全文获取类型
收费全文 | 10929篇 |
免费 | 859篇 |
国内免费 | 6篇 |
出版年
2023年 | 68篇 |
2022年 | 140篇 |
2021年 | 283篇 |
2020年 | 156篇 |
2019年 | 282篇 |
2018年 | 315篇 |
2017年 | 279篇 |
2016年 | 404篇 |
2015年 | 626篇 |
2014年 | 642篇 |
2013年 | 831篇 |
2012年 | 961篇 |
2011年 | 905篇 |
2010年 | 562篇 |
2009年 | 540篇 |
2008年 | 652篇 |
2007年 | 664篇 |
2006年 | 561篇 |
2005年 | 505篇 |
2004年 | 446篇 |
2003年 | 402篇 |
2002年 | 369篇 |
2001年 | 96篇 |
2000年 | 62篇 |
1999年 | 84篇 |
1998年 | 93篇 |
1997年 | 67篇 |
1996年 | 61篇 |
1995年 | 68篇 |
1994年 | 62篇 |
1993年 | 43篇 |
1992年 | 60篇 |
1991年 | 45篇 |
1990年 | 28篇 |
1989年 | 44篇 |
1988年 | 27篇 |
1987年 | 28篇 |
1986年 | 28篇 |
1985年 | 31篇 |
1984年 | 19篇 |
1983年 | 27篇 |
1982年 | 14篇 |
1980年 | 19篇 |
1979年 | 24篇 |
1978年 | 15篇 |
1977年 | 15篇 |
1974年 | 16篇 |
1971年 | 13篇 |
1969年 | 13篇 |
1968年 | 13篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
111.
Bricchi Emma Frenguelli Giuseppe Mincigrucci Gianfranco Fornaciari Marco Ferranti Francesco Romano Bruno 《Aerobiologia》1995,11(1):57-61
Times of pollination of different taxa in the atmosphere of Perugia (Central Italy) over an 11-year period (1982–1992) were recorded and analysed by means of a 7-day volumetric Hirst-type pollen trap. For some taxa, the pollination period varied from year to year from a chronological and/or quantitative point of view. Several taxa showed a linkage in their starting dates of pollination. Knowledge of this kind of linkage allows us to build a forecasting model. 相似文献
112.
Francesca Cappa Gianluca Caridi Giorgio Gimelli Gian Marco Ghiggeri 《Human genetics》1995,95(5):599-600
A cDNA probe of the human COL5A1 gene detects a frequent biallelic PstI polymorphism. Allele A has a frequency of 54% whereas that of allele B is 46%. This restriction fragment length polymorphism provides a useful marker for linkage analysis in 9q34.3. 相似文献
113.
Maurizio Meta Marco Ponte Marina Guastella Claudia Semino Gabriella Pietra Giovanni Battista Ratto Giovanni Melioli 《Cancer immunology, immunotherapy : CII》1995,40(4):235-240
Despite the combined use of surgery and chemoradiotherapy, the poor prognosis of advanced non-smallcell lung cancer (NSCLC) requires the definition of new therapeutic approaches. The presence of T lymphocytes, with peculiar phenotypic, functional and molecular characteristics within the tumour, suggested the possible use of these cells, expanded in vitro, in protocols of adoptive immunotherapy. We have described how a population of oligoclonal T lymphocytes, derived from advanced NSCLC, can be expanded in vitro and has the capability of lysing autologous cancer cells. What is more important, we observed that patients with advanced NSCLC, treated with TIL expanded in vitro and recombinant interleukin-2, seemed to have a disease-free period longer than that of patients treated with conventional chemoradiotherapy. in an attempt to find new sources of specific lymphocytes for immunotherapy, we describe the analysis of the phenotypic, functional and molecular characteristics of T lymphocytes, derived from lymph nodes draining advanced NSCLC. In this paper we show that these cells, have restriction patterns of T cell receptor chain similar to those detectable in the population of infiltrating T lymphocytes. This finding suggests that T cells derived from draining lymph nodes of advanced NSCLC have peculiar characteristics and can be a suitable source of effector cells for protocols of adoptive immunotherapy in lung cancer treatment. 相似文献
114.
Antibodies were raised in rabbits against the outer membrane of Neurospora mitochondria. Antibodies were obtained that were specific for this membrane's major polypeptide () and its slower-migrating derivatives on SDS-polyacrylamide gels. These antibodies inhibited the insertion into phospholipid bilayers of voltage-dependent ion channels from detergent extracts of the mitochondrial outer membranes. The same antibodies bound preferentially to membranes containing crystalline surface arrays in outer mitochondrial membrane fractions. These results indicate that the 31 kDa polypeptide is a component both of the ion channels and of the membrane arrays, suggesting identity between the functional and structural entities. 相似文献
115.
Lipid composition of brain myelin from normal and hyperphenylalaninemic chick embryos 总被引:1,自引:0,他引:1
M J Alejandre C Marco H Ramirez J L Segovia E Garcia-Peregrin 《Comparative biochemistry and physiology. B, Comparative biochemistry》1984,77(2):329-332
The influence of hyperphenylalaninemia on the lipid composition of brain myelin has been investigated in 19-day-old chick embryos. CNP-ase activity was used as myelin marker enzyme for myelin isolation. CNP-ase activity was significantly lower in hyperphenylalaninemic myelin when compared with control. No significant differences were observed after experimental treatment in the total lipid content of myelin as well as in the proportion of cholesterol:phospholipid:galactolipid. Nevertheless, a clear increase in the percentage of esterified cholesterol was found. No appreciable alterations were observed in the phospholipid composition of brain myelin from both control and hyperphenylalaninemic chick embryos. However, the ratio of unsaturated to saturated fatty acids in serine plasmalogen and sphingomyelin was considerably increased by this treatment. This ratio in choline and ethanolamine phosphatides from treated embryos did not differ from that of controls. 相似文献
116.
117.
Tannic acid impregnation has revealed the existence of a T-system in the helical fibers of Branchiobdella pentodonta (Annelida, Clitellata). T-tubules are L-shaped inside the fiber, within the plane of the I-band: after a short horizontal tract they run longitudinally for a long tract keeping contact with many sarcoplasmic reticulum cisternae and forming dyads. The presence of a T-system in this annelid, the only one demonstrated up to now in annelids, is to be ascribed to the thickness of the contractile layer of those fibers. 相似文献
118.
Antonio De Marco Harald Tschesche Gerhard Wagner Kurt Wüthrich 《European biophysics journal : EBJ》1977,3(3-4):303-315
In the 1H NMR spectra obtained at 360 MHz after digital resolution enhancement, the multiplet resonances of the methyl groups in the basic pancreatic trypsin inhibitor (BPTI) were resolved. With suitable double irradiation techniques the individual methyl resonances were assigned to the different types of aliphatic amino acid residues. Furthermore, from pH titration and comparison of the native protein with chemically modified BPTI, the resonance lines of Ala 16 in the active site and Ala 58 at the C-terminus were identified. Potential applications of the resolved methyl resonances as natural NMR probes for studies of the molecular conformations are discussed. 相似文献
119.
Enkephalin-binding systems in human plasma 总被引:1,自引:0,他引:1
Roberta Possenti Valeria De Marco Ornella Cherubini L. Giorgio Roda 《Neurochemical research》1983,8(4):423-432
Three amino acid-containing fractions present in human plasma are shown to bind both leu and met-enkephalin: serum albumin and two species of a much lower molecular weight, in all likelihood polypeptides. The amount of enkephalin associated with serum albumin seems comparatively smaller than that associated with the two low molecular weight systems. These systems jointly are apparently capable of binding a significant part of the circulating enkephalins. The possibility is suggested that the interactions described may play a role in maintaining the integrity of circulating enkephalins. 相似文献
120.
Joyce M. Fisher Marco Rabinovitz 《Biochemical and biophysical research communications》1982,104(2):851-853
A specific copper chelator, 2,9-dimethyl-4,7-diphenyl-1,10-phenanthrolinedisulfonic acid substituted for mercaptoethanol to support growth of a L1210 lymphoma in primary culture. Added Cu++, but not Zn++ or Fe++ interfered with growth promotion by the chelator. It also can protect an established L1210 culture, which does not require mercaptoethanol, from cytotoxicity of two bis-thiosemicarbazones. Since these are known to require copper for cytotoxicity, the results indicate that 2,9-dimethyl-4,7-diphenyl-1,10-phenanthrolinedisulfonic acid acts by removing a source of endogenous copper in the tissue culture medium which prevents growth of the primary culture. 相似文献