全文获取类型
收费全文 | 3922篇 |
免费 | 337篇 |
出版年
2023年 | 24篇 |
2022年 | 59篇 |
2021年 | 99篇 |
2020年 | 70篇 |
2019年 | 70篇 |
2018年 | 93篇 |
2017年 | 76篇 |
2016年 | 136篇 |
2015年 | 238篇 |
2014年 | 231篇 |
2013年 | 308篇 |
2012年 | 356篇 |
2011年 | 296篇 |
2010年 | 218篇 |
2009年 | 190篇 |
2008年 | 195篇 |
2007年 | 193篇 |
2006年 | 171篇 |
2005年 | 122篇 |
2004年 | 112篇 |
2003年 | 108篇 |
2002年 | 77篇 |
2001年 | 44篇 |
2000年 | 41篇 |
1999年 | 46篇 |
1998年 | 22篇 |
1997年 | 26篇 |
1996年 | 22篇 |
1993年 | 22篇 |
1992年 | 37篇 |
1991年 | 30篇 |
1990年 | 34篇 |
1989年 | 31篇 |
1988年 | 27篇 |
1987年 | 34篇 |
1986年 | 36篇 |
1985年 | 24篇 |
1984年 | 16篇 |
1983年 | 13篇 |
1982年 | 19篇 |
1980年 | 13篇 |
1979年 | 13篇 |
1978年 | 20篇 |
1977年 | 13篇 |
1976年 | 20篇 |
1975年 | 17篇 |
1974年 | 16篇 |
1971年 | 18篇 |
1970年 | 14篇 |
1966年 | 13篇 |
排序方式: 共有4259条查询结果,搜索用时 93 毫秒
1.
C Julien C Barres P Kandza J Sassard 《Comptes rendus de l'Académie des sciences. Série III, Sciences de la vie》1989,308(8):219-222
Intra-aortic blood pressure (BP) was measured in conscious rats after early chronic destruction of the peripheral sympathetic nervous system (SNS) with guanethidine. In sympathectomized rats, the mean level of BP was not different from that of control rats but its variability was markedly increased. These results indicate that functional integrity of the SNS is of primary importance for the short-term control of BP but is not essential for its long-term maintenance. 相似文献
2.
A Malassiné C Besse A Roche E Alsat R Rebourcet F Mondon L Cedard 《Histochemistry》1987,87(5):457-464
Low density lipoproteins (LDL) were conjugated to colloidal gold to visualize the route for internalization of LDL in the cultured cells of human term placenta. Cells were obtained from placental villi (caesarian section) by a standard trypsin-DNase dispersion method followed in some cases by a Percoll gradient centrifugation step. Employing electron microscopy it was observed that after 3 days of culture, cells obtained by trypsin-DNase dispersion were a mixture of macrophages, mononucleated cells and large multinucleated cells. When the cells were incubated for 3 days after the Percoll purification, essentially multinucleated cells identical to the syncytiotrophoblast were present. The number of LDL receptor was increased by preincubation in medium with lipoprotein depleted serum. In binding experiments cells incubated at 4 degrees C for 2 h with medium containing gold LDL conjugates showed gold LDL attached to the plasma membrane without characteristic localization. After incubation with gold LDL at 37 degrees C for various times, the three cellular types showed ligand internalization. Gold LDL endocytosis involved first coated pits but also uncoated plasmalemmal invaginations. Then gold LDL was further observed in coated and non coated vesicles, smooth walled endosomes, multivesicular bodies and tubular vesicles. Lastly free gold particles were observed in lysosome like dense bodies. These results prove the internalization of gold LDL conjugates by human cultured placental cells, particularly by syncytiotrophoblast like multinucleated cells. This accumulation of LDL (the major cholesterol carrying protein in humans) is recognised to be responsible for the exogenous cholesterol supply indispensable to the progesterone biosynthesis and cellular growth of the placenta. 相似文献
3.
4.
5.
6.
7.
F Monaco M Andreoli A La Posta J Roche 《Comparative biochemistry and physiology. B, Comparative biochemistry》1978,60(1):87-91
1. The biosynthesis of 18-19S thyroglobulin has been studied in a larval and adult freshwater lamprey (Lampetra planeri Bl.). 2. In vivo and in vitro experiments have been performed by injecting into the coelomic cavity or by incubating branchial region labeled constituents of Tg of higher vertebrates (125I, [3H]leucine and various [3H]carbohydrates). 3. Larvae (ammocoetes) and adults incorporate all labels into thyroglobulin (18-19S Tg), containing a small proportion of labeled T3 and T4, as identified by paper chromatography, and very minute amounts of stable iodine. 4. In adults, the biosynthesis of 18-19S Tg proceeds much more rapidly and the labels are incorporated in higher percentage than in larvae. 5. The demonstration of the biosynthesis of the specific thyroid protein, 18-19S Tg, in larvae indicates that the biochemical mechanism of hormonogenesis is present in larval endostyle before the morphological differentiation of thyroid cells and follicles occurring during metamorphosis. 6. Some 18-19S Tg is apparently stored in the endostyle. 相似文献
8.
9.
Osteoblasts synthesize and respond to transforming growth factor-type beta (TGF-beta) in vitro 总被引:29,自引:11,他引:18
P G Robey M F Young K C Flanders N S Roche P Kondaiah A H Reddi J D Termine M B Sporn A B Roberts 《The Journal of cell biology》1987,105(1):457-463
Transforming growth factor-type beta (TGF-beta) has been identified as a constituent of bone matrix (Seyedin, S. M., A. Y. Thompson, H. Bentz, D. M. Rosen, J. M. McPherson, A. Conti, N. R. Siegel, G. R. Gallupi, and K. A. Piez, 1986, J. Biol. Chem. 261:5693-5695). We used both developing bone and bone-forming cells in vitro to demonstrate the cellular origin of this peptide. TGF-beta mRNA was detected by Northern analysis in both developing bone tissue and fetal bovine bone-forming cells using human cDNA probes. TGF-beta was shown to be synthesized and secreted by metabolically labeled bone cell cultures by immunoprecipitation from the medium. Further, TGF-beta activity was demonstrated in conditioned media from these cultures by competitive radioreceptor and growth promotion assays. Fetal bovine bone cells (FBBC) were found to have relatively few TGF-beta receptors (5,800/cell) with an extremely low Kd of 2.2 pM (high binding affinity). In contrast to its inhibitory effects on the growth of many cell types including osteosarcoma cell lines, TGF-beta stimulated the growth of subconfluent cultures of FBBC; it had little effect on the production of collagen by these cells. We conclude that bone-forming cells are a source for the TGF-beta that is found in bone, and that these cells may be modulated by this factor in an autocrine fashion. 相似文献
10.
E Roche E Knecht S Grisolía 《Biochemical and biophysical research communications》1987,142(3):680-687
2,3-bisphosphoglycerate at physiological concentration similar to that found in many tissues protects effectively ornithine transcarbamoylase (OTC) from proteolytic inactivation by broken lysosomes. 2,3-bisphosphoglycerate protects also many other mitochondrial and cytosolic proteins, such as glutamate dehydrogenase (GDH) an glyceraldehyde-3-phosphate dehydrogenase (GAPDH), from proteolysis by broken lysosomes and other proteases. It is, thus, suggested that 2,3-bisphosphoglycerate may play an important role in the control of the degradative rates of some proteins, which may explain its high concentration in certain cells. 相似文献