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41.
LAURENT MICLO EMMANUEL PERRIN ALAIN DRIOU MICHEL MELLET GUY LINDEN 《Chemical biology & drug design》1995,46(2):186-192
A method for the simultaneous determination of the ratios of the three aromatic amino-acid residues in peptides was set up in acidic conditions. Binary and ternary mixtures of these amino acids were prepared, and first- and second-derivative spectra then calculated from their 0.1 nm resolution spectra between 240 and 320 nm. Certain spectral bands were chosen to differentiate tyrosine from tryptophan on the first-derivative spectra, and phenylalanine from tyrosine and tryptophan on the second-derivative spectra. Variation of the amplitude of the chosen bands was shown to be a linear function of the ratio of the aromatic amino acids in the mixture. This technique was validated with peptides whose sequence was known. The difference between theoretical and experimentally determined ratios was lower than 10%. Since the results are obtained as ratios, neither the concentration nor the nature of the peptide has to be known. The feasibility of application using a photodiode array detector with high resolution in reversed-phase high-performance liquid chromatography is discussed. © Munksgaard 1995. 相似文献
42.
James T. Winslow Thomas R. Insel 《Progress in neuro-psychopharmacology & biological psychiatry》1991,15(6):745-757
1. Rat pups emit ultrasonic calls during brief episodes of social separation. These calls have been variously described as “distress” calls and may be related to the separation cries expressed by the young of many mammalian species.
2. Ultrasonic call of rat pups are modulated by environmental stimuli such as ambient temperature, olfactory and tactile stimuli associated with the nest.
3. Calls are also sensitive to a variety of purported anxiolytic and anxiogenic drugs, including the benzodiazepines, serotonin agonists, and ligands at the NMDA-glycine receptor complex.
4. In addition to providing a simple test for the anxiolytic properties of drugs, this model may also provide new insights about the development and neurobiology of anxiety. 相似文献
43.
Thirty-five posters were presented at the Workshop on Brain Uptake And Utilization Of Fatty Acids, Lipids, and Lipoproteins.
They were grouped into four categories: (1) mechanisms of lipid uptake and transport to the brain, (2) lipoproteins and polyunsaturated
fatty acids, (3) eicosanoids in brain function, and (4) fatty acids and lipids in brain disorders. This article summarizes
the highlights of the research presented in these posters. The individual abstracts follow these synopses. 相似文献
44.
Elizabeth Z. Bordayo John R. Fawcett Sarita Lagalwar Aleta L. Svitak William H. Frey 《Journal of molecular neuroscience : MN》1996,27(2):185-194
Arachidonic acid (AA), released in response to muscarinic acetylcholine receptor (mAChR) stimulation, previously has been
reported to function as a reversible feedback inhibitor of the mAChR. To determine if the effects of AA on binding to the
mAChR are subtype specific and whether AA inhibits ligand binding to other G protein-coupled receptors (GPCRs), the effects
of AA on ligand binding to the mAChR subtypes (M1, M2, M3, M4, and M5) and to the μ-opioid receptor, β2-adrenergic receptor (β2-AR), 5-hydroxytryptamine receptor (5-HTR), and nicotinic receptors were examined. AA was found to inhibit ligand binding
to all mAChR subtypes, to the β2-AR, the 5-HTR, and to the μ-opioid receptor. However, AA does not inhibit ligand binding to the nicotinic receptor, even
at high concentrations of AA. Thus, AA inhibits several types of GPCRs, with 50% inhibition occurring at 3–25 μM, whereas the nicotinic receptor, a non-GPCR, remains unaffected. Further research is needed to determine the mechanism by
which AA inhibits GPCR function. 相似文献
45.
Robert H. K. Mak 《Pediatric nephrology (Berlin, Germany)》1998,12(8):637-642
Insulin and branched-chain amino acid (BCAA) metabolism was studied in 14 adolescents with uremia on hemodialysis. Glucose
tolerance was measured by intravenous glucose tolerance tests. Insulin sensitivity was measured by the euglycemia clamp technique.
Insulin secretion during constant hyperglycemia was measured by the hyperglycemic clamp technique. Fasting plasma BCAA concentrations
were compared with data from 8 adolescent controls, whereas insulin indices were compared with 8 young adults controls and
with published normal data in adolescents. The patients could be further sub-divided into two groups with respect to their
growth velocity standard deviation score (GVSDS). Group 1 consisted of 7 patients with GVSDS less than −2. This group demonstrated
insulin resistance, glucose intolerance, and low insulin secretion. This group also had low plasma valine, leucine, and isoleucine
concentrations compared with control values. Group 2 consisted of 7 patients with GVSDS more than −2. This group demonstrated
insulin resistance, but normal glucose tolerance and normal insulin secretion. Plasma valine, leucine, and isoleucine concentrations
in group 2 were not different from control values. Total plasma BCAA correlated with glucose tolerance index and with insulin
secretion, but not with insulin sensitivity. Growth failure in uremia is associated with glucose intolerance, hypoinsulinemia,
and low plasma BCAA concentrations. Impaired utilization of conventional energy sources leading to preferential oxidation
of BCAA may contribute to reduced anabolism and growth failure in uremia.
Received October 8, 1997; received in revised form February 3, 1998; accepted February 6, 1998 相似文献
46.
L. Giovannelli F. Casamenti G. Pepeu 《Journal of neural transmission (Vienna, Austria : 1996)》1998,105(8-9):935-948
Summary. A unilateral quisqualic acid lesion was placed in the nucleus basalis magnocellularis of 3- and 24-month-old rats, and the
animals were sacrificed at different times post-surgery. The morphology and the number of the cholinergic neurons of the nucleus
basalis were analyzed by means of immunohistochemistry for cholineacetyltransferase, in order to evaluate the size and severity
of the lesion. Immunohistochemistry for the immediate early gene c-fos was also performed in order to clarify its role in
the process of neurodegeneration following the excitotoxin injection. The DNA laddering and TUNEL techniques were used to
define the type of cell death involved. At short times (4 hr) the lesion induced alterations in the morphology of cholinergic
neurons of the nucleus basalis. Subsequently, a significant decrease in the number of neurons was found in comparison to the
contralateral unlesioned side. In the older animals the loss of cholineacetyltransferase immunoreactivity had an earlier onset
(4 hr) than in the young (24 hr). C-fos expression was induced by the lesion and not by saline injection in the nucleus basalis
and in neighbouring areas of the brain as early as 4 hr after surgery. The c-fos protein was no longer present by 24 hr. Furthermore,
the c-fos gene product was consistently absent from the nuclei of cholinergic cells. The aged animals exhibited a slower and
smaller increase in c-fos as measured by counting the labelled nuclei in the injected area. Analysis of DNA fragmentation
did not provide any evidence for apoptosis as the type of cell death involved in the cholinergic degeneration. These results
indicate that the c-fos protein might have a protective role in the response to excitotoxic lesions. Furthermore, we have
shown that the aged brain displays a reduced ability to produce a c-fos-mediated plastic response to the lesion.
Received December 17, 1997; accepted February 17, 1998 相似文献
47.
F-J Tsai C-H Tsai S-F Wu Y-H Liu T-F Yeh 《Acta paediatrica (Oslo, Norway : 1992)》1996,85(12):1487-1490
To evaluate the catabolic effects of dexamethasone therapy on protein metabolism, amino acid concentrations and urinary 3-methylhistidine (3MH) were measured in 28 premature infants who were included in a double-blind controlled study using early dexamethasone therapy in the prevention of bronchopulmonary dysplasia. Fifteen infants received dexamethasone (0.5mg/kg/day i.v.) and 13 infants received normal saline as control. Heparinized venous blood samples for amino acid analysis were obtained before the study and again at day 5 after starting the study. Urinary 3MH was measured on days 1, 3, 5, 7, 14, 21, and 28 of treatment. A substantial increase in amino acid concentrations was observed in infants receiving dexamethasone. Alanine, glutamine, citrulline, ornithine and cystine concentrations increased twofold or more. The 3MH:creatinine ratio was increased in the treated group. These metabolic effects were most likely due to an increase in protein catabolism. 相似文献
48.
Anna Pizzirusso Patrizia Oliva Sabatino Maione Michele D’Amico Francesco Rossi L. Berrino 《Naunyn-Schmiedeberg's archives of pharmacology》1998,357(5):514-518
In order to evaluate the role played by vasopressin on pressor responses elicited by stimulation of the periaqueductal gray
(PAG) area by excitatory amino acids we carried out in vivo studies in genetically vasopressin deficient rats (Brattleboro).
Microinjections of l-glutamic acid (glutamate, 0.6 to 60 nmol/rat) or N-methyl-d-aspartic acid (NMDA, 0.07 to 7 nmol/rat)
into the PAG area of freely moving Brattleboro rats induced increases of arterial blood pressure values significantly lower
than those obtained in Long Evans rats (control) (glutamate in Brattleboro rats: from +2±1 mmHg to 16±3 mmHg; glutamate in
Long Evans rats: from +16±2 mmHg to +36±4 mmHg; NMDA in Brattleboro rats: from +5±2 mmHg to +34 ±8 mmHg; NMDA in Long Evans
rats: from +18±7 mmHg to 80±9 mmHg; n=5). Similarly, in anaesthetized Brattleboro rats (urethane 1.2 g/kg i.p.) pressor responses to NMDA microinjections (0.7
nmol/rat) into the PAG area were significantly lower than in Long Evans rats (controls) (+15±3 mmHg vs +24±4 mmHg). In Long
Evans rats NMDA injection also reversed blood pressure decrease induced by ganglionic blocker, hexamethonium and/or losartan
(3 mg/kg i.v.), an AT1 receptor antagonist. In Brattleboro rats, NMDA injection did not reverse blood pressure decreases induced
by hexamethonium (5 mg/kg i.v.). Moreover, hexamethonium induced blood pressure decrease was not reversed by acetylcholine
injection (137 nmol/rat) into the PAG area of anaesthetized Long Evans rats, but if injected before hexamethonium, acetylcholine
was able to increase blood pressure (+25±3 mmHg). Our results document: i) the importance of the PAG area in the control
of cardiovascular system; ii) the involvement of excitatory amino acids in the neural control of vasopressin release; iii)
the close relationship between glutamate and vasopressin in the central blood pressure regulation.
Received: 1 April 1997 / Accepted: 2 February 1998 相似文献
49.
I. Steiner G. Feir D. Soffer A. B. Pleet O. Abramsky 《Acta neurologica Scandinavica》1988,77(2):152-157
The causes and clinical features of chronic progressive myelopathy (CPM) were evaluated in a retrospective study of 107 patients. A special emphasis was put on those in whom no underlying cause for the myelopathy could be determined. Of 76 such, 39 (51%) had oligoclonal immunoglobulins (Ig) in the CSF and were therefore considered as possible MS, while the remainder, without oligoclonal Ig, were designated "myelopathy of unknown origin" (MUO). Our "possible MS" group was similar clinically to reported series of proven spinal MS, and it seems therefore, that the presence of oligoclonal Ig permits the recognition of a group of patients with myelopathy who might be at a greater risk for MS. Patients with MUO differed from possible MS patients in several clinical characteristics, but most significantly in disease course and levels of functional disability which were more benign in the former. Myelopathy in possible MS patients was also of a primary pyramidal and asymmetrical nature. It is therefore suggested that the segregation of patients with CPM of undetermined origin into 2 separate groups based on the presence or absence of oligoclonal Ig might be of prognostic significance. 相似文献
50.
Daniel Fagret Jean-Eric Wolf Paul Pilichowski Jean-Paul Mathieu Claude Pernin Marcel Apparu Charles Arvieux Pierre Cuchet Michel Vidal Michel Comet 《European journal of nuclear medicine and molecular imaging》1988,14(12):624-627
The myocardial uptake of fatty acids labeled with radioactive iodine and injected i.v. can only be evaluated with SPECT if their oxidation kinetics is slow enough. For this reason, we evaluated different iodomethylated fatty acids in mice and dogs to determine which of them shows the highest myocardial uptake and the slowest oxidation. The most suitable was found to be 16-iodo-3-methyl hexadecanoic acid (mono ) since its myocardial fixation was the same as that of the reference, i.e. 16-iodo-9-hexadecenoic acid (IHA), whereas it was degraded more slowly. Thirty min after injection of mono into dogs, the decrease in myocardial activity with respect to the maximum was two fold less than after IHA injection. The myocardial uptake of the two dimethylated fatty acids studied, i.e. 16-iodo-2,2-methyl hexadecanoic acid and 16-iodo-3,3-methyl hexadecanoic acid, was less than that of IHA in mice and dogs. In the latter, the myocardial uptake was so small that we were unable to study the time course of its activity. Consequently, these dimethylated fatty acids are not suitable for the study of the myocardial uptake of fatty acids in man. 相似文献