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   7897篇
  免费   323篇
  国内免费   37篇
耳鼻咽喉   80篇
儿科学   187篇
妇产科学   104篇
基础医学   1147篇
口腔科学   228篇
临床医学   394篇
内科学   2315篇
皮肤病学   142篇
神经病学   519篇
特种医学   265篇
外科学   1212篇
综合类   27篇
预防医学   184篇
眼科学   81篇
药学   498篇
中国医学   22篇
肿瘤学   852篇
  2023年   31篇
  2022年   61篇
  2021年   120篇
  2020年   85篇
  2019年   119篇
  2018年   115篇
  2017年   110篇
  2016年   126篇
  2015年   122篇
  2014年   201篇
  2013年   281篇
  2012年   480篇
  2011年   528篇
  2010年   281篇
  2009年   240篇
  2008年   488篇
  2007年   555篇
  2006年   599篇
  2005年   597篇
  2004年   544篇
  2003年   494篇
  2002年   492篇
  2001年   103篇
  2000年   91篇
  1999年   97篇
  1998年   157篇
  1997年   111篇
  1996年   99篇
  1995年   74篇
  1994年   67篇
  1993年   77篇
  1992年   59篇
  1991年   61篇
  1990年   52篇
  1989年   53篇
  1988年   43篇
  1987年   41篇
  1986年   24篇
  1985年   30篇
  1984年   25篇
  1983年   19篇
  1982年   25篇
  1981年   32篇
  1980年   36篇
  1979年   17篇
  1978年   19篇
  1975年   19篇
  1973年   16篇
  1972年   13篇
  1968年   15篇
排序方式: 共有8257条查询结果,搜索用时 23 毫秒
11.
Electrogastrograms (EGGs) were recorded in patients both before and after receiving proximal gastrectomy plus jejunal interposition (PGJI) or just after receiving total gastrectomy plus jejunal interposition (TGJI). Intraluminal pressure was also recorded in some postoperative patients. The EGG 3 cpm component (2.5-4.9 cpm) remained after PGJI, but subsequently decreased with a significant reduction in the preoperative to postoperative ratio of the 3 cpm components (P<0.05). The mean frequency of the 3 cpm components increased significantly after PGJI (P<0.05) and its instability factor increased. The EGG 10 cpm components became relatively dominant compared to other frequency components in 2 out of 8 of patients having PGJI but the mean amplitude of 10 cpm decreased. In TGJI patients, only the 10 cpm component was conspicuous in EGG as in the case of total gastrectomy and Roux en Y anastomosis procedures. The spectral frequencies of intraluminal pressure in the interposed jejunum were similar to the EGG of 10 cpm components both in the case of PGJI and TGJI patients. In conclusion, surface EGG could record the electrical activities of the interposed jejunum more easily in patients having had TGJI than in PGJI.  相似文献   
12.
13.
Thrombotic microangiopathy (TMA) may develop after living donor liver transplantation (LDLT), but the mechanism is not fully understood. We retrospectively analyzed all patients undergoing LDLT at our center, including TMA patients, to elucidate the clinical characteristics and presentation and to determine which patients have a higher risk of occurrence of TMA. In all, 57 adult patients were reviewed after LDLT at our institution. TMA was diagnosed by sudden and severe thrombocytopenia, followed by hemolytic anemia with fractionated erythrocytes in the blood smear. Clinical features were compared between the TMA group and the non-TMA group. Of the 57 patients, 4 were diagnosed with posttransplantation TMA. ABO blood group (ABO)-incompatibility, cyclophosphamide (CPA), and recipient blood group (type O) were closely correlated with the occurrence of TMA. Thrombocytopenia appeared 1 to 5 days before hemolytic anemia. Coagulative function markers stayed at the same level after TMA, while marked elevation was shown in fibrinolytic function markers such as plasminogen activator inhibitor type 1 (PAI-1). TMA occurred at a higher prevalence in ABO-incompatible graft recipients. Additional factors associated with ABO-incompatible transplantation, such as an overdose of immunosuppressants, may affect the likelihood of TMA. Sudden and severe thrombocytopenia presented before hemolytic anemia and the serum levels of PAI-1 correlated well with the clinical course of TMA. In conclusion, early recognition of thrombocytopenia and elevation of PAI-1 is crucial to diagnose TMA especially in ABO-incompatible LDLT.  相似文献   
14.
Previous studies using primary monolayer cultures of epithelial cells from the involved epidermis of patients with mammary and extramammary Paget's disease investigated whether Paget cells proliferate as other malignant cells do. Although epithelial monolayers from the involved skin were maintained for approximately 45 days, no permanent cell lines were established. The proportion of carcinoembryonic antigen (CEA)-positive cells did not increase in the long-term cultures. Herein, we report studies of whether there is a real reduction of Paget cell numbers or if this is merely a decrease in the expression of CEA by the cells. Furthermore, we investigated whether Paget cells survive longer when cultured free from any potential inhibitory keratinocytes or other epidermal cells. Skin samples were obtained from one patient with mammary Paget's disease and three with extramammary Paget's disease; epidermal cells were cultured in vitro. An enrichment of Paget cells was carried out from the cultured epidermal cells by combining an anti-epithelial membrane antigen monoclonal antibody, binding to immunobeads, and density gradient centrifugation in Nycodenz. The separated cells were re-cultured in Keratinocyte-SFM serum-free media. The proportion of CEA-positive cells did not increase in the cultures, and the purified cells did not show any increase in survival times compared to the non-purified cultured cells. These results suggest that the decrease of CEA-positive cells noted during culture results from a decline in expression of CEA in the Paget cells. Paget cells in the involved epidermis do not proliferate significantly and thus differ from many other malignant cells.  相似文献   
15.
Abstract: A cell line, BAD05, derived from B lymphocytes of an adenosine deaminase (ADA; EC 3,5,4,4)-deficient patient could not proliferate in a serum-free medium containing 100 μmol/l deoxyadenosine. When BAD05 was cultured with ADA-positive fibroblasts, the proliferation of BAD05 was improved. BAD05 cell density increased when the initially mixed ratio of fibroblasts/BAD05 was 1/10 or higher, but decreased when the ratio was 1/20 or lower. Deoxyadenosine concentrations in the medium and ATP and deoxyATP (dATP) levels in the BAD05 were measured after 4 hours of coculture at initial BAD05 cell densities of 1 × 105and 1 × 106cells/ml. Deoxyadenosine concentrations in the medium decreased as the density of fibroblasts increased. The dATP level decreased as the mixed ratio rose. The ratio of fibroblasts/BAD05 rather than the cell density of fibroblasts had a larger effect on the dATP levels in BAD05. Under our experimental conditions, ADA-negative cells proliferated well when the ratio of ADA-positive cells/ADA-negative cells was over 1/10.  相似文献   
16.
OBJECTIVE: We investigate the synaptic factor for the recovery function of evoked responses using a repetitive stimulation technique. METHODS: Somatosensory evoked cortical magnetic field (SEF) was recorded following stimulation of the median nerve using single to 6-train stimulation in 8 healthy subjects. The SEF responses after each stimulus in the train stimulation were extracted by subtraction of the waveforms. RESULTS: An attenuation of the SEF components was recognized after the second of the stimuli, but there was no significant attenuation with the third or later stimulations. The root mean square (RMS) of the 1M (peak latency at 20 ms after stimulation) and 4M (70 ms) components were smaller than that of the single stimulation during the train stimulation, while the 2M (30 ms) and 3M (45 ms) components were not attenuated, but the 3M was facilitated at the fourth to sixth stimulation. CONCLUSION: The synaptic factor was not responsible for the attenuation of the SEF components during repetitive stimulation in healthy subjects. The SEF change disclosed a functional difference among the SEF components during the train stimulation, especially among the later components.  相似文献   
17.
Circadian rhythms of pineal melatonin release were measured in free-moving pigeons, Japanese quails, and chickens under light-dark cycles followed by constant dim light. Although melatonin levels differed among individual birds, circadian rhythms of melatonin were observed in all of them. Using this technique, we could examine phase shifts of melatonin rhythms and suppression of melatonin release by photic stimulation in pigeons. We could also examine effects of norepinephrine infusion on melatonin release. These results indicate that microdialysis is useful for the study of pineal melatonin rhythms in birds.  相似文献   
18.
Summary: A study was conducted to determine whether calcium blockers (CCB) have renoprotective effects, and if so to elucidate the mechanisms of such effects.
A total of 30 uninephrectomized (UNX) spontaneously hypertensive rats (SHR), 5 weeks of age, were divided into three groups. Group 1 was fed a diet containing 0.01% manidipine and 8% NaCl, while groups 2 and 3 were fed diets containing only 8 and 0.5% NaCl, respectively. Feeding of these diets began 7 days after UNX (experimental day 0). Bodyweight, urinary protein /24 h, urinary sodium excretion/24 h, and food intake were measured at certain time intervals.
At time of death (day 9 or 21), estimations of inulin clearance (Cin) and morphological evaluations, determination of glomerular sclerosis index (GSI), tubulointerstitial index (TII) and glomerular volume were performed.
Urinary protein was significantly higher in groups 1 and 2 than in group 3 from day 7 onward, but did not differ between the former two groups. Cin in group 2 was higher than in groups 1 and 3 on day 9, but declined to lower levels than in groups 1 and 3 by day 21. There was no difference in Cin between group 1 and group 3 on day 21. Morphometry (GSI and TII) revealed that renal lesions were more progressive in group 2 than in group 1. Glomeruli in group 2 were markedly larger than those in group 1, but no difference in glomerular volume was noted between groups 1 and 3.
Our findings suggest that CCB prevent progression of renal injury induced by accelerated hypertension in UNX SHR. the mechanisms of prevention may, at least in part, be related to suppression of glomerular hypertrophy. Inhibition of renal injury can be achieved without significant reduction of proteinuria.  相似文献   
19.
Transabdominal resection for esophagocardial cancer and reestablishment of alimentary continuity using bypass methods were performed in 76 patients. Thirteen underwent a bypass with a gastric tube and in 30, a colonic segment was prepared. In the remaining 33, a jejunal segment was used as a bypass organ, with considerable success. The 5 year survival rates were 68.8 per cent in those with stages (I+II), 16.5 per cent in those with stage III, 12.6 per cent in those with stage IV and 22.5 per cent in all cases, indicating similar results compared to those with cancer located in the upper third of the stomach with the limited proximal extension within the esophagocardial junction and operated on during the same period.  相似文献   
20.
Numerous clinical reports have shown the utility of cultured epithelial grafting in the field of plastic and reconstructive surgery. Recently, freezing storage of the cultured epithelium has been tried and has successfully grafted after thawing. It is clinically convenient if it is possible for cultured epithelium to keep its normal structure and viability. However, few papers have described the structural changes in cultured epithelium after freezing storage. In the present study, the morphological changes and cell viability of cultured mucosal epithelial sheets after freezing were studied in comparison with cultured epidermal sheets. Furthermore, we discuss the effect of storage temperature and cryoprotectants.As a result, there were some structural changes such as vacuolar degeneration in the cultured mucosal sheets using dimethyl sulphoxide (DMSO) as a cryoprotectant. Such changes were more clearly observed at −80°C than at −196°C with DMSO. However, little morphological change was observed in both epithelial sheets cultured with glycerin. The cell viability analysed by flow cytometry showed that more than 62% of the cells kept their viability after freezing storage. These results suggest that the optimum conditions of freezing for cultured epithelium were −196°C storage by slow cooling methods with glycerin as a cryoprotectant.  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