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   6417篇
  免费   304篇
  国内免费   29篇
耳鼻咽喉   36篇
儿科学   100篇
妇产科学   56篇
基础医学   772篇
口腔科学   114篇
临床医学   378篇
内科学   1474篇
皮肤病学   130篇
神经病学   681篇
特种医学   258篇
外科学   995篇
综合类   18篇
预防医学   299篇
眼科学   195篇
药学   522篇
中国医学   13篇
肿瘤学   709篇
  2023年   32篇
  2022年   87篇
  2021年   107篇
  2020年   63篇
  2019年   95篇
  2018年   148篇
  2017年   96篇
  2016年   146篇
  2015年   124篇
  2014年   179篇
  2013年   187篇
  2012年   326篇
  2011年   364篇
  2010年   206篇
  2009年   170篇
  2008年   303篇
  2007年   316篇
  2006年   285篇
  2005年   274篇
  2004年   279篇
  2003年   253篇
  2002年   290篇
  2001年   199篇
  2000年   218篇
  1999年   205篇
  1998年   98篇
  1997年   72篇
  1996年   66篇
  1995年   63篇
  1994年   50篇
  1993年   43篇
  1992年   150篇
  1991年   133篇
  1990年   106篇
  1989年   104篇
  1988年   105篇
  1987年   91篇
  1986年   86篇
  1985年   87篇
  1984年   54篇
  1983年   39篇
  1982年   33篇
  1981年   35篇
  1979年   46篇
  1978年   26篇
  1976年   25篇
  1974年   25篇
  1973年   27篇
  1971年   26篇
  1970年   34篇
排序方式: 共有6750条查询结果,搜索用时 11 毫秒
81.
82.
H Iwata  M Yamagawa  P Roy 《Virology》1992,191(1):251-261
The amino acid sequences of four major capsid proteins of African horse sickness virus (serotype 4, AHSV-4) have been compared with those of Bluetongue virus of sheep. Epizootic hemorrhagic disease virus of deer, and the phylogenetic relationships established. Complete nucleotide sequence analysis of three RNA segments (L2, L3, and M6) of AHSV-4 and their encoded products, VP2, VP3, and VP5, together with previously published data for VP7 (Roy et al., 1991), have revealed that of the four capsid proteins the innermost protein, VP3, is the most conserved, and the outermost protein, VP2, is the most variable. Some 57-58% of the aligned BTV-10 and EHDV-1 VP3 amino acids are identical with those of AHSV-4. This compares to an identity of 79% between the BTV and EHDV VP3 sequences. For the VP7 proteins 64% of the aligned amino acids are identical between BTV-10 and EHDV-1, while they share 44-46% amino acid residues with the aligned VP7 protein of AHSV-4. By contrast, the VP2 proteins of the three viruses share only 19-24% identical amino acids. Various other comparative analyses of the proteins indicate that the VP2 species of the three orbiviruses are similar. Unlike VP2, the other outer capsid protein, VP5 is more conserved among the three viruses. On alignment, the VP5 of AHSV-4 has some 43-45% identical amino acids with that of BTV-10 and EHDV-1. Between BTV and EHDV, 62% of the aligned sequences are identical.  相似文献   
83.
BACKGROUND: Although there have been numerous reports in personality of mood disorders, there have been few reports in regard with personality of winter seasonal affective disorder (SAD). Furthermore, no reports have been published concerning summer SAD personality characteristics. Thus, this study was conducted to assess the personality of winter and summer SAD using Tri-dimensional Personality Questionnaire (TPQ) that have been used in a variety of mental disorders. METHODS: A total of 6135 Japanese were evaluated with TPQ, the Seasonal Pattern Assessment Questionnaire (SPAQ) and the Self-rating Depression Scale (SDS). Winter, summer and non-SAD groups were classified by SPAQ. We compared the difference of personality trait among these three groups in consideration of gender, age and SDS score influence. RESULTS: Winter SAD demonstrated higher "Novelty Seeking" and "Harm Avoidance"; summer SAD showed higher "Harm Avoidance" than the non-SAD group. "Harm Avoidance" in both SAD groups was re-analyzed using SDS score as a covariate, and "Novelty Seeking" in winter SAD using age as a covariate. As a result, the significance of high "Novelty Seeking" and high "Harm Avoidance" in winter SAD was excluded. However, "Harm Avoidance" remained the significant difference between summer and non-SAD. LIMITATION: SAD was diagnosed only by SPAQ and not by interview. The state-dependency of "Harm Avoidance" was not confirmed in identical patients over lapse of time. CONCLUSION: Patients with winter SAD have high "Harm Avoidance" dependent on the depressive state that is in accordance with non-seasonal depression. Patients with summer SAD have high "Harm Avoidance" possibly independent from the depressive state.  相似文献   
84.
Elimination of CD25+ T cells, which constitute 5-10% of peripheral CD4+ T cells in normal naive mice, leads to spontaneous development of various autoimmune diseases. These immunoregulatory CD25+CD4+ T cells are naturally unresponsive (anergic) in vitro to TCR stimulation, and, upon stimulation, suppress proliferation of CD25-CD4+ T cells and CD8+ T cells. The antigen concentration required for stimulating CD25+CD4+ T cells to exert suppression is much lower than that required for stimulating CD25-CD4+ T cells to proliferate. The suppression, which results in reduced IL-2 production by CD25-CD4+ T cells, is dependent on cellular interactions on antigen-presenting cells (and not mediated by far-reaching or long-lasting humoral factors or apoptosis-inducing signals) and antigen non-specific in its effector phase. Addition of high doses of IL-2 or anti-CD28 antibody to the in vitro T cell stimulation culture not only breaks the anergic state of CD25+CD4+ T cells, but also abrogates their suppressive activity simultaneously. Importantly, the anergic/suppressive state of CD25+CD4+ T cells appeared to be their basal default condition, since removal of IL-2 or anti-CD28 antibody from the culture milieu allows them to revert to the original anergic/suppressive state. Furthermore, transfer of such anergy/suppression-broken T cells from normal mice produces various autoimmune diseases in syngeneic athymic nude mice. These results taken together indicate that one aspect of immunologic self-tolerance is maintained by this unique CD25+CD4+ naturally anergic/suppressive T cell population and its functional abnormality directly leads to the development of autoimmune disease.   相似文献   
85.
An autopsy case of a 58-year-old woman with massive cardiac Involvement of adult T cell leukemia/lymphoma (ATLL) is reported. She developed cardiac failure due to aortic and mitral regurgitation with cardiac infiltration of ATLL cells, and underwent replacement of both aortic and mitral valves. Studies of the cut-surfaces revealed diffuse thickening of the subendocardial wall of the left chamber with widespread whitish-brown tumor infiltrates. In the regions surrounding the replaced aortic and mitral valves there was also massive tumor cell infiltration. The tumor cells infiltrating the cardiac muscle wall were T cell in origin and exhibited Leu-3a (CD4)-positive immunoreaction. Ultrastructurally, tumor cells contained markedly indented nuclei and some were attached directly to the muscle cells. These findings suggest that this was an unusual form of ATLL with widespread involvement of the heart.  相似文献   
86.
87.
Membrane response to the various temperatures as one of the external factors was investigated in the lenses of the poikilothermal animal and the homothermal animal. The rainbow trout lens was used as the poikilothermal material and the rat lens as the homothermal material. The rainbow trout lens maintained in vitro its transparency without the changes of cation balance at 0 degrees C - 25 degrees C, while cold cataract developed in the rat lens under the same conditions. Na, K-ATPase activity was detected at 0 degrees C in rainbow trout lens but it was not detected in the rat lens. Lactic acid in the rainbow trout lens was produced for 30 successive days at 0 degrees C, while that in the rat lens was not produced. The cataract developed at 37 degrees C in rainbow trout lens, which we called "warm cataract." Warm cataract developed not only when the lens was incubated in vitro but also when rainbow trout was kept in fresh water at 37 degrees C. Significant differences were detected in components of membrane lipids in the rainbow trout lenses compared to bovine lenses as the mammalian lens. The cholesterol/phospholipid ratio in the trout lens membrane was lower than that in bovine lens. This suggests that a poikilothermal animal lens can maintain the membrane fluidity at low temperatures. These results might suggest that the membrane characteristics in the rainbow trout lens play a role to maintain its transparency at low temperatures.  相似文献   
88.
CT-guided stereotactic brachytherapy has been performed for the deep-seated malignant gliomas using the double-catheter after-loading method. The catheter system consists of two coaxial polyethylene tubes with closed tips. The outer catheter is 3.0 mm in outer diameter and 2.4 mm in inner diameter. The inner catheter is 2.0 mm in outside diameter and 1.4 mm in inside diameter, and contains the radioactive sources. Localization of the target volume is determined by the preoperative findings of computed tomography (CT), magnetic resonance imaging (MRI), and cerebral angiography. Dosimetry and dose planning are so finalized for the target volume as to be irradiated interstitially more than tumoricidal dose. After stereotactic biopsy of the deep-seated brain tumors, stereotactic implantation of the outer catheters is performed using Iseki Stereotactic System in the CT room. Burr holes had been previously opened in the operating room. The inner catheters containing nonradioactive sources (dummy sources) are inserted, and skull X-p is taken to confirm the position of the dummy sources, and to calculate the dosimetry by computer. The inner catheters are replaced with catheters containing radioactive sources (226Ra) in the irradiation room. 226Ra sources deliver at least 500 rads/day (approximately 20 rads/hr) to the target volume as interstitial irradiation. Two patients of malignant gliomas treated with this procedure were shown as representative cases. These patients underwent CT-guided stereotactic brachytherapy as "boost" combined with conventional external irradiation.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
89.
90.
Previously we reported the majority of lesions induced by bilereflux, in the absence of chemical carcinogens, in the rat remnantstomach to consist primarily of gastric type and secondarilyof intestinal type cells, and that they are reversible afterdiversion of bile reflux. The present study was designed toevaluate changes in proliferative activities in cells of eachtype under these conditions. The frequency of adenomatous hyperplasia(AH) induced in the gastric stump mucosa by duodenal contentreflux after Billroth II partial gastrectomy (BII) increaseduntil the 54th week of the experiment. Roux-en-Y (RY) surgicalprocedure which prevents duodenal reflux performed at the 24thor 36th week after BII led to a decrease in AH. Cell contentof the lesions was analyzed using routine H&E staining,immunohistochemical staining for pepsinogen isoenzyme 1 andhistochemical procedures for mucins (paradoxical concanavalinA, galactose oxidase Schiff and sialidase galactose oxidaseSchiff reactions) and proliferation in each compartment evaluatedby an immunohistochemical method using bromodeoxyuridine (BrdU)and a monoclonal antibody against BrdU. At the 54th week thenumber of BrdU-labeled cells per normal pyloric column was significantly(P < 0.05) increased to 10.63/pit after the BII operation,while it diminished to 5.23/pit after RY diversion, this beingthe same level as with the RY procedure alone. AH maintaineda high rate of BrdU incorporation at 12.7% after BII operation,which was also significantly reduced (P < 0.01) to 7.0% bythe RY surgery. The intestinal type cell showed highest (22.2%),the surface mucous type cell showed the next (16.5%) and thepyloric gland type cell showed lowest (5.2%) BrdU labeling indicesafter BII operation. All the cell types in AH showed similarproportional decreases in BrdU incorporation after RY diversion.Thus surgical intervention reverses the cell proliferation causedby bile reflux in the gastric stump.  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