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101.
Spatial structures of landforms as constants affecting vegetation patterns are discussed based on analyses of hilly land regions, mostly in the vicinity of Sendai, northeast Japan. The lower part of a hillslope is characterized by relatively active processes of soil erosion, landslides and slope failure. It supports a plant community different from that on the upper part of the hillslope. These two parts are termed the lower hillslope and the upper hillslope, respectively. The upper hillslope consists of valley heads with no stream water nor stream channels. Since a valley head is comprised of several micro-scale landform units, an upper hillslope can be subdivided into these landform units. Plant communities vary in their species compositions and structures as well as in some other ecological characteristics paralleling changes in their respective micro-scale landform units. However, the variations in species composition within upper hillslopes are not as extreme as those between the upper and lower hillslopes. xx]Papers presented at the Vth INTECOL Congress at YOKO-hama 1990. 相似文献
102.
103.
Masayuki Maki 《Journal of plant research》1993,106(2):181-186
Intrapopulation and interpopulation variations in floral sex ratio in hermaphrodites of gynodioeciousChionographis japonica var.kurohimensis (Liliaceae) were examined. The relative ratio of male flowers to total flowers (male and perfect flowers) decreased with
plant size, suggesting size-dependent gender modification. The relative ratio of male flowers per population-basis is negatively
correlated with the mean number of perfect flowers. Since the number of perfect flowers proportionally increased with plant
size, populations showing low maleness consist of relatively bigger plants and are considered to be in high-quality environment.
On the other hand, the relative ratio of male flowers per population basis is independent of female frequency in the population.
Plasticity in gender expression probably plays an important role of maintenance of gynodioecy inC. japonica var.kurohimensis. 相似文献
104.
Masayuki Takamiya 《Journal of plant research》1993,106(2):149-166
Karyomorphological comparisons were made of 16 native and cultivated species ofSelaginella in Japan. The somatic chromosome numbers are 2n=16 inS. boninensis; 2n=18 inS. doederleinii, S. helvetica, S. limbata, S. lutchuensis, S. nipponica, S. selaginoides, S. tama-montana, andS. uncinata; 2n=20 inS. biformis, S. involvens, S. moellendorffii, S. remotifolia, andS. tamariscina; 2n=30 inS. rossii; and 2n=32 inS. heterostachys. The interphase nuclei of all species examined are uniformly assigned to the simple chromocenter type. The metaphase karyotype
of 2n=16 (x=8) is 8 m (=median centromeric chromosomes)+8(st+t)(=subterminal and terminal). The group of the species having
2n=18 (x=9) is heterogeneous karyomorphologically: The karyotype ofS. nipponica is 2n=18=6 m+12(st+t),S. tama-montana 10 m+2 sm(=submedian)+6(st+t), andS. uncinata 6 m+7 sm+5(st+t). Although the remaining five species have the common karyotype 8 m+4 sm+6(st+t), the values of mean chromosome
length are variable. Another group of the specles having 2n=20 (x=10) is homogeneous, since all species have the same karyotypes
8 m+4 sm+8(st+t) and have similar chromosome size. The karyotype of 2n=30 is 12 m+6 sm+12(st+t) and is suggested to be a triploid
of x=10, and 2n=32=16m+16(st+t), a tetraploid of x=8. Thus, three kinds of basic chromosome numbers, x=8, 9, 10 are present
in JapaneseSelaginella examined, and their karyomorphological relationships are discussed. 相似文献
105.
Yoshihiro Izumi Kanji Ono Masayuki Takamiya Kiichi Fukui 《Journal of plant research》1993,106(4):319-325
Using cultured cells of the hornwortAnthoceros punctatus, the change in the relative chloroplast DNA content in each stage of chloroplast division was investigated to clarify the
relationship between the division cycle of a chloroplast and a cell nucleus. Samples of cultured cells were stained with 4′,6-diamidino-2-phenylindole
(DAPI) and then observed with an epifluorescence microscope and a chromosome image analyzing system (CHIAS). A chloropiast
in cultured cells duplicated DNA with an increase in size. When a chloroplast began to divide, it was constricted in the middle,
taking a dumbbell shape, and then divided into two daughter chloroplasts. In cultured cells of this species, the pattern of
quantitative change of chloroplast DNA, that is, the DNA replication pattern of chloroplasts, corresponded to that of cell
nuclear DNA in mitosis. 相似文献
106.
Masayuki Kakehashi 《Population Ecology》1996,38(2):203-210
The host-parasite or host-pathogen system was analyzed from dynamical and evolutionary viewpoints using simple mathematical models incorporating vertical transmission, immunity and its loss. We first analyzed a model without density regulation of host population. In the analysis on dynamics, the condition for the pathogen to work as a density regulating factor was obtained. In the analysis on evolution, criteria for the evolution of host and pathogen were proposed. These criteria implies that the evolution of hosts should result in an increase in infected host density, whereas the evolution of pathogens a decrease in susceptible host density. The direction of evolution at some parameters of host and that of pathogen were examined when the parameters were independently and freely changeable. Among the parameters, only reduction in additional mortality due to infection was the evolutionary trend common to both host and pathogen. In all the other parameters examined, trend of evolution predicted in host is reversed in pathogen. We then analyzed whether the obtained criteria still hold in models with density regulation of hosts. Using randomly generated parameter sets, we obtained the result that the criteria should hold very likely though they do not always hold. We discussed evolution of virulence when there is a constraint between the traits. 相似文献
107.
DNA immunization: Effects of vehicle and route of administration on the induction of protective antiviral immunity 总被引:2,自引:0,他引:2
Masayuki Yokoyama Jie Zhang J.Lindsay Whitton 《FEMS immunology and medical microbiology》1996,14(4):221-230
Abstract The effectiveness of DNA immunization has been demonstrated in several model systems, usually following intramuscular injection of DNA in saline, or topical administration to the skin. In this study we have compared DNA delivered by three routes (intramuscular, intravenous, and intraperitoneal) and, for each route, in two vehicles (cationic liposome complex and pH sensitive liposome). These two lipid vehicles were evaluated because they are frequently used in gene therapy studies, but their immunogenicity has not been extensively studied. Each of these six combinations has been evaluated not only by assay of marker gene expression in a variety of tissues, but also by measurement of biologically-relevant parameters of immunity induction of antibodies, cytotoxic T lymphocytes, and protection against viral challenge. By both criteria (marker gene expression and induced immunity), the outcomes vary markedly among the six combinations. The combination leading to maximal marker gene expression (DNA with cationic lipid, administered i.v.) also induces detectable antibodies and CTL, and is the only one of the six combinations to induce immune responses comparable to those seen following i.m. injection of DNA in saline. However, marker gene expression can be detected in other combinations in the absence of induced immunity thus the value of marker gene expression in predicting the protection induced by a microbial antigen is questionable suggesting that, when evaluating various promoter constructs, marker gene expression may not adequately replace the direct measurement of biological outcomes. 相似文献
108.
Photo-induced activation of cytochrome P450/reductase fusion enzyme coupled with spinach chloroplasts 总被引:1,自引:0,他引:1
Young-Sug Kim Masayuki Hara Kazunori Ikebukuro Jun Miyake Hideo Ohkawa Isao Karube 《Biotechnology Techniques》1996,10(10):717-720
Summary Photoactivation of cytochrome P450 monooxygenase was studied using a combination of spinach chloroplasts and yeast microsomes containing rat P4501A1/yeast reductase fusion enzyme. Under illumination, in the reaction mixture, NADP was reduced, transferring electrons to the P450/reductase fusion enzyme to convert 7-ethoxycoumarin to 7-hydroxycoumarin. 相似文献
109.
110.
Eight diatom species (Chaetoceros pseudocurvisetus Mang ., Stephanodiscus hantzschii Grun ., Skeletonema costatum ( Grev.) Cleve , Asterionella formosa Hass ., Thalassiosira nordenskioeldii Cleve , Detonula confervacea ( Cleve) Gran , Chaetoceros sp., and Nitzschia frigida Grun.) were isolated from various temperature environments ranging from temperate to the Arctic, and their growth responses to temperature were determined. Each species grew over a different temperature range. The lower and upper limits of each species varied from −1.8° to 20° C and from 2° to 30° C, respectively. The width of the growth range of each species. also varied from 3.8° to 25° C, and the growth of these species was observed, as a whole, between a wide temperature range from −1.8° to 30° C .
Within the growth temperature ranges, the growth rate of each species increased with temperature until reaching a maximum, which was followed by a steep decrease up to the upper limit of the growth range. As a result, each species showed a maximum rate at the temperature very near to the upper limit, which was generally higher than the isolation temperature. The specific growth rates were compared among the eight species. The interspecific maximum rate at each temperature exhibited an exponential increase with a Q10 = 1.48. The relative growth rates of each species were calculated by normalizing the specific growth rates with the interspecific maximum rate at each respective temperature. The higher relative growth rates tended to occur at the isolation temperature of each species, suggesting that temperature is a significant control on species distributions in nature . 相似文献
Within the growth temperature ranges, the growth rate of each species increased with temperature until reaching a maximum, which was followed by a steep decrease up to the upper limit of the growth range. As a result, each species showed a maximum rate at the temperature very near to the upper limit, which was generally higher than the isolation temperature. The specific growth rates were compared among the eight species. The interspecific maximum rate at each temperature exhibited an exponential increase with a Q