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   138篇
  免费   2篇
  2022年   2篇
  2021年   3篇
  2020年   1篇
  2019年   2篇
  2018年   1篇
  2017年   3篇
  2016年   1篇
  2015年   4篇
  2014年   4篇
  2013年   3篇
  2012年   2篇
  2011年   5篇
  2010年   6篇
  2009年   6篇
  2008年   3篇
  2007年   5篇
  2006年   5篇
  2005年   8篇
  2004年   1篇
  2003年   4篇
  2001年   3篇
  2000年   4篇
  1999年   3篇
  1998年   3篇
  1997年   4篇
  1996年   6篇
  1995年   2篇
  1993年   2篇
  1992年   2篇
  1991年   4篇
  1990年   3篇
  1989年   2篇
  1988年   5篇
  1987年   1篇
  1986年   3篇
  1985年   5篇
  1984年   2篇
  1982年   2篇
  1981年   2篇
  1980年   1篇
  1979年   1篇
  1978年   1篇
  1976年   2篇
  1972年   1篇
  1971年   3篇
  1970年   1篇
  1968年   1篇
  1967年   1篇
  1965年   1篇
排序方式: 共有140条查询结果,搜索用时 312 毫秒
1.
Transaxial tomoscintigraphy (or single-photon emission computerised tomography) was used to detect secondary deposits of carcinoma in 17 patients who had been injected with iodine-131-labelled monoclonal antibodies against carcinoembryonic antigen. Of 17 tumor sites studied by tomoscintigraphy 16 were detected (sensitivity 94%); five sites had a volume smaller than 10 cm3. Tomoscintigraphy also detected three unknown tumour deposits later confirmed by surgery or radiology. In contrast, when 21 tumour sites in the same patients were studied by rectilinear scintigraphy, only nine tumour sites were detected (sensitivity 43%), of which eight had a volume larger than 50 cm3.  相似文献   
2.
An excretory-secretory (ES) antigen was extracted from supernatants of cell cultures infected with Toxoplasma gondii, purified and controlled according to current standards. In 638 volunteers, the correlation with fluorescent antibody was 94.2% and no false positive skin tests were noted. The skin test did not transform an originally negative serological test into a positive one. For the prevention of congenital toxoplasmosis, this sensitive, specific and inexpensive skin test can be widely used for the detection of immunity to Toxoplasma in women before their first pregnancy. During pregnancy, the detection of specific IgM is very important for the diagnosis of a recently acquired toxoplasmosis and allows for an immediate treatment. For this detection and for the diagnosis of congenital toxoplasmosis, five different serological tests were compared: Indirect Fluorescent Antibody-test (IFA), ELISA test, ELISA test After Capture of IgM (ACCAs), Reverse Enzyme Immuno Assay R-EIA), Double-Sandwich Enzyme Linked ImmunoSorbent Assay (DS-ELISA) and ImmunoSorbent AGglutination Assay (ISAGA). For 37 sera of recently acquired toxoplasmosis, IgM were detected in 98.7% with ISAGA, in 89.5% with DS-ELISA and ELISA in 83% with R-EIA and in 59% with IFA test. The best specificity is obtained with ISAGA, DS-ELISA and R-EIA, from controls with non immune patients (99 cases), patients with chronic toxoplasmosis (77 sera), rheumatoid factors (35 sera) or anti-nuclear antibodies (7 sera). In 21 sera from infants with congenital toxoplasmosis, ISAGA was positive in 13 cases (62%), IFA in 5 cases (24%), ELISA and R-EIA in 2 cases (9.5%) and DS-ELISA in 9 cases (43%).(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
3.
4.
Summary In order to understand the nature of interspecific barriers in Populus, we have explored pollen/pistil interactions in intra- and interspecific crosses Populus nigra x P. nigra and P. nigra x P. alba. The kinetics of pollen-tube growth demonstrated that P. nigra and P. alba pollen tubes have distinct behavioral patterns inside P. nigra pistils. P. alba pollen tubes exhibit an unique S-shaped growth curve and an arrested growth site near the sylodium. P. nigra pollen tubes exhibit two growth phases, in the stigmatic tissues and in the ovarian cavity respectively. P. nigra and P. alba curves diverge 5 h after controlled pollination and could be related to a change in the physiology of the P. nigra pollen tube, which shifts from an autotrophic to a heterotrophic type of nutrition. Protein analysis of pollinated stigmatic extracts (0,6 and 20 h after pollination) revealed qualitative and quantitative differences that are related to the presence of either P. nigra or P. alba pollen tubes inside the stigmatic tissues. Increasing numbers of protein bands were detectable from 0 to 20 h after pollination only in intraspecific cross. Glycoproteins were detected, and the differences observed were dependent of the cross. -Galactosidase activity was found in pollinated stigmas, but an increase in its activity (one isozyme of pHi 4.2) between 6 h and 20 h after pollination was detected only in the intraspecific cross. This enzyme could play a role in heterotrophic pollen-tube nitrition, and its activity could be the final result of a series of interactions started by the initial pollen-stigma dialog.  相似文献   
5.
This study reports that TNF-alpha is a potent mitogen for human bone marrow sternal cells in vitro (assessed by [(3)H]-thymidine incorporation into DNA and cell counts). In contrast, cytokines such as IL-1alpha, IL-1beta, IL-2, IL-3, IL-4, IL-6, LIF, SCF, M-CSF, G-CSF and GM-CSF had no effect. The effect of TNF-alpha on the growth of human bone marrow stromal cells could be of importance during inflammatory processes which take place in the marrow, for example marrow fibrosis.  相似文献   
6.
Persistence of conidia of the entomopathogenic fungus Paecilomyces fumosoroseus exposed to artificial and solar radiation at a constant temperature was studied by monitoring the ability to germinate and to form colonies (colony - forming units , CFUs) . The photic effect of radiation on each of these variables was modelled by a decreasing function of UVB irradiation ( in J m 2) . Germination ability was represented by a logistic function and viability (log CFU) by an infinitely decreasing function . Experiments carried out under artificial conditions , at three different UVB irradiances ( from 0 . 3 to 1 . 6 W m 2) , similar to those observed in nature , confirmed the adequacy of the predictor variable and of the functions chosen for describing these data . The proposed models appeared to be irradiance independent . Under solar radiation , the models were able to describe data collected on three different summer days in France (48 o 51 N , 2 o 06 E) . However , it took a greater amount of solar UVB radiation to produce the same effect as that achieved indoors . This could be explained by differences in radiation spectra . For each model , one set of parameters was sufficient for representing all three sets of data: this constitutes an initial validation of the models proposed .  相似文献   
7.
8.
Madtsoiids constitute a successful group of extinct snakes widely distributed across Gondwana and the European archipelago during Late Cretaceous times, surviving in reduced numbers to the Pleistocene. They are renowned for including some of the largest snakes that have ever crawled on earth, yet diverse small madtsoiids are also known. Uncovering the evolutionary trends that led these snakes into disparate body sizes has been hampered mainly by the lack of phylogenetic consensus and the paucity of taxa with novel combinations of features. Here we describe a new large madtsoiid snake based on isolated vertebrae from the La Colonia Formation (Maastrichtian–Danian) of Patagonia, Argentina. A comprehensive phylogenetic analysis recovers Madtsoiidae as a basal ophidian lineage and the new snake as sister to a clade of mostly big-to-gigantic taxa, providing insights into early stages and evolutionary trends towards madtsoiid gigantism.  相似文献   
9.
Minireview: Parthenogenesis in mammals   总被引:6,自引:0,他引:6  
  相似文献   
10.
To question the relation between uni-and bipedal postural skills, 21 subjects were required to stand on a force platform through uni- and bipedal conditions. These two protocols are commonly used paradigms to assess the balance capacities of healthy and disabled patients. The recorded displacements of the center of pressure (CP) were decomposed along mediolateral and anteroposterior axes and assessed through variance positions and parameters obtained from fractional Brownian motion (fBm) modeling to determine the nature and the spatiotemporal organization of the successive controlling mechanisms. The variances underline the relative independence of the two tasks. Nevertheless, as highlighted by the fBm framework, postural correction is initiated for the unipedal stance after shorter time delays and longer covered distances. When compared to bipedal standing, one of the main characteristics of unipedal standing is to induce better-controlled CP trajectories, as deduced from the scaling regimes computed from the fBm modeling. Lastly, the control of the CP trajectories during the shortest time intervals along the anteroposterior axis appears identical for both uni- and bipedal conditions. Unipedal and bipedal standing controls should thus be viewed as two complementary tasks, each providing specific and complementary insights into the postural control organization.  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