全文获取类型
收费全文 | 2695篇 |
免费 | 265篇 |
国内免费 | 1篇 |
出版年
2021年 | 40篇 |
2020年 | 40篇 |
2019年 | 69篇 |
2018年 | 64篇 |
2017年 | 27篇 |
2016年 | 45篇 |
2015年 | 83篇 |
2014年 | 110篇 |
2013年 | 145篇 |
2012年 | 155篇 |
2011年 | 145篇 |
2010年 | 99篇 |
2009年 | 72篇 |
2008年 | 132篇 |
2007年 | 146篇 |
2006年 | 156篇 |
2005年 | 143篇 |
2004年 | 106篇 |
2003年 | 131篇 |
2002年 | 125篇 |
2001年 | 45篇 |
2000年 | 26篇 |
1999年 | 50篇 |
1998年 | 52篇 |
1997年 | 24篇 |
1996年 | 37篇 |
1995年 | 34篇 |
1994年 | 25篇 |
1993年 | 33篇 |
1992年 | 32篇 |
1991年 | 27篇 |
1990年 | 22篇 |
1989年 | 33篇 |
1988年 | 25篇 |
1987年 | 24篇 |
1986年 | 21篇 |
1985年 | 26篇 |
1984年 | 14篇 |
1983年 | 17篇 |
1982年 | 20篇 |
1981年 | 16篇 |
1980年 | 22篇 |
1979年 | 18篇 |
1978年 | 14篇 |
1977年 | 20篇 |
1976年 | 19篇 |
1975年 | 16篇 |
1974年 | 15篇 |
1973年 | 17篇 |
1971年 | 16篇 |
排序方式: 共有2961条查询结果,搜索用时 15 毫秒
1.
2.
3.
4.
5.
Keith G. Danielson Janice E. Knepper Frances S. Kittrell Janet S. Butel Daniel Medina Elisa M. Durban 《In vitro cellular & developmental biology. Plant》1989,25(6):535-543
Summary Clonal populations were isolated from the mouse mammary cell line, COMMA-D, by transfection with a dominant-selectable gene,
pSV2Neo, which confers resistance to the antibiotic, G418. Seven of twenty-four clones isolated retained the ability of the
parental line to repopulate cleared mammary fat pads in vivo as ductal-alveolar hyperplasias. Two sublines designated CDNR2
and CDNR4 retained hyperplastic growth potential after multiple passages in vitro with low incidence of tumor formation. A
third subpopulation, CDNR1, contained a single integration site for the pSV2Neo plasmid indicating a bonafide clonal origin
for this subline. CDNR1 cells displayed heterogeneous growth phenotypes in vivo including hyperplasia, adenocarcinoma, and
bone formation. Functional differentiation of CDNR1 cells organized as alveolarlike structures in vivo or on floating collagen
gels in vitro was observed as determined by immunoperoxidase staining for the milk-specific protein, casein. Overall, the
results indicate that a subset of cells from the COMMA-D cell line may be functionally analogous to stem cells existing in
the mammary gland.
Supported by NCI research grants CA-38650, CA-33369, CA-39017, and CA-25215. 相似文献
6.
7.
A case of chromomycosis in which hyperthermia proved effective is reported. The patient was a 56-year-old male bean curd maker who, without any previous history of minor trauma, developed on the extensor side of the left upper arm an eczematous lesion that underwent gradual radial expansion. The lesion showed a well-defined, 7×10 cm infiltrated erythematous plaque with the central area healed and, at the upper and lower borders, adherent scales and crusts on the surface. Histological examination revealed granulomatous changes in the dermis, as well as sclerotic cells within giant cells and microabscesses. On culturing,Fonsecaea pedrosoi was isolated. The patient was treated with disposable chemical pocket warmers, which were secured over the lesion with a rather tight elastic bandage, so that they kept the affected area warm for 24 hours a day. After a month of such hyperthermic treatment, the erythema and infiltration had decreased considerably, and microscopic examination and culture of the crusts both yielded negative results. Examination of biopsy specimens of the lesion after the third month showed that it had cicatrized. The treatment was stopped after 4 months, and no relapse occurred. We also summarize the published results of local hyperthermic treatment of chromomycosis in Japan. 相似文献
8.
Alfalfa (Medicago sativa L. cv. Vernal) nodules were separatedinto host plant fractions and fractions of rhizobial originby differential centrifugation and sedimentation equilibriumcentrifugation. Both NAD- and NADP-linked isocitrate dehydrogenase(70%, 90%) and glutamate dehydrogenase activities (90%, 83%)were located primarily (percent total nodule activity) in thefractions of plant origin and their specific activities werehighest in the fractions of plant origin. More than 50% of thenodules' total activity of both glutamine synthetase and NAD-glutamatesynthase and greater than 90% of the total glutamate oxaloacetatetransaminase activity was located in plant fractions. However,the fractions of rhizobial origin had the highest specific activitiesof glutamine synthetase and glutamate synthase. (Received September 5, 1981; Accepted December 7, 1981) 相似文献
9.
The Escherichia coli dnaW mutation is an allele of the adk gene 总被引:3,自引:0,他引:3
Joan M. Henson Aleksandra Blinkowa James R. Walker 《Molecular & general genetics : MGG》1982,186(4):488-492
Summary A dnaW mutant, isolated on the basis of inability to effect conjugal DNA transfer at high temperature, has been shown by complementation and enzyme assay to be defective in the adk (adenylate kinase; EC 2.7.4.3) locus. The adk mutant, known to have reduced ATP concentration at the nonpermissive temperature (Cousin and Belaich 1966), was used to demonstrate a donor energy requirement for stable aggregate formation and for chromosome transfer in conjugation. 相似文献
10.