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   115888篇
  免费   6048篇
  国内免费   138篇
耳鼻咽喉   1771篇
儿科学   5196篇
妇产科学   3928篇
基础医学   16072篇
口腔科学   2830篇
临床医学   8316篇
内科学   21968篇
皮肤病学   3355篇
神经病学   8981篇
特种医学   5045篇
外国民族医学   32篇
外科学   19017篇
综合类   1595篇
一般理论   29篇
预防医学   5809篇
眼科学   3390篇
药学   8046篇
中国医学   323篇
肿瘤学   6371篇
  2018年   887篇
  2017年   773篇
  2016年   1090篇
  2015年   1215篇
  2014年   1599篇
  2013年   2359篇
  2012年   3091篇
  2011年   3139篇
  2010年   1966篇
  2009年   1926篇
  2008年   3245篇
  2007年   3481篇
  2006年   3626篇
  2005年   3742篇
  2004年   3687篇
  2003年   3555篇
  2002年   3506篇
  2001年   7013篇
  2000年   6958篇
  1999年   5857篇
  1998年   1624篇
  1997年   1558篇
  1996年   1338篇
  1995年   1201篇
  1994年   1091篇
  1993年   1119篇
  1992年   3765篇
  1991年   3577篇
  1990年   3563篇
  1989年   3349篇
  1988年   2986篇
  1987年   2895篇
  1986年   2803篇
  1985年   2618篇
  1984年   1943篇
  1983年   1595篇
  1982年   928篇
  1981年   917篇
  1980年   765篇
  1979年   1823篇
  1978年   1347篇
  1977年   1114篇
  1976年   936篇
  1975年   1178篇
  1974年   1213篇
  1973年   1204篇
  1972年   1041篇
  1971年   975篇
  1970年   882篇
  1969年   789篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
861.
Background: The purpose of the present study was to assess the effects of intravenous lidocaine on spatial changes of electroen-cephalographic power and on psychomotoric status in conscious volunteers.
Methods: In 11 healthy volunteers lidocaine (2-min bolus, 100 mg; 15-min infusion, 40 μg kg-1 min-1) or placebo were given intravenously in a randomized, single-blinded, two-way crossover study. Haemodynamics and lidocaine plasma concentrations were measured at baseline and within a period of 30 min following bolus injection. Vigilance and emotional status were tested using visual analogue scales (VAS). Toxic CNS effects were evaluated by a questionnaire. The raw EEG (17 leads, reference Cz) and computed power spectra were continuously recorded.
Results: The chosen lidocaine dosage led to nearly constant plasma concentrations (unbound lidocaine 2.5 min and 15 min after bolus 0.36±0.14 μg/ml and 0.30±0.06 μg/ml, respectively [mean±SD]). The placebo caused no symptoms, changes in VAS-scores or EEG-parameters. Lidocaine induced pronounced subjective symptoms and significant increases in delta activity for 15 min, most dominant at the frontotemporal and occipital leads (max. +219% O1). Frontal and occipital beta1 and beta2 power (max. +131% and +124% at O1, respectively) was immediately increased after the bolus injection. No EEG changes occurred at central region Cz, and no interhemispheric EEG differences were noted. Theta, alphal, and alpha2 power remained unchanged.
Conclusion: The current data demonstrate simultaneous changes in psychomotoric status as well as delta and beta spectral power during lidocaine infusion. These data could be an indication that the pronounced frontotemporal and occipital EEG changes are the electroencephalographic expression of subjective sensations.  相似文献   
862.
The interaction of 5-fluorouracil (5-FU) and cisplatin (CDDP) was studied in Bp8 ascites sarcoma cells growing in mice. By density gradient centrifugation in Percoll solution, non-viable cells were separated from viable cells. Single drug treatment with doses of 12 and 36 mg/kg body weight of 5-FU and 0.4 and 0.8 mg/kg body weight of CDDP did not yield non-viable cells during the time period studied (96 h). Combination of the drugs increased the non-viable cells to about 10-25% depending on the doses given. This indicates a supra-additive cytotoxic effect. Analysis of the distribution of viable cells in the different cell cycle phases by flow cytometry showed an accumulation of cells in the S-phase after 5-FU and in the S- and G2-phases of the CDDP or combined 5-FU-CDDP treatment. Similar analysis of non-viable cells showed a similar cell cycle distribution, which suggests that supra-additive cytotoxicity is not cell cycle specific. By labeling the DNA of the tumor cells with [125T]-deoxyuridine and using whole body measurement, the cell loss was studied. No changes in cells loss after single drug and combined treatment were found during the observation time. The molecular basis for the interaction between 5-FU and CDDP should be elucidated.  相似文献   
863.
In order to detect possible urinary tract abnormalities among wetters, assessments of previous history completed by ultrasonography of the urinary tract and uroflowmetry were obtained for 145 wetting children and a random sample of 156 sex-matched non-wetting children drawn from a population of 3,375 seven-year-olds. Ultrasonography revealed abnormalities, including both morphological ones and cases with incomplete bladder emptying, in 5 out of 73 nightwetters (6.8%, 95% confidence limit, CL, 1.1-12.6), 10 out of 72 day and day and nightwetters (hereafter daywetters) (13.9%, CL 5.9-21.9) and 4 controls (2.6%, CL 0.1-5.0), the figure for the daywetters differing significantly from that for the controls (p less than 0.01). A fractioned voiding curve was recognized in 1 nightwetter (1.4%, CL -1.3-4.0), 7 daywetters (9.7%, CL 2.9-16.6) and 7 controls (4.5%, CL 1.2-7.7) the difference between the nightwetters and daywetters being significant (p less than 0.05). Depending on the previous history and abnormal findings in ultrasonography or uroflowmetry, examinations were continued with intravenous pyelography, voiding cystography, cystoscopy and/or by cystometry. Finally, marked structural or functional disorders of the urinary tract were detected in 11 out of 72 daywetters (15.3%, CL 7.0-23.6), 1 out of 73 pure nightwetters and 1 out of 156 control children. It is concluded that imaging of the urinary tract is not necessary for pure nightwetters, while ultrasonography or uroflowmetry and more sophisticated radiological or urological methods should be focused on those children with daytime wetting and clinical symptoms of voiding disturbances.  相似文献   
864.
Summary Temporary impairment of blood supply has been suggested to cause bone remodeling. The degradation of cells and matrix and the attraction of resorbing cells were examined in this study. Bone specimens of rabbits were stored in vitro for 2–20 days. At the end of this aging process the probes were tested for their chemotactic activity toward autologous leukocytes in a diffusion chamber. Both supernatant from the aged bone specimens and ground bone particles exhibited significant chemotactic activity that was specifically attracting monocytes. It is suggested that soluble bone matrix proteins or degeneration products liberated during ischemic damage to cortical bone initiate the resorptive process.This work was supported by the Swiss National Science Foundation, grant no. 3.857.0.83, and by the Studienstiftung des deutschen Volkes  相似文献   
865.
Abstract. The present study was carried out in a private periodontal practice. 8 clinical criteria were chosen to select patients for microbiological examination. These criteria characterize prominent features of disease which at the start, during, or in the maintenance phase of treatment suggest difficulties in the progress of the periodontal therapy. Based on these clinical characteristics, an inventory was made of the prevalence of the 3 putative periodontal pathogens: Actinobacillus actinomycetemcomitans, Porphyromonas gingivalis, Prevotella intermedia. Out of 320 referred patients 91 patients did meet 1 of the clinical criteria and consequently were selected for microbiological examination. Results showed that young patients (19–30 years) with periodontitis demonstrated the presence of A. actinomycetemcomitans more often (69%: p (0.005) compared to older age cohorts. A. actinomycetemcomitans was found more often when localized breakdown (in particular in the 1 st molar and incisor region) was observed and in patient who responded poorly to scaling and rootplaning. P. gingivalis and P. intermedia were most frequently recovered in patients showing primarily a bone loss pattern of angular defects of 5 mm. Retrospectively, these patients were further categorized, based on full mouth radiographs, in (1) patients with primarily horizontal bone loss and (2) patients with primarily angular bony defects. Results showed that A. actinomycetemcomitans occurred less frequently in patients showing horizontal bone loss ( p (0.05).  相似文献   
866.
Special status of lateral clavicular fracture]   总被引:1,自引:0,他引:1  
Fractures of the lateral clavicle have different biomechanical conditions compared with fractures of the medial and central third; they therefore demand different therapy. Some 237 patients with fractures of the clavicle were followed, of which 75 (33%) were located in the lateral third of the clavicle. At the 5-year follow-up after exclusively conservative treatment, good results were found for Neer types I and III and 3 J?ger/Breitner type IIb fractures, while 4 out of 13 J?ger/Breitner type II a fractures ended in pseudarthroses (31%). Conservative treatment is recommended for Neer types I and III, as well as for the more stable J?ger/Breitner type II b and old II a fractures. Therefore, a new bandage is presented. It prevents the posterior and upward dislocation of the proximal fragment by vertical compression and rotation of the distal fragment by fixation of the arm. Open reduction and internal fixation by preferably extraarticular implants is recommended for unstable and dislocated J?ger/Breitner type II a fractures. For fractures of the lateral clavicle, good results can be achieved when the instability is recognized and adequately treated.  相似文献   
867.
Summary The pathogenetic relationship between tumour and hypertension was investigated in 129 patients with renal cell carcinoma, of whom 41 (31.8%) were hypertensive. Of these 41 patients with renal tumours and hypertension, 6 (14.6%) were found to have primary reninism. In these patients the plasma renin activity in blood from the renal veins showed a tumour kidney to contralateral kidney ratio of between 4 and 7, and 2 patients also had secondary hyperaldosteronism. In the same 6 cases the renin content in the renal tumour tissue was significantly higher than that in tissue from the adjacent tumour-free renal cortex of the ipsilateral kidney. Immunohistochemical demonstration of renin in the tumour was only possible in these 6 cases. In 5 of these patients blood pressure returned to normal following nephrectomy; in the 6th case there was a drop in blood pressure after nephrectomy. In 3 renin-positive tumours examined, autonomous renin production was demonstrated in cell culture. Renin-producing renal cell carcinomas are an uncommon cause of renal hypertension. The differential diagnosis of hypertension should therefore also include renal tumour.  相似文献   
868.
Retinal detachment in an aphakic eye is a grave therapeutical problem. There exists some fears that cataract extraction with implantation of an artificial lens may increase the number of these complications. Three hundred and seventy cases of cataract extraction with implantation of an artificial lens performed in our department were analysed from the point of view of the incidence of retinal detachment. The cataract was extracted extra- and intracapsularly and the artificial lens was implanted in the anterior as well as in the posterior chamber. During the period of observation--4 months to 3 years--it was established that the number of the retinal detachment in pseudophakia was not larger than in aphakic eyes without implant.  相似文献   
869.
The specific humoral immune response against Epstein-Barr virus (EBV) antigens in patients with nasopharyngeal carcinoma (NPC) was compared to that of patients with infectious mononucleosis (IM) and other EBV-seropositive subjects using immunoblotting technique. Almost all sera from E,BV serologically associated NPC reacted reproducibly with a major group of polypeptides (four to six) of early antigen (EA) complex with molecular weights ranging from 50 kD to 58 kD, and with some additional polypeptides. Sera from IM-patients reproducibly recognized only one polypeptide of 50 kD belonging to the major group of polypeptides of EA-complex. Sera from patients with other types of head and neck cancer and relatively high levels of IgG antibody against viral capsid antigen (VCA) and EA did not react reproducibly with any of the EBV-associated proteins.  相似文献   
870.
The fingers of seven women with primary Raynaud's phenomenon (PRP), 10 female controls, seven men with vibration induced white finger (VWF), and eight male controls were exposed to vibration and the relative change in finger capillary blood flow was measured by an atraumatic 133xenon washout technique without and during proximal nervous blockade. All four groups showed a vasoconstriction to vibration (p less than or equal to 0.02) which was abolished by proximal nervous blockade. Women with PRP had an augmented response to vibration (p less than 0.01) and men with VWF had a normal response (p greater than 0.10) when compared with that of their respective sex matched controls. The results show the existence of a vibration elicited central sympathetic vasoconstrictor reflex in the normal finger and in fingers affected by PRP and VWF. The results indicate a hyperreactivity of the central sympathetic nervous system in PRP and VWF and a dysfunction of the peripheral sensory nerve fibres in subjects with VWF. The described vibration test may be of guidance in the differentiation of PRP from VWF.  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