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   5940篇
  免费   360篇
  国内免费   43篇
耳鼻咽喉   60篇
儿科学   104篇
妇产科学   55篇
基础医学   1027篇
口腔科学   66篇
临床医学   488篇
内科学   1071篇
皮肤病学   119篇
神经病学   718篇
特种医学   309篇
外科学   910篇
综合类   16篇
一般理论   3篇
预防医学   147篇
眼科学   236篇
药学   379篇
中国医学   14篇
肿瘤学   621篇
  2024年   4篇
  2023年   51篇
  2022年   93篇
  2021年   142篇
  2020年   109篇
  2019年   134篇
  2018年   143篇
  2017年   113篇
  2016年   177篇
  2015年   218篇
  2014年   243篇
  2013年   312篇
  2012年   468篇
  2011年   471篇
  2010年   290篇
  2009年   268篇
  2008年   408篇
  2007年   430篇
  2006年   399篇
  2005年   422篇
  2004年   380篇
  2003年   334篇
  2002年   281篇
  2001年   63篇
  2000年   42篇
  1999年   32篇
  1998年   49篇
  1997年   25篇
  1996年   31篇
  1995年   21篇
  1994年   25篇
  1993年   20篇
  1992年   9篇
  1991年   13篇
  1990年   9篇
  1989年   11篇
  1988年   3篇
  1987年   4篇
  1986年   6篇
  1985年   7篇
  1984年   6篇
  1983年   14篇
  1982年   12篇
  1981年   6篇
  1980年   3篇
  1979年   5篇
  1978年   7篇
  1977年   4篇
  1972年   6篇
  1965年   4篇
排序方式: 共有6343条查询结果,搜索用时 15 毫秒
161.
162.
A transplanted tumor that induces granulocytosis and produces colony stimulating factor (CSF) was studied in mice during several passages. The sequence of events leading to granulocytosis was characterized. Band granulocytes were increased 3 days after tumor inoculation, while simultaneously CFU-s and CFU-c in bone marrow and spleen were transitorily low. This was followed by rapid accumulation of CFU-c and CFU-s in spleen, and by successive waves of increased mitotable and non-mitotable granulocytes in spleen and marrow. In contrast, marrow CFU-c and CFU-s remained normal or slightly decreased.  相似文献   
163.
164.
165.
BACKGROUND: Psoriatic arthropathy occurs as complicating feature in about 5-7% of psoriasis patients. Infectious mechanisms including viral antigens have been suggested by serologic data as CD8 T cellular specifity towards viral epitopes. OBJECTIVE AND RESULTS: We here reported a case of a 32-year-old male psoriatic arthritis patient, where we could demonstrate simultaneous infection with cytomegalovirus (CMV), herpes simplex virus type I (HSV1) and parvovirus B19 (B19), as well as latent Epstein-Barr virus (EBV) infection within the synovial tissue by immunohistochemistry (CMV, parvovirus B19, HSV1, EBV-LMP) and DNA-in situ-hybridization (CMV). Serologic examination revealed positive EBV and parvovirus B19-IgG-antibodies, but no antibody response to HSV1 and CMV. CONCLUSION: This case is of special interest, since replicative viral infections have not yet been demonstrated localised in the psoriatic arthritis synovia. Thus, with particular regard to the limited information of the serologic data and the possible need of immuno suppressive therapy direct synovial testing for viral antigenes may be considered in psoriatic arthritis patients.  相似文献   
166.
BACKGROUND: In the context of mammalian oocyte maturation, it has been suggested that intermediates of cholesterol biosynthesis may represent the physiological signal that instructs the oocyte to reinitiate meiosis. METHODS: Endogenous levels of follicular fluid meiosis-activating sterol (FF-MAS) were monitored in rabbit ovarian tissue, and the influence of exogenous gonadotrophins on sterol formation was assessed. The involvement of cAMP in FF-MAS-induced versus spontaneous oocyte maturation in vitro in mice was also investigated, as was the direct microinjection of FF-MAS into mouse oocytes. RESULTS: Levels of FF-MAS in rabbit ovaries were significantly elevated 1 h after hCG/LH induction and remained so for 4 and 12 h after induction. In naked oocytes undergoing spontaneous maturation, a significant decrease in cAMP was detected after 30 min of culture. However, FF-MAS-mediated induction of oocyte maturation in hypoxanthine-arrested naked oocytes was not associated with any detectable decrease in intracellular cAMP levels. Microinjected FF-MAS failed to induce any noticeable meiosis. CONCLUSIONS: A rapid increase in FF-MAS level occurred in vivo in the rabbit ovary in response to LH, and clear differences were seen in the cAMP pattern during spontaneous and induced oocyte maturation in mice.  相似文献   
167.
Autosomal recessive hereditary motor and sensory neuropathy or Charcot-Marie-Tooth disease (CMT) is a severe childhood-onset neuromuscular disorder. Autosomal recessive CMT is genetically heterogeneous with one locus mapped to chromosome 11p15 (CMT4B2). The histopathological hallmarks of CMT4B2 are focal outfoldings of myelin in nerve biopsies. Homozygosity mapping, in a Turkish inbred family with four children affected by CMT characterized by focally folded myelin, provided linkage to the CMT4B2 locus. We identified a large, novel gene, named SET binding factor 2 (SBF2), that lies within this interval and is expressed in various tissues, including spinal cord and peripheral nerve. SBF2 is a member of the pseudo-phosphatase branch of myotubularins and was an obvious candidate for CMT4B2 by virtue of its striking homology to myotubularin-related protein 2 (MTMR2), causing another form of autosomal recessive CMT with outfoldings of the myelin sheaths. Molecular study of the SBF2 gene in the CMT4B family demonstrated the presence of a homozygous inframe deletion of SBF2 exons 11 and 12 in all four affected individuals. On the protein level, this mutation is predicted to disrupt an N-terminal domain that is conserved in SBF2 and its orthologues across species. Myotubularin-related proteins have been suggested to work in phosphoinositide-mediated signalling events that may also convey control of myelination. Localization of SBF2 within the candidate interval, cosegregation with the disease, expression in the peripheral nervous system, and resemblance of the histopathological phenotype to that related to mutations in its paralogue MTMR2 indicate that this gene is the CMT4B2 gene.  相似文献   
168.
The microscopic organization of the Göttingen minipig (sus scrofa) hypothalamus was studied using Nissl stain, acetylcholinesterase histochemistry, and immunohistochemical staining for calretinin, tyrosin hydroxylase, oxytocin, vasopressin, and orexin A.Mediolaterally the minipig hypothalamus can be divided into three cytoarchitectonic distinct longitudinal zones. The periventricular longitudinal zone comprises the supraoptic, paraventricular, median preoptic, anteroventral periventricular, suprachiasmatic and arcuate nuclei.The medial longitudinal zone includes the prominent medial preoptic, ventromedial, dorsomedial and medial mammillary nuclei. Together with the anterior hypothalamic area, they can be further divided into distinct subregions. The dorsal and posterior hypothalamic areas and the retromammillary and lateral mammillary nuclei are cyto- and chemoarchitectonically distinct but cannot be further divided into subregions.The cell sparse, fiber rich lateral longitudinal zone comprises the lateral preoptic and lateral hypothalamic area as well as the perifornical, lateral tuberal and tuberomammillary nuclei.The findings presented here indicate that the cyto- and chemoarchitecture of the Göttingen minipig hypothalamus is comparable to that of rat, landrace pig, monkey, and human and that the Göttingen minipig may be well suited for future, non-primate, large mammal, hypothalamic research.  相似文献   
169.
Differences in the global methylation pattern, ie hyper‐ as well as hypo‐methylation, are observed in cancers including germ cell tumours (GCTs). Related to their precursor cells, GCT methylation status differs according to histology. We investigated the methylation pattern of normal fetal, infantile, and adult germ cells (n = 103) and GCTs (n = 251) by immunohistochemical staining for 5‐ cytidine. The global methylation pattern of male germ cells changes from hypomethylation to hypermethylation, whereas female germ cells remain unmethylated at all stages. Undifferentiated GCTs (seminomas, intratubular germ cell neoplasia unclassified, and gonadoblastomas) are hypomethylated, whereas more differentiated GCTs (teratomas, yolk sac tumours, and choriocarcinomas) show a higher degree of methylation. Embryonal carcinomas show an intermediate pattern. Resistance to cisplatin was assessed in the seminomatous cell line TCam‐2 before and after demethylation using 5‐azacytidine. Exposure to 5‐azacytidine resulted in decreased resistance to cisplatin. Furthermore, after demethylation, the stem cell markers NANOG and POU5F1 (OCT3/4), as well as the germ cell‐specific marker VASA, showed increased expression. Following treatment with 5‐azacytidine, TCam‐2 cells were analysed using a high‐throughput methylation screen for changes in the methylation sites of 14 000 genes. Among the genes revealing changes, interesting targets were identified: ie demethylation of KLF11, a putative tumour suppressor gene, and hypermethylation of CFLAR, a gene previously described in treatment resistance in GCTs. Copyright © 2010 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.  相似文献   
170.
The synthesis of novel linear‐hyperbranched (linhb) polyether block copolymers based on poly(ethylene oxide) and branched poly(glycerol), bearing a single pyrene or myristyl moiety at the α‐position of the linear chain is described. The polymers exhibit low polydispersity ( < 1.3) and controlled molecular weights ( = 5 000 g · mol?1). The mainly hydrophilic block copolymers with multiple hydroxyl end groups readily dissolve multiwalled carbon nanotubes (MWCNTs) in water by mixing and subsequent sonification, resulting in noncovalent attachment of the linhb hybrid structure to the carbon nanotubes (CNTs). Transmission electron microscopy (TEM) was employed to visualize the solubilized nanotubes; after sulfation of the multiple hydroxyl groups the polymer layer was detected in the TEM images.

  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