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   14491篇
  免费   832篇
  国内免费   189篇
耳鼻咽喉   286篇
儿科学   285篇
妇产科学   338篇
基础医学   2097篇
口腔科学   411篇
临床医学   1210篇
内科学   2908篇
皮肤病学   276篇
神经病学   1086篇
特种医学   895篇
外科学   1893篇
综合类   213篇
一般理论   1篇
预防医学   780篇
眼科学   435篇
药学   1268篇
中国医学   169篇
肿瘤学   961篇
  2023年   98篇
  2022年   247篇
  2021年   476篇
  2020年   205篇
  2019年   331篇
  2018年   439篇
  2017年   307篇
  2016年   399篇
  2015年   584篇
  2014年   656篇
  2013年   869篇
  2012年   1279篇
  2011年   1206篇
  2010年   687篇
  2009年   586篇
  2008年   806篇
  2007年   766篇
  2006年   729篇
  2005年   644篇
  2004年   560篇
  2003年   468篇
  2002年   417篇
  2001年   392篇
  2000年   331篇
  1999年   258篇
  1998年   142篇
  1997年   112篇
  1996年   94篇
  1995年   103篇
  1994年   75篇
  1993年   81篇
  1992年   128篇
  1991年   106篇
  1990年   104篇
  1989年   134篇
  1988年   106篇
  1987年   93篇
  1986年   68篇
  1985年   70篇
  1984年   41篇
  1983年   35篇
  1982年   35篇
  1981年   28篇
  1980年   32篇
  1979年   24篇
  1978年   21篇
  1977年   27篇
  1976年   21篇
  1975年   21篇
  1974年   17篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
BACKGROUND: The introduction of GnRH antagonists such as cetrorelix acetate has made possible the simplification of ovarian stimulation. However, the most effective protocol for their administration has not yet been clearly defined. METHODS: Forty women with male-factor infertility undergoing 40 ICSI cycles were included in the study. Clomiphene citrate at 100 mg a day was given from cycle day 3 through day 7. hMG at 150 IU was given on cycle days 4, 6 and 8, and was adjusted from day 9 according to the follicular and hormone responses. Cetrorelix acetate at 2.5 mg was administered when the leading follicle reached 14 mm. The remaining 0.5 mg was divided into two 0.25 mg injections for possible later use. Serum FSH, LH, estradiol and progesterone levels were measured daily from the day of cetrorelix acetate injection until hCG was given. RESULTS: Serum LH level was suppressed effectively for 4 days. Four patients (10%) needed one or two additional injections of 0.25 mg cetrorelix acetate. No premature LH surge was detected in any of the women treated. Sixteen women became pregnant (40%), of which 14 pregnancies (35%) were ongoing at the time of writing. CONCLUSIONS: This study demonstrates that this new protocol is feasible for couples with male-factor infertility undergoing ICSI.  相似文献   
32.
Immunotherapy using adoptive cell transfer is a promising approach that can result in the regression of bulky, invasive cancer in some patients. However, currently available therapies remain less successful than desired. To study the mechanisms of action and possible improvements in cell-transfer therapies, we use a murine model system with analogous components to the treatment of patients. T cell receptor transgenic CD8+ T cells (pmel-1) specifically recognizing the melanocyte differentiation antigen gp100 are adoptively transferred into lympho-depleted mice bearing large, established, 14-day subcutaneous B16 melanoma (0.5-1 cm in diameter) on the day of treatment. Adoptive cell transfer in combination with interleukin interleukin-2 or interleukin-15 cytokine administration and vaccination using an altered form of the target antigen, gp100, can result in the complete and durable regression of large tumor burdens. Complete responders frequently develop autoimmunity with vitiligo at the former tumor site that often spreads to involve the whole coat. These findings have important implications for the design of immunotherapy trials in humans.  相似文献   
33.
Several studies have suggested that the regulator of G-protein signaling 4 (RGS4) may be a positional and functional candidate gene for schizophrenia. Three single nucleotide polymorphisms (SNP) located at the promoter region (SNP4 and SNP7) and the intron 1 (SNP18) of RGS4 have been verified in different ethnic groups. Positive results have been reported in these SNPs with different numbers of SNP combinatory haplotypes. In this study, these three SNP markers were genotyped in 218 schizophrenia pedigrees of Taiwan (864 individuals) for association analysis. Among these three SNPs, neither SNP4, SNP7, SNP18 has shown significant association with schizophrenia in single locus association analysis, nor any compositions of the three SNP haplotypes has shown significantly associations with the DSM-IV diagnosed schizophrenia. Our results fail to support the RGS4 as a candidate gene for schizophrenia when evaluated from these three SNP markers.  相似文献   
34.
Antiphospholipid syndrome (APS) is an autoimmune disease that is characterized by thrombosis, recurrent fetal loss and thrombocytopenia. Antiphospholipid antibodies, detected by enzyme-linked immunoabsorbent assays (aCL) and/or in vitro blood clotting assays (LAC) are strongly associated with APS. Both the molecular structures used by pathogenic antiphospholipid antibodies and the genetic mechanisms leading to their production are unknown. We describe here the variable region genes of seven IgG antiphospholipid antibodies derived from two APS patients. Of these, five are pathogenic as defined in a mouse model of thrombosis and two are not. Analyses of the expressed variable region genes show no preferential V gene usage. However, similar to anti-DNA antibodies, pathogenic antiphospholipid antibodies contain an increased number of arginine residues in the third complimentarity-determining region (CDR3) of their H chains. The increased accumulation of arginine residues in the V(H) CDR3 may act to enhance antigen binding, promote disease and point to the importance of the H chain in the pathogenic potential of certain antiphospholipid antibodies.  相似文献   
35.
The present study was performed to determine whether the effects induced by GABA(B) receptor-acting drugs would be related with the alteration in GABA(B) receptor expression in the hippocampus using Mongolian gerbil, a genetic epilepsy model. The distribution patterns of both GABA(B) receptor 1A/B and GABA(B)receptor 2 immunoreactivities were similarly detected in the hippocampi of normal and seizure-prone gerbils. Following baclofen (GABA(B) receptor agonist) or phaclofen (GABA(B) receptor antagonist) treatment, GABA(B) receptor immunoreactivities were decreased or increased by dose-dependent manners, respectively. Vigabatrin (GABA transaminase inhibitor) or 3-mercaptopropionic acid (GAD inhibitor) treatment did not affect GABA(B) receptor expressions. These findings suggest that GABA(B) receptor expression in the gerbil hippocampus may be altered by baclofen or phaclofen treatment.  相似文献   
36.
Compound nerve action potential (CNAP) of the mixed peripheral nerve is composed of A alpha beta, A delta, and C potentials. All components of CNAPs in the sciatic nerve were recorded by stimulating the tibial nerve of both control and lead-poisoned rats. Marked decrease of nerve conduction velocity and prolonged duration were found in A alpha beta and A delta fibers especially in large myelinated A alpha beta fibers. The amplitude decreased in A alpha beta potential, but the area did not change. In C potential produced by activation of unmyelinated fibers, nerve conduction velocity slightly decreased, but the amplitude and area did not significantly change. Pathologic correlates revealed prominent segmental demyelination with significant decrease of large myelinated fiber densities. Minimal axonal degeneration of unmyelinated fibers was present. We can conclude that electrophysiologic changes in the lead-poisoned rats correlate with pathologic changes in them.  相似文献   
37.
To determine the content of thyroglobulin in oxyphilic cells of the thyroid, which have been considered as non-thyroglobulin producing cells, the degree of stainability of the various oxyphilic cells for thyroglobulin was compared with that of non-oxyphilic follicular cells in either same or different lesion. A total of 13 oxyphilic lesions, including three follicular adenomas containing oxyphilic cell nodules, four pure oxyphilic cell adenomas, and six Hashimoto's thyroiditis were compared with 16 of non-oxyphilic lesions such as, seven follicular adenomas, four chronic lymphocytic thyroiditis, and five Graves' disease. Many oxyphilic cells stained positively for thyroglobulin regardless of their morphologic variation, but less intensely than the usual follicular cells in follicular adenomas, chronic lymphocytic thyroiditis, and Graves' disease. The stainability of oxyphilic cells for thyroglogulin did not show any significant correlation with morphologic features, whereas in follicular adenomas, the non-oxyphilic follicular cells forming microfollicles stained less strongly for thyroglobulin than the same cells lining large mature follicles in a reproducible way. With above findings, we concluded that oxyphilic cells maintain the functional activity in terms of thyroglobulin synthesis, although the content of the thyroglobulin is less than that of non-oxyphilic colloid forming follicular cells.  相似文献   
38.
Endogenous heparin-binding lectin purified from postmortem lung samples of two cystic fibrosis (CF) patients was compared to lectin derived from normal tissue with respect to structure, carbohydrate specificity, interaction with alginate derived from CF isolates of Pseudomonas aeruginosa, and secretion within the lung. Lectin was purified from extracts of lung tissue by gel filtration on Sepharose CL-2B followed by affinity chromatography on heparin-Sepharose. Lectin purified from either CF lung or control tissue ran as two peptides of approximately 16,000 and 13,000 molecular weight on electrophoresis in sodium dodecyl sulfate. The lectins displayed similar carbohydrate specificity and interacted in much the same way with bacterial alginate. An increase in lectin secretion was seen in CF lungs affecting the bronchial epithelial cells and the mucosal glands. The data suggest that the major changes seen in endogenous heparin-binding lectin in CF are related to the quantity and distribution of lectin secretion.  相似文献   
39.
Skin thickness of Korean adults   总被引:4,自引:0,他引:4  
Skin thickness varies considerably between different races and age-groups, between men and women, and between different regions of the body surface. A few authors reported the skin thickness of different regions of the body, but no detailed study have been performed on Asian. We performed 452 biopsies on 28 different regions of the normal skin of Korean men and women. The specimens were stained with hematoxylin-eosin and measured microscopically. The thickness of the skin (epidermis plus dermis) ranged from 521 to 1977 microm; the eyelid, prepuce, and inguinal skin was thinnest (521-626 microm), and the back was thickest (1977 microm). The thickness of the epidermis varied from 31 to 637 microm; skin thickness in the prepuce, eyelid, supraclavicular region, postauricular region, and axilla ranged from 31 to 71 microm; the buttock, dorsum of the hand, and dorsum of the foot were relatively thick (138-189 microm); the palm and sole were thickest (601-637 microm). The thickness dermis varied from 469 to 1942 microm; skin thickness in the eyelid, prepuce, inguinal region, and postauricular region ranged from 469 to 645 microm; the buttock, chest, and anterior neck were relatively thick (1318-1586 microm); the back was thickest (1942 microm). The epidermis accounted for 3.7-16.8% of the entire skin in most regions, except in the palm and sole (40.6-44.6%). Thickness data may be useful in harvesting full- or split-thickness skin grafts.  相似文献   
40.
To understand whether the p53-regulated mdm2 gene expression was altered by the Epstein-Barr virus (EBV) in nasopharyngeal carcinoma (NPC), the NPC-TW01 cell line was infected by EBV through IgA receptor-mediated endocytosis. The mdm2 gene was expressed only in a small fraction of the NPC cell population and could be enhanced in the EBV-infected (EBV+) cells. In the animals bearing EBV+ and EBV- NPC xenografts, the MDM2+ cells only appeared in clusters in both EBV+ and EBV- tumors with stronger expression in EBV+ cells. Cotransfection of pmdm2-Luc plus pSV40-p53 plus pCMV-LMP1 in the NPC-TW06 line that had p53 heterozygous point mutation showed stronger mdm2 promoter activity than cells cotransfected with pmdm2-Luc plus pSV40-p53, but no mdm2 promoter activity was seen in cells cotransfected with pmdm2-Luc plus pCMV-LMP1. Only the EBV-LMP1 but not the EBV-LMP2A gene could enhance p53 to upregulated mdm2 expression. Tumor cells in NPC biopsy specimens revealed similar mdm2 expression as in the animal model. It is concluded that although EBV can indirectly enhance mdm2 gene expression in tumor cells that express this gene, it cannot turn on or directly regulate mdm2 expression in cells that do not express this gene. In other words, EBV plays a role as an enhancer in NPC tumorigenesis.  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