全文获取类型
收费全文 | 1212篇 |
免费 | 98篇 |
出版年
2021年 | 7篇 |
2019年 | 8篇 |
2018年 | 8篇 |
2017年 | 8篇 |
2016年 | 22篇 |
2015年 | 37篇 |
2014年 | 28篇 |
2013年 | 49篇 |
2012年 | 51篇 |
2011年 | 43篇 |
2010年 | 34篇 |
2009年 | 47篇 |
2008年 | 49篇 |
2007年 | 70篇 |
2006年 | 55篇 |
2005年 | 50篇 |
2004年 | 60篇 |
2003年 | 45篇 |
2002年 | 41篇 |
2001年 | 30篇 |
2000年 | 48篇 |
1999年 | 40篇 |
1998年 | 12篇 |
1997年 | 16篇 |
1996年 | 13篇 |
1995年 | 12篇 |
1994年 | 7篇 |
1993年 | 10篇 |
1992年 | 26篇 |
1991年 | 29篇 |
1990年 | 33篇 |
1989年 | 25篇 |
1988年 | 19篇 |
1987年 | 28篇 |
1986年 | 23篇 |
1985年 | 23篇 |
1984年 | 27篇 |
1983年 | 14篇 |
1982年 | 12篇 |
1981年 | 10篇 |
1979年 | 22篇 |
1978年 | 9篇 |
1977年 | 13篇 |
1975年 | 9篇 |
1974年 | 14篇 |
1973年 | 11篇 |
1972年 | 6篇 |
1971年 | 6篇 |
1970年 | 13篇 |
1968年 | 6篇 |
排序方式: 共有1310条查询结果,搜索用时 15 毫秒
41.
K Matsuyama K Moriwaki S Iida Y Itoh M Gomi S Kawamura S Tarui 《Endocrinologia japonica》1984,31(4):443-449
An extract of porcine thyroid gland in 0.1 N acetic acid exerted dose-dependent potentiation of ACTH-induced corticosterone production in isolated rat adrenal cells. The extract by itself manifested no steroidogenic activity. Upon gel-filtration of the extract, potentiating activities were demonstrated in three main peaks with molecular weights of about 10,000, 5,000 and 2,000. These findings indicate the presence of heterogeneous forms of ACTH-potentiating factors in the thyroid. Significant enhancement of ACTH-induced steroidogenesis was readily apparent with three gel-filtration fractions at a lower concentration of ACTH (4.75 pM). At this concentration, dose-dependent potentiation was observed with these three fractions. Enhanced corticosterone production responses by cells preincubated with the thyroid extract were observed and the results indicated the existence of potentiating mechanisms other than inhibition of ACTH proteolysis. The lack of T4, T3 and thyroglobulin in this activity suggests that the activity resides in other constituents of the thyroid. 相似文献
42.
The constituents of the steam volatile oils from two kinds of Allium fistulosum, A. fistulosum var. caespitosum and A. chinense, have been investigated by GC and spectral techniques (IR, UV, GC/MS, 1H NMR and 13C NMR). The compounds identified from the neutral fraction of each volatile oil included sulphides, thiolanes, alcohols, aldehydes, ketones, furanones and others. Among the sulphur compounds, dipropyl disulphide comprised ca 28% of A. fistulosum oil, ca 23% of A. fistulosum var. caespitosum oil and ca 30% of A. chinense oil. A. fistulosum oil was characterized by a large quantity of tridecan-2-one (ca 52%) and 2,3-dihydro-2-octyl-5-methylfuran-3-one (ca 16%). Also, a large amount of 2,3-dihydro-2-hexyl-5-methylfuran-3-one (ca 20%) was isolated from A. chinense oil. 相似文献
43.
Complement-dependent cytotoxicity of sera obtained from subacute sclerosing panencephalitis patients 总被引:1,自引:0,他引:1
Human lymphoid cells (NC-37) persistently infected with either measles virus (Schwarz and TYCSA strains) or subacute sclerosing panencephalitis (SSPE) virus (Halle and Mantooth strains) were destroyed in the presence of complement by anti-measles sera as well as by sera from SSPE patients. The cytotoxic activity was demonstrated in both IgG and IgM fractions of measles convalescent sera, but only in IgG fraction of SSPE sera. Measles convalescent sera completely lost the cytotoxic activity to all the cell lines, when absorbed with any one of the cell lines, indicating that the viral surface antigens of these cell lines infected with measles or SSPE virus are identical. On the other hand, the cytotoxic activity of SSPE sera could not be readily absorbed with these cells. Thus, the affinity of SSPE sera for the viral surface antigens might be lower than that of measles convalescent sera. 相似文献
44.
Summary Processes in the development of intestinal metaplasia of the stomach were investigated from the morphological and histochemical approaches using light and electron microscopic techniques. The specimens taken from 38 gastric carcinomas and 15 gastric and/or duodenal ulcers were subjected to this study. Morphological appearances of the intestinal metaplasia observed in routine examination with hematoxylin and eosin staining was able to be divided into complete and incomplete metaplasia by the light and electron microscopic histochemical stainings of the mucosubstances. The columnar cells at the area of the incomplete metaplasia had both the properties of the intestinal epithelia and the gastric foveolar epithelia. The incomplete as well as the complete metaplasia arose from the generative cells at the isthmus of the gland. The generative cells, however, sometimes gradually transformed to produce the complete metaplastic cells. The two processes of the development of the intestinal metaplasia were proposed and discussed. 相似文献
45.
Forskolin, a unique diterpene which directly activates the adenylate cyclase, stimulated production of both cyclic AMP and corticosterone in isolated rat adrenal cells, in vitro. This agent also potentiated the action of adrenocorticotropin and/or cholera toxin on cyclic AMP production and steroidogenesis at lower concentrations. It augmented both an early (cyclic AMP production) and a late (steroidogenesis) action of the hormone in the adrenal gland. 相似文献
46.
Hideyo Suzuki Kuo-Hsiung Lee Mitsumasa Haruna Toshiyuki Iida Kazuo Ito Huan-Chang Huang 《Phytochemistry》1982,21(7):1824-1825
A new lignan, (+)-aretigenin has been isolated from the roots of Wikstroemia indica (Nan-Ling-Jao-Hua) and identified as 8(R) 8′(S)-4′-hydroxy-3, 4,3′-trimethoxylignan-olid (9, 9′) on the basis of spectral evidence as well as a direct comparison with its enantiomer, (?)-arctigenin. 相似文献
47.
Summary Comparative restriction cleavage analysis of the genomes of bacteriophage P7, of several recombinant phages between P7 and P1, and of bacteriophage P1 allowed to draw PstI, BglII, BamHI and HindIII cleavage maps of all genomes studied. The data obtained complement Yun and Vapnek's (1977) conclusions with regard to areas of major nonhomology based on electron microscopical heteroduplex analysis and they identify several additional minor differences between P1 and P7. The use of hybrid phage strains allowed to locate the genes for particular functions on the physical genome map.Abbreviations Cm
chloramphenicol
- Ap
ampicillin
- bp
base pairs
- kb
kilo-base pairs 相似文献
48.
Jean T. Walker Shigeru Iida Donald H. Walker Jr. 《Molecular & general genetics : MGG》1979,167(3):341-344
Summary Use of restriction endonucleases BglII, EcoRI, BamHI, and HindIII, has established that in small-headed (PIS) virions of coliphage P1, as a population, the entire genome found in big-headed (P1B) virions is represented. In addition, the origin and direction of DNA packaging are identical in P1S and P1B virions. 相似文献
49.
Fat cell TSH receptor-related antibodies were detected by immunoprecipitation of 125I-TSH-receptor complexes and the nature of the antibodies was analyzed. To 125I-TSH prebound to Triton-solubilized receptors from guinea pig fat tissues, 50 micrograms of immunoglobulin G (IgG) was added and precipitation was effected by the addition of antihuman IgG. Immunoprecipitation values in 13 patients with Graves' disease were significantly (p less than 0.05) higher than those in 11 normal subjects. No significant increase in the values was seen in 8 patients with Hashimoto's disease. No correlation was observed between immunoprecipitation values and titers of antimicrosomal and antithyroglobulin antibodies. Neither was there any correlation between the values and TSH-binding inhibitor immunoglobulins (TBII) detected by the radioreceptor assay. The IgG fractions positive for the immunoprecipitation antibody were found to be poor human thyroid stimulators (HTS) relative to their TBII activities. And a highly significant correlation was observed between TBII and HTS activities among IgGs without detectable antibody by immunoprecipitation (r=0.907; p less than 0.005; n=7). These findings 1) demonstrate that immunoprecipitation assay using fat cell TSH receptor may detect TSH receptor-related antibodies different from TBII in patients with Graves' disease and 2) suggest the antibodies may recognize determinants on the receptor or its vicinity that do not participate in the binding of TSH or thyroid stimulating antibody, and may interfere with thyroidal response to these stimulators. 相似文献
50.
An improved approach for transformation of plant cells by microinjection: molecular and genetic analysis 总被引:4,自引:0,他引:4
Martin Schnorf Gabriele Neuhaus-Url Alessandro Galli Shigeru Iida Ingo Potrykus Gunther Neuhaus 《Transgenic research》1991,1(1):23-30
A new culture method for the injection of tobacco mesophyll protoplasts has been established. The protoplasts are embedded
in a thin layer of alginate and are nourished from the medium in the underlying basislayer. In the alginate layer the protoplasts
regenerate to calli at a frequency of up to 80%. Embedded protoplasts can be selected either with 50 mg l−1 kanamycin or 5 mg l−1 paromomycin. Single resistant cells can be recovered from about 10 000 sensitive cells in one alginate layer. Injection of
theneo gene (coding for neomycin phosphotransferase II) into protoplast derived single cells in the alginate layer results in kanamycin
resistant colonies that can be regenerated to mature plants. These plants express the neomycin phosphotransferase as shown
by enzyme activity assay. The integration of the transgene into the plant genome could be proved by Southern hybridization
to high molecular weight DNA. With this culture method 100 cells can be injected per hour. Transformation frequencies range
from 2 to 20%. In crossing experiments, it was shown that the foreign gene is transmitted to the next generation in a Mendelian
fashion. 相似文献