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   3497篇
  免费   198篇
  国内免费   28篇
耳鼻咽喉   24篇
儿科学   116篇
妇产科学   141篇
基础医学   413篇
口腔科学   96篇
临床医学   346篇
内科学   737篇
皮肤病学   87篇
神经病学   145篇
特种医学   124篇
外国民族医学   4篇
外科学   505篇
综合类   104篇
预防医学   254篇
眼科学   99篇
药学   230篇
中国医学   27篇
肿瘤学   271篇
  2023年   50篇
  2022年   105篇
  2021年   162篇
  2020年   100篇
  2019年   104篇
  2018年   145篇
  2017年   104篇
  2016年   97篇
  2015年   111篇
  2014年   119篇
  2013年   195篇
  2012年   229篇
  2011年   231篇
  2010年   132篇
  2009年   132篇
  2008年   179篇
  2007年   177篇
  2006年   175篇
  2005年   183篇
  2004年   158篇
  2003年   121篇
  2002年   109篇
  2001年   57篇
  2000年   50篇
  1999年   40篇
  1998年   21篇
  1997年   17篇
  1996年   29篇
  1995年   20篇
  1994年   17篇
  1993年   20篇
  1992年   22篇
  1991年   21篇
  1990年   34篇
  1989年   23篇
  1988年   19篇
  1987年   28篇
  1986年   12篇
  1985年   14篇
  1984年   11篇
  1983年   14篇
  1982年   10篇
  1980年   12篇
  1979年   14篇
  1978年   11篇
  1977年   10篇
  1975年   8篇
  1974年   8篇
  1973年   16篇
  1967年   7篇
排序方式: 共有3723条查询结果,搜索用时 15 毫秒
91.
92.
93.
The Helicobacter pylori virulence gene, cagA, and active forms of the vacuolating cytotoxin gene, vacA, are major determinants of pathogenesis. However, previous studies linking these factors to disease risk have often included patients using aspirin/nonsteroidal anti-inflammatory agents (NSAIDs) or acid-suppressing drugs, both of which may confound results. Also, particularly for gastric cancer (GC), controls have often been of quite different ages. Here, we performed a careful study in a “clean” Belgian population with gastric cancer cases age and sex matched to 4 controls and with a parallel duodenal ulcer (DU) group. As in other populations, there was a close association between the presence of cagA and the vacA s1 genotype. For GC, associations were found for vacA s1-positive (P = 0.01, odds ratio [OR], 9.37; 95% confidence interval [CI], 1.16 to 201.89), i1-positive (P = 0.003; OR, 12.08; 95% CI, 1.50 to 259.64), and cagA-positive status (P < 0.05; OR, infinity; 95% CI, 0.76 to infinity). For DU, associations were found with vacA s1 (P = 0.002; OR, 6.04; 95% CI, 1.52 to 27.87) and i1 (P = 0.004; OR, 4.35; 95% CI, 1.36 to 14.78) status but not with cagA status. Neither condition showed independent associations with the vacA m1 allele or with more biologically active forms of cagA with longer 3′ variable regions. In this Belgian population, the best markers of gastric cancer- and duodenal ulcer-associated strains are the vacA s1 and i1 genotypes. This fits with experimental data showing that the s and i regions are the key determinants of vacuolating cytotoxin activity.  相似文献   
94.

Aims

Intrauterine death is a multifactorial major complication during pregnancy. In this retrospective analysis the pathological anatomical findings of fetuses and placentas as well as maternal factors were evaluated.

Material and methods

A retrospective screening of post-mortem examinations, corresponding placental examinations and clinical data on maternal status (1998–2008) was carried out. A classification of all findings was made with the ReCoDe system and induced abortions and cases with incomplete data were excluded from the study.

Results

A total of 84 pregnancies involving 87 fetuses (9 siblings) were evaluated. The median gestation age was 20 weeks (range 12–41). The evaluation based on the ReCoDe system revealed that intrauterine death was mainly associated with placental diseases (n?=?63) and to a lesser extent with fetal malformations (n?=?15) or maternal diseases (n?=?4). Idiopathic cases were rare (n?=?2).

Conclusions

Placental examination is important for explaining intrauterine death because in most cases an association with placental diseases can be found but fetal malformation and maternal diseases must be taken into account.  相似文献   
95.
The physico-chemical and biological characteristics of Alkhumra hemorrhagic fever virus (AHFV) are not yet known. The present study describes the thermal stability of this virus at different temperatures for different periods. The kinetics of thermal inactivation were studied, linear regressions were plotted, the Arrhenius equation was applied, and the activation energy was calculated accordingly. Titers of the residual virus were determined in median tissue culture infective dose (TCID50), and the rate of destruction of infectivity at various temperatures was determined. Infectivity of AHFV was completely lost upon heating for 3 minutes at 60 °C and for 30 min at 56 °C. However, the virus could maintain 33.2 % of its titer after heating for 60 min at 45 °C and 32 % of its titer after heating for 60 min at 50 °C. In conclusion, AHFV is thermo-labile, and its inactivation follows first-order kinetics.  相似文献   
96.
97.
98.
Transcortical and cervical magnetic stimulation is a potential method of examining the central inspiratory pathway to phrenic motor neurons. The reliability and accuracy of this technique were studied. We performed magnetic stimulations of the cortex and cervical spinal cord with recording from both hemidiaphragms in 35 normal subjects using two different stimulation coils (90-mm circular coil and 70-mm figure-eight coil). Needle electrode recordings and ultrasound real-time documentation in 2 subjects excluded volume-conducted contaminations from adjacent chest wall and abdominal muscles. The effect of diaphragmatic facilitation (stimulation at the end of a deep breath) on latency, and amplitude were compared to the effect of hypothenar muscle facilitation. Normal ranges were established for: latency; central motor conduction time; amplitude; amplitude ratio between peripheral and both cortical and cervical amplitude; and excitability threshold. The latencies were similar for both coils. The amplitudes were significantly higher, and excitability thresholds significantly lower for the 90-mm circular coil, indicating that this coil is preferable for transcortical diaphragmatic stimulations. The effect of facilitation was greater for hypothenar than diaphragmatic recordings. There was excellent right-left agreement for all measurements. Transcortical and cervical magnetic stimulation with recording from the diaphragm can be used routinely to diagnose and monitor patients with impaired central respiratory drive. © 1996 John Wiley & Sons, Inc.  相似文献   
99.
OBJECTIVETo compare the outcomes of transapical transcatheter aortic valve replacement (TA-TAVR) and surgical aortic valve replacement (SAVR) using a large US population sample.METHODSThe U.S. National Inpatient Sample was queried for all patients who underwent TA-TAVR or SAVR during the years 2016−2017. The primary outcome was all-cause in-hospital mortality. Secondary outcomes were in-hospital stroke, pericardiocentesis, pacemaker insertion, mechanical ventilation, vascular complications, major bleeding, acute kidney injury, length of stay, and cost of hospitalization. Outcomes were modeled using multi-variable logistic regression for binary outcomes and generalized linear models for continuous outcomes.RESULTSA total of 1560 TA-TAVR and 44,280 SAVR patients were included. Patients who underwent TA-TAVR were older and frailer. Compared to SAVR, TA-TAVR correlated with a higher mortality (4.5% vs. 2.7%, effect size (SMD) = 0.1) and higher periprocedural complications. Following multivariable analysis, both TA-TAVR and SAVR had a similar adjusted risk for in-hospital mortality. TA-TAVR correlated with lower odds of bleeding with (adjusted OR (aOR) = 0.26; 95% CI: 0.18−0.38;P < 0.001), and a shorter length of stay (adjusted mean ratio (aMR) = 0.77; 95% CI: 0.69−0.84; P < 0.001), but higher cost (aMR = 1.18; 95% CI: 1.10−1.28; P < 0.001). No significant differences in other study outcomes. In subgroup analysis, TA-TAVR in patients with chronic lung disease had higher odds for mortality (aOR = 3.11; 95%CI: 1.37−7.08; P = 0.007). CONCLUSIONThe risk-adjusted analysis showed that TA-TAVR has no advantage over SAVR except for patients with chronic lung disease where TA-TAVR has higher mortality.

Trans-apical aortic valve replacement (TA-TAVR) is typically reserved for patients who have unfavorable transfemoral approach.[1] Several studies investigated the clinical outcomes of transfemoral-(TF) TAVR vs. surgical aortic valve replacement (SAVR); but there is paucity of data about the outcomes of TA-TAVR compared to SAVR. The STACCATO trial was the first randomized controlled trial to compare TA-TAVR versus SAVR. Though it was small trial (included only 70 operable patients) and was terminated prematurely (due to major adverse events in the TA-TAVR), it heralded a better outcome of SAVR when compared to TA-TAVR.[2] Current trends in the U.S. show a steady decline in TA-TAVR procedures with a decrease in the rates of TAVR-related complications, such as stroke and need for pacemaker insertion. However, there has been no change in the risk of mortality or other peri-procedural complications.[3]In this study, we aim to elucidate the applicability and safety of TA-TAVR when compared with SAVR. To our knowledge, this is the first retrospective cohort in the literature that compares the outcomes of TA-TAVR vs. SAVR in a national sample representative of the U.S. population.  相似文献   
100.
A 3‐year‐old child presented with recurrent chest pain for 3 months, echocardiography showed a thorn inside the left ventricle, the patient was diagnosed with foreign body complicated with infective endocarditis and received proper treatment, and operation was performed after inflammatory reaction subsided.  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