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   2137035篇
  免费   150974篇
  国内免费   3954篇
耳鼻咽喉   31494篇
儿科学   67923篇
妇产科学   60487篇
基础医学   302147篇
口腔科学   62895篇
临床医学   186935篇
内科学   407280篇
皮肤病学   48722篇
神经病学   167803篇
特种医学   84272篇
外国民族医学   595篇
外科学   326638篇
综合类   48499篇
现状与发展   7篇
一般理论   677篇
预防医学   152432篇
眼科学   51196篇
药学   165516篇
  8篇
中国医学   5014篇
肿瘤学   121423篇
  2018年   20762篇
  2016年   18592篇
  2015年   20744篇
  2014年   28827篇
  2013年   43180篇
  2012年   57661篇
  2011年   61108篇
  2010年   36116篇
  2009年   34433篇
  2008年   57546篇
  2007年   62343篇
  2006年   63158篇
  2005年   60591篇
  2004年   58610篇
  2003年   56435篇
  2002年   55083篇
  2001年   104515篇
  2000年   107300篇
  1999年   90260篇
  1998年   24079篇
  1997年   21554篇
  1996年   19741篇
  1995年   19748篇
  1994年   18347篇
  1993年   17257篇
  1992年   69411篇
  1991年   67119篇
  1990年   65950篇
  1989年   64000篇
  1988年   58998篇
  1987年   57885篇
  1986年   55185篇
  1985年   52315篇
  1984年   38865篇
  1983年   32961篇
  1982年   19219篇
  1981年   17314篇
  1979年   36608篇
  1978年   25711篇
  1977年   22525篇
  1976年   20260篇
  1975年   23002篇
  1974年   27183篇
  1973年   26527篇
  1972年   25257篇
  1971年   23647篇
  1970年   22148篇
  1969年   21315篇
  1968年   19666篇
  1967年   17610篇
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
971.
The onset of diabetic nephropathy is characterized by subclinical elevation of urinary albumin excretion, so-called 'microalbuminuria' (M). Dietary assessments were carried out in 15 insulin-dependent diabetic patients with persistent M and an equal number with persistently normal albumin excretion. The groups were matched for sex, age, duration of diabetes, body mass index, insulin dose and glycosylated haemoglobin; there were no significant differences in systemic blood pressure, glomerular filtration rate, blood glucose and serum albumin concentrations between the groups; retinopathy was significantly more frequent in patients with M. Diabetics with persistent M were found to consume a significantly larger amount of fat (expressed as grams and percentage of total energy) and a significantly smaller percentage of total energy as carbohydrate than patients with normal albumin excretion; total dietary energy was larger in those with persistent M, but the difference was not significant. No significant differences were found in protein and fibre intakes between the groups. Our findings suggest that an excess in the dietary consumption of fat relative to carbohydrate might play an important role in the pathogenesis of early nephropathy in insulin-dependent diabetes mellitus. We emphasize the importance of careful attention to nutrient intake in the prevention and treatment of diabetic complications.  相似文献   
972.
Normal stereoscopic vision is necessary for many occupations. Therefore, stereoacuity must be measured accurately. Borderline values are not yet available for existing stereo-tests or, as for haploscopic tests, their degree of difficulty is too low. In order to provide an accurate, natural measuring method for both scientific and practical applications, an existing three-rod tester was modified to convert it into a distant-vision stereo-tester, and a new near-vision stereo-tester was designed. A standardized test method was developed and borderline values were established for both units.  相似文献   
973.
Post-traumatic retinal detachment occurs frequently as a late consequence of progressive vitreous changes, especially following penetrating injuries. Occasionally, it develops soon after the trauma, without preceding proliferative vitreoretinopathy, is based on posterior vitreous detachment and morphologically resembles an idiopathic retinal detachment. It is possible that the posterior vitreous detachment in these cases is encouraged by the presence of intravitreal hemorrhage.  相似文献   
974.
The YAG (yttrium aluminum garnet) laser has been recommended for anterior capsulotomies. One major complication is elevated intraocular pressure. We report a study of the biochemical content of the aqueous humor after a YAG laser anterior capsulotomy. We analyzed 6-keto-prostaglandin F1 alpha, thromboxane B2 and protein concentrations in the aqueous humor of human eyes. The average values of protein, 6-keto-prostaglandin F1 alpha, and thromboxane B2 in the control eyes were 81.3 +/- 14.0 mg/dL, 17 +/- 30 pg/mL, and 10 +/- 10 pg/mL, respectively. These values were elevated to 182.4 +/- 81.3 mg/dL, 401 +/- 55 pg/mL, and 576 +/- 148 pg/mL, respectively, after YAG laser anterior capsulotomy. The samples with a moderate level of 6-keto-prostaglandin F1 alpha (less than 300 pg/mL) had negligible changes of thromboxane. The elevation of thromboxane was obvious only when prostaglandin levels rose above 300 pg/mL.  相似文献   
975.
976.
Elimination of antibiotic-resistant plasmids by quinolone antibiotics   总被引:2,自引:0,他引:2  
Of 7 plasmids we tested, the plasmid pORF2 was eliminated in vitro with the most efficiency by treatment with subinhibitory concentrations of novobiocin, coumermycin and 10 quinolones. It showed a cure rate of 43% by enoxacin; 12% by novobiocin, pefloxacin, ciprofloxacin and CI-934; 7% by coumermycin and ofloxacin; 9% by amifloxacin; and 4% by AM-833. On the other hand, pSC194, pBR322 and pMH612 were poorly cured in vitro by quinolones, except pSC194 which was cured 33% by enoxacin. R1, pP1603, and pUB110 were unaffected by the treatment. Mice were challenged intraperitoneally with a 2XLD50 of Escherichia coli carrying the ORF2 plasmid and were treated per os with 1 X or 1/2 X ED50 of either enoxacin or CI-934. The frequency of loss of ampicillin resistance determined 3 h after treatment shows curing effects of 92% for CI-934, 89% for enoxacin and 20% for untreated control.  相似文献   
977.
An exaggerated fall in blood pressure has been reported with the combination of an alpha 1-blocker and a calcium antagonist. This study investigated, in a placebo-controlled, randomized crossover trial, the clinical usefulness of the combination of prazosin (2 mg b.i.d.) and verapamil (160 mg b.i.d.). Therapeutic efficacy was monitored at regular outpatient visits: average supine and erect blood pressures were, respectively, 175/99 and 176/103 mm Hg with placebo, 160/91 and 164/96 mm Hg with single drug treatment, and 152/84 and 152/89 mm Hg with combination therapy. This significant and clinically useful reduction in blood pressure had an overall magnitude of approximately 28/18 mm Hg (supine) and 29/19 mm Hg (erect). Further measurements were made during a series of intensive study days, and the most important additional finding was a pharmacokinetic interaction that resulted in increased peak concentrations and bioavailability of prazosin. In conclusion, the combination of prazosin and verapamil proved effective in the treatment of 12 patients with essential hypertension who had been poorly responsive to conventional treatment with a beta-blocker and thiazide diuretic.  相似文献   
978.
979.
In this graphite-furnace atomic-absorption spectrometric method for measuring manganese in whole blood, we use a pyrolytic platform to minimize interference by sample matrix. For optimal sample ashing we denature the sample within the furnace with nitric acid and use oxygen as the purge gas at low temperatures. The mean manganese concentration found in blood from 15 unexposed city dwellers was 215 (2 SD 135) nmol/L. By comparison, the range of manganese concentrations in blood sampled from a group of Australian aborigines living near a surface manganese ore deposit on Groote Eylandt, Northern Territory, was much higher (median 405 nmol/L, range 175 to 990 nmol/L).  相似文献   
980.
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