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   5081篇
  免费   479篇
  国内免费   27篇
耳鼻咽喉   64篇
儿科学   176篇
妇产科学   94篇
基础医学   573篇
口腔科学   79篇
临床医学   556篇
内科学   836篇
皮肤病学   38篇
神经病学   471篇
特种医学   227篇
外科学   810篇
综合类   122篇
一般理论   6篇
预防医学   747篇
眼科学   107篇
药学   349篇
中国医学   10篇
肿瘤学   322篇
  2022年   34篇
  2021年   79篇
  2020年   47篇
  2019年   73篇
  2018年   88篇
  2017年   80篇
  2016年   80篇
  2015年   88篇
  2014年   141篇
  2013年   172篇
  2012年   288篇
  2011年   290篇
  2010年   177篇
  2009年   152篇
  2008年   218篇
  2007年   275篇
  2006年   293篇
  2005年   250篇
  2004年   217篇
  2003年   187篇
  2002年   179篇
  2001年   129篇
  2000年   133篇
  1999年   87篇
  1998年   75篇
  1997年   61篇
  1996年   47篇
  1995年   34篇
  1994年   52篇
  1993年   43篇
  1992年   116篇
  1991年   88篇
  1990年   93篇
  1989年   98篇
  1988年   97篇
  1987年   79篇
  1986年   70篇
  1985年   68篇
  1984年   71篇
  1983年   46篇
  1982年   36篇
  1981年   36篇
  1980年   36篇
  1979年   53篇
  1977年   42篇
  1976年   35篇
  1974年   32篇
  1972年   36篇
  1969年   32篇
  1966年   31篇
排序方式: 共有5587条查询结果,搜索用时 234 毫秒
51.
Macropotrema pertinax gen. et sp. nov. (Digenea: Paramphistomidae) is described from the caecum of the macropodid marsupial Macropus agilis (Gould, 1842) from northern Australia. The new genus is characterised as follows: ventro-terminal acetabulum bearing many papillae; oral sucker with constriction and paired diverticula; oesophagus with muscular bulb; cirrus sac and genital sucker absent; testes symmetrical, unlobed, preovarian; Laurer's canal opening anterior to excretory pore. The genus is placed in the subfamily Pseudodiscinae N?smark, 1937. At the point where the worm attaches to the caecal wall of the host, the entire mucosa is destroyed and there is an inflammatory cell infiltration in the intact mucosa surrounding the attachment site.  相似文献   
52.
Large-scale functional genomics studies for malaria vaccine and drug development will depend on the generation of molecular tools to study protein expression. We examined the feasibility of a high-throughput cloning approach using the Gateway system to create a large set of expression clones encoding Plasmodium falciparum single-exon genes. Master clones and their ORFs were transferred en masse to multiple expression vectors. Target genes (n = 303) were selected using specific sets of criteria, including stage expression and secondary structure. Upon screening four colonies per capture reaction, we achieved 84% cloning efficiency. The genes were subcloned in parallel into three expression vectors: a DNA vaccine vector and two protein expression vectors. These transfers yielded a 100% success rate without any observed recombination based on single colony screening. The functional expression of 95 genes was evaluated in mice with DNA vaccine constructs to generate antibody against various stages of the parasite. From these, 19 induced antibody titers against the erythrocytic stages and three against sporozoite stages. We have overcome the potential limitation of producing large P. falciparum clone sets in multiple expression vectors. This approach represents a powerful technique for the production of molecular reagents for genome-wide functional analysis of the P. falciparum genome and will provide for a resource for the malaria resource community distributed through public repositories.  相似文献   
53.
54.
The purpose of the study was to examine the stability of variables associated with the metabolic syndrome from adolescence to adulthood. The sample included 48 subjects from the Aerobics Center Longitudinal Study who had one clinical visit during adolescence (mean age = 15.8 years) and a follow-up visit during adulthood (mean age = 26.6 years). The following variables were considered: treadmill time to exhaustion (TM), body mass index (BMI), waist circumference (WC), percent body fat (%BF), total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C), TC:HDL-C, triglycerides (TG), glucose (GLU), and systolic (SBP), diastolic (DBP), and mean (MAP) blood pressure. A composite risk factor score using variables consistent with the WHO and ATP III definition of the metabolic syndrome (WC, HDL-C, TG, MAP, and GLU) was calculated. Tracking coefficients were computed as partial correlations, controlling for length of follow-up (mean = 11 years). Tracking coefficients (r values) were moderate for all variables (TM, 0.53; BMI, 0.64; WC; 0.79;%BF, 0.44; TC, 0.62; HDL-C, 0.60; TG, 0.54; TC:HDL-C, 0.78; SBP, 0.45; and MAP, 0.41), except GLU (0.26) and DBP (0.21). The composite risk factor score also tracked moderately well (0.56) from adolescence into adulthood. The results support previous findings that variables associated with the metabolic syndrome track moderately well from adolescence to adulthood. The findings support the prevention and treatment of obesity, atherosclerosis, type 2 diabetes, and the metabolic syndrome during childhood and adolescence.  相似文献   
55.
Although trophozoites of Giardia lamblia have not been demonstrated to possess the capacity for synthesis of phospholipids, these protozoan parasites would be exposed to fatty acids within the human small intestine. We have evaluated the metabolic incorporation of arachidonic and palmitic acids by Giardia trophozoites. Trophozoites (2.25 X 10(6)) were incubated with 12 nM [3H]fatty acid for up to 60 min. Uptake of [3H]arachidonate by trophozoites was rapid, increasing from 37% at 1 min to 65% at 10 min. Uptake of palmitate was rapid but less extensive. In contrast to palmitate, almost all of the trophozoite-associated [3H]arachidonate was esterified into phospholipids and neutral lipids. By 1 and 60 min 37% and 82% of [3H]arachidonate, respectively, were incorporated into phospholipids, including phosphatidylinositol and phosphatidylcholine. Peak incorporation of [3H]arachidonate into phosphatidylcholine (30 mmol [3H]fatty acid (mol phospholipid)-1) occurred at 60 min; whereas incorporation into the pool of phosphatidylinositol, which accounted for only 4% of trophozoite phospholipid, was maximal at 10 min (190 mmol [3H]fatty acid (mol phospholipid)-1) and declined significantly thereafter as arachidonic acid was released from phosphatidylinositol. Therefore, Giardia trophozoites not only utilize exogenous fatty acids in the formation of glycerolipids but also preferentially incorporate arachidonic acid into a metabolically active pool of phosphatidylinositol.  相似文献   
56.
Anatomy of the thenar branch of the median nerve   总被引:1,自引:0,他引:1  
The gross and interfascicular anatomy of the terminal portion of the thenar (or recurrent median) nerve was defined by a microdissection of 20 fresh-frozen cadaveric hands. The traditionally described pattern of one main thenar trunk with three terminal branches, one each to the abductor pollicis brevis, opponens pollicis, and flexor pollicis brevis muscles, was observed in nine specimens (45%). One main trunk with two terminal branches (one branch to the abductor and one to the opponens, but no branch to the flexor) was seen in six specimens (30%). The remaining five specimens (25%) exhibited four other terminal patterns with either two, three, or four branches off the main trunk. In 15 specimens (75%), a previously undescribed "accessory thenar nerve" (ATN) arose from either the first common digital nerve (25%) or the radial proper digital nerve to the thumb (50%). The ATN innervated the flexor pollicis brevis.  相似文献   
57.
Maternal and Child Health Journal - In the US, approximately 8% of pregnant women smoke, and 5–11.9% currently use ENDS products. The health effects of ENDS use are debated; however, most...  相似文献   
58.
Prevention Science - Intimate partner violence (IPV) impacts sexual minority adolescents at rates equal to or greater than the rate it impacts heterosexual adolescents. We investigated whether...  相似文献   
59.
BackgroundThe prevalence of total joint arthroplasty (TJA) in the United States has drawn the attention of health care stakeholders. The payers have also used a variety of strategies to regulate the medical necessity of these procedures. The purpose of this study was to examine the level of evidence of the coverage policies being used by commercial payers in the United States.MethodsThe references of the coverage policies of four commercial insurance companies were reviewed for type of document, level of evidence, applicability to a TJA population, and success of nonoperative treatment in patients with severe degenerative joint disease.Results282 documents were reviewed. 45.8% were primary journal articles, 14.2% were level I or II, 41.2% were applicable to patients who were candidates for TJA, and 9.9% discussed the success of nonoperative treatment in patients who would be candidates for TJA.ConclusionMost of the references cited by commercial payers are of a lower level of scientific evidence and not applicable to patients considered to be candidates for TJA. This is relatively uniform across the reviewed payers. The dearth of high-quality literature cited by commercial payers reflects the lack of evidence and difficulty in conducting high level studies on the outcomes of nonoperative versus operative treatment for patients with severe, symptomatic osteoarthritis. Patients, surgeons, and payers would all benefit from such studies and we encourage professional societies to strive toward that end through multicenter collaboration.  相似文献   
60.
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