全文获取类型
收费全文 | 235607篇 |
免费 | 5570篇 |
国内免费 | 330篇 |
学科分类
医药卫生 | 241507篇 |
出版年
2023年 | 271篇 |
2021年 | 1138篇 |
2020年 | 730篇 |
2019年 | 1022篇 |
2018年 | 22974篇 |
2017年 | 18073篇 |
2016年 | 20306篇 |
2015年 | 2008篇 |
2014年 | 2511篇 |
2013年 | 3516篇 |
2012年 | 10583篇 |
2011年 | 24837篇 |
2010年 | 20944篇 |
2009年 | 13533篇 |
2008年 | 23236篇 |
2007年 | 25595篇 |
2006年 | 4478篇 |
2005年 | 6190篇 |
2004年 | 7115篇 |
2003年 | 7700篇 |
2002年 | 5820篇 |
2001年 | 991篇 |
2000年 | 1036篇 |
1999年 | 883篇 |
1998年 | 932篇 |
1997年 | 803篇 |
1996年 | 576篇 |
1995年 | 583篇 |
1994年 | 551篇 |
1993年 | 487篇 |
1992年 | 558篇 |
1991年 | 591篇 |
1990年 | 535篇 |
1989年 | 511篇 |
1988年 | 445篇 |
1987年 | 406篇 |
1986年 | 375篇 |
1985年 | 444篇 |
1984年 | 448篇 |
1983年 | 411篇 |
1982年 | 539篇 |
1981年 | 436篇 |
1980年 | 523篇 |
1979年 | 301篇 |
1978年 | 329篇 |
1977年 | 318篇 |
1976年 | 267篇 |
1975年 | 287篇 |
1974年 | 258篇 |
1973年 | 209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.
Rajendrababu Sharmila Puthuran George Varghese Alia Laxmi Ananya Uduman Mohammed Sithiq Wijesinghe Hiruni Kaushalya 《International ophthalmology》2022,42(8):2609-2618
International Ophthalmology - To investigate the efficacy and safety of non-valved Aurolab aqueous drainage implant (AADI) surgery combined with phacoemulsification in eyes with refractory glaucoma... 相似文献
3.
Seyed Mehdi BagheriMofidi Majid Pouladian Seyed Behnamedin Jameie Ali Abbaspour Tehrani-Fard 《Australasian physical & engineering sciences in medicine / supported by the Australasian College of Physical Scientists in Medicine and the Australasian Association of Physical Sciences in Medicine》2016,39(3):717-726
Magnetic field generated by neuronal activity could alter magnetic resonance imaging (MRI) signals but detection of such signal is under debate. Previous researches proposed that magnitude signal change is below current detectable level, but phase signal change (PSC) may be measurable with current MRI systems. Optimal imaging parameters like echo time, voxel size and external field direction, could increase the probability of detection of this small signal change. We simulate a voxel of cortical column to determine effect of such parameters on PSC signal. We extended a laminar network model for somatosensory cortex to find neuronal current in each segment of pyramidal neurons (PN). 60,000 PNs of simulated network were positioned randomly in a voxel. Biot–savart law applied to calculate neuronal magnetic field and additional phase. The procedure repeated for eleven neuronal arrangements in the voxel. PSC signal variation with the echo time and voxel size was assessed. The simulated results show that PSC signal increases with echo time, especially 100/80 ms after stimulus for gradient echo/spin echo sequence. It can be up to 0.1 mrad for echo time = 175 ms and voxel size = 1.48 × 1.48 × 2.18 mm3. With echo time less than 25 ms after stimulus, it was just acquired effects of physiological noise on PSC signal. The absolute value of the signal increased with decrease of voxel size, but its components had complex variation. External field orthogonal to local surface of cortex maximizes the signal. Expected PSC signal for tactile detection in the somatosensory cortex increase with echo time and have no oscillation. 相似文献
4.
5.
6.
La Rosa Mauricio Omere Chasey Redfern Tiffany Abdelwahab Mahmoud Spencer Nicholas Villarreal Josephine Olson Gayle Saade George R. Saad Antonio F. 《Archives of gynecology and obstetrics》2020,301(1):69-73
Archives of Gynecology and Obstetrics - The objective of this study was to determine if high-dose antibiotic prophylaxis with cefazolin decreases the risk of surgical site infection (SSI) after a... 相似文献
7.
8.
9.
10.
N. S. Hari Narayana Moorthy Sergio F. Sousa Maria J. Ramos Pedro A. Fernandes 《Medicinal chemistry research》2016,25(7):1340-1357
Farnesyltransferase (FTase) is one of the prenyltransferase family enzymes that catalyse the transfer of 15-membered isoprenoid (farnesyl) moiety to the cysteine of CAAX motif-containing proteins including Rho and Ras family of G proteins. Inhibitors of FTase act as drugs for cancer, malaria, progeria and other diseases. In the present investigation, we have developed two structure-based pharmacophore models from protein–ligand complex (3E33 and 3E37) obtained from the protein data bank. Molecular dynamics (MD) simulations were performed on the complexes, and different conformers of the same complex were generated. These conformers were undergone protein–ligand interaction fingerprint (PLIF) analysis, and the fingerprint bits have been used for structure-based pharmacophore model development. The PLIF results showed that Lys164, Tyr166, TrpB106 and TyrB361 are the major interacting residues in both the complexes. The RMSD and RMSF analyses on the MD-simulated systems showed that the absence of FPP in the complex 3E37 has significant effect in the conformational changes of the ligands. During this conformational change, some interactions between the protein and the ligands are lost, but regained after some simulations (after 2 ns). The structure-based pharmacophore models showed that the hydrophobic and acceptor contours are predominantly present in the models. The pharmacophore models were validated using reference compounds, which significantly identified as HITs with smaller RMSD values. The developed structure-based pharmacophore models are significant, and the methodology used in this study is novel from the existing methods (the original X-ray crystallographic coordination of the ligands is used for the model building). In our study, along with the original coordination of the ligand, different conformers of the same complex (protein–ligand) are used. It concluded that the developed methodology is significant for the virtual screening of novel molecules on different targets. 相似文献