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   52601篇
  免费   2521篇
  国内免费   265篇
耳鼻咽喉   452篇
儿科学   932篇
妇产科学   605篇
基础医学   6588篇
口腔科学   1352篇
临床医学   3651篇
内科学   13793篇
皮肤病学   1143篇
神经病学   3888篇
特种医学   1995篇
外科学   8981篇
综合类   179篇
一般理论   1篇
预防医学   1637篇
眼科学   984篇
药学   3356篇
中国医学   113篇
肿瘤学   5737篇
  2023年   316篇
  2022年   677篇
  2021年   1206篇
  2020年   608篇
  2019年   818篇
  2018年   1098篇
  2017年   810篇
  2016年   1046篇
  2015年   1008篇
  2014年   1405篇
  2013年   1644篇
  2012年   2653篇
  2011年   3046篇
  2010年   1644篇
  2009年   1531篇
  2008年   2579篇
  2007年   2747篇
  2006年   2763篇
  2005年   2817篇
  2004年   2709篇
  2003年   2675篇
  2002年   2620篇
  2001年   1606篇
  2000年   1590篇
  1999年   1419篇
  1998年   679篇
  1997年   540篇
  1996年   451篇
  1995年   383篇
  1994年   362篇
  1993年   327篇
  1992年   981篇
  1991年   871篇
  1990年   775篇
  1989年   776篇
  1988年   708篇
  1987年   718篇
  1986年   628篇
  1985年   587篇
  1984年   392篇
  1983年   323篇
  1982年   179篇
  1979年   251篇
  1978年   191篇
  1977年   159篇
  1975年   165篇
  1974年   161篇
  1973年   175篇
  1969年   155篇
  1967年   155篇
排序方式: 共有10000条查询结果,搜索用时 13 毫秒
81.
BACKGROUND AND METHODS. It is not certain whether patients with Kawasaki disease have a higher death rate than the age-matched healthy population. We therefore undertook a study to investigate this question. Between July 1982 and December 1988, 53 collaborating treatment centers collected data on all patients who had an unequivocal new diagnosis of Kawasaki disease; patients who had recurrent disease or whose first visit to the treatment center occurred more than 14 days after the onset of symptoms were excluded. Patients were followed from the time of the first visit to the treatment center until December 31, 1989, or until death, whichever occurred first. The expected number of deaths was calculated from Japanese vital-statistics data and compared with the number observed. RESULTS. Of 4676 patients who met the eligibility criteria, 4608 (98.5 percent) were followed through either the end of the study or the date of death. Thirteen patients (10 boys and 3 girls) died during the study period. The number of deaths expected was 7.61 (ratio of observed to expected deaths, 1.71; 95 percent confidence interval, 0.91 to 2.92). The ratio was 2.04 (95 percent confidence interval, 0.98 to 3.76) for boys and 1.11 (95 percent confidence interval, 0.23 to 3.23) for girls. During the acute phase of the disease (the first two months after onset), the ratios of observed to expected deaths were higher: 9.86 overall (95 percent confidence interval, 3.95 to 20.31), 13.33 for boys (95 percent confidence interval, 4.89 to 29.07), and 3.85 for girls (95 percent confidence interval, 0.10 to 21.42). After the acute phase, however, both sexes had ratios of observed to expected deaths that were lower than 1, and the difference from the control population was not statistically significant. CONCLUSIONS. The mortality rate among boys with Kawasaki disease in Japan is twice that among healthy boys of the same age, and most deaths occur within two months of diagnosis. The mortality rate among girls with the disease appears similar to that among healthy girls, although the numbers are very small.  相似文献   
82.
Human gastric carcinoma cells from one of three long-term cultured cell lines (HPE-GAC-T) were injected into peritoneal cavities of BALB/c mice. The surviving celss in vivo were collected 3 days later. Following brief cultivation in vitro, those cells were reinjected into mice by the same route. This procedure was repeated 3 times. The cultured cancer cells recovered from the mice on the 3rd passage, at a 92.5% recovery rate, showed xenotransplantability in BALB/C nu/nu mice by subcutaneous injection. This subline (GAC-T.M-2) can be maintained in vitro but not in vivo while maintaining heterotransplantability. Three original cancer cell lines did not show tumorigenicity in nude mice. Animal passages by the same protocol failed to select tumorigenic sublines from the other cell lines (HPE-GAC-2 and -3). Factors affecting tumorigenic capacity of cancer cells in nude mice were studied in vivo and in vitro by comparing the properties of GAC-T.M-2 and parental cancer cells (GAC-T.O). Treatment of the hosts by injection of anti-asialoGM1 antibody or cyclophosphamide, adult thymectomy of BALB/c mice, and 400 rads whole body irradiation did not enhance the growth of either GAC-T.M-2 or -T.O cells. There was no detectable difference between in vitro growth properties of the original and variant cells at a rather high cell density. However, at a low cell density GAC-T.M-2 cells showed a higher cell growth rate and increased [3H] thymidine incorporation and possessed higher colony forming activity in the liquid medium than their parental cells. High dense expression of epidermal growth factor (EGF) receptors was evident equally in both GAC-T cells, however, GAC-T.M-2 cells were more sensitive to down-regulation by EGF in culture. Tumor cells of HPE-GAC-2 and -3 lines expressed minimum amount of EGF receptors on their cell surfaces and were refractory to additional EGF in culture. The results indicate that growth factors and their receptors are responsible for tumorigenicity in nude mice.  相似文献   
83.
We successfully performed arterial embolization of an arteriovenous fistula between the left gastric artery and vein. The increased blood flow in the portal vein via the left gastric vein and the arteriovenous fistula induced severe portal hypertension. After obliteration of the left gastric artery, the arteriovenous fistula was not opacified on angiography and the portal hypertension improved.  相似文献   
84.
To examine the effects of transient hyperprolactinemia on in vitro fertilization and embryo transfer, 61 cycles in 50 euprolactinemic ovulatory women with irreparable tubal diseases were stimulated with clomiphene (CC) alone or CC and human menopausal gonadotropin followed by human chorionic gonadotropin (hCG). Serum prolactin (PRL) increased after hCG administration with peak values of 45.4 +/- 4.2 ng/ml on the day of laparoscopic oocyte aspiration. The highest serum estradiol (E2) concentration was found on the day before PRL peak and serum progesterone (P) began to increase after hCG injection concomitant with the PRL rise. The group having 50 ng/ml or more of PRL (34 cycles) had significantly higher levels of E2 during preovulatory and early luteal phase compared to those of the group having less than 50 ng/ml of PRL (27 cycles) but there was no significant difference between the P levels in the two groups. In the higher PRL group 72 (62.1%) of 116 collected oocytes were fertilized and 6 (20.0%) conceived. In the lower PRL group 45 oocytes (58.4%) of 77 were fertilized and 3 (12.5%) became pregnant. These data suggest that elevated serum PRL concentrations may have no effect on fertilization of oocytes in vitro or embryonic development.  相似文献   
85.
A 69-year-old man was admitted to hospital because of sustainedventricular tachycardia with right bundle branch block morphology.After abolition of ventricular tachycardia, an electrocardiogramshowed atrial fibrillation, complete right bundle  相似文献   
86.
To investigate the relationship between the effects of bone turnover and bone marrow cell development in bone cells, we developed a mouse voluntary climbing exercise model. Climbing exercise increased bone volume and transient osteogenic potential of bone marrow. This model would be suitable for investigating the mechanistic roles of mechanical loading. INTRODUCTION: The relationship between bone mass gain and local bone formation and resorption in mechanically loaded bone is not well understood. MATERIALS AND METHODS: Sixty-five C57BL/6J mice, 8 weeks of age, were assigned to five groups: a baseline control and two groups each of ground control and climbing exercise mice for 2 and 4 weeks. Mice were housed in a 100-cm tower and had to climb toward a bottle placed at the top to drink water. RESULTS: Compared with the ground control, bone mineral density of the left femur increased in the climbing mice at 4 weeks. At 2 and 4 weeks, bone formation rate (BFR/BS) of periosteal surface, the cross-sectional area, and moment of inertia were increased in the climbing mice, whereas BFR/BS and eroded surface (ES/BS) of endosteal surface did not differ. The trabecular bone volume (BV/TV) of the proximal tibia increased in climbing mice, and osteoclast surface (Oc.S/BS) and osteoclast number decreased at 2 weeks. At 4 weeks, there were increases in BV/TV and parameters of bone formation, including mineralized surface, mineral apposition rate, and bone formation rate. In marrow cell cultures from the tibia, the number of alkaline phosphatase+ colony forming units-fibroblastic and the area of mineralized nodule formation in climbing mice were increased, and the number of osteoclast-like TRACP+ multinucleated cells was lower at 2 weeks. At 4 weeks, these parameters recovered to the levels of the ground controls. CONCLUSION: Our results indicate that climbing increased trabecular bone volume and reduced bone resorption, with a subsequent increase in bone formation. Intermittent climbing downregulates marrow osteoclastogenic cells and upregulates osteogenic cells initially, but further exercise seemed to desensitize them. Cortical envelopes were enlarged earlier, but the response seems to differ from trabecular bone.  相似文献   
87.
88.
Leiomyoblastoma has been regarded as a neoplasm of smooth muscle origin. With recent progress in immunohistostaining techniques, many clinicopathological discrepancies have been pointed out about the origin of leiomyoblastoma. It has been claimed that gastrointestinal non-epithelial tumors should be regarded as stromal tumors in order to study their origin. In the present study, we performed various forms of immunohistostaining in seven cases of leiomyoblastoma to determine their origin. One case expressed desmine and muscle specific actin and was considered to be derived from smooth muscle. Four neoplasms expressed X-100 protein (two cases were also NSE positive) and were thought to be derived from the nerve. Two cases were of unknown derivation. These results suggest that the cells of leiomyoblastoma may arise from a primitive to totipotential cell of neural lineages that may anomalously express smooth muscle filaments.  相似文献   
89.
The relation between smoking and risk of asthma has been well-examined; however little attention has been paid to the correlation between smoking and asthma symptoms. The aims of this study were to examine respiratory symptoms in asthmatics with a highly prevalent use of inhaled corticosteroid (ICS) and to assess the effects of smoking and its cessation. A cross-sectional study of pulmonologist-based 3197 asthmatics (men 45.2%, ages 20-97) was performed using a questionnaire about smoking habits, the incidence and frequency of symptoms (sputum, cough and wheezing, night symptoms, and shortness of breath), physical activity interference, and medication. Although 81.4% of the patients used ICS according to the international guideline, 14.9% had activity interference, and daily symptoms remained in 43.3%. At the time of the questionnaire, 21.6% were current and 25.1% were ex-smokers. In multiple logistic regression analysis, the factors of significance (p < 0.0001) were (1) smoking; for all four symptoms, (2) age and duration of asthma; for shortness of breath. Current smokers were at a risk of sputum (age-adjusted odds ratio 2.32 [95% confidence interval 1.73-3.11]; 2.09 [1.57-2.79]), of cough and wheezing (2.38 [1.81-3.14]; 1.78 [1.35-2.36]), of night symptoms (1.95 [1.41-2.60]; 1.47 [1.09-1.98]), and of shortness of breath (1.70 [1.26-2.28]; 1.30 [0.97-1.75]) in men and women, respectively. These ratios in ex-smokers decreased to the level similar to nonsmokers. Although 81.4% of asthmatic patients used ICS, 43.3% complained of daily respiratory symptoms, especially sputum. It is suggested that the effects of ICS on asthma symptoms may be interfered with by smoking and therefore more emphasis should be placed on cessation of smoking.  相似文献   
90.
Endoscopic resection has been accepted as the standard treatment for intramucosal gastric tumors of differentiated type. However, the indication was limited to small tumors to achieve en bloc resection and prevent local recurrence in cases of conventional endoscopic mucosal resection (EMR) such as the strip biopsy and the cap technique. To avoid multi‐fragmental resection, we have developed endoscopic submucosal dissection (ESD) as a new endoscopic resection technique. ESD is a remarkable technique, because we make it possible to remove the lesions en bloc regardless of size, shape, coexisting ulcer, and location. However, it is difficult or impossible to resect recurrent tumors en bloc in conventional EMR owing to hard fibrosis, and some patients need laparotomy. Using ESD, we can dissect the submucosal layer as we directly look at the submucosa, and remove the lesion safely and reliably even in cases of hard fibrosis. The key to treatment of recurrent tumors in ESD are as follows: (i) using enough submucosal injection solution (we use a mixture of Glyceol and 1% 1900 kDa hyaluronic acid preparation); (ii) incising the mucosa without fibrosis; (iii) understanding characteristics of various cutting devices, and changing other devices in difficult situations. In these ways we can remove the majority of the recurrent tumors en bloc. Hence, we consider that ESD is a very effective treatment which achieves excellent en bloc and complete resection rates and enables patients with intramucosal gastric tumors to a recurrent‐free survival even in recurrent tumors.  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