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   185817篇
  免费   11091篇
  国内免费   1726篇
耳鼻咽喉   2443篇
儿科学   4454篇
妇产科学   5452篇
基础医学   27216篇
口腔科学   6210篇
临床医学   14509篇
内科学   38417篇
皮肤病学   4090篇
神经病学   13968篇
特种医学   5555篇
外国民族医学   3篇
外科学   25835篇
综合类   5501篇
一般理论   60篇
预防医学   14482篇
眼科学   4074篇
药学   14677篇
中国医学   1063篇
肿瘤学   10625篇
  2021年   2093篇
  2020年   1231篇
  2019年   2217篇
  2018年   3682篇
  2017年   2408篇
  2016年   2526篇
  2015年   3470篇
  2014年   3946篇
  2013年   5434篇
  2012年   9421篇
  2011年   9517篇
  2010年   4911篇
  2009年   3994篇
  2008年   8234篇
  2007年   8643篇
  2006年   8836篇
  2005年   8090篇
  2004年   7430篇
  2003年   6768篇
  2002年   6517篇
  2001年   8294篇
  2000年   8992篇
  1999年   6693篇
  1998年   2037篇
  1997年   1527篇
  1996年   1096篇
  1995年   1006篇
  1992年   3859篇
  1991年   3927篇
  1990年   3640篇
  1989年   3646篇
  1988年   3499篇
  1987年   3340篇
  1986年   3187篇
  1985年   3061篇
  1984年   2157篇
  1983年   1866篇
  1982年   1069篇
  1979年   1959篇
  1978年   1238篇
  1977年   1034篇
  1976年   961篇
  1975年   1217篇
  1974年   1406篇
  1973年   1447篇
  1972年   1369篇
  1971年   1269篇
  1970年   1156篇
  1969年   1141篇
  1968年   1031篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
991.
Over a 36-month period 2800 patients were subjected to extracorporeal shock-wave lithotripsy (ESWL). A total of 5154 procedures were done. Best results were seen with renal pelvic calculi (not larger than 2.5 cm in diameter). Fragments of crushed lower calyceal calculi proved the most difficult to eliminate. As ureteral stone localization approached the bladder, the ESWL results were poorer. Post-ESWL complications were proportional to the stone mass; the higher the mass the more numerous the complications tended to be. Besides erythrocyturia and gross haematuria renal colic was the most frequent complication in almost 60% of the patients. Less prevalent were impacted ureteral stones, subcapsular haematoma and fever. At our institution, thanks to the ESWL method about 80% of the patients were spared surgery.  相似文献   
992.
Dynamic studies of visual capacity for work in individuals working with displays revealed decreased accommodation volume after the long concentration on the display. The total time of work with the display of more than 2h a day involved a decrease of the accommodation volume by 0.42-0.49 diopters and transitory myopia of 0.15-0.21 diopters, as well as increased self-appraisal of fatigue. The system of prophylactic measures including rest breaks, special exercises, massage was worked out and put into practice. Repeated study has proved the effectiveness of suggested measures.  相似文献   
993.
Approximately 60% of Helicobacter pylori isolates in the Western world possess the cytotoxin-associated gene A (cagA). cagA-positive H. pylori is found to be associated with peptic ulcer disease (PUD) and gastric adenocarcinoma. To investigate the cagA status of H. pylori isolates from Chinese patients with PUD and chronic gastritis (CG), H. pylori populations from 83 patients, 48 with PUD and 35 with CG, were assessed by two different cagA-specific PCRs, Southern blotting, and colony hybridization. The combined results from PCR, Southern blotting, and colony hybridization indicate a prevalence of cagA-positive H. pylori isolates of 98% (47 of 48) among Chinese PUD patients and 100% (35 of 35) among Chinese CG patients. Amplification with primer sets 1 and 2 yielded 52 and 95% of the 82 cagA-positive Chinese H. pylori, respectively. In contrast, the sensitivity of cagA-specific PCR for cagA-positive H. pylori isolates from Dutch patients with primer set 1 was 92% (112 of 122) and that with primer set 2 was 91% (50 of 55). The prevalence of cagA-positive H. pylori populations in Chinese patients with PUD and CG is almost universally high. Therefore, cagA cannot be used as a marker for the presence of PUD in Chinese patients. Our data further suggest that allelic variation in cagA may exist and that distinct H. pylori genotypes may circulate in China and Western Europe.  相似文献   
994.
Bronchial hyperresponsiveness (BHR) and damage of the epithelium, as well as eosinophilia in the airway wall, induced by trimellitic anhydride (TMA) in sensitized brown Norway rats were studied. Rats were challenged once or seven times with aerosol of TMA conjugated to rat serum albumin (TMA-RSA) 3 weeks after intradermal TMA sensitization. Airway responsiveness (-log PC300 of acetylcholine i.v.) was measured 24 h after allergen challenge. Epithelial lesion and eosinophil infiltration in the airway walls were quantified under light microscopy, and TMA-specific IgE and IgG in serum were evaluated with ELISA. High levels of TMA-specific IgE and IgG were found in all rats in the sensitized groups compared to nonsensitized groups ( P < 0.001). Repeated allergen challenges of 0.03% TMA-RSA for 7 consecutive days enhanced the level of TMA-specific IgG, compared to single challenge ( P < 0.05). Single allergen challenge of 0.3% TMA-RSA had a nonsignificant tendency to produce BHR in sensitized rats compared to nonsensitized rats ( P =0.06). However, repeated allergen challenges (0.003% and 0.03% TMA-RSA for 7 consecutive days) produced significant BHR in sensitized rats ( P < 0.05). Furthermore, repeated low-dose (0.003%) TMA-RSA challenge produced more BHR than a 10 times higher single dose (0.03%) ( P < 0.05). Slight damage of the airway epithelium was seen in sensitized and repeat-challenged groups. However, bronchial eosinophilia was found in the sensitized and single-challenged groups, but not in nonsensitized nonchallenged, and sensitized repeat-challenged groups ( P < 0.005). We conclude that the brown Norway rat can be sensitized with TMA, and that repeated low-dose allergen challenges produce slight epithelial damage and BHR which is independent of ongoing eosinophilia in the airway wall.  相似文献   
995.
The aim of the study was to determine whether a prior diagnostic testicle biopsy can predict success or failure of testicular sperm extraction (TESE) with intracytoplasmic sperm injection (ICSI) in patients with non-obstructive azoospermia caused by testicular failure, and what is the minimum threshold of sperm production in the testis which must be surpassed for spermatozoa to reach the ejaculate. Forty- five patients with non-obstructive azoospermia caused by testicular failure underwent diagnostic testicle biopsy prior to a planned future TESE-ICSI procedure. The diagnostic testicle biopsy was analysed quantitatively, and correlated with the quantitative findings of spermatogenesis in patients with normal spermatogenesis, as well as with the results of subsequent attempts at TESE-ICSI. Men with non- obstructive azoospermia caused by germinal failure had a mean of 0-6 mature spermatids/seminiferous tubule seen on a diagnostic testicle biopsy, compared to 17-35 mature spermatids/tubule in men with normal spermatogenesis and obstructive azoospermia. These findings were the same for all types of testicular failure whether Sertoli cell only, maturation arrest, cryptorchidism, or post-chemotherapy azoospermia. Twenty-two of 26 men with mature spermatids found in the prior testis biopsy had successful retrieval of spermatozoa for ICSI, 12 of their partners became pregnant, and are either ongoing or delivered. The study suggests that 4-6 mature spermatids/tubule must be present in the testis biopsy for any spermatozoa to reach the ejaculate. More than half of azoospermic patients with germinal failure have minute foci of spermatogenesis which are insufficient to produce spermatozoa in the ejaculate. Prior diagnostic testicle biopsy analysed quantitatively (for the presence of mature spermatids) can predict subsequent success or failure with TESE-ICSI. Incomplete testicular failure may involve a sparse multi-focal distribution of spermatogenesis throughout the entire testicle, rather than a regional distribution. Therefore, it is possible that massive testicular sampling from many different regions of the testes may not be necessary for successful TESE-ICSI.   相似文献   
996.
Intragastral administration of the pesticides Sumi-alpha and Omait to rats significantly increases the number of parietal microorganisms in the jejunum, ileum, and particularly in the cecum. Electron microscopy shows that parietal microorganisms invade goblet cells during secretion and then enter prismatic cells via the lateral plasma membrane. The number of parietal microorganisms entering enterocytes after Sumi-alpha is higher than after less toxic Omait, reaching the maximum 5 h after administration. Translated fromByulleten’ Eksperimental’noi Biologii i Meditsiny, Vol. 123, No. 4, pp. 467–470, April, 1997  相似文献   
997.
998.
999.
丁丙啡用于海洛因依赖的快速戒毒   总被引:1,自引:0,他引:1  
  相似文献   
1000.
目的:观察丁基苯酞(NBP)对大鼠局灶性脑缺血及重灌后海马,纹状体和皮层中TXB2及6-keto-PGF1α含量的影响,方法:尼龙线栓塞法造成大鼠局灶性脑缺血模型,TXB2和6-keto-PGF1α用放免法测定。结果:NBP10mg.kg^-1治疗对缺血重灌注后脑组织中TXB2的产生具有抑制作用,但对6-keto-PGF1α的产生无明显作用,NBP20mg.kg^-1治疗后,重灌5min缺血脑组织  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