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   69733篇
  免费   5223篇
  国内免费   109篇
耳鼻咽喉   510篇
儿科学   2671篇
妇产科学   2153篇
基础医学   7376篇
口腔科学   1338篇
临床医学   8614篇
内科学   13187篇
皮肤病学   1374篇
神经病学   7079篇
特种医学   2350篇
外科学   9084篇
综合类   1154篇
一般理论   56篇
预防医学   7171篇
眼科学   2767篇
药学   4160篇
中国医学   139篇
肿瘤学   3882篇
  2023年   2161篇
  2022年   2753篇
  2021年   2829篇
  2020年   3068篇
  2019年   2184篇
  2018年   2667篇
  2017年   2781篇
  2016年   2672篇
  2015年   2477篇
  2014年   4372篇
  2013年   4033篇
  2012年   3387篇
  2011年   3305篇
  2010年   2987篇
  2009年   2881篇
  2008年   2708篇
  2007年   2694篇
  2006年   2327篇
  2005年   2106篇
  2004年   1852篇
  2003年   1885篇
  2002年   1735篇
  2001年   1757篇
  2000年   1613篇
  1999年   1581篇
  1998年   799篇
  1997年   747篇
  1996年   680篇
  1995年   545篇
  1994年   508篇
  1993年   378篇
  1992年   812篇
  1991年   725篇
  1990年   688篇
  1989年   661篇
  1988年   563篇
  1987年   300篇
  1986年   168篇
  1985年   194篇
  1984年   223篇
  1983年   177篇
  1982年   171篇
  1981年   158篇
  1980年   159篇
  1979年   140篇
  1978年   141篇
  1977年   123篇
  1976年   104篇
  1975年   120篇
  1974年   115篇
排序方式: 共有10000条查询结果,搜索用时 328 毫秒
1.
Objective: Since the COVID-19 pandemic, many governments globally have introduced policy measures to contain the spread of the virus. Popular COVID-19 containment measures include lockdowns of various forms (aggregated into government response stringency index [GRSI]) and handwashing (HWF). The effectiveness of these policy measures remains unclear in the academic literature. This study, therefore, examines the effect of government policy stringency and handwashing on total daily reported COVID-19 cases.Method: We use a comprehensive dataset of 176 countries to investigate the effect of government policy stringency and handwashing on daily reported COVID-19 cases. In this study, we apply the Lewbel (2012) two-stage least squares technique to control endogeneity.Results: Our results indicated that GRSI significantly contributes to the increase in the total and new confirmed cases of COVI-19. Sensitivity analyses revealed that the 1st, 4th, and 5th quintiles of GRIS significantly reduce total confirmed cases of COVID-19. Also, the result indicated that while the 1st quintile of GRIS contributes significantly to reducing the new confirmed cases of COVID-19, the 3rd, 4th, and 5th quintiles of GRSI contribute significantly to increasing the new confirmed cases of COVID-19. The results indicated that HWF reduces total and new confirmed cases of COVID-19; however, such effect is not robust to income and regional effects. Nonlinear analysis revealed that while GRSI has an inverted U-shaped relationship with total and new confirmed cases of COVID-19, HWF has a U-shaped relationship.Conclusion: We suggest that policymakers should focus on raising awareness and full engagement of all members of society in implementing public health policies rather than using stringent lockdown measures.  相似文献   
2.
3.
  1. Download : Download high-res image (173KB)
  2. Download : Download full-size image
  相似文献   
4.
5.
6.
《Clinical therapeutics》2022,44(3):403-417.e6
PurposeEntecavir (ETV) and tenofovir disoproxil fumarate (TDF) are both recommended as first-line treatments for patients with chronic hepatitis B virus (CHB) infection according to international HBV treatment guidelines. However, recent studies reported conflicting results regarding the preferred antiviral in the prevention of hepatocellular carcinoma (HCC). This cohort study aimed to investigate this issue by using Taiwan's National Health Insurance Research Database, wherein a “finite” but not life-long treatment policy was applied.MethodsFrom January 2008 to December 2013, a total of 12,388 consecutive adult patients with CHB who received a finite course of TDF treatment (n = 1250) or ETV treatment (n = 11,138) were analyzed through screening for study eligibility followed by the 1:4 propensity score matching method.FindingsIn the entire cohort, the annual incidence and survival between the ETV and TDF groups were not significantly different regarding HCC occurrence (2.05 vs 2.74 per 100 patient-years [PY]; P = 0.055; hazard ratio [HR], 0.975; log-rank, P = 0.966), cirrhosis-related complications (1.9 vs 2.4 per 100 PY; P = 0.149; HR, 0.869; log-rank, P = 0.388), or all-cause mortality (2.16 vs 1.6 per 100 PY; P = 0.119; HR, 0.831; log-rank, P = 0.342), respectively. Propensity score matching analyses yielded similar results regarding HCC occurrence, cirrhosis-related complications, and all-cause mortality. In addition, these findings were consistently reproduced in the subgroups of patients with chronic hepatitis and cirrhosis that developed before antiviral treatment.ImplicationsETV and TDF did not significantly differ in prevention of HCC occurrence or reduction of cirrhosis-related complications and all-cause mortality in patients with CHB receiving a finite period of treatment.  相似文献   
7.
For supersaturating formulations of BCS-II compounds, which by definition have high intestinal permeability, a closed USP apparatus does not provide the necessary absorptive conditions during dissolution. To address this, an artificial gut simulator (AGS) has been constructed consisting of a 2.5 mL donor compartment in which a hollow fiber-based absorption module is suspended. Drug from donor diffuses across the hollow fiber membrane to be absorbed by the continuously flowing intraluminal receiver fluid. The membrane surface area and intraluminal fluid flow rate are tuned to obtain the physiologically observed absorption rate constant for a weakly basic, poorly water-soluble model compound, ketoconazole (KTZ). Supersaturated solutions of KTZ were generated in the donor in pH 6.5 phosphate buffer by the pH-shift method in the absence (closed system, control) and presence (open system, biorelevant) of an optimally or suboptimally tuned absorption module. Drug concentrations in the donor and intraluminal fluids were determined by in-line UV spectroscopy. The presence of an absorptive sink reduced the supersaturated solution's crystallization propensity, more so in the case of the optimally tuned AGS. This study demonstrates the significance of simulating absorption of drug at a physiological rate during dissolution studies, especially to predict the performance of formulations of BCS-II drugs.  相似文献   
8.
Ventricular tachycardia (VT) is a potentially fatal cardiac rhythm disorder. Implantable cardioverter defibrillators (ICDs) are the primary management strategy for VT and have been shown to reduce the incidence of death but, ICDs do not reduce VT recurrences. Further, mounting evidence indicates that high VT burden, defined as the cumulative number of recurrent VTs or ICD shocks, is associated with an elevated risk of death; however, it is unclear if high VT burden is a cause of death or a marker of severe heart disease. Proposed mechanisms for a causal pathway suggest that multiple VT episodes or potential deleterious effects from ICDs might alter the myocardium of the ventricles to induce worsening heart disease, which might translate to an increased risk of mortality. In this review, we present the evidence to support association and causation hypotheses for the relationship between VT burden and risk of mortality and indicate potential gaps in evidence. Overall, there is insufficient evidence to prove causal hypotheses for the relationship between VT burden and mortality. Consistent definitions for VT burden, randomized controlled trials that assess the relationship between VT burden and mortality, and observational studies that capture VT burden are warranted to investigate if a potential causal relationship exists.  相似文献   
9.
10.
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