全文获取类型
收费全文 | 13707篇 |
免费 | 699篇 |
国内免费 | 8篇 |
出版年
2022年 | 60篇 |
2021年 | 113篇 |
2020年 | 58篇 |
2019年 | 85篇 |
2018年 | 139篇 |
2017年 | 145篇 |
2016年 | 245篇 |
2015年 | 375篇 |
2014年 | 432篇 |
2013年 | 1138篇 |
2012年 | 764篇 |
2011年 | 826篇 |
2010年 | 481篇 |
2009年 | 461篇 |
2008年 | 778篇 |
2007年 | 864篇 |
2006年 | 852篇 |
2005年 | 889篇 |
2004年 | 972篇 |
2003年 | 907篇 |
2002年 | 856篇 |
2001年 | 138篇 |
2000年 | 96篇 |
1999年 | 144篇 |
1998年 | 220篇 |
1997年 | 206篇 |
1996年 | 169篇 |
1995年 | 145篇 |
1994年 | 114篇 |
1993年 | 153篇 |
1992年 | 126篇 |
1991年 | 91篇 |
1990年 | 90篇 |
1989年 | 88篇 |
1988年 | 85篇 |
1987年 | 64篇 |
1986年 | 73篇 |
1985年 | 86篇 |
1984年 | 100篇 |
1983年 | 87篇 |
1982年 | 106篇 |
1981年 | 95篇 |
1980年 | 83篇 |
1979年 | 41篇 |
1978年 | 47篇 |
1977年 | 43篇 |
1976年 | 51篇 |
1975年 | 26篇 |
1974年 | 36篇 |
1973年 | 33篇 |
排序方式: 共有10000条查询结果,搜索用时 703 毫秒
981.
Chu C Jin Q Kunitake T Kato K Nabekura T Nakazato M Kangawa K Kannan H 《Regulatory peptides》2002,105(1):29-34
Neuromedin U (NMU) is a brain-gut peptide, which peripherally stimulates smooth muscle, increases of blood pressure, alters ion transport in the gut, controls local blood flow, and regulates adrenocortical function. Although intracerebroventricular (i.c.v.) administration of NMU is known to decrease food intake and body weight, little is known about its effect on other physiological functions. We examined the effects of i.c.v. administration of NMU on mean arterial pressure (MAP), heart rate (HR), and plasma norepinephrine in conscious rats. Neuromedin U (0.05 and 0.5 nmol) provoked an increase in MAP (93.8 +/- 0.5 to 123.5 +/- 1.7 and 94.7 +/- 0.8 to 132.7 +/- 3.0 mm Hg, respectively) and HR (334.9 +/- 6.0 to 494.1 +/- 6.9 and 346.3 +/- 3.3 to 475.1 +/- 8.9 beats/min, respectively). In contrast, plasma norepinephrine increased only with a high dose of neuromedin U. Intravenously administered NMU (0.5 nmol) elicited a small and short lasting increase in MAP, compared to that by i.c.v. NMU. These results indicate that central neuromedin U regulates sympathetic nervous system activity and affects cardiovascular function. 相似文献
982.
Kazuo Sasaki Tatsuaki Ishise Koichiro Shimomura Toshihiro Kobayashi Yoshikatsuo Matsubayashi Youji Sakagami Hironori Umetsu Hiroshi Kamada 《Plant Growth Regulation》2002,36(1):87-90
Phytosulfokine (PSK)- is a sulphated pentapeptide, isolated fromthe medium of cultured Asparagus officinalis mesophyllcells, that promotes cell proliferation. It is a putative key factor inconditioned medium required for the growth of low-density plant cell cultures.The present study investigates the effect of PSK- on growth and tropanealkaloid production in Atropa belladonna hairy rootstransformed with Agrobacterium
rhizogenes (MAFF 03-01724). Although the growth rates ofhairy roots cultured in medium with orwithout PSK- for 4 weeks did not show any differences, the productivityof tropane alkaloids, especially of hyoscyamine, was enhanced by10–7 or 10–8 M PSK-. Inaddition, the content of tropane alkaloids in transformed roots treated withPSK- was 1.4 times higher than that of untreated roots after 4 weeks ofculture. The time course of growth and tropane alkaloid production inAtropa belladonna transformed roots suggested thatPSK- influenced the growth of transformed roots during the activegrowingphase, but not tropane alkaloid production. 相似文献
983.
BACKGROUND: The polymorphic forms of silica (silicon dioxide; SiO(2)) interact with the cell membranes of many mammalian cells, including red blood cells (RBCs), causing hemolysis. The electrostatic factor, which is believed to be a major contributor to the silica-cell contact, might have potential interest for the study of cell surface properties. The surface properties of SiO(2) particles are also of interest. METHODS: Washed human RBCs interacted with the particles of highly dispersed fumed silica (Aerosil A-300) and silicas (nine samples) obtained from the initial A-300 by its dehydroxylation at various thermal conditions. Their light scatter (forward and side light scatter) in 0.01% silica solution was measured uninterruptedly within the first 5 min of the reaction by flow cytometry (flow erythrogram). The hemolytic effect of SiO(2) particles was evaluated by photometric measurement of hemoglobin in the supernatant 90 min after the reaction. RESULTS: Light scatter of affected RBCs and the degree of hemolysis revealed that the surface properties of SiO(2) particles had various effects on the RBCs. After thermal reduction of the surface hydroxyl groups, the membranotoxic effect of silica increased and then decreased. CONCLUSIONS: RBCs offer a convenient and informative model for examining the surface properties of silica. 相似文献
984.
The present status of our understanding of the feedback regulation of pancreatic secretion by peptide YY (PYY) released from the distal intestine is reviewed. Exocrine pancreatic secretion is primarily controlled by the cephalic (the vagus nerve), gastric (acid and pepsin secretion, and nutrients delivered into the duodenum by gastric emptying), and intestinal (secretin and CCK) mechanisms. PYY acts on the multiple sites in the brain and gut, and inhibits pancreatic secretion by regulating these primary control mechanisms. The involvement of Y(1) and Y(2) receptors has been suggested in the regulation of pancreatic secretion. However, it remains to be studied which site of action or receptor subtype is physiologically most important for this regulation. 相似文献
985.
Uchiyama S Hasegawa J Tanimoto Y Moriguchi H Mizutani M Igarashi Y Sambongi Y Kobayashi Y 《Protein engineering》2002,15(6):455-462
Thermal stability was measured for variants of cytochrome c-551 (PA c-551) from a mesophile, Pseudomonas aeruginosa, and a thermophilic counterpart, Hydrogenobacter thermophilus cytochrome c-552 (HT c-552), by differential scanning calorimetry (DSC) at pH 3.6. The mutated residues in PA c-551, selected with reference to the corresponding residues in HT c-552, were located in three spatially separated regions: region I, Phe7 to Ala/Val13 to Met; region II, Glu34 to Tyr/Phe43 to Tyr; and region III, Val78 to Ile. The thermodynamic parameters determined indicated that the mutations in regions I and III caused enhanced stability through not only enthalpic but also entropic contributions, which reflected improved packing of the side chains. Meanwhile, the mutated region II made enthalpic contributions to the stability through electrostatic interactions. The obtained differences in the Gibbs free energy changes of unfolding [Delta(DeltaG)] showed that the three regions contributed to the overall stability in an additive manner. HT c-552 had the smallest heat capacity change (DeltaC(P)), resulting in higher DeltaG values over a wide temperature range (0-100 degrees C), compared to the PA c-551 variants; this contributed to the highest stability of HT c-552. Our DSC measurement results, in conjunction with mutagenesis and structural studies on the homologous mesophilic and thermophilic cytochromes c, provided an extended thermodynamic view of protein stabilization. 相似文献
986.
Grit,a GTPase-activating protein for the Rho family,regulates neurite extension through association with the TrkA receptor and N-Shc and CrkL/Crk adapter molecules 总被引:6,自引:0,他引:6
下载免费PDF全文
![点击此处可从《Molecular and cellular biology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Nakamura T Komiya M Sone K Hirose E Gotoh N Morii H Ohta Y Mori N 《Molecular and cellular biology》2002,22(24):8721-8734
Neurotrophins are key regulators of the fate and shape of neuronal cells and act as guidance cues for growth cones by remodeling the actin cytoskeleton. Actin dynamics is controlled by Rho GTPases. We identified a novel Rho GTPase-activating protein (Grit) for Rho/Rac/Cdc42 small GTPases. Grit was abundant in neuronal cells and directly interacted with TrkA, a high-affinity receptor for nerve growth factor (NGF). Another pool of Grit was recruited to the activated receptor tyrosine kinase through its binding to N-Shc and CrkL/Crk, adapter molecules downstream of activated receptor tyrosine kinases. Overexpression of the TrkA-binding region of Grit inhibited NGF-induced neurite elongation. Further, we found some tendency for neurite promotion in full-length Grit-overexpressing PC12 cells upon NGF stimulation. These results suggest that Grit, a novel TrkA-interacting protein, regulates neurite outgrowth by modulating the Rho family of small GTPases. 相似文献
987.
Three new species of the genus Gammarus are described from Lijiang, Yunnan Province, South China. Gammarus elevatus sp. nov. is characterized by mid-dorsal keel on pleonites 1-3 and compressed elevation on urosomites 1-2; G. denticulatus sp. nov. by many small spinules and setae on pleonites 1-3; G. stagnarius sp. nov. by lack of calceoli on antenna 2 and shorter inner ramus of uropod 3. These amphipods are compared with other known Gammarus species from China. 相似文献
988.
Washio H 《Zoological science》2002,19(2):153-162
Effects of application of glutamate and glutamatergic ligands were studied to characterize the receptors for glutamate present on the soma membrane of the dorsal unpaired median (DUM) neurons in the thoracic ganglia of the cockroach, Periplaneta americana, using the intracellular recording technique. Application of L-glutamate did not block the GABA-response, and application of beta-guanidino-propionic acid, a competitive antagonist for GABA, failed to block the response to L-glutamate. These results indicate that most of L-glutamate action may not be mediated by a GABA-activated channel. To examine glutamate receptor types on the DUM neurons, glutamate receptor agonists were applied. The ionotropic glutamate receptor (iGluR) agonists evoked depolarizations with the following relative rank of order of potency: kainate > AMPA > quisqualate. Metabotropic glutamate receptor (mGluR) agonists also elicited membrane depolarizations or hyperpolarizations associated with an increase in membrane conductance. The mGluR agonists evoked depolarizations or hyperpolarizations with the following relative rank of order: L-CCG-1 > 1S, 3R-ACPD > L-AP4. Depolarization of the same DUM neuron was detected following exposure of kainate and L-CCG-I, suggesting the coexistence of distinct iGluR and mGluR types. A membrane permeable cAMP analog, CPT-cAMP, could not mimic the effect of mGluR agonists. The mGluR selective antagonists, MCCG and MCPG, failed to antagonize the response to mGluR agonists. The involvement of cAMP in the mGluR response was not confirmed in DUM neurons. Although the functional roles of these receptors are unknown, it might be possible then that these extrasynaptic receptors have a modulatory effect on the excitability of the DUM neurons. 相似文献
989.
Shikazono N Tanaka A Kitayama S Watanabe H Tano S 《Radiation and environmental biophysics》2002,41(2):159-162
To clarify the effect of heavy ions in plants, dry seeds of Arabidopsis were irradiated with carbon, neon, and argon ions with various linear energy transfer (LET) values. The relative biological effectiveness (RBE) for lethality peaked at LET values over 350 keV/microns for neon and argon ions. This LET giving the peak RBE was higher than the LET of 100-200 keV/microns which was reported to have a maximum RBE for other types of cells, such as mammalian cells. Furthermore, sterility showed a higher RBE at an LET of 354 keV/microns with neon ions than that at an LET of 113 keV/microns with carbon ions. Lethality and sterility are both considered to be caused by damage to DNA. The results indicate that the LET having a maximum of RBE for lethality is higher in Arabidopsis seeds than in other unicellular systems. The most likely explanation for this shift of LET is that the DNA in dry seeds has a different chemical environment and/or hydration state than the DNA in cells in culture. 相似文献
990.
Rong S Ikeda H Sato Y Hirohashi Y Takamura Y Sahara H Sato T Maeda A Ohguro H Sato N 《Cancer immunology, immunotherapy : CII》2002,51(5):282-290
Recoverin is a photoreceptor-specific calcium binding protein that is only expressed in the retina in normal tissues. Aberrant expression of recoverin, however, has been observed in several cancer tissues and may cause a very rare autoimmune disease, cancer-associated retinopathy (CAR). It has been suggested that CAR-positive cancer patients have a more favorable prognosis than CAR-negative cancer patients. To estimate the status of recoverin-specific T cells in such cancer patients, we generated an HLA-A24-recoverin peptide tetramer. By use of the tetramer, we could directly assess the frequency of CTL precursors (CTLp) of 20 HLA-A24(+) cancer patients with ten colon, six stomach and four breast cancers, and seven healthy individuals. Four cancer patients showed a CTLp frequency higher than 0.9%. Seven cancer patients including the former four patients and two healthy individuals showed specific anti-recoverin cytotoxic responses in an HLA-A24-restricted manner after in vitro stimulation with the recoverin peptide. Moreover, five cancer patients analyzed in an independent experiment using different peripheral blood mononuclear cells (PBMC) samples showed similar CTLp and cytotoxic T lymphocyte (CTL) frequencies and cytotoxic responses, suggesting that the CTLp frequency analyzed by the tetramer and the cytotoxic response may have a good correlation. Thus, we hypothesize that anti-recoverin CTLp may exist in some cancer patients, and that anti-recoverin CTL may be readily induced. 相似文献