全文获取类型
收费全文 | 1917篇 |
免费 | 113篇 |
国内免费 | 3篇 |
专业分类
2033篇 |
出版年
2022年 | 7篇 |
2021年 | 25篇 |
2020年 | 7篇 |
2019年 | 12篇 |
2018年 | 26篇 |
2017年 | 21篇 |
2016年 | 37篇 |
2015年 | 52篇 |
2014年 | 53篇 |
2013年 | 96篇 |
2012年 | 114篇 |
2011年 | 98篇 |
2010年 | 50篇 |
2009年 | 51篇 |
2008年 | 87篇 |
2007年 | 103篇 |
2006年 | 106篇 |
2005年 | 111篇 |
2004年 | 100篇 |
2003年 | 89篇 |
2002年 | 81篇 |
2001年 | 57篇 |
2000年 | 74篇 |
1999年 | 53篇 |
1998年 | 22篇 |
1997年 | 20篇 |
1996年 | 30篇 |
1995年 | 22篇 |
1994年 | 19篇 |
1993年 | 17篇 |
1992年 | 32篇 |
1991年 | 33篇 |
1990年 | 23篇 |
1989年 | 32篇 |
1988年 | 37篇 |
1987年 | 34篇 |
1986年 | 28篇 |
1985年 | 21篇 |
1984年 | 16篇 |
1983年 | 11篇 |
1982年 | 22篇 |
1981年 | 16篇 |
1979年 | 16篇 |
1978年 | 5篇 |
1977年 | 8篇 |
1974年 | 5篇 |
1973年 | 7篇 |
1970年 | 5篇 |
1968年 | 7篇 |
1966年 | 5篇 |
排序方式: 共有2033条查询结果,搜索用时 14 毫秒
991.
Mizuo Mizuno Masaya Kato Munekazu Iinuma Toshiyuki Tanaka Arika Kimura Hiroyoshi Ohashi Hideki Sakai Tadashi Kajita 《Journal of plant research》1989,102(3):403-411
High-performance liquid chromatography (HPLC) profiles based on chemical constituents of the leaves of 145 individuals ofSalix sachalinensis were classified into two different patterns: one composed of flavonoids (myricetin and dihydromyricetin), and the other composed
of phenylpropanoid derivatives. This led to the conclusion that two chemical races exist inS. sachalinensis with different biosynthetic abilities to produce secondary metabolites. 相似文献
992.
Prostaglandin E2 attenuates preoptic expression of GABAA receptors via EP3 receptors 总被引:1,自引:0,他引:1
Tsuchiya H Oka T Nakamura K Ichikawa A Saper CB Sugimoto Y 《The Journal of biological chemistry》2008,283(16):11064-11071
Prostaglandin E(2) (PGE(2)) has been shown to produce fever by acting on EP3 receptors within the preoptic area of the brain. However, there is little information about the molecular events downstream of EP3 activation in preoptic neurons. As a first step toward this issue, we examined PGE(2)-induced gene expression changes at single-cell resolution in preoptic neurons expressing EP3. Brain sections of the preoptic area from PGE(2)- or saline-injected rats were stained with an anti-EP3 antibody, and the cell bodies of EP3-positive neurons were dissected and subjected to RNA amplification procedures. Microarray analysis of the amplified products demonstrated the possibility that gene expression of gamma-aminobutyric acid type A (GABA(A)) receptor subunits is decreased upon PGE(2) injection. Indeed, we found that most EP3-positive neurons in the mouse preoptic area are positive for the alpha2 or gamma2 GABA(A) receptor subunit. Moreover, PGE(2) decreased the preoptic gene expression of these GABA(A) subunits via an EP3-dependent and pertussis toxin-sensitive pathway. PGE(2) also attenuated the preoptic protein expression of the alpha2 subunit in wild-type but not in EP3-deficient mice. These results indicate that PGE(2)-EP3 signaling elicits G(i/o) activation in preoptic thermocenter neurons, and we propose the possibility that a rapid decrease in preoptic GABA(A) expression may be involved in PGE(2)-induced fever. 相似文献
993.
Tsuboi Y Munemoto H Ishikawa S Matsumoto K Iguchi-Ariga SM Ariga H 《FEBS letters》2008,582(17):2643-2649
DJ-1 is secreted into the serum and plasma of patients with various diseases. In this study, DJ-1 was found to be secreted into culture media of various cells and the amount of wild-type DJ-1 secreted was two-fold greater than that of mutant DJ-1 of cysteine at 106 (C106). Furthermore, the oxidative status of more than 90% of the DJ-1 secreted from HeLa cells was SOH and SO2H forms of C106. A portion of DJ-1 in cells was localized in microdomains of the membrane. These findings suggest that DJ-1 is secreted through microdomains and that oxidation of DJ-1 at C106 facilitates the secretion. 相似文献
994.
DNA-binding sites for SYCRP1, which is a regulatory protein of the cyanobacterium Synechocystissp. PCC6803, were predicted for the whole genome sequence by estimating changes in the binding free energy () for SYCRP1 for those sites. The values were calculated by summing DeltaDeltaG values derived from systematic single base-pair substitution experiments (symmetrical and cooperative binding model). Of the calculated binding sites, 23 sites with a value <3.9kcal.mol(-1) located upstream or between the ORFs were selected as putative binding sites for SYCRP1. In order to confirm whether SYCRP1 actually binds to these binding sites or not, 11 sites with the lowest values were tested experimentally, and we confirmed that SYCRP1 binds to ten of the 11 sites with a DeltaDeltaG(total) value <3.9kcal.mol(-1). The best correlation coefficient between and the observed DeltaDeltaG(total) for binding of SYCRP1 to those sites was 0.78. These results suggest that the DeltaDeltaG values derived from systematic single base-pair experiments may be used to screen for potential binding sites of a regulatory protein in the genome sequence. 相似文献
995.
Expression and function of tight junctions in the crypt epithelium of human palatine tonsils. 总被引:2,自引:0,他引:2
Mitsuru Go Takashi Kojima Ken-ichi Takano Masaki Murata Shingo Ichimiya Hiroshi Tsubota Tetsuo Himi Norimasa Sawada 《The journal of histochemistry and cytochemistry》2004,52(12):1627-1638
The human palatine tonsils have surface and crypt stratified epithelium and may be initiated via the epithelium to mount immune responses to various presenting antigens. Here we investigated the expression and function of tight junctions in the epithelium of human palatine tonsils from patients with tonsillar hypertrophy or recurrent tonsillitis. Occludin, ZO-1, JAM-1, and claudin-1, -3, -4, -7, -8, and -14 mRNAs were detected in tonsillar hypertrophy. Occludin and claudin-14 were expressed in the uppermost layer of the tonsil surface epithelium, whereas ZO-1, JAM-1, and claudin-1, -4, and -7 were found throughout the epithelium. In the crypt epithelium, claudin-4 was preferentially expressed in the upper layers. In freeze-fracture replicas, short fragments of continuous tight junction strands were observed but never formed networks. In the crypt epithelium of recurrent tonsillitis, the tracer was leaked from the surface regions where occludin and claudin-4 disappeared. Occludin, ZO-1, JAM-1, and claudin-1, -3, -4, and -14, but not claudin-7, mRNAs were decreased in recurrent tonsillitis compared with those of tonsillar hypertrophy. These studies suggest unique expression of tight junctions in human palatine tonsillar epithelium, and the crypt epithelium may possess an epithelial barrier different from that of the surface epithelium. 相似文献
996.
C-glycosyl flavones, kurilensin A (1) and B (2), together with two known compounds, tricin-4'-O-beta-d-glucopyranoside (3) and tricin-5-O-beta-d-glucopyranoside (4), were isolated from hot-water extracts of the leaves of Sasa kurilensis. The structure of the compounds was determined by spectroscopic analyses including 1D, 2D NMR and MS. The absolute configuration of sugar moieties in 1 and 2 was determined by chiral HPLC analyses of the benzoyl derivatives of acid hydrolysis. Compounds 1 and 2 exhibited higher radical scavenging activity than ascorbic acid in the 1,1-diphenyl-2-pycrylhydrazyl (DPPH) assay system. 相似文献
997.
Summary The gene for -CGTase from an alkalophilic bacterium, Bacillus sp. #1011, was cloned in an Escherichia coli phage D69 and recloned in an E. coli plasmid pBR322 and a B. subtilis plasmid pUB110. An E. coli recombinant plasmid pTUE202 and a B. subtilis plasmid pTUB703 were selected from ten plasmids, because the transformants by each of the two plasmids produced the highest amount of extracellular -CGTase in each strain. The plasmids were stably maintained and expressed in each bacterial strain. A common DNA region of approximately 2.5 kb was defined in the ten plasmids, and the enzymatic activity was lost when a part of the common region was deleted. The major product of hydrolysis from starch by the -CGTases of E. coli [pTUB202] and B. subtilis [pTUB703] was -CD as in the case of the enzyme of the parental Bacillus sp. #1011.Abbreviations -CGTase
-cyclodextrin synthetase
- -CD
-cyclodextrin
- -CD
-cyclodextrin
- -CD
-cyclodextrin
- []
designates plasmid-carrier state 相似文献
998.
Wataru Yano Naoko Egi Tomo Takano Naomichi Ogihara 《Primates; journal of primatology》2010,51(3):263-271
We cross-sectionally investigated prenatal ontogeny of craniofacial shape in the two subspecies of the Japanese macaque (Macaca fuscata fuscata and Macaca fuscata yakui) using a geometric morphometric technique to explore the process of morphogenetic divergence leading to the adult morphological difference between the subspecies. The sample comprised a total of 32 formalin-fixed fetal specimens of the two subspecies, in approximately the second and third trimesters. Each fetal cranium was scanned using computed tomography to generate a three-dimensional surface model, and 68 landmarks were digitized on the external and internal surface of each cranium to trace the growth-related changes in craniofacial shape of the two subspecies. The results of our study demonstrated that the two subspecies generally shared the same craniofacial growth pattern. Both crania tend to exhibit relative contraction of the neurocranium in the mediolateral and superoinferior directions, a more superiorly positioned cranial base, a more vertically oriented occipital squama, and a more anteriorly positioned viscerocranium as the cranial size increased. However, distinctive subspecific differences, for example relatively narrower orbital breadth, higher orbit, higher position of the nuchal crest, and more protrudent snout found in Macaca fuscata yakui were already present during the prenatal period. This study demonstrated that morphological differentiation in the craniofacial shape may occur at a very early stage of the fetal period even between closely related subspecies of the Japanese macaque. 相似文献
999.
以兴安落叶松(Larix gmelinii)实生苗为材料,提取总RNA和基因组DNA;利用兼并PCR及RACE技术克隆肌动蛋白基因(Lg-act).序列分析的结果显示,该基因cDNA全长1662 bp,编码377个氨基酸;基因组DNA长度约为2564bp,包含4个内含子,5个外显子.所克隆的Lg-act cDNA序列与GenBank中注册的其它植物肌动蛋白核苷酸序列的相似性均在77%以上,氨基酸序列的相似性高达93%以上.根据高等植物肌动蛋白相似性构建的系统树显示,兴安落叶松肌动蛋白与挪威云杉肌动蛋白之间的亲缘关系较为密切,在进化中分化时间最为接近. 相似文献
1000.
Elena A Takano Thomas Mikeska Alexander Dobrovic David J Byrne Stephen B Fox 《BMC biotechnology》2010,10(1):1-11