全文获取类型
收费全文 | 3760篇 |
免费 | 189篇 |
国内免费 | 1篇 |
专业分类
3950篇 |
出版年
2021年 | 42篇 |
2019年 | 22篇 |
2018年 | 40篇 |
2017年 | 30篇 |
2016年 | 43篇 |
2015年 | 88篇 |
2014年 | 104篇 |
2013年 | 261篇 |
2012年 | 158篇 |
2011年 | 177篇 |
2010年 | 133篇 |
2009年 | 117篇 |
2008年 | 182篇 |
2007年 | 163篇 |
2006年 | 143篇 |
2005年 | 148篇 |
2004年 | 151篇 |
2003年 | 151篇 |
2002年 | 183篇 |
2001年 | 140篇 |
2000年 | 138篇 |
1999年 | 118篇 |
1998年 | 64篇 |
1997年 | 39篇 |
1996年 | 39篇 |
1995年 | 33篇 |
1994年 | 25篇 |
1993年 | 29篇 |
1992年 | 81篇 |
1991年 | 84篇 |
1990年 | 75篇 |
1989年 | 66篇 |
1988年 | 63篇 |
1987年 | 65篇 |
1986年 | 56篇 |
1985年 | 56篇 |
1984年 | 36篇 |
1983年 | 34篇 |
1982年 | 28篇 |
1981年 | 23篇 |
1980年 | 22篇 |
1979年 | 36篇 |
1978年 | 23篇 |
1977年 | 25篇 |
1976年 | 30篇 |
1975年 | 29篇 |
1974年 | 32篇 |
1973年 | 19篇 |
1969年 | 17篇 |
1968年 | 20篇 |
排序方式: 共有3950条查询结果,搜索用时 0 毫秒
101.
Manabu Yamada Mitsuji Yamashita Takuya Suyama Junko Yamashita Kazuhide Asai Taishi Niimi Nobuhisa Ozaki Michio Fujie Kasthuraiah Maddali Satoki Nakamura Kazunori Ohnishi 《Bioorganic & medicinal chemistry letters》2010,20(19):5943-5946
4-Bromo-3,4-dimethyl-1-phenyl-2-phospholene 1-oxide (3c) was first synthesized from 3,4-dimethyl-1-phenyl-2-phospholene 1-oxide (2c) by a bromo-radical substitution reaction occurred at C-4 position by N-bromosuccinimide and 2,2′-azobisisobutyronitrile. The novel phospha sugar analogue 3c exerted high anti-proliferative effect on U937 cells evaluated by MTT in vitro methods and was much more efficient than that of Gleevec®, which is known as a molecule targeting chemotherapeutical agent. The substitution of 2-phospholenes at C-3 and C-4 position with methyl groups as well as 4-bromo substituent suggests a good anti-proliferative effect. 相似文献
102.
Tadao Ohno Kaoru Saijo-Kurita Naoko Miyamoto-Eimori Tomoko Kurose Yasunobu Aoki Sigehiro Yosimura 《Cytotechnology》1991,5(3):273-277
We developed a simple method for freezing anchorage-dependent cells, including primary cultured rat liver parenchymal cells, without detaching the cells from the culture dish. The method consists of preculture of the cells to confluence, changing the growth medium to a conventional freezing medium, packaging in a container, and storage at –80°C. After thawing and changing the freezing medium to regular growth medium, cell growth was nearly identical to that of cells freshly seeded into a new dish. 相似文献
103.
104.
Yokoro M Suzuki M Yatani M Yamashita H Takahashi Y Tsuji H Kimoto M 《Bioscience, biotechnology, and biochemistry》2012,76(2):400-403
We produced a monoclonal antibody (mAb) against N(G),N(G)-dimethyl-L-arginine (asymmetric dimethylarginine: ADMA), an endogenous competitive inhibitor of nitric oxide synthase (NOS), and developed an enzyme-linked immunosorbent assay (ELISA). The competitive ELISA method using the mAb determined 5 nM-100 nM ADMA, and ADMA levels in human plasma and urine were found to be 0.78 μM and 51.3 μmol/g of creatinine respectively. 相似文献
105.
Yamamizu K Fujihara M Tachibana M Katayama S Takahashi A Hara E Imai H Shinkai Y Yamashita JK 《Cell Stem Cell》2012,10(6):759-770
Timing of cell differentiation is strictly controlled and is crucial for normal development and stem cell differentiation. However, underlying mechanisms regulating differentiation timing are fully unknown. Here, we show a molecular mechanism determining differentiation timing from mouse embryonic stem cells (ESCs). Activation of protein kinase A (PKA) modulates differentiation timing to accelerate the appearance of mesoderm and other germ layer cells, reciprocally correlated with the earlier disappearance of pluripotent markers after ESC differentiation.?PKA activation increases protein expression of G9a, an H3K9 methyltransferase, along with earlier H3K9 dimethylation and DNA methylation in Oct3/4 and Nanog gene promoters. Deletion of G9a completely abolishes PKA-elicited acceleration of differentiation and epigenetic modification. Furthermore, G9a knockout mice show prolonged expressions of?Oct3/4 and Nanog at embryonic day 7.5 and delayed development. In this study, we demonstrate molecular machinery that regulates timing of multilineage differentiation by linking signaling with epigenetics. 相似文献
106.
Kenichi Harada Eiki Yamashita Atsushi Nakagawa Takamitsu Miyafusa Kouhei Tsumoto Takashi Ueno Yoshiharu Toyama Shigeki Takeda 《Biochimica et Biophysica Acta - Proteins and Proteomics》2013,1834(1):284-291
Bacteriophage Mu, which has a contractile tail, is one of the most famous genus of Myoviridae. It has a wide host range and is thought to contribute to horizontal gene transfer. The Myoviridae infection process is initiated by adhesion to the host surface. The phage then penetrates the host cell membrane using its tail to inject its genetic material into the host. In this penetration process, Myoviridae phages are proposed to puncture the membrane of the host cell using a central spike located beneath its baseplate. The central spike of the Mu phage is thought to be composed of gene 45 product (gp45), which has a significant sequence homology with the central spike of P2 phage (gpV). We determined the crystal structure of shortened Mu gp45Δ1-91 (Arg92–Gln197) at 1.5 Å resolution and showed that Mu gp45 is a needlelike structure that punctures the membrane. The apex of Mu gp45 and that of P2 gpV contained iron, chloride, and calcium ions. Although the C-terminal domain of Mu gp45 was sufficient for binding to the E. coli membrane, a mutant D188A, in which the Asp amino acid residue that coordinates the calcium ion was replaced by Ala, did not exhibit a propensity to bind to the membrane. Therefore, we concluded that calcium ion played an important role in interaction with the host cell membrane. 相似文献
107.
Hiroaki Matsubara Yasunobu Shibasaki Mitsuhiko Okigaki Yasukiyo Mori Hiroya Masaki Atsushi Kosaki Yoshiaki Tsutsumi Yoko Uchiyama Soichiro Fujiyama Atsuko Nose Osamu Iba Eriko Tateishi Takamasa Hasegawa Masatsugu Horiuchi Clara Nahmias Toshiji Iwasaka 《Biochemical and biophysical research communications》2012,417(4):1316-1317
108.
By coupling Anisakis larval hemoglobin with cyanogen bromide-activated Sepharose, a stable and sensitive antigen for the indirect fluorescent antibody test for anisakiasis was prepared. Using this antigen, cross-reaction with other helminth infections was minimized and the test was greatly simplified.Furthermore, the results obtained indicate that this technique may be useful not only in the sero-diagnosis of anisakiasis but may also be applicable to the diagnosis of other helminthic diseases. 相似文献
109.
110.
Takeshita T Yasui M Tomioka M Nakano Y Shimazaki Y Yamashita Y 《Applied and environmental microbiology》2011,77(19):6739-6745
Enteral tube feeding is widely used to maintain nutrition for elderly adults with eating difficulties, but its long-term use alters the environment of the oral ecosystem. This study characterized the tongue microbiota of tube-fed elderly adults by analyzing the 16S rRNA gene. The terminal restriction fragment length polymorphism (T-RFLP) profiles of 44 tube-fed subjects were compared with those of 54 subjects fed orally (average age, 86.4 ± 6.9 years). Bar-coded pyrosequencing data were also obtained for a subset of the subjects from each group (15 tube-fed subjects and 16 subjects fed orally). The T-RFLP profiles demonstrated that the microbiota of the tube-fed subjects was distinct from that of the subjects fed orally (permutational multivariate analysis of variance [perMANOVA], P < 0.001). The pyrosequencing data revealed that 22 bacterial genera, including Corynebacterium, Peptostreptococcus, and Fusobacterium, were significantly more predominant in tube-fed subjects, whereas the dominant genera in the subjects fed orally, such as Streptococcus and Veillonella, were present in much lower proportions. Opportunistic pathogens rarely detected in the normal oral microbiota, such as Corynebacterium striatum and Streptococcus agalactiae, were often found in high proportions in tube-fed subjects. The oral indigenous microbiota is disrupted by the use of enteral feeding, allowing health-threatening bacteria to thrive. 相似文献