全文获取类型
收费全文 | 6956篇 |
免费 | 458篇 |
国内免费 | 4篇 |
专业分类
7418篇 |
出版年
2022年 | 46篇 |
2021年 | 83篇 |
2020年 | 58篇 |
2019年 | 58篇 |
2018年 | 90篇 |
2017年 | 81篇 |
2016年 | 131篇 |
2015年 | 217篇 |
2014年 | 263篇 |
2013年 | 392篇 |
2012年 | 445篇 |
2011年 | 427篇 |
2010年 | 218篇 |
2009年 | 231篇 |
2008年 | 392篇 |
2007年 | 401篇 |
2006年 | 346篇 |
2005年 | 347篇 |
2004年 | 376篇 |
2003年 | 313篇 |
2002年 | 328篇 |
2001年 | 166篇 |
2000年 | 157篇 |
1999年 | 135篇 |
1998年 | 95篇 |
1997年 | 82篇 |
1996年 | 57篇 |
1995年 | 69篇 |
1994年 | 69篇 |
1993年 | 64篇 |
1992年 | 91篇 |
1991年 | 92篇 |
1990年 | 77篇 |
1989年 | 104篇 |
1988年 | 65篇 |
1987年 | 68篇 |
1986年 | 63篇 |
1985年 | 81篇 |
1984年 | 75篇 |
1983年 | 49篇 |
1982年 | 50篇 |
1981年 | 37篇 |
1979年 | 52篇 |
1978年 | 35篇 |
1977年 | 42篇 |
1976年 | 25篇 |
1975年 | 29篇 |
1974年 | 29篇 |
1973年 | 30篇 |
1972年 | 26篇 |
排序方式: 共有7418条查询结果,搜索用时 19 毫秒
61.
Repression by a differentiation-specific factor of the human cytomegalovirus enhancer. 总被引:5,自引:0,他引:5 下载免费PDF全文
T H Huang T Oka T Asai T Okada B W Merrills P N Gertson R H Whitson K Itakura 《Nucleic acids research》1996,24(9):1695-1701
We detected a novel nuclear protein, MRF, that binds to multiple sites on the modulator which is located upstream of the human cytomegalovirus major immediate early gene enhancer. The expression of MRF is differentiation specific; the DNA binding activity is present in nuclear extracts from undifferentiated Tera-2 and THP-1 cells, but significantly reduced after these cells are induced to differentiate. In undifferentiated cells the enhancer activity is repressed by the modulator and upon differentiation the enhancer becomes active. Competitive binding assays demonstrate that MRF requires the presence of multiple A+T stretches for binding to DNA, rather than binding to a specific DNA sequence. Mutations of these stretches in the modulator reduce the binding activity of MRF, as well as the repressing activity on the enhancer. These results suggest that MRF may act as a repressor of enhancer function. We propose that MRF binds over the entire modulator and exerts repressor activity. 相似文献
62.
Summary Normal skeletal and cardiac striated muscle from adult rats was incubated for the cytochemical detection of acid phosphatase activity with cerium as the capture metal. Results from these experiments show that normal striated muscle has a greater number of acid phosphatase-positive structures, which are presumed to be lysosomes, than has been indicated by several previous cytochemical studies.Supported in part by grants AI 17945 and HL 17747 from the United States Public Health Service, National Institutes of Health 相似文献
63.
Brooke EW Davies SG Mulvaney AW Okada M Pompeo F Sim E Vickers RJ Westwood IM 《Bioorganic & medicinal chemistry letters》2003,13(15):2527-2530
The synthesis and inhibitory activity of a series of 5-substituted-(1,1-dioxo-2,3-dihydro-1H-1 lambda(6)-benzo[e][1,2]thiazin-4-ylidene)-thiazolidine-2,4-dione derivatives as competitive inhibitors of recombinant bacterial arylamine-N-acetyltransferases (NATs) are described. The most potent NAT inhibitors are those that contain planar hydrophobic substituents on the sultam nitrogen. 相似文献
64.
Hidetatsu Outani Minoru Okada Akihiro Yamashita Kanako Nakagawa Hideki Yoshikawa Noriyuki Tsumaki 《PloS one》2013,8(10)
The repair of large cartilage defects with hyaline cartilage continues to be a challenging clinical issue. We recently reported that the forced expression of two reprogramming factors (c-Myc and Klf4) and one chondrogenic factor (SOX9) can induce chondrogenic cells from mouse dermal fibroblast culture without going through a pluripotent state. We here generated induced chondrogenic (iChon) cells from human dermal fibroblast (HDF) culture with the same factors. We developed a chondrocyte-specific COL11A2 promoter/enhancer lentiviral reporter vector to select iChon cells. The human iChon cells expressed marker genes for chondrocytes but not fibroblasts, and were derived from non-chondrogenic COL11A2-negative cells. The human iChon cells formed cartilage but not tumors in nude mice. This approach could lead to the preparation of cartilage directly from skin in human, without going through pluripotent stem cells. 相似文献
65.
OsWRKY28, a PAMP-responsive transrepressor, negatively regulates innate immune responses in rice against rice blast fungus 总被引:1,自引:0,他引:1
66.
Tadao Niijima Takashi Umeda Manabu Kuriyama Hiroyuki Ohmori Yohsuke Matsumura Tomoyasu Tsushima Toyoko Tanahashi Jun Yoshimoto Toshihiko Asahi Norimasa Ike Taiichiro Johsen Noritaka Ishido Naoki Mitsuhata Takeshi Uyama Hiroyoshi Tanaka Hideo Ueda Jisaburo Sakatoku Norio Yamamoto Kazuo Nagata Yukitoshi Fujita Masaaki Morioka Kazuo Kurokawa Susumu Kagawa Tomoyuki Ishibe Yasutoshi Himeno Toyofumi Ueda 《Cancer immunology, immunotherapy : CII》1989,30(2):81-85
Summary In order to examine its clinical efficacy, recombinant human interferon- (rIFN-) was instilled intravesically into 51 patients with superficial bladder cancer. Ten patients, who received intermittent intravesical instillation at a dose of (3–36) × 106 U rIFN- on days 1–3 every week, showed no response. Thirty-two patients received intravesical instillation at a dose of (3–36) × 106 U every day for 10–20 days. Eight patients showed partial response, indicating an efficacy rate of 25%. Nine patients received divided doses of 18 × 106 U twice a day every day for 10–20 days. Six patients showed partial response, indicating an efficacy rate of 67%. This value was significantly higher than that obtained by administering divided doses. The response to intravesical instillation therapy with rIFN- varies with treatment protocol. Frequent and longer exposure to rIFN- may induce better regression of superficial bladder cancer. Six incidences of side-effects were found in five cases (9.8%): pollakiuria in one, pain on micturition in two, fever in two, and eruption in one case. All of these side-effects were slight and reversible after drug withdrawal. Laboratory tests showed only a few changes with low severity. Thus, rIFN- is potentially a new drug for instillation therapy of superficial bladder cancer, in view of the absence of adverse effects. 相似文献
67.
Using gamma distribution and spatial autocorrelation, it was demonstrated that plant biomass per unit area of a pasture grazed by cattle exhibited two kinds of spatial heterogeneity: small-scale heterogeneity caused by grazing and large-scale heterogeneity caused by topography, land aspect, etc. For each of the 10 measurement times from May to August, 100 quadrats 50cm × 50cm were arranged along a straight line 50m long in a pasture, and the plants within the quadrats were harvested at the height of 3cm above the ground surface to measure the dry weight. The data were aggregated into frequency distributions, and gamma distribution and the parameter values were estimated. This analysis showed that with the progression of grazing the amount of biomass decreased and the degree of spatial heterogeneity in biomass, measured per 0.25m2, increased, and due to plant regrowth the trends were reversed. By rearranging the 100 biomass data in order of weight, it was suggested that plots with an extremely large biomass were not grazed by cattle and remained in the pasture. For the same data, variations of biomass along the straight line were divided into two parts based on the moving average: the spatial trend and the residuals which cannot be explained by the trend. In this analysis, 48–75% of the total spatial variation was explained by the trend along the straight line. Analysis using spatial autocorrelation for the actual biomass changes showed that the biomass changes within a range of about 10m on the straight line gave a positive correlation, which indicates a topographical trend in biomass. Spatial autocorrelation for residuals suggested that the spatial changes in biomass along the straight line followed a wave-like or checker-board pattern. Small-scale spatial heterogeneity in plant biomass may be caused by the uneven deposition of excreta by grazing animals, uneven use of the grassland by grazing animals, and uneven dispersal of plant seeds through faeces over the grassland. The possibility that such unevenness might accelerate energy flow in the grassland ecosystem and contribute to grassland sustainability is discussed. 相似文献
68.
Jiro?ManiwaEmail author Shunsuke?Izumi Naoki?Isobe Takato?Terada 《Reproductive biology and endocrinology : RB&E》2005,3(1):23
Background
The objective of this study was to identify substantially increased proteins in bovine cystic follicular fluid (FF) in order to clarify the pathology and etiology of bovine ovarian follicular cysts (BOFC). 相似文献69.
Hitomi Yatsuki Ken Higashimoto Kosuke Jozaki Kayoko Koide Junichiro Okada Yoriko Watanabe Nobuhiko Okamoto Yoshinobu Tsuno Yoko Yoshida Kazutoshi Ueda Kenji Shimizu Hirofumi Ohashi Tsunehiro Mukai Hidenobu Soejima 《Genes & genomics.》2013,35(2):141-147
Beckwith-Wiedemann syndrome (BWS) is an imprinting-related human disease that is characterized by macrosomia, macroglossia, abdominal wall defects, and variable minor features. BWS is caused by several genetic/epigenetic alterations, such as loss of methylation at KvDMR1, gain of methylation at H19-DMR, paternal uniparental disomy of chromosome 11, CDKN1C mutations, and structural abnormalities of chromosome 11. CDKN1C is an imprinted gene with maternal preferential expression, encoding for a cyclin-dependent kinase (CDK) inhibitor. Mutations in CDKN1C are found in 40 % of familial BWS cases with dominant maternal transmission and in ~5 % of sporadic cases. In this study, we searched for CDKN1C mutations in 37 BWS cases that had no evidence for other alterations. We found five mutations—four novel and one known—from a total of six patients. Four were maternally inherited and one was a de novo mutation. Two frame-shift mutations and one nonsense mutation abolished the QT domain, containing a PCNA-binding domain and a nuclear localization signal. Two missense mutations occurred in the CDK inhibitory domain, diminishing its inhibitory function. The above-mentioned mutations were predicted by in silico analysis to lead to loss of function; therefore, we strongly suspect that such anomalies are causative in the etiology of BWS. 相似文献
70.
Interleukin 1 alpha mRNA in virus-transformed T and B cells 总被引:2,自引:0,他引:2
T Noma T Nakamura M Maeda M Okada Y Taniguchi Y Tagaya Y Yaoita J Yodoi T Honjo 《Biochemical and biophysical research communications》1986,139(1):353-360
IL-1 alpha cDNA clone was isolated from a T cell line infected by the human T lymphotropic retrovirus type-I (HTLV-I/ATLV). We found significant amounts of mRNA hybridizing to IL-1 alpha cDNA not only in HTLV-I-transformed T cells but also in Epstein-Barr Virus-transformed B cells. A part of IL-2 receptor inducing activity in Adult T cell leukemia (ATL) cell line seems to be due to IL-1 alpha. 相似文献