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   21685篇
  免费   2192篇
  国内免费   45篇
耳鼻咽喉   182篇
儿科学   563篇
妇产科学   527篇
基础医学   3409篇
口腔科学   337篇
临床医学   3008篇
内科学   4288篇
皮肤病学   257篇
神经病学   1697篇
特种医学   863篇
外科学   2378篇
综合类   423篇
一般理论   17篇
预防医学   2774篇
眼科学   317篇
药学   1524篇
中国医学   12篇
肿瘤学   1346篇
  2023年   150篇
  2022年   141篇
  2021年   390篇
  2020年   263篇
  2019年   416篇
  2018年   466篇
  2017年   376篇
  2016年   371篇
  2015年   450篇
  2014年   616篇
  2013年   865篇
  2012年   1300篇
  2011年   1330篇
  2010年   737篇
  2009年   631篇
  2008年   1114篇
  2007年   1192篇
  2006年   1167篇
  2005年   1142篇
  2004年   1019篇
  2003年   1033篇
  2002年   946篇
  2001年   479篇
  2000年   463篇
  1999年   479篇
  1998年   277篇
  1997年   221篇
  1996年   216篇
  1995年   231篇
  1994年   208篇
  1993年   220篇
  1992年   367篇
  1991年   374篇
  1990年   302篇
  1989年   315篇
  1988年   273篇
  1987年   288篇
  1986年   283篇
  1985年   305篇
  1984年   264篇
  1983年   207篇
  1982年   153篇
  1981年   144篇
  1980年   121篇
  1979年   168篇
  1978年   138篇
  1977年   107篇
  1976年   109篇
  1974年   116篇
  1973年   118篇
排序方式: 共有10000条查询结果,搜索用时 707 毫秒
91.
Endothelial cell activation may play a role in thrombotic complications of BMT such as hepatic veno-occlusive disease (VOD), right atrial line thrombosis and microangiopathic haemolysis. To assess this, von Willebrand factor antigen (vWF:ag) was measured in 72 patients (25 allografts, 46 autografts and one syngeneic) during the first 6 weeks post-transplant. There was a significant rise in vWF:ag in both allografts and autografts but a greater increase was seen in the allografts. The changes in vWF:ag did not correlate with changes in C reactive protein showing that this was not merely an acute phase response. vWF multimers were normal in a subgroup of uncomplicated transplants showing that there was no large scale endothelial cell disruption. Patients with VOD did not have changes in vWF:ag that were consistently different from uncomplicated controls. Three of four patients who developed line thrombosis had higher levels of vWF:ag compared with control groups; multimeric structure of the vWF was again normal. These results show that there is endothelial cell activation post-BMT and that this is greater in allografts compared with autografts, thus suggesting a possible mechanism for the higher incidence of VOD in this group. There were no useful predictive markers of VOD or thrombosis in individual patients.  相似文献   
92.
93.
94.
A cytoskeletal actin gene in the mosquito Anopheles gambiae   总被引:2,自引:0,他引:2  
Five actin genes have been identified in the mosquito Anopheles gambiae , and a constitutively expressed actin gene has been chosen for detailed analysis. We have physically mapped and sequenced this gene and six associated cDNAs, including translated coding regions, as well as the 5 and 3 flanking sequences. Analysis of stage-specific RNA shows this gene to be present in all stages of mosquito development and in an established A. gambiae cell line, thus indicating a cytoskeietal actin. In the sequence of the translated coding region and in pattern of expression, this gene is very similar to the cytoskeietal actin genes of Droso-phila melanogaster , and in sequence, equally similar to the Artemia cytoskeietal actin gene 403 (99.2% identity among the three amino acid sequences). Sequencing of this A. gambiae actin gene (designated actWior its location in chromosome division 1D) and selected cDNAs shows that it possesses three alternative leader sequences; thus the gene appears to have three alternative promoters. These promoters should ultimately prove useful in the production of transgenic constructs for constitutive expression.  相似文献   
95.
There is sometimes a discrepancy between the apparent thickness of postmenopausal endometria, as determined by transvaginal ultrasonography, and the examination of endometrial biopsies. We describe a case which showed that tamoxifen (20 mg/day over 12 months) decreased impedance to blood flow in the uterine arteries and increased the apparent thickness of the endometrium. Conversely, the analysis of biopsies suggested the presence of an atrophic endometrium. The introduction of sterile saline into the uterine cavity during a repeat ultrasound scan revealed the presence of a large, free-floating endometrial polyp, which was subsequently difficult to see by hysteroscopy.  相似文献   
96.
Hope  Sally 《Family practice》2003,20(3):355
If I had not been asked to read this book, I would not havepicked it off the shelf, despite my interest in women’shealth. The two reasons for this were the cover and the title.I’m ashamed to admit that ‘A Life  相似文献   
97.
98.
99.
100.
Human interleukin 3 (IL-3) is a multipotential cytokine that supports the growth of early hematopoietic progenitors and promotes their response to other, later-acting cytokines. We found that IL-3 was able to induce the expression of interleukin 2 (IL-2) receptor (IL-2R) (CD25) on a subset of early myeloid cells in normal human bone marrow that had been first depleted of mature hematopoietic cells and E-rosette-positive T cells by treatment with soybean lectin and sheep erythrocytes (SBA-E-BM). Immunofluorescence analysis revealed that the CD25+ cells were contained almost entirely within the lymphoblastoid gate of the IL-3-cultured marrow. CD25 was undetectable on freshly isolated marrow and less than 10% CD25+ cells could be detected following liquid culture at 37 degrees C in the presence of 10% human serum, 10% fetal calf serum, or under serum-free conditions. Addition of IL-3 (100 U/ml) significantly increased the expression of CD25 to 37%, 31%, and 24%, respectively. CD25 could also be induced by granulocyte-macrophage colony-stimulating factor (GM-CSF), but no IL-2R was detectable following exposure to granulocyte colony-stimulating factor (G-CSF), macrophage colony-stimulating factor (M-CSF), interleukin 1 (IL-1), interleukin 4 (IL-4), or IL-2. Expression of CD25 was dependent on the dose of IL-3 or GM-CSF added and was maximal within 24 h of exposure. Two-color immunofluorescence analysis demonstrated that CD25 was not expressed by cells of lymphoid lineage or by mature monocytes, but rather was present on cells that coexpressed CD13, CD33, CD34, MY8, and HLA-DR, and that lacked CD14 or CD11b, thus placing the CD25+ cells at or near the myeloblast stage of differentiation. An identical phenotype was found for CD25+ cells induced by GM-CSF. Cycloheximide completely inhibited the IL-3-induced expression of CD25, indicating the necessity for protein synthesis, and although most of the CD25+ cells were in G0/G1 phase, 25% of the cells were in S or G2M phase, indicating that receptor expression was not cell-cycle dependent. The p75 chain of IL-2R was not detected on the CD25+ cells. IL-3 was also found to directly induce CD25 in greater than 46% of SBA-E-BM enriched for CD34+ cells by panning. Consistent with the expression of only p55 IL-2R, the functional activity of IL-2 on enriched CD34+ cells exposed to IL-3 could not be demonstrated in either granulocyte-macrophage colony-forming unit (CFU-GM) assays or proliferation assays.(ABSTRACT TRUNCATED AT 400 WORDS)  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