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   2931篇
  免费   556篇
  国内免费   52篇
耳鼻咽喉   8篇
儿科学   39篇
妇产科学   26篇
基础医学   129篇
口腔科学   21篇
临床医学   255篇
内科学   256篇
皮肤病学   7篇
神经病学   61篇
特种医学   74篇
外科学   1229篇
综合类   261篇
一般理论   9篇
预防医学   876篇
眼科学   15篇
药学   168篇
中国医学   56篇
肿瘤学   49篇
  2024年   1篇
  2023年   69篇
  2022年   61篇
  2021年   205篇
  2020年   262篇
  2019年   218篇
  2018年   187篇
  2017年   210篇
  2016年   159篇
  2015年   150篇
  2014年   200篇
  2013年   226篇
  2012年   156篇
  2011年   174篇
  2010年   125篇
  2009年   129篇
  2008年   140篇
  2007年   92篇
  2006年   88篇
  2005年   97篇
  2004年   84篇
  2003年   70篇
  2002年   43篇
  2001年   42篇
  2000年   39篇
  1999年   38篇
  1998年   34篇
  1997年   33篇
  1996年   10篇
  1995年   23篇
  1994年   13篇
  1993年   18篇
  1992年   10篇
  1991年   18篇
  1990年   9篇
  1989年   16篇
  1988年   7篇
  1987年   18篇
  1986年   14篇
  1985年   8篇
  1984年   12篇
  1983年   12篇
  1982年   6篇
  1981年   5篇
  1980年   6篇
  1978年   1篇
  1975年   1篇
排序方式: 共有3539条查询结果,搜索用时 46 毫秒
91.
目的:在住院药房开展降低针剂内部调配差错的品管圈活动,提升药事服务质量,提高药学专业人员的自我管理意识和解决问题的能力,保证临床用药安全有效. 方法:通过药师自发组成品管圈,找出针剂内部调配差错的主要原因,运用多种品管方法制定对策,依循"PDCA循环"开展各项活动. 结果:住院药房在开展品管圈活动之后,针剂内部调剂差错率由活动前的37.57%降到16.53%,工作环境与服务得到了改善.结论:住院药房开展品管圈活动能有效地降低住院药房针剂内部调配差错率,同时通过品管圈这种自下而上的管理方法,提高了圈员的自我管理能力以及病区对住院药房的满意度,最大限度地保障了患者的用药安全,和谐药护患关系.  相似文献   
92.
介绍了一套医院处理突发事件的应急预案及调配制度,系统阐述了应急设备保障中心的具体构成及运行模式.结合实践经验,证明了成立应急设备保障中心是合理分配医疗资源、充分发挥设备效益、提高设备使用率的有效措施之一.从信息化、应用培训、资源配置、消毒维护等4个方面分析了保障中心存在的问题,并提出了相应的对策和解决办法,以期提高急救设备的使用率,避免设备的重复购置和盲目引进,初步达到资源共享的目的.  相似文献   
93.
Background : Human apolipoprotein H ( &#103 2 -glycoprotein I, apoH, protein; APOH, gene) is a single-chain glycoprotein that has been implicated in several metabolic pathways, including lipid metabolism, coagulation and production of antiphospholipid antibodies and many disease phenotypes. The structural, molecular and genetic bases of APOH have been studied in detail but population studies, especially from the Indian sub-continent, are limited. Objective : This study seeks to enlarge our understanding of APOH genetic diversity in human populations from different regions and social groups of India. Also, we examine the level and extent of genetic variation at this locus in world populations and its utility as a population genetic marker. Subjects and methods : Blood samples from 1381 unrelated and randomly selected individuals were screened for APOH genetic polymorphism. Eleven populations from North India (Brahmins, Banias, Jat Sikhs, Khatris, Scheduled Castes, Lobanas and Rajputs), West India (Brahmin and Patels) and Central India (Brahmins and Baiga tribe) were studied for APOH polymorphism using isoelectric focusing. Allele frequencies were calculated by the gene counting method. The results were statistically evaluated using chi-square statistics for regional and ethnic variation. Genetic distances were computed on Indian populations to determine the population affinities. Correspondence analysis was used to assess ethnic variation in world populations. Results : An interesting and wide genetic variation at this locus was observed in Indian populations. The frequency distribution of three observed alleles ranged from 0.034 to 0.091 for APOH*1, 0.852 to 0.917 for APOH*2 and 0.027 to 0.075 for APOH*3. The world's highest APOH*2 allele frequency was observed in the Patel (0.917) caste group from West India. Conclusions : Overall, the observed variation at this locus in Indian populations is comparable to many Caucasian populations. An analysis of world populations showed that APOH is a useful genetic marker for population and anthropological studies.  相似文献   
94.
《Dental materials》2020,36(9):1201-1213
ObjectiveTo evaluate the influence of light emitted from two Polywave®, LED light-curing units (LCU) on in vivo pulp temperature (PT) rise and signs of acute inflammatory response in pulps of human premolar having deep Class V preparations.MethodsSixty intact, first premolars from 15 volunteers requiring extraction received infiltrative anesthesia. A sterile thermocouple probe was inserted within the pulp tissue through a minute occlusal pulp exposure in only 45 teeth (n = 9) to continuously monitor PT (°C). A deep buccal Class V preparation was created, and the surface was exposed to light from a commercial Polywave LCU (Bluephase 20i (20i), Ivoclar Vivadent) or from an experimental LCU (Exp) using the exposure modes (EM): 1s/Exp and 2s/Exp, 10s/20i, 20s/20i, and 60s/20i. Peak PT and PT rise values above baseline (ΔT) data were evaluated using a one-way ANOVA followed by Tukey’s post-hoc test (α = 5%). Teeth used for histological and immunohistochemical analyses (n = 3) were extracted approximately 2 h after exposure to the LCU.ResultsNo significant difference in peak PT and ΔT values was noted between 2s/Exp and 20s/20i groups, which both exhibited higher values than 1s/Exp and 10s/20i groups (p < 0.001). Dilated and congested blood vessels were seen after exposure to 1s/Exp, 2s/Exp, or 60s/20i EMs. The expression of IL-1β and TNF-α tended to be more intense when higher irradiance was delivered.SignificanceAlthough higher irradiance delivered over a short exposure caused lower PT rise than 5.5 °C, such EMs should be used with caution, as they have more potential to harm the pulp tissue.  相似文献   
95.
A ph mesh refinement method for optimal control   总被引:1,自引:0,他引:1       下载免费PDF全文
A mesh refinement method is described for solving a continuous‐time optimal control problem using collocation at Legendre–Gauss–Radau points. The method allows for changes in both the number of mesh intervals and the degree of the approximating polynomial within a mesh interval. First, a relative error estimate is derived based on the difference between the Lagrange polynomial approximation of the state and a Legendre–Gauss–Radau quadrature integration of the dynamics within a mesh interval. The derived relative error estimate is then used to decide if the degree of the approximating polynomial within a mesh should be increased or if the mesh interval should be divided into subintervals. The degree of the approximating polynomial within a mesh interval is increased if the polynomial degree estimated by the method remains below a maximum allowable degree. Otherwise, the mesh interval is divided into subintervals. The process of refining the mesh is repeated until a specified relative error tolerance is met. Three examples highlight various features of the method and show that the approach is more computationally efficient and produces significantly smaller mesh sizes for a given accuracy tolerance when compared with fixed‐order methods. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   
96.
Most distributed parameter control problems involve manipulation within the spatial domain. Such problems arise in a variety of applications including epidemiology, tissue engineering, and cancer treatment. This paper proposes an approach to solve a state‐constrained spatial field control problem that is motivated by a biomedical application. In particular, the considered manipulation over a spatial field is described by partial differential equations (PDEs) with spatial frequency constraints. The proposed optimization algorithm for tracking a reference spatial field combines three‐dimensional Fourier series, which are truncated to satisfy the spatial frequency constraints, with exploitation of structural characteristics of the PDEs. The computational efficiency and performance of the optimization algorithm are demonstrated in a numerical example. In the example, the spatial tracking error is shown to be almost entirely due to the limitation on the spatial frequency of the manipulated field. The numerical results suggest that the proposed optimal control approach has promise for controlling the release of macromolecules in tissue engineering applications.  相似文献   
97.
Extensively burned patients receive iterative blood transfusions and skin allografts that often lead to HLA sensitization, and potentially impede access to vascularized composite allotransplantation (VCA). In this retrospective, single‐center study, anti‐HLA sensitization was measured by single‐antigen‐flow bead analysis in patients with deep, second‐ and third‐degree burns over ≥40% total body surface area (TBSA). Association of HLA sensitization with blood transfusions, skin allografts, and pregnancies was analyzed by bivariate analysis. The eligibility for transplantation was assessed using calculated panel reactive antibodies (cPRA). Twenty‐nine patients aged 32 ± 14 years, including 11 women, presented with a mean burned TBSA of 54 ± 11%. Fifteen patients received skin allografts, comprising those who received cryopreserved (n = 3) or glycerol‐preserved (n = 7) allografts, or both (n = 5). An average 36 ± 13 packed red blood cell (PRBC) units were transfused per patient. In sera samples collected 38 ± 13 months after the burns, all patients except one presented with anti‐HLA antibodies, of which 13 patients (45%) had complement‐fixing antibodies. Eighteen patients (62%) were considered highly sensitized (cPRA≥85%). Cryopreserved, but not glycerol‐preserved skin allografts, history of pregnancy, and number of PRBC units were associated with HLA sensitization. Extensively burned patients may become highly HLA sensitized during acute care and hence not qualify for VCA. Alternatives to skin allografts might help preserve their later access to VCA.  相似文献   
98.

Background

Cervical spondylosis is now recognised as the leading cause of myelopathy and spinal cord dysfunction worldwide. Chronic spinal cord compression results in chronic inflammation, cellular apoptosis, and microvacular insufficiency, which are thought to the biologic basis for cervical spondylotic myelopathy (CSM).

Questions/Purposes

Our purpose was to address the key principles of CSM, including natural history and presentation, pathogenesis, optimal surgical approach, results and complication rates of posterior surgical approaches for CSM so that the rationale for addressing CSM by a posterior approach can be fully understood.

Methods

We conducted a systematic search of PubMed/MEDLINE and the Cochrane Collaboration Library for literature published through February 2014 to identify articles that evaluated CSM and its management. Reasons for exclusion included patients with ossification of the posterior longitudinal ligament (OPLL), patients with degenerative disc disease without CSM, and patients with spine tumor, trauma and infection. Meeting abstracts/proceedings, white articles and editorials were additionally excluded.

Results

The search strategy yielded 1,292 articles, which was reduced to 52 articles, after our exclusion criteria were introduced. CSM is considered to be a surgical disorder due to its progressive nature. There is currently no consensus in the literature whether multilevel spondylotic compression is best treated via an anterior or posterior surgical approach.

Conclusion

Multilevel CSM may be safely and effectively treated using a posterior approach, either by laminoplasty or with a laminectomy and fusion technique.

Electronic supplementary material

The online version of this article (doi:10.1007/s11420-014-9425-5) contains supplementary material, which is available to authorized users.  相似文献   
99.
In June 2013, a change to the liver waitlist priority algorithm was implemented. Under Share 35, regional candidates with MELD ≥ 35 receive higher priority than local candidates with MELD < 35. We compared liver distribution and mortality in the first 12 months of Share 35 to an equivalent time period before. Under Share 35, new listings with MELD ≥ 35 increased slightly from 752 (9.2% of listings) to 820 (9.7%, p = 0.3), but the proportion of deceased‐donor liver transplants (DDLTs) allocated to recipients with MELD ≥ 35 increased from 23.1% to 30.1% (p < 0.001). The proportion of regional shares increased from 18.9% to 30.4% (p < 0.001). Sharing of exports was less clustered among a handful of centers (Gini coefficient decreased from 0.49 to 0.34), but there was no evidence of change in CIT (p = 0.8). Total adult DDLT volume increased from 4133 to 4369, and adjusted odds of discard decreased by 14% (p = 0.03). Waitlist mortality decreased by 30% among patients with baseline MELD > 30 (SHR = 0.70, p < 0.001) with no change for patients with lower baseline MELD (p = 0.9). Posttransplant length‐of‐stay (p = 0.2) and posttransplant mortality (p = 0.9) remained unchanged. In the first 12 months, Share 35 was associated with more transplants, fewer discards, and lower waitlist mortality, but not at the expense of CIT or early posttransplant outcomes.  相似文献   
100.
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