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   914235篇
  免费   55343篇
  国内免费   2373篇
耳鼻咽喉   12757篇
儿科学   28550篇
妇产科学   24628篇
基础医学   128781篇
口腔科学   24612篇
临床医学   81240篇
内科学   172049篇
皮肤病学   20334篇
神经病学   68146篇
特种医学   36214篇
外国民族医学   170篇
外科学   136612篇
综合类   20772篇
现状与发展   5篇
一般理论   216篇
预防医学   62379篇
眼科学   20565篇
药学   73003篇
  55篇
中国医学   3600篇
肿瘤学   57263篇
  2021年   7888篇
  2019年   7822篇
  2018年   10684篇
  2017年   8422篇
  2016年   9341篇
  2015年   10761篇
  2014年   14434篇
  2013年   20333篇
  2012年   28272篇
  2011年   29414篇
  2010年   17431篇
  2009年   16149篇
  2008年   26546篇
  2007年   28239篇
  2006年   28623篇
  2005年   27055篇
  2004年   25880篇
  2003年   24718篇
  2002年   23765篇
  2001年   49297篇
  2000年   50088篇
  1999年   41616篇
  1998年   10300篇
  1997年   9162篇
  1996年   9109篇
  1995年   8551篇
  1994年   7705篇
  1993年   7276篇
  1992年   30650篇
  1991年   29302篇
  1990年   28852篇
  1989年   27788篇
  1988年   24900篇
  1987年   24210篇
  1986年   22825篇
  1985年   21339篇
  1984年   15472篇
  1983年   13010篇
  1982年   7064篇
  1979年   13880篇
  1978年   9199篇
  1977年   8270篇
  1976年   7142篇
  1975年   8031篇
  1974年   9375篇
  1973年   9038篇
  1972年   8689篇
  1971年   8186篇
  1970年   7457篇
  1969年   7145篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
92.
The aim of this study was to investigate the role of the nitric oxide (NO) system in ovarian function, by determining if arginine (Arg) supplementation impacts follicle number, cell proliferation, and expression of the NO system members in nutritionally compromised ewes. Ewes were randomly assigned into maintenance (C, 100% requirements), excess (O; 2xC), or restricted (U; 0.6xC) diets 8 weeks prior to Arg treatment. Ewes were individually fed twice daily with pelleted diets. Ewes from each nutritional group were randomly assigned to one of two treatments: saline or Arg, which was initiated on day 0 of the estrous cycle and administered 3 times per day. Ovaries were collected at the early-luteal, mid-luteal and late-luteal/follicular phases of the estrous cycle to determine 1) the number of surface follicles, 2) follicle cell proliferation marked by Ki67 protein expression, and 3) expression of endothelial nitric oxide (eNOS; NOS3) and soluble guanylyl cyclase beta (sGC; GUCY1B3) protein and mRNA in granulosa (G) and theca (T) layers using immunohistochemistry followed by image analysis and qPCR, respectively. During nutritional treatment, C maintained body weight, O gained 6±1.2 kg, and U lost 14±1.3 kg. Our data show that: 1) Ki67 was expressed in all ovarian compartments, eNOS protein was detected in blood vessels of T and stroma, and sGC protein was detected in T cells, and blood vessels of T layer and other ovarian compartments; 2) plane of nutrition affected the number of surface follicles, and thus folliculogenesis, cell proliferation in the T layer, eNOS and sGC protein expression in T, and NOS3 and GUCY1B3 mRNA expression in G; 3) Arg treatment affected cell proliferation in G and T, eNOS and sGC protein expression in T, mRNA expression of NOS3 in T in all groups, and GUCY1B3 in G depending on the stage of the estrous cycle; and 4) G and T cell proliferation, and expression of eNOS and sGC protein in T was affected by the stage of the estrous cycle. Our data demonstrated that plane of nutrition and Arg are involved in the regulation of follicular functions in non-pregnant sheep.  相似文献   
93.
94.
Alpha-1-acid glycoprotein (AGP-1) is a major positive acute phase glycoprotein with unknown functions that likely play a role in inflammation. We tested its involvement in a variety of inflammatory responses using human AGP-1 purified to apparent homogeneity and confirmed its identity by immunoblotting and mass spectrometry. AGP-1 alone upregulated MAPK signaling in murine peritoneal macrophages. However, when given in combination with TLR ligands, AGP-1 selectively augmented MAPK activation induced by ligands of TLR-2 (Braun lipoprotein) but not TLR-4 (lipopolysaccharide). In vivo treatment of AGP-1 in a murine model of sepsis with or without TLR-2 or TLR-4 ligands, selectively potentiated TLR-2-mediated mortality, but was without significant effect on TLR-4-mediated mortality. Furthermore, in vitro, AGP-1 selectively potentiated TLR-2 mediated adhesion of human primary immune cell, neutrophils. Hence, our studies highlight a new role for the acute phase protein AGP-1 in sepsis via its interaction with TLR-2 signaling mechanisms to selectively promote responsiveness to one of the two major gram-negative endotoxins, contributing to the complicated pathobiology of sepsis.  相似文献   
95.
Current models describing HLA epitopes are both theoretical and empirical. Each has limitations yielding discordant results and increasingly complex modeling. The models make a priori assumptions that epitopes must be present only on the mature protein, solvent accessible, on the ‘top’ (peptide binding surface) of the molecule, restricted to the same class as the antibody, and in the same position on the target allele if reactive to more than one locus. Results obtained counter to these assumptions are routinely discounted. For the 17th International Histocompatibility and Immunogenetics Workshop, we developed a reverse engineering algorithm to define epitopes without these assumptions on a cohort of 332 primary transplant pairs. Complete NGS typing of the transcribed (including leader) genomic DNA for 11 HLA loci of donor and recipient and DSA assignment by single antigen beads was performed. Our results show that, when grouped by 16 class I and II allele specific DSA, uniform clusters and 172 specific amino acid target epitopes are recognized by recipients despite originating from disparate HLA pairs. Data also show that these targets can be in the leader, alpha 3, transmembrane and cytoplasmic domains, thus calling into question current assumptions regarding immunogenic epitopes. Comparisons of amino acid epitopes defined by the Terasaki and Duquesnoy groups (TerEp and EpRegistry) are given.  相似文献   
96.
Neuroscience and Behavioral Physiology - Objective. To assess the dynamics of recovery of motor, speech, and autonomous functions in patients with ischemic stroke (IS) using music therapy....  相似文献   
97.
Parasitology Research - Aeromonas hydrophila, considered as an emerging pathogen, is increasingly involved in opportunistic human infections. This bacterium, mainly present in aquatic environments,...  相似文献   
98.
Vanillylmandelic acid, a catecholamine end-metabolite, has been shown to have several biological properties in previous studies, despite considered biologically inactive. We examined the potential effects of vanillylmandelic acid on the ischemic heart following myocardial infarction and reperfusion on a rat model. Thirty-four female Wistar rats were randomized into two groups, control and experimental. They were anesthetized and subjected to myocardial infarction through left anterior descending artery ligation. A previously studied dose of vanillylmandelic acid (10 mg/kg) was administered and the following parameters were studied during ischemia and reperfusion: a) mortality b) severity of ventricular tachyarrhythmias c) premature ventricular contractions and d) heart rate. Administration of vanillymandelic acid significantly reduced the severity of ventricular tachyarrhythmias and mortality rate during reperfusion, while it did not affect any other of the parameters studied. In conclusion, reperfusion injury was blunted through vanillylmandelic acid administration, which seems to be mediated by parasympathetic activation.  相似文献   
99.
Frequently, patients receiving parenteral nutrition (PN) report hunger during the parenteral infusion, yet experience early satiety once PN is tapered off. Post-PN satiety can interfere with the ability to consume enough nutrients to maintain body weight and nutritional status. Factors such as caloric quantity of infusate, gastric motility changes, and disease pathology have been related to appetite changes. To investigate the effects of PN on food intake and gastric motility without the complicated interactions associated with disease pathology, four normal, healthy rhesus monkeys (Macaca mulatta) were studied. The monkeys were administered PN in amounts ranging from 25% to 100% of their normal daily caloric intake. Food and water were continuously available. PN consistently suppressed voluntary food intake in direct relationship to the amount of nutrient infused. The frequency of large-amplitude hunger-type gastric contractions decreased from control conditions. Upon cessation of PN, appetite remained suppressed for one to two weeks, indicating a self-limiting physiological basis to post-PN satiety. Thus, reduced appetite following PN termination might occur in the clinical setting and the patients' feelings of satiety may not be completely attributed to lack of cooperation or disease pathology.  相似文献   
100.
Tuberculosis (TB) is described as lethal disease in the world. Resistant to TB drugs is the main reason to have unfavourable outcomes in the treatment of TB. Therefore, new agents to replace existing drugs are urgently needed. Previous reports suggested that InhA inhibitors, an enoyl-ACP-reductase, might provide auspicious candidates which can be developed into novel antitubercular agents. In this review, we explain the role of InhA in the resistance of isoniazid. Furthermore, five classes of InhA inhibitors, which display novel binding modes and deliver evidence of their prosperous target engagement, have been debated.  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