全文获取类型
收费全文 | 3178篇 |
免费 | 223篇 |
国内免费 | 17篇 |
专业分类
3418篇 |
出版年
2021年 | 28篇 |
2020年 | 19篇 |
2019年 | 24篇 |
2018年 | 27篇 |
2017年 | 27篇 |
2016年 | 50篇 |
2015年 | 81篇 |
2014年 | 87篇 |
2013年 | 146篇 |
2012年 | 165篇 |
2011年 | 147篇 |
2010年 | 106篇 |
2009年 | 105篇 |
2008年 | 135篇 |
2007年 | 133篇 |
2006年 | 127篇 |
2005年 | 154篇 |
2004年 | 139篇 |
2003年 | 138篇 |
2002年 | 136篇 |
2001年 | 125篇 |
2000年 | 117篇 |
1999年 | 117篇 |
1998年 | 64篇 |
1997年 | 51篇 |
1996年 | 31篇 |
1995年 | 28篇 |
1994年 | 26篇 |
1993年 | 30篇 |
1992年 | 92篇 |
1991年 | 68篇 |
1990年 | 56篇 |
1989年 | 73篇 |
1988年 | 62篇 |
1987年 | 51篇 |
1986年 | 43篇 |
1985年 | 43篇 |
1984年 | 39篇 |
1983年 | 33篇 |
1982年 | 17篇 |
1981年 | 19篇 |
1979年 | 24篇 |
1978年 | 21篇 |
1977年 | 29篇 |
1976年 | 15篇 |
1975年 | 22篇 |
1974年 | 17篇 |
1973年 | 15篇 |
1972年 | 17篇 |
1970年 | 15篇 |
排序方式: 共有3418条查询结果,搜索用时 15 毫秒
61.
Basolateral plasma membrane localization of ouabain-sensitive sodium transport sites in the secretory epithelium of the avian salt gland 下载免费PDF全文
The distribution of Na+ pump sites (Na+-K+-ATPase) in the secretory epithelium of the avian salt gland was demonstrated by freeze-dry autoradiographic analysis of [(3)H] ouabain binding sites. Kinetic studies indicated that near saturation of tissue binding sites occurred when slices of salt glands from salt-stressed ducks were exposed to 2.2 μM ouabain (containing 5 μCi/ml [(3)H]ouabain) for 90 min. Washing with label-free Ringer's solution for 90 min extracted only 10% of the inhibitor, an amount which corresponded to ouabain present in the tissue spaces labeled by [(14)C]insulin. Increasing the KCl concentration of the incubation medium reduced the rate of ouabain binding but not the maximal amount bound. In contrast to the low level of ouabain binding to salt glands of ducks maintained on a freshwater regimen, exposure to a salt water diet led to a more than threefold increase in binding within 9-11 days. This increase paralleled the similar increment in Na+-K+-ATPase activity described previously. [(3)H]ouabain binding sites were localized autoradiographically to the folded basolateral plasma membrane of the principal secretory cells. The luminal surfaces of these cells were unlabeled. Mitotically active peripheral cells were also unlabeled. The cell-specific pattern of [(3)H]ouabain binding to principal secretory cells and the membrane-specific localization of binding sites to the nonluminal surfaces of these cells were identical to the distribution of Na+-K+-ATPase as reflected by the cytochemical localization of ouabain-sensitive and K+-dependent nitrophenyl phosphatase activity. The relationship between the nonluminal localization of Na+-K+-ATPase and the possible role of the enzyme n NaCl secretion is considered in the light of physiological data on electrolyte transport in salt glands and other secretory epithelia. 相似文献
62.
Abe M Sogabe Y Syuto T Yokoyama Y Ishikawa O 《Journal of cellular biochemistry》2007,102(5):1290-1299
Fibroblast-collagen matrix contraction has been used as a model system to study how cells organize connective tissue. Previous work showed that lysophosphatidic acid (LPA)-stimulated floating collagen matrix contraction is independent of Rho kinase while platelet-derived growth factor (PDGF)-stimulated contraction is Rho kinase-dependent. The current studies were carried out to determine the signaling mechanisms of basic fibroblast growth factor (bFGF)-stimulated fibroblast-collagen matrix contraction. Both bFGF and LPA promoted equally collagen matrix contraction well. Three different inhibitors, LY294002 for phosphatidylinositol-3-kinase (PI3K), C3 exotransferase for Rho and Y27632 for Rho kinase, suppressed the bFGF-stimulated fibroblast-collagen matrix contraction. With bFGF stimulation, fibroblasts spread with prominent stress fiber network formation and focal adhesions. In the presence of Rho kinase inhibitor, focal adhesions and stress fibers were mostly lost. We demonstrated that bFGF stimulation for fibroblast caused transient Rac and Rho activation but did not activate Cdc42. In addition, bFGF enhanced fibroblast migration in wound healing assay. The present study implicates PI3K, Rac, Rho, and Rho kinase as being involved in bFGF-stimulated collagen matrix contraction. The elucidation of bFGF-triggered signal transduction may be an important clue to understand the roles of bFGF in wound healing. 相似文献
63.
Endothelial progenitor cells (EPC) participate in revascularization and angiogenesis. EPC can be cultured in vitro from mononuclear cells of peripheral blood, umbilical cord blood or bone marrow; they also can be transdifferentiated from mesenchymal stem cells (MSC). We isolated EPCs from Wharton's jelly (WJ) using two methods. The first method was by obtaining MSC from WJ and characterizing them by flow cytometry and their adipogenic and osteogenic differentiation, then applying endothelial growth differentiating media. The second method was by direct culture of cells derived from WJ into endothelial differentiating media. EPCs were characterized by morphology, Dil-LDL uptake/UEA-1 immunostaining and testing the expression of endothelial markers by flow cytometry and RT-PCR. We found that MSC derived from WJ differentiated into endothelial-like cells using simple culture conditions with endothelium induction agents in the medium. 相似文献
64.
The initial rates of phosphorylation of glucose catalysed by glucokinase from Bacillus stearothermophilus were measured over a wide range of glucose, MgATP2-, MgADP- and glucose 6-phosphate concentrations. The results of the effects of the inhibitors on the initial rates suggest that the reaction mechanism is essentially the ordered Bi Bi, in which glucose adds to the enzyme before MgATP2- and glucose 6-phosphate is released from the enzyme after the dissociation of MgADP-, and also suggest that the final step in which glucose 6-phosphate is released is irreversible. For many reaction schemes, the rate equations were derived on the basis of the pseudo-steady-state assumption and were used to correlate the experimental rate data. From this result, we concluded that the reaction obeys the ordered mechanism accompanied by the formation of a non-productive ternary complex, glucose-MgADP--enzyme. By using the experimental Dalziel coefficients phi i, some kinetic parameters were evaluated. The enzyme was characterized by the thermal stability and the low Michaelis constant, the values of which were 54 microM for glucose and 32 microM for MgATP2-. 相似文献
65.
Monoclonal antibodies against the minimal DNA-binding domain in the carboxyl-terminal region of human immunodeficiency virus type 1 integrase 下载免费PDF全文
Ishikawa T Okui N Kobayashi N Sakuma R Kitamura T Kitamura Y 《Journal of virology》1999,73(5):4475-4480
Integrase of human immunodeficiency virus type 1 (HIVIN) consists of 288 amino acids, and its minimum DNA-binding domain (MDBD) (amino acids [aa] 220 to 270) is required for the integration reaction. We produced and characterized four murine monoclonal antibodies (MAbs) to the MDBD of HIVIN (strain LAI). Immunoblot and enzyme-linked immunosorbent assays with truncated HIVINs showed that those MAbs recognized sequential epitopes within the MDBD (aa 228 to 236, 237 to 252, 253 to 261, and 262 to 270). Their binding to HIVIN inhibited terminal cleavage and strand transfer activities but not disintegration activity in vitro. This collection of MAbs is useful for studying the structure and function of the MDBD by complementing mutational analyses and other biochemical studies. 相似文献
66.
T. Ishikawa 《The Journal of membrane biology》1996,153(2):147-159
A Ca2+-activated Cl− conductance in rat submandibular acinar cells was identified and characterized using whole-cell patch-clamp technique. When
the cells were dialyzed with Cs-glutamate-rich pipette solutions containing 2 mm ATP and 1 μm free Ca2+ and bathed in N-methyl-d-glucamine chloride (NMDG-Cl) or Choline-Cl-rich solutions, they mainly exhibited slowly activating currents. Dialysis of
the cells with pipette solutions containing 300 nm or less than 1 nm free Ca2+ strongly reduced the Cl− currents, indicating the currents were Ca2+-dependent. Relaxation analysis of the ``on' currents of slowly activating currents suggested that the channels were voltage-dependent.
The anion permeability sequence of the Cl− channels was: NO−
3 (2.00) > I− (1.85) ≥ Br− (1.69) > Cl− (1.00) > bicarbonate (0.77) ≥ acetate (0.70) > propionate (0.41) ≫ glutamate (0.09). When the ATP concentration in the pipette
solutions was increased from 0 to 10 mm, the Ca2+-dependency of the Cl− current amplitude shifted to lower free Ca2+ concentrations by about two orders of magnitude. Cells dialyzed with a pipette solution (pCa = 6) containing ATP-γS (2 mm) exhibited currents of similar magnitude to those observed with the solution containing ATP (2 mm). The addition of the calmodulin inhibitors trifluoperazine (100 μm) or calmidazolium (25 μm) to the bath solution and the inclusion of KN-62 (1 μm), a specific inhibitor of calmodulin kinase, or staurosporin (10 nm), an inhibitor of protein kinase C to the pipette solution had little, if any, effect on the Ca2+-activated Cl− currents. This suggests that Ca2+/Calmodulin or calmodulin kinase II and protein kinase C are not involved in Ca2+-activated Cl− currents. The outward Cl− currents at +69 mV were inhibited by NPPB (100 μm), IAA-94 (100 μm), DIDS (0.03–1 mm), 9-AC (300 μm and 1 mm) and DPC (1 mm), whereas the inward currents at −101 mV were not. These results demonstrate the presence of a bicarbonate- and weak acid-permeable
Cl− conductance controlled by cytosolic Ca2+ and ATP levels in rat submandibular acinar cells.
Received: 9 January 1996/Revised: 20 May 1996 相似文献
67.
Zhi-Hui Su Osamu Tominaga Takeshi Ohama Eiji Kajiwara Ryoshuke Ishikawa Tokindo S. Okada Keiko Nakamura Syozo Osawa 《Journal of molecular evolution》1996,43(6):662-671
Molecular phylogenetic analyses using mitochondrial NADH dehydrogenase subunit 5 (ND5) gene sequences representing all 15 species and the majority of subspecies or races of theOhomopterus ground beetles from all over the Japanese archipelago have uncovered a remarkable evolutionary history. Clustering of the species in the molecular phylogenetic tree is linked to their geographic distribution and does not correlate with morphological characters. Taxonomically the same species or the members belonging to the same species-group fall out in more than two different places on the ND5 tree. Evidence has been presented against a possible participation of ancestral polymorphism and random lineage sorting or of hybrid individuals for the observed distribution of mitochondrial DNA haplotypes. The most plausible explanation of our results is that parallel evolution took place in different lineages. Most notably,O. dehaanii, O. yaconinus, andO. japonicus in a lineage reveal almost identical morphology with those of the same species (or subspecies) but belonging to the phylogenetically remote lineages.The nucleotide sequence data reported in this paper will appear in the DDBJ, EMBL, and GenBank nucleotide sequence databases with accession numbers D50711-DD-50733 and D87131-D87186. 相似文献
68.
Y. Fukui T. Mogoe Y. G. Jung Y. Terawaki A. Miyamoto H. Ishikawa Y. Fujise S. Ohsumi 《Marine Mammal Science》1996,12(1):28-37
Spermatozoa from 21 mature minke whales ( Balaenoptera acutorostrata ) taken in the Antarctic Ocean for Japanese research were recovered from vasa deferentia, diluted 1:9 in a Tris-based diluent, and frozen at - 80°C on board the vessel. After a period ranging from 45 to 125 d, the samples were transferred to liquid nitrogen and transported to the laboratory. After thawing at 37°C the motility (percentage of motile spermatozoa), vitality (proportion of live spermatozoa), and sperm concentration were determined for each sample. These values were tested for correlations with morphological measurements (body size, body weight, testis weight) and serum concentrations of progesterone (Pd), estradiol-17β (E2), and testosterone (T). Ten of 21 samples had motile spermatozoa (2%-40%). Although no motile spermatozoa were observed in 1.1 samples, all sperm samples were examined by eosinnigrosin staining and showed vitality levels of 3%44%. It was found that the motility (Y = 0.54) and vitality (r = 0.53) of the spermatozoa were significantly (P < 0.01) correlated with the E2 levels (8.50 ± 1.80 pg/ml). Serum T levels (0.07 ± 0.02 ngml) were significantly correlated with the E2 levels (r = 0.58, P < 0.01>, but sperm concentrations were not correlated with either Ea or T levels. The present study demonstrates that spermatozoa of minke whales can be successfully cryopreserved. 相似文献
69.
Effects of lactoferrin and lactoperoxidase‐containing food on the oral microbiota of older individuals 下载免费PDF全文
Manabu Nakano Hiroyuki Wakabayashi Hirosuke Sugahara Toshitaka Odamaki Koji Yamauchi Fumiaki Abe Jin‐Zhong Xiao Kohji Murakami Kentaro Ishikawa Shouji Hironaka 《Microbiology and immunology》2017,61(10):416-426
70.
Ishikawa Keiko; Kamada Hiroshi; Yamaguchi Isomaro; Takahashi Nobutaka; Harada Hiroshi 《Plant & cell physiology》1988,29(3):461-466
Carrot and tobacco plants were transformed with Agrobacteriumtumefaciens harboring wild-type, aux or cyt Tiplasmids. In tobacco, these wild and mutant Ti plasmids inducedthe formation of non-morphogenic galls, galls with shoots, andgalls with roots, respectively. In carrot, however, transformationwith any of these plasmids resulted in only the formation ofamorphous tumors. Determination of IAA and cytokinin contentsshowed that in tobacco, significantly high amounts of cytokininsor IAA are present in the cells transformed with Ti plasmidspossessing cytokinin or IAA biosynthetic genes, respectively.In carrot, cytokinin contents were also high in the cells transformedwith Ti plasmids having cytokinin biosynthetic genes, whereasIAA contents of the cells were similar regardless of the plasmidsused for transformation. These results suggest that the mechanism regulating IAA metabolismmay be different in tobacco and carrot. (Received June 25, 1987; Accepted February 1, 1988) 相似文献