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   337978篇
  免费   27262篇
  国内免费   11603篇
耳鼻咽喉   2630篇
儿科学   5350篇
妇产科学   3533篇
基础医学   52224篇
口腔科学   6078篇
临床医学   28904篇
内科学   53656篇
皮肤病学   4086篇
神经病学   21098篇
特种医学   7196篇
外国民族医学   74篇
外科学   25622篇
综合类   48713篇
现状与发展   28篇
一般理论   31篇
预防医学   20083篇
眼科学   5975篇
药学   45517篇
  58篇
中国医学   15327篇
肿瘤学   30660篇
  2024年   785篇
  2023年   5409篇
  2022年   11600篇
  2021年   14780篇
  2020年   11769篇
  2019年   10990篇
  2018年   10673篇
  2017年   10585篇
  2016年   10791篇
  2015年   11837篇
  2014年   18420篇
  2013年   20775篇
  2012年   17832篇
  2011年   20646篇
  2010年   17443篇
  2009年   17554篇
  2008年   17262篇
  2007年   17472篇
  2006年   15850篇
  2005年   14734篇
  2004年   12554篇
  2003年   11244篇
  2002年   8667篇
  2001年   7870篇
  2000年   6519篇
  1999年   6011篇
  1998年   4869篇
  1997年   4413篇
  1996年   4240篇
  1995年   3882篇
  1994年   3481篇
  1993年   3080篇
  1992年   2638篇
  1991年   2362篇
  1990年   1989篇
  1989年   1768篇
  1988年   1689篇
  1987年   1337篇
  1986年   1116篇
  1985年   1544篇
  1984年   1530篇
  1983年   1032篇
  1982年   1136篇
  1981年   926篇
  1980年   788篇
  1979年   643篇
  1978年   475篇
  1977年   392篇
  1976年   417篇
  1975年   277篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
92.

Background

Chronic limb-threatening ischemia (CLTI), defined as ischemic rest pain or tissue loss secondary to arterial insufficiency, is caused by multilevel arterial disease with frequent, severe infrageniculate disease. The rise in CLTI is in part the result of increasing worldwide prevalence of diabetes, renal insufficiency, and advanced aging of the population. The aim of this study was to compare a bypass-first with an endovascular-first revascularization strategy in patients with CLTI due to infrageniculate arterial disease.

Methods

We reviewed the American College of Surgeons National Surgical Quality Improvement Program targeted lower extremity revascularization database from 2012 to 2015 to identify patients with CLTI and isolated infrageniculate arterial disease who underwent primary infrageniculate bypass or endovascular intervention. We excluded patients with a history of ipsilateral revascularization and proximal interventions. The end points were major adverse limb event (MALE), major adverse cardiovascular event (MACE), amputation at 30 days, reintervention, patency, and mortality. Multivariable logistic regression was used to determine the association of a bypass-first or an endovascular-first intervention with outcomes.

Results

There were 1355 CLTI patients undergoing first-time revascularization to the infrageniculate arteries (821 endovascular-first revascularizations and 534 bypass-first revascularizations) identified. There was no significant difference in adjusted rate of 30-day MALE in the bypass-first vs endovascular-first revascularization cohort (9% vs 11.2%; odds ratio [OR], 0.73; 95% confidence interval [CI], 0.50-1.08). However, the incidence of transtibial or proximal amputation was lower in the bypass-first cohort (4.3% vs 7.4%; OR, 0.60; CI, 0.36-0.98). Patients with bypass-first revascularization had higher wound complication rates (9.7% vs 3.7%; OR, 2.75; CI, 1.71-4.42) compared with patients in the endovascular-first cohort. Compared with the endovascular-first cohort, the incidence of 30-day MACE was significantly higher in bypass-first patients (6.9% vs 2.6%; adjusted OR, 3.88; CI, 2.18-6.88), and 30-day mortality rates were 3.23% vs 1.8% (adjusted OR, 2.77; CI, 1.26-6.11). There was no difference in 30-day untreated loss of patency, reintervention of treated arterial segment, readmissions, and reoperations between the two cohorts. In subgroup analysis after exclusion of dialysis patients, there was also no significant difference in MALE or amputation between the bypass-first and endovascular-first cohorts.

Conclusions

CLTI patients with isolated infrageniculate arterial disease treated by a bypass-first approach have a significantly lower 30-day amputation. However, this benefit was not observed when dialysis patients were excluded. The bypass-first cohort had a higher incidence of MACE compared with an endovascular-first strategy. These results reaffirm the need for randomized controlled trials, such as the Bypass versus Angioplasty in Severe Ischaemia of the Leg (BASIL-2) trial and Best Endovascular vs Best Surgical Therapy in Patients with Critical Limb Ischemia (BEST-CLI), to provide level 1 evidence for the role of endovascular-first vs bypass-first revascularization strategies in the treatment of this population of challenging patients.  相似文献   
93.
《Value in health》2020,23(10):1340-1348
ObjectivesWe applied principles for conducting economic evaluations of factorial trials to a trial-based economic evaluation of a cluster-randomized 2 × 2 × 2 factorial trial. We assessed the cost-effectiveness of atorvastatin, omega-3 fish oil, and an action-planning leaflet, alone and in combination, from a UK National Health Service perspective.MethodsThe Atorvastatin in Factorial With Omega EE90 Risk Reduction in Diabetes (AFORRD) Trial randomized 800 patients with type 2 diabetes to atorvastatin, omega-3, or their respective placebos and randomized general practices to receive a leaflet-based action-planning intervention designed to improve compliance or standard care. The trial was conducted at 59 UK general practices. Sixteen-week outcomes for each trial participant were extrapolated for 70 years using the United Kingdom Prospective Diabetes Study Outcomes Model v2.01. We analyzed the trial as a 2 × 2 factorial trial (ignoring interactions between action-planning leaflet and medication), as a 2 × 2 × 2 factorial trial (considering all interactions), and ignoring all interactions.ResultsWe observed several qualitative interactions for costs and quality-adjusted life-years (QALYs) that changed treatment rankings. However, different approaches to analyzing the factorial design did not change the conclusions. There was a ≥99% chance that atorvastatin is cost-effective and omega-3 is not, at a £20 000/QALY threshold.ConclusionsAtorvastatin monotherapy was the most cost-effective combination of the 3 trial interventions at a £20 000/QALY threshold. Omega-3 fish oil was not cost-effective, while there was insufficient evidence to draw firm conclusions about action planning. Recently-developed methods for analyzing factorial trials and combining parameter and sampling uncertainty were extended to estimate cost-effectiveness acceptability curves within a 2x2x2 factorial design with model-based extrapolation.  相似文献   
94.
95.
OBJECTIVES: To assess the effectiveness and safety of additional bedtime H2‐receptor antagonists (H2RAs) in suppressing nocturnal gastric acid breakthrough (NAB) via a systematic review. METHODS: Eligible trials were identified by searching the Cochrane Central Register of Controlled Trials (CENTRAL) (Cochrane Library Issue 2, 2004), MEDLINE (January 1966–June 2004), EMBASE (January 1980–June 2004) and CINAHL (January 1982–June 2004). Additional hand‐searching was conducted on the proceedings of correlated conferences, eight important Chinese journals and references of all included trials. All randomized controlled trials evaluating H2RAs for the control of NAB were eligible for inclusion. The systematic review was conducted using methods recommended by The Cochrane Collaboration. RESULTS: Only two randomized crossover studies, comprising 32 participants, met the inclusion criteria. Because the design, dosage and duration of the treatments were different between the studies, it was not possible to conduct meta‐analysis. There were no consistent conclusions found between the two included studies in evaluating H2RAs for the control of NAB. CONCLUSIONS: No implications for practice at this stage can be concluded. Appropriately designed large‐scale randomized controlled trials with long‐term follow up are needed to determine the effects of additional bedtime H2RAs in suppressing NAB.  相似文献   
96.
ZusammenfassungHintergrund Bedingt durch die intraoperative Katecholaminsekretion mit hämodynamischen Veränderungen, einem größeren Tumordurchmesser und einer deutlichen Neovaskularisation ist die Adrenalektomie beim Phäochromozytom im Vergleich zu anderen Nebennierenerkrankungen schwieriger und potenziell komplikationsträchtiger. Ziel unserer Studie war die Frage, ob das Risiko intraoperativer kardiovaskulärer Komplikationen durch das minimal-invasive Vorgehen potenziert wird.Patienten und Methodik Im Zeitraum zwischen Februar 1992 und Mai 2005 wurden in unserer Klinik 82 Eingriffe wegen eines Phäochromozytoms bei 71 Patienten durchgeführt. Davon wurden 8 (1) Patient(en) bi-(tri-)lateral adrenalektomiert und bei 2 Patienten erfolgte eine ipsilaterale Rezidivoperation. Eingeschlossen sind 5 weitere Patienten mit Rezidiv nach Erstoperation vor 1992. Sechsunddreißig Eingriffe erfolgten konventionell (transperitoneal n=35, retroperitoneal n=1) und 46 Operationen endoskopisch (transperitoneal n=28, retroperitoneal n=18), davon keine Konversion zum offenen Vorgehen.Ergebnisse Das mediane Alter zum Zeitpunkt der Operation betrug 45 (24–75) Jahre bei einer Anamnesedauer von 12 (0–180) Monaten. Die offen operierten Phäochromozytome waren mit 5,5 (1–19) cm vs. 3,5 (0,5–8) cm (endoskopisch) signifikant größer (p=0,0011). Patienten mit endoskopischer, insbesondere mit retroperitoneoskopischer Adrenalektomie hatten im Vergleich zum konventionellen Vorgehen intraoperativ höhere systolische und diastolische maximale Blutdruckwerte sowie Spitzen über 200 mmHg (statistisch nicht signifikant). Faktoren mit möglichem Einfluss auf intraoperative hämodynamische Veränderungen waren in der multivariaten Analyse das Geschlecht (p=0,0107), der operative Zugangsweg (p=0,0153), das Patientenalter (p=0,0364) und die Tumorgröße (p=0,0484). Die postoperative stationäre Verweildauer war nach endoskopischer Operation signifikant kürzer (p<0,0001).Schlussfolgerung Die endoskopische Adrenalektomie beim Phäochromozytom ist in der Routine ohne vermehrtes Risiko kardiovaskulärer Komplikationen die Methode der Wahl. Das offene Vorgehen sollte extraadrenalen Befunden oder sehr großen Tumoren mit Malignitätsverdacht vorbehalten bleiben.   相似文献   
97.
Condensation of thiourea 1 with diethyl malonate 2 in the presence of sodium methoxide furnished 4,6‐dihydroxy‐2‐mercaptopyrimidine 3 . Compound 3 on methylation with diazomethane followed by oxidation with H5IO6/CrO3 in ethyl acetate gave 4,6‐dimethoxy‐2‐methylsulphonylpyrimidine 5 . Compound 5 on condensation with 2‐mercapto‐6‐chlorobenzoic acid in the presence of a phase transfer catalyst, tetrabutylammonium bromide and sodium carbonate gave the title compound – pyrithiobac‐sodium 6 with an overall yield of > 35% starting from thiourea. Following the above standardized procedure, using [14C]‐thiourea in lieu of thiourea, 14C labelled product 6 , was synthesized with an overall radiochemical yield > 30% (with respect to [14C]‐thiourea) for further evaluations of environmental fate of 6 , in soils and plants. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   
98.
目的探讨谷氨酸是否能够影响腺苷A2A受体对一氧化氮合酶(NOS)活力的调节。方法用1000ng/ml脂多糖(LPS)刺激小胶质细胞,分别加入100nmol/L A2A受体激动剂CGS21680以及不同浓度的谷氨酸(0,1,0,25,0,5mmol/L)干预,观察NOS活力变化。结果LPS诱导NOS活力增高,激活A2A受体可以产生抑制作用;0,25及0.5mmoL/L谷氨酸和A2A受体激动剂同时存在时,NOS活力进一步增高。结论高浓度谷氨酸可逆转腺苷A2A受体激动剂抑制升高NOS活力的作用。  相似文献   
99.
100.
Many health-related research studies among Seventh-day Adventists (SDA) were published since 1958. Californian and Norwegian studies have shown that SDA have lower coronary mortality rates than the general population. This finding is usually attributed to the lifestyle advocated by the Seventh-day Adventist church with greater physical activity, lower median BMI, abstention from use of alcohol and tobacco, food habits characterized by a large intake of fruits, vegetables, cereal fiber, unsaturated fatty acids and a low consumption of saturated fats. The results about cancer incidence were discussed. Californian studies have shown significantly decreased relative risk in SDA than in the general population. Japanese studies have also reported lower risk of cancers in men with lifestyles similar to those of SDA. By contrast the Norwegian study of SDA has shown that the risk of cancer seems to be similar to that of the general population. Some studies reported a greater prevalence of type 2 diabetes in the non vegetarian SDA than the vegetarian. Compared with vegetarian, non vegetarian SDA reported more medication use, more chronic diseases, more hospitalizations and surgeries. Lifestyle choices of SDA as above described could prevent a great many coronary artery disease and type 2 diabetes. This lifestyle is now emphasized by French PNNS.  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