全文获取类型
收费全文 | 5375篇 |
免费 | 309篇 |
国内免费 | 2篇 |
出版年
2022年 | 17篇 |
2021年 | 49篇 |
2020年 | 27篇 |
2019年 | 48篇 |
2018年 | 62篇 |
2017年 | 34篇 |
2016年 | 82篇 |
2015年 | 126篇 |
2014年 | 137篇 |
2013年 | 407篇 |
2012年 | 265篇 |
2011年 | 290篇 |
2010年 | 163篇 |
2009年 | 182篇 |
2008年 | 274篇 |
2007年 | 256篇 |
2006年 | 248篇 |
2005年 | 255篇 |
2004年 | 301篇 |
2003年 | 273篇 |
2002年 | 267篇 |
2001年 | 161篇 |
2000年 | 171篇 |
1999年 | 150篇 |
1998年 | 70篇 |
1997年 | 75篇 |
1996年 | 58篇 |
1995年 | 56篇 |
1994年 | 59篇 |
1993年 | 63篇 |
1992年 | 99篇 |
1991年 | 83篇 |
1990年 | 72篇 |
1989年 | 86篇 |
1988年 | 81篇 |
1987年 | 58篇 |
1986年 | 53篇 |
1985年 | 55篇 |
1984年 | 55篇 |
1983年 | 38篇 |
1982年 | 30篇 |
1981年 | 48篇 |
1980年 | 27篇 |
1979年 | 33篇 |
1978年 | 30篇 |
1977年 | 29篇 |
1976年 | 37篇 |
1975年 | 20篇 |
1973年 | 26篇 |
1971年 | 17篇 |
排序方式: 共有5686条查询结果,搜索用时 78 毫秒
101.
Mitsuo Matsuda Toshiya Nosaka Masaaki Sato Norio Ohshima 《European journal of applied physiology and occupational physiology》1993,66(2):122-126
To evaluate the effects of exercise on aortic wall elasticity and elastic components, young male rats underwent various exercise regimes for 16 weeks. In the exercised rats, the aortic incremental elastic modulus decreased significantly when under physiological strain. The aortic content of elastin increased significantly and the calcium content of elastin decreased significantly in the exercised group. The accumulated data from the exercised and sedentary groups revealed that the elastin calcium content was related positively to the incremental elastic modulus. We concluded that physical exercise from an early age decreases the calcium deposit in aortic wall elastin and that this effect probably produced in the exercised rats a distensible aorta. 相似文献
102.
Ken-ichiro Takamiya Yuzo Shioi Masakazu Morita Hiroyuki Arata Minoru Shimizu Michio Doi 《Archives of microbiology》1993,159(1):51-56
Characteristics and occurrence of cytochrome c-552 from an aerobic photosynthetic bacterium, Roseobacter denitrificans, were described.Relative molecular mass of the cytrochrome was 13.5 kDa on sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and 15,000 by gel filtration. This cytochrome was a acidic protein having a pI of 5.6 and Em was +215 mV at pH 7.0. Absorption peaks were at 278, 408 and 524 nm in the oxidized form and 416, 523 and 552 nm in the reduced form.Amino acid composition and N-terminal amino acid sequence of cytochrome c-552 determined for 24 residues had low similarities to those of cytochrome c-551 of this bacterium, which is homologous to cytochrome c
2, although the physico-chemical properties of these two cytochromes were similar to each other.Cytochrome c-552 was maximally synthesized in the light under aerobic conditions but not in the dark. The synthesis also occurred in the presence of alternative acceptors such as trimethylamine N-oxide (TMAO) and nitrate under anaerobic conditions. Our results suggest that cytochrome c-552 is involved in TMAO respiration and denitrification in R. denitrificans, although the effect of light remains to be solved.Abbreviations Em
Midpoint redox potential
- PAGE
Polyacrylamide ge electrophoresis
- SDS-PAGE
Sodium dodecyl sulfate polyacrylamide gel electrophoresis
- TMAO
Trimethylamine N-oxide 相似文献
103.
Seiji Ichida Tetsuyuki Wada Satori Nakazaki Naruhisa Matsuda Hiroyuki Kishino Takafumi Akimoto 《Neurochemical research》1993,18(5):633-638
The characteristics of the specific bindings of [3H](+)PN200-110 (PN: L-type Ca channel antagonist) and [125I]-conotoxin G VI A (-CgTX: neuronal L-or N-type Ca channel antagonist) to crude membranes from undifferentiated neuroblastoma x glioma hybrid NG108-15 (NG108-15) cells and differentiated cells induced with dibutyryl cAMP (Bt2cAMP) were examined, because we have already observed that the magnitude and rate of KCL-stimulated45Ca uptake by NG108-15 cells increased progressively during differentiation of the cells induced with Bt2cAMP (unpublished results). The specific binding of [3H](+)PN to these crude membranes was saturable at various concentrations of 2.5–5.0 nM [3H](+)PN. Scatchard analysis showed that the specific binding of [3H](+)PN at equilibrium was significantly increased after differentiation of the NG108-15 cells with Bt2cAMP, but that the apparent Kd value for the specific binding of [3H](+)PN was not influenced by treatment with Bt2cAMP. The specific binding of [3H](+)PN to crude membranes from Bt2cAMP-treated NG108-15 cells was inhibited by a calcium agonist and antagonists, the order of their inhibitory potencies being (+)PN>nitrendipine>(–)PNBay K 8644diltiazem = verapamil. Thus, PNs showed significant stereoselective inhibition of the specific binding of [3H(+)PN. On the other hand, [125I]-CgTX at concentrations of 0.075–0.6 nM showed scarcely any specific binding to these crude membranes, although at 0.6 nM it showed specific binding to crude membranes from rat brain in the same experimental conditions. These results suggest that the increase in magnitude or rate of KCl-stimulated45Ca uptake during differentiation of NG108-15 cells is partially due to quantitative alteration of voltage-sensitive Ca channels in the cells, and that there are scarcely any specific binding sites for [125I]-CgTX on Bt2cAMP-treated or untreated NG108-15 cells. 相似文献
104.
Yukie Takahashi Masako Sohnaka Minoru Nakao Kenji Miyamoto Masahito Fukunaga 《Microbiology and immunology》1993,37(9):721-727
Thirty-two Borrelia isolates were obtained from the adult stage of ixodid ticks, Ixodes ovatus, collected in various localities in Japan. Borrelial isolates were cultivated and analyzed by polyacrylamide gel electrophoresis, with monoclonal antibodies, by pulsed field gel electrophoresis, and by genomic Southern hybridization. All borrelial isolates showed similar protein profiles and monoclonal antibody reactivities, while plasmid profiles were rather diverse. Genomic hybridization using rRNA gene probes demonstrated the genetic similarities of those isolates. We found no significant differences among the borrelial isolates tested, and the restriction fragment length polymorphism patterns of I. ovatus isolates were quite distinct from those of borrelial strains associated with Lyme disease. Therefore, the isolates of Borrelia obtained from I. ovatus were thought to fall into different genospecies. 相似文献
105.
The analysis of major satellite sequence differences between Mus spretus and laboratory mice provides a robust method for analyzing the centromere location for the genetic maps of each mouse chromosome. Fluorescence in situ hybridization (FISH) of a genomic probe, pMR196, for the laboratory mouse major satellite sequences was used to identify C57BL/6Ros (B6) pericentromeric heterochromatin in progeny of reciprocal backcross matings. These included 80 (B6xM. spretus)F1xM. spretus progeny (BSS) and 70 (B6xM. spretus)F1xB6 (BSB) progeny. FISH analysis of pericentromeric heterochromatin was conducted on the same metaphase spreads that were karyotypically analyzed for chromosomespecific banding patterns. Analysis of chromosomal segregation suggested that there was not primary deviation from random assortment during meiosis in the interspecific hybrid female, because nearly all of the 190 pair-wise comparisons did not deviate from expected and because there was no consistent pattern of deviation of the same chromosomes in the reciprocal backcross progeny from similar (C57BL/6xM. spretus)F1 hybrid females. These results affirm the value of using the major satellite to genetically mark pericentromeric heterochromatin in the analysis of the segregation and assortment of centromeres in Mus interspecific crosses. 相似文献
106.
Susumu Ikegami Yasunori Ooe Takahiko Shimizu Toshihiko Kasahara Tatsuhiko Tsuruta Masako Kijima Minoru Yoshida Teruhiko Beppu 《Development genes and evolution》1993,202(3):144-151
Summary External application of 10 rig/ml (R)-trichostatin A (TSA), a potent and specific inhibitor of mammalian histone deacetylase, to the embryo of the starfish Asterina pectinifera inhibited development during the early gastrula stage before formation of mesenchyme cells. The TSA-sensitive period was limited to the mid-blastula stage before hatching. The pulse-chase experiment clearly demonstrated that TSA induced an accumulation of acetylated histone species in blastulae through inhibition of historic deacetylation. Similar blockage of development at the early gastrula stage was observed with n-butyrate, which has been known as a weak inhibitor of historic deacetylase. These results suggest an intimate role for historic acetylation-deacetylation equilibria in starfish development.
Correspondence to: S. Ikegami 相似文献
107.
Kajiwara Hideyuki; Okuyama Tsuneo; Fukuda Minoru; Hirano Hisashi; Oono Kiyoharu 《Plant & cell physiology》1992,33(1):27-32
A protein with relatively high homology in its N-terminal aminoacid sequence to animal parvalbumin and oncomodulin has beenidentified in leaves of rice (Oryza sativa L.). The PV-likeprotein has a relative molecular mass of 27,000 and an isoelectricpoint of 5.0. This protein was partially purified by ion-exchangechromatography, and the purified protein was found to have Ca2+-bindingactivity in a microscale Ca2+-binding assay. Furthermore, anantiserum raised against a synthetic oligopeptide based on theN-terminal amino acid sequence of this protein cross-reactedwith protein not only from rice but also from other monocotyledonousplants. (Received October 17, 1990; Accepted October 17, 1991) 相似文献
108.
Minoru Murai 《Ethology : formerly Zeitschrift fur Tierpsychologie》1992,92(2):124-134
The male of Uca (Deltuca) arcuata, a vertical claw-waving fiddler in the Indo-Pacific, is used to court females by approaching them from his burrow or while wandering. Differences in the rate of encounters with females between burrow-holding males and burrowless wandering males are found not to be significant. Burrow-holding males less often cause displacement of wandering by females than wandering males do. Wandering of females caused by wandering males occurs as often as wandering of males caused by other males. Thus, burrow-holding males tend not to reduce the number of their potential mates in the neighborhood. Burrow dwelling males are apt to start wandering after decreased encounters with females. Wandering males experience more interactions with other males than burrow-holding males do. Most wandering males that displace burrow owners descend the burrows one or more times after displacing the owners. The extra fighting for temporary burrows is responsible for no increase of the encounter rate with females during wandering. 相似文献
109.
S Ito A Iwasaki J Syundo Y Tamura S Kishi H Mori K Ii Y Matsuda N Katsunuma 《The journal of histochemistry and cytochemistry》1989,37(5):611-615
Human liver guanase was purified and a specific antibody against it was raised in rabbits. The antiserum formed a single precipitin line with human liver extract, and also completely inhibited the activity of the liver enzyme. An immunoblotting study showed that the antibody bound specifically to one band of protein with guanase activity and not to other proteins. Therefore, we concluded that this antiserum against the liver enzyme was suitable for use in immunohistochemical demonstration of guanase. In tissue sections, the immunohistochemical reaction with this antibody was positive in the same locations as the histochemical guanase reaction with DAB (3,3'-diaminobenzidine tetrahydrochloride). 相似文献
110.
Three kinds of ATP analogues were synthesized. These ATP analogues can be classified into two conformations, i.e. syn and anti forms with respect to the N-glycosidic bond between adenine and ribose groups of ATP. 3'-O-(N-Methylanthraniloyl)-2-azidoadenosine 5'-triphosphate (MantN2(3)ATP) is recognized as the anti form, as ATP, and the other two, 3'-O-(N-methylanthraniloyl)-8-azidoadenosine 5'-triphosphate (MantN8(3)ATP) and 1,N6-etheno-8-azidoadenosine 5'-triphosphate (epsilon N8(3)ATP) are both syn forms. Mant and etheno groups are both fluorescent which allows detection of their binding to proteins. The photochemical binding of azido groups in ATP analogues to the myosin active site, examined in the presence and absence of ATP, showed that all the analogues bound to the site of myosin ATPase. These analogues also acted as substrates of the ATPase and were hydrolyzed in the active site, as judged by competitive inhibition of the ATPase and by their ATPase activities. Of these analogues, MantN2(3)ATP is very similar to ATP in divalent-cation dependence of its hydrolysis rate and in its ability to trap ADP in the active site with vanadate, while the other two are different from ATP in these respects. The photochemical binding sites of ATP analogues were localized by gel electrophoresis of trypsinized myosin ATPase with photocross-linked ATP analogues and/or by isolating the modified peptides. MantN2(3)ATP was found in the 23-kDa fragment which has a structure common to ATP-binding proteins, i.e. Gly-Xaa-Xaa-Gly-Xaa-Gly-Lys-Thr. Mant N8(3)ATP was found in a region of the 20-kDa fragment where actin is reported to attach. 相似文献