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   8695篇
  免费   680篇
  9375篇
  2023年   89篇
  2022年   128篇
  2021年   253篇
  2020年   135篇
  2019年   179篇
  2018年   215篇
  2017年   199篇
  2016年   305篇
  2015年   471篇
  2014年   517篇
  2013年   662篇
  2012年   742篇
  2011年   691篇
  2010年   408篇
  2009年   441篇
  2008年   526篇
  2007年   447篇
  2006年   422篇
  2005年   408篇
  2004年   374篇
  2003年   330篇
  2002年   316篇
  2001年   100篇
  2000年   63篇
  1999年   85篇
  1998年   94篇
  1997年   80篇
  1996年   63篇
  1995年   50篇
  1994年   44篇
  1993年   49篇
  1992年   36篇
  1991年   28篇
  1990年   29篇
  1989年   27篇
  1988年   22篇
  1987年   29篇
  1986年   13篇
  1985年   28篇
  1984年   31篇
  1983年   24篇
  1982年   24篇
  1981年   22篇
  1980年   14篇
  1978年   15篇
  1977年   23篇
  1975年   11篇
  1974年   17篇
  1973年   12篇
  1972年   11篇
排序方式: 共有9375条查询结果,搜索用时 0 毫秒
11.
The structure and absolute configuration of desangeloylshairidin, a guaianolide isolated from Guillonea scabra, have been established by X-ray diffraction analysis. No conformational change was observed in its seven-membered ring between the crystal and deuterochloroform solution states.  相似文献   
12.
The rosette inhibition test was used in the clinical management of organ allografts to estimate the amount of immunosuppressive drugs necessary to prevent rejection. In patients surviving more than three months renal function appeared to be better than in a similar group of patients managed without the test. It is suggested that this was due to a reduction in the number of clinical or subclinical rejection episodes. On the other hand, the test indicates that in many cases the level of immunosuppression should be much higher, and if this advice is followed the patients become increasingly exposed to the risk of infection. In other words, those patients with good renal function remained well, whereas those who might otherwise have rejected their kidney and survived had in fact died of sepsis.  相似文献   
13.
Summary The fluorescent antibody technique was used to study antigenic relationships betweenParacoccidioides loboi and other pathogenic fungi. The findings suggest thatP. loboi is more closely related antigenically to certainP. brasiliensis strains than to others and that it has antigens in common with the yeast form ofHistoplasma capsulatum, H. duboisii, Blastomyces dermatitidis, Candida albicans and also the mycelial form ofCoccidioides immitis. Serum globulins from 3 cases of keloidal blastomycosis were labelled with fluorescein isothiocyanate. These conjugates showed slight or no reactivity withP. loboi, the yeast forms ofP. brasiliensis, H. capsulatum, H. duboisii andB. dermatitidis, However, they stained brightlyC. albicans, serotypes A and B, the tissue form ofC. immitis and the yeast form ofSporotrichum schenckii. Adsorption of these reagents withC. albicans eliminated all staining except that forS. schenckii. These patients had no history of clinical sporotrichosis.Deceased. Last address: Fundacão Gonçalo Moniz, Salvador, Bahia, Brazil. Requests for reprints should be sent to Dr.William Kaplan.Dr.Miranda is in private practice in Rio de Janeiro, Brazil.  相似文献   
14.
Spinalona anophtalma n. gen. n. sp. is describedon parthenogenetic and ephippial females andmales from material collected in a temporary lagoonlocated in the Neovolcanic Province from Mexico at analtitude of 2507 m above sea level. It ischaracterized by a strong armature of the antenna,postabdomen and postabdominal claw, no compound eyeor ocellus, the exopod of thoracic limb IIIwith only four setae and that of P5 with only three setae.This new taxon has no relationwith blind Alona from hypogean habitats.  相似文献   
15.
16.
Tissue biopsies from (1) some chronic inflammatory diseases, (2) a necrotic tumoral process, (3) normal human lymphatic ganglia, and (4) two congenital diseases of the adrenal cortex were selected for study. A block from each biopsy was fixed in glutaraldehyde-paraformaldehyde; a second block was fixed in 10% formaldehyde. In all cases septate junctions between digestive vacuoles did occur in phagocytic cells and some adrenal cortex cells fixed in formaldehyde. These junctions were similar to those reported recently for malakoplakia phagocytes. Consistently, they were not found to attach organelles other than lysosomes derivatives. Both phagocytes and adrenal cortex cells in the material fixed in glutaraldehyde-paraformaldehyde did not display adhesive specializations between digestive vacuoles. This suggests that the septate junctions described herein are artifactuous structures induced by formaldehyde. There is, however, a certain degree of specificity of cells having the capability of developing these septate junctions. It is assumed that the coating material of digestive organelles in phogocytes and some other cells would be responsible for both cell specificity and organelle specificity of the formaldehyde-induced septate junctions.  相似文献   
17.
18.
19.
Summary In this paper are studied in E. coli K12 the influence of the bacterial Rec and phage Red recombination systems on the rescue of the O + gene from the prophage by a superinfecting O - phage, UV irradiated or not. In the absence of UV irradiation the Red system produces more recombinants that does the Rec system, and its action requires DNA replication. The presence of UV lesions in the DNA facilitates the action of the Rec system, which is more efficient in this instance than the Red system and can act in the absence of DNA replication. In all cases, there is a cooperation between the two generalized recombination systems.  相似文献   
20.
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