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   3968篇
  免费   471篇
  国内免费   462篇
  2024年   5篇
  2023年   113篇
  2022年   99篇
  2021年   155篇
  2020年   188篇
  2019年   189篇
  2018年   202篇
  2017年   167篇
  2016年   211篇
  2015年   177篇
  2014年   218篇
  2013年   317篇
  2012年   163篇
  2011年   258篇
  2010年   146篇
  2009年   230篇
  2008年   205篇
  2007年   201篇
  2006年   185篇
  2005年   156篇
  2004年   153篇
  2003年   119篇
  2002年   113篇
  2001年   100篇
  2000年   68篇
  1999年   61篇
  1998年   60篇
  1997年   60篇
  1996年   60篇
  1995年   57篇
  1994年   46篇
  1993年   51篇
  1992年   38篇
  1991年   38篇
  1990年   24篇
  1989年   29篇
  1988年   22篇
  1987年   12篇
  1986年   14篇
  1985年   19篇
  1984年   29篇
  1983年   25篇
  1982年   30篇
  1981年   14篇
  1980年   11篇
  1979年   14篇
  1977年   10篇
  1976年   10篇
  1975年   6篇
  1973年   10篇
排序方式: 共有4901条查询结果,搜索用时 15 毫秒
91.

Background

Fluticasone furoate (FF)/vilanterol (VI) 100/25 mcg is a once-daily inhaled corticosteroid (ICS)/long-acting beta2 agonist (LABA) treatment approved in the United States, Canada and Europe for the long-term maintenance therapy of COPD. We report data from mixed treatment comparisons (MTC) of once-daily FF/VI against established twice-daily ICS/LABA combination therapies on clinical efficacy outcomes.

Methods

Data from 33 parallel-group randomised controlled trials (RCTs) of ICS/LABAs, of ≥8 weeks’ duration in patients ≥12 years of age with COPD, identified by systematic review, were analysed using covariate-adjusted Bayesian hierarchical models for three efficacy outcomes. Lung function, assessed by change from baseline in forced expiratory volume in one second (FEV1), was the outcome of primary interest (n = 28 studies). Secondary objectives were assessment of annual rate of moderate/severe exacerbations (n = 15) and patient-reported health status, measured by change from baseline in St George’s Respiratory Questionnaire (SGRQ) Total score (n = 20). Overall, 25 different treatments were included in the MTC; we report findings, including probabilities of non-inferiority, for comparisons of once-daily FF/VI 100/25 mcg with twice-daily fluticasone propionate (FP)/salmeterol (SAL) 500/50 mcg and budesonide (BUD)/formoterol (FORM) 400/12 mcg.

Results

For FEV1, FF/VI 100/25 mcg demonstrated >99% probability of non-inferiority to FP/SAL 500/50 mcg and BUD/FORM 400/12 mcg using a 50 mL margin. For annual rate of moderate/severe exacerbations, FF/VI 100/25 mcg demonstrated 73% and 77% probability of non-inferiority to FP/SAL 500/50 mcg and BUD/FORM 400/12 mcg, respectively, using a 10% rate ratio margin. For SGRQ Total score, the corresponding probabilities of non-inferiority were 99% and 98%, respectively, on a 2-unit margin. Significant covariate effects were identified: increased age was associated with deterioration in FEV1 and reduced exacerbation frequency; shorter study duration was associated with reduced exacerbation frequency.

Conclusions

FF/VI 100/25 mcg was comparable with corresponding doses of FP/SAL and BUD/FORM on lung function and health status outcomes. Non-inferiority on moderate/severe exacerbation rate was not demonstrated to the same degree of confidence, though observed rates were similar. Model limitations include a weak treatment network for the exacerbation analysis and variability across the included studies. Our data support previous RCT findings suggesting that the efficacy of FF/VI 100/25 mcg on lung function and health status in COPD is comparable with twice-daily ICS/LABAs.

Electronic supplementary material

The online version of this article (doi:10.1186/s12931-015-0184-8) contains supplementary material, which is available to authorized users.  相似文献   
92.
Resource constraints in developing countries compel policy makers to ration the provision of healthcare services. This article examines one such set of Guidelines: A patient dialysing in the state sector in South Africa may not refuse renal transplantation when a kidney becomes available. Refusal of transplantation can lead to exclusion from the state‐funded dialysis programme. This Guideline is legally acceptable as related to Constitutional stipulations which allow for rationing healthcare resources in South Africa. Evaluating the ethical merit of the Guideline, and exploring the ethical dilemma it poses, proves a more complex task. We examine the actions of healthcare professionals as constrained by the Guideline. From a best interests framework, we argue that in these circumstances directing patient decision making (pressurising a patient to undergo renal transplantation) is not necessarily unethical or unacceptably paternalistic. We then scrutinise the guideline itself through several different ethical ‘lenses’. Here, we argue that bioethics does not provide a definitive answer as to the moral merit of rationing dialysis under these circumstances, however it can be considered just in this context. We conclude by examining a potential pitfall of the Guideline: Unwilling transplant recipients may not comply with immunosuppressive medication, which raises questions for policies based on resource management and rationing.  相似文献   
93.
Primary osteogenic sarcoma of the breast is a rare neoplasm, diagnosed mainly by pathohistological and immunohistochemical analysis.We hereby present a case of primary osteogenic sarcoma in the right breast of a 62-year-old woman with synchronous appearance of an invasive ductal carcinoma. Clinical findings are manifested with two separate painless formations 2.5 cm/2 cm and 1.5 cm/1 cm in size, located on the border of the upper and lower lateral quadrant of the right breast. No axillary lymphadenopathy was diagnosed. The pathohistological and immunohistochemistry findings of both tumors revealed a synchronous manifestation of two distinct neoplasms – epithelial and non-epithelial. Multimodality treatment consisted of Patey''s radical mastectomy; 3 cycles of adjuvant chemotherapy; postoperative 50 Gy radiotherapy to the chest wall followed by additional 3 cycles of chemotherapy and anti-estrogen hormonotherapy.Due to the rarity of osteogenic mammary sarcoma, even more so in a combination with epithelial breast tumors, its clinical features are unclear and optimal treatment remains controversial. Considering the poor prognosis of the combination of both malignomas, we discuss a number of diagnostic and therapeutic issues.  相似文献   
94.
Little is known regarding the effect of the graphene lateral size on the electrochemical performance of hybrid graphene electrode. This work examines the electrochemical performance of a flexible hybrid supercapacitor electrode composed of ultralarge graphene oxide (UGO; mean lateral size of 47 ± 22 μm) and vanadium dioxide (VO2) nanobelts, referring to a reference electrode composed of small scale graphene oxide (SGO; mean lateral size of 0.8 ± 0.5 μm) and VO2.Thermal treatment converts UGO/VO2 and SGO/VO2 to URGO/VO2 (denoted VURGO) and SRGO/VO2 (denoted VSRGO) electrodes, respectively. The sheet resistance of the VURGO film (0.57 ± 0.03 kΩ sq.–1) was two orders of magnitude lower than that of the VSRGO (55.74 ± 9.35 kΩ sq.–1). The VURGO hybrid electrode showed a specific capacitance of 769 F g?1, which was significantly better than the corresponding values for the VSRGO electrode (385 F/g). These results support the notion that the use of ultralarge graphene sheets (≈22 500 μm2) lowers the intersheet resistance due to the presence of fewer intersheet tunneling barriers. This article highlights the potential utility of URGO (as a conductive support) in hybrid electrode containing VO2 nanobelts for high performance flexible hybrid supercapacitor.  相似文献   
95.
The addition of polystyrene (PS), a typical insulator, is empirically shown to increase the power conversion efficiencies (PCEs) of a solution‐deposited bulk heterojunction (BHJ) molecular blend film used in solar cell fabrication: p‐DTS(FBTTh2)2/PC71BM. The performance is further improved by small quantities of diiodooctane (DIO), an established solvent additive. In this study, how the addition of PS and DIO affects the film formation of this bulk heterojunction blend film are probed via in situ monitoring of absorbance, thickness, and crystallinity. PS and DIO additives are shown to promote donor crystallite formation on different time scales and through different mechanisms. PS‐containing films retain chlorobenzene solvent, extending evaporation time and promoting phase separation earlier in the casting process. This extended time is insufficient to attain the morphology for optimal PCE results before the film sets. Here is where the presence of DIO comes into play: its low vapor pressure further extends the time scale of film evolution and allows for crystalline rearrangement of the donor phase long after casting, ultimately leading to the best BHJ organization.  相似文献   
96.
97.
98.
99.
The text describes a preventive clinical trial with drug treatment in a very rare neurodegenerative disease (Fatal familial Insomnia, FFI) designed with the help of individuals at genetic risk of developing the disease, asymptomatic carriers, who have agreed to be exposed over a 10-year period to doxycycline, an antibiotic with anti-prion activity. At least 10 carriers of the FFI mutation over 42 y old will be treated with doxycycline (100 mg/die) and the incidence of the disease will be compared to that of an historical dataset. For ethical reasons a randomized, double-blind, placebo-controlled trial was not feasible, however the study design and the statistical analysis ensure the scientific value of the results. This approach might represent an important breakthrough in terms of potential therapy and knowledge of rare diseases that could give some hopes to these neglected patients.  相似文献   
100.
Helicobacter pylori (H. pylori) infection has been associated with gastric disorders. The situation of H. pylori infection in China—where a high prevalence of H. pylori infection, a high incidence of gastric cancer, and widespread resistance to clarithromycin, metronidazole, and levofloxacin exist—is quite different from that in Western countries. In order for Chinese clinicians to better manage H. pylori infection, a Chinese Study Group on H. pylori published four consensus reports regarding the management of H. pylori infection in China between 1999 and 2012. The eradication rate with standard triple therapy was <80% in most areas of China. Bismuth is available in China, and bismuth‐containing quadruple therapy has been shown to produce a high eradication rate; thus, bismuth quadruple therapy could be recommended both as an initial and as a rescue therapy in China. There is no advantage of sequential therapy over triple therapy in Chinese patients, but the efficacy of concomitant therapy must be studied further. This review introduces the epidemiology, diagnosis, indicators, and therapies for the eradication of H. pylori in China in recent years.  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