全文获取类型
收费全文 | 20663篇 |
免费 | 1986篇 |
国内免费 | 2220篇 |
出版年
2024年 | 41篇 |
2023年 | 395篇 |
2022年 | 501篇 |
2021年 | 747篇 |
2020年 | 668篇 |
2019年 | 984篇 |
2018年 | 907篇 |
2017年 | 585篇 |
2016年 | 646篇 |
2015年 | 799篇 |
2014年 | 1420篇 |
2013年 | 1528篇 |
2012年 | 1014篇 |
2011年 | 1386篇 |
2010年 | 1042篇 |
2009年 | 1115篇 |
2008年 | 1111篇 |
2007年 | 1225篇 |
2006年 | 1065篇 |
2005年 | 934篇 |
2004年 | 788篇 |
2003年 | 662篇 |
2002年 | 639篇 |
2001年 | 416篇 |
2000年 | 395篇 |
1999年 | 349篇 |
1998年 | 349篇 |
1997年 | 262篇 |
1996年 | 267篇 |
1995年 | 314篇 |
1994年 | 255篇 |
1993年 | 223篇 |
1992年 | 200篇 |
1991年 | 194篇 |
1990年 | 163篇 |
1989年 | 135篇 |
1988年 | 127篇 |
1987年 | 105篇 |
1986年 | 73篇 |
1985年 | 113篇 |
1984年 | 165篇 |
1983年 | 121篇 |
1982年 | 148篇 |
1981年 | 65篇 |
1980年 | 55篇 |
1979年 | 55篇 |
1978年 | 41篇 |
1977年 | 21篇 |
1976年 | 13篇 |
1974年 | 13篇 |
排序方式: 共有10000条查询结果,搜索用时 236 毫秒
51.
52.
Andrew Leask 《Journal of cell communication and signaling》2010,4(1):73-74
Connective tissue growth factor (CTGF/CCN2) is overexpressed in diabetes. Diabetic rats possess myocardial and cardiomyocyte hypertrophy. In a recent report, Wang and colleagues (Am J Physiol Cell Physiol. 2009 Jul 22. [Epub ahead of print]) show that CCN2 directly mediates cardiomyocyte hypertrophy as well as that induced by high glucose and fatty acid. CCN2 acted via the TrkA receptor. These data are the subject of this commentary, and emphasize that CCN2 may be an excellent target for therapy in diabetes. 相似文献
53.
54.
J. Moreno-González A. R. Hallauer 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1982,61(4):353-358
Summary A method (CRRS) that combines S2 and crossbred family selection in full-sib reciprocal recurrent selection (FSRRS) is proposed. The method requires four generations per cycle in single-eared maize populations. Selection is based on performance of S2 and full-sib families by applying selection index theory. Equations to estimate the coefficients included in the index are given. These estimates are functions of the genetic and phenotypic variances and covariances among and between the two kinds of families. Comparisons of FSRRS and CRRS under equivalent amount of effort show that CRRS has some advantage over FSRRS for low heritability of the trait being selected (e.g., maize yield) and when only one or two locations with two replications are involved in the selection experiment.Joint contribution: Institute Nacional de Investigaciones Agrarias, La Coruna, Spain; and Agricultural Research, Science and Education Administration, U.S. Department of Agriculture, and Journal Paper No. J-10118 of the Iowa Agriculture and Home Economics Experiment Station, Ames, IA 50011. Project 2194 相似文献
55.
56.
Growth hormone-releasing factor (GRF) is a hypothalamic peptide named for its ability to induce release of growth hormone from the anterior pituitary. GRF also acts as a neurotransmitter in the suprachiasmatic nucleus/medial preoptic area (SCN/MPOA) to stimulate food intake. The purpose of this series of experiments was to explore the nature of GRF-induced feeding, with a particular emphasis on macronutrient selectivity, and to examine the role of opiate activity in the paraventricular nucleus of the hypothalamus (PVN). Chow intake stimulated by GRF microinjection (1 pmol/0.5 μl) into the SCN/MPOA was blocked by injection of methyl-naltrexone (3 μg/0.5 μl) into the PVN. In animals habituated to macronutrient diets (Teklad, WI), GRF preferentially stimulated intake of protein at 2 and 4 h postinjection, whereas it had no effect on carbohydrate intake. Further, this effect was blocked by injection of naloxone (40 nmol/0.5 μl) into the PVN. Microinjection of morphine (0, 1, 10, and 17 μg/0.5 μl) into the PVN also specifically stimulated protein intake at 2 and 4 h postinjection. These results suggest that feeding derived from GRF actions in the SCN/MPOA is macronutrient selective, and is dependent on PVN opiate activity for expression. 相似文献
57.
J.N. Beresford J.A. Gallagher M. Gowen M. Couch J. Poser D.D. Wood R.G.G. Russell 《Biochimica et Biophysica Acta (BBA)/General Subjects》1984,801(1):58-65
Cultural adherent human mononuclear cells produce factor(s) which stimulate the release of calcium from new-born mouse calvaria in organ culture. This stimulation of bone resorption is accompanied by an inhibition of the incorporation of [3H]proline into collagen which is independent of increased prostaglandin production by the bone. When human osteoblast-like cells are treated with conditioned medium from human mononuclear cells, collagen accounts for a decreased proportion of the protein synthesised. This effect on matrix synthesis is not accompanied by an inhibitory action of the monocyte-conditioned medium preparations on net cell proliferation. In human osteoblast-like cell cultures, partially purified human interleukin 1 also inhibits the production of the bone-specific protein osteocalcin in a dose-dependent fashion. These observations are consistent with the hypothesis that products of human monocytes similar to, or identical with, human interleukin 1 may be important regulators of bone metabolism and may contribute to the bone loss seen in diseases such as chronic rheumatoid arthritis. 相似文献
58.
59.
Young J. Oh Jonathan W. Francis George J. Markelonis Tae H. Oh 《Journal of neurochemistry》1992,58(6):2131-2138
Peripheral-type benzodiazepine binding sites (PTBBS) are markedly increased in the injured CNS. Astrocytes appear to be the primary cell type which express increased PTBBS. Because certain cytokines within the injured CNS are potent mitogens for astrocytes, we examined the effects of two such cytokines, interleukin (IL)-1 beta and tumor necrosis factor (TNF), on PTBBS in cultured astrocytes using [3H]Ro 5-4864 as the specific ligand. Purified cultures of either polygonal or process-bearing astrocytes were prepared from neonatal rat cerebral hemispheres. At a concentration of 1.8 nM, specific binding of the radioactive ligand to polygonal astrocytes reached equilibrium within 60 min and was half-maximal by 5-10 min. By contrast, specific binding to process-bearing astrocytes barely exceeded background levels. IL-1 and TNF increased PTBBS within polygonal astrocytes in both dose- and time-dependent manners. At 10-50 ng/ml, IL-1 beta and TNF-alpha elevated [3H]Ro 5-4864 binding in polygonal astrocyte cultures 65 and 87%, respectively, above the level in control cultures. However, no changes in PTBBS were seen within polygonal astrocytes after IL-2 treatment. Scatchard analysis of saturation binding experiments suggested that the increase in PTBBS promoted by TNF was due to an increased number of binding sites present in polygonal astrocytes and not due to an increase in receptor affinity. Binding data suggested that PTBBS within cultures of process-bearing astrocytes were virtually absent irrespective of the treatment. These in vitro data suggest that certain cytokines found in the injured brain may be involved in up-regulating PTBBS within a particular subtype of astrocyte. 相似文献
60.
Juri M. Vasiliev 《生物化学与生物物理学报:癌评论》1984,780(1):21-65
Mechanisms of cellular reactions responsible for the spreading non-transformed cultured tissue cells on the surface of various substrata and relationships of these reactions to the control of cell proliferation are reviewed; the special role of the membrane-cystoskeleton interactions leading to extension and attachment of psuedopods is stressed.Transition of cells from non-transformed to transformed phenotype is characterized by decreased spreading and by decreased dependence of proliferation on spreading. Manifestations of both of these spreading-associated changes are reviewed and their possible mechanisms are discussed. It is suggested that cell transition to transformed phenotype involves shift of an equilibrium between the reactions induced by the two groups of membrane-bound ligands: those attached and those not attached to the substratum. 相似文献