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   258375篇
  免费   23352篇
  国内免费   5897篇
耳鼻咽喉   3781篇
儿科学   4888篇
妇产科学   4419篇
基础医学   18722篇
口腔科学   8419篇
临床医学   29006篇
内科学   24864篇
皮肤病学   3009篇
神经病学   12513篇
特种医学   6858篇
外国民族医学   16篇
外科学   24153篇
综合类   39763篇
现状与发展   10篇
一般理论   27篇
预防医学   37725篇
眼科学   2745篇
药学   24565篇
  541篇
中国医学   29916篇
肿瘤学   11684篇
  2024年   1249篇
  2023年   5448篇
  2022年   9795篇
  2021年   13059篇
  2020年   12933篇
  2019年   13694篇
  2018年   12209篇
  2017年   11053篇
  2016年   10035篇
  2015年   9417篇
  2014年   18006篇
  2013年   18500篇
  2012年   16013篇
  2011年   16833篇
  2010年   13442篇
  2009年   11866篇
  2008年   11157篇
  2007年   11090篇
  2006年   9594篇
  2005年   7959篇
  2004年   6605篇
  2003年   5766篇
  2002年   4471篇
  2001年   3695篇
  2000年   3198篇
  1999年   2578篇
  1998年   2040篇
  1997年   1842篇
  1996年   1496篇
  1995年   1421篇
  1994年   1256篇
  1993年   1114篇
  1992年   1009篇
  1991年   874篇
  1990年   755篇
  1989年   735篇
  1988年   666篇
  1987年   603篇
  1986年   537篇
  1985年   1805篇
  1984年   2084篇
  1983年   1299篇
  1982年   1721篇
  1981年   1195篇
  1980年   1017篇
  1979年   909篇
  1978年   739篇
  1977年   554篇
  1976年   694篇
  1975年   478篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
951.
Trichosporon is a common cause of superficial mycotic infection but has rarely been associated with endocarditis. The case of a patient who had a peritoneovenous shunt for chronic intractable ascites due to Laennec liver cirrhosis is described. The shunt was revised on several occasions, and the last procedure was complicated by a draining skin sinus wound. To the authors' knowledge, this is the first reported case of Trichosporon endocarditis complicating a peritoneovenous shunt.  相似文献   
952.
Twenty-nine patients with asthma and aspirin-sensitivity were studied in an attempt to induce tolerance to aspirin (ASA). Starting with the smallest ASA doses eliciting bronchial obstruction (threshold doses) we doubled the doses on subsequent days and finally achieved good tolerance of 600 mg ASA per day in 27 patients. It was more difficult to achieve tolerance in patients with low ASA-thresholds than in patients with high ones. Daily ASA administration led to prolongation of the refractory state but when the intervals between consecutive doses were increased, aspirin hypersensitivity recurred. The pause sufficient for a recurrence of sensitivity to ASA was measured in 16 patients and ranged from 24 h to 9 days. Twelve patients challenged with indomethacin after ASA-desensitisation showed good drug tolerance.  相似文献   
953.
For evaluation of the degree of senescence in SAM-P, accelerated senescence prone mouse, formerly called SAM or prone series or P-series, consisting of SAM-P/1, SAM-P/2, SAM-P/3 and SAM-P/4 corresponding to P-1, P-2, P-3 and P-4 series, respectively, in the previous reports, and in SAM-R, accelerated senescence resistant mouse, formerly called resistant series or R-series, consisting of SAM-R/1, SAM-R/2 and SAM-R/3 corresponding to R-1, R-2 and R-3 series, respectively, in the previous reports, the grading score system was adopted. The items to be examined in this system include 11 categories selected from the clinical signs and gross lesions considered to be associated with the aging process. The degree of the senescence in each category was graded from 0 to 4 according to the detailed criteria devised in our laboratory. After 8 months of age each mouse was examined every 4 months, and some of the mice were examined after 2 months of age.In almost all categories, the grading score and incidence began to increase from 4 or 6 months of age and continued to increase with advancing age in both SAM-P and SAM-R. The increase, however, was more marked in SAM-P than in SAM-R. The slow but steady increase in the SAM-R levelled out at 24 months of age and was comparable to that of 12 months of age in SAM-P. In both SAM-P/1 at 8 months of age and SAM-R/2 at 12 months of age, there was a significant reverse correlation between total score of this grading score system and length of residual life after examination.Systematic and extensive studies using the grading score system showed that if the validity of the system is, based on “irreversibility” and “universality” of the changes in  相似文献   
954.
In order to delineate parameters that might discriminate between allergic subjects who develop R or R-P symptoms during natural antigen exposure, 26 subjects allergic to grass or ragweed pollen were classified into R or R-P groups, and then the antigen sensitivity and degree of in vivo mediator release were compared. Antigen-skin sensitivity was quantitated by dilutional skin-test titration, and bronchial sensitivity was quantitated by the amount of inhaled antigen required to receive the FEV1 by 20%. Mediator release was determined by measuring the amount of histamine that was released into skin chambers during antigen incubation and the rise in plasma histamine and serum NCA during antigen-induced bronchospasm. Compared to the 13 R subjects, the 13 R-P subjects were: (1) more sensitive to antigen by both skin-test and inhalation challenge, (2) responded to inhalation of antigen with a greater fall in FEV1 and a greater rise in serum NCA and plasma histamine, and (3) released more histamine into skin chambers after antigen incubation. Even when R and R-P subjects were matched by comparing only subjects with equal skin sensitivity to antigen, greater increases in serum NCA and plasma histamine occurred after inhalation of antigen in the R-P subjects. These data are consistent with the hypothesis that allergic rhinitis subjects who develop pulmonary symptoms during natural pollen exposure are more sensitive to antigen and release more mediators in response to antigen administration. It is therefore possible that the degree of mediator release may be an important factor in determining the pattern of clinical responses to antigen exposure.  相似文献   
955.
Joshi S  Pleij CW  Haenni AL  Chapeville F  Bosch L 《Virology》1983,127(1):100-111
The existence of subgenomic RNAs is well established in the case of plant viruses such as tobacco mosaic virus (TMV). However, except for the subgenomic coat protein mRNA, it is not known whether the other subgenomic RNAs have a function in the life cycle of the virus. In search of more information about one of the major subgenomic RNAs-intermediate length RNA-2 or I2 RNA-of TMV, in vitro and in vivo translational studies were performed. The I2 RNA, which codes in vitro for the synthesis of a 30K (K = kilodalton) protein, appears to be uncapped as judged by the need of different in vitro translation conditions for the synthesis of this protein, compared to the conditions required for the synthesis of the 126K and 183K proteins coded by the capped genomic RNA. In vivo a protein migrating in the same position as the 30K protein synthesized in vitro can be detected in infected tobacco leaves. Since this protein occurs transiently early upon infection, whether it is virus-coded or virus-induced, it could have an early function during infection.  相似文献   
956.
A newborn infant was referred because of low-set ears, mild downward slant of the palpebral fissues, micrognathia with higharched palate, a flat midface, small mouth, and thin upper lip with cupid bow configuration. To some extent her cry resembled that associated with cri du chat syndrome. Cytogenetic findings with G- and Q-banding alone failed to characterize precisely the complex translocations. By the chromosome in situ suppression (CISS) hybridization technique using whole chromosome specific probes, a complex 4 breakpoint rearrangement involving both arms of a single chromosome 1 with the long arms of chromosome 5 and 11 was disclosed, i.e., 46,XX, der(1),t(1;5) t(1;11) (5qter→5q31::1p31.3→1q44::11q23→11qter;5pter→5q31::1p31.3→1pter;11pter→11q23::1q44→1qter). Gene deregulation and position effect may explain the multiple anomalies in individuals with apparently balanced translocations may shed some light towards unveiling the clinical consequences associated with aberrations which are presumably balanced. © 1993 Wiley-Liss, Inc.  相似文献   
957.
目的:研究碱性成纤维细胞生长因子(bFGF)对人卵巢癌CAOV3细胞细胞周期调节蛋白cyclinD1及GADD153表达的影响,探讨bFGF促进人卵巢癌CAOV3细胞增殖、抑制凋亡的信号机制。方法:利用无血清饥饿诱导卵巢癌CAOV3细胞凋亡。分为对照组、bFGF组。分别应用MTT、流式细胞术、琼脂糖凝胶电泳观察25、50、75μg/L bFGF对CAOV3细胞增殖率、细胞周期及细胞凋亡的影响。利用Western blotting检测bFGF对CA-OV3细胞cyclin D1、GADD153以及转录因子(c-Fos、c-Jun)表达的影响。结果:与对照组相比,bFGF呈剂量依赖性加速CAOV3细胞细胞周期进程,促进细胞增殖,抑制饥饿诱导的凋亡(P<0.01);呈时间依赖性促进cyclinD1、c-Fos、c-Jun,抑制GADD153蛋白表达(P<0.01)。结论:bFGF可能通过上调cyclin D1、c-Fos、c-Jun,下调GADD153表达促进细胞增殖,抑制饥饿诱导的卵巢癌CAOV3细胞凋亡。  相似文献   
958.
男医学生在妇产科实习的素质能力培养   总被引:1,自引:0,他引:1  
21世纪需要高素质人才,素质教育是关键。从一定意义上说素质教育就是因材施教,妇产科作为一门比较特殊的学科,在实践教学工作中女患者不愿意示教的情况越来越严重,尤其对于男医学生。本文对男医学生在妇产科实习的素质能力培养进行实践与研究,提出以素质教育为中心,培养出具备高尚的医德、扎实的专业本领和丰富的人文知识的新型人才。  相似文献   
959.
Congenital insensitivity to pain with anhidrosis (CIPA), also referred to as hereditary sensory and autonomic neuropathy type IV (HSAN‐IV), is an autosomal recessive hereditary disorder characterized by recurrent episodic fever, anhidrosis (inability to sweat), absence of reaction to noxious stimuli, self‐mutilating behavior, and mental retardation. The TRKA (NTRK1) gene located on chromosome 1 (1q21‐q22), consists of 17 exons and spans at least 23 kb. TRKA encodes the receptor tyrosine kinase (RTK) for nerve growth factor (NGF) and is the gene responsible for CIPA. Defects in NGF signal transduction at the TRKA receptor lead to failure to support survival of sympathetic ganglion neurons and nociceptive sensory neurons derived from the neural crest. Thirty‐seven different TRKA mutations, identified in patients in various countries, including nine frameshift, seven nonsense, seven splice, and 14 missense mutations, are distributed in an extracellular domain involved in NGF binding, as well as in the intracellular signal‐transduction domain. Extensive analysis of CIPA mutations and associated intragenic polymorphisms should facilitate detection of CIPA mutations and aid in the diagnosis and genetic counseling of this painless but severe genetic disorder with devastating complications. In addition, naturally occurring TRKA missense mutations with loss of function provide considerable insight into the structure–function relationship in the RTK family. Further, molecular pathology of CIPA would provide unique opportunities to explore critical roles of the autonomic sympathetic nervous system as well as peripheral sensory nervous system that transmit noxious stimuli in humans. Hum Mutat 18:462–471, 2001. © 2001 Wiley‐Liss, Inc.  相似文献   
960.
广州市1996—2005年管网末梢水卫生状况及对策分析   总被引:1,自引:0,他引:1  
目的了解广州市管网末梢水的水质情况,为随时监测全市生活饮用水水质的动态变化提供信息并提出改进措施。方法对广州市1996—2005年管网末梢水水质监测资料进行统计,按照GB5749—85《生活饮用水卫生标准》和卫生部《生活饮用水卫生规范》(2001年)进行分析评价。结果共监测606份水样,合格155份,合格率为25.58%。不合格的项目主要有锰、游离余氯、细菌总数、色度、铁和耗氧量。在广州市疾病预防控制中心检测的项目中,锰的合格率仅为59.57%,游离余氯的合格率为76.73%,细菌总数的合格率为85.81%,色度的合格率为88.12%,铁的合格率为88.94%,耗氧量的合格率为96.37%。结论广州市管网末梢水的锰、游离余氯、细菌总数和铁等项目合格率较低,今后应加强饮水的氯化消毒、对管网的定期检修和冲洗、减少二次供水水箱的使用和设立管网水水质自动监测系统。  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