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   1095642篇
  免费   74405篇
  国内免费   1518篇
耳鼻咽喉   15311篇
儿科学   35052篇
妇产科学   28817篇
基础医学   156411篇
口腔科学   30183篇
临床医学   96447篇
内科学   209227篇
皮肤病学   24820篇
神经病学   83305篇
特种医学   43738篇
外国民族医学   201篇
外科学   166769篇
综合类   21834篇
现状与发展   1篇
一般理论   263篇
预防医学   75256篇
眼科学   24799篇
药学   87861篇
  7篇
中国医学   2862篇
肿瘤学   68401篇
  2021年   8087篇
  2019年   8129篇
  2018年   11770篇
  2017年   9287篇
  2016年   10544篇
  2015年   11742篇
  2014年   15921篇
  2013年   23018篇
  2012年   31746篇
  2011年   33593篇
  2010年   19691篇
  2009年   18449篇
  2008年   31052篇
  2007年   33223篇
  2006年   33870篇
  2005年   32324篇
  2004年   30918篇
  2003年   29691篇
  2002年   28699篇
  2001年   60553篇
  2000年   62045篇
  1999年   51489篇
  1998年   12768篇
  1997年   11243篇
  1996年   11254篇
  1995年   10528篇
  1994年   9532篇
  1993年   9060篇
  1992年   38182篇
  1991年   36638篇
  1990年   36082篇
  1989年   34659篇
  1988年   31208篇
  1987年   30279篇
  1986年   28521篇
  1985年   26732篇
  1984年   19409篇
  1983年   16280篇
  1982年   8941篇
  1979年   17162篇
  1978年   11522篇
  1977年   10338篇
  1976年   8922篇
  1975年   10144篇
  1974年   11752篇
  1973年   11371篇
  1972年   10841篇
  1971年   10193篇
  1970年   9342篇
  1969年   9037篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
We report 2 cases of diffuse intraperitoneal metastases from testicular carcinoma following transabdominal retroperitoneal lymphadenectomy. This is an unusual pattern of metastasis for nonseminomatous germ cell tumors and it is believed to be the result of direct seeding from lymphatic leakage secondary to surgery. The value of computerized tomography in diagnosing this entity is emphasized.  相似文献   
992.
993.
One hundred consecutive patients who attended the premenstrual syndrome clinics at Groote Schuur and Somerset Hospitals were analysed. The incidence did not correlate with age, marital status or parity. Seventy per cent of patients were employed or were full-time students, and 72% had a regular menstrual pattern. The commonest symptoms were irritability, depression and abdominal bloating.  相似文献   
994.
The Portex blood warming coil (200/700/000) and water bath (500/111/010) were tested by comparing the body temperatures of two groups of patients undergoing similar operations, but having transfusions of different rate and quantity. The skin and oesophageal temperatures in the massively transfused patients (5-31 units) did not differ significantly from those having minor transfusions (1-5 units). The temperatures were well maintained in both groups. The lowest mean oesophageal temperatures, during the transfusions, were 35.2 +/- 0.2 in the massively transfused patients and 35.4 +/- 0.1 (SEM) in the control group. The warming capacity of the Portex blood warmer was therefore sufficient for our patients. If, however, transfusion rates, higher than those in this study (maximum 96 ml min-1 during the rapid transfusion phase) are needed, a more effective blood warmer may be beneficial.  相似文献   
995.
Tumour-promoting phorbol esters such as phorbol 12-myristate 13-acetate (PMA) have been reported to modulate beta-adrenergic receptor responses in various cell types, presumably by the activation of protein kinase C. In the present investigation we assessed the effect of PMA on the beta-adrenergic receptor-adenylate cyclase system of human mononuclear leukocytes (MNL). It was found that incubation of MNL with PMA resulted in a time- and concentration-dependent desensitization of isoproterenol-induced adenylate cyclase activity. However, the effect of PMA was not restricted to the beta-adrenergic receptor system, since basal adenylate cyclase activity and histamine-, prostaglandin E1-, 5'-guanylylimidodiphosphate (GppNHp)-, and NaF-stimulated values were also reduced. By contrast, no effect was found on the forskolin-induced adenylate cyclase activity. The inactive phorbol ester, 4 alpha-phorbol 12,13-didecanoate had no effect on adenylate cyclase at all, suggesting that the observed PMA effect was specifically mediated by activation of protein kinase C. The reduced beta-adrenergic response induced by PMA was not associated with a reduced beta-adrenergic receptor number, indicating uncoupling of this receptor from adenylate cyclase. Isoproterenol competition curves for 3H-dihydroalprenolol binding to membranes from untreated and PMA-treated cells demonstrated that the uncoupling was due to a reduced ability of the agonist to promote formation of the guanine nucleotide-sensitive high affinity state of the receptor. The results indicate that PMA may cause desensitization of catecholamine-responsive adenylate cyclase in MNL, and that the major locus of alteration is the guanine nucleotide regulatory protein.  相似文献   
996.
A number of vitamin D3 metabolites inhibit benzodiazepine- and dimethyl sulfoxide-induced differentiation of Friend erythroleukemia cells. The inhibition is dose dependent and occurs at nM concentrations. The order of potency of these compounds is 1,25-dihydroxycholecalciferol greater than 1,25,26-trihydroxycholecalciferol greater than 1,24R,25-trihydroxycholecalciferol greater than 1 alpha-hydroxycholecalciferol greater than 24R,25-dihydroxycholecalciferol greater than 25S,26-dihydroxycholecalciferol. The inhibition is maximal when the vitamin D3 analogs are added together with the inducer, and becomes progressively decreased with delayed addition. These results suggest that the vitamin D3 metabolites may play a regulatory role in erythropoiesis.  相似文献   
997.
Prolidase was highly purified from human liver and erythrocytes. NaDodSO4/acrylamide gel electrophoresis revealed that these preparations contained a major protein with MW = 56,000. The mass of prolidase was estimated on gel filtration to be MW = 97,000, for both enzyme preparations. A monoclonal antibody was raised against the liver enzyme and a specific antiserum against the erythrocyte enzyme. The monoclonal antibody (EP-2) recognized prolidase from erythrocytes and liver, in equal proportions. The antiserum also recognized the enzyme from erythrocytes and liver. Immunoprecipitation studies with these antibodies suggested only a single species of prolidase in erythrocytes and liver. Using an immobilized monoclonal antibody (EP-2) as an immunoadsorbent, prolidase was partially purified from crude extracts, and the protein of the partially purified enzyme was identified by immunoblotting using antiserum. A protein band with a MW = 56,000 was demonstrated specifically when crude extracts from the liver and erythrocytes were examined using NaDodSO4/acrylamide gel electrophoresis. The subunit protein was absent in erythrocytes from a patient with prolidase deficiency. We propose that the absence of the subunit is one cause of the prolidase deficiency.  相似文献   
998.
Input-output (I/O) functions of hearing aids were measured in response to a 2000-Hz tone burst, having 0.5 ms rise/fall time and 10 ms duration. I/O functions, measured with a hearing-aid analyzer, served as reference conditions. Hearing-aid outputs at onset and during the steady-state portion of the waveform differed; these differences often depended upon stimulus rate. The relation between onset and steady-state estimates of output were not always predictable from hearing-aid attack and release times. These findings indicate that the steady-state output limitation characteristics of hearing aids cannot be estimated from their onset responses. In turn, this suggests that ABR measurements may not provide accurate estimates of the compressive characteristics of hearing aids.  相似文献   
999.
1000.
Sclerosing mucoepidermoid carcinoma (SMEC) with eosinophilia is a rare but distinctive tumor usually affecting the thyroid. SMEC involvement of salivary gland is exceptional, with only six cases in the literature. We present here the first case of an intermediate-grade SMEC, arising from the intraoral minor salivary glands. A particularly interesting finding is the cytoplasmic accumulation of eosinophilic hyaline granules in carcinoma cells, similar to aberrant zymogen-like granules previously described in salivary sclerosing polycystic adenosis.  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