全文获取类型
收费全文 | 3786篇 |
免费 | 179篇 |
国内免费 | 2篇 |
出版年
2022年 | 19篇 |
2021年 | 32篇 |
2020年 | 23篇 |
2019年 | 33篇 |
2018年 | 53篇 |
2017年 | 36篇 |
2016年 | 51篇 |
2015年 | 106篇 |
2014年 | 132篇 |
2013年 | 251篇 |
2012年 | 257篇 |
2011年 | 238篇 |
2010年 | 157篇 |
2009年 | 127篇 |
2008年 | 243篇 |
2007年 | 250篇 |
2006年 | 240篇 |
2005年 | 258篇 |
2004年 | 226篇 |
2003年 | 252篇 |
2002年 | 276篇 |
2001年 | 42篇 |
2000年 | 46篇 |
1999年 | 44篇 |
1998年 | 72篇 |
1997年 | 47篇 |
1996年 | 42篇 |
1995年 | 43篇 |
1994年 | 33篇 |
1993年 | 30篇 |
1992年 | 29篇 |
1991年 | 34篇 |
1990年 | 22篇 |
1989年 | 13篇 |
1988年 | 12篇 |
1987年 | 14篇 |
1986年 | 12篇 |
1985年 | 17篇 |
1984年 | 15篇 |
1983年 | 13篇 |
1982年 | 17篇 |
1981年 | 17篇 |
1980年 | 10篇 |
1979年 | 12篇 |
1978年 | 8篇 |
1977年 | 10篇 |
1976年 | 8篇 |
1975年 | 12篇 |
1974年 | 5篇 |
1972年 | 4篇 |
排序方式: 共有3967条查询结果,搜索用时 46 毫秒
961.
Tanaka A Sugimoto H Muta Y Mizuno T Senoo K Obata H Inouye K 《Bioscience, biotechnology, and biochemistry》2003,67(1):207-210
Thermal unfolding of P. cepacia lipase was observed by adiabatic differential scanning microcalorimetry in the absence and presence of calcium ions at pH 8, and thermodynamic parameters of unfolding were evaluated to analyze the unfolding mechanism of the enzyme. The temperature of unfolding was higher at higher concentrations of Ca2+. From the Ca2+ concentration-dependence of the unfolding temperature, the number of calcium ions that dissociated from the enzyme molecule upon unfolding was estimated to be one. These results confirmed the validity of the unfolding mechanism proposed previously: NCa2+ < = => D + Ca2+, where N and D represent the native and denatured states, respectively, of the enzyme. 相似文献
962.
Shinomiya H Nagai K Hirata H Kobayashi N Hasegawa H Liu F Sumita K Asano Y 《Bioscience, biotechnology, and biochemistry》2003,67(6):1368-1375
We previously identified a 65-kDa protein (p65) that was phosphorylated in activated macrophages. It has turned out to be a murine homologue of human L-plastin, which was identified as a novel protein in human cancer cells. p65/L-plastin is characterized by a series of Ca(2+)-, calmodulin-, and actin-binding domains, and is thought to play a crucial role in leukocytes and cancer cells. We have expressed a recombinant (r) p65/L-plastin in Escherichia coli that binds to beta-actin and prepared high-titer antibodies using large amounts of the protein as immunogen. Anti-rp65/L-plastin antibodies recognize native p65/L-plastin as well as rp65/L-plastin and have enabled us to detect the fine structures of intracellular p65/L-plastin, and it was found that its localization was extensively changed by stimulation with bacterial components. We further developed an enzyme-linked immunosorbent assay system and a flow cytometry method using these reagents, which made it possible to measure antibodies, including autoantibodies, against p65/L-plastin and to evaluate the maturation-dependent expression of the protein in leukocytes. 相似文献
963.
Asakawa R Komatsuzawa H Kawai T Yamada S Goncalves RB Izumi S Fujiwara T Nakano Y Suzuki N Uchida Y Ouhara K Shiba H Taubman MA Kurihara H Sugai M 《Molecular microbiology》2003,50(4):1125-1139
Actinobacillus actinomycetemcomitans (Aa) is one of the pathogenic bacteria involved in periodontal diseases. We have previously identified six major outer membrane proteins (Omps) of Aa Y4. Among them is an Omp with high molecular mass, designated Omp100, which has homology to a variety of virulence factors. Electron microscopic observation indicated that Omp100 is randomly localized on the cell surface of Aa. Aa Y4 has been shown to adhere and invade KB or normal human gingival keratinocytes. Anti-Omp100 antibody inhibited 50% of adhesion and 70% of invasion of Aa Y4 to KB cells. An Omp100 knock-out mutant had a decreased adhesion and invasion efficiency of 60%, compared with that of the wild type. Escherichia coli HB101 expressing Omp100 adhered twofold and invaded 10-fold more than the wild-type E. coli HB101. HB101 expressing Omp100 showed resistance to serum by trapping factor H, an inhibitor for C3b, with Omp100. Omp100 induced inflammatory cytokine responses of interleukin (IL)-8, IL-6 and tumour necrosis factor (TNF)alpha in epithelial cells, and induced IL-1beta and TNFalpha production in mouse macrophages. These results indicate that Omp100 is a versatile virulence factor that may demonstrate potential significance in the onset of periodontal diseases related to Aa. 相似文献
964.
Ichiyanagi T Rahman MM Kashiwada Y Ikeshiro Y Shida Y Hatano Y Matsumoto H Hirayama M Tsuda T Konishi T 《Free radical biology & medicine》2004,36(7):930-937
The absorption and metabolism of delphinidin 3-O-beta-d-glucopyranoside (Dp3G), which is the most potent antioxidant among the blueberry anthocyanins, were studied in rats. Dp3G rapidly appeared in the blood plasma within 15 min of oral administration (100 mg/kg body wt). The plasma level of absorbed Dp3G showed two peaks at 15 and 60 min after ingestion and then decreased time-dependently. However, the plasma level was maintained at approximately 30 nmol/l even after 4 h. Besides the Dp3G peak, a single major metabolite peak was detected by HPLC in the blood plasma obtained at 15 min. MS and NMR spectroscopy clarified that the chemical structure of the metabolite was 4'-O-methyl delphinidin 3-O-beta-d-glucopyranoside (methylation of the 4'-OH on the delphinidin B-ring). The present finding of this unique metabolite in anthocyanin metabolism strongly suggests that methylation of the 4'-OH on the flavonoid B-ring is a common metabolic pathway for flavonoids that carry the pyrogallol structure on the B-ring, as the same type of metabolite has been reported for other flavonoids such as epigallocatechin, but not for flavonoids carrying the catechol structure. 相似文献
965.
sigma marY1 is the LTR of the retroelement marY1 from the homobasidiomycete Tricholoma matsutake. Upon integration through transformation, pLC1-hph carrying a sigma marY1 derivative, sigma* marY1, conferred the hygromycin-resistant phenotype stronger than the vector without sigma* marY1 on Lentinula edodes. Based on the densitometric analysis after Southern hybridization, a copy number of the former construct integrated in the genome is much higher than that of the latter. We conclude that sigma marY1 allows multicopy DNA integration and will be useful in the genetic research on this fungal group. 相似文献
966.
967.
Kawashima H Saito T Yoshizato H Fujikawa T Sato Y McEwen BS Soya H 《Life sciences》2004,76(7):763-774
Running training on the treadmill increases the resting hypothalamic corticotropin-releasing hormone (CRH) content in rats, though is still unknown whether and how it occurs in the parvocellular region of the hypothalamic paraventricular nucleus (PVN) where is a predominant region of pituitary-adrenal activity and where CRH and arginine vasopressin (AVP) are colocalized. We thus aimed at examining whether treadmill training would alter the CRH and AVP mRNA levels in the PVN at rest and during acute running with different lengths of a training regime. Male Wistar rats were subjected to treadmill running (approximately 25 m/min, 60 minutes/day, 5 times/week) for training regimes of 0, 1, 2 or 4 weeks. All training regimes induced an adrenal hypertrophy. Plasma corticosterone levels before acute running increased with lengthening the training period. Four weeks of training produced a significant increase in the resting CRH, but not AVP, mRNA levels in the PVN though relatively shorter training regimes did not. Acute responses of lactate and ACTH release were reduced after 2 and 4 weeks of training, respectively. The responsive PVN CRH mRNA level to acute running decreased with 4 weeks of training but increased with relatively shorter training regimes. These results indicate that running training changes the PVN CRH biosynthetic activity with the regime lasting for 4 weeks, which follows adaptive changes in adrenal functions. Thus, running training-induced changes in hypothalamic CRH activity would originate from the PVN and be induced according to the training period. 相似文献
968.
Lateral root of Brassica crops firmly aggregated around Ca-alginate gel beads containing dicalcium phosphate dihydrate and -cyclodextrin (DCPD gel bead) in a phosphate (P)-deficient soil (Nanzyo et al., 2002, Soil Sci. Plant Nutr. 48, 847–853). The first aim of the present study was to identify the component in the DCPD gel beads that accounts for the special root proliferation. This P-foraging root growth was observed in plots applied with either polyolefin-coated NH4H2PO4 (POC-MAP) or DCPD powder instead of the DCPD gel beads. The POC-MAP neither contains Ca, alginate nor -cyclodextrin. The DCPD powder was applied in a similar number of spots with the number of DCPD gel beads. Thus, the essential component in the DCPD gel beads for the P-foraging root growth around them was P. The second aim was to examine the effect of various inorganic P sources on the P uptake of B. rapa nothovar. While significant P uptake was obtained in the plot applied with apatite from Florida, USA, sediment origin (F-Ap), almost no P uptake was obtained in that with apatite from Quebec, Canada, igneous origin in the P-deficient nonallophanic Andisol. Hence, a P-release level from F-Ap was near the lower limit for the P uptake by the B. rapa nothovar. under the present experimental conditions. These results indicate the P foraging characteristics of the Brassica roots contribute to improve the P recovery rate in the agricultural fields with localized application of moderately-soluble P fertilizers. 相似文献
969.
970.
Lorens JB Pearsall DM Swift SE Peelle B Armstrong R Demo SD Ferrick DA Hitoshi Y Payan DG Anderson D 《Journal of biochemical and biophysical methods》2004,58(2):101-110
As contemporary "genomics" steadily reveals an increasing number of novel gene sequences, the need for efficient methodologies to functionally characterize these genes in vivo increases significantly. Reliable coupling of target gene expression to a variety of surrogate reporter functions is critical to properly assay novel gene function in complex cell populations. Ideally, independent target and reporter proteins would be derived from a single open reading frame creating a stoichiometric relationship without obscuring subcellular localization. We report here effective strategies for assaying gene function through the stable production of chimeric polyproteins, processed intracellularly by inclusion of an intervening 19-amino-acid sequence from the 2A region of the Foot and Mouth Disease virus. Using drug-resistance and flow cytometry-based assay systems, we demonstrate that diverse protein functions are effectively delivered to various cell types by retroviral constructs as single 2A-cleaved polyproteins. For example, cells infected with a retrovirus encoding a nuclear cell cycle regulator, linked via the 2A-motif to a marker membrane protein, showed a direct correlation between cell cycle arrest and surface marker level. This demonstrates the utility of this methodology for stable and stoichiometric delivery of distinctly localized protein functionalities. In particular, the ability to exploit multiple cellular functions will serve to accelerate the functional characterization of gene products and facilitate novel gene therapy approaches. 相似文献