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   58399篇
  免费   5027篇
  国内免费   110篇
耳鼻咽喉   662篇
儿科学   1513篇
妇产科学   1250篇
基础医学   7619篇
口腔科学   1352篇
临床医学   6412篇
内科学   11450篇
皮肤病学   878篇
神经病学   6338篇
特种医学   2716篇
外国民族医学   4篇
外科学   8574篇
综合类   795篇
一般理论   36篇
预防医学   4989篇
眼科学   1472篇
药学   3782篇
  2篇
中国医学   66篇
肿瘤学   3626篇
  2021年   895篇
  2020年   552篇
  2019年   862篇
  2018年   985篇
  2017年   871篇
  2016年   924篇
  2015年   1065篇
  2014年   1345篇
  2013年   2074篇
  2012年   2935篇
  2011年   3100篇
  2010年   1695篇
  2009年   1557篇
  2008年   2782篇
  2007年   2965篇
  2006年   2805篇
  2005年   2618篇
  2004年   2470篇
  2003年   2304篇
  2002年   2301篇
  2001年   1634篇
  2000年   1612篇
  1999年   1448篇
  1998年   630篇
  1997年   590篇
  1996年   540篇
  1995年   512篇
  1994年   446篇
  1993年   397篇
  1992年   1197篇
  1991年   1203篇
  1990年   1124篇
  1989年   1126篇
  1988年   939篇
  1987年   1053篇
  1986年   969篇
  1985年   982篇
  1984年   779篇
  1983年   648篇
  1982年   419篇
  1981年   389篇
  1980年   390篇
  1979年   710篇
  1978年   537篇
  1977年   458篇
  1976年   469篇
  1975年   406篇
  1974年   531篇
  1973年   464篇
  1972年   391篇
排序方式: 共有10000条查询结果,搜索用时 359 毫秒
931.
Lymphocytes separated from venous blood from six dogs who had heterotopic cardiac transplants have been labeled using 111In-oxine. Labeled lymphocytes were reinjected into the dogs and imaging of the heart carried out over the successive 3 or 4 days. For comparison serial ECGs and punch biopsies of the heart were obtained. Abnormal uptake of labeled lymphocytes in the donor heart was clearly visible in three of the six dogs, faintly visible in two and not seen in one. 630 Ci 111In was used in the dog where no uptake was seen and subsequent studies showed this amount of the radiopharmaceutical was toxic to lymphocytes. In the remaining five dogs the mean ratio of uptake of 111In in donor to recipient heart was 14:1 (range 6.5:1–21:1). The lack of substantial uptake in the transplanted heart of two dogs is attributed to a delay in rejection relative to the time the labeled lymphocytes were injected. The results suggest that 111In-labeled lymphocytes have potential as a noninvasive test for detecting rejection of cardiac transplants.J. McKillop is a Harkness Fellow of the Commonwealth FundJ. Wallwork is supported by National Heart Research Fund (UK)  相似文献   
932.
Larson RL  Miller BA 《Hospital pharmacy》1982,17(5):254-5, 258-9
Methods of controlling controlled substance (CS) inventories in unit dose dispensing systems vary. The two extremes are total floor stock of all CS drugs by the use of declining inventory signout sheets on the nursing unit to controlling only Class II and a few selected class III-V items. The method described herein outlines a systematic approach to controlling items on an individual patient basis consistant with the benefits of unit dose dispensing. A CS card assigned to each patient for each of his required controlled substance medications serves as an audit trail for doses consumed by the patient and provides a declining inventory receipt when returned to the pharmacy.  相似文献   
933.
A cell line has been developed from the imaginal wing discs of the lepidopteran insect Trichoplusia ni (Hübner). The cells grow in suspension as fluid-filled, multicellular vesicles. The cell line has been designated IAL-TND1. Two-dimensional electrophoresis (isoelectric focusing and sodium dodecyl sulfate/polyacrylamide gels) of [35S]methionine-labeled proteins revealed similar patterns for IAL-TND1 cells and whole T. ni wing imaginal discs. Additionally, exposure to the insect steroid hormone 20-hydroxyecdysone stimulated the synthesis of the same new proteins in both whole wing discs and IAL-TND1 cell vesicles.  相似文献   
934.
Earlier studies showed that N-acetyl-2-aminofluorene (AAF) ismuch more carcinogenic than N-acetyl-2-amino-7-iodofluorene(AAIF). Subsequently it was found that substitution of C-8 ofguanine bases in DNA with AAF residues resulted in displacementof the guanine bases outside the DNA helix. This did not occurafter similar substitution with AAIF residues. As one approachto assessing the possible importance of this gross conformationaldifference to the carcinogenicity of AAF, the carcinogenic activitiesof two electrophilic esters, N-myristoyloxy-AAF and its 7-iododerivative, were compared by s.c. injection into male Fischerrats. On injection of a total of 64 µmol, each ester induceda high incidence of sarcomas, and the latent periods were similar.N-Myristoyloxy-AAIF was solvolyzed in aqueous media at aboutone-half the rate of N-myristoyloxy-AAF, and it was less than10% as reactive with native DNA as N-myristoyloxy-AAF. N-Myristoyloxy-AAFand N-myristoyloxy-AAIF were each less reactive than the correspondingacetoxy derivatives. These data suggest that the low carcinogenicityof AAIF as compared to that of AAF may not be associated withthe conformations of their adducts in the DNA. This differencein carcinogenicity may be related to differences in the ratesof metabolic activation and inactivation of these two amides.  相似文献   
935.
936.
Seven percent of 400 patients with cervical spine fractures and/or dislocations had unusual lesions of the axis. The authors have analyzed axis injuries by review of radiographs and clinical data and have derived a classification of traumatic conditions. Uncommon traumatic axis abnormalities are discussed with reference to incidence, causes, clinical findings, mechanism of injury, and roentgen characteristics.Picker Scholar, James Picker Foundation  相似文献   
937.
Summary The present study compares the effects of d-amphetamine (d-AMP) and the potent non-amphetamine CNS stimulant, amfonelic acid (AFA), on the firing rate of single midbrain dopaminergic (DA) neurons and on neostriatal DA metabolism (dihydroxyphenylacetic acid—DOPAC). The results indicate that AFA, like d-AMP, reduces the firing rate of DA neurons, although unlike d-AMP, AFA does not cause a decrease in neostriatal DOPAC content and, in fact, enhances that produced by haloperidol (HALO). The AFA-induced decrease in firing rate, like d-AMP, is reversed by the DA receptor blocker HALO, but again unlike d-AMP, the decrease in firing rate is not prevented by catecholamine synthesis inhibition with-methyl-para-tyrosine. Thus, both amphetamine and amfonelic acid have identical electrophysiological effects on DA neurons but act by different mechanisms.  相似文献   
938.
R A Kahn  S D Staggs  W V Miller  F R Ellis 《JAMA》1979,242(19):2087-2090
During the past five years, there has been a sharp increase in the use of packed RBCs (PRBCs) and plasma products, whereas whole blood (WB) transfusions have steadily decreased. In order to determine whether plasma and its derivatives were being used to "reconstitute" whole blood from PRBCs, we performed a retrospective evaluation of all transfusion episodes in ten representative regional hospitals during a five-month period. Our results indicate that PRBCs were transfused 2.5 times more frequently than WB. Plasma products were administered with PRBCs less often than with WB: 14% of all PRBCs vs 24% of all WB units tranfused. The likelihood of a patient receiving plasma was found to correlate with the total amount of blood transfused and the frequency of transfusion. This study provides evidence that, at most, only a small percentage of PRBCs are given in conjunction with plasma as "reconstituted" WB.  相似文献   
939.
940.
Novobiocin demonstrates an effect similar to that of probenecid (the "probenecid effect") in enhancing the therapeutic efficacy of antibiotics excreted mainly by the renal tubules. The ability of cefoxitin, cephalexin, cephalothin and penicillin G to protect mice against infection with Salmonella schottmuelleri was enhanced 2- to 3-fold when the animals were given oral doses of either probenecid or of novobiocin. The efficacy of cephaloridine, excreted mainly by glomerular filtration, was not enhanced by either probenecid or by novobiocin.  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