全文获取类型
收费全文 | 3569篇 |
免费 | 169篇 |
国内免费 | 2篇 |
出版年
2022年 | 10篇 |
2021年 | 29篇 |
2020年 | 18篇 |
2019年 | 29篇 |
2018年 | 47篇 |
2017年 | 30篇 |
2016年 | 48篇 |
2015年 | 101篇 |
2014年 | 126篇 |
2013年 | 245篇 |
2012年 | 245篇 |
2011年 | 225篇 |
2010年 | 145篇 |
2009年 | 124篇 |
2008年 | 238篇 |
2007年 | 241篇 |
2006年 | 230篇 |
2005年 | 252篇 |
2004年 | 220篇 |
2003年 | 245篇 |
2002年 | 270篇 |
2001年 | 39篇 |
2000年 | 41篇 |
1999年 | 39篇 |
1998年 | 71篇 |
1997年 | 47篇 |
1996年 | 40篇 |
1995年 | 42篇 |
1994年 | 26篇 |
1993年 | 29篇 |
1992年 | 28篇 |
1991年 | 28篇 |
1990年 | 20篇 |
1989年 | 13篇 |
1988年 | 11篇 |
1987年 | 13篇 |
1986年 | 8篇 |
1985年 | 14篇 |
1984年 | 11篇 |
1983年 | 9篇 |
1982年 | 16篇 |
1981年 | 17篇 |
1980年 | 10篇 |
1979年 | 6篇 |
1978年 | 5篇 |
1977年 | 6篇 |
1976年 | 6篇 |
1975年 | 6篇 |
1974年 | 4篇 |
1971年 | 3篇 |
排序方式: 共有3740条查询结果,搜索用时 46 毫秒
11.
Calcium-binding protein regucalcin increases calcium-independent proteolytic activity in rat liver cytosol 总被引:1,自引:0,他引:1
The effect of regucalcin, isolated from rat liver cytosol, on neutral proteolytic activity in the hepatic cytosol was investigated. The Ca2+-requiring proteinase required 5–10 µM Ca2+ for maximal activity in the presence of a protein substrate (globin). The proteinase activity was markedly elevated by the addition of regucalcin (0.25–2.0 µM) in the absence or presence of Ca2+ (5.0 µM) added. The effect of regucalcin, however, was the greater in the absence of Ca2+ than that in the presence. The pronounced effect of regucalcin on the proteinase activity was also seen in the presence of 1.0 mM EGTA with or without Ca2+ (5.0 µM). In the absence of Ca2+, the regucalcin-increased proteinase activity was clearly inhibited by the presence of anti-regucalcin antiserum (diluted to 240-fold), leupeptin (20 and 200 µg/ml), and heavy metals (25 µM cadmium or 25 µM zinc), although the inhibition was not complete at the concentration used. The present findings suggest that regucalcin increases proteolytic activity in rat liver cytosol, and that regucalcin may activate Ca2+-independent neutral cysteinyl-proteinase. 相似文献
12.
Point mutations in the upstream region of the α-galactosidase A gene exon 6 in an atypical variant of Fabry disease 总被引:5,自引:0,他引:5
Summary Single point mutations in the upstream region of exon 6 of the -galactosidase A gene were found in two Japanese cases of the cardiac form of Fabry disease; 301ArgGln (902GA) in a case that has already been published and 279GlnGlu (835CG) in a new case. They both expressed markedly low, but significant, amounts of residual activity in COS-1 cells. In contrast, two unrelated cases with classic Fabry disease were found to have different point mutations, which showed a complete loss of enzyme activity in a transient expression assay; 328GlyArg (982GA) in the downstream region of exon 6 in one case and two combined mutations, 66GluGln (196GC)/112ArgCys (334CT), in exon 2 in the other. We conclude, on the basis of the results recorded in this study and those in previous reports, that the pathogenesis of atypical Fabry disease is closely associated with point mutations in the upstream region of exon 6 of the -galactosidase A gene. 相似文献
13.
Shiraishi Tomonori; Araki Miwa; Yoshioka Hirofumi; Kobayashi Issei; Yamada Tetsuji; Ichinose Yuki; Kunoh Hitoshi; Oku Hachiro 《Plant & cell physiology》1991,32(7):1067-1075
A pathogenic fungus of pea, Mycosphaerella pinodes, secretesa so-called "suppressor" in its pycnospore germination fluid.The suppressor blocks the defense responses and induces localsusceptibility (accessibility) in pea plants to agents thatare not pathogenic in pea. The suppressor nonspecifically inhibitsthe ATPase activity in plasma membranes prepared from pea, soybean,kidney bean, cowpea and barley plants. However, cytochemicalstudies by electron microscopy indicate that the suppressorspecifically inhibits the ATPase in pea cell membranes, butnot in those of four other plant species tested. That is, thespecificity of the suppressor appears at the cell and/or tissuelevel, but is not evident in vitro. Furthermore, the inhibitoryeffect of the suppressor is temporary because the ATPase activityrecovers 9 h after the treatment. A similar effect was observedafter inoculation with M. pinodes but not with a nonpathogenof pea, M. ligulicola. The role of the suppressor in host-parasitespecificity is discussed. (Received April 9, 1991; Accepted August 6, 1991) 相似文献
14.
D L Jankovic O Abehsira-Amar M Korner C Roth Y Hitoshi K Takatsu J Theze 《Cellular immunology》1988,117(1):165-176
B cell activating factor (BCAF) was initially identified in the supernatant of the murine T helper cell clone 52-3 (52-3 SN) because of its ability to promote activation and proliferation of resting B cells in the absence of any other costimulus. In this paper, we show that 52-3 T helper cells also secrete IL-4 and IL-5 and we have analyzed the influence of these two lymphokines on B cell proliferation induced by BCAF-containing 52-3 SN. Using the neutralizing anti-IL-4 monoclonal antibody 11B11, we observed partial inhibition of B cell proliferation. 52-3 SN free of IL-4 prepared using an immunoabsorbent column was still able to induce significant B cell proliferation. Although recombinant IL-4 alone does not induce B cell proliferation, it increased the proliferation induced by IL-4-free 52-3 SN. Kinetic studies showed that IL-4 is required at the start of B cell cultures in order to exert optimal synergistic effects. In contrast, anti-IL-5 monoclonal antibody NC17 did not affect the B cell proliferative activity of 52-3 SN whether or not IL-4 was present. When 52-3 SN was tested on dextran-sulfate-activated B cells, IL-5 and BCAF activities were detected but only the IL-5 activity was neutralized by monoclonal antibody NC17. These results demonstrate that (i) BCAF-containing SN can induce proliferation of resting B cells independently of IL-4 and IL-5, and (ii) IL-4, but not IL-5, can act synergistically with BCAF to induce B cell proliferation. 相似文献
15.
Hitoshi Shibata Hideo Ochiai Tetsufumi Kawashima Tadayoshi Okamoto Isamu Inamura 《BBA》1986,852(2-3):175-182
By mixing chlorophyll (Chl) a or b with a dense bovine serum albumin solution, the water-soluble Chl-bovine serum albumin complexes were prepared. These complexes, eluted near the void volume on a gel filtration, were separated well from unreacted bovine serum albumin, indicating an aggregation of such molecules in the complexes. Preparation of chlorophyllide (Chlide) a- or Chlide b-bovine serum albumin complex was unsuccessful, while the phytol-, and β-carotene-bovine serum albumin complexes could be obtained. Chls in the Chl-bovine serum albumin complexes had the following characteristics. (i) Main absorption peak of Chl a or b in the red region occurred at 675 nm or 652 nm, respectively. The Chl a-bovine serum albumin complex having absorption peak at 740 nm was also prepared. As compared with the stabilities of Chl a and b in Triton X-100. (ii) Both Chls in the bovine serum albumin-complexes were stable against oxidative stresses, such as photobleaching, Fenton reagent, peroxidase-H2O2 system. But (iii) they were easily hydrolyzed by chlorophyllase. These properties of Chls in the bovine serum albumin-complexes were similar to those of Chls in the isolated light-harvesting Chl a/b protein complex. A possible localization of Chls within the bovine serum albumin complexes was suggested that the porphyrin moiety of Chl was buried in bovine serum albumin; however, the hydrophilic edge of porphyrin ring, adjacent to the phytol group, occurred in the hydrophilic region of a bovine serum albumin molecule. 相似文献
16.
Tatsuo Nakahara Takashi Matsumoto Makoto Hirano Hideyuki Uchimura Hideyasu Yokoo Kaoru Nakamura Kenji Ishibashi Hitoshi Hirano 《Peptides》1985,6(6):1093-1099
Acute and chronic effects of γ-butyrolactone-γ-carbonyl-histidyl-prolinamide (DN-1417) were investigated on motor activity, dopamine (DA) metabolites and DA receptors in various brain regions of rats. The motor activity, as measured with Automex recorder, was enhanced after a single injection with DN-1417 (20 mg/kg, IP), and the motor stimulating action persisted during 21 daily injections. Acute DN-1417 elevated both homovanillic acid (HVA) and 3,4-dihydroxyphenylacetic acid (DOPAC) levels in 7 brain regions, prefrontal cortex polar, medial and lateral fields, nucleus accumbens, olfactory tubercles, amygdala and striatum. After chronic treatment for 7 days, the acute effect of DN-1417 on DA metabolites disappeared in all regions except for the striatum in which DN-1417 still increased HVA and DOPAC. The response of striatal DA metabolites was also observed after chronic treatment for 21 days. Chronic DN-1417 produced no significant change in 3H-spiperone binding in the prefrontal cortex, nucleus accumbens, olfactory tubercles and striatum, while striatal 3H-DA binding displaced by 30 nM spiperone was enhanced after chronic treatment. These results indicate that DN-1417 interacts with mesocortical, mesolimbic and nigrostriatal DA systems in the different modes of action. The lack of tolerance to motor hyperactivity, however, raises the question as to whether DN-1417-induced hyperactivity may be mediated by the activation of mesolimbic DA neurons. The involvement of nigrostriatal neurons in DN-1417-induced motor hyperactivity is suggested. 相似文献
17.
Intensely pigmented and spherical vesicles (anthocyanoplasts) were found in anthocyanin-containing cells of sweet potato (Ipomoea batatas) suspension cultures. Anthocyanin synthesis began to first occur 24–48 h after exposure to light, and then numerous small red vesicles were detected under a microscope. The frequency of anthocyanoplast-containing cells rapidly increased to finally about 80% of the total cultured cells after 5 days of irradiation. Fully developed anthocyanoplasts reached 10–15 m in diameter. On the other hand, neither anthocyanin synthesis nor development of anthocyanoplasts was induced in the dark-cultured cells. 2,4-D also inhibited anthocyanin synthesis and development of these vesicles. The results suggest that anthocyanoplasts might be a site of anthocyanin synthesis and/or accumulation.Abbreviation 2,4-D
2,4-dichlorophenoxyacetic acid 相似文献
18.
Dr. Gerard J. McGarrity Lindsay Gamon Theodor Steiner Joseph Tully Hitoshi Kotani 《Current microbiology》1985,12(2):107-112
Uridine phosphorylase activity has been used to detect mycoplasmas in cell cultures by measuring formation of14C-uracil from14C-uridine. In this report we show that all species ofMycoplasma, Acholeplasma, andUreaplasma tested exhibited uridine phorphorylase activity. Among the genusSpiroplasma, serogroups I-1, I-3, I-5, I-7, I-8, IV, XIII, and XIV lacked uridine phosphorylase activity.Present address: Ciba-Geigy, Basel, Switzerland. 相似文献
19.
Hitoshi Sato Yuichi Sugiyama Yasufumi Sawada Tatsuji Iga Manabu Hanano 《Life sciences》1984,35(10):1051-1059
A rapid radioreceptor assay for measuring ß-endorphin (ß-EP) in unextracted serum has been developed. The method is based upon the inhibition by ß-EP of 3H-naloxone binding to the specific receptors on rat brain membranes, prepared in a stable form of pellets. Effect of serum on the assay was minimized by adding pooled serum to the equal dilution of total serum in the assay mixture. Pharmacokinetic analysis of pharmacologically active ß-EP equivalents (ß-EP eq.) in rats was performed using this method. The serum disappearance of ß-EP eq. after iv administration followed a biexponential decline and pharmacokinetic parameters were calculated by a two-compartment open model. The half-lives of α-phase and ß-phase were 2.6 ± 0.5 min and 6.2 ± 1.6 hr (mean ± SE; n=6), respectively. The volume of the central compartment (V1) and that of steady-state (Vdss) were 67 ± 16 and 480 ± 75 ml/kg (mean ± SE; n=6), respectively. The total body serum clearance (CLtot) was 2.1 ± 0.9 ml/min/kg (mean ± SE; n=6). The serum disappearance curve of ß-EP eq. obtained in the present study was similar to that previously reported by Houghten et al. (Proc. Natl. Acad. Sci. U.S.A. , 4588–4591 (1980)), in which the disapperance of total radioactivity of tritiated ß-EP in rats was examined. 相似文献
20.
On the basis of an artificial defoliation experiment, a new growth model of soybean was formulated through a modification
of Rudd's (1980) model with regard to his equations for dry matter allocation. Compensatory growth for leaf damage was modelled
by a single process in which the dry matter allocation changes dynamically according to the severity of leaf damage. The sums
of squared differences between simulations and experimental soybean yields were much smaller in our modified model than in
Rudd's original model. The modified model gave a better simulation of yield loss due to defoliation that varied in time and
intensity. The relationship between various times and intensities of defoliation and yield loss was shown, which is essential
for establishing the dynamic economic injury level in IPM. 相似文献