全文获取类型
收费全文 | 2338篇 |
免费 | 115篇 |
专业分类
2453篇 |
出版年
2022年 | 10篇 |
2021年 | 9篇 |
2020年 | 6篇 |
2019年 | 16篇 |
2018年 | 31篇 |
2017年 | 22篇 |
2016年 | 42篇 |
2015年 | 64篇 |
2014年 | 89篇 |
2013年 | 150篇 |
2012年 | 178篇 |
2011年 | 152篇 |
2010年 | 112篇 |
2009年 | 85篇 |
2008年 | 154篇 |
2007年 | 148篇 |
2006年 | 150篇 |
2005年 | 157篇 |
2004年 | 136篇 |
2003年 | 140篇 |
2002年 | 148篇 |
2001年 | 18篇 |
2000年 | 12篇 |
1999年 | 21篇 |
1998年 | 39篇 |
1997年 | 48篇 |
1996年 | 22篇 |
1995年 | 25篇 |
1994年 | 12篇 |
1993年 | 20篇 |
1992年 | 13篇 |
1991年 | 21篇 |
1990年 | 14篇 |
1989年 | 15篇 |
1988年 | 4篇 |
1987年 | 6篇 |
1986年 | 11篇 |
1985年 | 14篇 |
1984年 | 15篇 |
1983年 | 8篇 |
1982年 | 20篇 |
1981年 | 20篇 |
1980年 | 16篇 |
1979年 | 13篇 |
1978年 | 10篇 |
1977年 | 5篇 |
1976年 | 10篇 |
1975年 | 5篇 |
1973年 | 5篇 |
1971年 | 4篇 |
排序方式: 共有2453条查询结果,搜索用时 0 毫秒
1.
2.
Dr. Shigeru Sakiyama Yohko Nakamura Katsuo Tokunaga Hiroshi Takazawa Yoshinori Ohwaki Toshio Nagano 《Cell and tissue research》1989,258(2):225-231
Summary In-situ hybridization experiments have been performed using isoactin ( and )-specific riboprobes in various tissues of the rat and mouse. Distribution of the grains of actin mRNAs for both and types was similar throughout sections of the rat testis. Although both mRNAs were evenly distributed in the seminiferous tubule, extremely heavy labeling was observed in about 10% of the seminiferous tubules that could be identified as stage XII of spermatogenesis. At high magnification, grains of the mRNA were found in the cytoplasm of elongating spermatids and in the Sertoli cell cytoplasm at the adluminal side. Much higher density of the grains of mRNA was observed in the neck region of the spermatids at stage XII. Thus, the dense distribution of cytoskeletal actin mRNAs is stage-specific in the tubule during spermatogenesis in the rat. The high expression of both and actin mRNAs was also observed in the epithelial cells of the intestinal crypts. 相似文献
3.
T Nakahara A Shiraishi M Hirano T Matsumoto T Kuroki Y Tatebayashi T Tsutsumi K Nishiyama H Ooboshi K Nakamura 《Analytical biochemistry》1989,180(1):38-42
A highly sensitive assay for guanine was developed using high-performance liquid chromatography with electrochemical detection (ECD). Guanine was susceptible to the electrochemical oxidation, and ECD response was proportional to the amount of guanine in the range 0.25-4 pmol of guanine. The ECD of guanine was applicable to the analysis of nucleic acids. DNA and RNA were hydrolyzed in 0.03 and 3 M HCl, respectively, and guanine liberated from the nucleic acids was separated on a reverse-phase column and determined by ECD. The method allowed detection of 0.2 ng of calf thymus DNA or tRNA. An application of the method is shown for DNA and RNA assays in trichloroacetic acid extracts of rat adrenal and liver. 相似文献
4.
Tatsuo Nakahara Makoto Hirano Takashi Matsumoto Toshihide Kuroki Yoshinori Tatebayashi Tetsuyuki Tsutsumi Kouji Nishiyama Hiroaki Ooboshi Kaoru Nakamura Hiroshi Yao Akio Shiraishi Michinori Waki Hideyuki Uchimura 《Neurochemical research》1990,15(6):609-611
DNA and RNA contents in 20 brain regions or nuclei of the rat were determined by a highly sensitive method using high-performance liquid chromatography with electrochemical detection. The high DNA and RNA contents were found in the hypothalamic nuclei, especially the median eminence-arcuate nucleus. These results may be available for the preparation of nucleic acids as the regional control. 相似文献
5.
An efficient method, called the culture plate method, was devised for microinjection of foreign materials into nuclei of tomato callus cells. The culture plate method, used in this study, is advantageous because cells suitable for microinjection can be selected microscopically and the injected cells subsequently cultured in the same plate. With this microinjection system, some foreign materials were injected into nuclei of callus cells without causing detrimental effects. Kanamycin-resistant callus clones were obtained 1 month after injection from single cells whose nuclei were microinjected with a NPT II DNA fragment of the pE2KX plasmid. 相似文献
6.
A comparative study on immunosuppressive effects of cyclosporin A and FK 506 on peripheral blood lymphocytes in dogs 总被引:1,自引:0,他引:1
Kyoichi Takaori Yoshinori Nio Kazutomo Inoue Thein Tun Manaba Fukumoto Tohru Hashida Masato Yasuhara Ryohei Hori Takayoshi Tobe 《Biotherapy》1992,4(2):129-137
Immunosuppressive effects of cyclosporin A (CsA) and FK 506 (FK) on peripheral blood lymphocytes were studied in dogs in respect to mixed lymphocyte reaction, proliferative responses to recombinant interleukin-2 (rIL-2), phytohemagglutinin (PHA) and concanavalin-A (Con-A); phenotypes of OKIa1, CD3, CD8 and surface IgM; cytotoxic activity against xenogeneic tumor cells. CsA (2.0 or 5.0 mg/kg, intravenously) or FK (0.16 mg/kg, intramuscularly) was given to mongrel dogs every morning for serial 21 days. The blood concentrations of CsA, measured as trough levels by fluorescence polarization method, ranged from 37 to 350 ng/ml in dogs administered at 2.0 mg/kg and from 170 to 894 ng/ml in dogs administered at 5.0 mg/kg during treatment, respectively. In dogs treated with FK at a dose of 0.16 mg/kg, the drug concentrations in the plasma during treatment ranged from 0.16 to 1.8 ng/ml. Mixed lymphocyte reaction and proliferative responses to rIL-2, PHA and Con-A, which were declined by CsA, were not affected by FK. In contrast, the proportion of OKIa1+ cells was not affected by CsA, whereas FK decreased the proportion of OKIa1+ cells progressively during the course of treatment. Cytotoxic activity was suppressed by both CsA and FK. These results possibly indicate that CsA and FK exert their immunosuppressive effects via different mechanisms. 相似文献
7.
Formation of Nitrosylleghemoglobin in Nodules of Nitrate-Treated Cowpea and Pea Plants 总被引:1,自引:0,他引:1
The formation of nitrosylleghemoglobin (LbNO) was examined incowpea and pea nodules in relation to the inhibition of nitrogenfixation by nitrate. Leghemoglobin was of the ferrous type andwas mainly converted to LbNO in cowpea nodules when the acetylene-reducingactivity decreased to 45% of control values as a result of thesupply of nitrate. In nodules of nitrate-treated pea plants,leghemoglobin was also of the ferrous type and LbNO was a minorcomponent of leghemoglobin. The levels of LbNO isolated fromnodules corresponded to the levels of LbNO calculated from equilibriumconstants for LbNO and the concentration of nitrite in nodules.The dissociation rate constants for LbNO from both cowpea andpea were much smaller than those for LbO2 or LbCO, as is alsothe case in soybean. These results indicate that the inhibition of the functionsof leghemoglobin, due to the accumulation of LbNO, induces adecrease in nitrogen fixation in cowpea nodules, and that theinhibition of nitrogen fixation in pea nodules is not relatedto the formation of LbNO. (Received July 2, 1990; Accepted October 9, 1990) 相似文献
8.
Three germacrane-type sesquiterpenoids, (+)-germacrone-4,5-epoxide, germacrone and (+)-curdione were biotransformed by Aspergillus niger to give hydroxylated guaiane-type sesquiterpenoids together with allylic alcohols and spirolactone. 相似文献
9.
Summary A Na+-sensitive uptake of 3-O-methylglucose (3-O-MG), a nonmetabolized sugar, was characterized in frog skeletal muscle. A removal of Na+ from the bathing solution reduced 3-O-MG uptake, depending on the amount of Na+ removed. At a 3-O-MG concentration of 2mm, the Na+-sensitive component of uptake in Ringer's solution was estimated to be about 26% of the total uptake. The magnitude of Na+-sensitive component sigmoidally increased with an increase of 3-O-MG in bathing solution, whereas in Na+-free Ringer's solution the uptake was proportional to the concentration. The half saturation of the Na+-sensitive component was at a 3-O-MG concentration of about 13mm, and the Hill coefficient was 1.4 to 1.6. Phlorizin (5mm), a potent inhibitor specific for Na+-coupled glucose transport, reduced the uptake in a solution containing Na+ to the level in Na+-free Ringer's solution. Glucose of concentrations higher than 20mm suppressed 3-O-MG uptake to a level slightly lower than that in Na+-free Ringer's solution. These observations indicate that there are Na+-coupled sugar transport systems in frog skeletal muscle which are shared by both glucose and 3-O-MG. 相似文献
10.
Takashi Tsuchiya Atsushi Ichimura Yoshinori Nagai 《Cell biochemistry and biophysics》1987,11(1):109-122
Correlations in the baker map and the tent map as examples of one-dimensional, fully developed chaos are considered. It is
shown, utilizing symbolic dynamical systems derived from these maps, that the vanishing second-order correlation function
is not sufficient to guarantee uncorrelatedness. Importance of the higher-order, especially third-order, correlation functions
is emphasized for chaotic systems. In search of the quantities that grasp correlational behaviors as a whole in chaotic systems,
it is proposed to use the fixed-separation correlation integral, which is a modified quantity of the usual correlation integral
devised to calculate the fractal dimension of strange attractors, for these maps. It is shown that the new quantity contains
all the even-number orders of autocorrelation function that are commonly considered. 相似文献