全文获取类型
收费全文 | 5325篇 |
免费 | 365篇 |
国内免费 | 1篇 |
出版年
2023年 | 22篇 |
2022年 | 22篇 |
2021年 | 157篇 |
2020年 | 90篇 |
2019年 | 103篇 |
2018年 | 160篇 |
2017年 | 118篇 |
2016年 | 159篇 |
2015年 | 236篇 |
2014年 | 303篇 |
2013年 | 373篇 |
2012年 | 432篇 |
2011年 | 451篇 |
2010年 | 268篇 |
2009年 | 244篇 |
2008年 | 306篇 |
2007年 | 349篇 |
2006年 | 312篇 |
2005年 | 270篇 |
2004年 | 241篇 |
2003年 | 241篇 |
2002年 | 206篇 |
2001年 | 53篇 |
2000年 | 47篇 |
1999年 | 46篇 |
1998年 | 45篇 |
1997年 | 33篇 |
1996年 | 23篇 |
1995年 | 38篇 |
1994年 | 27篇 |
1993年 | 33篇 |
1992年 | 27篇 |
1991年 | 20篇 |
1990年 | 25篇 |
1989年 | 16篇 |
1988年 | 13篇 |
1987年 | 11篇 |
1986年 | 14篇 |
1985年 | 15篇 |
1984年 | 16篇 |
1983年 | 12篇 |
1982年 | 14篇 |
1981年 | 12篇 |
1979年 | 11篇 |
1977年 | 13篇 |
1976年 | 8篇 |
1975年 | 8篇 |
1974年 | 5篇 |
1972年 | 5篇 |
1970年 | 7篇 |
排序方式: 共有5691条查询结果,搜索用时 23 毫秒
51.
Conclusion Membrane association is essential for GRK function and because of this the GRKs have evolved complex regulatory mechanisms
for associating with the membrane. Although the GRKs are highly homologous, each kinase utilizes a distinct mechanism for
associating with the membrane, which makes it unique within the family. Initially, the carboxyl terminus of the GRKs was identified
as the “membrane association domain” but recent evidence suggests that the amino terminus may also play a critical role in
localizing the kinases to the membrane (Murga et al., 1996; Pitcher et al, 1996). It is within these two domains that the
GRKs are most variable at the amino acid level. The GRKS exhibit an absolute requirement for phospholipids not only for association
with the membrane but also for activity. There are differences in preference and binding sites for the phospholipids within
the GRK family, which may reflect differential targeting of the GRKs to G protein-coupled receptors situated in different
lipid environments. There are hundreds of G protein-coupled receptors and only six known GRKs. All the GRKs appear to phosphorylate
the same receptor substrates in vitro (Sterne-Marr & Benovic, 1995; Premont et al., 1995). Receptor specificity, in a cellular 相似文献
52.
Eréndira Vargas Sergio Gutiérrez Ma. Elena Ambriz Carlos Cervantes 《Antonie van Leeuwenhoek》1995,68(3):225-229
NinePseudomonas strains were selected by their high copper tolerance from a population of bacteria isolated from heavy-metal polluted zones. Copper resistance (Cu
r
) was inducible by previous exposure of cultures to subinhibitory amounts of copper sulfate. All nine strains possessed large plasmids, but transformation and curing results suggest that Cu
r
is conferred by chromosomal genes. Plasmid-lessPseudomonas aeruginosa PAO-derived strains showed the same level of Cu
r
as environmental isolates and their resistance to copper was also inducible. Total DNA from the environmentalPseudomonas, as well as fromP. aeruginosa PAO strains, showed homology to a Cu
r
P. syringae cop probe at low-stringency conditions but failed to hybridize at high-stringency conditions. 相似文献
53.
Sergio Grinstein Wendy Furuya 《Biochimica et Biophysica Acta (BBA)/Molecular Cell Research》1984,803(4):221-228
The site and mechanism of accumulation of acridine derivatives into platelets and their isolated organelles were investigated. In addition, their suitability as indicators of cytoplasmic pH was analysed. Direct microscopic observation showed that quinacrine and 9-aminoacridine are concentrated inside organelles in platelets. Using fractionation studies, the acridine derivatives were found to accumulate particularly in dense and α-granules. Uptake into these organelles is driven by a pH differential across their membrane (acidic inside). Because of their cellular distribution, acridine derivatives were found to be poor indicators of cytoplasmic pH. In contrast, a poorly permeant dicarboxylated fluorescein derivative, generated in situ by cytosolic enzymes, is shown to be a more reliable probe of intracellular pH. The results are compared with previous reports of the use of 9-aminoacridine as a cytoplasmic pH probe in platelets and of quinacrine as a selective dense-granule marker. 相似文献
54.
Sergio Casella Robert R. Gault Kenneth C. Reynolds John R. Dyson John Brockwell 《FEMS microbiology letters》1984,22(1):37-45
Abstract Symbiotic experiments in glasshouse, controlled environment cabinet, and field were conducted with four lines of sulla ( Hedysarum coronarium ) and 15 strains of Rhizobium spp. This plant is highly Rhizobium -specific and appropriate strains are most unlikely to occur naturally in Australia. Under several sets of experimental conditions, H. coronarium nodulated abundantly and effectively with homologous rhizobia introduced from Spain and Italy. The optimum temperature for nitrogen fixation was relatively low (approx. 21°C) but significant interactions between line of host, strain of rhizobia, and growth temperature were frequent. The rhizobia were persistent in soil. 相似文献
55.
Summary We have compared some features of the resting and the insulin-stimulated uptake of -aminoisobutyrate (AIB) in frog skeletal muscle. We found a substantial difference between the two processes, namely, that resting AIB uptake is Na-independent while the insulin-stimulated fraction of the AIB uptake is Na-dependent.Since the amino acid transport systems in frog skeletal muscle are poorly characterized, we have also surveyed some of their properties. One of the most interesting findings of this survey is that both the uptake and efflux of AIB are inhibited by low concentrations of PCMBS (parachloro-mercury-benzene sulfonic acid 5×10–5
m). In contrast, the carrier mediated transport of basic amino acids is neither inhibited by this mercurial agent nor accelerated by insulin.The action of PCMBS strongly suggests the presence of a critical sulfhydryl group in the amino acid carrier system utilized by AIB. This group is exposed to the outside solution since PCMBS penetrates cell membranes poorly, and in addition its inhibitory actions were reverted by agents that do not penetrate the cell membrane like albumin or glutathione. 相似文献
56.
Daniela Cocchi Angela Santagostino Irit Gil-Ad Sergio Ferri Eugenio E. Müller 《Life sciences》1977,20(12):2041-2046
The effect of Leu5-enkephalin on growth hormone (GH) and prolactin (PRL) release was studied in the infant rat and compared to that of morphine. In 10 day-old pups, intracerebroventricular injection of Leu5-enkephalin (50, 75 and 100 μg) resulted in a dose-related increase in plasma GH; morphine was active as GH releaser at the dose of 5 and 10 μg, but not at 2.5 μg. Pretreatment with naloxone (2 mg/kg ip) suppressed the GH-releasing effect of either Leu5-enkephalin (100 μg) or morphine (10 μg). Leu5-enkephalin (75 and 100 μg) induced a rise in plasma PRL which was neither dose-related nor antagonized by naloxone; morphine (5 and 10 μg) was active as PRL releaser and its effect was antagonized by naloxone. These results indicate that: 1) Leu5-enkephalin stimulates both GH and PRL release; 2) the release of GH by Leu5-enkephalin but likely not that of PRL involves specific opiate receptors; 3) morphine releases GH and PRL through specific opiate receptors. 相似文献
57.
58.
Natale Cascinelli Gian Paolo Balzarini Vincenzo Fontana Sergio Orefice Umberto Veronesi 《Cancer immunology, immunotherapy : CII》1977,2(3):157-161
Summary From November 1973 to December 1974, 20 patients with advanced malignant melanoma were treated with BCG given by intralymphatic route at the Cancer Institute of Milan. The lyophilized Pasteur BCG was used. Patients were treated with a single dose ranging from 0.2–80 mg. Patients' performance status was never severely impaired.The most frequent side effects were fever, lymphangitis, and lymph node enlargement.Variations were observed in white cell count, ERS and immunoglobulins; in no case did we find evidence of liver toxicity or tumor growth enhancement. It is concluded that the intralymphatic route is a safe way of administrating BCG. 相似文献
59.
Calmodulin copurifies with platelet plasma membranes isolated by glycerol-induced lysis and density gradient centrifugation. These membranes also bind 125I-labeled calmodulin in vitro in the presence of Ca2+. Binding is largely reduced by replacing Ca2+ by Mg2+ or by addition of an excess unlabeled calmodulin. The specific component of binding is saturable, with an apparent Kd of 27 nM and a maximum of 15.9 pmol binding sites per mg of membrane protein. This is equivalent to approx. 4100 binding sites per platelet. Binding was inhibited by addition of phenothiazines, a group of calmodulin antagonists. Half-maximal inhibition was attained with approx. 20 μM trifluoperazine or 50 μM chlorpromazine. In contrast, chlorpromazine-sulfoxide which is inactive towards calmodulin, did not affect the binding. Calmodulin binding polypeptides of the plasma membrane were identified by a gel-overlay technique. A major calmodulin-binding component of molecular weight 149 000 was detected. Binding to this band was Ca2+-dependent and inhibited by chlorpromazine. The molecular weight of this polypeptide is similar to that of glycoprotein I and also that of the red cell (Ca2+ + Mg2+)-stimulated ATPase, which is known to bind calmodulin. The possible role of calmodulin in platelet activation is analysed. 相似文献
60.