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   42644篇
  免费   1961篇
  国内免费   196篇
耳鼻咽喉   716篇
儿科学   750篇
妇产科学   738篇
基础医学   5520篇
口腔科学   1291篇
临床医学   3012篇
内科学   10247篇
皮肤病学   559篇
神经病学   3507篇
特种医学   1391篇
外科学   7343篇
综合类   183篇
一般理论   2篇
预防医学   1523篇
眼科学   642篇
药学   3476篇
中国医学   87篇
肿瘤学   3814篇
  2023年   220篇
  2022年   459篇
  2021年   801篇
  2020年   402篇
  2019年   549篇
  2018年   660篇
  2017年   510篇
  2016年   617篇
  2015年   643篇
  2014年   852篇
  2013年   1129篇
  2012年   1801篇
  2011年   1925篇
  2010年   1105篇
  2009年   934篇
  2008年   1812篇
  2007年   1971篇
  2006年   1893篇
  2005年   1882篇
  2004年   1844篇
  2003年   1856篇
  2002年   1841篇
  2001年   1633篇
  2000年   1786篇
  1999年   1512篇
  1998年   513篇
  1997年   406篇
  1996年   371篇
  1995年   311篇
  1994年   287篇
  1993年   259篇
  1992年   1111篇
  1991年   924篇
  1990年   905篇
  1989年   944篇
  1988年   836篇
  1987年   834篇
  1986年   786篇
  1985年   772篇
  1984年   532篇
  1983年   425篇
  1982年   223篇
  1979年   485篇
  1978年   275篇
  1977年   251篇
  1975年   209篇
  1974年   224篇
  1971年   230篇
  1969年   230篇
  1968年   216篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
41.
A 48-year-old woman was admitted because of increased bloody sputum. Since she had had a history of repeated thrombotic episodes including venous thrombosis in the lower limbs (21 year old) and pulmonary emboli developing into pulmonary infarction (41 years old), the patient was treated with anti-coagulant therapy using Warfarin for 7 years. Warfarin was discontinued after admission and heparin was administered instead at a relatively low dose of 5,000 units daily, resulting in a considerable diminution of hemoptysis. Unfortunately however, it caused a relapse of active thrombosis associated not only with a significant increase of the product of fibrinolysis (FDP), LDH and GOT but with a concomitant decrease of the platelet count. Hematological examinations concerning coagulation and fibrinolysis remained within a normal range except for the serum concentration of antithrombin III (AT III) and its functional property with regard to the heparin cofactor, which were 8.8 mg/dl and 48%, respectively. Since the findings were consistent with congenital deficiency of AT III, some members of her family were also examined. The concentration of AT III and its activity in the patient's son and her daughter deteriorated in a similar manner, indicating that this was a definite case of congenital deficiency of AT III. The clinical manifestations of 87 cases with congenital AT III deficiency, belonging to 24 families reported in Japan were reviewed.  相似文献   
42.
The effects of testosterone (T) and 17 beta-estradiol (E2) on the prostate of castrated rats were investigated by histopathological and immunocytochemical procedures. A significant increase in prostatic weight occurred after 6 weeks treatment with T alone and in combination with E2. The greatest increase in prostatic weight occurred after the administration of T plus E2. Histopathologically, glandular hyperplasia of the prostate was noted, and the number of bromodeoxyuridine (BrdU)-positive cells showed a significant increase over that induced by testosterone alone.  相似文献   
43.
Cross-resistance to anticancer drugs, termed multidrug resistance (MDR), is functionally associated with the expression of a plasma membrane, energy-dependent, drug efflux pump termed P-glycoprotein (PGP), the product of the mdr1 gene. We have shown previously that MCF-7 breast carcinoma cells transfected with the human mdr1 gene (BC-19 cells) exhibit greater MDR when stably transfected with protein kinase C alpha (PKC alpha). We now demonstrate that transfection of BC-19 cells with the gamma isoform of PKC (BC-19/PKC gamma cells), which is not normally present in BC-19 cells, does not confer increased resistance to doxorubicin, despite a 19-fold increase in PKC activity. All of the increased PKC activity is accounted for by PKC gamma and it is rapidly down-regulated by phorbol dibutyrate, within 15 min of treatment. Endogenous PKC alpha and PKC epsilon activities are not affected by phorbol dibutyrate. The cytotoxicity of doxorubicin was similar in BC-19/neo or BC-19/PKC gamma cells after either 2-hr or continuous drug exposure, and co-treatment with phorbol dibutyrate increased resistance to doxorubicin 4-fold in both cell lines. Phosphorylation of PGP was similar in both cell lines and drug accumulation was not affected by overexpression of PKC gamma. These results demonstrate that transfection of PGP-expressing cells with an atypical isoform of PKC does not confer increased MDR, and they suggest that the regulation of PGP is phenotype specific with respect to the isoform of PKC.  相似文献   
44.
We reviewed 12 cases of infarcts in the territory of the anterior choroidal artery (AChA) on CT and/or MRI. In each case vascular occlusion in the region was verified angiographically. Although the extent of the lesion on CT/MR images was variable, all were located on the axial images within an arcuate zone between the striatium anterolaterally and the thalamus posteromedially. The distribution of the lesions on mutiplanar MRI conformed well to the territory of the AChA demonstrated microangiographically. The variability of the extent of the infarcts may be explained by variations in the degree of occlusive changes in the AChA or the development of collateral circulation through anastomoses between the AChA and the posterior communicating and posterior cerebral arteries. The extent of the lesion appeared to be closely related to the degree of neurological deficit.  相似文献   
45.
The aim of this study was to assess the significance of C3 deposition in IgA nephropathy in children and adolescents. One hundred and two patients aged 5–21 years (57 male and 45 female) were studied. The findings of C3 deposition were classified into 8 groups by immunofluorescent (IF) pattern and intensity as follows: group MC3+ (N = 12): mesangiocapillary pattern and 3+ in intensity; group MC2+ (N = 13): mesangiocapillary and 2+; group MC1 + (N = 4): mesangiocapillary and 1 +; group M3+ (N = 11): mesangial and 3+; group M2+ (N = 24): mesangial and 2+; group M1 + (N=18): mesangial 1 +; group S (N = 12): only segmentally positive; and group N (N = 8): negative. Histological changes were scored semiquantitatively as an activity index (cellular proliferation, necrosis, interstitial cell infiltration, and cellular crescents) and a chronicity index (mesangial sclerosis, segmental and global glomerular sclerosis, fibrous crescents, adhesion and tubulo-interstitial change). IF findings were scored semiquantitatively and laboratory findings were also studied. The following results were obtained: 1) The scores of total activity index in MC groups were higher than in the M, S or N groups, and the greater the degree of C3 deposition, the higher the score; 2) Such result was not evident in the chronicity index; 3) High IF scores of IgG and IgM were found in the MC3+ and MC2+ groups; 4) Hematuria was more severe in MC3+ and MC2+ than in other groups, and proteinuria was more prominent in the MC than other groups. Thus the degree of C3 deposition was parallel with histological activity and urinary findings.  相似文献   
46.
In connection with gallstone (GS) formation after gastrectomy for cancer, we examined alteration of the composition of gallbladder bile after subtotal gastrectomy with truncal vagotomy. Of 11 mongrel dogs with cholecystostomy, 3 underwent B-I and 4 B-II gastrectomy. Four dogs without gastrectomy were served as controls. Bile was collected for 12 months. Bile acids were quantified by GLC. The bile was cultured for bacteriology. TBA did not significantly differ among the three groups of the dogs. In the two gastrectomized groups, CDA (a secondary bile acid) kept a higher level and CA (a primary bile acid) maintained a lower concentration compared with those in the controls. A remarkable increase of non-conjugated bile acids was recognized in both gastrectomized groups. Lithogenicity was low for all of the 3 groups. All but 1 control dog incurred bile infection that persisted long. Black pigment stones containing calcium bilirubinate developed in 1 of the 3 B-I and 2 of the 4 B-II dogs but none in the controls. The bile infection seemed to be involved in the development of GS. As the alteration of bile composition and GS occurred solely in the gastrectomized dogs, subtotal gastrectomy with truncal vagotomy might precipitate the GS formation.  相似文献   
47.
A 23-year-old male with bronchial asthma developed eosinophilia (eosinophils greater than 2,000/mm3) and was observed at our hospital. After using a prescribed indomethacin suppository for fever at home, he experienced an attack of acute chest pain and severe dyspnea. He suffered cardiac arrest while being transferred to the ward. After resuscitation, he was diagnosed as having acute myocardial infarction on the basis of electrocardiographic and ultrasonic cardiographic findings, and marked elevation of serum concentrations of myocardial enzymes. Thereafter, he often complained of precordial pain and abdominal pain. When he was administered an analgesic in another hospital, he developed severe precordial pain, and marked ST elevation was recorded on the electrocardiogram. Coronary angiography revealed no stenosis nor atherosclerotic changes, suggesting that severe spasm of the coronary arteries and direct myocardial injury by eosinophils were the causes of the myocardial infarction-like symptoms and angina pectoris-like attacks. He was diagnosed as having Churg-Strauss syndrome (allergic granulomatous angiitis) on the basis of the clinical findings; skin biopsy and transbronchial lung biopsy findings were consistent with the diagnosis. Following steroid administration, his angina-like attacks and abdominal pain ceased. This patient developed two episodes of acute cardiovascular symptoms upon administration of antipyretic analgesics. This suggests that in cases of Churg-Strauss syndrome with aspirin-induced asthma, physicians must be aware of the cardiovascular complications, and such drugs should be administered with caution.  相似文献   
48.
Clinical features of 16 patients with mild systemic lupus erythematosus (SLE) were compared with those of 21 control patients with moderate or severe disease. Age at the time of diagnosis of SLE was higher in mild disease group. The incidence of the coexistence of Sj?gren's syndrome (SS) at the time of diagnosis of SLE was higher in patients who later developed mild disease. Anti-Sm antibody and decreased levels of C3, C4, and CH50 occurred less frequently in patients with mild disease. SLE patients with the coexistence of SS at the time of diagnosis of SLE may represent a subset with a benign prognosis.  相似文献   
49.
50.
In our previous study (Nishinaka et al., 1989), a chicken B cell line (HU3R27) deficient in thymidine kinase activity was used as a fusion partner for production of chicken monoclonal antibody. Specific antibody-producing hybridomas were initially obtained, but they soon lost the ability to produce antibody in culture. The present report documents the development of an improved fusion cell line. R27H4, for the production of chicken monoclonal antibody. This cell line was obtained by fusion of HU3R27 cells with spleen cells of immunized chicken. Fusion of R27H4 cells with spleen cells from chicken immunized by keyhole limpet hemocyanin (KLH) resulted in antibody-producing hybridomas. Subcloned hybridomas secreted highly reactive IgG and weakly reactive IgM. Some of the cell lines have been displaying stable antibody secretions for over 6 months.  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