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   11207篇
  免费   625篇
  国内免费   159篇
耳鼻咽喉   184篇
儿科学   146篇
妇产科学   240篇
基础医学   1736篇
口腔科学   242篇
临床医学   903篇
内科学   1977篇
皮肤病学   564篇
神经病学   668篇
特种医学   719篇
外科学   1810篇
综合类   79篇
一般理论   1篇
预防医学   607篇
眼科学   185篇
药学   988篇
中国医学   156篇
肿瘤学   786篇
  2023年   58篇
  2022年   231篇
  2021年   351篇
  2020年   176篇
  2019年   275篇
  2018年   296篇
  2017年   215篇
  2016年   350篇
  2015年   493篇
  2014年   593篇
  2013年   681篇
  2012年   980篇
  2011年   953篇
  2010年   597篇
  2009年   464篇
  2008年   659篇
  2007年   633篇
  2006年   564篇
  2005年   567篇
  2004年   426篇
  2003年   371篇
  2002年   333篇
  2001年   220篇
  2000年   227篇
  1999年   180篇
  1998年   81篇
  1997年   66篇
  1996年   52篇
  1995年   42篇
  1994年   40篇
  1993年   36篇
  1992年   62篇
  1991年   61篇
  1990年   53篇
  1989年   42篇
  1988年   50篇
  1987年   38篇
  1986年   45篇
  1985年   46篇
  1984年   38篇
  1983年   49篇
  1981年   16篇
  1980年   15篇
  1979年   29篇
  1978年   27篇
  1977年   21篇
  1976年   23篇
  1975年   16篇
  1974年   17篇
  1973年   24篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
101.
102.
This empirical study identifies the negative aspects of private health insurance (PHI) by analyzing the association between subjective health conditions, 2 weeks of outpatient care, chronic diseases, and hospitalizations for 1 year. We used frequency analysis, χ2 testing, an analysis of variance, and logistic and multiple logistic regression models to analyze the association between PHI and subjective health conditions, outpatient care, chronic disease status, and hospitalization. The PHI group had good subjective health but had more outpatient care for 2 weeks. There were few chronic diseases in the private insurance group, and there was no significant difference in hospitalizations for 1 year. Hospitalization may occur when essential medical care is required, regardless of health insurance type. This study confirmed that as the PHI lowers the burden of personal medical expenses, the PHI can lead to an increase in the medical resource expenditures on the outpatient medical service and higher public health costs. The government should work to redefine the role of private and national health insurance. Also, the effectiveness of PHI should be reevaluated so that it does not lead to indiscriminate use of medical services by minimizing the burden of private insurance.  相似文献   
103.
104.
The present study was designed to investigate whether the aqueous extract of rhubarb (AR) could prevent the development of atherosclerosis through regulating vascular inflammatory processes in rats fed with an atherogenic diet. AR significantly reduced plasma low-density lipoprotein-cholesterol, and increased plasma high-density lipoprotein-cholesterol in rats fed with an atherogenic diet. AR inhibited vascular expressions of endothelin-1 (ET-1) and endothelin-converting enzyme (ECE) induced in rats with an atherogenic diet. On the other hand, AR augmented the vascular expression of endothelial nitric oxide synthase (ecNOS) and restored vascular nitric oxide (NO) production. Furthermore, AR suppressed the elevated expression of vascular nuclear factor-kappaB (NF-kappaB) p65 as well as adhesion molecules, including intracellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1), and E-selectin in rats fed with an atherogenic diet. Also, AR decreased endothelial expression of ICAM-1 and ET-1 in aorta. These results suggest that AR suppresses the development of atherosclerosis in the atherogenic-diet rat model through inhibiting vascular expressions of proinflammatory and adhesion molecules via the regulation of nitric oxide and endothelin system.  相似文献   
105.
Anti-bone resorption properties of the Korean herbal formulation, Gami-Honghwain (HJ), which comprises Carthamus tinctorius L. seed and hominis placenta, were investigated. We demonstrate that the production of PGE2 is inhibited by 20-100 microg/ml HJ in nontransformed osteoblastic cells (MC3T3-E1 cells), indicating that HJ inhibits PGE2 production. The effect of HJ on the proliferation and osteoblastic differentiation in MC3T3-E1 was also studied. HJ dose-dependently increased DNA synthesis (significant at 20-100 microg/ml), and increased alkaline phosphatase (ALP) and prolyl hydroxylase activities of MC3T3-E1 cells (20-100 microg/ml), while anti-estrogen tamoxifen eliminated the stimulation of proliferation and ALP activity of MC3T3-E1 which was induced by HJ. These results indicate that HJ directly stimulates cell proliferation and differentiation of osteoblasts. Also, when we assessed the effects of HJ on osteoblastic differentiation in MC3T3-E1, HJ enhanced ALP activity and mineralization in a dose- and time-dependent fashion. This stimulatory effect of the HJ was observed at relatively low doses (significant at 20-100 microg/ml and maximal at 100 microg/ml). Northern blot analysis showed that the HJ (60 microg/ml) increased in bone morphogenetic protein-2 as well as ALP mRNA concentrations in MC3T3-E1 cells. HJ (100 microg/ml) slightly increased in type I collagen mRNA abundance throughout the culture period, whereas it markedly inhibited the gene expression of collagenase-1 between days 15 and 20 of culture. These results indicate that HJ has anabolic effect on bone through the promotion of osteoblastic differentiation, suggesting that it could be used for the treatment of common metabolic bone diseases.  相似文献   
106.
AIM OF THE STUDY: To elucidate the pharmacological activities of deer antler acupuncture and TGF61538;1 on the acute and chronic phases of rheumatoid arthritis diseases. MATERIALS AND METHODS: Polyarthritis rats were administered with TGF61538;1 and water extract of deer antler acupunture (DAA), prepared from the pilose antler of Cervus korean TEMMINCK var. mantchuricus Swinhoe. TGF61538; (0.1 to 2 61549;g/animal) and DAA (5-100 61549;g/kg animal) were initiated 1 day before an arthritogenic dose of streptococcal cell wall fragments to see the effects on the joint swelling and distortion during the acute phase and the chronic phase of the disease. Arthritic index suppression of rat arthritis model was examined by TGF61538; and DAA administrations. RESULTS: TGF61538;1 and DAA diminished the polyarthritis development in rats. TGF61538; and DAA eliminated the joint swelling and distortion observed during the acute phase and the chronic phase of the disease. The TGF61538; and DAA suppressed the arthritis progress when administration was begun after acute phase of arthritis. DISCUSSION: Consistent with the inhibition of inflammatory cell recruitment into the synovium, TGF61538;1 and DAA reversed the leukocytosis associated with the chronic phase of the arthritis, respectively.  相似文献   
107.
OBJECTIVES: The purpose of our study is to provide reference values for the great vessels obtained from images of the three-vessel view of the fetal heart, with an emphasis on the size discrepancy of the great vessels. METHODS: From February 2003 to May 2003, the main pulmonary artery (MPA), ascending aorta (AA), and SVC were measured in well-dated, nonanomalous fetuses scanned at 14-38 weeks of gestation. RESULTS: The size of each great vessel had a significant positive relationship with advance in gestation (P < 0.001); MPA (mm) = -2.76 + 0.34 x GA, ascending aorta (AA) (mm) = -1.73 + 0.26 x GA - 1.18E - 05 x GA(3), and SVC (mm) = 0.33 + 0.01 x GA(2) - 4.12E - 05 x GA(3). The AA/MPA ratio was significantly decreased with advance in gestation, while the SVC/AA ratio was significantly increased; AA/MPA ratio = -1.24 - 0.03 x GA + 3.88E - 04 x GA(2); P < 0.001, SVC/AA ratio = 0.63 - 5.43E - 03 x GA + 1.96E - 04 x GA(2); P < 0.001. CONCLUSION: On the three-vessel view of the fetal heart, the interpretation of the size discrepancy of the great vessels needs to be adjusted according to fetal growth.  相似文献   
108.
Silicon-based anodes can increase the energy density of Li-ion batteries (LIBs) owing to their large weights and volumetric capacities. However, repeated charging and discharging can rapidly deteriorate the electrochemical properties because of a large volume change in the electrode. In this study, a commercial Fe-Si powder was coated with Al2O3 layers of different thicknesses via atomic layer deposition (ALD) to prevent the volume expansion of Si and suppress the formation of crack-induced solid electrolyte interfaces. The Al2O3 content was controlled by adjusting the trimethyl aluminum exposure time, and higher Al2O3 contents significantly improved the electrochemical properties. In 300 cycles, the capacity retention rate of a pouch full-cell containing the fabricated anodes increased from 69.8% to 72.3% and 79.1% depending on the Al2O3 content. The powder characterization and coin and pouch cell cycle evaluation results confirmed the formation of an Al2O3 layer on the powder surface. Furthermore, the expansion rate observed during the charging/discharging of the pouch cell indicated that the deposited layer suppressed the powder expansion and improved the cell stability. Thus, the performance of an LIB containing Si-alloy anodes can be improved by coating an ALD-synthesized protective Al2O3 layer.  相似文献   
109.
110.
Although melanogenesis is a defense mechanism against ultraviolet (UV)-induced skin damage, abnormally excessive melanin production causes pigmentation disorders. Tyrosinase, as a key factor for melanin synthesis, plays an important role in inducing skin pigmentation. Therefore, the inhibition of tyrosinase is crucial in preventing skin pigmentation in the cosmetics and medicine fields. However, the majority of well-known tyrosinase inhibitors have been discontinued due to toxic effects on the skin or lack of selectivity and/or stability. In this study, we evaluated possible anti-melanogenic effects of catechin-7-O-α-L-rhamnopyranoside (C7R) isolated from the stem bark of Ulmus parvifolia, to discover a new tyrosinase inhibitor that has both safety and stability. When C7R was pretreated in B16F10 melanoma cells stimulated by α-melanocyte-stimulating hormone, this compound reduced melanin accumulation and murine tyrosinase activity. In line with these results, C7R inhibits tyrosinase purified from a mushroom in vitro like kojic acid and arbutin. Furthermore, C7R exhibited a competitive inhibition on a Lineweaver-Burk plot. Next, the underlying mechanisms of the C7R-mediated tyrosinase inhibitory effect were sought through docking simulation and pharmacophore analysis between tyrosinase residues and C7R. The results of these analyses showed that C7R had binding energy of -14.5kcal/mol, and indicated that C7R interacts with tyrosinase through an aromatic ring and various hydrophobic and hydrogen bonds. Together, our results suggest that C7R can be applied as a novel natural anti-melanogenic agent that inhibits tyrosinase.  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