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   549篇
  免费   8篇
  2022年   6篇
  2021年   6篇
  2020年   8篇
  2019年   5篇
  2018年   4篇
  2017年   15篇
  2016年   15篇
  2015年   7篇
  2014年   10篇
  2013年   21篇
  2012年   21篇
  2011年   17篇
  2010年   18篇
  2009年   7篇
  2008年   23篇
  2007年   24篇
  2006年   19篇
  2005年   24篇
  2004年   14篇
  2003年   9篇
  2002年   18篇
  2001年   15篇
  2000年   20篇
  1999年   10篇
  1998年   6篇
  1992年   5篇
  1990年   6篇
  1989年   12篇
  1988年   12篇
  1987年   13篇
  1986年   5篇
  1985年   9篇
  1984年   8篇
  1983年   7篇
  1982年   4篇
  1981年   3篇
  1979年   15篇
  1978年   4篇
  1976年   6篇
  1975年   11篇
  1974年   18篇
  1973年   9篇
  1972年   5篇
  1971年   13篇
  1970年   7篇
  1969年   6篇
  1968年   8篇
  1967年   9篇
  1966年   9篇
  1965年   3篇
排序方式: 共有557条查询结果,搜索用时 15 毫秒
41.
42.
The complex dielectric permittivity of salt solutions with positive and negative salvation as well as healthy and cicatricially changed human skin in situ at the frequencies of 42 and 56.6 GHz was measured. The relation between the dielectric characteristics of water and diluted salt solutions and changes in their structural organization conditioned by different temperatures of samples and the type of salvation of electrolytes was studied. The differences in the dielectric characteristics of healthy and cicatricially changed skin are interpreted in terms of the dependence of the structural organization of interstitial fluids on the morphological and functional state of biological tissues.  相似文献   
43.
A possibility is discussed of use of methods of nonlinear dynamics for analysis of spontaneous EEG and of the EEG caused by low acoustic stimuli in healthy people and in patients with epilepsy. The use of methods of nonlinear dynamics—the fractal dimension of EEG—in clinical and scientific practice is described.  相似文献   
44.
Two IncP-9 naphthalene degradative plasmids pOV17 and pBS216 were transferred into plant growth-promoting Pseudomonas which were represented by species P. aureofaciens, P. chlororaphis, P. fluorescens, and P. putida. The strains with the same plasmid differed significantly by their growth parameters, stability of the plasmid and plant protective effect from naphthalene action. Strains P. putida 53a(pOV17) and P. chlororaphis PCL1391(pOV17) demonstrated higher population number in the rhizosphere. Moreover, they protected the mustard plants from naphthalene toxic influence more effectively than the wild type strain P. aureofaciens OV17(pOV17). The activity of catechol-2,3-dioxygenase in the strains with the plasmid pOV17 was higher than that in strains with the plasmid pBS216. The strain P. putida 53a(pOV17) with high catechol-2,3-dioxygenase activity has been demonstrated to have the best protective effect. The strain P. putida 53a(pBS216) without catechol dioxygenases activities did not have protective effect but suppressed the plant germination.  相似文献   
45.
In Agaricus bisporus all cytological studies performed until now concerned the pseudohomothallic and bisporic var. bisporus. In the past 12 y two tetrasporic varieties have been described, the heterothallic var. burnettii and the homothallic var. eurotetrasporus. Our aim was to compare the behavior of the nuclei in the vegetative and reproductive cells of the three varieties with light microscopy (Feulgen and DAPI staining) and transmission electron microscopy. Most of the vegetative cells contained 3-5 nuclei in the three varieties. Nuclear migrations through the septum were detected. In the basidia relative locations of nuclei and vacuoles, meiotic spindle alignments, relative content of nuclear DNA and synaptonemal complexes were measured or observed. From the observation of numerous asynchronous second division of meiosis within basidia of var. bisporus and var. burnettii a new hypothesis emerges to explain the nonrandom distribution of the four meiotic products in the two spores of the bisporic basidia. Karyogamy and meiosis similarly occurred in the three varieties. In the case of A. bisporus var. eurotetrasporus this implies that the reproductive mode is sexual and therefore homothallic in the strict sense. The three different types of life cycles are described.  相似文献   
46.
47.
The data on the in vitro and in vivo (into embryonic disk) retroviral-mediated transfer of genetic information into chicken embryonic cells are presented. The estimated transformation frequency of the cultured target cells constituted 8 x 10(-4) to 5 x 10(-3). A transgenic rooster, carrying recombinant DNA in blood, heart, liver, and intestine cells, was obtained.  相似文献   
48.
49.

Background

Leishmaniasis is a disease caused by protozoan parasites of genus Leishmania. The frequent involvement of Leishmania tropica in human leishmaniasis has been recognized only recently. Similarly as L. major, L. tropica causes cutaneous leishmaniasis in humans, but can also visceralize and cause systemic illness. The relationship between the host genotype and disease manifestations is poorly understood because there were no suitable animal models.

Methods

We studied susceptibility to L. tropica, using BALB/c-c-STS/A (CcS/Dem) recombinant congenic (RC) strains, which differ greatly in susceptibility to L. major. Mice were infected with L. tropica and skin lesions, cytokine and chemokine levels in serum, and parasite numbers in organs were measured.

Principal Findings

Females of BALB/c and several RC strains developed skin lesions. In some strains parasites visceralized and were detected in spleen and liver. Importantly, the strain distribution pattern of symptoms caused by L. tropica was different from that observed after L. major infection. Moreover, sex differently influenced infection with L. tropica and L. major. L. major-infected males exhibited either higher or similar skin pathology as females, whereas L. tropica-infected females were more susceptible than males. The majority of L. tropica-infected strains exhibited increased levels of chemokines CCL2, CCL3 and CCL5. CcS-16 females, which developed the largest lesions, exhibited a unique systemic chemokine reaction, characterized by additional transient early peaks of CCL3 and CCL5, which were not present in CcS-16 males nor in any other strain.

Conclusion

Comparison of L. tropica and L. major infections indicates that the strain patterns of response are species-specific, with different sex effects and largely different host susceptibility genes.  相似文献   
50.
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