全文获取类型
收费全文 | 13469篇 |
免费 | 979篇 |
国内免费 | 38篇 |
专业分类
耳鼻咽喉 | 82篇 |
儿科学 | 243篇 |
妇产科学 | 236篇 |
基础医学 | 1916篇 |
口腔科学 | 428篇 |
临床医学 | 1741篇 |
内科学 | 2671篇 |
皮肤病学 | 273篇 |
神经病学 | 1114篇 |
特种医学 | 528篇 |
外科学 | 1977篇 |
综合类 | 85篇 |
一般理论 | 2篇 |
预防医学 | 1195篇 |
眼科学 | 242篇 |
药学 | 827篇 |
中国医学 | 34篇 |
肿瘤学 | 892篇 |
出版年
2023年 | 84篇 |
2022年 | 94篇 |
2021年 | 222篇 |
2020年 | 157篇 |
2019年 | 217篇 |
2018年 | 280篇 |
2017年 | 259篇 |
2016年 | 247篇 |
2015年 | 234篇 |
2014年 | 353篇 |
2013年 | 513篇 |
2012年 | 701篇 |
2011年 | 751篇 |
2010年 | 371篇 |
2009年 | 337篇 |
2008年 | 611篇 |
2007年 | 620篇 |
2006年 | 588篇 |
2005年 | 510篇 |
2004年 | 505篇 |
2003年 | 446篇 |
2002年 | 420篇 |
2001年 | 359篇 |
2000年 | 446篇 |
1999年 | 381篇 |
1998年 | 162篇 |
1997年 | 125篇 |
1996年 | 122篇 |
1995年 | 122篇 |
1994年 | 115篇 |
1993年 | 100篇 |
1992年 | 318篇 |
1991年 | 327篇 |
1990年 | 323篇 |
1989年 | 262篇 |
1988年 | 248篇 |
1987年 | 284篇 |
1986年 | 265篇 |
1985年 | 210篇 |
1984年 | 206篇 |
1983年 | 180篇 |
1982年 | 104篇 |
1981年 | 80篇 |
1979年 | 123篇 |
1978年 | 90篇 |
1977年 | 79篇 |
1975年 | 76篇 |
1974年 | 75篇 |
1973年 | 81篇 |
1970年 | 72篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
Dibasic staining of large epoxy tissue sections and applications to surgical pathology 总被引:3,自引:0,他引:3
A variety of normal and pathologic aldehyde-fixed osmium postfixed human tissues were prepared as large sections embedded in Spurr epoxy. They were stained with a sequential basic fuchsin--methylene blue stain which gives "hematoxylin- and eosin-like" staining and additionally functions as several special stains. This technic also allows for electron microscopy directly on the embedded tissue. The histologic and cytologic preservation and overall staining was superior to tissue embedded in glycol methacrylate. The methods and technics presented in this article have important applications in diagnostic surgical pathology and histology in general. 相似文献
72.
Multimers of soluble major histocompatibility complex class I and II molecules have proven to be useful reagents in quantifying and following specific T cell populations. This study describes the design, generation, and characterization of a novel, single chain I-A(b) molecule which utilizes a unique linker derived from the murine invariant chain. A fragment of the invariant chain, residues 58-85, binds to a region proximal to the class II peptide binding groove and stabilizes occupancy of the class II invariant chain-associated peptide. We have utilized this fragment, replacing CLIP with the Ealpha peptide sequence, to lock the attached peptide into the class II binding groove. The single chain I-A(b) molecule was recognized by a panel of conformation-sensitive, I-A(b)-specific, monoclonal antibodies. Membrane-bound and soluble forms of the single chain I-A(b) stimulated an antigen-specific T cell hybridoma, and tetramers made from soluble monomers stained these cells. The unique features of this molecule may be useful in the design of recombinant T cell receptor ligands containing peptides with low affinity for MHC. 相似文献
73.
K. S. Kristensen S. Norn F. Espersen P. Stahl Skov J. Holst Pedersen J. Sparup N. M. Jensen H. Permin 《Inflammation research》1993,38(3-4):C218-C220
Some cytokines are known to affect IgE-mediated basophil histamine release. The effect of the cytokine granulocyte-macrophage colony-stimulating factor (GM-CSF) on human basophil and masct cell histamine release was studies further. Blood leukocytes with approximately 2% basophils from 9 healthy individuals were incubated with recombinant human GM-CSF (0.3–30 U/ml) in combination with A23187 (10–7–10–6
M) or washedStaphylococcus aureus whole bacteria (0.3–2.5 mg/ml). Histamine release was measured spectrofluorometrically. GM-CSF in itself did not induce histamine release. The addition of GM-CSF to cells stimulated with A 23187 caused a dose-dependent enhancement amounting to mean 70% at 3 U/ml and mean 170% at 30 U/ml (P<0.05). GM-CSF enhanced the bacteria-induced histamine release by 30% at U/ml and by 65% at 3 U/ml (P<0.05). The enhancement did not depend on cell-bound IgE or LPS contamination. In preliminary mast cell experiments with lung tissue we did not find an enancing effect of GM-CSF on IgE-mediated histamine release. 相似文献
74.
Use of 125I-secretin to identify and characterize high-affinity secretin receptors on pancreatic acini 总被引:1,自引:0,他引:1
R T Jensen C G Charlton H Adachi S W Jones T L O'Donohue J D Gardner 《The American journal of physiology》1983,245(2):G186-G195
We prepared 125I-secretin and studied the kinetics, stoichiometry, and chemical specificity with which the labeled peptide binds to dispersed acini prepared from guinea pig pancreas. Iodinated secretin retained intrinsic biological activity in that it was as effective but 2.5-times less potent than native secretin in its ability to bind to pancreatic acini and to increase cellular cAMP. Scatchard analysis of binding of 125I-secretin indicated that each pancreatic acinar cell has approximately 93,000 binding sites, half of which are occupied by 11 nM iodinated secretin. Binding of 125I-secretin was rapid, reversible, saturable, specific, and temperature dependent. Binding of 125I-secretin was inhibited by secretin, vasoactive intestinal peptide, PHI, and Gila monster venom but not by glucagon, gastric inhibitory polypeptide, cholecystokinin, caerulein, gastrin, bovine pancreatic polypeptide, somatostatin, neurotensin, leucine-enkephalin, methionine-enkephalin, carbachol, bombesin, litorin, eledoisin, physalaemin, or substance P. With agonists (secretin, vasoactive intestinal peptide, PHI, or Gila monster venom), as well as antagonists (C-terminal fragments of secretin), there was a close correlation between their relative potencies for inhibiting binding of 125I-secretin and their relative potencies for increasing cAMP (agonists) or inhibiting the secretin-induced increase in cAMP (antagonists). For a given agonist, however, a 40-fold higher concentration was required for half-maximal inhibition of binding of 125I-secretin than was required to produce a half-maximal increase in cellular cAMP. Thus, maximal stimulation of cellular cAMP occurs when approximately one-third of the secretin receptors are occupied by an agonist. 相似文献
75.
Transient and sustained types of long-term potentiation in the CA1 area of the rat hippocampus 总被引:2,自引:0,他引:2
Synaptic potentiation induced by high frequency stimulation was investigated by recording field excitatory postsynaptic potentials (f-EPSPs) in rat hippocampal slices. Potentiation consisted of a transient period of decaying f-EPSPs (short-term potentiation, STP) that led to a plateau of continuously potentiated f-EPSPs (long-term potentiation, LTP). Here we show that a previously unknown type of transient, use-dependent, long-lasting potentiation (t-LTP) can account for STP. t-LTP could be stored for more than 6 h and its decay was caused by synaptic activation. Both the expression and the decay of t-LTP were input specific. t-LTP was induced differently from conventional LTP in that the amplitude of t-LTP was dependent upon the stimulation frequency, whereas the magnitude of LTP was dependent on the number of stimuli in the induction train. The decay of t-LTP could not be prevented by the blockage of glutamate receptors, but was prevented by the blockage of stimulus-evoked neurotransmitter release, suggesting that t-LTP is expressed presynaptically. Paired-pulse stimulation experiments showed that the decay of t-LTP was mediated by a decrease in the probability of neurotransmitter release. The decline of t-LTP could be prolonged by the activation of NMDA receptors. Hence, both single and paired-pulse stimuli prolonged the decline of the t-LTP. This decline could be prevented by high frequency burst stimulation (200 Hz). We conclude that t-LTP allows dynamic modulation of synaptic transmission by providing not only spatial association but also temporal convergence between synaptic inputs. Therefore, t-LTP might be a substrate for the encoding of synaptic memory. 相似文献
76.
Histopathological grading of soft tissue tumours. Prognostic significance in a prospective study of 278 consecutive cases 总被引:1,自引:0,他引:1
Olaf Myhre Jensen Jrgen Hgh Svend E.
stgaard Axel Munck Nordentoft Otto Sneppen 《The Journal of pathology》1991,163(1):19-24
A consecutive 10-year series of 278 soft tissue sarcomas was prospectively graded, using a system based on the number of mitoses and taking into account parameters such as cellularity, anaplasia, necrosis, and histogenetic type and subtype of tumour. Prognostic factors in relation to metastasis-free survival were studied by uni- and multivariate analysis. Fifty-seven (20.5 per cent) were low-grade tumours, 43 (15.5 per cent) were intermediate, and 178 (64 per cent) were high grade. High-grade tumours were divided into two groups; 80 (29 per cent) grade 3A (= 5-20 mitoses per 10 high power fields (HPF)) and 78 grade 3B (28 per cent) (= more than 20 mitoses/10 HPF); 10 HPF corresponds to 2.5 mm2. Twenty (7.2 per cent) high-grade tumours could not be further subdivided. Grading was found to be the prognostic factor associated with the strongest predictive value. Five-year survival in low-grade and intermediate tumours (95 and 86 percent, respectively) differed significantly (P less than 0.0001) from high grade (50 per cent) and (p = 0.0018) between grade 3A (64 per cent) and grade 3B (41 per cent). Other prognostic indicators of importance in high-grade tumours were age, local recurrence at presentation (primary operation outside the Centre), and localization (superficial vs. deep). 相似文献
77.
The hypophysis of the brook trout is irrigated by blood vessels which originate from the internal carotid arteries. These are: (1) branches of the ventral hypothalamic arteries that give rise to an extensive capillary plexus in the neurohypophysis from which vessels extend into all regions of the adenohypophysis; (2) branches of the caudal hypothalamic artery that irrigate the saccus vasculosus and continue anteriorly to supply the ventral areas of the meta-adenohypophysis; (3) a caudal hypophyseal artery which vascularizes a portion of the meta-adenohypophysis however, this vessel is not always present; (4) a pair of small arteries which supply the peripheral regions of the gland directly from the carotids. Most of the neurosecretory fibers of the preoptic-hypophyseal tract terminate close to capillaries in the neurohypophysis. A few axons extend into meso-adenohypophyseal tissue. It is suggested that the secretory activities of the pro-, meso- and metaadenohypophyses are governed by hypothalamic factors that are chiefly transmitted to the gland cells via the vascular system (indirect control). However, the activity of the meso-adenohypophysis may also be regulated by factors which are transmitted directly to the cells from the endings of neurosecretory fibers which have traversed the neurohypophysis (direct control). The distribution and abundance of neurosecretion in the ventral hypophysis suggest the possibility of storage of hypothalamic products within this region. 相似文献
78.
The pathogenetic role of autoantibodies in multiple sclerosis (MS) is uncertain. CD5+ B cells commonly produce autoantibodies, but CD5 expression has also been implicated in B-cell tolerance. We studied B-cell subsets, anti-myelin protein antibody-secreting cells in cerebrospinal fluid (CSF) and a panel of serum autoantibodies in patients with clinically isolated syndromes (CIS), suggestive of MS and patients with clinically definite MS (CDMS). Patients with CDMS had a higher percentage of CD5- B cells in CSF than did control subjects (P = 0.02). CIS patients with immunoglobulin G (IgG) oligoclonal bands in CSF or multiple lesions on magnetic resonance imaging (MRI) had a higher percentage of CD5- B cells in CSF than did the remaining CIS patients (P = 0.03). The percentage of CD5- and CD80+ B cells correlated positively and the percentage of CD5+ B cells correlated negatively with the number of CSF cells secreting anti-myelin basic protein (anti-MBP) antibodies. The prevalence of serum autoantibodies was comparable in the three patient groups. We conclude that intrathecal expansion of CD5- B cells appears to be more characteristic in MS patients, and CD5+ B cells may be associated with a lower prevalence of anti-myelin antibody production. 相似文献
79.
Cenarro A Jensen HK Casao E Civeira F González-Bonillo J Rodríguez-Rey JC Gregersen N Pocoví M 《Human mutation》1998,11(5):413
We used the single strand conformation polymorphism (SSCP) method to investigate 13 apparently unrelated Spanish patients with familial hypercholesterolemia (FH) for mutations in the promoter region and the 18 exons and their flanking intron sequences of the low density lipoprotein (LDL) receptor gene. We found 16 aberrant SSCP patterns, and the underlying mutations were characterized by DNA sequencing. Five novel missense mutations, Q71E, C74G, C95R, C281Y and D679E, and one nonsense mutation, Q133X, were identified. We also found six missense mutations, S156L, D200Y, D200G, E256K, T413K and C646Y, and one stop codon mutation, W(-18)X, that were previously described in patients from other populations. A new frameshift mutation, 2085del19, was found in one patient. We also identified three splicing mutations; two of them are novel mutations, 1706-10G->A and 2390-1G->A, and the other one has been reported recently, 313+1G->C. Four patients were found to carry two different mutations in the same allele: Q71E and 313+1G->C; C95R and D679E; W(-18)X and E256K, and C281Y and 1706-10G->A. Our results demonstrate that there is a broad spectrum of mutations in the LDL receptor gene in the Spanish population. 相似文献
80.
Special report. Steriod receptors in breast cancer. 总被引:5,自引:0,他引:5
E R DeSombre P P Carbone E V Jensen W L McGuire S A Wells J L Wittliff M B Lipsett 《The New England journal of medicine》1979,301(18):1011-1012