全文获取类型
收费全文 | 5994篇 |
免费 | 449篇 |
国内免费 | 3篇 |
出版年
2023年 | 28篇 |
2022年 | 23篇 |
2021年 | 67篇 |
2020年 | 53篇 |
2019年 | 62篇 |
2018年 | 166篇 |
2017年 | 125篇 |
2016年 | 185篇 |
2015年 | 329篇 |
2014年 | 336篇 |
2013年 | 430篇 |
2012年 | 504篇 |
2011年 | 482篇 |
2010年 | 320篇 |
2009年 | 239篇 |
2008年 | 397篇 |
2007年 | 397篇 |
2006年 | 382篇 |
2005年 | 377篇 |
2004年 | 322篇 |
2003年 | 309篇 |
2002年 | 271篇 |
2001年 | 41篇 |
2000年 | 46篇 |
1999年 | 48篇 |
1998年 | 39篇 |
1997年 | 35篇 |
1996年 | 26篇 |
1995年 | 24篇 |
1994年 | 16篇 |
1993年 | 27篇 |
1992年 | 23篇 |
1991年 | 16篇 |
1990年 | 26篇 |
1989年 | 15篇 |
1988年 | 22篇 |
1987年 | 14篇 |
1986年 | 25篇 |
1985年 | 12篇 |
1984年 | 19篇 |
1983年 | 11篇 |
1982年 | 10篇 |
1981年 | 10篇 |
1979年 | 13篇 |
1978年 | 15篇 |
1977年 | 9篇 |
1974年 | 10篇 |
1973年 | 9篇 |
1969年 | 7篇 |
1968年 | 9篇 |
排序方式: 共有6446条查询结果,搜索用时 15 毫秒
11.
Satratoxins H and G, verrucarin J, and roridin E were isolated from the bedding straw of 200 sport horses exhibiting typical symptoms of stachybotryo-toxicosis. At the same time, the oat feed consumed by the horses contained non-macrocyclicFusarium trichothecenes: T-2 toxin and diacetoxyscirpenol. 相似文献
12.
Inhibition of electroshock-induced seizures by cholecystokinin-related peptides in mice 总被引:1,自引:0,他引:1
The effects of several doses of cholecystokinin octapeptide sulphate ester (CCK-8-SE) and nonsulphated cholecystokinin octapeptide (CCK-8-NS), and two CCK-related peptide analogues Ac-Thr5-caerulein, and nonsulphated Ac-Thr5-caerulein were investigated on electroshock-(ES)-induced seizures after intraperitoneal administration in mice. As parameters, the duration of the tonic and clonic phase of the fit, and those of postictal coma and behavioural depression were measured. CCK-8-SE decreased the duration of the clonic phase; its highest dose, 3.2 mumol/kg, shortened the coma. CCK-8-NS antagonized only slightly the clonic phase of seizure. Ac-Thr5-caerulein did not influence ES-induced seizures in any dose, only increased the duration of behavioural depression. Similarly to CCK-8-NS, the nonsulphated form of Ac-Thr5-caerulein inhibited selectively the clonic phase of seizures. The reference drugs, diazepam and phenobarbital, antagonized dose-dependently and most effectively the tonic phase of ES-induced seizures, but in much higher doses than did the CCK-related peptides. Besides, diazepam increased and phenobarbital decreased the duration of postictal coma. The results showed that the tested CCK-related peptides inhibit prevalently the clonic phase of ES-induced seizures after peripheral administration. 相似文献
13.
Bård Smedsrød Marie Malmgren Jan Ericsson Torvard C. Laurent 《Cell and tissue research》1988,253(1):39-45
Summary Endocytosis via the hyaluronic acid/chondroitin sulphate receptor of rat liver endothelial cells was studied ultrastructurally, by use of a probe consisting of chondroitin sulphate proteoglycan attached to 15-nm gold particles. The probe bound to the surface of the cells exclusively in coated regions of the plasma membrane. Internalization at 37° C took place in less than one minute during which time interval the bound probe was transferred to coated vesicles. Further transfer to lysosomes was delayed in association with an accumulation of probes in a prelysosomal compartment consisting of large vacuoles in which probes lined the inner aspect of the membrane. Transport to lysosomes occurred only after a lag phase of at least 40–60 min at 37° C.Abbreviations
CS
chondroitin sulphate
-
CSPG
chondroitin sulphate proteoglycan
-
CSPG-Au
CSPG-gold complex
-
EM
electronmicroscopical or electron microscopy
-
HA
hyaluronic acid
-
KC
Kuppfer cells
-
LEC
liver endothelial cells
-
PC
parenchymal cells
-
RES
reticuloendothelial system 相似文献
14.
15.
Adriaan P. de Bruïne Winand N. M. Dinjens Margriet M. J. Pijls Edith P. M. v. d. Linden Mat J. M. Rousch Peter T. Moerkerk Antony F. P. M. de Goeij Fred T. Bosnian 《Virchows Archiv. B, Cell pathology including molecular pathology》1992,62(1):311-320
In colonic neoplasms, endocrine differentiation is encountered not only in carcinoid tumors but also in adenocarcinomas, where
endocrine cells may represent a distinct line of differentiation in the tumor. The significance of endocrine differentiation
in colorectal cancer is not well established, partly because of the paucity of tumor cell lines which can serve as a model
for studying endocrine differentiation. In this report we describe the properties of NCI-H716 cells, a cell line derived from
a poorly differentiated adenocarcinoma of the caecum, under various in vitro conditions and as xenografts in athymic mice.
Phenotypical properties were immunohistochemically assessed using a panel of differentiation related antibodies, and also
by Northern blot analysis and by electron microscopy. Receptors for biogenic amines and peptide hormones were analyzed by
ligand binding assay. These studies show that:
相似文献
16.
Françoise Farace Anne-Marie Le Ridant Bernard Escudier Thierry Hercend Frédéric Triebel 《Biotherapy》1992,5(1):11-20
We have attempted to improve negative selection procedures for the large scale purification of human CD
in3
–
CD56+ NK cells. In a series of experiments, purifications of NK cells from 108 PBMC were performed by T cell depletion using either direct or indirect anti-CD3 labeling and the Magnetic Activated Cell Separation (MACS) procedure. Contaminating CD3+ cells were still present using either one of these two different T cell depletion protocols as shown by phenotyping IL-2 supplemented cell cultures on day 12. A second cycle of purification was therefore added. When MACS and Dynabeads were compared as complementary procedures to the first MACS cycle starting with 108 cells, the Dynabeads method was found to be superior to the MACS with regard to the elimination of residual T cells. Starting from 109 PBMC, we showed that this MACS+Dynabeads procedure gave similar satisfactory results when compared to the scaling-up of a previously established two steps procedure using Dynabeads. These two approaches (MACS+Dynabeads and 2 cycles of Dynabeads) have been also tested in a clinical setting to purify NK cells from cancer patients prior toin vitro expansion. The results indicate that the two methods are equivalent with respect to purity and recovery rate; a slight advantage in terms of feasibility was found in favor of 2 cycles of Dynabeads. 相似文献
17.
Human cumuli-oophori were cultured in vitro in the presence of radioactive protein and polysaccharide precursors. The time course of the cumulus cell secretion was traced by histoautoradiography. Matrix solubilization, and sodium dodecyl sulphate polyacrylamide gel electrophoresis and high-performance liquid chromatography showed that proteoglycan (Mr greater than 1,700,000) was the main cumulus cell product that was prevailingly deposited in the cumulus intercellular matrix and partly released into the culture medium. It was capable of accelerating the conversion of proacrosin to acrosin and this activity was abolished by enzymatic removal of chondroitin sulphate, the predominant glycosaminoglycan of this proteoglycan fraction. None of the other fractions, including a proteoglycan of Mr 80,000-90,000, containing heparan sulphate, accelerated the conversion of proacrosin to acrosin under the conditions used. The results suggest that chondroitin sulphate is the active component of the high-Mr proacrosin activator of the human cumulus-oophorus. 相似文献
18.
Marie-Hélène Avelange Jean M. Thiéry Frédéric Sarrey Pierre Gans Fabrice Rébeillé 《Planta》1991,183(2):150-157
In order to estimate photosynthetic and respiratory rates in illuminated photoautotrophic cells of carnation (Dianthus caryophyllus L.), simultaneous measurements of CO2 and O2 gas exchange were performed using 18O2, 13CO2 and a mass-spectrometry technique. This method allowed the determination, and thus the comparison, of unidirectional fluxes of O2 and CO2. In optimum photosynthetic conditions (i.e. in the presence of high light and a saturating level of CO2), the rate of CO2 influx represented 75±5% of the rate of gross O2 evolution. After a dark-to-light transition, the rate of CO2 efflux was inhibited by 50% whereas the O2-uptake rate was little affected. The effect of a recycling of respiratory CO2 through photosynthesis on the exchange of CO2 gas was investigated using a mathematical model. The confliction of the experimental data with the simulated gas-exchange rates strongly supported the view that CO2 recycling was a minor event in these cells and could not be responsible for the observed inhibition of CO2 efflux. On the basis of this assumption it was concluded that illumination of carnation cells resulted in a decrease of substrate decarboxylations, and that CO2 efflux and O2 uptake were not as tightly coupled in the light as in the dark. Furthermore, it could be calculated from the rate of gross photosynthesis that the chloroplastic electron-transport chain produced enough ATP in the light to account for the measured CO2-uptake rate without involving cyclic transfer of electrons around PS I or mitochondrial supplementation.Abbreviations Chl
chlorophyll
- Kd
permeability coefficient
The authors thank Drs A. Vermeglio and P. Thibault, Dépt. de Biologie, CEN-Cadarache, St. Paul Lez Durance, France, for helpful discussions. 相似文献
19.
20.
Bård Smedsrød Håkan Pertoft Gösta Eggertsen Christer Sundström 《Cell and tissue research》1985,241(3):639-649
Summary This paper presents a study on the structure and function of Kupffer cells (KC) and liver endothelial cells (LEC) isolated by a simple and rapid technique involving 1) perfusion of the liver with collagenase; 2) cell separation by means of density centrifugation in Percoll; and 3) cell culture, taking advantage of the fact that KC and LEC differ in their preferences for growth substrate. The KC, which attach and spread under serum-free conditions on surfaces of glass or plastic during the first 15 min in culture exhibit a typical macrophage-like morphology including membrane ruffling and a heterogenous content of vacuoles. Moreover, these cells express (a) Fc receptors (FcR) for binding and phagocytosis of erythrocytes covered with immune globulin G (E-IgG), and (b) complement receptors (CR) for binding and serum dependent phagocytosis of erythrocytes covered with either human C3b or mouse inactivated C3b (iC3b). The cells also bind fluid phase fluoresceinated C3b. Approximately 30% of the KC express immune response-associated (Ia)-antigens.The LEC attach and spread on fibronectin coated surfaces, but not on glass or plastic surfaces, during the first two hours in culture with or without serum, and are morphologically distinct from KC. Cultured LEC are well spread out with no membrane ruffling and with numerous large vesicles surrounding the regularly shaped nucleus. These cells bind, but do not ingest E-IgG via the FcR, but no binding of fluid phase C3b or particle fixed C3b or iC3b can be observed. Incubation of LEC with fluorescein amine conjugates of ovalbumin or formaldehyde treated serum albumin, but not with fluoresceinated native serum albumin, results in accumulation of fluorescence specifically localized in the large perinuclear vesicles. Neither KC nor any other cell types tested have the ability to accumulate fluorescence upon incubation with these compounds. Iaantigens are not present on the LEC.Cytochemical demonstration of unspecific esterase, acid phosphatase, and peroxidase reveals different patterns and intensities of staining in KC as compared to LEC.Abbreviations Used
KC
Kupffer cells
-
LEC
Liver endothelial cells
-
C
Complement
-
C3b
Major fragment of C3 activation
-
iC3b
C3b that has been cleaved by factor I (C3b inactivator), present in serum
-
meC3b
C3b produced by treating purified human C3 with methyl amine
-
trC3b
C3b produced by treating purified human C3 with trypsin
-
CR
Complement receptors for C3b and iC3b
-
IgG
Immune globulin G
-
IgM
Immune globulin M
-
E
Erythrocytes
-
E-IgG
E covered with anti-E IgG
-
E-IgM E
covered with anti-E IgM
-
E-C3b(h)
E-IgM reacted with purified human C1, C4, oxidized C2 and C3 (E-IgMC14xyC2C3b)
-
E-iC3b(m)
E-IgM incubated with C5 deficient serum from AKR mice
-
FcR
Receptors for the Fc portion of IgG
-
FITC
Fluorescein isothiocyanate
-
FITC-meC3b
FITC conjugated to meC3b
-
FITC-trC3b
FITC conjugated to trC3b
-
FA
Fluorescein amine
-
FA-OA
Ovalbumin conjugated with FA
-
FA-SA
Serum albumin conjugated with FA
-
FA-FSA
Formaldehyde-treated serum albumin conjugated with FA
-
Ia
Immune response-associated AcE Acid unspecific esterase acting on alpha naphtyl acetate
-
NASDAE
Unspecific esterase acting on naphthol AS-D acetate
-
NASDCAE
Unspecific esterase acting on napthol AS-D chloroacetate 相似文献