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   115018篇
  免费   31408篇
  国内免费   1111篇
耳鼻咽喉   2642篇
儿科学   2915篇
妇产科学   2795篇
基础医学   4944篇
口腔科学   5345篇
临床医学   28074篇
内科学   27987篇
皮肤病学   3528篇
神经病学   13685篇
特种医学   4334篇
外科学   21320篇
综合类   282篇
现状与发展   40篇
一般理论   50篇
预防医学   14570篇
眼科学   2633篇
药学   2366篇
中国医学   27篇
肿瘤学   10000篇
  2024年   553篇
  2023年   5160篇
  2022年   1399篇
  2021年   3582篇
  2020年   5689篇
  2019年   2733篇
  2018年   7628篇
  2017年   7847篇
  2016年   8448篇
  2015年   8631篇
  2014年   11363篇
  2013年   13155篇
  2012年   5570篇
  2011年   5338篇
  2010年   7697篇
  2009年   9913篇
  2008年   4770篇
  2007年   3666篇
  2006年   4690篇
  2005年   3152篇
  2004年   2367篇
  2003年   1944篇
  2002年   1694篇
  2001年   1891篇
  2000年   1187篇
  1999年   1716篇
  1998年   2137篇
  1997年   1942篇
  1996年   1969篇
  1995年   1692篇
  1994年   1095篇
  1993年   922篇
  1992年   751篇
  1991年   648篇
  1990年   510篇
  1989年   536篇
  1988年   511篇
  1987年   383篇
  1986年   360篇
  1985年   309篇
  1984年   260篇
  1983年   308篇
  1982年   229篇
  1981年   199篇
  1980年   126篇
  1979年   77篇
  1978年   127篇
  1977年   117篇
  1976年   89篇
  1972年   75篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.

Objective

The aim of the study was to estimate the effect of the state-based reinsurance programs through the section 1332 State Innovation Waivers on health insurance marketplace premiums and insurer participation.

Data Source

2015 to 2022 Robert Wood Johnson Foundation Health Insurance Exchange Compare Datasets.

Study Design

An event study difference-in-differences (DD) model separately for each year of implementation and a synthetic control method (SCM) are used to estimate year-by-year effects following program implementation.

Data Collection/Extraction Methods

Not applicable.

Principal Findings

Reinsurance programs were associated with a decline in premiums in the first year of implementation by 10%–13%, 5%–19%, and 11%–17% for bronze, silver, and gold plans (p < 0.05). There is a trend of sustained declines especially for states that implemented their programs in 2019 and 2020. The SCM analyses suggest some effect heterogeneity across states but also premium declines across most states. There is no evidence that reinsurance programs affected insurer participation.

Conclusion

State-based reinsurance programs have the potential to improve the affordability of health insurance coverage. However, reinsurance programs do not appear to have had an effect on insurer participation, highlighting the need for policy makers to consider complementary strategies to encourage insurer participation.  相似文献   
2.
3.
4.
5.
6.
7.
8.
9.
Amacrine cells of the retina are conspicuously variable in their morphologies, their population demographics, and their ensuing functions. Vesicular glutamate transporter 3 (VGluT3) amacrine cells are a recently characterized type of amacrine cell exhibiting local dendritic autonomy. The present analysis has examined three features of this VGluT3 population, including their density, local distribution, and dendritic spread, to discern the extent to which these are interrelated, using male and female mice. We first demonstrate that Bax-mediated cell death transforms the mosaic of VGluT3 cells from a random distribution into a regular mosaic. We subsequently examine the relationship between cell density and mosaic regularity across recombinant inbred strains of mice, finding that, although both traits vary across the strains, they exhibit minimal covariation. Other genetic determinants must therefore contribute independently to final cell number and to mosaic order. Using a conditional KO approach, we further demonstrate that Bax acts via the bipolar cell population, rather than cell-intrinsically, to control VGluT3 cell number. Finally, we consider the relationship between the dendritic arbors of single VGluT3 cells and the distribution of their homotypic neighbors. Dendritic field area was found to be independent of Voronoi domain area, while dendritic coverage of single cells was not conserved, simply increasing with the size of the dendritic field. Bax-KO retinas exhibited a threefold increase in dendritic coverage. Each cell, however, contributed less dendrites at each depth within the plexus, intermingling their processes with those of neighboring cells to approximate a constant volumetric density, yielding a uniformity in process coverage across the population.SIGNIFICANCE STATEMENT Different types of retinal neuron spread their processes across the surface of the retina to achieve a degree of dendritic coverage that is characteristic of each type. Many of these types achieve a constant coverage by varying their dendritic field area inversely with the local density of like-type neighbors. Here we report a population of retinal amacrine cells that do not develop dendritic arbors in relation to the spatial positioning of such homotypic neighbors; rather, this cell type modulates the extent of its dendritic branching when faced with a variable number of overlapping dendritic fields to approximate a uniformity in dendritic density across the retina.  相似文献   
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