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   1492篇
  免费   144篇
  国内免费   230篇
耳鼻咽喉   13篇
儿科学   18篇
妇产科学   20篇
基础医学   246篇
口腔科学   9篇
临床医学   87篇
内科学   313篇
皮肤病学   11篇
神经病学   152篇
特种医学   29篇
外国民族医学   1篇
外科学   189篇
综合类   287篇
一般理论   2篇
预防医学   74篇
眼科学   102篇
药学   148篇
中国医学   65篇
肿瘤学   100篇
  2024年   1篇
  2023年   26篇
  2022年   29篇
  2021年   50篇
  2020年   23篇
  2019年   18篇
  2018年   12篇
  2017年   17篇
  2016年   13篇
  2015年   48篇
  2014年   79篇
  2013年   71篇
  2012年   167篇
  2011年   173篇
  2010年   48篇
  2009年   37篇
  2008年   191篇
  2007年   145篇
  2006年   154篇
  2005年   119篇
  2004年   80篇
  2003年   86篇
  2002年   71篇
  2001年   61篇
  2000年   65篇
  1999年   32篇
  1998年   11篇
  1997年   14篇
  1996年   5篇
  1995年   5篇
  1993年   2篇
  1992年   1篇
  1991年   3篇
  1989年   3篇
  1987年   1篇
  1986年   1篇
  1985年   2篇
  1982年   1篇
  1980年   1篇
排序方式: 共有1866条查询结果,搜索用时 15 毫秒
1.
<正>Since the first case of acquired immune deficiency syndrome (AIDS) was detected in the United States in 1981,this disease has spread to every corner of the world.Despite the annual incidence of AIDS showing a slight decline since1997,it remains a major cause of infectious disease-related death worldwide.Unlike global epidemiological trends,the number of notified AIDS cases has increased in recent years in China[1].  相似文献   
2.
A rapid and high selective ultra?performance liquid chromatography (UPLC) with tandem mass spectrometry method for simultaneous determination of six compounds including albiflorin, paeoniflorin, picroside I, picroside II, saikosaponin A, and saikosaponin D in rat plasma was developed and validated using butyl p-hydroxybenzoate as an internal standard. One-step direct protein precipitation with acetonitrile was used to extract the compounds from the rat plasma samples. Chromatographic separation was achieved using an ACQUITY UPLC BEH C18 column (100 mm × 2.1 mm, 1.7 µm) at a flow rate of 0.4 mL/min, using gradient mode containing 0.1% formic acid in water and acetonitrile were used as the Mobile phase A and B. Electrospray ionization in negative ion mode and multiple reaction monitoring were used to identify and quantify active components. Calibration curves showed good linearity (R2 > 0.9908) over a wide concentration range for all compounds. The intra- and interday precision (relative standard deviation) ranged 2.4%–7.0% and 2.6%–8.0%, respectively. The accuracy (relative error) was from ?13.0% to 13.2% at all quality control levels. The recovery ranged from 81.1% to 92.5%. The validated method was successfully applied to pharmacokinetic study in rats after oral administration of Qing Gan?Shu Yu?Fang. The results show that one can draw a conclusion that these six active ingredients can be quickly absorbed and play a pharmacodynamic role rapidly in vivo.  相似文献   
3.
4.
Objective Evidence is lacking regarding the combined effects of smoking and obesity on mortality from coronary heart disease in male veterans.This study aimed to explore the combined effect of smoking and obesity on coronary heart disease mortality in male veterans in China.Methods A cohort of 1,268 male veterans from 22 veteran centers in Xi’an(Shaanxi Province,China)were followed up once every 2 years from February 1,1987 to October 30,2016.The endpoint was death from any cause.The hazard ratio(HR)of each risk factor and the 95%confidence interval(CI)were calculated using a multivariate Cox proportional hazard model.Results The total follow-up was 24394.21 person-years;each subject was followed up for a mean duration of 19.24 years.By the end of the study,of the 1,268 veterans,889 had died,363 were alive,and 16 were lost to follow-up.Cox regression analysis results revealed that current smoking(HR:1.552,95%CI:1.074–2.243),obesity(HR:1.625,95%CI:1.024–2.581),and the combined effect of the two factors(HR:2.828,95%CI:1.520–5.262)were associated with coronary heart disease mortality.Conclusion Our results suggest that obese veterans who smoke might be an important target population for coronary heart disease mortality control.  相似文献   
5.
Objective The relationship between outdoor temperature and blood pressure(BP) has been inconclusive. We analyzed data from a prospective cohort study in northwestern China to investigate the effect of outdoor temperature on BP and effect modification by season.Methods A total of 32,710 individuals who participated in both the baseline survey and the first follow-up in 2011–2015 were included in the study. A linear mixed-effect model and generalized additive mixed model(GAMM) were applied to estimate the association between outdoor temperature and BP after adjusting for confounding variables.Results The mean differences in systolic blood pressure(SBP) and diastolic blood pressure(DBP)between summer and winter were 3.5 mm Hg and 2.75 mm Hg, respectively. After adjusting for individual characteristics, meteorological factors and air pollutants, a significant increase in SBP and DBP was observed for lag 06 day and lag 04 day, a 0.28 mm Hg(95% CI: 0.27–0.30) per 1 °C decrease in average temperature for SBP and a 0.16 mm Hg(95% CI: 0.15–0.17) per 1 °C decrease in average temperature for DBP, respectively. The effects of the average temperature on both SBP and DBP were stronger in summer than in other seasons. The effects of the average temperature on BP were also greater if individuals were older, male, overweight or obese, a smoker or drinker, or had cardiovascular diseases(CVDs), hypertension, and diabetes.Conclusions This study demonstrated a significant negative association between outdoor temperature and BP in a high-altitude environment of northwest China. Moreover, BP showed a significant seasonal variation. The association between BP and temperature differed by season and individuals' demographic characteristics(age, gender, BMI), unhealthy behaviors(smoking and alcohol consumption), and chronic disease status(CVDs, hypertension, and diabetes).  相似文献   
6.
Inefficient diabetic ulcer healing and scar formation remain a challenge worldwide,owing to a series of disordered and dynamic biological events that occur during the process of healing.A functional wound dressing that is capable of promoting ordered diabetic wound recovery is eagerly anticipated.In this study,we designed a silicone elastomer with embedded 20(S)-protopanaxadiol-loaded nanostructured lipid carriers(PPD-NS)to achieve ordered recovery in scarless diabetic ulcer healing.The nanostructured lipid carriers were prepared through an emulsion evaporation-solidification method and then incorporated into a network of silicone elastomer to form a unique nanostructured lipid carrier-enriched gel formulation.Interestingly,the PPD-NS showed excellent in vitro anti-inflammatory and proangiogenic activity.Moreover,in diabetic mice with full-thickness skin excision wound,treatment with PPD-NS significantly promoted in vivo scarless wound healing through suppressing inflammatory infiltration in the inflammatory phase,promoting angiogenesis during the proliferation phase,and regulating collagen deposition in the remodeling phase.Hence,this study demonstrates that the developed PPD-NS could facilitate ordered diabetic wound recovery via multifunctional improvement during different wound-healing phases.This novel approach could be promising for scarless diabetic wound healing.  相似文献   
7.
8.
AIM: To describe and compare pathologic findings in eyes enucleated after superselective ophthalmic arterial chemotherapy (SOAC) or SOAC with intravenous chemotherapy (IVC) for retinoblastoma. METHODS: Medical records between January 1st, 2014 and June 31st, 2017 were retrospectively analyzed, and pathologic findings were recorded. This study included 36 eyes from 22 (61.1%) male and 14 (38.9%) female patients. Nineteen of 36 (52.8%) eyes received SOAC (mean=3, range=1-7) as primary treatment, and 17 of 36 (47.2%) eyes received SOAC (mean=3.7, range=1-10) after IVC (mean=6.1, range=2-11). Tumor extension including choroidal invasion (n=9, 25%), optic nerve invasion (n=5, 13.9%) and anterior segment invasion (n=5, 13.9%) were recorded. RESULTS: Histopathologic evidence of ischemic damage in the retina and choroid was found in 28 (77.8%) eyes. Thrombosed blood vessels were identified in 9 (25%) eyes, including orbital artery in the retrobulbar orbit (n=1), intrascleral vessels (n=4), and chorioretinal vessels (n=6). Fibrotic changes were found in extraocular muscles (n=5, 13.9%) and optic nerve (n=5, 13.9%). Varying degrees of scleral degeneration were found in all eyes. In statistical analysis, there was no significant difference in clinical and pathologic changes between SOAC group and SOAC with IVC group except for optic nerve invasion (P=0.047). CONCLUSION: SOAC for retinoblastoma can result in ocular toxicity, and SOAC with IVC did not increase the toxicity but reduced the incidence of optic nerve invasion.  相似文献   
9.
Lycium barbarum(LB)is a traditional Chinese medicine that has been demonstrated to exhibit a wide variety of biological functions,such as antioxidation,neuroprotection,and immune modulation.One of the main mechanisms of Alzheimer’s disease is that microglia activated by amyloid beta(Aβ)transform from the resting state to an M1 state and release pro-inflammatory cytokines to the surrounding environment.In the present study,immortalized microglial cells were pretreated with L.barbarum extract for 1 hour and then treated with oligomeric Aβfor 23 hours.The results showed that LB extract significantly increased the survival of oligomeric Aβ-induced microglial cells,downregulated the expression of M1 pro-inflammatory markers(inducible nitric oxide synthase,tumor necrosis factorα,interleukin-6,and interleukin-1β),and upregulated the expression of M2 anti-inflammatory markers(arginase-1,chitinase-like protein 3,and interleukin-4).LB extract also inhibited the oligomeric Aβ-induced secretion of tumor necrosis factorα,interleukin-6,and interleukin-1βin microglial cells.The results of in vitro cytological experiments suggest that,in microglial cells,LB extract can inhibit oligomeric Aβ-induced M1 polarization and concomitant inflammatory reactions,and promote M2 polarization.  相似文献   
10.
Objective: To observe the effects of electroacupuncture (EA) of different intensities on lactate dehydrogernase (LDH), succinate dehydrogenase (SDH) and ATPase in brain tissue of rats with cerebral ischemia-reperfusion injury (CI/R). Methods: Forty male SD rats were uniformly randomized into sham operation group (group A), CI/R group (group B), CI/R+5 mA EA (group C), CI/R+3 mA EA (group D) and CI/R+1 mA EA (group E) groups with eight rats in each group. Transient general brain ischemia was induced by four-vessel occlusion and reperfusion. The rats in group C, group D and group E were punctured and stimulated at Baihui (GV20), Mingmen (GV4) and Zusanli (ST36) with the same intermittent and rarefaction-dense wave (30 to 50 Hz) and different electric current intensities: 5 mA , 3 mA and 1 mA for 20 min after CI/R. Then the activities of Na+-K+-ATPase, SDH and LDH in mitochondria of brain tissue were measured by spectrophotometry. The ischemic cerebral cortex tissue was taken for observing the ultrastructure changes of impaired nerve cells. Results: Compared with group A, the activities of LDH, SDH and Na+-K+-ATPase were lowerer in the group B (P<0.05 or P<0.01). However, the activities of LDH, SDH and Na+-K+-ATPase were higher in the group D than those in the group B (P<0.05 or P<0.01). In group A, the anatomical structure of the cerebral cortex cells was basically normal; in group B, the neuronal cellular structures were severely damaged, the neuronal mitochondria got swelling, the mitochondrial cristae were broken, the medullated nerve fibers were not integrated. In group C, group D and group E, the ultrastructure of impaired neuron were improved. Group D was the best among three groups above. Conclusion: EA of 3 mA intensity could strengthen aerobic metabolism by elevating the activities of SDH and LDH, meanwhile maintaining the ionic equilibrium in the exterior and interior brain cell and relieving the cellular edema by reinforcing the activities of Na+-K+-ATPase.  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