全文获取类型
收费全文 | 8203篇 |
免费 | 612篇 |
国内免费 | 33篇 |
专业分类
耳鼻咽喉 | 81篇 |
儿科学 | 118篇 |
妇产科学 | 230篇 |
基础医学 | 1069篇 |
口腔科学 | 228篇 |
临床医学 | 915篇 |
内科学 | 1764篇 |
皮肤病学 | 165篇 |
神经病学 | 689篇 |
特种医学 | 724篇 |
外科学 | 1443篇 |
综合类 | 60篇 |
一般理论 | 1篇 |
预防医学 | 273篇 |
眼科学 | 161篇 |
药学 | 354篇 |
中国医学 | 2篇 |
肿瘤学 | 571篇 |
出版年
2023年 | 108篇 |
2022年 | 193篇 |
2021年 | 342篇 |
2020年 | 203篇 |
2019年 | 299篇 |
2018年 | 333篇 |
2017年 | 242篇 |
2016年 | 277篇 |
2015年 | 318篇 |
2014年 | 420篇 |
2013年 | 425篇 |
2012年 | 642篇 |
2011年 | 640篇 |
2010年 | 383篇 |
2009年 | 373篇 |
2008年 | 467篇 |
2007年 | 449篇 |
2006年 | 364篇 |
2005年 | 347篇 |
2004年 | 267篇 |
2003年 | 270篇 |
2002年 | 198篇 |
2001年 | 109篇 |
2000年 | 99篇 |
1999年 | 108篇 |
1998年 | 44篇 |
1997年 | 52篇 |
1996年 | 33篇 |
1995年 | 17篇 |
1994年 | 23篇 |
1993年 | 24篇 |
1992年 | 45篇 |
1991年 | 55篇 |
1990年 | 39篇 |
1989年 | 40篇 |
1988年 | 42篇 |
1987年 | 41篇 |
1986年 | 32篇 |
1985年 | 37篇 |
1984年 | 20篇 |
1983年 | 21篇 |
1982年 | 16篇 |
1981年 | 19篇 |
1979年 | 32篇 |
1978年 | 18篇 |
1975年 | 12篇 |
1974年 | 15篇 |
1972年 | 14篇 |
1932年 | 13篇 |
1924年 | 12篇 |
排序方式: 共有8848条查询结果,搜索用时 15 毫秒
21.
B. Persky C. C. Huerta M. J. Hendrix 《International journal of experimental pathology》1987,68(4):493-499
Subcutaneous tumours were induced in castrated golden Syrian hamsters by 7,12 dimethylbenz[a]anthracene (DMBA), an agent known to produce papillomas and carcinomas. The morphological characteristics of the cellular and extracellular constituents of the chemically-induced tumours were indicative of melanoma. Tumours were induced by three injections of DMBA into the jugular vein over a 3 month period. Dermal tumour development within the dorsal integument and groin region ultimately projected into the epidermis and occurred during the 3 month period subsequent to the last DMBA injection. Suspect melanoma tumours were excised and processed for light microscopic (LM) and transmission electron microscopic (TEM) studies. Histochemical staining methods facilitated the characterization of the differentiated tumour components in this hamster melanoma model. The model presented could allow observations from initial melanoma transformation events through advanced stages of metastasis within a window of 7 months. 相似文献
22.
23.
Molecular determinants of human uveal melanoma invasion and metastasis 总被引:19,自引:0,他引:19
Seftor EA Meltzer PS Kirschmann DA Pe'er J Maniotis AJ Trent JM Folberg R Hendrix MJ 《Clinical & experimental metastasis》2002,19(3):233-246
The molecular analysis of cancer has benefited tremendously from the sequencing of the human genome integrated with the science
of bioinformatics. Microarray analysis technology has the potential to classify tumors based on the differential expression
of genes. In the current study, a collaborative, multidisciplinary approach was utilized to study the molecular determinants
of human uveal melanoma invasion and metastasis. Uveal melanoma is considered the most common primary intraocular cancer in
adults, resulting in the death of approximately 50% of patients affected. Unfortunately, at the time of diagnosis, many patients
already harbor microscopic metastases, thus underscoring a critical need to identify prognostic markers indicative of metastatic
potential. The investigative strategy consisted of isolating highly invasive vs. poorly invasive uveal melanoma cells from
a heterogeneous tumor derived from cells that had metastasized from the eye to the liver. The heterogeneous tissue explant
MUM-2 led to the derivation of two clonal cell lines: MUM-2B and MUM-2C. Further morphological and functional analyses revealed
that the MUM-2B cells were epithelioid, interconverted (expressing mesenchymal and epithelial phenotypes) highly invasive,
and demonstrated vasculogenic mimicry. The MUM-2C cells were spindle-like, expressed only a vimentin mesenchymal phenotype,
poorly invasive, and were incapable of vasculogenic mimicry. The molecular analysis of the MUM-2B vs. the MUM-2C clones resulted
in the differential expression of 210 known genes. Overall, the molecular signature of the MUM-2B cells resembled that of
multiple phenotypes – similar to a pluripotent, embryonic-like genotype. Validation of select genes that were upregulated
and down-regulated was conducted by semiquantitative RT-PCR measurement. This study provides a molecular profile that will
hopefully lead to the development of new molecular targets for therapeutic intervention and possible diagnostic markers to
predict the clinical outcome of patients with uveal melanoma.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
24.
Dr. U. Cordes B. Braun M. Georgi F. Kümmerle V. Lenner E. Magin T. Philipp J. Beyer 《Journal of molecular medicine (Berlin, Germany)》1979,57(22):1209-1215
Zusammenfassung Bei sechs Patienten mit adrenalem Phäochromocytom erfolgte die Lokalisationsdiagnostik durch Ultraschalluntersuchung, Phlebographie der Nebennieren und selektiver Katecholaminbestimmung im Blut der Vena cava sowie der Nebennierenvenen. Durch die selektive Katecholaminbestimmung konnten alle Phäochromocytome lokalisiert werden, durch die Ultraschalluntersuchung fünf, durch die Phlebographie vier. Ein Phäochromocytom von 1,5 g Gewicht, das nur durch die selektive Katecholaminbe-stimmung, nicht aber durch Ultraschall oder Phlebographie lokalisiert wurde, konnte computertomographisch dargestellt werden.Um Fehldiagnosen bei der selektiven Katecholaminbestimmung zu vermeiden, darf vor der Blutentnahme aus den Nebennierenvenen kein Röntgenkontrastmittel injiziert werden, da dies zu einer erheblichen Adrenalin- oder Noradrenalinfreisetzung aus dem Nebennierenmark führen kann. 相似文献
25.
Cation channels,cell volume and the death of an erythrocyte 总被引:8,自引:0,他引:8
Lang F Lang KS Wieder T Myssina S Birka C Lang PA Kaiser S Kempe D Duranton C Huber SM 《Pflügers Archiv : European journal of physiology》2003,447(2):121-125
Similar to a variety of nucleated cells, human erythrocytes activate a non-selective cation channel upon osmotic cell shrinkage. Further stimuli of channel activation include oxidative stress, energy depletion and extracellular removal of Cl–. The channel is permeable to Ca2+ and opening of the channel increases cytosolic [Ca2+]. Intriguing evidence points to a role of this channel in the elimination of erythrocytes by apoptosis. Ca2+ entering through the cation channel stimulates a scramblase, leading to breakdown of cell membrane phosphatidylserine asymmetry, and stimulates Ca2+-sensitive K+ channels, thus leading to KCl loss and (further) cell shrinkage. The breakdown of phosphatidylserine asymmetry is evidenced by annexin binding, a typical feature of apoptotic cells. The effects of osmotic shock, oxidative stress and energy depletion on annexin binding are mimicked by the Ca2+ ionophore ionomycin (1 µM) and blunted in the nominal absence of extracellular Ca2+. Nevertheless, the residual annexin binding points to additional mechanisms involved in the triggering of the scramblase. The exposure of phosphatidylserine at the extracellular face of the cell membrane stimulates phagocytes to engulf the apoptotic erythrocytes. Thus, sustained activation of the cation channels eventually leads to clearance of affected erythrocytes from peripheral blood. Susceptibility to annexin binding is enhanced in several genetic disorders affecting erythrocyte function, such as thalassaemia, sickle-cell disease and glucose-6-phosphate dehydrogenase deficiency. The enhanced vulnerability presumably contributes to the shortened life span of the affected erythrocytes. Beyond their role in the limitation of erythrocyte survival, cation channels may contribute to the triggering of apoptosis in nucleated cells exposed to osmotic shock and/or oxidative stress. 相似文献
26.
Joachim Ktz Mathias Hahn Burkart Philipp Esen A. Bekturov Sarkyt E. Kudaibergenov 《Macromolecular chemistry and physics.》1993,194(2):397-410
Employing polyampholytes (inclusively polybetaines) of different chemical structure containing carboxylic groups and various basic nitrogen functions, homosymplex formation, as well as the competition between homo- and heterosymplex formation on addition of an appropriate polyelectrolyte, was investigated in dependence of pH and ionic strength by means of viscometry and turbidimetry. With most, but not with all, of the polyampholytes, the expected viscosity minimum at the isoelectric point, with its steepness depending on polyampholyte structure, was observed. Competition of homo- and heterosymplex formation at and near the isoelectric point is mainly governed by the pK values of the species involved, the level of zwitter-ion formation of the polyampholyte and the effect of non-Coulombic interactions, for example, via hydrogen bonds. 相似文献
27.
13C NMR spectroscopic studies on polyanion-polycation complexes and their component polyelectrolytes
Joachim Ktz Andreas Ebert Jürgen Kunze Burkart Philipp Johan Lindberg Kari Soljamo 《Macromolecular chemistry and physics.》1990,191(3):651-658
Position and intensities of the 13C NMR signals and relaxation times T1 of several anionic and cationic polyelectrolytes in the solid state were compared with those of the appropriate polyanion-polycation complexes. At a high charge density of the components, the most significant changes of the parameters in question due to complex formation are observed for the C atoms adjacent to the charge centers, indicating a strong Coulombic interaction. At lower charge density, conformational changes of the polymer chains have also to be taken into consideration. 相似文献
28.
C. de Wit Christian Schäfer Philipp von Bismarck Steffen-Sebastian Bolz Ulrich Pohl 《Pflügers Archiv : European journal of physiology》1997,434(4):354-361
We studied whether a flow-independent increase of luminal wall shear stress (WSS) could dilate hamster arterioles in vivo
and which endothelial mediators are potentially involved. To this end the plasma viscosity was elevated by exchanging blood
for dextran-erythrocyte solution thereby augmenting WSS. Diameters of small and large arterioles as well as red blood cell
velocities were measured before and after exchange of blood for solutions of identical haematocrit containing either high-
(HMWD) or low-molecular weight dextran (LMWD). The potential role of endothelial autacoids was investigated by local application
of the NO-synthase inhibitor N
G-nitro-L-arginine (L-NNA), the inhibitor of cyclooxygenase, indomethacin (3 μM), or the K+-channel blocker, tetrabutylammonium (TBA, 0.1 mM) to assess the potential effects of EDHF. HMWD (n = 11 animals) increased plasma viscosity by 64 ± 3% and dilated arterioles of all branching orders (A1–A4) significantly
[by 24 ± 3% (A1–A2) and 32 ± 3% (A3–A4)]. This dilation compensated fully for the calculated initial increase of WSS. LMWD
(n = 6) did not affect plasma viscosity or arteriolar diameters. Tissue treatment with L-NNA (30–300 μM, n = 12) substantially diminished the HMWD-induced dilation in small arterioles (A3–A4; to 13 ± 3%; P<0.05) and virtually abolished it in large ones (A1–A2). Consequently, the calculated WSS increased significantly in these
arterioles (by 31 ± 5%). TBA combined with L-NNA (n = 4) did not reduce further the remaining dilation. Indomethacin (n = 6) had no effect on HMWD-induced dilation. We conclude that an increase of WSS induces a mainly NO-mediated arteriolar
dilation. This dilation occurs in all arteriolar branching orders and is of sufficient magnitude to compensate for the initial
WSS-increase. Thus, any elevations of WSS fulfil the requirement for a signal to change diameter along the arteriolar tree
in a coordinated manner. The fully compensating dilation which we observed indicates that WSS is a controlled variable. It
does, however, raise questions as to its role as a continuous endothelial stimulus.
Received: 2 August 1996 / Received after revision: 24 February 1997 / Accepted: 14 April 1997 相似文献
29.
Philipp Müller Christof Wrner Rolf Mülhaupt 《Macromolecular chemistry and physics.》1995,196(6):1917-1928
A novel family of functional ethene copolymers with various side chains were prepared by melt grafting of poly(ethene-co-methacrylic acid), containing 3,00 and 4,25 mol-% of methacrylic acid, with 2-substituted 1,3-oxazolines such as 2-phenyl-1,3-oxazoline, 2-undecyl-1,3-oxazoline, 2-heptadecyl-1,3-oxazoline, and 4-(1,3-oxazolin-2-yl)phenyl 4-methoxybenzoate. 1H NMR and FTIR studies of the polymer microstructures revealed that carboxylic acid groups reacted with 1,3-oxazolines within few minutes to form esteramide-coupled side chains in very high yields. Torque of the reaction mixture, mechanical and thermal properties of the graft copolymers were measured. In the case of 2-heptadecyl-esteramide-substituted polyethenes, the side-chain cocrystallization accounted for higher crystallinity of the resulting graft copolymers. 相似文献
30.
Philipp Müller Christof Wrner Rolf Mülhaupt 《Macromolecular chemistry and physics.》1995,196(6):1929-1936
2-Phenyl-1,3-oxazoline was injected into poly(ethene-co-methacrylic acid), containing 4,25 mol-% methacrylic acid units, at 225°C. In the first stage, 2-phenyl-1,3-oxazoline reacted with carboxylic acid groups to form esteramide side chains via grafting reaction. In the second stage, 2-phenyl-1,3-oxazoline containing methyl 4-nitrobenzensulfonate initiator was added to initiate in-situ cationic polymerization, yielding poly(N-benzoylethylenimine) as dispersed phase with 0,2–3,5 μm average diameter. Morphological, mechanical and thermal properties of poly-(ethene-co-methacrylic acid) blends, prepared by grafting combined with in-situ polymerization of 2-phenyl-1,3-oxazoline, were investigated. 相似文献