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   1733039篇
  免费   114990篇
  国内免费   3755篇
耳鼻咽喉   22115篇
儿科学   56528篇
妇产科学   46721篇
基础医学   244702篇
口腔科学   49413篇
临床医学   153908篇
内科学   338599篇
皮肤病学   39292篇
神经病学   134305篇
特种医学   64670篇
外国民族医学   249篇
外科学   260608篇
综合类   39351篇
现状与发展   4篇
一般理论   569篇
预防医学   126675篇
眼科学   40826篇
药学   125390篇
  47篇
中国医学   4496篇
肿瘤学   103316篇
  2021年   13343篇
  2019年   14283篇
  2018年   20361篇
  2017年   15612篇
  2016年   17032篇
  2015年   19364篇
  2014年   26747篇
  2013年   38957篇
  2012年   53918篇
  2011年   56734篇
  2010年   33546篇
  2009年   31400篇
  2008年   52822篇
  2007年   56137篇
  2006年   56592篇
  2005年   53831篇
  2004年   51988篇
  2003年   49324篇
  2002年   47537篇
  2001年   92189篇
  2000年   93977篇
  1999年   77351篇
  1998年   20023篇
  1997年   17533篇
  1996年   17609篇
  1995年   16974篇
  1994年   15519篇
  1993年   14307篇
  1992年   57723篇
  1991年   55604篇
  1990年   53288篇
  1989年   51054篇
  1988年   46394篇
  1987年   45178篇
  1986年   42512篇
  1985年   40235篇
  1984年   29620篇
  1983年   25167篇
  1982年   14169篇
  1981年   12656篇
  1979年   25768篇
  1978年   17742篇
  1977年   15066篇
  1976年   14036篇
  1975年   14730篇
  1974年   17807篇
  1973年   17132篇
  1972年   15857篇
  1971年   14601篇
  1970年   13573篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
131.
132.
133.
The biodistribution of two recently developed tumour markers, trimethylated (CP(Me)3) and trimethoxylated (CP(OMe)3) carotenoporphyrin, was investigated by means of laser-induced fluorescence (LIF) after i.v. injection into 38 tumour-bearing (MS-2 fibrosarcoma) female Balb/c mice. At 3, 24, 48 or 96 h after administration, the carotenoporphyrin fluorescence was measured in tumoral and peritumoral tissue, as well as in the abdominal, thoracic and cranial cavities. The fluorescence was induced by a nitrogen laser-pumped dye laser, emitting light at 425 nm, and analysed by a polychromator equipped with an image-intensified CCD camera. The fluorescence was evaluated at 490, 655 and 720 nm: the second and third wavelengths represent the carotenoporphyrin (CP)-related peaks, whereas the first one is close to the peak of the tissue autofluorescence. The tumour and the liver were the two tissue types showing the strongest carotenoporphyrin-related fluorescence, whereas the cerebral cortex and muscle consistently exhibited weak substance-related fluorescence. In most tissue types, the fluorescence intensities decreased over time. A few exceptions were observed, notably the liver, in which the intensity remained remarkably constant over the time period investigated.  相似文献   
134.
Abstract Perioscan requires a plaque sample to detect the presence of enzymes capable of degrading N-benzoyl-DL-arginine-2-naphthylamide (BANA) from relatively few anaerobic periodontal pathogens. Periocheck assays the presence of neutral proteases in crevicular fluid. The aim of this study was to compare these test kits with traditional clinical methods of detecting periodontal disease and to monitor the ability of the kits to reflect the response to initial therapy. 19 patients with moderately severe chronic periodontitis were seen before and after a course of oral hygiene and root instrumentation consisting of 4 appointments. Clinical measurements and test assays were collected at 5 diseased sites and 2 healthy sites in each subject. Complete data from 125 sites were available for statistical analysis. At baseline Periocheck had a sensitivity of 88% and a specificity of 61% whereas Perioscan had a sensitivity of 99% and a specificity of 55%, when related to the clinical diagnosis. A composite clinical assessment, based on improvement or deterioration of one whole unit change of the subjective clinical indices and 2mm changes or greater in probing depth or probing attachment level, revealed 75 sites which improved following treatment, whereas 45 sites did not change and 5 sites deteriorated. The probability that the tests agreed with the clinical outcome after treatment, was calculated as 50.4% for Periocheck and 52% for Perioscan. The diagnostic kits did not reliably reflect the clinical assessment of periodontal disease in the cross sectional study, or the outcome following treatment.  相似文献   
135.
136.
This study aimed at identifying the signal(s) that elicit myositis-induced neuroplastic changes in background activity and responsiveness of spinal neurones. It is based on previous data suggesting that in dorsal horn neurones, responsiveness to peripheral input on one hand and background activity on the other are probably controlled by different mechanisms. In anaesthetized rats, myositis was induced in the gastrocnemius-soleus muscle and the activity of single dorsal horn neurones was recorded in segment L3. Impulse traffic and axoplasmatic transport in dorsal roots L4 and L5 were selectively blocked by lignocaine or vinblastine for various time periods relative to the induction of the myositis. The results show that the main triggering signal for the myositis-induced changes in both responsiveness and background activity is the altered impulse activity in primary afferent fibres. In contrast, 'no axonally transported chemical signal controlling the discharge behaviour of dorsal horn neurones was found. However, the time course of the electrical signals that cause the myositis-induced changes in background activity and responsiveness is different. For changes in responsiveness, a rather narrow time window of 2 h directly after induction of the myositis existed, during which the impulses from the inflamed muscle must reach the spinal cord. Accordingly, to prevent the increase in responsiveness, the electrical input had to be blocked during the first 2 h; a block of the same duration at another time had no effect. The change in background activity seems to be due to a continuous input from the inflamed muscle which adds up over the hours. Therefore, with regard to background activity, blocking the electrical signals is effective at any time, but only a block of long duration has a significant effect.  相似文献   
137.
The results of the in vitro fertilisation programme at Tygerberg Hospital for the period April 1983 to January 1988 are presented. Of the 1117 laparoscopies performed, 825 patients reached the transfer stage. A live-birth rate of 9.3% was achieved. The pregnancy rate after transfer of 4 embryos was 25.9% compared with 15.4% after 2 embryos and 10.8% after 3 embryos (P = less than 0.0001). The multiple pregnancy rate was 2.8% in the group receiving 2 embryos and 11.7% and 10.4% in those receiving 3 and 4 embryos, respectively. Of the 77 successful pregnancies (90 babies), 1 baby died at 34 weeks' gestation as the result of abruptio placentae due to preeclampsia and 1 cot death occurred. The only congenital abnormality encountered was a cleft palate.  相似文献   
138.
Eleven patients with lunatomalacia were treated by excision of the lunate and instillation of liquid silicone. The silicone vulcanised and formed an in-situ molded prosthesis. The patients were reexamined after a mean of 7.1 years. Four patients were pain-free and two had pain only at work; three had not been improved by the operation and two had undergone arthrodesis. The patients with good results all belonged to group IV pre-operatively. Surprisingly, no patient showed any sign of silicone synovitis, although all the prostheses except one had either fractured or deformed. The reasons for this are discussed and the indications for the operation established.  相似文献   
139.
1. Effects of a novel imidazoindole derivative on cholinergic function were studied in isolated tissue preparations. 2. The compound demonstrated a dose-dependent (10(-11)-10(-9) potentiation (20-60%) of acetylcholine induced tension in guinea pig ileal tissue. 3. Increases in the size of end-plate potentials and nerve evoked muscle twitches were observed in frog nerve-skeletal muscle preparations. 4. Cholinesterase activity was not inhibited. 5. The results suggest that the compound has actions at the post-synaptic muscarinic receptor complex in smooth muscle and causes pre-synaptic increases in ACh release at the neuromuscular junction.  相似文献   
140.
We report a case of recurrent calculi in a Kock pouch continent urinary diversion. An open operation was avoided by successfully excising the Marlex mesh and removing it with the associated calculi in an endoscopic fashion.  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