全文获取类型
收费全文 | 15837篇 |
免费 | 1005篇 |
国内免费 | 2篇 |
出版年
2021年 | 160篇 |
2020年 | 75篇 |
2019年 | 124篇 |
2018年 | 168篇 |
2017年 | 145篇 |
2016年 | 260篇 |
2015年 | 388篇 |
2014年 | 463篇 |
2013年 | 932篇 |
2012年 | 815篇 |
2011年 | 791篇 |
2010年 | 436篇 |
2009年 | 474篇 |
2008年 | 743篇 |
2007年 | 721篇 |
2006年 | 727篇 |
2005年 | 729篇 |
2004年 | 778篇 |
2003年 | 745篇 |
2002年 | 697篇 |
2001年 | 559篇 |
2000年 | 551篇 |
1999年 | 453篇 |
1998年 | 206篇 |
1997年 | 173篇 |
1996年 | 155篇 |
1995年 | 149篇 |
1994年 | 140篇 |
1993年 | 146篇 |
1992年 | 341篇 |
1991年 | 321篇 |
1990年 | 320篇 |
1989年 | 289篇 |
1988年 | 246篇 |
1987年 | 248篇 |
1986年 | 221篇 |
1985年 | 190篇 |
1984年 | 148篇 |
1983年 | 142篇 |
1982年 | 120篇 |
1981年 | 110篇 |
1980年 | 94篇 |
1979年 | 117篇 |
1978年 | 94篇 |
1977年 | 83篇 |
1976年 | 82篇 |
1975年 | 73篇 |
1974年 | 88篇 |
1973年 | 93篇 |
1969年 | 68篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
11.
12.
The rhodopsin preparation obtained by the method of ammonium sulfate fractionation contained 3–6 mol phospholipid and about 18 mol cholate per mol rhodopsin. The purified rhodopsin had 74% helical structure and showed a visible CD spectrum different from that of rhodopsin in the membrane. The rhodopsin was stable below but denatured gradually above 20°C. The lifetime of metarhodopsin I was long in this preparation. Regeneration capacity was low and only 30% of the original rhodopsin was regenerable by addition of 11-cis-retinal after bleaching.50 mol of phosphatidylcholine were maximally bound to 1 mol rhodopsin when the purified rhodopsin was mixed with phosphatidylcholine in 0.5% cholate. The rhodopsin recombined with lipid had properties similar to those of the original rhodopsin in the membrane. Exchange of cholate for other detergents was easily performed by dialysis. The rhodopsin preparation in which cholate was exchanged for digitonin gave almost the same CD, thermal stability and regenerability as those of a native rhodopsin in the membrane but metarhodopsin I still retained its long lifetime. 相似文献
13.
Naturally occurring subclinical Corynebacterium kutscheri infection was analyzed by antibody response related to the strain of rats. Wistar-Lewis, Wistar and Spraque-Dawley rats were high responders in seroconversion rates and antibody titers, while Brown Norway and Fischer rats were low responders. The antibody response was related to age also. Some young rats had maternal antibody to C. kutscheri, but antibody disappeared before 8 weeks of age. Rats were antibody-negative for several months thereafter and became antibody-positive after 6 months of age. The antibody response was highest at 8 to 9 months of age in subclinical C. kutscheri infection. This antibody response was very late, compared to the antibody response to Sendai virus and Mycoplasma infections. 相似文献
14.
15.
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
16.
17.
18.
A putative GDP–GTP exchange factor is required for development of the excretory cell in Caenorhabditis elegans 下载免费PDF全文
Norio Suzuki Matthew Buechner Kiyoji Nishiwaki David H. Hall Hiroyuki Nakanishi Yoshimi Takai Naoki Hisamoto Kunihiro Matsumoto 《EMBO reports》2001,2(6):530-535
The Caenorhabditis elegans excretory cell extends tubular processes, called canals, along the basolateral surface of the epidermis. Mutations in the exc-5 gene cause tubulocystic defects in this canal. Ultrastructural analysis suggests that exc-5 is required for the proper placement of cytoskeletal elements at the apical epithelial surface. exc-5 encodes a protein homologous to guanine nucleotide exchange factors and contains motif architecture similar to that of FGD1, which is responsible for faciogenital dysplasia. exc-5 interacts genetically with mig-2, which encodes Rho GTPase. These results suggest that EXC-5 controls the structural organization of the excretory canal by regulating Rho family GTPase activities. 相似文献
19.
20.
S Hoshino M Suzuki T Kakegawa K Imai M Wakita Y Kobayashi Y Yamada 《Comparative biochemistry and physiology. A, Comparative physiology》1988,90(2):355-359
1. Circulating concentrations of iodothyronines, luteinizing hormone(LH), estradiol(E2), progesterone and corticosterone were measured in hens before, during, and after a forced molt induced by fasting. 2. Corticosterone increased at the onset of molt, peaked at the maximal molt and returned to pre- and post-molt levels. LH, E2 and progesterone declined during the molt, and the decline was coincident with the cessation of egg production. 3. Thyroxine(T4), triiodothyronine (T3) and reverse triiodothyronine(rT3) increased during the molt. The increases of T4 and T3 were not abolished even if the forced molt was conducted in mild weather. 相似文献