全文获取类型
收费全文 | 94913篇 |
免费 | 382篇 |
国内免费 | 884篇 |
专业分类
96179篇 |
出版年
2021年 | 14篇 |
2020年 | 17篇 |
2019年 | 16篇 |
2018年 | 11851篇 |
2017年 | 10689篇 |
2016年 | 7464篇 |
2015年 | 606篇 |
2014年 | 317篇 |
2013年 | 407篇 |
2012年 | 4274篇 |
2011年 | 12880篇 |
2010年 | 12038篇 |
2009年 | 8267篇 |
2008年 | 9875篇 |
2007年 | 11466篇 |
2006年 | 350篇 |
2005年 | 610篇 |
2004年 | 1052篇 |
2003年 | 1116篇 |
2002年 | 875篇 |
2001年 | 322篇 |
2000年 | 208篇 |
1999年 | 68篇 |
1998年 | 40篇 |
1997年 | 46篇 |
1996年 | 35篇 |
1995年 | 26篇 |
1994年 | 31篇 |
1993年 | 48篇 |
1992年 | 66篇 |
1991年 | 74篇 |
1990年 | 36篇 |
1989年 | 37篇 |
1988年 | 40篇 |
1987年 | 43篇 |
1986年 | 23篇 |
1985年 | 17篇 |
1984年 | 25篇 |
1983年 | 39篇 |
1982年 | 16篇 |
1981年 | 18篇 |
1980年 | 19篇 |
1977年 | 15篇 |
1976年 | 16篇 |
1975年 | 14篇 |
1973年 | 15篇 |
1972年 | 251篇 |
1971年 | 280篇 |
1965年 | 18篇 |
1962年 | 24篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
92.
J L Lin T Asano H Katagiri K Tsukuda H Ishihara K Inukai Y Yazaki Y Oka 《Biochemical and biophysical research communications》1992,184(2):865-870
We engineered the GLUT1 cDNA to delete C-terminal 12 amino acids of encoded GLUT1 protein. This mutated GLUT1 protein expressed in CHO cells by transfection of its cDNA was demonstrated to reside on the plasma membrane by cell surface labeling technique, and retain the transport activity, similar to that of the wild-type GLUT1. In addition, metabolic labeling of the intact cells with 35S indicated that the half-life of the mutated GLUT1 was not significantly different from that of the wild-type GLUT1. These results suggest that C-terminal 12 amino acids of GLUT1 are not important for the transport activity and the stability of the protein. Taken together with our previous results on the mutant without C-terminal 37 amino acids, the amino acids between the 37th and the 13th from the C-terminus appear to be essential for the transport activity. 相似文献
93.
S Takahashi K Uchimaru K Harigaya S Asano T Yamashita 《Biochemical and biophysical research communications》1992,188(1):310-317
Activin A, a homodimer of the beta A chain, regulates hematopoiesis. In a human bone marrow-derived stromal cell line, KM-102, phorbol myristate acetate, tumor necrosis factor-alpha and interleukin-1 beta induced great increases in beta A chain mRNA levels and production of activin A activities. The phorbol ester-induced beta A chain gene expression was inhibited by cycloheximide and down regulation of protein kinase C, whereas the cytokine-induced expression was little affected by these treatments. These results indicate that the inflammatory cytokines directly stimulate beta A chain gene expression via protein kinase C-independent pathways. 相似文献
94.
K. Terasawa T. Fujiwara A. Sakai N. Yanagidaira K. Asano K. Yanagisawa N. Kashimura G. Ueda T. Wu Y. Zhang 《International journal of biometeorology》1996,39(3):111-115
Handgrip force (HF), maximal pinch force (MF), muscle endurance (ME), and the median power frequency (MdPF) of the activity shown in the electromyogram (EMG) were studied at various altitudes in eight normal healthy subjects. MF and ME were measured between the index finger and thumb, and all measurements were obtained at altitudes ranging from 610 to 4860 m during an expedition in the Qinghai Plateau in China. With the change in altitude HF, ME, and MF showed no significant change. Compared to the MdPF at 2260 m on ascent, the MdPF at other altitudes showed a significant decrease (P<0.01). Thus, we conclude that muscle performance (HF, MF, and ME) was not affected by the environment at high altitude. However, MdPF was affected and the mean MdPF at 610 m after the expedition did not recover to initial values of MdPF. We suggest these results may have been affected by fatigue and chronic exposure to the hypobaric hypoxic environment, since the members of the expedition party expressed feelings of sluggishness and fatigue after the expedition. 相似文献
95.
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
96.
97.
98.
Maxim K. Elias 《Pal?ontologische Zeitschrift》1962,36(1):29-37
The type specimen ofGonioloboceras goniolobum (Meek), rediscovered by Spath in the British Museum, is the foundation for a more accurate comparative study of this and other species ofGonioloboceras.Gonioloboceras described asG. goniolobum byElias in 1938 is differentiated asGonioloboceras schmidti, new species. Suture sets (new term) for several growth stages inG. goniolobum (Meek),G. welleriSmith,G. schmidtiElias, G.eliasiMiller &Owen, andG. asiaticumLibrovitch are assembled and used for differentiation of the species.The Kazakhstan goniatite faunule containingG. asiaticum is considered of very late Pennsylvanian age. 相似文献
99.
R. Schoysman B. Lejeune E. Van Roosendaal L. Segal P. Vanderzwalmen M. Nijs B. Vandamme G. Bertin 《Andrologie》1996,6(4):432-439
The authors report their experience with the use of spermatids in TESE programs where mature spermatozoa could not be isolated from testicular biopsies. The details of the indications for spermatid insemination, the technicity of the procedure and the results are exposed. 相似文献
100.
3-Methylaspartase was purified 24-fold and crystallized from the crude extract of the cells of a facultative anaerobic bacterium
from soil, strain YG-1002. The molecular mass of the native enzyme was about 84 kDa and that of the subunit was about 42 kDa.
The pH optimum for the deamination reaction of (2S, 3S)-3-methylaspartic acid and those for the amination reaction of mesaconic acid were 9.7 and 8.5; its optimum temperature was
50°C. The enzyme was stable at pH 5.5–11.0 and up to 50°C. The enzyme required both divalent and monovalent cations such as
Mg2+ and K+. The enzyme was inhibited by sulfhydryl reagents, metal-chelating reagents and some divalent cations. The enzyme catalyzed
the reversible amination/deamination reactions between several 3-substituted (S)-aspartic acids and their corresponding fumaric acid derivatives. The enzyme preferentially acted on (2S, 3S)-3-methylaspartic acid and mesaconic acid in the deamination and the amination reactions respectively. The enzyme showed
high similarities in several enzymological properties and N-terminal amino acid sequence with 3-methylaspartase from an obligate
anaerobic bacteriumClostridium tetanomorphum. 相似文献