全文获取类型
收费全文 | 7557篇 |
免费 | 643篇 |
国内免费 | 306篇 |
专业分类
耳鼻咽喉 | 33篇 |
儿科学 | 181篇 |
妇产科学 | 86篇 |
基础医学 | 668篇 |
口腔科学 | 125篇 |
临床医学 | 688篇 |
内科学 | 1082篇 |
皮肤病学 | 110篇 |
神经病学 | 500篇 |
特种医学 | 172篇 |
外国民族医学 | 2篇 |
外科学 | 614篇 |
综合类 | 705篇 |
现状与发展 | 2篇 |
一般理论 | 1篇 |
预防医学 | 761篇 |
眼科学 | 324篇 |
药学 | 1439篇 |
7篇 | |
中国医学 | 583篇 |
肿瘤学 | 423篇 |
出版年
2024年 | 32篇 |
2023年 | 155篇 |
2022年 | 261篇 |
2021年 | 451篇 |
2020年 | 344篇 |
2019年 | 313篇 |
2018年 | 286篇 |
2017年 | 297篇 |
2016年 | 268篇 |
2015年 | 284篇 |
2014年 | 415篇 |
2013年 | 591篇 |
2012年 | 361篇 |
2011年 | 363篇 |
2010年 | 318篇 |
2009年 | 297篇 |
2008年 | 282篇 |
2007年 | 279篇 |
2006年 | 274篇 |
2005年 | 227篇 |
2004年 | 235篇 |
2003年 | 210篇 |
2002年 | 169篇 |
2001年 | 163篇 |
2000年 | 129篇 |
1999年 | 111篇 |
1998年 | 115篇 |
1997年 | 89篇 |
1996年 | 85篇 |
1995年 | 87篇 |
1994年 | 72篇 |
1993年 | 67篇 |
1992年 | 57篇 |
1991年 | 72篇 |
1990年 | 60篇 |
1989年 | 55篇 |
1988年 | 57篇 |
1987年 | 47篇 |
1986年 | 45篇 |
1985年 | 69篇 |
1984年 | 84篇 |
1983年 | 40篇 |
1982年 | 60篇 |
1981年 | 50篇 |
1980年 | 32篇 |
1979年 | 30篇 |
1978年 | 18篇 |
1977年 | 37篇 |
1976年 | 18篇 |
1973年 | 13篇 |
排序方式: 共有8506条查询结果,搜索用时 46 毫秒
61.
Molecular cloning and complete nucleotide sequence of the genome of Japanese encephalitis virus Beijing-1 strain 总被引:5,自引:0,他引:5
Hiroshi Hashimoto Akio Nomoto Koji Watanabe Takayuki Mori Toshiyuki Takezawa Chikara Aizawa Tsutomu Takegami Keiichi Hiramatsu 《Virus genes》1988,1(3):305-317
The genomic RNA of the Japanese encephalitis virus (JEV) Beijing-1 strain was reversely transcribed and the synthesized cDNA was molecularly cloned. Six continuous cDNA clones that cover the entire virus genome were established and sequenced to determine the complete nucleotide sequence of the JEV RNA. The precise genomic size was estimated as 10,965 bases long. With flanking 95 bases at the 5 and 583 bases at the 3 non-coding regions, one long open reading frame (ORF) was revealed encoding a virus polyprotein with 3,429 amino acid residues. Because of sequence homologies observed between JEV and other flaviviruses, the genome organization of JEV appears to be identical with other flaviviruses. Genetic variation detected among flavivirus genomes is consistent with the established serological relatedness between JEV and other members of flaviviruses. The secondary structure of the JEV genome is deduced and discussed concerning its involvement in genome replication. 相似文献
62.
目的探讨中专学生网络使用情况及与社会心理因素之间的关系,为解决网络成瘾问题提供理论依据。方法选取中专学生231人作为研究对象,收回有效问卷229份(有效率为99.13%)。其中男生97人,女生134人,平均年龄18±1岁。使用一般资料调查表、网络成瘾量表和症状自评量表对学生进行测试。结果判断为轻度网络成瘾者占受试的6.98%,判断为网络使用过度占受试的14.41%。网络成瘾量表得分与男性、计算机专业相关,与SCL-90各因子之间均成正相关,均有统计学显著差异。多因素线性回归分析发现:男性、计算机专业、精神病性因子和敌对性是影响网络使用的危险因素。结论中专学生网络使用情况与心理社会因素关系密切,预防网络成瘾应从性别和个体的心理特点出发。 相似文献
63.
《Research in microbiology》2021,172(6):103870
We previously reported the complete genome of Streptomyces lavendulae subsp. lavendulae CCM 3239, containing the linear chromosome and the large linear plasmid pSA3239. Although the chromosome exhibited replication features characteristic for the archetypal end-patching replication, it lacked the tap/tpg gene pair for two proteins essential for this process. However, this archetypal tpgSa-tapSa operon is present in pSA3239. Complete genomic sequence of the S. lavendulae Del-LP strain lacking this plasmid revealed the circularization of its chromosome with a large deletion of both arms. These results suggest an essential role of pSA3239-encoded TapSa/TpgSa in the end-patching replication of the chromosome. 相似文献
64.
中学生生活事件与抑郁的关系 总被引:32,自引:3,他引:32
目的:探讨中学生具体生活事件和抑郁状况的关系。方法:采用青少年生活事件量表和中学生抑郁量表对558名中学生进行问卷调查。结果:除个别生活事件项目外,青少年生活事件量表中的多数项目均与中学生抑郁呈显著正相关;生活事件与抑郁的回归分析表明,学习负担重,受人歧视冷遇,不喜欢上学,家庭经济困难,与同学或好友发生纠纷,升学压力,被盗或丢失东西,考试失败或不理想,受批评或处分,生活习惯明显变化,恋爱不顺利或失恋,被罚款等12类生活事件进入了对抑郁的回归方程,对抑郁的预测作用较大。结论:中学生生活事件与其抑郁存在广泛的正相关关系。12项生活事件对中学生抑郁有较大的预测作用。 相似文献
65.
van der Graaf M Janssen SW van Asten JJ Hermus AR Sweep CG Pikkemaat JA Martens GJ Heerschap A 《NMR in biomedicine》2004,17(6):405-410
Localized in vivo 1H magnetic resonance spectroscopy (MRS) was used to investigate metabolite levels in the brain of adult Zucker Diabetic Fatty (ZDF) rats, an animal model for type 2 diabetes mellitus. This study focussed on the hippocampus, assumed to be one of the main brain areas affected by this disease. Together with an almost 5-fold increase in blood glucose concentration measured by glucose oxidation, significant increases were found in the hippocampal concentrations of glucose (4.93 vs 1.66 mM p < 0.001), myo-inositol (6.52 vs 4.30 mM; p < 0.05), and total creatine (12.71 vs 10.50 mM; p < 0.05) in ZDF rats (n = 5) compared with littermates (n = 5). Although no obvious alterations were detected in the hippocampal levels of other metabolites, including NAA + NAAG and choline-containing compounds in the ZDF rats, the increase in Glc and Ins levels is in line with elevated brain tissue contents of these metabolites in patients with diabetes mellitus. 相似文献
66.
中小学教师心理控制源、应付方式与自我和谐的关系 总被引:2,自引:0,他引:2
目的考察中小学教师自我和谐、心理控制源、应付方式的状况及其关系。方法使用自我和谐量表、内控性、有势力的他人及机遇量表、应付方式问卷对200名中小学教师进行调查。结果①教师整体上倾向内控,使用最多的应付方式是解决问题,最少的是自责;②任教地点、职务、职称、学历不同的教师自我和谐、应付方式有显著差异,年龄、教龄、任班主任年限、自评心理健康水平、生活压力、工作满意度与心理控制源、应付方式、自我和谐的不同维度相关显著;③机遇和幻想对自我和谐有正向预测作用,内控、解决问题、求助对自我和谐有负向预测作用。结论自我和谐可以作为衡量心理健康水平的一个标志,中小学教师心理控制源与应付方式对自我和谐有重要影响。 相似文献
67.
Cloning and characterization of the cDNA encoding the HA protein of a hemagglutination-defective measles virus strain 总被引:3,自引:0,他引:3
Hiroyuki Saito Hiroyasu Sato Mariko Abe Seizaburo Harata Ken-Ichi Amano Tsunehisa Suto Morihiro Morita 《Virus genes》1994,8(1):107-113
cDNA clones corresponding to the mRNA for the hemagglutinin of the hemagglutination-defective strain AK-1 of measles virus were isolated and characterized. Compared with the prototype Edmonstron strain, 60 nucleotide substitutions that resulted in 18 amino acid changes were detected. An additional potential N-linked glycosylation site was added by point mutation, which was supported by the observation that the hemagglutinin of the AK-1 strain was stained more heavily after NaDodSO4PAGE and periodic acid-Schiff (PAS) staining than the Edmonston strain. Computer-assisted analysis revealed that three reverse turns in the secondary structure had disappeared in the hemagglutinin of the AK-1 strain. Moreover, one of these structural changes occurred in the closely glycosylated region at amino acid residues 168–240, which appeared to be a biologically important functional domain. The isoelectric point calculated from the predicted amino acid sequence became about 1 pH unit more basic in the AK-1 strain than the Edmonston strain. This present study is the first sequence analysis of the hemagglutinin gene in a hemagglutination-defective strain of the measles virus. 相似文献
68.
Visualizing metabolic changes in breast-cancer tissue using 1H-NMR spectroscopy and self-organizing maps 总被引:8,自引:0,他引:8
In-vitro NMR spectroscopic examinations of tissue extracts can be combined with appropriate pattern-recognition and visualization techniques in order to monitor characteristic metabolic differences between tissue classes. In the present study, such techniques are applied to a set of 88 breast-tissue samples with the intention of identifying typical differences between various tissue classes. The set contains 49 breast-tumor samples of various tumor grades and 39 samples of healthy tissue. The metabolite compositions of the tissue extracts were investigated using a dual extraction technique and high-resolution (1)H-NMR spectroscopy. The spectra of the hydrophilic and the lipophilic compounds were assigned to three groups according to different malignancy grades of the respective tissue samples. The group characteristics were analyzed using the k-nearest-neighbor method and self-organizing-map visualizations. The results show an increase of UDP-hexose, phosphocholine and phosphoethanolamine concentrations according to the tumor grade. Higher concentrations of taurine were detected in the malignant samples. Myo-inositol and glucose content were elevated in control samples compared with malignant tissue. Both compounds also characterized different subgroups in the pool of unaffected tissue samples depending upon fat content or fibrosis. Several lipid metabolites showed a characteristic elevation with high malignancy. 相似文献
69.
Adriana C. Gittenberger‐De Groot Edris A.F. Mahtab Nathan D. Hahurij Lambertus J. Wisse Marco C. Deruiter Maurits C.E.F. Wijffels Robert E. Poelmann 《Anatomical record (Hoboken, N.J. : 2007)》2007,290(1):115-122
Recent advances in the study of cardiac development have shown the relevance of addition of myocardium to the primary myocardial heart tube. In wild‐type mouse embryos (E9.5–15.5), we have studied the myocardium at the venous pole of the heart using immunohistochemistry and 3D reconstructions of expression patterns of MLC‐2a, Nkx2.5, and podoplanin, a novel coelomic and myocardial marker. Podoplanin‐positive coelomic epithelium was continuous with adjacent podoplanin‐ and MLC‐2a‐positive myocardium that formed a conspicuous band along the left cardinal vein extending through the base of the atrial septum to the posterior myocardium of the atrioventricular canal, the atrioventricular nodal region, and the His‐Purkinje system. Later on, podoplanin expression was also found in the myocardium surrounding the pulmonary vein. On the right side, podoplanin‐positive cells were seen along the right cardinal vein, which during development persisted in the sinoatrial node and part of the venous valves. In the MLC‐2a‐ and podoplanin‐positive myocardium, Nkx2.5 expression was absent in the sinoatrial node and the wall of the cardinal veins. There was a mosaic positivity in the wall of the common pulmonary vein and the atrioventricular conduction system as opposed to the overall Nkx2.5 expression seen in the chamber myocardium. We conclude that we have found podoplanin as a marker that links a novel Nkx2.5‐negative sinus venosus myocardial area, which we refer to as the posterior heart field, with the cardiac conduction system. Anat Rec, 290:115–122, 2007. © 2006 Wiley‐Liss, Inc. 相似文献
70.
Frederick J Hardie M Reid M Fletcher H Wynter S Frederick C 《Human reproduction (Oxford, England)》2002,17(11):2967-2971
BACKGROUND: This prospective study was designed to evaluate the operative morbidity and reproductive outcome in patients who had secondary myomectomy for recurrent symptomatic uterine fibroids. METHODS: A total of 58 women were subjected to a secondary myomectomy via the abdominal route. The operative morbidity such as blood loss, presence of adhesions and febrile index were estimated and the pregnancy outcome over a 2-4 year period of follow-up. RESULTS: The mean age and standard deviation (+/- SD) of the women was 35 (+/- 2.4) years. Nineteen patients (33%) had a postoperative temperature vertical line 100 degrees F and the estimated blood loss ranged from 159-2500 ml (median 700 ml). Seven patients (12%) required blood transfusion and one had a hysterectomy due to haemorrhage. Nine women (15.5%) became pregnant but only five (56%) had live births. Those with successful pregnancies tended to be younger with a mean age of 31.8 (+/- 2.6) years versus 35 (+/- 1.8) years, (P = 0.08, non-significant) and had fewer uterine leiomyomata; median with range values, 2 (1-6) versus 7 (6-15). The variables which best predicted the postoperative likelihood of pregnancy were; age, presence of tubal adhesions and the number of uterine fibroids. CONCLUSION: This prospective study showed a high operative morbidity and a poor fertility outcome after a repeat myomectomy. The factors affecting successful outcome in a logistic regression model were age, tubal adhesions and number of uterine fibroids. 相似文献