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   2285篇
  免费   102篇
  国内免费   27篇
耳鼻咽喉   4篇
儿科学   73篇
妇产科学   28篇
基础医学   280篇
口腔科学   26篇
临床医学   130篇
内科学   486篇
皮肤病学   23篇
神经病学   269篇
特种医学   110篇
外科学   390篇
综合类   7篇
预防医学   67篇
眼科学   191篇
药学   64篇
中国医学   5篇
肿瘤学   261篇
  2023年   30篇
  2022年   33篇
  2021年   62篇
  2020年   37篇
  2019年   48篇
  2018年   51篇
  2017年   40篇
  2016年   57篇
  2015年   55篇
  2014年   64篇
  2013年   79篇
  2012年   135篇
  2011年   135篇
  2010年   81篇
  2009年   64篇
  2008年   132篇
  2007年   107篇
  2006年   128篇
  2005年   142篇
  2004年   134篇
  2003年   115篇
  2002年   123篇
  2001年   36篇
  2000年   33篇
  1999年   53篇
  1998年   30篇
  1997年   36篇
  1996年   23篇
  1995年   15篇
  1994年   37篇
  1993年   23篇
  1992年   21篇
  1991年   27篇
  1990年   25篇
  1989年   26篇
  1988年   24篇
  1987年   19篇
  1986年   8篇
  1985年   19篇
  1984年   13篇
  1983年   14篇
  1981年   7篇
  1980年   9篇
  1979年   6篇
  1976年   5篇
  1975年   6篇
  1974年   5篇
  1973年   6篇
  1972年   5篇
  1970年   6篇
排序方式: 共有2414条查询结果,搜索用时 15 毫秒
971.
972.
BACKGROUND AND OBJECTIVES: To determine the prognostic factors for long-term survivors (LTS) with stage IV non-small cell lung cancer (NSCLC) who had undergone various treatments. PATIENTS AND METHODS: From 1990 to 1999, 222 NSCLC patients with stage IV disease, who had been treated in our department, were reviewed. As the initial treatment, 135 patients (48%) were treated with chemotherapy alone, 52 patients with a combination of chemotherapy and radiotherapy, 19 patients underwent an operation with or without any other therapeutic modalities and 16 were received radiotherapy alone. RESULTS: Seventeen (7.7%) patients survived for more than 2 years, and all but one had adenocarcinoma. Among these LTS, eight patients received surgery as the initial therapy, and 16 (94.1%) received some type of local-control therapy, including surgery or radiotherapy, during the course of their disease. Regarding the clinical characteristics between LTS and others (non-LTS), an early N status, a single metastatic site, a good performance status, and surgery for initial therapy were all found to be significantly important factors for LTS. A multivariate analysis using a logistic regression model also showed an early N status and surgical treatment to be significantly associated with LTS. CONCLUSIONS: Selected patients with an early N status may be appropriate candidates for aggressive multimodality treatment including surgery, in order to provide a long-term survival for stage IV NSCLC.  相似文献   
973.
Previously, we observed that liquid form bovine bone (BB) gelatin stimulates murine spleen cells to proliferate in vitro. In this study, activity of BB gelatin to stimulate murine-adherent peritoneal exudate cells (PEC) to secrete cytokines has been examined. Quantitatively, BB gelatin stimulated adherent PEC of C3H/HeN mice to secrete interleukin (IL)-12 (+p40), TNF-alpha, and IL-6 but not IL-1beta, IL-2, IL-10, and IFN-gamma. Qualitatively, BB gelatin-induced secretion of KC, MIP-2, MCP-1, RANTES, and MIP-1a as well as IL-6 but not 6Ckine, CTACK, Eotaxin, G-CSF, GM-CSF, IL-2,-3,-4,-5,-9,-10,-12,-13,-17, Leptin, IFN-gamma, SCF, sTNFri, TARC, TNF-alpha, TIMP-1, Tpo, and VEGF. BB gelatin acted on adherent PEC of C3H/HeN mice but not C3H/HeJ mice, which lack Toll-like receptor 4. Polymyxin B, a LPS antagonist, did not inhibit the activity of BB gelatin. Lipopolysaccharide (LPS) but not BB gelatin induced secretion of an appreciable amount of mIL-1beta. These results suggest that the activity of BB gelatin is not attributed to contamination of LPS but BB gelatin itself. It was also suggested that BB gelatin stimulated adherent PEC to newly produce and secrete cytokines.  相似文献   
974.

Background

Ligamentum flavum (LF) hypertrophy is an important cause of lumbar spinal canal stenosis (LSS), one of the most common spinal disorders in the elderly. Although many cytokines are reported to be associated with LF hypertrophy, the intracellular signaling system is rarely discussed. The purpose of this study was to identify the JAK/STAT signaling pathway and to examine the role of the JAK/STAT systems in the hypertrophied LF.

Methods

The LF of 10 LSS patients was analyzed and the expression of JAK1, STAT3, phosphorylated (p)-STAT3, and actin was examined by Western blot analysis. The expression of p-STAT3 was also examined by immunostaining and its positive cell ratio was compared between LSS and non-LSS samples. We measured the thickness of the LF on magnetic resonance images and studied the relationship between its thickness and the expression of p-STAT3.

Results

JAK1, STAT3, and p-STAT3 were detected in almost all samples by Western blot analysis. Immunoreactivity against p-STAT3 was observed mainly in endothelial- and fibroblast-like cells. The expression of p-STAT3 was significantly higher in LSS than non-LSS samples; it was significantly stronger on the dorsal than the dural side of the LF and positively correlated with the thickness of the LF on the dorsal side.

Conclusions

The JAK/STAT signaling pathway is positively correlated with the thickness of the LF. Our findings suggest that JAK1 and STAT3 molecules are involved in and regulate LF hypertrophy.  相似文献   
975.
Cdc7, a protein kinase required for the initiation of eukaryotic DNA replication, is activated by a regulatory subunit, Dbf4. A second activator of Cdc7 called Drf1 exists in vertebrates, but its function is unknown. Here, we report that in Xenopus egg extracts, Cdc7-Drf1 is far more abundant than Cdc7-Dbf4, and removal of Drf1 but not Dbf4 severely inhibits phosphorylation of Mcm4 and DNA replication. After gastrulation, when the cell cycle acquires somatic characteristics, Drf1 levels decline sharply and Cdc7-Dbf4 becomes the more abundant kinase. These results identify Drf1 as a developmentally regulated, essential activator of Cdc7 in Xenopus.  相似文献   
976.
The mechanical properties of regenerated cartilage tissue were measured to evaluate changes in their visco-elastic properties during cultivation. An indentation test and dynamic visco-elasticity measurements were carried out on cartilage tissue cultured with rabbit chondrocytes that had been inoculated into the fibroin sponge. A 1.5-mm-diameter porous indentor was used for the indentation test, in which time-dependent strain curves were derived from measurements taken under several loading conditions. Dynamic visco-elasticity measurements were performed under compressive loading to evaluate the load-bearing function of the articular cartilage. Although the amount of permanent deformation was not influenced by the duration of cartilage regeneration, the amount of creep deformation increased with longer cultivation. The E' value of the regenerated cartilage increased and the peak value of tan delta and the frequency at the peak became lower with longer cultivation. It is suggested that the changes in the time-dependent strain curves and dynamic visco-elastic properties of the regenerated cartilage were caused by maturation of the cultured cartilage tissue.  相似文献   
977.
WSX-1 is a component of the IL-27R. Analyses of WSX-1 knockout (WSX-1(-/-)) mice have shown that IL-27/WSX-1 signaling is essential for the proper development of T(h)1 responses and that WSX-1 can suppress cellular activation and pro-inflammatory cytokine production. We have generated transgenic mouse lines over-expressing the WSX-1 gene under the control of the T cell-specific CD2 promoter (WSX-1 Tg mice). Unexpectedly, like activated CD4(+) T cells from WSX-1(-/-) mice, activated CD4(+) T cells from WSX-1 Tg mice showed increased proliferation, augmented IL-2 production and up-regulated surface expression of activation markers. IL-27-mediated tyrosine phosphorylation of STAT1 was also enhanced in WSX-1 Tg CD4(+) T cells, but STAT3 activation was normal. Exogenous IL-27 supported the proliferation of wild-type CD4(+) T cells but suppressed that of WSX-1 Tg cells. WSX-1 over-expression increased IFN-gamma production in T(h)1-polarized CD4(+) T cells, but also promoted T(h)2 cytokine production under T(h)1-polarizing conditions. Importantly, WSX-1 over-expression failed to suppress T(h)2 cytokine production under T(h)2-polarizing conditions. Cytokine hyperproduction was also observed in vivo in WSX-1 Tg mice injected with Con A. Our data suggest that WSX-1 plays a pivotal role in regulating T cell responsiveness to TCR stimulation and that the correct balance of STAT1/STAT3 activation downstream of IL-27R engagement is crucial for the physiological function of IL-27.  相似文献   
978.
979.
Two brothers with XX male syndrome with penoscrotal hypospadias are reported. Chromosomal analysis of cells from the peripheral blood, skin, and testes revealed a normal female karyotype in both subjects. Biopsy of both testes in the brothers showed histological features of normal immature testes and no evidence of ovarian structures. Neither vagina, uterus nor fallopian tubes could be detected either by exploratory laparotomy or retrograde urethrography. Results of endocrine studies on serum gonadotropins (LH and FSH) and testosterone levels as well as their responses to LH-RH and hCG stimulation tests were normal for age. Studies of various genetic markers, including the Xg blood type and erythrocyte enzymes, were performed in the probands and their parents. Possible explanations for the paradoxical occurrence of testes in XX males and for the familial occurrence are discussed.  相似文献   
980.
Association of the pink-eye-dilution gene (P) with hypopigmentation is seen in patients who have oculocutaneous albinism type 2 (OCA2) and Prader-Willi syndrome (PWS) or Angelman syndrome (AS). However, it remains unknown whether duplication or amplification of the P gene causes hyperpigmentation. We previously reported a woman who had hyperpigmentation with a duplication of the proximal part of 15q, including the P gene. Here, we describe an additional patient with mosaicism of inv dup(15) and clinical manifestations of severe psychmoter retardation, epilepsy, and pigmentary dysplasia showing mottled and linear patterns of hyperpigmentation. His karyotype was 47,XY,+idic(15)(pter-->q14::q14-->pter)[38]/46,XY[12] de novo. Chromosomal fluorescence in situ hybridization (FISH) showed six copies of the P gene. Therefore, his cutaneous mosaicism might be caused by the presence of both normal and hyperpigmented skin due to multicopies of the P gene.  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