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   5819篇
  免费   252篇
  国内免费   15篇
耳鼻咽喉   87篇
儿科学   94篇
妇产科学   24篇
基础医学   715篇
口腔科学   73篇
临床医学   352篇
内科学   1360篇
皮肤病学   128篇
神经病学   396篇
特种医学   122篇
外科学   1194篇
综合类   19篇
预防医学   179篇
眼科学   195篇
药学   443篇
中国医学   1篇
肿瘤学   704篇
  2022年   53篇
  2021年   58篇
  2020年   44篇
  2019年   59篇
  2018年   84篇
  2017年   82篇
  2016年   93篇
  2015年   107篇
  2014年   144篇
  2013年   157篇
  2012年   222篇
  2011年   273篇
  2010年   176篇
  2009年   134篇
  2008年   235篇
  2007年   259篇
  2006年   271篇
  2005年   307篇
  2004年   277篇
  2003年   288篇
  2002年   291篇
  2001年   200篇
  2000年   223篇
  1999年   206篇
  1998年   64篇
  1997年   63篇
  1996年   48篇
  1995年   52篇
  1994年   56篇
  1993年   45篇
  1992年   143篇
  1991年   130篇
  1990年   116篇
  1989年   104篇
  1988年   115篇
  1987年   89篇
  1986年   102篇
  1985年   109篇
  1984年   56篇
  1983年   50篇
  1982年   35篇
  1979年   39篇
  1977年   35篇
  1974年   29篇
  1973年   27篇
  1972年   29篇
  1971年   27篇
  1969年   27篇
  1967年   33篇
  1966年   27篇
排序方式: 共有6086条查询结果,搜索用时 15 毫秒
141.
We successfully treated a case of mitral regurgitation due to chest trauma in Barlow's disease. A 71‐year‐old man was admitted with severe mitral regurgitation after blunt compression of the chest by a heavy object 5 months earlier. Preoperative examination revealed wide chordae tendineae rupture and myxomatous changes to the bileaflets. Neo‐chordae reconstruction of the anterior mitral leaflet using loop technique, triangular resection of the posterior mitral leaflet, and ring annuloplasty was performed via surgical robot. Robotic mitral valve plasty for severe mitral regurgitation due to chest trauma in Barlow's disease was achieved safely with good clinical and excellent cosmetic results.  相似文献   
142.
We compared vasti muscle electromyograms for two knee joint angles during fatiguing tetanic contractions. Tetanic contraction of the knee extensors was evoked for 70 s by electrical stimulation of the femoral nerve at knee joint angles of 60° (extended, with 0° indicating full extension) and 110° (flexed) in eight healthy men. Surface electromyography was recorded from the vastus intermedius (VI), vastus lateralis (VL) and vastus medialis (VM) muscles. Knee extension force and M‐wave amplitudes and durations were calculated every 7 s, which were normalized by the initial value. Normalized knee extension force was decreased at the flexed knee joint angle compared with that of the extended knee joint angle (P<0·05). Decreased normalized M‐wave amplitude and increased normalized M‐wave duration of the VI were greater at the flexed knee joint angle than the extended knee joint angle (P<0·05), whereas those for the VL and VM were similar (P>0·05). These results suggest that peripheral fatigue profiles of the VI might be greater at the flexed than the extended knee joint angles, but that of VL and VM might be similar in the tested range of knee joint angles (i.e. 60°–110°) during continuous tetanic contraction induced by electrical stimulation. Therefore, greater reduction of knee extension force at the flexed knee joint angle than the extended knee joint angle may reflect fatigue development of the VI more than other quadriceps femoris components.  相似文献   
143.
144.
Aims: The aim of the study was to determine whether increased physical activities (PA) affect frailty for old women, 75 years and older (OO), compared to 60–74 years old (YO). Methods: This cross-sectional study measured 19 frailty indicators (muscle strength and endurance, balance, gait characteristics, and function), using 46 community-dwelling women. PA were divided into three levels by caloric expenditure per week (<2,000 kcal/week, 2,000–3,999 kcal/week, >4,000 kcal/week). Results: As PA level increased, a gap (=difference) between OO and YO narrowed for step length and function, but for quadriceps strength and endurance, a gap widened. Conclusions: Frailty progresses with aging but older women who engage in a high level of physical activity (>4,000 kcal/week) can increase mobility and functional capacity, but not for muscle strength and endurance. Starting regular resistance training activities early in the aging process is critical to improve or maintain muscle quality to offset age-related frailty.  相似文献   
145.
146.
The unevenness of pulmonary nanoparticle (NP) distribution, which hinders the establishment of an absolute dose–response relationship, has been described as one of the limitations of intratracheal administration techniques for toxicological assessment of inhaled NPs. Quantification of the NP microdistribution would facilitate the establishment of a concentration–response relationship in localized regions of the lung; however, such quantitative methods have not been reported. Here, we established a quantitative method for evaluating pulmonary TiO2 NP microdistribution in rats using X‐ray fluorescence microscopy. Ti intensity in lung sections from rats intratracheally administered 10 mg kg–1 TiO2 NPs with a microsprayer was measured using X‐ray fluorescence with a 100 µm beam size. Ti reference samples were prepared by dropping different concentrations of Ti solutions on glass slide or lung sections of untreated rat. Ti intensity increased linearly with Ti content in the reference samples on both substrates. The detection limit of TiO2 was estimated to be 6.3 ng mm–2. The reproducibility was confirmed for measurements done in the short‐ (2 weeks) and long‐term (6 months). The quantitative results of TiO2 NP microdistribution suggested that more TiO2 NPs were distributed in the right caudal and accessory lobes, which are located downstream of the administration direction of the NP suspension, and the lower portion of each lobe. The detection rates of TiO2 NPs were 16.6–25.0%, 5.19–15.6%, 28.6–39.2%, 21.4–38.7% and 10.6–23.2% for lung sections from the right cranial, middle, caudal, accessory and left lobes, respectively. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   
147.
We studied isotype-specific rheumatoid factors (RFs) to clarify their significance in rheumatoid arthritis (RA) and to verify the difference in RF isotypes between RA and chronic liver diseases (CLD). Isotype-specific RFs in RA and in CLD were measured by enzyme-linked immunosorbent assay (ELISA). Most sera (n = 51, 94.1%) from RA patients contained some kind of RF isotypes (92.1% for IgM RF, 76.4% for IgG RF, and 43.1% for IgA RF), and seronegative RA by ELISA was seen in only 11.8% (n = 6). The most characteristic combination of RF isotypes in active RA was IgG, IgA, and IgM. This combination of RF isotypes changed to IgG plus IgM, according to the diminution of RA activity; then, we found only IgM RF in inactive RA. The titers of each RF isotype also decreased in parallel with the activity of RA. IgA RF seemed to be the most sensitive factor for evaluating the activity of RA. In CLD, almost the same high frequency (n = 49, 89.8% for IgM RF, 59.2% for IgG RF), with the same titer levels seen in RA, was observed. On the other hand, IgA RF was significantly lower in frequency (n = 9, 18.4%) and in titer, compared with the finding in RA. Surprisingly, even in CLD, true seronegativity by ELISA was also found in very few patients (n = 4, 8.1%). In CLD, positive RFs detected by agglutination assay were seen more often in chronic hepatitis than in liver cirrhosis. In RA patients, significant associations of IgA RF and the serum concentration of IgA, and IgG RF and the serum concentration of IgG, were observed. On the other hand, in CLD patients, significant associations of IgG RF and the serum IgG concentration, and of IgM RF and the serum IgM concentration, were observed. These results indicated that IgA RF in active RA is the most characteristic RF isotype distinguishing it from other nonrheumatic diseases, as well as from inactive RA. RF isotypes reflected the background polyclonal B-cell activation in different manners in both diseases. In CLD, RF isotypes seemed to be disease-related immunological disorders reflecting disease progression. Received: February 17, 2000 / Accepted: July 5, 2001  相似文献   
148.
A Japanese Family with Two Sisters Apparently Homozygous for Mk   总被引:1,自引:0,他引:1  
Two Japanese sisters with consanguineous parents have M-N- En(a-) Wr(a-b-) S-s-U- red cells and are therefore apparently homozygous for Mk; the third reported family with members of this genotype. The serum of the proposita (ORCMK) contained anti-EnaTS, anti-EnaFR and possibly anti-Wrb, whereas the serum of her MkMk sister contained no atypical antibodies. Total absence of sialoglycoproteins alpha and delta from red cell membranes of an Mk homozygote was demonstrated by lactoperoxidase-catalysed radioiodination of accessible tyrosine residues with subsequent SDS polyacrylamide gel electrophoresis and autoradiography, and by use of a monoclonal antibody directed at the cytoplasmic portion of alpha-sialoglycoprotein.  相似文献   
149.
In recent years, the number of Japanese traveling to foreign countries is increasing. Most of them travel to Asian regions where many infectious diseases that are rare or don't occur in Japan still remain endemic or epidemic. Of these infectious diseases typhoid fever and meningococcal infection are now preventable because safe and effective vaccines have been developed and now marketed. However, these vaccines are hardly available in Japan because the Japanese Government has not admitted them. To investigate the demand for the two vaccines, the author personally imported inactivated polysaccharide typhoid vaccine and groups A, C,Y and W135 combined polysaccharide meningococcal vaccine, both manufactured by Aventis-Pasteur. After obtaining approval of the ethical committee of our hospital, vaccination was started. From May 6, 2003 to September 30, 2004, 124 applicants received typhoid vaccine and 35 were injected with meningococcal vaccine. Of 124 vaccinees of typhoid vaccine, 46 went to Afghanistan, 15 to India, 8 to Thailand. Of 35 vaccinees of meningococcal vaccine 6 went to the USA, 5 to Guinea and 3 to England. In addition a total of 12 physicians and nurses having no international scheduled trip were also immunized with meningococcal vaccine. None of these vaccines are widely known in Japan now. Based on our results, however, the expansion of recognition and demand for these two vaccines is expected.  相似文献   
150.
AIMS: We recently demonstrated that aldosterone induces a non-genomic vasoconstrictor effect on rat coronary arterioles and that this effect was blocked by angiotensin II type 1 receptor (AT1) blockers. Intracellular transglutaminase enhances AT1 signalling by cross-linking AT1 homodimers. The purpose of this study was to confirm the AT1-dependency of the vasoconstrictor effect of aldosterone using AT1a knockout (AT1aKO) mice and to investigate the role of intracellular transglutaminase and AT1 dimerization in this effect. METHODS AND RESULTS: The mesenteric arterioles (60-160 microm) were isolated from C57BL/6J (wild-type, WT) and AT1aKO mice, and the internal diameter was measured by video microscopy. Aldosterone (10(-13) to 10(-6) M), but not hydrocortisone, produced a dose-dependent vasoconstriction in WT mice; the maximal diameter change was -8.6 +/- 0.3% from the baseline (P < 0.001). This vasoconstrictor effect was unaffected by the mineralocorticoid receptor antagonist spironolactone or eplerenone, the AT2 antagonist PD123319, the glucocorticoid receptor antagonist RU486, or endothelium denudation. Aldosterone's vasoconstrictor effect was negligible in AT1aKO mice. The AT1 blockers valsartan or candesartan suppressed aldosterone-induced vasoconstriction in WT mice. The transglutaminase inhibitors cystamine and monodansyl cadaverine also suppressed the vasoconstrictor effect of aldosterone, without affecting the vasoconstrictor effect of angiotensin II in WT mice. AT1 dimer protein levels were increased in WT mesenteric arterioles treated with 10(-7) M aldosterone, and the transglutaminase inhibitor and AT1 blocker blocked this aldosterone-induced formation of AT1 dimer. Treatment with 10(-7) M aldosterone for 10 min increased the transglutaminase activity by 2.5 +/- 0.2-fold in cultured vascular smooth muscle cells and by 1.2 +/- 0.1-fold in the mesenteric arterioles. These increases were abolished by transglutaminase inhibitors. CONCLUSION: Aldosterone produces a non-genomic, endothelium-independent vasoconstrictor effect by enhancing intracellular transglutaminase activity and presumably inducing AT1 dimer formation in mesenteric arterioles.  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