts with fracture. In experiment 2, 12 rats were classified into two groups according to the presence of mechanical loading. This involved vascularized bone grafts with external fixators, and vascularized bone grafts with external fixators removed after bone union. The bone dynamics of the grafts were investigated by several methods, including roentgenographic analysis, histologic studies, and fluorochrome labeling. In experiment 1, a slight bone formation was recognized in the conventional bone graft, while irregular bone formation with creeping substitution was observed in the cuff graft. The vascularized bone graft showed significant hypertrophy; hypertrophy of the vascularized bone with fracture was greater than that without fracture. In experiment 2, markedly circumferential bone formation was observed after removal of the external fixator, while slight new bone formation was observed during the late postoperative period in bone with an external fixator. These results suggest that hypertrophy can be promoted by artificial fracture of the grafted bone, and that mechanical loading is an important factor for remodeling of grafted bone.  相似文献   
30.
To elucidate the sites of and mechanisms of analgesic effect of centrally injected calcitonin, we examined expression of calcitonin receptor mRNA in the mouse brain by in situ hybridization techniques. Calcitonin receptor mRNA was expressed in various brain regions, including the preoptic area, dorsomedial hypothalamic nucleus, lateral hypothalamic area, periaqueductal gray, dorsal raphe nucleus, locus coeruleus, lateral parabrachial nucleus, gigantocellular reticular nucleus alpha part, lateral paragigantocellular nucleus, raphe magnus nucleus and solitary tract nucleus, which are known to play important roles in pain modulation. In addition, a double in situ hybridization technique demonstrated the intense expression of calcitonin receptor mRNA on serotonergic neurons in some raphe nuclei and the lateral paragigantocellular nucleus, suggesting the involvement of central serotonergic pathways in analgesic effect of calcitonin.  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