全文获取类型
收费全文 | 4550篇 |
免费 | 287篇 |
国内免费 | 5篇 |
专业分类
4842篇 |
出版年
2023年 | 13篇 |
2022年 | 26篇 |
2021年 | 62篇 |
2020年 | 25篇 |
2019年 | 55篇 |
2018年 | 59篇 |
2017年 | 64篇 |
2016年 | 95篇 |
2015年 | 149篇 |
2014年 | 170篇 |
2013年 | 313篇 |
2012年 | 276篇 |
2011年 | 291篇 |
2010年 | 151篇 |
2009年 | 157篇 |
2008年 | 284篇 |
2007年 | 269篇 |
2006年 | 286篇 |
2005年 | 279篇 |
2004年 | 284篇 |
2003年 | 253篇 |
2002年 | 239篇 |
2001年 | 56篇 |
2000年 | 51篇 |
1999年 | 64篇 |
1998年 | 64篇 |
1997年 | 48篇 |
1996年 | 46篇 |
1995年 | 39篇 |
1994年 | 52篇 |
1993年 | 40篇 |
1992年 | 42篇 |
1991年 | 36篇 |
1990年 | 40篇 |
1989年 | 41篇 |
1988年 | 27篇 |
1987年 | 32篇 |
1986年 | 21篇 |
1985年 | 42篇 |
1984年 | 32篇 |
1983年 | 28篇 |
1982年 | 27篇 |
1981年 | 17篇 |
1980年 | 26篇 |
1978年 | 17篇 |
1976年 | 26篇 |
1975年 | 16篇 |
1974年 | 21篇 |
1972年 | 12篇 |
1970年 | 12篇 |
排序方式: 共有4842条查询结果,搜索用时 15 毫秒
21.
Close linkage of MEN2A with RBP3 locus in Japanese kindreds 总被引:7,自引:0,他引:7
Masayuki Yamamoto Shin-ichiro Takai Tetsuro Miki Kazuyoshi Motomura Makoto Okazaki Isamu Nishisho Hideo Tateishi Akira Miyauchi Tasuku Honjo A. J. Pakstis Takesada Mori 《Human genetics》1989,81(3):287-288
Summary The gene responsible for multiple endocrine neoplasia type 2A (MEN2A) has recently been assigned to the pericentromeric region of chromsome 10 in European Caucasian kindreds by linkage analysis using a DNA marker, interstitial retinol-binding protein 3 (RBP3). We have found tight linkage between the MEN2A and RBP3 loci in Japanese MEN2A kindreds. The maximum lod score is 5.19 at a recombination fraction of 0.00. This result suggests that mutation of a certain gene close to RBP3 is responsible for MEN2A irrespective of ethnic backgrounds. 相似文献
22.
23.
Makiko Kawagishi-Kobayashi Masayuki Yamamoto Akira Ishihama 《Molecular & general genetics : MGG》1996,250(1):1-6
Local sequence similarity exists between the subunit 2 of eukaryotic RNA polymerases II and the barnase-type bacterial RNases. The RNase-like domain from the Rpb2 ofSchizosaccharomyces pombe was expressed inEscherichia coli as a GST fusion protein and examined for its RNase activity. When the GST fusion protein was incubated in vitro with32P-labeled RNA, the RNA degradation activity was less than 0.1%, if any, of the level of synthetic barnase. In order to check the in vivo function of this region, we constructed two mutantrpb2 alleles,rpb2
E357A
andrpb2
H3a6L
, each carrying a single amino acid substitution at the site correponding to one of the three essential amino acid residues forming the catalytic site in barnase (mutation of barnase at the corresponding sites results in complete loss of RNase activity) and five other mutantrpb2 alleles, each carrying a single mutation at various positions within the RNase-like domain but outside the putative catalytic site for RNase activity. When these mutantrpb2 alleles were expressed in anrpb2-disruptedS. pombe strain, all the mutants grew as well as the wild-type parent and did not show any clear defective phenotypes. These results suggest either that the RNase-like domain in Rpb2 does not function as an RNase in vivo or that the RNase activity of this domain, if present at all, is not essential for cell growth. 相似文献
24.
Effects of interleukin-12 on in vitro culture with interleukin-2 of regional lymph node lymphocytes from lung cancer patients 总被引:2,自引:0,他引:2
T. Hanagiri Mitsuhiro Takenoyama Takashi Yoshimatsu Chikashi Hirashima Ichiro Yoshino Kozo Nakanishi Akira Nagashima Kikuo Nomoto Kosei Yasumoto 《Cancer immunology, immunotherapy : CII》1996,43(2):87-93
In the present study, we carried out a functional analysis of regional lymph node lymphocytes (RLNL) from patients with lung
cancer after in vitro activation by interleukin-2 (IL-2) and interleukin-12 (IL-12). IL-12 (100 U/ml) enhanced both the proliferation
and cytotoxic activity of RLNL in a culture with low doses of IL-2 (5 – 10 JRU/ml). After comparing an RLNL culture with a
low dose of IL-2 alone, a higher proportion of CD8+ cells and CD56+ cells and a lower proportion of CD4+ cells were found in the culture with both IL-12 and a low dose of IL-2. Such a combination of the cytokines effectively activated
RLNL in terms of the expression of IL-2 receptors. In the culture condition of IL-12 and a low dose of IL-2, a synergistic
effect was observed in the production of such cytokines as interferon γ, tumor necrosis factor α (TNFα), and TNFβ, as well
as in tumor cytotoxicity. However, the addition of IL-12 inhibited the cytotoxicity of RLNL in the culture with a high dose
of IL-2 (100 JRU/ml). This inhibition is considered to be partially due to the endogenous production of TNFα by lymphocytes,
because the neutralization of TNFα bioactivity partially restored the cytotoxic activities of RLNL. Furthermore, in the presence
of hydrocortisone, IL-12 synergistically enhanced the cytotoxic activity of RLNL cultured with a high dose of IL-2. These
results provide useful information about the improvement of adoptive immunotherapy against cancer using RLNL.
Received: 2 February 1996 / Accepted: 30 July 1996 相似文献
25.
26.
The effect of -alanyl-L-histidinato zinc (AHZ) on bone metabolism was investigated in osteoblastic MC3T3-El cells. Cells were cultured for 3 days at 37°C in a CO2 incubator in plastic dishes containing -modified minimum essential medium supplemented with 10% fetal bovine serum. After the cultures, the medium was exchanged for that containing 0.1% bovine serum albumin plus various concentrations of AHZ or other reagents, and the cells were cultured further for appropriate periods of time. The presence of AHZ (10–7–10–5M) stimulated the proliferation of cells. AHZ (10–6 and 10–5M) increased deoxyribonucleic acid (DNA) content in the cells with 48hr-culture. This increase was completely blocked by the presence of cycloheximide (10–6M) or hydroxyurea (10–3M). Also, the presence of cycloheximide (10–6M) completely inhibited the AHZ (10–5M)-induced increase in the proliferation of cells. Meanwhile, parathyroid hormone (10–7M), estrogen (10–9M) and insulin (10–M) significantly increased cellular DNA content. However, these hormonal effects clearly lowered in comparison with that of AHZ (10–5M). Dibutyryl cyclic AMP (10–4M) and zinc sulfate (10–5M) did not cause a significant increase in cellular DNA content. The present results support the view that AHZ has a direct specific proliferative effect on osteoblastic cellsin vitro and that this effect is dependent on protein synthesis. 相似文献
27.
28.
Yoshihiro Izumi Kanji Ono Masayuki Takamiya Kiichi Fukui 《Journal of plant research》1993,106(4):319-325
Using cultured cells of the hornwortAnthoceros punctatus, the change in the relative chloroplast DNA content in each stage of chloroplast division was investigated to clarify the
relationship between the division cycle of a chloroplast and a cell nucleus. Samples of cultured cells were stained with 4′,6-diamidino-2-phenylindole
(DAPI) and then observed with an epifluorescence microscope and a chromosome image analyzing system (CHIAS). A chloropiast
in cultured cells duplicated DNA with an increase in size. When a chloroplast began to divide, it was constricted in the middle,
taking a dumbbell shape, and then divided into two daughter chloroplasts. In cultured cells of this species, the pattern of
quantitative change of chloroplast DNA, that is, the DNA replication pattern of chloroplasts, corresponded to that of cell
nuclear DNA in mitosis. 相似文献
29.
Photo-induced activation of cytochrome P450/reductase fusion enzyme coupled with spinach chloroplasts 总被引:1,自引:0,他引:1
Young-Sug Kim Masayuki Hara Kazunori Ikebukuro Jun Miyake Hideo Ohkawa Isao Karube 《Biotechnology Techniques》1996,10(10):717-720
Summary Photoactivation of cytochrome P450 monooxygenase was studied using a combination of spinach chloroplasts and yeast microsomes containing rat P4501A1/yeast reductase fusion enzyme. Under illumination, in the reaction mixture, NADP was reduced, transferring electrons to the P450/reductase fusion enzyme to convert 7-ethoxycoumarin to 7-hydroxycoumarin. 相似文献
30.
Two new shrimp-associated gobies,Amblyeleotris yanoi sp. nov. andA. masuii sp. nov. are described on the basis of specimens from Iriomote-jima Island and Okinawa-jima Islands, Okinawa Prefecture,
Japan.A. yanoi is distinguished from other members of the genus by the combination of the following characters: 14 anal fin soft rays, 19
pectoral fin rays, 97–103 longitudinal scales, a candle flame-shaped marking on the caudal fin, a very low membrane connecting
the pelvic fins and absence of a ventral frenum.A. masuii differs from all other congeners by having 92–97 longitudinal scales, the length of the interpelvic connecting membrane relative
to the longest pelvic fin ray (0.43–0.66), black blotches on the sides of the chin, and blue spots on the opercle and preopercle. 相似文献