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   11099篇
  免费   582篇
  国内免费   27篇
耳鼻咽喉   188篇
儿科学   238篇
妇产科学   263篇
基础医学   2199篇
口腔科学   106篇
临床医学   1083篇
内科学   2278篇
皮肤病学   242篇
神经病学   769篇
特种医学   661篇
外科学   1288篇
综合类   96篇
预防医学   509篇
眼科学   267篇
药学   1049篇
中国医学   17篇
肿瘤学   455篇
  2021年   95篇
  2020年   60篇
  2019年   87篇
  2018年   95篇
  2017年   82篇
  2016年   113篇
  2015年   135篇
  2014年   196篇
  2013年   289篇
  2012年   476篇
  2011年   543篇
  2010年   320篇
  2009年   322篇
  2008年   490篇
  2007年   576篇
  2006年   550篇
  2005年   553篇
  2004年   542篇
  2003年   513篇
  2002年   489篇
  2001年   249篇
  2000年   239篇
  1999年   249篇
  1998年   133篇
  1997年   147篇
  1996年   113篇
  1995年   81篇
  1994年   78篇
  1993年   58篇
  1992年   129篇
  1991年   126篇
  1990年   113篇
  1989年   93篇
  1988年   87篇
  1987年   72篇
  1986年   88篇
  1985年   77篇
  1984年   61篇
  1933年   85篇
  1932年   86篇
  1931年   94篇
  1930年   105篇
  1929年   90篇
  1928年   90篇
  1927年   84篇
  1926年   90篇
  1925年   85篇
  1924年   90篇
  1923年   88篇
  1922年   72篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
11.
12.
BACKGROUND: Bone marrow cell injection has been introduced to treat patients with ischemic heart disease. However, focal application of bone marrow cells may generate an arrhythmogenic substrate. OBJECTIVES: To assess the electrophysiological and arrhythmogenic effects of intramyocardial bone marrow cell injection in patients with chronic myocardial ischemia. METHODS: Bone marrow was aspirated in 20 patients (65+/-11 years, 19 male) with drug-refractory angina and myocardial ischemia. Electroanatomical mapping (NOGA, Biosense-Webster, Waterloo, Belgium) was performed during mononuclear cell isolation. Areas for cell injection were selected based on the localization of ischemia on SPECT. These areas were mapped in detail to evaluate local bipolar electrogram duration, amplitude and fragmentation. Mononuclear cells were injected in the ischemic area with the NOGA system. SPECT and electroanatomical mapping were repeated at 3 months. Holter monitoring was repeated at 3 and 6 months. RESULTS: SPECT revealed a decrease in the number of segments with ischemia (3.5+/-2.5 vs. 1.1+/-1.0 at 3 months; P<0.01) and an increased left ventricular ejection fraction (44+/-13% vs. 49+/-17% at 3 months; P=0.02). The number of ventricular premature beats remained unchanged (10+/-24x10(2)/24h vs. 8+/-23x10(2)/24h at 3 months (P=NS) and 12+/-30x10(2)/24h at 6 months (P=NS)). At 3 months follow-up, bone marrow cell injection did not prolong electrogram duration (15.9+/-4.6 ms vs. 15.6+/-4.0 ms; P=NS), decrease electrogram amplitude (3.8+/-1.5 mV vs. 3.8+/-1.5 mV; P=NS), or increase fragmentation (2.0+/-0.5 vs. 1.9+/-0.4; P=NS). CONCLUSION: Intramyocardial bone marrow cell injection does not increase the incidence of ventricular arrhythmias and does not alter the electrophysiological properties of the injected myocardium.  相似文献   
13.
14.
15.
16.
Therapeutic drug monitoring generally focuses on the plasma compartment only. Differentiation between the total plasma concentration and the free fraction (plasma water) has been described for a number of limited drugs. Besides the plasma compartment, blood has also a cellular fraction which has by far the largest theoretical surface and volume for drug transport. It is with anti-cancer drugs that major progress has been made in the study of partition between the largest cellular blood compartment, i.e., erythrocytes, and the plasma compartment. The aim of the present review is to detail the progress made in predicting what a drug does in the body, i.e., pharmacodynamics including toxicity and plasma and/or red blood cell concentration monitoring. Furthermore, techniques generally used in anti-cancer drug monitoring are highlighted. Data for complex Bayesian statistical approaches and population kinetics studies are beyond the scope of this review, since this is generally limited to the plasma compartment only.  相似文献   
17.
We tested the hypothesis that bone mineral density (BMD) and bone mineral content (BMC) in proximal human femur specimens in the upper neck region of interest (ROI) and femoral neck axis length (FNAL) provide a significantly better prediction of femoral bone strength than standard ROIs in vitro. BMD and BMC were measured in 110 proximal femur specimens using a standard dual-energy X-ray absorptiometry (DXA) scanner. The analysis included a new ROI in the upper neck as well as the standard ROIs. FNAL was obtained from the scan images. The specimens' failure-load was measured in a mechanical loading device, simulating a fall on the greater trochanter. For the standard ROIs, correlations between failure-load and BMD ranged from R2 = 0.64 (shaft ROI) to R2 = 0.70, p < 0.001 (femoral neck). Prediction of strength by BMD did not significantly differ from those of BMC (R2 ranging from 0.65 to 0.75, p < 0.001). In the upper neck ROI, for both BMD and BMC correlations with failure-load were higher (R2 = 0.76 and 0.81, respectively; p < 0.001). A lower, yet still significant, correlation was found between FNAL and bone strength (R2 = 0.23, p < 0.001). Normalization of failure-load with respect to FNAL did not significantly increase the correlations with densitometric measures. This study provides in vitro evidence indicating that among the ROIs of the proximal femur the newly defined upper neck ROI provides the best prediction of bone strength. Only a weak association was observed between failure load and FNAL.  相似文献   
18.
19.
BACKGROUND: The role of large colony streptococci groups C or G as pathogen agents in sore throat has been questioned. AIM: To analyse clinical features of patients with large colony streptococci groups C or G compared with patients with group A streptococci (GAS) and with negative cultures. DESIGN OF STUDY: Prospective study of patients with sore throat. SETTING: Two Norwegian general practices in Stokke and Kongsberg communities with 6500 patients.METHOD: Frequency of clinical features in the three patient categories including the four Centor criteria (fever, anterior cervical lymphadenopathy, tonsillar exudates, and lack of cough), degree of pain on swallowing, pharyngeal rubor, C-reactive protein (CRP) values, patient age between 3 and 14 years, and duration of symptoms before seeing the doctor. A logistic regression analysis to find independent predictors was performed. RESULTS: Out of 306 patients with a sore throat, 244 were adults and 62 were children under 10 years old; 40% were men. One hundred and twenty-seven had GAS, 33 had streptococci groups C or G, and 146 had negative throat cultures. Forty-eight per cent of the GAS patients and 45% of the C or G patients met three or four of the Centor criteria. The logistic regression revealed that in patients with GAS considerable pain on swallowing, an age of 3-14 years and a duration of symptoms of < or =3 days or less were significantly associated with GAS infection in addition to the Centor criteria. The same results were found when all streptococci were analysed together, in addition elevated CRP was significant. In patients with streptococci group C or G an elevated CRP-value was significantly associated. CONCLUSION: Patients with tonsillitis caused by streptococcus groups C or G have, to a large extent, the same clinical picture as patients with GAS. Large colony streptococci groups C and G should be considered as throat pathogens in line with GAS.  相似文献   
20.
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