首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   15939篇
  免费   1001篇
  国内免费   235篇
耳鼻咽喉   383篇
儿科学   217篇
妇产科学   289篇
基础医学   2726篇
口腔科学   307篇
临床医学   1273篇
内科学   3152篇
皮肤病学   451篇
神经病学   1187篇
特种医学   1189篇
外科学   2090篇
综合类   82篇
现状与发展   3篇
一般理论   10篇
预防医学   617篇
眼科学   428篇
药学   1293篇
中国医学   153篇
肿瘤学   1325篇
  2024年   12篇
  2023年   133篇
  2022年   370篇
  2021年   662篇
  2020年   269篇
  2019年   441篇
  2018年   525篇
  2017年   409篇
  2016年   614篇
  2015年   882篇
  2014年   954篇
  2013年   1049篇
  2012年   1579篇
  2011年   1425篇
  2010年   842篇
  2009年   712篇
  2008年   899篇
  2007年   943篇
  2006年   772篇
  2005年   630篇
  2004年   518篇
  2003年   469篇
  2002年   382篇
  2001年   296篇
  2000年   245篇
  1999年   189篇
  1998年   97篇
  1997年   86篇
  1996年   61篇
  1995年   61篇
  1994年   44篇
  1993年   52篇
  1992年   55篇
  1991年   49篇
  1990年   46篇
  1989年   54篇
  1988年   47篇
  1987年   41篇
  1986年   31篇
  1985年   29篇
  1984年   14篇
  1983年   18篇
  1982年   13篇
  1981年   22篇
  1980年   14篇
  1979年   17篇
  1978年   17篇
  1977年   23篇
  1976年   19篇
  1975年   13篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
Yoon HJ  Kim H  Kim HL  Lee SG  Zheng SH  Shin JH  Lim CS  Kim S  Lee JS  Lee DS  Kim YS 《Clinical genetics》2002,62(2):128-134
In order to investigate the interdependent action of the insertion/deletion polymorphism of the angiotensin-converting enzyme (ACE) gene and polymorphism in exon 11 (C1136-->T; Ala379Val) of the platelet-activating factor acetylhydrolase (PAF-AH) gene, which encodes a functional antagonist of PAF, on the progression of immunoglobulin A (IgA) nephropathy, we analysed both polymorphisms in patients with primary IgA nephropathy, who were followed-up for longer than 3 years. During the follow-up (87.3 +/- 50.0 months), the disease progressed in 38 of the 191 patients (19.9%). The D allele of the ACE gene in the absence of the T allele of the PAF-AH gene did not affect the prognosis [odds ratio (OR), 3.6; 95% confidence interval (CI), 0.8-16.4] and neither did the T allele in the absence of the D allele (OR, 3.0; 95% CI, 0.4-24.2). However, the presence of both was a significant prognostic factor (OR, 6.6; 95% CI, 1.4-31.3). After adjusting for other risk factors, the presence of both proved to be an independent risk factor (OR, 4.5; 95% CI, 1.6-12.7). These results suggest that the interdependent effects of ACE and PAF-AH polymorphisms on the progression of IgA nephropathy might be more important than the effect of the individual polymorphisms.  相似文献   
42.
There is persuasive epidemiological and experimental evidence that dietary polyphenols have anti-inflammatory activity. Aspirin and other non-steroidal anti-inflammatory drugs (NSAIDs) have long been used to combat inflammation. Recently, cyclooxygenase (COX) inhibitors have been developed and recommended for treatment of rheumatoid arthritis (RA) and osteoarthritis (OA). However, two COX inhibitors have been withdrawn from the market due to unexpected side effects. Because conventional therapeutic and surgical approaches have not been able to fully control the incidence and outcome of many inflammatory diseases, there is an urgent need to find safer compounds and to develop mechanism-based approaches for the management of these diseases. Polyphenols are found in many dietary plant products, including fruits, vegetables, beverages, herbs, and spices. Several of these compounds have been found to inhibit the inflammation process as well as tumorigenesis in experimental animals; they can also exhibit potent biological properties. In addition, epidemiological studies have indicated that populations who consume foods rich in specific polyphenols have lower incidences of inflammatory disease. This paper provides an overview of the research approaches that can be used to unravel the biology and health effects of polyphenols. Polyphenols have diverse biological effects, however, this review will focus on some of the pivotal molecular targets that directly affect the inflammation process.  相似文献   
43.
X-linked severe combined immunodeficiency (X-SCID) is a rare, life-threatening immune disorder, caused by mutations in the gamma c chain gene, which encodes an essential component of the cytokine receptors for interleukin-2 (IL-2), IL-4, IL-7, IL-9, IL-15, and IL-21. A 13-month-old boy with recurrent infections who had reduced serum immunoglobulin levels and decreased numbers of CD3, CD16/56 cells was evaluated for gamma c chain gene mutation and protein expression. The patient had a C-to-T point mutation at nucleotide position 690, one of the hot spots, resulting in a single amino acid substitution of cysteine for arginine (R226C), as determined by direct sequencing and PCR-RFLP. The patient's mother was a heterozygous carrier. Percutaneous umbilical cord blood sampling was performed at the 6-month of gestation in a subsequent pregnancy. As the immunophenotype of the fetus showed an identical pattern, the pregnancy was terminated and genetic analysis of the abortus confirmed recurrence. This is the first report of the molecular diagnosis of X-SCID in Korea. Genetic analysis of the gamma c chain gene is useful for definite diagnosis and genetic counseling for X-SCID.  相似文献   
44.
Isometric and isokinetic torque curves at the knee joint   总被引:1,自引:0,他引:1  
Isometric and isokinetic torques of bilateral quadriceps and hamstrings were measured with Isokinetic Rehabilitation and Testing System (Model No. Cybex 340) on 40 normal untrained subjects, 20 males and 20 females, ranging between the ages of 23 and 35 years. The mean peak isometric and isokinetic torque values of both muscle groups showed no significant differences between dominant (right) and nondominant (left) limbs in both sexes; however there were significant differences between the male and the female. As the angular velocity increased, the peak torque significantly decreased, and the point of peak torque output occurred significantly later in the range of motion for quadriceps and hamstrings (p less than 0.01). There were no significant changes in the hamstrings to quadriceps (H/Q) ratios as the angular velocity increased. However, there were significant differences of mean H/Q ratio between male and female (p less than 0.01). Height had significant positive correlation with peak isometric and isokinetic torques for both quadriceps and hamstrings (p less than 0.01). Weight was found to correlate significantly with peak isometric and isokinetic torques (p less than 0.01). The mean isometric torques were significantly higher than the mean isokinetic torques for any joint angles in both sexes (p less than .01).  相似文献   
45.
H M Eun  Y S Bae  J W Yoon 《Virology》1988,163(2):369-373
The genes for the major capsid protein, VP1(1D), of both diabetogenic D variant (EMC-D) and nondiabetogenic B variant (EMC-B) of encephalomyocarditis virus were cloned by using two synthetic primers which are common to both EMC-D and EMC-B. The cloned genes were mapped for major restriction enzyme sites including AccI, BamHI, EcoRI, HincII, KpnI, PvuII, SstI, TaqI, and XbaI. Among those nine restriction enzyme sites, only the TaqI site distinguished EMC-D genome from the counterpart of EMC-B genome. The complete nucleotide sequences (831 bases) of the VP1 genes revealed five amino acid differences between the two variants. Three of the changes, at positions 41, 58, and 152, were Thr (EMC-B) to Ala (EMC-D). The additional two changes occurred at positions 63 [Gln (EMC-B) to Glu (EMC-D)] and 181 [Thr (EMC-B) to Ser (EMC-D)]. All of these amino acid changes were due to point mutations at the first base of each codon.  相似文献   
46.
Recent clinical trials showed that bortezomib, a novel proteasome inhibitor, had therapeutic activity in multiple myeloma. However, there was no data about the feasibility of bortezomib in Korean patients. We performed a pilot study of bortezomib in patients with relapsed or refractory myeloma (1.3 mg/m2 twice weekly for 2 week in a 3-week cycle). Seven patients were enrolled. The median age of patients was 59 yr. All patients previously received VAD (vincristine, doxorubicin and dexamethasone) and thalidomide chemotherapy. Three patients previously received alkylator-containing chemotherapy and 4 patients, autologous stem cell transplantation. Bortezomib monotherapy resulted in 3 partial remissions (43%), 3 no changes (43%) and 1 progressive disease (14%). One patient who had no response to bortezomib monotherapy experienced partial remission after addition of dexamethasone to bortezomib. The most common serious toxicity was thrombocytopenia (grade 3/4, 10 of 20 cycles (50%)) and grade 3 peripheral neuropathy was developed in 2 of 20 cycles (10%). Drug-related adverse event led to discontinuation of bortezomib in 1 patient. There was no treatment related mortality. Overall, bortezomib seems to be effective and feasible. Conduction of larger clinical studies on Korean patients is necessary to characterize clinical efficacy and safety of bortezomib more precisely.  相似文献   
47.
FVB and BALB/c mice show different morbidity, development of Clonorchis sinensis, and pathological changes following C. sinensis infection. FVB mice are susceptible and BALB/c mice are relatively more resistant to C. sinensis infection. To investigate the relationship between cytokine reaction and susceptibility to C. sinensis infection in FVB and BALB/c mice, we described both the patterns and kinetics of Th1 cytokines and Th2 cytokines in spleen cell culture. Interleukin (IL)-4 and IL-10 cytokine production in the culture supernatants of the concanavalin-A-stimulated spleen cells increased at 2–3 weeks post-infection in both strains. IL-5 production increased between 2 and 5 weeks post-infection in both strains, and reached a peak level at 2 weeks post-infection in BALB/c mice and 4 weeks post-infection in FVB mice. In contrast, gamma interferon (IFN-) production decreased between 2 and 4 weeks in both strains. IL-2 production increased slightly in BALB/c mice following infection, but was unchanged in FVB mice. IL-4 production over preinfection levels was significantly higher in FVB mice, whereas IFN-, IL-2, and IL-10 production were significantly higher in BALB/c mice. The levels of serum immunoglobulin E (IgE) and blood eosinophils in both mouse strains significantly increased between 3 and 6 weeks postinfection. Serum IgE levels were significantly higher in FVB mice than in BALB/c mice. The results of this study suggest that susceptibility to C. sinensis infection is associated with Th2 cytokine production, especially IL-4 which is predominant in relatively susceptible FVB mice.  相似文献   
48.
In order to determine the effect of ultraviolet radiation (UVR) on the cell adhesion molecules expressed in human dermal microvascular endothelial cells (HDMEC), the cells were exposed to varying UVR doses and the cell surface was examined for expression of intercellular cell adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM- 1), and E-selectin. The effect of UVB irradiation on the binding of T lymphocytes to HDMEC was also examined. UVA irradiation did not affect the surface expression of ICAM-1, VCAM-1, or E-selectin on the HDMEC. However, following UVB exposure, ELISA demonstrated a significant increase in the baseline ICAM-1 cell surface expression on the HDMEC. However, no induction of either E-selectin or VCAM-1 was noted. UVB also significantly augmented ICAM-1 induction by IL-1alpha and TNF-alpha. VCAM-1 was induced by stimulating HDMEC with IL-1alpha following a UVB irradiation dose of 100 mJ/cm2. Flow cytometric analysis of the HDMEC stimulated with IL-1alpha for 24h demonstrated that 12% of the cells expressed VCAM-1 but either IL-1alpha or UVB irradiation alone failed to induce VCAM-1 expression. Enhancement of T cell-HDMEC binding by IL-1alpha or TNF-alpha treatment was not significantly affected after UVB irradiation. This study demonstrated that UVB irradiation can alter ICAM-1 and VCAM-1 expression on the HDMEC surface and that augmentation of ICAM-1 expression and the IL-1alpha-dependent induction of VCAM-1 following UVB exposure might be important steps in the pathogenesis of sunburn.  相似文献   
49.
Ring-opening polymerization of a new anhydro ribose-type monomer, 1,4-anhydro-3-azido-3-deoxy-2-O-tert-butyldimethylsilyl-α-D -ribopyranose (A3ASR), was investigated. The monomer was synthesized from 1,4-anhyro-α-D -xylopyranose by three steps comprising Walden inversion at the C3 position into ribose configuration. Ring-opening polymerization of A3ASR by Lewis acid catalysts such as boron trifluoride etherate and stannic chloride gave a stereoregular 3-azido-3-deoxy-2-O-tert-butyldimethylsilyl-(1→5)-α-D -ribofuranan having specific rotations of +246 ~ +271 deg · dm?1 · g?1 · cm3 and number-average molecular weights of 18,7 × 103 ~ 25,1 × 103. When the polymerization was carried out by antimony pentachloride at 0°C, the resulting polymer exhibited a negative specific rotation of ?6 deg · dm?1 · g?1 · cm3 and the C1 absorption in the 13C NMR spectrum shifted downfield to 107,5 ppm, suggesting that the polymer might consist of 1,5-β furanosidic unit. The reduction of the azido group of the 1,5-α and 1,5-β furanosidic polymers into amino group and subsequent desilylation gave 3-amino-3-deoxy-(1→5)-α- and -β-D -ribofuranans, respectively. In addition, copolymerization of A3ASR with 1,4-anhydro-2,3-di-O-tert-butyldimethylsilyl-α-D -ribopyranose (ADSR) in various feeds was performed by boron trifluoride etherate as catalyst to give copolymers with different monomeric components. The structural analysis of the homopolymers and copolymers was examined by means of 1H and 13C NMR spectroscopies, IR spectroscopy, and optical rotation.  相似文献   
50.
Malignant transformation of mature cystic teratoma of the ovary can develop with an incidence of 1-2%. Squamous cell carcinoma is the most common malignant tumor arising in benign cystic teratoma. The authors have recently experienced a case of combined microcystic adnexal carcinoma and squamous cell carcinoma arising in a benign cystic teratoma of the ovary in a 72-year-old Korean woman. The right ovarian cystic mass had been ruptured and firmly adhered with salpinx and omental fat tissue on operation. Thickened cystic wall with yellowish white solid infiltrative lesion was noted grossly, and two different malignant tumors of microcystic adnexal carcinoma exhibiting both eccrine and hair follicular differentiation and squamous cell carcinoma were observed microscopically. PAS and CEA positivities suggested eccrine differentiation in areas of microcystic adnexal carcinoma.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号