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   1255538篇
  免费   73557篇
  国内免费   1413篇
耳鼻咽喉   16274篇
儿科学   41387篇
妇产科学   31814篇
基础医学   170220篇
口腔科学   31275篇
临床医学   107793篇
内科学   236227篇
皮肤病学   25276篇
神经病学   97831篇
特种医学   52002篇
外国民族医学   201篇
外科学   193195篇
综合类   24317篇
现状与发展   1篇
一般理论   266篇
预防医学   92426篇
眼科学   27826篇
药学   96161篇
  8篇
中国医学   3491篇
肿瘤学   82517篇
  2021年   8181篇
  2019年   8293篇
  2018年   32509篇
  2017年   25620篇
  2016年   28887篇
  2015年   12519篇
  2014年   16618篇
  2013年   23658篇
  2012年   38238篇
  2011年   53131篇
  2010年   37266篇
  2009年   29197篇
  2008年   49164篇
  2007年   53398篇
  2006年   33893篇
  2005年   33728篇
  2004年   33550篇
  2003年   33193篇
  2002年   30304篇
  2001年   60579篇
  2000年   62206篇
  1999年   51348篇
  1998年   12752篇
  1997年   11282篇
  1996年   11169篇
  1995年   10500篇
  1994年   9517篇
  1993年   8972篇
  1992年   38005篇
  1991年   36528篇
  1990年   36012篇
  1989年   34502篇
  1988年   31025篇
  1987年   30128篇
  1986年   28342篇
  1985年   26576篇
  1984年   19302篇
  1983年   16234篇
  1982年   8888篇
  1979年   17115篇
  1978年   11473篇
  1977年   10270篇
  1976年   8892篇
  1975年   10107篇
  1974年   11729篇
  1973年   11351篇
  1972年   10825篇
  1971年   10139篇
  1970年   9318篇
  1969年   8985篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
991.
The short section of the urethra that passes through the urogenital diaphragm is termed the membranous urethra. It is accompanied by several vessels and nerve fibers. In surgery on the membranous urethra the perineal body is of crucial importance, and precise knowledge of the course of the urethra through the pelvic floor is essential. Furthermore, the relationship between the membranous urethra and its accompanying structures is of great importance. These include the branches of the internal pudendal artery, the prostatic venous plexus and the cavernous nerves coursing ventrally from the pelvic plexus. The nerves supplying the membranous urethra were studied in fetuses with the help of a magnifying lens. The results of the dissections are documented by histological sections, photographs and paintings.  相似文献   
992.
Résumé L'utilisation de matériaux d'ostéosynthèse biodégradables a l'avantage d'éviter la réintervention pour extraire le matériel. Les biomatériaux de polymères polyglycolides ont été expérimentés sur plus de 3 600 animaux de laboratoire avant leur introduction en pratique clinique. Depuis 1984 nous les avons utilisés comme matériau d'ostéosynthèse dans près de 1 700 cas parmi lesquels 880 cas de fracture malléolaire, 226 cas d'ostéotomie en chevron pour hallux valgus, 65 cas de fracture de la tête radiale et 54 cas de fracture de l'olécrane. Parmi les 800 premiers cas traités par broches biodégradables nous avons obtenu des résultats favorables et sans incidents dans 91 pour cent des cas. Il y eut 7 cas de fixation défaillante nécessitant une réintervention. Il y a eu 7 cas d'infection superficielle et 3 cas d'infection profonde. Nous avons observé la formation d'une collection séreuse sous-cutanée sans influence sur le résultat radiologique ou clinique dans 52 cas (6,5 %). Au vue de ces résultats et compte tenu des avantages économiques et psychologiques des matériaux biodégradables (pas de réintervention), on peut penser que l'usage de biomatériaux rivalise favorablement avec l'usage de matériaux conventionnels dans certains types d'ostéosynthèse.
Utilization of biodegradable implants in the surgical treatment of fractures and osteotomies
Summary The utilization of biodegradable implants instead of metals in orthopaedic surgery abolishes the need to remove the fixation material. For this study biodegradable rods and screws of self-reinforced polyglycolide, polylactide and lactide-glycolide copolymer were developed and manufactured. The clinical introduction of these implants was preceded by thorough experimental studies with 3 600 animals. From November 1984 the developed biodegradable method of osteofixation was used in 1 700 operations. These included 880 displaced malleolar fractures, 226 chevron-osteotomy for hallux valgus, 65 displaced fracture of the radial head, 54 displaced frature of the olecranon and other fresh fractures or orthopaedic operations. In the first 800 cases operated on using self-reinforced polyglycolide rods the postoperative course was uneventful (91%). Because of failure in the fixation reoperation was needed in 7 cases. A superficial wound infection was observed in 7 cases, deep infection in 3 and transient fluid accumulation in 52 cases (6,5%). Fluid accumulation did not influence the radiological or clinical end-result. The advantages of biodegradable fixation are many-sided. There is a costbenefit and clinical capacity is free for other use, and psychological advantages must be emphasised because removal of implants is not needed. The over all results of this study were considered favourable.
  相似文献   
993.
994.
A modified enzyme immunoassay based on adsorption of antihepatitis A virus (HAV) IgG-HRPO conjugate and monoclonal antibodies to HAV were used to investigate antigenic differences between mature HAV virions and subviral particles with different buoyant densities in CsCl produced in HAV-infected cells. The mature virions (1.34 g/cm3) appeared to have common antigenic determinants with subviral particles (1.20, 1.27, and 1.30 g/cm3) and possess some additional determinants. Nevertheless, both subviral particles and mature virions induced antibodies capable of neutralizing HAV infectivity in tissue culture.  相似文献   
995.
Expression of leptin receptor (OB-R) mRNA was detected in the human anterior pituitary as well as in ACTH-secreting and nonsecreting pituitary adenomas by RT-PCR with primers recognizing all receptor splice variants. Primers specific to the long splice variant of the leptin receptor (OB-Rb), containing the putative intracellular signalling domain, also revealed a strong expression in normal and adenomatous anterior pituitaries. These results indicate that the pituitary is a possible target tissue of leptin action and might be involved in leptin regulation of pituitary hormone secretion.  相似文献   
996.
African Americans are at increased risk for cancer and represent an important target population for programs such as Healthy People 2000, the Cancer Information Service (CIS), and the 5 a Day for Better Health Initiative. Yet, awareness of such programs among rural blacks is unknown. This study assessed awareness of these programs and determined related knowledge and beliefs among rural African Americans. It was undertaken as part of the baseline survey for the Black Churches United for Better Health project, a National Cancer Institute-funded initiative. A minority of respondents (n = 3737) demonstrated name recognition of Healthy People 2000 (23.4%), the CIS (42.4%), and the 5 a Day Program (40.7%). Far fewer (7.4%) were able to correctly identify the recommended daily number of servings of fruits and vegetables. Reported family history of cancer was associated with a greater tendency believe that eating more fruits and vegetables can prevent disease. These findings underscore the need for efforts to reach the rural black community with culturally sensitive and stage appropriate cancer prevention messages. Knowledge of family history of cancer may play an important role in targeting subgroups and delivering effective cancer prevention messages.  相似文献   
997.
Abstract: Polycythaemia vera (PV) is a myeloproliferative disorder characterized by haematopoietic progenitor cells being hypersensitive to cytokines such as erythropoietin, interleukin-3, stem cell factor and insulin-like growth factor 1, which results in an increased production of mature blood cells. The pathogenetic cellular mechanism(s) behind this hypersensitivity to cytokines is unknown, but the number of cytokine receptors and the interaction between ligand and receptor are normal in PV. Interest has therefore focused on post-receptor mechanism(s). Haematopoietic cell phosphatase (HCP) is an intracellular tyrosine phosphatase that has been demonstrated to regulate proliferative signals negatively induced by the cytokines mentioned above. Moreover, motheaten mice that genetically lack HCP have an increased amount of erythroid progenitors that are hypersensitive to Epo, and patients with familial polycythaemia have been shown to exhibit a mutation of the Epo receptor gene that includes the docking site for HCP. We therefore studied mRNA expression of HCP in pure populations of CD34+ cells, granulocytes, platelets and lymphocytes from patients with PV, chronic myeloid leukaemia (CML) or essential thrombocythemia (ET), as well as healthy controls. Using a polymerase chain reaction analysis employing specific primers for HCP, we failed to detect any abnormalities of HCP expression in PV in any of the cell populations that were examined. Moreover, HCP mRNA expression was similar in ET and CML compared to controls. Finally, Western blot analysis revealed a normal HCP protein content in PV granulocytes and platelets. We therefore conclude that neither an impaired expression of the HCP gene nor a defect in HCP protein synthesis is present in PV, and does not seem to play a role in the aetiology of this disorder.  相似文献   
998.
999.
Serum level of sex hormone-binding globulin (SHBG) was measured by immunoradiometric assay in fifty two breast cancer patients and twenty nine healthy female volunteers. The results are as follows: 1) Although the serum SHBG concentration showed no significant difference between the breast cancer group and the healthy control group, the serum SHBG concentration in postmenopause was significantly higher in the breast cancer group (63.8 +/- 31.2nmol/ml/ml; mean +/- S.D.) than in the healthy control group (40.1 +/- 15.4nmol/ml). 2) Subsequently in the postmenopausal breast cancer group, the serum SHBG concentration was significantly higher in the estrogen receptor (ER)-negative cancer group (97.8 +/- 12.7nmol/ml) than in the ER-positive cancer group (55.8 +/- 32.1nol/ml). 3) No significant relationships were showed between the serum SHBG concentration and obesity or serum estradiol concentration in postmenopausal patients. 4) The serum SHBG concentration showed significant decrease 3 months after radical operation for breast cancer in postmenopausal patients. These results suggest the possibility of the SHBG synthesis in breast cancer tissue.  相似文献   
1000.
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