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   454362篇
  免费   294869篇
  国内免费   47025篇
耳鼻咽喉   4366篇
儿科学   7615篇
妇产科学   3700篇
基础医学   102027篇
口腔科学   6597篇
临床医学   83146篇
内科学   112145篇
皮肤病学   6849篇
神经病学   27381篇
特种医学   17465篇
外国民族医学   15篇
外科学   57781篇
综合类   108471篇
现状与发展   58篇
一般理论   5篇
预防医学   64780篇
眼科学   21423篇
药学   83007篇
  338篇
中国医学   63868篇
肿瘤学   25219篇
  2023年   5341篇
  2022年   11102篇
  2021年   13233篇
  2020年   14063篇
  2019年   16733篇
  2018年   17302篇
  2017年   19441篇
  2016年   16759篇
  2015年   20806篇
  2014年   23122篇
  2013年   25704篇
  2012年   31478篇
  2011年   34568篇
  2010年   34828篇
  2009年   40373篇
  2008年   28680篇
  2007年   24216篇
  2006年   22100篇
  2005年   19173篇
  2004年   17500篇
  2003年   15353篇
  2002年   14249篇
  2001年   15509篇
  2000年   9998篇
  1999年   13460篇
  1998年   14090篇
  1997年   13997篇
  1996年   15019篇
  1995年   15154篇
  1994年   14897篇
  1993年   13551篇
  1992年   12790篇
  1991年   12161篇
  1990年   11145篇
  1989年   10981篇
  1988年   10539篇
  1987年   9889篇
  1986年   9389篇
  1985年   8464篇
  1984年   6539篇
  1983年   6546篇
  1982年   7605篇
  1981年   7143篇
  1980年   6807篇
  1979年   6642篇
  1978年   5819篇
  1977年   6122篇
  1976年   5743篇
  1975年   5482篇
  1974年   5034篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
82.
BACKGROUND: There is a high non-attendance rate for traditional clinic-based routine asthma care in general practice. Alternative methods of providing routine asthma care need to be examined. AIM: To examine the cost and effectiveness of targeted routine asthma care in general practice using telephone triage, compared to usual clinic care. DESIGN OF STUDY: An open randomised controlled trial. SETTING: A single semi-rural practice in the southwest of England. METHOD: Adult patients with asthma were randomised to receive either their routine asthma care in the surgery or care by telephone triage. Asthma control parameters, health status and NHS resource utilisation were measured over the 12-month study period. RESULTS: One hundred and ninety-four patients were randomised and 35% per cent more patients (n = 84 versus n = 62) received more than one consultation in the telephone group. Asthma control as measured by the asthma control questionnaire (ACQ) was similar in the clinic and telephone groups: mean change in ACQ = -0.11 (95% CI = -0.32 to 0.11) versus -0.18 (95% CI = -0.38 to 0.02). Mean NHS costs were 210 pounds sterling per patient per year in the telephone group compared to 334 pounds sterling in the clinic group (P-value of bootstrapped difference = 0.071). CONCLUSION: Targeted routine asthma care by telephone triage of adult asthmatics can lead to more asthma patients being reviewed, at less cost per patient and without loss of asthma control compared to usual routine care in the surgery.  相似文献   
83.
84.
饮食因素与肠道微生态的研究进展   总被引:2,自引:0,他引:2  
微生态学是20世纪兴起的一门生命学科,它是从健康水平研究微生物之间与环境和宿主之间相互依存、相互制约规律的科学。饮食因素对维持肠道微生态的平衡起着重要的作用。本文就肠道菌群与人体健康、饮食因素对肠道菌群的影响以及对菌群失调的调节作用作一综述。  相似文献   
85.
We found multimolecular antigenic mimicry of arthritogenic autoantigens and peptides from several other “self” or foreign antigens sharing amino acid sequence homologies. Many of these new mimotopes induced arthritis and/or uveitis upon immunization in Lewis rats, indicating a role for multiple antigens in the initiation of a certain autoimmune disease.  相似文献   
86.
We have used a three-dimensional diffusion model of calcium entering the presynaptic nerve terminal through discrete channels to simulate experiments relating transmitter release to presynaptic calcium current. The relationship will be less than linear, or will curve downward, if calcium channels are well separated. It will resemble a power-law function with exponent less than the cooperativity of calcium action if channels are clustered closer together. Large presynaptic depolarizations elicit more release than small depolarizations admitting the same calcium influx. This occurs because large pulses open more channels near each other, with the result that the calcium concentration near release sites is greater, due to overlap of calcium diffusing from adjacent channels.  相似文献   
87.
Summary The olfactory epithelium of the adult hamster (Mesocricetus auratus) was examined with the scanning electron microscope following olfactory nerve axotomy. Axotomy results in retrograde degeneration of mature olfactory neurons. Maximum degeneration was observed around day 4. During the degeneration period the epithelium consists primarily of supporting and basal cells. Microvillar columnar supporting cells were observed to have fine cellular processes extending from their lateral border to neighbouring cells. Supporting cells extended to the basal lamina where they terminated in foot-like processes of variable shapes (club, splay and hook). Basal cells which gave rise to new replacement olfactory neurons were observed near the basal lamina. They had a rough cellular surface covered with small granules and fine cellular extensions. Bowman's gland duct cells extended unbranched through the epithelium where they formed funnel duct openings covered with microvilli. During early recovery periods (5–30 days) the number of olfactory neurons in the lower epithelium region increased. We observed olfactory neurons with developing axon and dendritic processes. Specialized growth cone structures were seen at the tips. Olfactory neuron growth cones were elongated or club-shaped and had a ruffled membrane surface. Several thin filopodia extended from the growth cone and made contact with adjacent cells. At late recovery periods (35–120 days) there was a marked increase in the number of olfactory neurons within the middle and lower epithelium regions. Numerous dendritic processes extended to the epithelial surface and terminated in knob-like ciliated structures. Olfactory axons passed basally, forming small intra-epithelial bundles that penetrated the basal lamina then fasciculated into larger bundles within the lamina propria.This study provides detailed three-dimensional observations of the olfactory epithelium following neuron injury, and describes neural degenerative changes, replacement of olfactory neurons, development and maturation. In addition, we describe the structure and basal attachment of supporting cells and their glial-like relation with olfactory neurons.  相似文献   
88.
Summary:  Three chromosomal rearrangements: a balanced reciprocal translocation, t(14;10) (q22;q13), a Y-autosome translocation, t(Y;16) (q11;p13) and a deleted Y chromosome, Yq- were detected among 100 infertile men. The autosomal translocation, associated with oligozoospermia was found to be familial with various effects on the female carriers and the proband's father. The patients with the chromosome Y abberations were found to be azoospermic and might have lost the genes necessary for normal sperma-togenesis.
Zusammenfassung:  Unter 100 infertilen Männern wurden drei Chromosomenneuan-ordnungen entdeckt: eine balancierte reziproke Translokation, t(14;10) (q22;q13), eine Y-autosome Translokation, t(Y;16) (q11;p13) und eine Deletion des Y-Chromosoms, Yq-. Die autosomale Translokation bei Oligozoospermie zeigte sich familiär mit verschiedenen Auswirkungen bei den weiblichen Überträgern und dem Vater des Probanden. Die Patien-ten mit chromosomalen Y-Aberrational wiesen eine Azoospermie auf und scheinen die zur normalen Spermatogenese notwendigen Gene verloren zu haben.  相似文献   
89.
We tested whether hypoglycemia, like hypoxia, would preferentially destroy GABAergic nerve cells in the neocortex. To this end, rat neocortex explants dissected from 6-day-old rat pups and cultured up to a developmental stage approximately comparable to that of the newborn human neocortex, were exposed to hypoglycemia for different periods. Quantitative light microscopic and immunocytochemical evaluation of the cultures demonstrated that hypoglycemia does not preferentially destroy GABAergic but rather non-GABAergic neurons, a finding quite opposite to what was found after hypoxia. Recent biochemical data from other laboratories which seem to support this difference in neuronal vulnerability are discussed. It is concluded that perinatal hypoglycemia may not form such a serious threat with respect to the genesis of epilepsy as does hypoxia.  相似文献   
90.
Processing of a protein antigen into fragments is believed to be a prerequisite for its presentation by the antigen-presenting cell to the T cell. This model would predict that, in oligomeric proteins, T cells prepared with specificity for regions that are buried within subunit association surfaces should recognize the respective regions in vitro equally well on the isolated subunit or on the oligomer. Three hemoglobin (Hb) alpha-chain synthetic peptides, corresponding to areas that are situated either completely [alpha-(31-45)] or partially [alpha-(41-45) and alpha-(81-95)] within the interface between the alpha and beta subunits of Hb, and a fourth peptide representing a completely exposed area in tetrameric Hb were used as immunogens in SJL/J (H-2s) mice. Peptide-primed T cells were passaged in vitro with the respective peptide to obtain peptide-specific T-lymphocyte lines. T-cell clones were isolated from these lines by limiting dilution. T-cell lines and clones that were specific for buried regions in the subunit association surfaces recognized the free peptide and the isolated subunit but not the Hb tetramer. On the other hand, T cells with specificity against regions that are not involved in subunit interaction and are completely exposed in the tetramer recognized the peptide, the isolated subunit, and the oligomeric protein equally well. The responses of the T-cell lines and clones were major histocompatibility complex-restricted. Since the same x-irradiated antigen-presenting cells were employed, the results could not be attributed to differences or defects in Hb processing. The findings indicate that in vitro the native (unprocessed and undissociated) oligomeric protein was the trigger of major histocompatibility complex-restricted T-cell responses.  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