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   17543篇
  免费   719篇
  国内免费   79篇
耳鼻咽喉   205篇
儿科学   292篇
妇产科学   187篇
基础医学   2135篇
口腔科学   551篇
临床医学   1104篇
内科学   4079篇
皮肤病学   218篇
神经病学   1432篇
特种医学   737篇
外科学   3127篇
综合类   68篇
预防医学   568篇
眼科学   225篇
药学   1203篇
中国医学   25篇
肿瘤学   2185篇
  2023年   88篇
  2022年   174篇
  2021年   268篇
  2020年   156篇
  2019年   184篇
  2018年   282篇
  2017年   192篇
  2016年   252篇
  2015年   262篇
  2014年   378篇
  2013年   440篇
  2012年   737篇
  2011年   735篇
  2010年   482篇
  2009年   413篇
  2008年   714篇
  2007年   703篇
  2006年   743篇
  2005年   772篇
  2004年   743篇
  2003年   733篇
  2002年   769篇
  2001年   775篇
  2000年   775篇
  1999年   705篇
  1998年   247篇
  1997年   189篇
  1996年   187篇
  1995年   133篇
  1994年   108篇
  1993年   106篇
  1992年   464篇
  1991年   408篇
  1990年   372篇
  1989年   457篇
  1988年   375篇
  1987年   332篇
  1986年   357篇
  1985年   337篇
  1984年   248篇
  1983年   157篇
  1982年   73篇
  1979年   144篇
  1978年   100篇
  1977年   86篇
  1975年   80篇
  1974年   75篇
  1973年   75篇
  1969年   92篇
  1967年   87篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
91.
Chromosome banding analyses were made on 10 cases of Ph1-positive AML (7 M1 and 3 M2). The standard type Ph1 translocation, t(9q +;22q -), was identified in all of them. Karyotypically normal cells were observed in 6-65% of bone marrow metaphases at the initial cytogenetic examination of 7 patients, whereas the remaining 3 patients had only Ph1-positive cells at diagnosis. Follow-up studies performed in 5 cases indicated that the frequency of karyotypically normal cells increased up to 81-100% when the patients were in remission, whereas it was much reduced in relapse. In 5 cases, there was observed a clone of cells in which the Ph1 translocation was the sole karyotypic abnormality. Various types of other chromosome abnormalities, in addition to the Ph1, were observed in all cases, among which-7 was the most frequent, being found in three cases as a stem line. Other additional changes encountered were + Ph1, del(5), i(17q), - 10, + 18, + X, and various numerical and structural changes including certain secondary translocations that occurred in the Ph1 (22q -) or its partner (9q +). The types and frequencies of these additional changes appeared to be different from those found in the acute phase of CML or in Ph1-positive ALL.  相似文献   
92.
93.
Summary Thalamic projections of the pallidum and the deep cerebellar nuclei were studied by unitary recordings as well as field potential analysis in the thalamus of squirrel monkeys (Saimiri sciureus) under sodium pentobarbital anesthesia.Stimulation of the pallidum produced a positive field potential preceded by incoming afferent fiber volleys in the thalamus. Spontaneous discharges of thalamic neurons were suppressed during this positive potential, and intracellular recordings from the thalamic neurons revealed that the time course of this field potential corresponded to that of the hyperpolarizing potential. The hyperpolarization was presumed to be a monosynaptic inhibitory postsynaptic potential by the short synaptic delay (about 0.5–0.7 ms) and responsiveness to high frequency stimulation (over 150 Hz). The positive field potential on stimulation of the external pallidal segment was distributed in L.po (VA) and the reticular thalamic nucleus around L.po, whereas that on stimulation of the internal segment was in V.o.a (the anterior basal part of VL) and in Z.o (upper part of VL). The projection of the external segment appeared to be less dense than that of the internal segment.The projection of deep cerebellar nuclei was situated in V.o.a, V.o.p (posterior part of basal part of VL), V.o.i (VLm), the intralaminar nucleus (CL), and some part of V. im (the rostral part of VPLo). Projections of the interpositus and dentate nuclei were distributed in a more anterior part than those of the fastigial nucleus. A certain topographical arrangement of the projections of these three nuclei was found in V.o.p, V.o.i and V.im. No significant overlap was detected between projections of the pallidum and the deep cerebellar nuclei within the thalamus.  相似文献   
94.
We report here that loss of the Sprouty2 gene (also known as Spry2) in mice resulted in enteric nerve hyperplasia, which led to esophageal achalasia and intestinal pseudo-obstruction. Glial cell line-derived neurotrophic factor (GDNF) induced hyperactivation of ERK and Akt in enteric nerve cells. Anti-GDNF antibody administration corrected nerve hyperplasia in Sprouty2-deficient mice. We show Sprouty2 to be a negative regulator of GDNF for the neonatal development or survival of enteric nerve cells.  相似文献   
95.
Human parvovirus B19 (B19) infects cells of erythroid lineage. Production of neutralizing antibodies (Abs) is indispensable for recovery from B19-related disease state. In this study, we used a convenient method to measure neutralizing activities in human sera by using a real-time quantitative PCR based assay. Erythroid cell line KU812Ep6 was incubated with test sera before infection with B19 virus. The copy number of B19-DNA in cultures was decreased in the presence of the sera from patients who recovered from acute B19 infection, whereas no decrease in B19-DNA was in cultures incubated with sera from healthy volunteers who had no B19 infection. The decrease in B19-DNA copy number was calculated and the inhibition percentage was expressed as neutralizing activity to B19. A clinical study showed that the levels of neutralizing ability were high in patients who recovered soon after acute B19 infection, but were low in some patients with a prolonged clinical course for recovery from B19 infection. This method is simple and convenient compared with methods described previously, showing its usefulness to evaluate the neutralizing activity to B19.  相似文献   
96.
The diagnosis of rheumatic diseases is primarily based on clinical symptoms and laboratory findings. However, diagnosis of rheumatic disease is often difficult because of the variations even in the same disease. Routine laboratory tests are valuable in detecting renal dysfunctions. In this review, the important auto-antibodies and inflammatory markers associated with rheumatic diseases are described. Further, their utility as diagnostic and prognostic tools, including their specificity, sensitivity and practical applications, is discussed.  相似文献   
97.
Recent data demonstrated that CD4+CD25+ regulatory T (Treg) cells and an enzyme called indoleamine 2,3-dioxygenase (IDO) mediate maternal tolerance to the fetus. Interestingly, Treg cells express the CTLA-4 molecule on their surface, and B7 (CD80/86) ligation by CTLA-4 enhanced IDO activity of dendritic cells (DCs) and monocytes by the induction of interferon gamma (IFN-gamma) production. In this study, we studied the IDO expression on peripheral blood monocytes and decidual monocytes or DCs after treatment with CTLA-4/Fc fusion protein or IFN-gamma using flow cytometry. IDO expressions on both peripheral blood DC and decidual DC and monocytes were up-regulated during normal pregnancy. On the other hand, both IDO expression on DC and monocytes after IFN-gamma treatment or CTLA-4 treatment were decreased in spontaneous abortion cases. The expression of CD86 on peripheral blood and decidual monocytes and DC in spontaneous abortion cases was lower compared with those in normal pregnancy subjects. Also, IFN-gamma production by decidual and peripheral blood mononuclear cells after CTLA-4/Fc treatment in spontaneous abortion cases was significantly lower than those in normal pregnancy subjects. These data suggest that CTLA-4 on Treg cells up-regulates IDO expression on decidual and peripheral blood DC and monocytes by the induction of IFN-gamma production.  相似文献   
98.
Sarcoma of the oral region is extremely rare and ultrastructural studies of the tumor are limited in number. We collected oral sarcomas, such as fibrosarcoma, malignant fibrous histiocytoma, liposarcoma, leiomyosarcoma, rhabdomyosarcoma, angiosarcoma, alveolar soft-part sarcoma, solitary plasmacytoma, and osteosarcoma, and performed ultrastructural studies of these tumors. The value of these studies for an understanding of the biological behavior of the tumors was then investigated. In these studies, electron microscopic examinations of oral sarcoma were of assistance in our attempt to establish correct diagnosis and histogenesis. Data from the studies of oral sarcoma by light microscopy, electron microscopy, and immunohistochemistry should be accumulated.  相似文献   
99.
100.
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