全文获取类型
收费全文 | 4164篇 |
免费 | 254篇 |
国内免费 | 7篇 |
专业分类
耳鼻咽喉 | 14篇 |
儿科学 | 130篇 |
妇产科学 | 42篇 |
基础医学 | 532篇 |
口腔科学 | 87篇 |
临床医学 | 294篇 |
内科学 | 1051篇 |
皮肤病学 | 72篇 |
神经病学 | 405篇 |
特种医学 | 127篇 |
外科学 | 621篇 |
综合类 | 33篇 |
预防医学 | 139篇 |
眼科学 | 44篇 |
药学 | 340篇 |
肿瘤学 | 494篇 |
出版年
2023年 | 16篇 |
2022年 | 45篇 |
2021年 | 68篇 |
2020年 | 35篇 |
2019年 | 49篇 |
2018年 | 58篇 |
2017年 | 47篇 |
2016年 | 54篇 |
2015年 | 53篇 |
2014年 | 52篇 |
2013年 | 87篇 |
2012年 | 141篇 |
2011年 | 191篇 |
2010年 | 94篇 |
2009年 | 80篇 |
2008年 | 163篇 |
2007年 | 152篇 |
2006年 | 172篇 |
2005年 | 184篇 |
2004年 | 190篇 |
2003年 | 174篇 |
2002年 | 189篇 |
2001年 | 151篇 |
2000年 | 152篇 |
1999年 | 165篇 |
1998年 | 66篇 |
1997年 | 50篇 |
1996年 | 37篇 |
1995年 | 40篇 |
1994年 | 23篇 |
1993年 | 32篇 |
1992年 | 130篇 |
1991年 | 130篇 |
1990年 | 135篇 |
1989年 | 141篇 |
1988年 | 152篇 |
1987年 | 96篇 |
1986年 | 88篇 |
1985年 | 80篇 |
1984年 | 74篇 |
1983年 | 42篇 |
1979年 | 59篇 |
1978年 | 27篇 |
1977年 | 36篇 |
1976年 | 22篇 |
1975年 | 20篇 |
1974年 | 17篇 |
1973年 | 21篇 |
1972年 | 20篇 |
1971年 | 19篇 |
排序方式: 共有4425条查询结果,搜索用时 15 毫秒
91.
OBJECTIVE: To investigate the effect of sodium, protein and calcium in habitual diets on bone resorption. DESIGN: A cross-sectional study. SETTING: A community-based study. SUBJECTS: Healthy free-living male (n=342) and female (n=421) volunteers aged 20-79 y recruited for a health and nutrition examination survey conducted by a local government. METHODS: Bone resorption was assessed by the measurement of free deoxypyridinoline in 24 h urine. Dietary assessment was by one-day dietary record method. Sodium and urea in 24 h urine were also measured for assessment of sodium and protein intake. The relationships between deoxypyridinoline excretion and the dietary factors were examined using correlation and multiple regression statistics. RESULTS: In women aged 50-79 y, protein intake was positively associated with deoxypyridinoline excretion (P<0.05); and the urinary deoxypyridinoline/creatinine ratio was positively associated with both the urinary calcium/creatinine ratio (P<0.01) and sodium/creatinine ratio (P<0.05). In the multiple regression model, the association of the deoxypyridinoline/creatinine ratio and sodium/creatinine ratio was still significant (P<0.05) after adjustment for possible confounders, in this sex and age group. CONCLUSION: In elderly women, habitual excess sodium in diets may result in bone loss through accelerated bone resorption. 相似文献
92.
Yokota K Johyama Y Yamaguchi K Fujikt Y Takeshita T Morimoto K 《Environmental health and preventive medicine》1996,1(3):133-135
Methylterahydrophthalic anhydride (MTHPA) is used as a hardening agent in an epoxy resin system. Because work-related nasal symptoms were observed in some workers exposed toMTHPA at two condenser plants, a cross-sectional survey was performed to improve their work environment. MeanMTHPA levels in the manufacturing processes to which the workers were routinely assigned were extremely low (1.09-22.4 μg/m3). However, specific IgE antibody (S-IgE) was detected in 9 (32%) of 28 workers. Of these, 8 (89%) had nasal symptoms. An IgE-mediated mechanism seems to be associated with at least some of the cases of work-related nasal symptoms. This indicates that the occupational health administration ofMTHPA cannot be controlled simply by limiting exposure in the work environment. Total IgE (T-IgE) levels were significantly higher in S-IgE-positive workers than in S-IgE-negative workers (geometric mean, 200.5 and 51.3 IU/ml, respectively; p<0.002, unpaired t test). These findings demonstrate that workers in whom S-IgE is less likely to be produced, i.e., those in whom the T-IgE level is 80 IU/ml or less, should be assigned to work in these manufacturing processes. 相似文献
93.
94.
Spontaneous improvement in reduced vasodilatory capacity in major cerebral arterial occlusive disease 总被引:4,自引:1,他引:3
Reduced vasodilatory capacity resulting from occlusive lesions of the major cerebral arteries may return to normal without
surgical revascularisation. We aimed to determine prospectively the frequency and predictors of recovery of impaired haemodynamics
as demonstrated by acetazolamide (ACZ) reactivity on single-photon emission computed tomography (SPECT). Vasoreactivity was
measured by 123I-IMP SPECT with an ACZ challenge, in 37 medically treated patients with unilateral occlusive disease of the internal carotid
or middle cerebral artery at an interval of 1–2 years. Each ACZ challenge test was analysed semiquantitatively by calculating
the degree of increase in cerebral blood flow (CBF) asymmetry after ACZ administration (ΔAI). Vasodilatory capacity was abnormal
initially in 20 patients (65 %); eight of whom (40 %) exhibited spontaneous normalisation on follow-up. Although the baseline
characteristics did not differ significantly between patients with or without increase in reactivity, logistic regression
analysis revealed that the initial ΔAI (P < 0.05) and the type of vascular lesion (stenosis or occlusion) (P < 0.05) correlated significantly with a return towards normal of reduced ACZ reactivity. Spontaneous improvement of impaired
vasodilatory capacity may not be a rare phenomenon. We found that mild reduction in the initial ACZ reactivity and a stenosis,
but not complete occlusion, were independent factors contributing to normalisation of impaired cerebral haemodynamics.
Received: 12 October 1998/Accepted: 27 April 1999 相似文献
95.
Kawanishi M; Kohno T; Otsuka T; Adachi J; Sone S; Noguchi M; Hirohashi S; Yokota J 《Carcinogenesis》1997,18(11):2057-2062
Allelotype and replication error (RER) phenotype analyses were performed to
clarify the pathogenetic significance of inactivation of tumor suppressor
genes and genomic instability in the genesis and progression of small cell
lung carcinoma (SCLC). We examined 37 cases of SCLC for loss of
heterozygosity (LOH) and microsatellite instability at 49 loci on all 39
nonacrocentric chromosomal arms. LOH was frequently (>70%) detected on
chromosomes 3p (29/32, 90.6%), 5q (15/21, 71.4%), 13q (25/26, 96.2%), 17p
(22/25, 88.0%), and 22q (24/33, 72.7%). Frequent LOH (>70%) on these
loci was observed even among seven cases of stage I tumors. The incidence
of LOH on all 39 nonacrocentric chromosomal arms was not significantly
different between primary tumors and metastases. These results suggest that
inactivation of multiple tumor suppressor genes accumulates relatively
early during progression of SCLC and it may be responsible for clinically
and biologically aggressive phenotype of SCLC. RER was observed in 6/37
(16.2%) of SCLC, however, RER at multiple loci was observed only in two
cases. Therefore, it was indicated that genomic instability is uncommon,
but might play a role in the genesis of a small subset of SCLC.
相似文献
96.
CD44 is a cell surface glycoprotein with a number of isoforms generated by alternative splicing of ten 'variant' exons in humans. Variant exon 6-containing isoforms of CD44 (CD44v6) have been implicated in the metastatic potential of rat carcinoma cell lines. Human homologues of CD44v6 are expressed in several tumour types and are involved in their progression. In the present study, we examined the expression of CD44 mRNA in 20 acute myelocytic leukemias by semiquantitative RT-PCR analysis and assessed its prognostic value. In all leukemic cells the predominant isoform was the 'standard' form of CD44 (CD44H), and intense bands were found in eight cases. CD44v6 was expressed in 11 cases, although its levels and those of other variants containing exon v7 through to v10 were much lower than those of CD44H. Isoforms containing exon v4 or v5 could not be detected. The expression of CD44v6 correlated with the death rate from leukemia (p > 0.05), but was not related to other risk factors. On the other hand, the intense expression of CD44H did not correlate with the prognosis of leukemia. CD44v6 thus appears to be a marker for the poor prognosis of acute myelocytic leukemia. 相似文献
97.
RER phenotype and its associated mutations in familial gastric cancer 总被引:11,自引:1,他引:11
To clarify the genetic background of gastric cancer, we collected 28
familial gastric cancers (FGCs) with reference to the Amsterdam criteria in
hereditary non-polyposis colorectal cancer (HNPCC) and investigated the
frequency of replication error (RER) at six microsatellite loci and
frameshift mutations in its related genes in these tumors. RER was detected
in seven (25%) of the 28 gastric cancers. Five (18%) cases showed RER at
more than two loci. The apparent increased incidence of RER in FGC was not
detected compared with that reported in sporadic gastric cancers
previously. Among four cases with RER at more than three loci, frameshift
mutations in the (A)8 track of the hMSH3 gene were detected in all the four
cases and mutations in the (A)10 track of the transforming growth
factor-beta type II receptor (TGF-beta RII) gene were detected in the three
of them. Histologically, three of the four cases were of the intestinal
type, and the other one was the diffuse type. No mutation was detected in
the (C)8 and (GT)3 tracks of the hMSH6 and TGF-beta RII genes respectively.
These results indicate that the acquisition of the RER phenotype equally
influences the gastric carcinogenesis of both sporadic and familial cases,
and that the majority of FGC is pathogenetically distinct from HNPCC.
相似文献
98.
Infrequent Mutations of the hOGG1 Gene, That Is Involved in the Excision of 8-Hydroxyguanine in Damaged DNA, in Human Gastric Cancer 总被引:4,自引:0,他引:4
Kazuya Shinmura Takashi Kohno Hiroshi Kasai Kenji Koda Haruhiko Sugimura Jun Yokota 《Cancer science》1998,89(8):825-828
DNA glycosylase, encoded by the hOGG1 gene, repairs 8-hydroxyguanine (oh8 Gua), which is an oxidatively damaged mutagenic base. To clarify whether the DNA repair activity of hOGG1 protein is involved in gastric carcinogenesis, we examined 9 gastric cancer cell lines and 35 primary gastric cancers for mutations and genetic polymorphisms of the hOGG1 gene by polymerase chain reaction-single strand conformation polymorphism analysis. A G-to-A transition was detected in a gastric cancer cell line, MKN1. This nucleotide change caused the conversion of the amino acid from Arg to His at codon 154, which is located in a domain highly conserved among human, mouse, and yeast OGG1 proteins. No mutation was detected in primary gastric cancers. We compared the distribution of the polymorphic alleles associated with enzymatic activity (hOGG1-Ser326 vs. hOGG1-Cys326 ) between 35 gastric cancer patients and 42 healthy individuals. Although the frequency of the Cys326 allele, associated with low enzymatic activity, in gastric cancer patients was a little higher than that in healthy individuals, the difference did not reach statistical significance. These results suggest that low hOGG1 activity due to mutations and genetic polymorphisms is involved in the development of only a small subset of gastric cancers. 相似文献
99.
Monosynaptic and disynaptic projections from the substantia nigra pars reticulata to the parafascicular thalamic nucleus in the rat 总被引:1,自引:0,他引:1
We examined a direct pathway and an indirect pathway via the reticular thalamic nucleus (RT) from the substantia nigra pars reticulata (SNr) to the parafascicular thalamic nucleus (PF) by using anterograde and retrograde tract tracing methods. After biotinylated dextranamine (BDA) injection into the dorsolateral part of the SNr, many labeled fibers and axon terminals were distributed in the ventral part of the RT, as well as in the ventrolateral part of the PF, bilaterally with an ipsilateral dominance. After BDA injection into the ventral part of the RT, a plexus of labeled axons was found bilaterally with an ipsilateral dominance in the ventrolateral part of the PF. After combined injections of BDA into the dorsolateral part of the SNr and cholera toxin B subunit (CTb) into the ventrolateral part of the PF on the same side, overlapping distribution of BDA-labeled fibers and CTb-labeled neurons was observed in the ventral part of the RT ipsilateral to the injection sites, where the BDA-labeled axon terminals made symmetrical synaptic contacts with soma and dendrites of the CTb-labeled neurons. 相似文献
100.
Takaiwa M Nakano M Koseki K Yoshida J Iwasaki M Kuma Y Kushida N Kamata T Yokota T Yamaguchi O 《Nihon Hinyōkika Gakkai zasshi. The japanese journal of urology》2000,91(7-8):595-598
75 year old female who was hospitalized for abdominal pain and fever up on 12th May 1998. She had been followed as a polycystic kidney patient since few years. The swelling of the right kidney and her general condition became gradually worse. On 18th May, the embolization to the right kidney using pure alcohol and gelatin sponge was performed. Within a month, CT scan showed the reduced volume of the right kidney and her blood examination data as well as her general condition became gradually well. And on 17th June, she left our hospital without any complication. 相似文献