全文获取类型
收费全文 | 846篇 |
免费 | 57篇 |
国内免费 | 5篇 |
专业分类
耳鼻咽喉 | 6篇 |
儿科学 | 41篇 |
妇产科学 | 8篇 |
基础医学 | 76篇 |
口腔科学 | 66篇 |
临床医学 | 80篇 |
内科学 | 123篇 |
皮肤病学 | 9篇 |
神经病学 | 22篇 |
特种医学 | 191篇 |
外科学 | 62篇 |
综合类 | 76篇 |
预防医学 | 49篇 |
眼科学 | 4篇 |
药学 | 43篇 |
中国医学 | 24篇 |
肿瘤学 | 28篇 |
出版年
2022年 | 6篇 |
2021年 | 4篇 |
2020年 | 6篇 |
2019年 | 4篇 |
2018年 | 15篇 |
2017年 | 13篇 |
2016年 | 12篇 |
2015年 | 12篇 |
2014年 | 29篇 |
2013年 | 51篇 |
2012年 | 47篇 |
2011年 | 38篇 |
2010年 | 42篇 |
2009年 | 36篇 |
2008年 | 34篇 |
2007年 | 50篇 |
2006年 | 18篇 |
2005年 | 13篇 |
2004年 | 9篇 |
2002年 | 6篇 |
2001年 | 9篇 |
2000年 | 5篇 |
1999年 | 13篇 |
1998年 | 56篇 |
1997年 | 47篇 |
1996年 | 36篇 |
1995年 | 23篇 |
1994年 | 29篇 |
1993年 | 23篇 |
1992年 | 6篇 |
1991年 | 11篇 |
1990年 | 6篇 |
1989年 | 19篇 |
1988年 | 24篇 |
1987年 | 19篇 |
1986年 | 14篇 |
1985年 | 21篇 |
1984年 | 10篇 |
1983年 | 11篇 |
1982年 | 9篇 |
1981年 | 12篇 |
1980年 | 10篇 |
1979年 | 3篇 |
1978年 | 6篇 |
1977年 | 6篇 |
1976年 | 9篇 |
1975年 | 5篇 |
1974年 | 4篇 |
1971年 | 4篇 |
1970年 | 5篇 |
排序方式: 共有908条查询结果,搜索用时 15 毫秒
1.
2.
Intracranial circulation: pulse-sequence considerations in three- dimensional (volume) MR angiography 总被引:2,自引:0,他引:2
The technique and feasibility of magnetic resonance (MR) angiography of intracranial vessels were studied in 35 healthy volunteers. Variations in image orientation, repetition time (TR), and flip angle were evaluated to determine their effects on flow-related enhancement. Gradient modifications--including echo time (TE), motion compensation, bandwidth, and field of view--were also studied in an effort to reduce motion-induced phase shifts. Results indicated that a FISP (fast imaging with steady precession) sequence with a TR of 50 msec, TE of 15 msec, velocity compensation in the read and section-select directions, acceleration compensation in the read direction, anisotropic volume, and a 1.25-mm partition thickness produced three-dimensional angiographic MR images that were accurate and reproducible in the depiction of the major intracranial vessels. Difficulties with field of view, persistent signal void secondary to higher-order motion, and spatial resolution remain major problems requiring additional study. 相似文献
3.
Maxillary sinusitis in adults: an evaluation of placebo-controlled double-blind trials 总被引:1,自引:0,他引:1
BACKGROUND: In general practice, acute sinusitis is frequently diagnosed
and treated with antibiotics. OBJECTIVE: This study aimed to determine the
evidence for the effectiveness of antibiotic treatment in acute maxillary
sinusitis in adults by assessing the methodological quality of
placebo-controlled double-blind randomized trials. METHOD: An evaluation by
four raters through a 35-item scoring-scale for internal and external
validity of all placebo-controlled double-blind randomized trials on acute
sinusitis found between January 1966 and July 1996. RESULTS: Eighty-five
trials were excluded because they were not placebo-controlled,
double-blind, randomized, or were carried out in patients with chronic
sinusitis or in children. The three remaining trials were performed in
different populations (one in general practice) between 1973 and 1978. Only
one study claimed superiority of antibiotic treatment. Different inclusion
criteria and major outcome measures were used by the authors. The
reliability of major outcome events was reported poorly or not at all and
in two studies outcome measures were clinically inappropriate. The studies
scored 30-62% of the maximum attainable score for internal validity and
10-20% for external validity. CONCLUSION: The effectiveness of antibiotic
treatment in acute maxillary sinusitis in a general practice population is
not based sufficiently on evidence.
相似文献
4.
5.
H Angus-Leppan GA Lambert J Michalicek 《Cephalalgia : an international journal of headache》1997,17(6):625-630
Co-existence of facial and occipital pain may occur in occipital neuralgia, migraine and cluster headache; suggesting convergence of trigeminal and cervical afferents. Such convergence has been shown in humans and other animals, but the site and extent of this are uncertain. In anaesthetized adult cats, the superior sagittal sinus and occipital nerve were stimulated electrically, and extracellular recordings made in the dorsolateral area of the upper cervical cord using glass-coated tungsten electrodes. Of 49 units in 10 cats, 33 (67%) had input from the superior sagittal sinus and the occipital nerve. Thirteen (27%) had superior sagittal sinus input and 3 (6%) had occipital nerve input. Convergent receptive fields were identified mechanically in 7 units. These experiments in cats show convergent input from occipital nerve and superior sagittal sinus on dorsolateral area units in two-thirds of cases studied. This experimental site of trigeminocervical convergence may relate to referral of pain in occipital neuralgia and other headaches. 相似文献
6.
In patients with PG-dependent renal function, NSAID administration
constantly reduces GFR and RBF in a dose-dependent fashion. In this
situation, the risk of overt acute renal failure is high and should be
taken into proper account. In contrast, the incidence of NSAID-related
renal structural alterations appears to be very low, yet the absolute
number of patients may be significant considering the wide use of such
drugs. Concerning the antiproteinuric effect of NSAIDs, the unfavourable
ratio risk/benefit does not seem to support their indication in proteinuric
nephropathies. The development of PGHS-2 selective inhibitors is promising,
and may open new therapeutical strategies in the treatment of the
progression of renal disease.
相似文献
7.
Patch clamp techniques were used to study whole cell ionic currents in Schwann cells (SC) from a tropical marine fish, the bicolor damselfish, Pomacentrus partitus. The bicolor damselfish is affected by a disease termed damselfish neurofibromatosis (DNF), being developed as an animal model of neurofibromatosis-type 1 (NF1) in humans. NF1 affects SC, fibroblasts, and perineurial cells. The sole depolarization-activated ionic current present in cultured SC from normal fish peripheral nerve and from neurofibromas of fish with induced or spontaneously occurring DNF was an inactivating K+ current (K current), with a strong dependence on the Nernst potential for K+. This K current activated at depolarizations to -40 mV and above and inactivated during a maintained test pulse (0.2-1 s), but inactivation was significantly greater in tumored SC. Both currents were inhibited by 4-aminopyridine (Kd ? 1 mM) and by dendrotoxin (15 μM) but were insensitive to extracellular tetraethyammonium (≤ 150 mM), indicating that the whole cell currents were similar pharmacologically. The currents could be distinguished on the basis of their sensitivity to depolarized holding potential, with normal cells less sensitive. Half-inactivation of the current was -32 mV in normal cells and -38 mV in tumored cells. Inactivation curves constructed from the average normalized current for many SC were significantly different in normal and tumored cells. When the depolarized holding potential was maintained between test depolarizations, greater voltage-dependent inactivation in tumored cells was apparent. Normal cells maintained an average of 36% of peak current at a holding voltage of ?40 mV, while in tumored cells this average was 12%, a significant difference. © 1994 Wiley-Liss, Inc. 相似文献
8.
9.
10.
Endothelin receptor expression in human decidua 总被引:3,自引:1,他引:3
Kohnen G; Campbell S; Irvine GA; Church HJ; MacLachlan F; Titterington M; Cameron IT 《Molecular human reproduction》1998,4(2):185-193
The endothelins are signalling peptides that act via two receptors, ET(A)
and ET(B). In the human endometrium, endothelin receptors have been
demonstrated in glands and stroma and have been shown to vary during the
course of the menstrual cycle. The present study was undertaken to
determine whether or not expression of endothelin receptors changes during
pregnancy or after administration of exogenous progestagens. The expression
of the receptors was correlated with the appearance of basement membrane
components during decidualization of the endometrial stroma. Decidual
specimens (n = 15) were obtained during the first trimester of pregnancy
and 10 at term. Sixteen pairs of endometrial biopsies were obtained from
women with menorrhagia before and after exposure to exogenous progestagens.
A total of 15 hysterectomy specimens were used as controls for the
expression of stromal basement membrane proteins in the absence of
decidualization. Autoradiography was carried out with selective ligands for
ET(A) ([125I]-PD 151242) and ET(B) ([125I]-BQ3020). The distribution of
ligand binding was then compared with the distribution of laminin alpha2
light chain and collagen IV. ET(A), ET(B), laminin alpha2 light chain, and
collagen IV were expressed in stromal decidual cells in the first trimester
of pregnancy. ET(B) was also found on endometrial glandular epithelium.
Quantitative macro-autoradiography and multiple regression analysis
demonstrated a highly significant positive correlation (P < 0.001)
between expression of ET(B) and laminin alpha2 light chain. In the third
trimester qualitative examination suggested a reduction of ET(A) in the
stroma. Progestagen-induced decidua exhibited a similar pattern to that
found in first trimester decidua. This study has demonstrated up-regulation
of ET(B) during the progesterone- dependent process of decidualization and
suggests a paracrine or autocrine role for endothelins in the decidua.
相似文献