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   3707991篇
  免费   310889篇
  国内免费   13764篇
耳鼻咽喉   50913篇
儿科学   118332篇
妇产科学   97232篇
基础医学   580671篇
口腔科学   102751篇
临床医学   331280篇
内科学   661121篇
皮肤病学   95191篇
神经病学   316899篇
特种医学   148541篇
外国民族医学   497篇
外科学   572182篇
综合类   113742篇
现状与发展   23篇
一般理论   2377篇
预防医学   309371篇
眼科学   85744篇
药学   259619篇
  22篇
中国医学   10125篇
肿瘤学   176011篇
  2021年   55066篇
  2020年   35076篇
  2019年   57993篇
  2018年   71420篇
  2017年   54457篇
  2016年   60255篇
  2015年   74236篇
  2014年   108507篇
  2013年   173593篇
  2012年   97159篇
  2011年   97550篇
  2010年   117717篇
  2009年   122056篇
  2008年   85320篇
  2007年   88623篇
  2006年   99575篇
  2005年   94688篇
  2004年   97302篇
  2003年   87760篇
  2002年   77625篇
  2001年   120831篇
  2000年   115130篇
  1999年   111690篇
  1998年   67008篇
  1997年   64576篇
  1996年   62570篇
  1995年   58187篇
  1994年   52342篇
  1993年   48883篇
  1992年   82933篇
  1991年   79397篇
  1990年   75940篇
  1989年   74613篇
  1988年   69441篇
  1987年   68137篇
  1986年   64928篇
  1985年   64806篇
  1984年   56581篇
  1983年   51282篇
  1982年   44753篇
  1981年   41911篇
  1980年   39511篇
  1979年   48961篇
  1978年   40957篇
  1977年   36775篇
  1976年   34076篇
  1975年   32841篇
  1974年   35535篇
  1973年   34194篇
  1972年   31687篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
992.
We have presented a rare case of primary involvement of the anterior mediastinum by osteogenic sarcoma in which CT was useful in demonstrating calcium within the mass, and in distinguishing the mass from surrounding bony structures. Although rare, extraosseous osteogenic sarcoma should be included in the differential diagnosis of a calcified anterior mediastinal mass.  相似文献   
993.
994.
The present authors investigated the excretion, distribution and pharmacokinetics of the novel potential antirheumatic agent flobufen and its active metabolite after p.o. and i.v. doses of 2, 10 and 50 mg/kg administered to rats. The drug is resorbed well from the digestive tract and mostly it is metabolized to the principal metabolite M, which is only slowly excreted from the organism mainly by renal clearance. Within the whole dose range the kinetics of the drug is linear. Binding of flobufen and M to proteins is high (95-99%). The highest concentrations of radioactive metabolites (mostly M) were found in the plasma, liver, lungs, kidneys, connective tissue and inflammatory foci. The penetration of metabolites through the placenta and excretion in human milk are relatively important.  相似文献   
995.
996.
A mouse monoclonal antibody (MAb 6B9, isotype IgM) was raised against autopsy tissue samples from the central nervous system (CNS) of multiple sclerosis (MS) patients. By immunofluorescence microscopy, MAb 6B9 intensely stains most or all cells in fetal rats. However, MAb 6B9 differentially stains various cell types in adult rats. Neurons, ependymal cells, and adrenal chromaffin cells are stained intensely, whereas astrocytes and oligodendrocytes are not stained. The 6B9-reactive antigen (6B9 antigen) is sensitive to periodic acid, but insensitive to treatment with protease, RNase, or hyaluronidase. Results from immunofluorescence microscopy on semithin sections and cultured neuroblastoma cells indicate that 6B9 antigen is intracellular. This is supported by immunoelectron microscopy, where labeling for 6B9 antigen appears in the cytoplasm distinct from any identifiable organelle. Further studies on 6B9 antigen should reveal its chemical nature as well as the significance of developmental changes in its distribution.  相似文献   
997.
The ability of a number of heterocyclic metal chelators to deliver zinc into red cells, to release the liganded zinc to haemoglobin and thereby cause a left shift in the oxygen dissociation curve of intact red cells has been investigated. Incubation of neutrally charged zinc-pyrone and zinc-pyridin-2-one complexes with red cells led to the rapid accumulation of zinc within cells, whereas unliganded zinc in the form of zinc acetate, zinc chloride or zinc sulphate accumulated only slowly. The rate at which zinc was delivered to red cells by pyrone and pyridin-2-one ligands increased with increasing lipid solubility of the ligands. The uptake of zinc into both normal adult and sickle red cells was associated with a dose-dependent increase in the oxygen affinity of haemoglobin. The degree of left shift in the oxygen dissociation curve following the incubation of red cells with zinc-pyrone and -pyridin-2-one complexes suggests that these complexes may find application as agents to increase the oxygen affinity of haemoglobin in sickle cell disease and thereby decrease the probability of intravascular sickling at low tissue oxygen tensions. Ethylmaltol appears to be a particularly useful agent due to its known low toxicity.  相似文献   
998.
Multimodality evoked potentials and early prognosis in comatose patients   总被引:1,自引:0,他引:1  
In 112 comatose patients somatosensory, visual and auditory evoked potentials were registered within 36 hours after the onset of coma or admission. Main causes of coma were head injury, and intracerebral and subarachnoid haemorrhage. The initial bilateral loss of any evoked potential was associated with a mortality of 98%. Normal somatosensory evoked potentials were associated with a survival rate of 74%, while normal visual and normal auditory evoked potentials had a survival rate of 60% and 66%, respectively. It is concluded that SEPs can be valuable for the prognosis of coma after primary brain lesions.  相似文献   
999.
We report a case of left iliofemoral vein thrombosis with extension to the inferior vena cava associated with giant right hydronephrosis secondary to ureteropelvic junction obstruction. Surgery revealed marked infrarenal vena caval compression and deviation to the left side caused by the dilated right renal pelvis, with resultant kinking of the origin of the left iliac vein. It is postulated that the reduction in blood flow caused by this compression and distortion predisposed this patient to venous thrombosis.  相似文献   
1000.
Our understanding of the causes of male infertility and our ability to develop an appropriate range of diagnostic tests are both dependent upon a knowledge of the cellular mechanisms responsible for the regulation of human sperm function. This review examines the intra- and extracellular factors regulating four separate components of human sperm function: sperm transport, sperm-egg recognition, the acrosome reaction and sperm-oocyte fusion. Within each of these areas the fundamental nature of the process, the control mechanisms involved, the availability of appropriate diagnostic tests and the relationship with human infertility have been considered.  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