全文获取类型
收费全文 | 3479篇 |
免费 | 240篇 |
出版年
2024年 | 4篇 |
2023年 | 12篇 |
2022年 | 53篇 |
2021年 | 76篇 |
2020年 | 45篇 |
2019年 | 71篇 |
2018年 | 101篇 |
2017年 | 75篇 |
2016年 | 132篇 |
2015年 | 209篇 |
2014年 | 218篇 |
2013年 | 253篇 |
2012年 | 321篇 |
2011年 | 330篇 |
2010年 | 218篇 |
2009年 | 168篇 |
2008年 | 237篇 |
2007年 | 225篇 |
2006年 | 172篇 |
2005年 | 173篇 |
2004年 | 139篇 |
2003年 | 128篇 |
2002年 | 107篇 |
2001年 | 44篇 |
2000年 | 48篇 |
1999年 | 40篇 |
1998年 | 17篇 |
1997年 | 12篇 |
1996年 | 9篇 |
1995年 | 10篇 |
1994年 | 4篇 |
1993年 | 7篇 |
1992年 | 14篇 |
1991年 | 5篇 |
1990年 | 2篇 |
1989年 | 3篇 |
1988年 | 3篇 |
1987年 | 2篇 |
1986年 | 3篇 |
1985年 | 2篇 |
1982年 | 3篇 |
1977年 | 2篇 |
1976年 | 2篇 |
1975年 | 2篇 |
1970年 | 1篇 |
1969年 | 3篇 |
1968年 | 1篇 |
1967年 | 5篇 |
1965年 | 1篇 |
1961年 | 1篇 |
排序方式: 共有3719条查询结果,搜索用时 453 毫秒
1.
Virginia Edgcomb William Orsi John Bunge Sunok Jeon Richard Christen Chesley Leslin Mark Holder Gordon T Taylor Paula Suarez Ramon Varela Slava Epstein 《The ISME journal》2011,5(8):1344-1356
Microbial diversity and distribution are topics of intensive research. In two companion papers in this issue, we describe the results of the Cariaco Microbial Observatory (Caribbean Sea, Venezuela). The Basin contains the largest body of marine anoxic water, and presents an opportunity to study protistan communities across biogeochemical gradients. In the first paper, we survey 18S ribosomal RNA (rRNA) gene sequence diversity using both Sanger- and pyrosequencing-based approaches, employing multiple PCR primers, and state-of-the-art statistical analyses to estimate microbial richness missed by the survey. Sampling the Basin at three stations, in two seasons, and at four depths with distinct biogeochemical regimes, we obtained the largest, and arguably the least biased collection of over 6000 nearly full-length protistan rRNA gene sequences from a given oceanographic regime to date, and over 80 000 pyrosequencing tags. These represent all major and many minor protistan taxa, at frequencies globally similar between the two sequence collections. This large data set provided, via the recently developed parametric modeling, the first statistically sound prediction of the total size of protistan richness in a large and varied environment, such as the Cariaco Basin: over 36 000 species, defined as almost full-length 18S rRNA gene sequence clusters sharing over 99% sequence homology. This richness is a small fraction of the grand total of known protists (over 100 000–500 000 species), suggesting a degree of protistan endemism. 相似文献
2.
Barakaeli Abdieli Ndosi Hansol Park Dongmin Lee Seongjun Choe Yeseul Kang Tilak Chandra Nath Mohammed Mebarek Bia Chatanun Eamudomkarn Hyeong-Kyu Jeon Keeseon S. Eom 《The Korean journal of parasitology》2020,58(6):653
Spirometra tapeworms (Cestoda: Diphyllobothriidae) collected from carnivorous mammals in Tanzania were identified by the DNA sequence analysis of the mitochondrial cytochrome c oxidase subunit 1 (cox1) and internal transcribed spacer 1 (ITS1), and by morphological characteristics. A total of 15 adult worms were collected from stool samples and carcasses of Panthera leo, Panthera pardus, and Crocuta crocuta in the Serengeti and Selous ecosystems of Tanzania. Three Spirometra species: S. theileri, S. ranarum and S. erinaceieuropaei were identified based on morphological features. Partial cox1 sequences (400 bp) of 10 specimens were revealed. Eight specimens showed 99.5% similarity with Spirometra theileri (), 1 specimen showed 99.5% similarity with the Korean S. erinaceieuropaei and 1 specimen had 99.5% similarity with Myanmar S. ranarum. Sequence homology estimates for the ITS1 region of S. theileri were 89.8% with S. erinaceieuropaei, 82.5% with S. decipiens, and 78.3% with S. ranarum; and 94.4% homology was observed between S. decipiens and S. ranarum. Phylogenetic analyses were performed with 4 species of Spirometra and 2 species of Dibothriocephalus (=Diphyllobothrium). By both ML and BI methods, cox1 and ITS1 gave well supported, congruent trees topology of S. erinaceieuropaei and S. theileri with S. decipiens and S. ranarum forming a clade. The Dibothriocephalus species were sisters of each other and collectively forming successive outgroups. Our findings confirmed that 3 Spirometra species (S. theileri, S. ranarum, and S. erinaceieuropaei) are distributed in the Serengeti and Selous ecosystems of Tanzania. MK955901相似文献
3.
Kateryna Raykova Melina V. Jones Hwa Huang Paul F. Hoffman Michael Levy 《Journal of visualized experiments : JoVE》2015,(99)
The rat optic nerve is a useful model for stem cell regeneration research. Direct injection into the rat optic nerve allows delivery into the central nervous system in a minimally-invasive surgery without bone removal. This technique describes an approach to visualization and direct injection of the optic nerve following minor fascial dissection from the orbital ridge, using a conjunctival traction suture to gently pull the eye down and out. Representative examples of an injected optic nerve show successful injection of dyed beads. 相似文献
4.
5.
Kiyoshi Takahashi Katsuya Miyatani Hiroyuki Yanai Ho Jong Jeon Kotaro Fujiwara Tadashi Yoshino Kazuhiko Hayashi Tadaatsu Akagi Ken Tsutsui Koichi Mizobuchi 《Virchows Archiv. B, Cell pathology including molecular pathology》1992,62(1):105-113
Monocytic leukemia (MoL) cells were obtained from the peripheral blood of a patient in whom the leukemic cells infiltrating
various lymphoreticular organs exhibited features intermediate between interdigitating reticulum cells (IDC) and ordinary
phagocytic macrophages, whereas the leukemic cells in the peripheral blood were essentially monocytic and lacked such features.
Peripheral blood CD4+ T-cells were established as an interleukin-2-dependent T-cell line. When the MoL cells were exposed
for a few days to conditioned medium from the T-cell line, they extended several dendritic cytoplasmic projections and became
intensely positive for HLA-DR antigen, cytoplasmic S-100β protein, and CD1 antigen. Functionally, the conditioned medium significantly
down-regulated Fc-mediated and Fc-independent phagocytic activities, and the levels of lysosomal enzymes such as lysozyme
and nonspecific esterase in the MoL cells. Moreover, the conditioned medium significantly up-regulated the accessory cell
function of the MoL cells as measured by the primary allogenic mixed leukocyte reaction (MLR). Furthermore, the conditioned
medium significantly down-regulated the expression of CD14 antigen.
Biochemical analysis indicated that the factor responsible for these changes is a protein which is distinct from known human
cytokines and whose molecular weight is approximately 31 kDa. These findings suggest that IDC are closely related the monocytic
lineage and that helper T-cells play an important role in constructing the microenvironment of T-lymphoid tissues which is
necessary for the differentiation and maturation of IDC. 相似文献
6.
7.
Direct repeats flanking the Bacteroides transposon Tn4351 are insertion sequence elements. 总被引:11,自引:5,他引:6 下载免费PDF全文
The clindamycin-erythromycin resistance (Ccr Emr) region of the Bacteroides transposon Tn4351 is flanked by direct repeats. This study showed that the direct repeats are insertion sequence (IS) elements. Although both IS elements can mediate transfer of the chloramphenicol (Cmr) marker on pBR328 by cointegrate formation with the conjugal IncW plasmid R388, IS4351R-mediated transfer of Cmr occurred at a consistently lower frequency than did the transfer mediated by IS4351L. Analysis of plasmids from the resultant transconjugants revealed IS-mediated activities such as deletions, tandem duplication of IS4351L, and excision of IS4351R. 相似文献
8.
9.
10.
The fate of a membrane protein of the amoeba plasmalemma was studied by means of 125I iodination by lactoperoxidase, gel electrophoresis, radioautography and gamma counting. There was only one iodinatable polypeptide group with a molecular weight (MW) of 175 000 on the external surface of the plasmalemma. Two hours or more after induced phagocytosis, isolated phagolysosomal membranes contained two other smaller polypeptides with MWs of 70 000 and 35 000, respectively, suggesting that the 175 000 polypeptide was broken down to these smaller components during endocytosis. After 22 h of induced phagocytosis, isolated plasmalemma contained a 35 000 polypeptide group in addition to the 175 000 polypeptide species. The results suggested that some of the iodinatable membrane proteins were altered and recycled during endo- and exocytosis in amoebae, while others were recycled intact. 相似文献