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   2802篇
  免费   142篇
  国内免费   6篇
耳鼻咽喉   24篇
儿科学   74篇
妇产科学   147篇
基础医学   445篇
口腔科学   89篇
临床医学   203篇
内科学   641篇
皮肤病学   27篇
神经病学   224篇
特种医学   62篇
外科学   451篇
综合类   17篇
预防医学   132篇
眼科学   70篇
药学   149篇
中国医学   1篇
肿瘤学   194篇
  2023年   8篇
  2022年   14篇
  2021年   49篇
  2020年   29篇
  2019年   34篇
  2018年   52篇
  2017年   50篇
  2016年   66篇
  2015年   64篇
  2014年   114篇
  2013年   108篇
  2012年   142篇
  2011年   172篇
  2010年   118篇
  2009年   108篇
  2008年   208篇
  2007年   214篇
  2006年   187篇
  2005年   205篇
  2004年   163篇
  2003年   169篇
  2002年   143篇
  2001年   48篇
  2000年   22篇
  1999年   31篇
  1998年   22篇
  1997年   35篇
  1996年   37篇
  1995年   29篇
  1994年   22篇
  1993年   19篇
  1992年   17篇
  1991年   20篇
  1990年   15篇
  1989年   15篇
  1988年   14篇
  1987年   15篇
  1986年   19篇
  1985年   17篇
  1984年   13篇
  1983年   11篇
  1982年   15篇
  1981年   9篇
  1980年   9篇
  1979年   10篇
  1978年   10篇
  1977年   8篇
  1973年   9篇
  1971年   6篇
  1969年   5篇
排序方式: 共有2950条查询结果,搜索用时 15 毫秒
961.
A 75-year-old man with right upper quadrant abdominal pain was diagnosed by gastroscopy to have an impacted gallstone in the duodenal bulb. Using the polypectomy loop, the stone was extracted from the bulbus and mobilized into the stomach. After failure to remove the stone from the stomach as well as fragmentation by mechanical lithotripsy, electrohydraulic lithotripsy was used to break up the stone, parts of which passed spontaneously through the bowel. Thus, it was unnecessary to proceed with surgical enterolithotomy to remove, from the duodenal bulb, the impacted gallstone responsible for the gastric outlet obstruction.  相似文献   
962.
The baseline characteristics and outcome of patients with acute chest pain who were brought to the hospital by public versus private mobile intensive care units were compared. Of 283 patients brought to the Department of Emergency Medicine at the Tel Aviv Sourasky Medical Center by mobile units in July and September of 1995, 163 were transported by the private service and 120 by the public service. Patients who were brought by the private service were older and had significantly more comorbidities, especially cardiac history. However, a significantly higher proportion of patients brought by the public service suffered confirmed myocardial infarction, and were hospitalized in the intensive coronary care unit. In addition, mortality in this group was significantly higher (4.0% vs. 2.2%). Possible explanations for this finding are greater accessibility or bias in the prehospital management of patients channeled through the private mobile service.  相似文献   
963.
The results of continuous 12-hour electrocardiography in 40 convalescent patients after myocardial infarction undergoing a programme of readaptation on average 4 weeks after the initial infarction are reported. The frequency and alarming nature of the VES observed in 75% patients who had already undergone selection for the coronary readaptation programme, 30% of whom were receiving antiarrhythmic therapy, is emphasized. The observation of a progressive increase in the number of VES during the day prompts the following suggestions: the possibility of limited continuous ECG monitoring at the end of the day, the need to adapt the dosage of antiarrhythmic drugs during this most critical period. The comparison of the results of continuous ECG with those of repeated exercise ECG seems very positive, but some reservations are made and it would seem logical to associate these two complementary methods of investigation.  相似文献   
964.
Rho GTPases play an important and versatile role in several biological processes. In this study, we identified the zebrafish ortholog of the mammalian Rho A guanine exchange factor, synectin-binding guanine exchange factor (Syx), and determined its in vivo function in the zebrafish and the mouse. We found that Syx is expressed specifically in the vasculature of these organisms. Loss-of-function studies in the zebrafish and mouse point to a specific role for Syx in angiogenic sprouting in the developing vascular bed. Importantly, vasculogenesis and angioblast differentiation steps were unaffected in syx knockdown zebrafish embryos, and the vascular sprouting defects were partially rescued by the mouse ortholog. Syx knockdown in vitro impairs vascular endothelial growth factor-A-induced endothelial cell migration and angiogenesis. We have also uncovered a potential mechanism of endothelial sprout guidance in which angiomotin, a component of endothelial cell junctions, plays an additive role with Syx in directing endothelial sprouts. These results identify Syx as an essential contributor to angiogenesis in vivo.  相似文献   
965.
Vilozni D  Barak A  Efrati O  Augarten A  Springer C  Yahav Y  Bentur L 《Chest》2005,128(3):1146-1155
STUDY OBJECTIVES: To explore the role of respiratory interactive computer games in teaching spirometry to preschool children, and to examine whether the spirometry data achieved are compatible with acceptable criteria for adults and with published data for healthy preschool children, and whether spirometry at this age can assess airway obstruction. DESIGN: Feasibility study. SETTINGS: Community kindergartens around Israel and a tertiary pediatric pulmonary clinic. PARTICIPANTS: Healthy and asthmatic preschool children (age range, 2.0 to 6.5 years). INTERVENTION: Multi-target interactive spirometry games including three targets: full inspiration before expiration, instant forced expiration, and long expiration to residual volume. MEASUREMENTS AND RESULTS: One hundred nine healthy and 157 asthmatic children succeeded in performing adequate spirometry using a multi-target interactive spirometry game. American Thoracic Society (ATS)/European Respiratory Society spirometry criteria for adults for the start of the test, and repeatability were met. Expiration time increased with age (1.3 +/- 0.3 s at 3 years to 1.9 +/- 0.3 s at 6 years [+/- SD], p < 0.05). FVC and flow rates increased with age, while FEV1/FVC decreased. Healthy children had FVC and FEV1 values similar to those of previous preschool studies, but flows were significantly higher (> 1.5 SD for forced expiratory flow at 50% of vital capacity [FEF50] and forced expiratory flow at 75% of vital capacity [FEF75], p < 0.005). The descending part of the flow/volume curve was convex in 2.5- to 3.5-year-old patients, resembling that of infants, while in 5- to 6-year-old patients, there was linear decay. Asthma severity by Global Initiative for Asthma guidelines correlated with longer expiration time (1.7 +/- 0.4 s; p < 0.03) and lower FEF50 (32 to 63%; p < 0.001) compared to healthy children. Bronchodilators improved FEV1 by 10 to 13% and FEF50 by 38 to 56% of baseline. CONCLUSIONS: Interactive respiratory games can facilitate spirometry in very young children, yielding results that conform to most of the ATS criteria established for adults and published data for healthy preschool children. Spirometric indexes correlated with degree of asthma severity.  相似文献   
966.
967.
BACKGROUND: Ethnic origin affects spirometric prediction values. Our aims were to investigate the effect of ethnic origin on prediction equations in an immigrant-based society, identify possible deviations from commonly used prediction equations and analyze the effect of miscalculation in a large cohort of apparently healthy individuals. METHODS: Healthy never-smokers participants from a large Israeli survey underwent lung function testing and were divided into two major ethnic groups: Ashkenazi Jews (AJ) and Sephardic Jews (SJ). Data were analyzed by multiple linear regressions. Forced vital capacity (FVC), forced expiratory volume in 1s (FEV1) and the FEV1/FVC ratio were measured according to ERS-ATS guidelines. RESULTS: The study population comprised 3150 individuals (AJ=1817; SJ=1333). AJ tended to be older and taller than SJ (all p<0.005). Ethnicity entered as a significant regression variable for FVC for both genders and for FEV1 for females only. The final regression model for both FVC and FEV1 had R2=0.71 and the standard error of the estimate (SEE) for FVC and FEV1 were 0.54 and 0.43 L, respectively. The regression model for the FEV1/FVC ratio has less statistical strength (R2=0.06, SEE=6.15%). We found statistically significant underestimates of predicted lung volumes from the commonly used prediction equation for each ethnic group. CONCLUSIONS: Ashkenazi and Sephardic Jews have different ranges of normal pulmonary function values. Lung function prediction equations in an immigrant-based society should be based on local and not previously reported regional equations and adjusted for ethnic attributed variance.  相似文献   
968.
Pacemaker current (I(f)) in the human sinoatrial node.   总被引:1,自引:0,他引:1  
AIMS: Animal studies revealed that the hyperpolarization-activated pacemaker current, I(f), contributes to action potential (AP) generation in sinoatrial node (SAN) and significantly determines heart rate. I(f) is becoming a novel therapy target to modulate heart rate. Yet, no studies have demonstrated that I(f) is functionally present and contributes to pacemaking in human SAN. We aimed to study I(f) properties in human SAN. METHODS AND RESULTS: In a patient undergoing SAN excision, we identified SAN using epicardial activation mapping. From here, we isolated myocytes and recorded APs and I(f) using patch-clamp techniques. Pacemaker cells generated spontaneous APs (cycle length 828 +/- 15 ms) following slow diastolic depolarization, maximal diastolic potential - 61.7 +/- 4.3 mV, and maximal AP upstroke velocity 4.6 +/- 1.2 V/s. They exhibited an hyperpolarization-activated inward current, blocked by external Cs(+) (2 mmol/L), characterizing it as I(f). Fully-activated conductance was 75.2 +/- 3.8 pS/pF, reversal potential - 22.1 +/- 2.4 mV, and half-maximal activation voltage and slope factor of steady-state activation - 96.9 +/- 2.7 and - 8.8 +/- 0.5 mV. Activation time constant ranged from approximately 350 ms (-130 mV) to approximately 1 s (-100 mV), deactivation time constant 156 +/- 45 ms (-40 mV). The role of I(f) in pacemaker activity was demonstrated by slowing of pacemaker cell diastolic depolarization and beating rate by Cs(+). CONCLUSION: I(f) is functionally expressed in human SAN and probably contributes to pacemaking in human SAN.  相似文献   
969.
OBJECTIVE: Bone marrows (BM) of myelodysplastic syndrome (MDS) patients show increased proliferation and premature programmed cell death (PCD) in vivo as well as in vitro. We explored the proliferative capacity and apoptotic propensity of CD34+ progenitor cells of MDS patients excluding accessory cell interference. MATERIALS AND METHODS: CD34+/CD3-/CD19- cells of 5 MDS patients and 5 normal BM were sorted as single cells into single wells and were cultured in liquid medium. Wells were evaluated on days 4, 7, 10, and 14. PCD was determined by staining with annexin V-FITC. Growth rate and cell doubling time (Td) were calculated for each colony-forming cell. RESULTS: Normal BM CD34+ cells formed clusters and colonies and both showed increasing PCD in time, although within colonies the degree of apoptosis was twice as high (about 25%) as compared with clusters at all time points. In MDS increased cluster formation was observed at all evaluation points when compared to normal BM, whereas the number of colonies was markedly reduced (1/7 of normal). These colonies were also smaller, usually smaller than 100 cells. Significantly enhanced levels of PCD of clusters (53-79%) in combination with longer cell doubling times explain this slower formation of smaller colonies. Surprisingly, these colonies showed considerably lower levels of PCD (7-32%) as compared to normal (1-48%, median values). CONCLUSIONS: In the absence of stromal influences and accessory cells, this study in MDS patients showed intrinsically enhanced proliferation and apoptosis of cluster-forming cells, as the opposite was true for colony-forming cells.  相似文献   
970.
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