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   2907篇
  免费   205篇
  国内免费   30篇
耳鼻咽喉   29篇
儿科学   27篇
妇产科学   29篇
基础医学   480篇
口腔科学   42篇
临床医学   271篇
内科学   198篇
皮肤病学   24篇
神经病学   413篇
特种医学   102篇
外科学   151篇
综合类   410篇
预防医学   524篇
眼科学   69篇
药学   182篇
  5篇
中国医学   131篇
肿瘤学   55篇
  2024年   15篇
  2023年   42篇
  2022年   128篇
  2021年   131篇
  2020年   104篇
  2019年   83篇
  2018年   82篇
  2017年   80篇
  2016年   101篇
  2015年   109篇
  2014年   157篇
  2013年   234篇
  2012年   170篇
  2011年   185篇
  2010年   155篇
  2009年   135篇
  2008年   152篇
  2007年   132篇
  2006年   139篇
  2005年   122篇
  2004年   88篇
  2003年   82篇
  2002年   63篇
  2001年   46篇
  2000年   45篇
  1999年   27篇
  1998年   38篇
  1997年   32篇
  1996年   24篇
  1995年   40篇
  1994年   16篇
  1993年   19篇
  1992年   7篇
  1991年   20篇
  1990年   8篇
  1989年   14篇
  1988年   4篇
  1987年   11篇
  1986年   12篇
  1985年   13篇
  1984年   12篇
  1983年   14篇
  1982年   7篇
  1981年   9篇
  1980年   10篇
  1979年   5篇
  1978年   4篇
  1977年   6篇
  1976年   5篇
  1968年   1篇
排序方式: 共有3142条查询结果,搜索用时 15 毫秒
81.
Objective We hypothesized that the drinking behavior of adolescents in China is influenced by expectancies and self‐efficacy and that adolescents' cultural orientation towards western versus traditional Chinese values influences expectancies, self‐efficacy and drinking behavior, with western values leading to more dysfunctional patterns of beliefs and drinking, and that these beliefs are influenced by students' gender and school environment. Methods A total of 1020 high school students from Beijing completed the Chinese Adolescent Alcohol Expectancy, the Chinese Cultural Orientation and the Chinese Self‐regulation Self‐efficacy questionnaires. Results Results generally confirmed our hypotheses. Higher negative expectancies and higher self‐efficacy reduced the likelihood of drinking significantly. Higher positive expectancies increased the likelihood of regular drinking but not occasional drinking. Having western cultural orientation increased the likelihood of drinking. Higher levels of western cultural orientation also increased positive expectancies, lowered negative expectancies and lowered self‐efficacy. Having more western (less traditional) views towards traditional Chinese values decreased positive and negative expectancies. Gender influenced beliefs, with males having higher positive and lower negative expectancies, lower self‐efficacy and more traditional cultural orientation. Students in key and general schools had less traditional cultural orientation and key school students had higher self‐efficacy. Conclusions Results indicate that cultural orientation influences adolescent drinking and this influence is mediated partially through cultural orientation influences on adolescent drinking expectancies and self‐efficacy. Having more western and less traditional Chinese cultural orientation leads to more drinking, lower self‐efficacy for regulating drinking and more risk‐promoting alcohol expectancies.  相似文献   
82.
Numerical studies for polymer composites deposition additive manufacturing have provided significant insight promoting the rapid development of the technology. However, little of existing literature addresses the complex yet important polymer composite melt flow–fiber orientation coupling during deposition. This paper explores the effect of flow–fiber interaction for polymer deposition of 13 wt.% Carbon Fiber filled Acrylonitrile Butadiene Styrene (CF/ABS) composites through a finite-element-based numerical approach. The molten composite flow in the extrusion die plus a strand of the deposited bead contacting the deposition substrate is modelled using a 2D isothermal and incompressible Newtonian planar flow model, where the material deposition rate is ~110 mm/s simulating a large scale additive manufacturing process. The Folgar–Tucker model associated with the Advani–Tucker orientation tensor approach is adopted for the evaluation of the fiber orientation state, where the orthotropic fitted closure is applied. By comparing the computed results between the uncoupled and fully coupled solutions, it is found that the flow-orientation effects are mostly seen in the nozzle convergence zone and the extrusion-deposition transition zone of the flow domain. Further, the fully coupled fiber orientation solution is highly sensitive to the choice of the fiber–fiber interaction coefficient CI, e.g., assigning CI as 0.01 and 0.001 results in a 23% partial relative difference in the predicted elastic modulus along deposition direction. In addition, Structural properties of deposited CF/ABS beads based on our predicted fiber orientation results show favorable agreements with related experimental studies.  相似文献   
83.
目的:观察中西医结合序贯治疗对支气管哮喘患者的临床疗效。方法将128例支气管哮喘患者随机分为观察组与对照组,均分发作期、缓解期、稳定期三期序贯治疗。对照组64例予西医常规治疗,观察组64例在对照组基础上配合中药,应用中西医结合疗法,每一期疗程结束评价疗效。结果观察组在发作期病情平均缓解时间,以及肺功能指标、症状体征积分、临床总有效率、1年内复发率等方面与对照组比较,差异有统计学意义(P ﹤0.05,P ﹤0.01)。结论中西医结合序贯疗法能有效改善哮喘患者肺功能,临床近期、远期疗效高,复发率低,提高患者生活质量,值得推广应用。  相似文献   
84.
清代后中国文学的史学定位在现代文学内部划分为民国时期文学和共和国时期文学。与现代文学的意义概念不同的是,民国文学和共和国文学在中国现代文学的框架内都仅仅是一个时间概念。放弃文学史研究的整体主义努力,以多样主义或归纳主义的心态面对历史。中国现代文学的起点在1912年为各种争论的最大公约数,各种起点事件均看着是与起点联系的相关事件。先锋与常态的理论发现为一体两翼的成立找到理论依据。"民国机制"与"民国文学机制"的提出拓展了民国文学的研究思路,但本身却是可商之论。如果我们将民国文学机制改变为"民国文学环境"或者"民国文学生态",那么在民国时期不同时空中不同类型的文学自然会产生于不同的文学环境或生态。  相似文献   
85.
86.
This paper reviews recent policy initiatives in England to achieve the closer integration of health and social care. This has been a policy goal of successive UK governments for over 40 years but overall progress has been patchy and limited. The coalition government has a new national framework for integrated care and variety of new policy initiatives including the ‘pioneer’ programme, the introduction of a new pooled budget – the ‘Better Care Fund’ – and a new programme of personal commissioning. Further change is likely as the NHS begins to develop new models of care delivery. There are significant tensions between these very different policy levers and styles of implementation. It is too early to assess their combined impact. Expectations that integration will achieve substantial financial savings are not supported by evidence. Local effort alone will be insufficient to overcome the fundamental differences in entitlement, funding and delivery between the NHS and the social care system.With a national election set to take place in May 2015, all political parties are committed to the integration of health and social care but clear evidence about the best means to achieve it is likely to remain as elusive as ever.  相似文献   
87.

Objective

To compare the risk of falls and fall predictors in patients with Parkinson disease (PD), multiple sclerosis (MS), and stroke using the same study design.

Design

Multicenter prospective cohort study.

Setting

Institutions for physical therapy and rehabilitation.

Participants

Patients (N=299) with PD (n=94), MS (n=111), and stroke (n=94) seen for rehabilitation.

Interventions

Not applicable.

Main Outcome Measures

Functional scales were applied to investigate balance, disability, daily performance, self-confidence with balance, and social integration. Patients were followed for 6 months. Telephone interviews were organized at 2, 4, and 6 months to record falls and fall-related injuries. Incidence ratios, Kaplan-Meier survival curves, and Cox proportional hazards models were used.

Results

Of the 299 patients enrolled, 259 had complete follow-up. One hundred and twenty-two patients (47.1%) fell at least once; 82 (31.7%) were recurrent fallers and 44 (17.0%) suffered injuries; and 16%, 32%, and 40% fell at 2, 4, and 6 months. Risk of falls was associated with disease type (PD, MS, and stroke in decreasing order) and confidence with balance (Activities-specific Balance Confidence [ABC] scale). Recurrent fallers were 7%, 15%, and 24% at 2, 4, and 6 months. The risk of recurrent falls was associated with disease type, high educational level, and ABC score. Injured fallers were 3%, 8%, and 12% at 2, 4, and 6 months. The only predictor of falls with injuries was disease type (PD).

Conclusions

PD, MS, and stroke carry a high risk of falls. Other predictors include perceived balance confidence and high educational level.  相似文献   
88.
目的:通过对安徽省三县市卫生服务体系整合结构和有效性的研究,为促进卫生服务体系整合提供政策建议。方法:采用典型抽样,对安徽省马鞍山市、肥西县和肥东县卫生服务体系进行案例分析。数据主要来源于机构调查问卷、医生和患者调查问卷和机构关键知情人访谈。定量和定性数据分析相结合,采用社会网络分析方法分析体系整合结构和有效性。结果:马鞍山市卫生服务体系结构的整合度最高,其次是肥西县,肥东县最低。体系有效性与结构整合程度一致。三县市的卫生服务体系在整合方面均存在优势和不足。结论:卫生服务体系整合效果是各体系内外环境综合作用的产物。马鞍山市的市立医疗集团改革和肥西县的县乡医联体改革在整合卫生服务体系结构的同时对卫生服务体系的有效性产生了积极影响。  相似文献   
89.
This study investigated the in vivo formation of engineering cartilage within living or devitalized cartilage discs using reflectance mode confocal microscopy and conventional light microscopy. Pig articular chondrocytes were suspended in fibrin glue and placed between two cartilage discs. Four experimental groups were prepared: in groups 1 and 2, the cell-hydrogel composite was placed between two live or between two devitalized cartilage discs, respectively; in groups 3 and 4, acellular fibrin glue was placed between two live or between two devitalized cartilage discs, respectively. Samples were implanted in the back of nude mice and analyzed after 2, 5, and 8 weeks. Results showed that engineered cartilage seems to grow more homogenously when the cell-seeded gel was placed between devitalized cartilages than when it was placed between live cartilage matrices. Confocal microscopy provides valuable information on the integration of tissue-engineered cartilage with native tissue and could be useful for nondestructive imaging in vivo.  相似文献   
90.
The aim of this study was to develop nanofibrous silk substrates for limbal stem cell expansion that can serve as a potential alternative substrate to replace human amniotic membrane. The human limbal stem cell was used to evaluate the biocompatibility of substrates (random and oriented nanofibrous mats, and human amniotic membrane) based on their phenotypic profile, viability, proliferation, and attachment ability. Biocompatibility results indicated that all substrates were highly biocompatible, as limbal stem cells could favorably attach and proliferate on the nanofibrous surfaces. Microscopic figures showed that the human limbal stem cells were firmly anchored to the substrates and were able to retain a normal corneal stem cell phenotype. Microscopic analyses illustrated that cells infiltrated the nanofibers and successfully formed a three-dimensional corneal epithelium, which was viable for 15 days. Immunocytochemistry and real-time PCR results revealed no change in the expression profile of limbal stem cells grown on nanofibrous substrates when compared to those grown on human amniotic membrane. In addition, electrospun nanofibrous silk substrates especially oriented mat provides not only a milieu supporting limbal stem cells expansion, but also serve as a useful alternative carrier for ocular surface tissue engineering and could be used as an alternative substrate to amniotic membrane.  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