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   1272237篇
  免费   97067篇
  国内免费   1592篇
耳鼻咽喉   16414篇
儿科学   41225篇
妇产科学   35104篇
基础医学   190889篇
口腔科学   34970篇
临床医学   118643篇
内科学   249556篇
皮肤病学   27586篇
神经病学   102761篇
特种医学   47173篇
外国民族医学   268篇
外科学   179952篇
综合类   25808篇
现状与发展   3篇
一般理论   568篇
预防医学   106071篇
眼科学   28193篇
药学   93259篇
  6篇
中国医学   2031篇
肿瘤学   70416篇
  2018年   13660篇
  2017年   10515篇
  2016年   11494篇
  2015年   13295篇
  2014年   18232篇
  2013年   27802篇
  2012年   38074篇
  2011年   40499篇
  2010年   23358篇
  2009年   22588篇
  2008年   38236篇
  2007年   40889篇
  2006年   40420篇
  2005年   39522篇
  2004年   37949篇
  2003年   36376篇
  2002年   35224篇
  2001年   56251篇
  2000年   57313篇
  1999年   48309篇
  1998年   13506篇
  1997年   12323篇
  1996年   12773篇
  1995年   12157篇
  1994年   11342篇
  1993年   10612篇
  1992年   38464篇
  1991年   37912篇
  1990年   36634篇
  1989年   35380篇
  1988年   32797篇
  1987年   32130篇
  1986年   30630篇
  1985年   28892篇
  1984年   22029篇
  1983年   19268篇
  1982年   11407篇
  1981年   10375篇
  1979年   21019篇
  1978年   15451篇
  1977年   12833篇
  1976年   11886篇
  1975年   12865篇
  1974年   15653篇
  1973年   15428篇
  1972年   14572篇
  1971年   13616篇
  1970年   12821篇
  1969年   12116篇
  1968年   11267篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
The purpose of these experiments was to determine the effect of ethanol dose and time of administration on cerebral blood flow (CBF) and cerebral oxygen consumption (CMRO2). CBF and CMRO2 were measured in Sprague-Dawley rats 30 and 90 minutes after intraperitoneal injections of ethanol. Blood alcohol concentrations ranged from 1 to 3 mg/ml and were equivalent at both time periods. Ethanol produced small but significant increases in CBF and CMRO2 with blood alcohol concentrations. The above changes were not time dependent and were similar between 30 and 90 minute testing periods. The dose dependent effects of ethanol on cerebral metabolism are consistent with in vitro studies suggesting a dose related effect of ethanol on neuronal metabolism. The time of application appears to have little effect on the cerebral metabolic effects of alcohol.  相似文献   
992.
Atomic absorption spectrometry and x-ray fluorescence have been used to determine the lead content of metatarsal and tibia bone samples. For a range of bone lead levels from 6.5 to 83 micrograms g-1 of ashed bone there is no evidence of a systematic difference between the two techniques of more than 1 microgram g-1. There is, however, some evidence that random differences between the two in vitro analyses applied to the same bone sample are larger than can be accounted for by known measurement uncertainties. Variations in bone composition could account for these differences. Because the x-ray fluorescence technique is applied in an identical way to in vivo analysis, it is concluded that the uncertainties in in vivo measurements are small.  相似文献   
993.
994.
995.
In newly diagnosed adult patients with epilepsy followed prospectively on monotherapy, carbamazepine and phenytoin were associated with a fall in plasma uric acid, but sodium valproate and phenobarbitone were associated with a rise in plasma uric acid. The mechanisms and significance of these findings are discussed.  相似文献   
996.
Effect of respiratory training with a mouth-nose-mask in tetraplegics   总被引:1,自引:0,他引:1  
Ten tetraplegics, 8 males and 2 females, with a median age of 32 years participated in a scheduled 6 weeks training programme with a respiratory muscle training mouth-nose-mask (RMT-mask) with a fixed expiratory and an increasing inspiratory resistance set by the tetraplegic in accordance to his/her increasing ability during the training period. During the 6 weeks the tetraplegics required to use the RMT-mask for 15 minutes three times a day. Before and after each training session they measured peak flow (PEF). Lung volumes, ventilatory and diffusion capacity were measured before and after the 6 weeks training period. The training resulted only in a significant change in the PEF, which increased with 11% from 371 l/min before to 412 l/min in average after the 6 weeks of training (p less than 0.025). This statistically significant increase was confirmed by the measurements of PEF performed by the tetraplegics themselves during the training period. In addition there was an increase in PEF from before to immediately after each 15 minutes training session, this trend reached statistically significance (p less than 0.025) in the third '2 weeks period'. These results might indicate a possibility of improving the tetraplegics ability to cough by use of a simple RMT-mask, which in turn might prevent certain lung complications including pneumonia, and atelectasia.  相似文献   
997.
Mechanical properties of post and core systems   总被引:1,自引:0,他引:1  
  相似文献   
998.
999.
Of 299 patients who presented with superficial bladder cancer (Ta, T1), 60 were treated by intravesical chemotherapy (Epodyl, methotrexate or mitomycin C). The rate of tumour progression to muscle invasion or metastases was identical for each intravesical regime. There was no evidence that mitomycin C promoted tumour progression. Carcinoma in situ in non-tumour-bearing urothelium was the most significant predictive factor for progression to muscle invasion or metastases.  相似文献   
1000.
Five studies were conducted to examine the degree of variability to be expected during the use of the non-imaging nuclear probe (BIOS Inc.) under a variety of clinical conditions. Comparison of the ejection fraction (EF) readings between the nuclear probe and a gamma camera showed good agreement, with the nuclear probe tending to underestimate lower, and overestimate higher camera EF values [mean (S.D.) difference, 0.84% (6.06)]. A comparison of two nuclear probes showed a small mean (S.D.) difference of EF readings of 0.063% (2.26). EF readings obtained in normal subjects 6 weeks apart were reproducible and differed by a mean (S.D.) of 0.23% (4.42). The administration of placebo to 10 normal subjects followed by sequential measurements for 4 h produced EF changes large enough to mimic a clinical effect, the largest hourly change observed being 5.4%, indicating the need for strict placebo control in interventional experiments. Data on four patients with heart failure showed small non-significant EF changes in the 1 h after placebo administration but a wide intra-subject range of ejection time and time to peak filling measurements. This highlights the problem of accurate, reproducible cursor placement in such patients. The nuclear probe is a portable, low cost instrument which produces accurate EF measurements when compared with the gamma camera.  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