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   2734281篇
  免费   204526篇
  国内免费   6045篇
耳鼻咽喉   36179篇
儿科学   90508篇
妇产科学   75600篇
基础医学   387465篇
口腔科学   77694篇
临床医学   247714篇
内科学   536184篇
皮肤病学   62789篇
神经病学   217691篇
特种医学   103083篇
外国民族医学   696篇
外科学   411593篇
综合类   63969篇
现状与发展   7篇
一般理论   948篇
预防医学   209450篇
眼科学   64126篇
药学   197111篇
  7篇
中国医学   6593篇
肿瘤学   155445篇
  2019年   21933篇
  2018年   31481篇
  2017年   23851篇
  2016年   26538篇
  2015年   29922篇
  2014年   41981篇
  2013年   62276篇
  2012年   85369篇
  2011年   90490篇
  2010年   53355篇
  2009年   50289篇
  2008年   83699篇
  2007年   88870篇
  2006年   89715篇
  2005年   86349篇
  2004年   83079篇
  2003年   79191篇
  2002年   76338篇
  2001年   138660篇
  2000年   142164篇
  1999年   117703篇
  1998年   32330篇
  1997年   28517篇
  1996年   28598篇
  1995年   27365篇
  1994年   24974篇
  1993年   23250篇
  1992年   89729篇
  1991年   86113篇
  1990年   82865篇
  1989年   79545篇
  1988年   72811篇
  1987年   71153篇
  1986年   66656篇
  1985年   63472篇
  1984年   47400篇
  1983年   40098篇
  1982年   23379篇
  1981年   20803篇
  1979年   41808篇
  1978年   29105篇
  1977年   24481篇
  1976年   23040篇
  1975年   23961篇
  1974年   29006篇
  1973年   27980篇
  1972年   26059篇
  1971年   23908篇
  1970年   22536篇
  1969年   21014篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Piroximone (MDL 19,205), a new imidazolone derivative, was given intravenously to 14 patients with congestive heart failure (NYHA class II-III), while under constant daily doses of digitalis and diuretics. In the first 3 patients, we determined the dose safely eliciting a favorable hemodynamic response. The subsequent 11 patients received 1 mg/kg of piroximone intravenously, and the hemodynamic effects were compared with those of sodium nitroprusside (SN) at a dose-lowering mean blood pressure by 10-20 mm Hg. Piroximone increased heart rate (13.2 +/- 2.0 beats/min, mean +/- SEM) and lowered mean arterial pressure (9 +/- 2.3 mm Hg). Both agents reduced similarly wedge pressure (6.5 +/- 2.9 and 9 +/- 2.9 mm Hg, respectively, for SN and piroximone) and total peripheral resistance. Cardiac index was increased less by SN (15%) than piroximone (48%) (p less than 0.001), and stroke work index significantly enhanced only by piroximone (p less than 0.001). The changes in loading conditions induced by the two agents being similar, it is likely that piroximone not only acts by peripheral vasodilation, but also possesses positive inotropic properties. Myocardial oxygen demand, assessed indirectly by tension-time index, was not affected by piroximone. Thus, piroximone appears to combine well-balanced vasodilator and inotropic properties which make this new agent potentially very useful for the management of congestive heart failure.  相似文献   
992.
Collagen, fibronectin and laminin are important components of the extracellular matrix of the human cornea. We used the immunofluorescence technique with polyclonal antibodies directed against these proteins and to bullous pemphigoid antigen (BPA), in order to study their distribution in human corneas from 8 weeks of gestation to term and in adult corneas. Immunoreactivity was observed with antibodies to type I collagen in the limbus and the corneal stroma at 8 weeks of gestation. At 11 weeks of gestation it was found in epithelial basement membrane (EBM) and Descemet's membrane (DM) and continued thus throughout fetal and adult life. Type II collagen was not detected in fetal or adult cornea. Type III collagen was detected during 8-20th weeks of gestation in the EBM, DM and stroma. After 27th weeks of gestation, type III collagen could no longer be detected in the central cornea. Type IV collagen was detected in the EBM as early as 8 weeks of gestation and remained positive throughout fetal and adult life. Descemet's membrane was negative for type IV collagen at 8 weeks of gestation and became positive thereafter. Immunostaining for fibronectin in DM was negative at 8 weeks of gestation, followed by patchy staining of corneal stroma and EBM up to the age of 37 weeks of gestation. Staining in the EBM was negative or variable up to 70 years of age, and then became positive again in a 77 year old individual. Staining for LN was positive in the EBM after 8 weeks of gestation. Staining was negative in DM at that age, but became positive after 9 weeks of gestation. Staining for BPA was negative at 8-9 weeks of gestation, then gradually became positive.  相似文献   
993.
A new rapid procedure for desiccating frozen resin-cracked retinal tissue for scanning electron microscopy (SEM) which permits air-drying was found to compare favorably with tissues prepared by critical-point drying: Retinal tissue was fixed in 4% phosphate-buffered neutral formaldehyde, dehydrated by means of graded ethanol, embedded in Epon, cracked and washed in propylene oxide. For desiccation, the specimens were immersed in hexamethyldisilazane (HMDS), air-dried and finally sputter-coated. The method is time-saving, gives extended information in SEM, and the number of good specimens is increased.  相似文献   
994.
Perbendazole was given orally and subcutaneously to mice infected with Angiostrongylus cantonensis at different stages of infection. The subcutaneous route of administration was more effective than the oral one. On the 5th day after infection, the perbendazole had a higher efficacy than on the 10th day postinfection. This finding shows that perbendazole had complete larvicidal effect at early stages of infection.  相似文献   
995.
Case-adjusted prospective reimbursement systems, such as resource utilization groups (RUGs), may promote nursing home cost containment, but they may do no better than existing systems at encouraging homes to admit the more dependent and thus costlier Medicaid patients, if the homes' reluctance to admit these patients is due to a shortage of nursing home beds. Using 1983 data on Wisconsin nursing homes, this paper presents evidence that suggests that the presence of excess demand, rather than low reimbursement rates, causes nursing homes to exclude the more costly Medicaid patients. Consequently, to benefit fully from RUGs, it is necessary either to eliminate excess demand (by increasing supply or decreasing demand) or to decide which patients have priority for admission and assign reimbursement payments to these patients that significantly favor these patients. Otherwise, access to nursing home care under RUGs is left to chance.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
996.
997.
Fifty-five patients with vascular insufficiency resulting in above-knee (AK) and through-knee (TK) amputations were studied to determine factors related to prosthetic candidacy and functional outcome. Chart review showed that the only difference between patients who were fitted with prostheses and those who were not fitted with prostheses was their respective number of medical complications. Twenty-three of 31 patients with prostheses were evaluated 7 to 35 months after receiving the prostheses. Ten (44%) of these patients wore their prostheses all day every day and used wheelchairs minimally or not at all. Over half of the patients evaluated used their wheelchairs most of the time. Two (9%) of the 23 patients had stopped wearing their prostheses. Patients who demonstrated increased walking distances and velocities at follow-up used their prostheses more and their wheelchairs less than did the other patients. Neither gait factors nor hip range of motion at discharge was predictive of continued prosthetic use. Functional outcome and prosthetic use were limited in this group of elderly patients with dysvascular AK and TK amputations. The results of this study may serve as a basis for clinical determination of prosthetic candidacy and functional goals.  相似文献   
998.
A goal for the obstetrician and neonatologist is to screen for risk factors associated with intraventricular hemorrhage (IVH) in the low-birthweight infant. Perinatal events that lead to neonatal metabolic and cardiovascular derangements seem to provoke IVH, and conflicting reports have implicated labor as being contributory. A fetal heart rate (FHR) abnormality during premature labor may be a predictor of subsequent neonatal IVH. For this reason, 5 years of FHR tracings at two university medical centers were reviewed for inborn infants who were delivered after premature labor and weighed less than or equal to 2000 gm. Sixty-four infants developed IVH, but pre-existing labor with a discernible FHR pattern was recorded in only 38 (59%) cases. Interpretations were reassuring in 17 (45%) cases, suspicious in 7 (18%) cases, and ominous in 14 (37%) cases. This proportion of FHR patterns was not significantly different from a matched group of premature infants without IVH during the same period. Interpretations of intrapartum FHR patterns of low-birthweight infants are limited, especially before 30 weeks gestation, and not useful in predicting neonatal IVH.  相似文献   
999.
1000.
Granuloma annulare possibly triggered by antitetanus vaccination   总被引:4,自引:0,他引:4  
We report the case of a 6-year-old girl with granuloma annulare (GA) possibly related to antitetanus vaccinations. The first episode occurred 2 months after the girl had been vaccinated but the lesions were not located at the vaccination site. After 1 year of being free of lesions, she had a second episode unrelated to vaccination. After another 6-month lesion-free period, the girl was administered another antitetanus vaccination and a solitary lesion developed at the vaccination site within 3 days. A few lesions developed on her legs in the 2 months following the appearance of the initial plaque. The literature includes two reports of cases with papular lesions limited to the hepatitis B vaccination site, both histopathologically consistent with necrobiotic granuloma, but clinically not suggestive of GA. To the best of our knowledge, GA following antitetanus vaccination and occurring at the vaccination site has not been reported before. Either the trauma alone from the injection or a vaccine-induced immunological reaction might have triggered the necrobiosis of collagen through some unexplained mechanisms.  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