全文获取类型
收费全文 | 1082篇 |
免费 | 104篇 |
国内免费 | 3篇 |
出版年
2021年 | 13篇 |
2020年 | 9篇 |
2019年 | 9篇 |
2018年 | 20篇 |
2017年 | 15篇 |
2016年 | 29篇 |
2015年 | 37篇 |
2014年 | 41篇 |
2013年 | 60篇 |
2012年 | 60篇 |
2011年 | 68篇 |
2010年 | 38篇 |
2009年 | 29篇 |
2008年 | 51篇 |
2007年 | 55篇 |
2006年 | 56篇 |
2005年 | 46篇 |
2004年 | 45篇 |
2003年 | 53篇 |
2002年 | 45篇 |
2001年 | 36篇 |
2000年 | 36篇 |
1999年 | 24篇 |
1998年 | 18篇 |
1997年 | 6篇 |
1996年 | 18篇 |
1995年 | 11篇 |
1994年 | 4篇 |
1993年 | 12篇 |
1992年 | 26篇 |
1991年 | 29篇 |
1990年 | 14篇 |
1989年 | 26篇 |
1988年 | 13篇 |
1987年 | 7篇 |
1986年 | 16篇 |
1985年 | 9篇 |
1984年 | 9篇 |
1983年 | 8篇 |
1982年 | 9篇 |
1981年 | 8篇 |
1980年 | 7篇 |
1979年 | 7篇 |
1978年 | 6篇 |
1974年 | 4篇 |
1971年 | 4篇 |
1969年 | 9篇 |
1968年 | 4篇 |
1967年 | 5篇 |
1966年 | 4篇 |
排序方式: 共有1189条查询结果,搜索用时 15 毫秒
991.
992.
Hiroko Shimomura Yutaka Sashida Hiroyuki Nakata Junichi Kawasaki Yoko Ito 《Phytochemistry》1982,21(9):2213-2215
The plant growth regulating substances, pimpinellin, isopimpinellin, bergapten, isobergapten, vaginidiol, sphondin, scopoletin, umbelliferone, ferulic 相似文献
993.
994.
Rat brain tryptophan 5-monooxygenase was activated by incubation with ATP, Mg2+, calmodulin, and micromolar concentrations of Ca2+. The activating activity was resolved into two distinct peaks upon gel filtration on Sepharose CL-6B: one, Ca2+-, calmodulin-dependent protein kinase, and the other, a heat-labile activator protein. The activator protein was purified to apparent homogeneity from rat brain by a procedure involving calmodulin-Sepharose 4B, Sephadex G-150, and phenyl-Sepharose CL-4B column chromatography. The molecular weight of the activator protein was determined to be 70,000 by sedimentation equilibrium and by gel filtration on Sephadex G-150. The protein gave a single band on sodium dodecyl sulfate-polyacrylamide gel electrophoresis, the molecular weight of which was estimated to be 35,000, indicating that the protein might be composed of two identical subunits. Analysis of cross-linked activator protein by sodium dodecyl sulfate-polyacrylamide gel electrophoresis also suggested that the protein might be a dimer of identical subunits. Some other molecular properties of the activator protein were: sedimentation coefficient, 4.3 S; Stokes radius, 3.6 nm; diffusion coefficient, 6.0 x 10(-7) cm2/s; frictional ratio, 1.32; and partial specific volume, 0.73 cm3/g. The activator protein activated tyrosine 5-monooxygenase as well as tryptophan 5-monooxygenase in the presence of ATP, Mg2+, Ca2+, calmodulin, and Ca2+-, calmodulin-dependent protein kinase. 相似文献
995.
Model calculations are presented for the several properties of the development of the retinotectal projection in amphibians and fishes, using the Gierer-Meinhardt equations. One of these properties is the maintenance of topographic mapping between the retina and the tectum during their development despite the fact that the two tissues grow in morphologically different ways. Another is the existence of a critical period, at which the coordinates of the retina with respect to the tectum are irrevocably determined. It is assumed that the connections between the retinal and the tectal cells are made on the correspondence of positional markers which are given as a form of the distribution of a specific activator, the dynamics of which is described by the Gierer-Meinhardt equations. The monotonic distributions of the activator and the existence of the critical period are shown by a computer simulation of the proliferating retina. Several changes of the retinotectal projection after surgical operations on the retina or the tectum are also explained.Some of the results in this paper were presented at the poster session of the 6th International Biophysics Congress in Kyoto 1978 相似文献
996.
Plasmid Control of 6-Aminohexanoic Acid Cyclic Dimer Degradation Enzymes of Flavobacterium sp. K172 下载免费PDF全文
Seiji Negoro Hideo Shinagawa Atsuo Nakata Shinichi Kinoshita Tomoya Hatozaki Hirosuke Okada 《Journal of bacteriology》1980,143(1):238-245
Flavobacterium sp. K172, which is able to grow on 6-aminohexanoic acid cyclic dimer as the sole source of carbon and nitrogen, and plasmid control of the responsible enzymes, 6-aminohexanoic acid cyclic dimer hydrolase and 6-aminohexanoic acid linear oligomer hydrolase, were studied. The wild strain of K172 harbors three kinds of plasmid, pOAD1 (26.2 megadaltons), pOAD2 (28.8 megadaltons), and pOAD3 (37.2 megadaltons). The wild strain K172 was readily cured of its ability to grow on the cyclic dimer by mitomycin C, and the cyclic dimer hydrolase could not be detected either as catalytic activity or by antibody precipitation. No reversion of the cured strains was detected. pOAD2 was not detected in every cured strain tested but was restored in a transformant. The transformant recovered both of the enzyme activities, and the cyclic dimer hydrolase of the transformant was immunologically identical with that of the wild strain. All of the strains tested, including the wild, cured, and transformant ones, possessed identical pOAD3 irrespective of the metabolizing activity. Some of the cured strains possessed pOAD1 identical with the wild strain, but the others harbored plasmids with partially altered structures which were likely to be derived from pOAD1 by genetic rearrangements such as deletion, insertion, or substitution. These results suggested that the genes of the enzymes were borne on pOAD2. 相似文献
997.
Sumio Iwai Teruyoshi Nagao Kazuo Nakata Nobumaro Kawashima Susumu Matsuvama 《Planta》1980,147(5):414-417
In the sexual interspecific cross, Nicotiana rustica L.xN. tabacum L., N. rustica can serve as the female but not as the male parent. By fusion of protoplasts, the barrier to fertilization was overcome and somatic hybrids containing N. tabacum cytoplasm were produced as shown by isoelectric focusing of the Fraction-1 protein (F-1-protein). All somatic hybrids displayed polypeptides of the large subunit of F-1 protein (which is coded by the chloroplast genome) characteristic of only one or the other parental species. Two hybrids had large subunits of the N. tabacum type and two hybrids had those of the N. rustica type. Three hybrids contained three smallsubunit polypeptides (coded by the nuclear genome), one being characteristic of N. rustica, one characteristic of N. tabacum, and one with an isoelectric point common to both species. A fourth hybrid contained only two small-subunit polypeptides of the N. tabacum type but in a F-1 protein macromolecule whose large subunits were of the N. rustica type. One somatic hybrid was self-fertile and its F2 progeny contained large- and small-subunit polypeptides indistinguishable in their isoelectric points from those in the parent F1 hybrid. All somatic hybrids showed an aneuploid chromosome number and morphological characteristics intermediate between those of N. rustica and N. tabacum. 相似文献
998.
Kudo M; Takayama E; Tashiro K; Fukamachi H; Nakata T; Tadakuma T; Kitajima K; Inoue Y; Shiokawa K 《Glycobiology》1998,8(8):771-777
Polysialic acid (polySia) is a carbohydrate structure found on neural cell
adhesion molecules (N-CAM). Two polysialyltransferases (polySiaTs) that
catalyze synthesis of polySia have been described, and designated
PST-1/PST/ST8SiaIV and STX/ST8SiaII. We cloned a polySiaT (xSTX) from a
nonmammalian vertebrate, Xenopus laevis . xSTX had 80% amino acid
similarity to the rat STX. This clone induced polySia expression when
transfected into polySia-negative COS-1 cells. Northern blot analysis of
whole embryos at different stages of development revealed that xSTX mRNA
was most abundantly expressed in premetamorphic stages. The relative level
of xSTX and N-CAM mRNAs was also examined and found to change in parallel
to the extent of polysialylation on N-CAM. In adult tissues, the expression
of xSTX mRNA was restricted to brain, eye and heart, which also expressed
polySia. These results suggest that xSTX is the major enzyme responsible
for the synthesis of polysialylated N-CAM in embryos at certain stages of
development and also in adult tissues.
相似文献
999.
A physical map of the mitochondrial genome was constructed for a male-sterile tomato, MSA1, which had been generated by an
asymmetric cell fusion between tomato (Lycopersicon esculentum) and wild potato (Solanum acaule). The entire genomic sequence of the MSA1 mitochondria (450 kb) was represented by five maps. Even if sequence duplications
were taken into consideration, at least two linkage groups (maps 1–4 and map 5) were necessary to show the overall genome.
The mitochondrial genome structure of MSA1 was also analyzed by comparing the Southern hybridization patterns of MSA1 and
its parents (tomato and wild potato). The mitochondrial genome of MSA1 consists of a complex mixture of the parental genomes
with at least 11 molecular recombination events.
Received: 23 February 1998 / Revision received: 2 March 1998 / Accepted: 14 March 1998 相似文献
1000.
Nigel G. Yoccoz Keisuke Nakata Nils Chr Stenseth Takashi Saitoh 《Population Ecology》1998,40(1):107-121
Until recently, most studies on microtines have focused on patterns in population dynamics or demography without providing
a quantitative assessment of the robustness of the inferred patterns as well as a link between demography and population dynamics.
Developments in statistical time-series analysis on the one hand and in capture-recapture statistical modelling on the other
hand, now allow for improved analyses. We review some of the recent developments in the capture-recapture statistical methodology
— restricting ourselves to methods most relevant to the demography of small mammals. A 5-years study of the gray-sided voleClethrionomys rufocanus in Hokkaido, Japan was used as an example to explore some models. We then provided a framework for further demographic analysis
of microtine populations, includingC. rufocanus. Investigating the relative importance of the different demographic parameters (e.g. survival, maturation, dispersal) will
require studies done on larger scale than is commonly done today, with more effort devoted to the low density phase. Special
emphasis is given to study-design, and to experimental designs tailored to the study of specific demographic mechanisms. 相似文献