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   30166篇
  免费   2987篇
  国内免费   2266篇
耳鼻咽喉   330篇
儿科学   356篇
妇产科学   355篇
基础医学   3627篇
口腔科学   550篇
临床医学   4023篇
内科学   4453篇
皮肤病学   370篇
神经病学   1572篇
特种医学   1118篇
外国民族医学   16篇
外科学   2756篇
综合类   5107篇
现状与发展   8篇
一般理论   6篇
预防医学   2258篇
眼科学   876篇
药学   3297篇
  19篇
中国医学   1795篇
肿瘤学   2527篇
  2024年   94篇
  2023年   477篇
  2022年   1224篇
  2021年   1564篇
  2020年   1220篇
  2019年   1066篇
  2018年   1104篇
  2017年   1108篇
  2016年   1006篇
  2015年   1383篇
  2014年   1804篇
  2013年   1658篇
  2012年   2385篇
  2011年   2522篇
  2010年   1560篇
  2009年   1255篇
  2008年   1650篇
  2007年   1603篇
  2006年   1486篇
  2005年   1477篇
  2004年   1030篇
  2003年   988篇
  2002年   840篇
  2001年   671篇
  2000年   604篇
  1999年   610篇
  1998年   411篇
  1997年   370篇
  1996年   281篇
  1995年   290篇
  1994年   249篇
  1993年   182篇
  1992年   212篇
  1991年   190篇
  1990年   137篇
  1989年   140篇
  1988年   132篇
  1987年   104篇
  1986年   81篇
  1985年   61篇
  1984年   29篇
  1983年   42篇
  1981年   17篇
  1980年   13篇
  1979年   15篇
  1978年   7篇
  1977年   8篇
  1976年   7篇
  1974年   7篇
  1973年   9篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
993.
Here we report the supercapacitive properties of a novel MoO3−x/TiO2 nanotube composite prepared by a facile galvanostatic deposition technique and subsequently thermal treatment in an argon atmosphere between 350 °C and 550 °C. X-ray diffraction and X-ray photoelectron spectroscopy confirm the existence of MoO3−x. The MoO3−x/TiO2 electrode prepared at 550 °C exhibits a high specific capacitance of 23.69 mF cm−2 at a scan rate of 10 mV s−1 and good cycling stability with capacitance retention of 86.6% after 1000 cycles in 1 M Na2SO4 aqueous solution. Our study reveals a feasible method for the fabrication of TiO2 nanotubes modified with electroactive MoO3−x as high-performance electrode materials for supercapacitors.

Here we report the supercapacitive properties of a novel MoO3−x/TiO2 nanotube composite prepared by a facile galvanostatic deposition technique and subsequently thermal treatment in an argon atmosphere between 350 °C and 550 °C.  相似文献   
994.

Background

Opioid-induced constipation (OIC) can be a debilitating side effect of opioid therapy and may result in increased medical costs. The published data on the economic burden of OIC among long-term opioid users are limited.

Objective

To assess the economic burden of OIC in patients with noncancer pain in a managed care population in the United States.

Methods

This retrospective study used 2007–2011 data from the Truven Health MarketScan Commercial and Medicare databases. The study included adults with ≥12 months of insurance enrollment before and after starting long-term (≥90 days) use of opioids. Patients were excluded if they had cancer or a diagnosis of drug abuse or drug dependence during the study period, or if they had constipation or bowel obstruction within 90 days before starting opioid therapy during the study period. OIC was identified by International Classification of Diseases, Ninth Edition codes for constipation (564.0) or bowel obstruction (560.x) within 12 months of the initiation of an opioid. Patients with OIC were identified in the nonelderly, elderly (age ≥65 years), and long-term care populations. Differences in costs and healthcare resource utilization were calculated using propensity scoring.

Results

A total of 13,808 nonelderly (age, 48.6 ± 10.4 years; female, 50%) and 2958 elderly patients (age, 78.7 ± 8.1 years; female, 70%) met the study inclusion criteria. Of 401 nonelderly and 194 elderly patients with OIC, 85 patients initiated opioid therapy in a long-term care facility (age, 80.7 ± 11.6 years; female, 77%). After matching by key covariates, patients with OIC had significantly more hospital admissions than patients without OIC (nonelderly, 33% vs 22%, respectively; P <.001; elderly, 51% vs 31%, respectively; P <.001) and longer inpatient stays (nonelderly, 3.0 ± 8.4 days vs 1.0 ± 3.0 days, respectively; P <.001; elderly, 5.2 ± 12.2 days vs 2.1 ± 4.0 days, respectively; P <.001). The group with OIC had significantly higher total healthcare costs than the group without OIC in all 3 study cohorts (nonelderly, $23,631 ± $67,209 vs $12,652 ± $19,717, respectively; elderly, $16,923 ± $38,191 vs $11,117 ± $19,525, respectively; long-term care, $16,000 ± $22,897 vs $14,437 ± $25,690, respectively; all P <.05).

Conclusion

To the best of our knowledge, this is the first study to analyze the economic impact of long-term use of opioids among patients with OIC, using real-world data. The findings underscore the significant economic burden associated with long-term opioid use for noncancer pain in a managed care population. Effective therapies for OIC may reduce the associated economic burden and improve quality of life for long-term opioid users.  相似文献   
995.
AIM: To describe and compare the differences in electroretinographic responses between two different age groups of adult Dark Agouti (DA) rats and to better understand the effect of age on retinal histology and function.METHODS: The electroretinographic responses of two different age groups of adult DA rats were compared. Animals were divided into younger adult DA rats 10-12wk (n=8) and older adult DA rats 17-19wk (n=8). Full field electroretinography (ERG) was recorded simultaneously from both eyes after dark adaption and light adaption and parameters including the positive scotopic threshold response (pSTR), negative scotopic threshold response (nSTR), scotopic a-wave, b-wave, photopic a-wave, b-wave and photopic negative response (PhNR) were compared between groups.RESULTS: The older adult rats displayed lower stimulation thresholds of the STRs (pSTR and nSTR) and higher amplitudes of pSTR, scotopic a-wave and b-wave, photopic b-wave and PhNR amplitudes, with shorter implicit times. Photopic a-wave amplitudes were however higher in the younger adult rats.CONCLUSION:In summary, for the rod system, photoreceptor, bipolar cell and RGC activity was enhanced in the older adult rats. For the cone system, RGC and bipolar cell activity was enhanced, while photoreceptor activity was depressed in the older adult rats. Such age-related selective modification of retinal cell function needs to be considered when conducting ophthalmic research in adult rats.  相似文献   
996.
AIM: To investigate the effect of DSX, an active component extracted from Erigeron breviscapus, on the voltage-gated outward K+ channel currents in rat retinal ganglion cells (RGCs) by using electrophysiological method, and to explore the possible mechanisms of DSX on optic nerve protection. METHODS: Outward K+ currents were recorded by using whole-cell patch-clamp techniques on acutely isolated rat RGCs. Outward K+ currents were induced by a series of depolarizing voltage pulses from a holding potential of -70 mV to +20 mV in an increment of 10 mV. RESULTS: Extracellular application of DSX voltage-dependently suppressed both the steady-state and peak current amplitudes of outward K+ currents in rat RGCs. Furthermore, DSX reversibly and dose-dependently inhibited the amplitudes of outward K+ currents of the cells. At +20 mV membrane potential DSX at the concentrations of 0.02 g/L and 0.05 g/L showed no significant effects on the currents. In contrast, DSX at higher concentrations (0.1 g/L, 0.2 g/L and 0.5 g/L) significantly suppressed the current amplitudes. CONCLUSION: These results suggest that DSX reversibly and dose-dependently suppress outward K+ channel currents in rat RGCs, which may be one of the possible mechanisms underlying Erigeron breviscapus prevents vision loss and RGC damage caused by glaucoma.  相似文献   
997.
998.
999.
1000.
Malaria importation and local vector susceptibility to imported Plasmodium vivax infection are a continuing risk along the China–Myanmar border. Malaria transmission has been prevented in 3 border villages in Tengchong County, Yunnan Province, China, by use of active fever surveillance, integrated vector control measures, and intensified surveillance and response.  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