全文获取类型
收费全文 | 4663篇 |
免费 | 273篇 |
国内免费 | 2篇 |
出版年
2021年 | 52篇 |
2020年 | 22篇 |
2019年 | 33篇 |
2018年 | 46篇 |
2017年 | 56篇 |
2016年 | 80篇 |
2015年 | 135篇 |
2014年 | 164篇 |
2013年 | 347篇 |
2012年 | 241篇 |
2011年 | 222篇 |
2010年 | 157篇 |
2009年 | 177篇 |
2008年 | 284篇 |
2007年 | 273篇 |
2006年 | 295篇 |
2005年 | 282篇 |
2004年 | 283篇 |
2003年 | 238篇 |
2002年 | 223篇 |
2001年 | 115篇 |
2000年 | 97篇 |
1999年 | 97篇 |
1998年 | 50篇 |
1997年 | 48篇 |
1996年 | 48篇 |
1995年 | 40篇 |
1994年 | 53篇 |
1993年 | 42篇 |
1992年 | 70篇 |
1991年 | 61篇 |
1990年 | 56篇 |
1989年 | 53篇 |
1988年 | 51篇 |
1987年 | 44篇 |
1986年 | 31篇 |
1985年 | 36篇 |
1984年 | 30篇 |
1983年 | 24篇 |
1982年 | 36篇 |
1981年 | 29篇 |
1980年 | 14篇 |
1979年 | 26篇 |
1978年 | 20篇 |
1977年 | 11篇 |
1976年 | 15篇 |
1975年 | 15篇 |
1974年 | 24篇 |
1971年 | 11篇 |
1968年 | 14篇 |
排序方式: 共有4938条查询结果,搜索用时 31 毫秒
1.
Masayo Suzuki Hiroyuki Ishida Yukimasa Shiotsu Taisuke Nakata Shiro Akinaga Shigemitsu Takashima Toshiaki Utsumi Toshiaki Saeki Nobuhiro Harada 《The Journal of steroid biochemistry and molecular biology》2009,113(3-5):195-201
In order to evaluate the importance of estrogen production in tumor and surrounding tissues, we measured mRNA expression levels of 5 enzymes participating to estrogen synthesis in situ and 4 breast cancer-related proteins in 27 pairs of tumor and non-malignant tissues. Steroid sulfatase (STS) mRNA was more frequently detected in tumor tissues rather than in their non-malignant counterparts. Estrogen sulfotransferase (EST) was constantly expressed with high level not only in tumor tissues but also in their surrounding non-malignant counterparts. In contrast, mRNA expression levels of aromatase, and 17β-hydroxysteroid dehydrogenase type I and II were relatively low and detected only in small proportion of the patients. We also measured the mRNA expression levels of the same nine genes in tumor tissues of 197 breast cancer patients, and analyzed relationship between the mRNA expression level and the clinicopathological parameters. The mRNA expression levels of STS, aromatase and erbB2 in tumor tissues increased as breast cancer progressed. The tumoral mRNA expression levels of STS, estrogen receptor β, and erbB2 in patients with recurrence were higher than those in patients without recurrence. Upregulation of STS expression plays an important role in tumor progression of human breast cancer and is considered to be responsible for estrogen production in tumor and surrounding tissues. 相似文献
2.
3.
Hideaki Naoe Tatsuyuki Chiyoda Jo Ishizawa Kenta Masuda Hideyuki Saya Shinji Kuninaka 《Biochemical and biophysical research communications》2013,430(2):757-762
Differentiation of placental trophoblast stem (TS) cells to trophoblast giant (TG) cells is accompanied by transition from a mitotic cell cycle to an endocycle. Here, we report that Cdh1, a regulator of the anaphase-promoting complex/cyclosome (APC/C), negatively regulates mitotic entry upon the mitotic/endocycle transition. TS cells derived from homozygous Cdh1 gene-trapped (Cdh1GT/GT) murine embryos accumulated mitotic cyclins and precociously entered mitosis after induction of TS cell differentiation, indicating that Cdh1 is required for the switch from mitosis to the endocycle. Furthermore, the Cdh1GT/GT TS cells and placenta showed aberrant expression of placental differentiation markers. These data highlight an important role of Cdh1 in the G2/M transition during placental differentiation. 相似文献
4.
Ishida Takuya Uehara Yoshitoshi Ikeya Tohru Haraguchi Takashi F. Asano Satoshi Ogino Yohei Okuda Noboru 《Limnology》2020,21(3):403-413
Limnology - Controlling phosphorous (P) loads from rice fields is important for the conservation of aquatic ecosystems, in part because P is relatively concentrated at its sources. Recently, winter... 相似文献
5.
6.
7.
8.
9.
Chromatin was prepared from the buds and cotyledons of Alaskapea seedlings. The dissociated chromosomal components in thepresence of 2 M NaCl and 5 M urea were completely fractionatedinto DNA and proteins with a Bio-Gel A50 column. The proteinswere recovered by (NH4)2SO4 and further fractionated into histonesand non-histone proteins using a Bio-Rex 70(Na+) column. Thedifference in the ratios of histones to non-histone proteinsbefore and after chromatography with the Bio-Rex 70 was lessthan 10%. The histones and non-histone proteins thus preparedshowed typical protein absorption spectra. Polyacrylamide gelelectrophoresis of histones showed that the histone compositionsin buds and cotyledon were similar, but the amount of HI histoneswas a little less in cotyledons than in buds. Unlike histones,non-histone proteins fractionated by SDS-polyacrylamide gelelectrophoresis indicated distinct differences between the twotissues. Buds had more heterogeneous non-histone proteins, atleast 13 polypeptides, than cotyledons did. On the other hand,non-histone proteins of cotyledons showed less heterogeneityand lacked proteins of high molecular weight which were foundin buds. (Received May 6, 1976; ) 相似文献
10.
Masatoshi Kataoka Keizoh Kawamura Tamotsu Kondoh Yoichi Wakano Hiroshi Ishida 《FEMS microbiology letters》1993,107(1):111-114
Abstract A factor showing inhibitory activity against human gingival fibrolasts was extracted from the cytosol fraction of Actinobacillus actinomycetemcomitans Y4. The activity markedly inhibited the proliferation of human gingival fibrolasts, but had no effect on cell viability or gross morphology. No such activity was found in cytosol fractions from either Porphyromonas gingivalis 381 or Escherichia coli HB101. The extract from A. actinomycetemcomitans Y4 was then purified by anion-exchange chromatography, hydroxyapatite chromatography and gel-filtration chromatography to give a single band on SDS-PAGE with an apparent molecular mass of 65 kDa. The purification ratio was 183-fold with a recovery rate of 5% compared with the crude extract (starting material) when the activity was assessed by direct cell counts. 相似文献